Environmental Health

Environmental health is a two-way street. Our environment, in the largest sense, is the complex network of physical, chemical, biological, and ecological components that make up the natural world. How clean and unpolluted the air, water, and soil of this environment are can affect the health of human beings. On the other hand, the way people treat the environment in their professional, industrial, and recreational activities helps determine how clean and safe it will be. In short, the environment affects the health of human beings, and human beings affect the health of the environment. All of the issues that evolve out of the interaction between people and the environment fall under the umbrella of environmental health.

Governments, companies, and individuals have a responsibility to preserve and promote environmental health. Government agencies, like the Environmental Protection Agency (EPA), founded in 1970, regulate industry to limit pollution that can damage the environment. The EPA's mission is to protect public health and the quality of the natural environment. Legislation like the Clean Air Act, passed by Congress in 1970, protects air quality by setting standards of purity for the air circulated in homes, schools, and workplaces. Groups outside the government, such as the World Wildlife Foundation, also work to identify and control threats to the environment that will endanger the food, water, and homes of plants and animals.

Everyone must make choices about how and where to live. Whether people are watching television in their living rooms, working at an office, eating at a restaurant, swimming at a beach, bicycling in a park, or sitting in a classroom, they should be aware of the condition of the environment around them. Good environmental health means having a safe, clean environment so that everyone can be healthy and productive within it. This chapter discusses the many different risks that threaten the environment, including radiation, pesticides, and indoor and outdoor air pollution, as well as ways to protect the environment and those who live in it.

RADIATION

Radiation is energy, or emission of energy, in the form of waves or particles. Microscopic particles, called atoms, are the foundation on which all matter (all substances that exist as solids, liquids, or gas) is built. Each atom has a nucleus at its center. The nucleus contains smaller (nuclear) particles called protons and neutrons. If the number, position, or energy level of these nuclear particles changes, an atom becomes unstable, or radioactive. Unstable atoms, or atoms undergoing change, produce radiation.

Sources of Radiation

Radiation is everywhere. It occurs naturally in soil and water on Earth. It exists in outer space and inside human bodies. Since the natural sources exist everywhere, these sources are sometimes called background radiation. There are human-made sources of radiation, too. Radiation has been harnessed for use in science, medicine, and industry. X-ray technology, nuclear power plants, and some forms of electricity use radiation. According to the United States Environmental Protection Agency (EPA), 80 percent of radiation sources are natural and 20 percent are synthetic (human-made).

Radiation: Words to Know

Acid rain:

Rain with a high content of sulfuric acid.

Asbestos:

A mineral fiber.

Byproduct:

Something other than the main product that is produced in a chemical or biological process.

Carbon monoxide:

A colorless, odorless, tasteless gas that turns into carbon dioxide when it is burned.

Carcinogenic:

Cancer-causing.

Contaminate:

To infect something or make something unsafe for use.

Cosmic:

Relating to the universe in contrast to Earth.

Emission:

Substances released into the air.

Endocrine disrupter:

Manmade chemical that looks and acts like naturally-occurring hormones.

Environmental tobacco smoke (ETS):

The mixture of the smoke from a lit cigarette, pipe, or cigar and the smoke exhaled by the person smoking; also known as secondhand smoke.

Herbicide:

A chemical agent used to kill damaging plants, such as weeds.

Incinerator:

A machine that burns waste materials.

Industrial:

Relating to a company that manufactures a product.

Inert:

A chemical agent lacking in active properties.

Leaching:

The process of dissolving outward by the action of a permeable substance.

Lead:

A heavy, flexible, metallic element that is often used in pipes and batteries.

Microscopic:

Invisible without the use of a microscope, an instrument that enlarges images of tiny objects.

Nitrogen dioxide:

A gas that cannot be seen or smelled. It irritates the eyes, ears, nose, and throat.

Ozone layer:

The atmospheric shield that protects the planet from harmful ultraviolet radiation.

Particle:

A miniscule pollutant released when fuel does not burn completely.

Pesticide:

A chemical agent used to kill bugs.

Potassium:

A chemical element that is a silver-white, soft metal occurring in nature.

Radiation:

Energy or rays emitted when certain changes occur in the atoms or molecules of an object or substance.

Radon:

A colorless, odorless, radioactive gas produced by the naturally occurring breakdown of the chemical element uranium in soil or rocks.

Sulfur dioxide:

A toxic gas that can also be converted to a colorless liquid.

Synthetic:

Something that is man-made; not found in nature

Thyroid:

A gland that controls the growth of the body

Toxic:

Relating to or caused by a poison

Uranium:

A chemical element that is a silver-white, hard metal and is radioactive.

Volatile organic compound (VOC):

An airborne chemical that contains carbon.

Types of Radiation: Non-ionizing and Ionizing Radiation

Two major types of radiation are non-ionizing radiation and ionizing radiation. Non-ionizing radiation is the less potent (strong) form. It has the power to move atoms around, but not to chemically change (or ionize) them. Ionizing radiation, on the other hand, does have the power to chemically change atoms and it is this power that makes it a threat to humans and the environment. There are three major types of ionizing radiation. They are called alpha, beta, and gamma rays. (They can also be described as radioactive particles, or radiation.) Each of these sub-groups is distinguished from the others by the ease or difficulty with which it can penetrate (or enter) the human body.

ALPHA RADIATION. The ability of an alpha particle to enter the body can be blocked by paper or skin, but alpha particles can enter the body through an open wound and do harm. Airborne alpha particles that are inhaled can cause serious lung damage.

BETA RADIATION. Paper cannot block beta radiation from entering the body. Some beta particles would be deterred by skin, while still more powerful beta particles would require something the thickness of wood to prevent entry. If beta rays do find their way into the body, they can get into the bones and cause damage.

COMMON SOURCES OF RADIATION TO WHICH PEOPLE CAN BE EXPOSED

• computer terminal
• cosmic rays from outer space
• ingested food and water containing elements like potassium
• medical X ray
• radiation in cancer treatment
• radon gas (in the air)
• rocks and soil
• smoke detector
• television
• X-ray luggage inspection machine

GAMMA RADIATION. Gamma rays are the most powerful particles. Often appearing along with alpha and beta rays, these dangerous rays can break through paper, skin, and wood. A concrete wall would be needed to deflect gamma rays. If gamma rays penetrate the body, they can cause major damage to internal organs.

Radiation Risks

Most scientists agree that radiation can be carcinogenic (cancer-causing); indeed, the major health risk radiation poses is an increased risk of developing cancer. Other harmful effects that have been observed include genetic abnormalities in the children of parents who had significant exposure to radiation. Mental retardation, in particular, has been observed in children whose mother was exposed to a significant amount of radiation.

EXPOSURE TO RADIATION, OR THE DOSE (AMOUNT) OF EXPOSURE, IS MEASURED BY A UNIT CALLED A REM. THE UNIT OF MEASURE FOR SMALLER DOSES IS THE MILLIREM. A REM IS EQUAL TO 1,000 MILLIREMS. ACCORDING TO EPA SCIENTISTS, AN AVERAGE U.S. CITIZEN'S ANNUAL RADIATION EXPOSURE IS ABOUT 360 MILLIREMS PER YEAR.

RADON AND ITS THREAT TO HUMAN LIFE

While cosmic rays represent some 8 percent of human exposure to natural radiation, EPA scientists suggest that radon accounts for an over-whelming 55 percent of human exposure to natural sources of radiation.

Produced by the decay of radioactive uranium (a chemical element) widely found in soils around the planet, radon gas has no color, taste, or odor. Radon travels up from the ground to seep into the foundation of a school, home, or other building. Once inside a building, airborne radon can become a threat to human health. If unhealthy amounts of radon are inhaled, it can damage the lungs and cause lung cancer. Scientists believe radon is second only to smoking as a cause of lung cancer, with thousands of lung cancer deaths in America each year thought to be the result of radon exposure.

Exposure to radioactive elements in the ground, such as thorium and potassium, can vary depending on where a person lives since the composition of land varies in different places. Exposure from cosmic radiation that is discharged into the atmosphere from outer space can also vary by location. Places that are at a higher elevation have thinner atmospheres and less protection from cosmic radiation. Locations that are closer to sea level have a bigger buffer zone and are less susceptible to cosmic radiation.

The Food and Drug Administration (FDA) and EPA insure that strict guidelines are followed for medical procedures involving radiation. The personnel, equipment, and facilities involved all have to meet certain standards to insure that radiation is managed as safely as possible. The Nuclear Regulatory Committee (NRC) has made tougher rules to govern construction, maintenance, emissions, and operations of nuclear power plants to decrease the risk of dangerous nuclear accidents. Stronger rules have also been developed for disposal of the radioactive waste, which is the byproduct of medical, scientific, and industrial uses of radiation.

What to Do About Radiation Exposure

Even with federal agencies monitoring radiation risks and working to control dangerous exposure to human populations and the environment, people still can't avoid radiation altogether. But precautions can be taken to limit exposure. When doctors recommend getting an X ray, people should not be afraid to take a few moments to talk about the risks versus benefits. Also, people in any community should be encouraged to get homes or schools tested to find out if the radon levels are acceptable.

There are three key strategies to limiting radiation exposure:

1. Time spent near an identified source of radiation should be limited.
2. Distance from an identified source of radiation should be kept; more distance means less exposure.
3. Identified sources of radiation should be shielded, keeping them out of or away from the body where they can do damage; for example, cracks in pipes and foundations should be repaired to block radon from getting into the air of homes.

FEDERAL AGENCIES WORKING TO LIMIT RADIATION EXPOSURE

Environmental Protection Agency (EPA)

Nuclear Regulatory Committee (NRC)

Department of Health and Human Services (HHS)

Department of Energy (DOE)

Department of Defense (DOD)

Department of Transportation (DOT)

Occupational Safety and Health Administration (OSHA)

Concerns about radiation in one's environment can be addressed by writing to state legislators to find out what is being done to correct or prevent a problem. Individuals can stay up to date on environmental issues so as to know what the latest studies say about sources of radiation in the everyday environment, such as computers and television. More information helps to make smarter choices about what to do, or not do, to limit exposure to dangerous sources or levels of radiation.

PESTICIDES

Human beings rely on a wide range of plants and animals for food. The majority of what people eat is grown or raised on the land, or from the waters, around the Earth. Plants or animals that interfere with or destroy human agricultural or livestock efforts are called pests. Animals, particularly insects and rodents, that can cause damage to human homes, lawns, food, and sanitation are also called pests. Pesticides are the products, usually chemically based, that are used to fight or kill these pests.

Common Types of Pesticides

Pesticides are used in agriculture on a large scale. Powerful chemical agents that deter a harmful weed or pest might be sprayed over large areas

of crops. On a smaller scale, individuals use pesticides to protect their homes and yards. Pesticide products can be bought in many forms including sprays, liquids, sticks, powders, crystals, balls, and foggers. Products that are commonly used to control pests around the house include insecticides (insects), termiticides (termites), rodenticides (rodents), fungicides (fungi, such as mold), and disinfectants (germs that can cause disease).

Pros and Cons of Pesticide Use

The use of pesticides is surrounded by controversy. Pesticides serve an invaluable function in protecting the crops and livestock that are vital to people's food supply. Pesticides can also help defend people's homes against germs and unsanitary and destructive pests. On the other hand, some pesticides contain and spread chemicals, which are toxic (poisonous), or even fatal, if they are consumed by human beings.

Each pesticide contains an active chemical ingredient that is targeted to kill a specific plant or animal pest. But these ingredients are surrounded, or carried, by chemical agents referred to as inerts. They are called inert (meaning lacking in active properties) because they do not have an active effect on the targeted pest. The problem is that inerts can be toxic to other animals or plants with which they come into contact. Some of these inerts are so toxic that, to insure public safety, the recommended usage of the pesticide is limited to mere ounces per acre of land.

Pesticide Risks in Agriculture

Although pesticides are a relatively cost-effective way to protect crops and livestock from damage or destruction, the potential health risks (and the costs that might be generated by them) also need to be considered. Aerial (air) or ground applications of pesticides are hard to control because herbicides (chemical agents used on damaging plants, such as weeds) can drift onto unintended areas.

CONTROLLING PESTICIDE USE

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was passed in 1947 to establish more controls over pesticide use. In 1972, the Federal Environmental Pest Control amendment further expanded standards for products and procedures used in pest management. This amendment introduced the following controls:

• It is illegal to use pesticides in an amount or manner other than what is specified on the product label.
• There will be heavy fines and/or imprisonment for improper pesticide use.
• There must be a distinction between general-use and restricted-use pesticides.
• State certification is required for restricteduse pesticides.
• Environmental Protection Agency (EPA) is required to investigate pesticide manufacturing plants.
• Registration is required of all pesticides by the EPA.
• Scientific research is required to confirm a product's effectiveness on killing targeted pests and to confirm no risks to people, other plants, and other animals (assuming the product is used as directed).

Methods used to try to control this drift include applying pesticides closer to the ground; waiting for wind to be at a minimum when spraying; using spray nozzles that tightly focus the outgoing stream of pesticides; and adding thickeners to pesticides to help focus active ingredients toward the intended targets. Pesticide users also have to be careful to remove contamination from the sprayers before using them again. Tobacco, grapes, tomatoes, garden vegetables, and fruit trees are particularly vulnerable to certain pesticides used on other crops. The remains left in a sprayer from a previously used pesticide can harm these crops.

The federal government has set standards that the workers, equipment, and procedures involved with pesticide use in industrial agriculture have to meet. These standards help to protect workers, crops and livestock, and the public—the ultimate consumers of the food—from the health risks of pesticide contamination or exposure.

Protection from Pesticides

There are steps everyone can take to protect against the known (and potential) health risks of pesticide use or exposure.

• After pesticide is used on an area, it must be aired out.
• One can investigate and use non-chemical alternatives to pesticides.
• Pest control companies should be screened before being hired to work in the home.
• Pesticides must be stored carefully.
• Pesticides must be disposed of properly.
• Pesticides must not be applied or disposed of in streams or areas where wildlife drink and feed. (Waste can travel so it's important to be aware not only of the immediate location, but the areas and waterways it might be connected to, or drain into.)
• The Internet, science teachers, and the media can help to keep the public educated and updated on environmental issues.

OUTSIDE AIR POLLUTION

A major concern of environmental health is the quality of the air people breathe. There are both natural and synthetic processes that decrease air quality, or cause air pollution. Following is a breakdown of some of the major areas of concern.

Acid Rain

Beginning in the 1970s, there has been growing concern about the problem of acid rain. Acid rain is rain with a high content of sulfuric acid, which is produced when sulfur dioxide combines with hydrogen. Sulfur dioxide is released from natural sources, such as volcanoes, sea spray, and rotting vegetation. Burning fossil fuels such as coal and oil also produces it. Once released, the sulfuric acid mixes with hydrogen, a gas that is already in the atmosphere. The resulting sulfuric acid falls back down to the earth as a pollutant, acid rain.

Acid rain poses health risks to people and nature. The danger for people is respiratory (breathing) problems such as asthma, dry coughs, headache, and eye/ear/nose/throat irritations. Another danger of acid rain is that it contains the remains of toxic metals. When acid rain falls, toxic remains can be absorbed by fruits, vegetables, and livestock and passed on to human consumers. Consumption of these toxic metals, such as mercury for example, can lead to brain damage, kidney problems, and even death.

The sulfuric acid in acid rain is a particular threat to forests and soils. Sulfuric acid competes with trees for vital nutrients, limits their hardiness to withstand cold temperatures, and triggers unhealthy growing cycles. Sulfuric acid also has a corrosive, or damaging, effect on buildings and statues.

VOCs (volatile organic compounds)

In science, something that can easily become airborne is called volatile. Chemicals that contain carbon, a fundamental element of all living organisms, are called organic. Volatile organic compounds (VOCs) are elements with both of these features.

VOCs are released when fuel, including gasoline, oil, wood, coal, and natural gas, is burned. They are also found in commonly used solvents, paints, and glues. The exhaust from cars is a big source of VOCs.

VOCs have been linked to serious health risks, such as cancer, but they are known mostly for their role in forming smog. Smog is a chemical haze, or fog, that is made heavier and darker by smoke and chemical fumes. It occurs when ultraviolet radiation from the sun comes into contact with atmospheric pollution.

Carbon Monoxide

Carbon monoxide is a colorless, odorless, tasteless gas that turns into carbon dioxide when it is burned. Produced by burning gasoline, natural gas, coal, oil, or other materials, carbon monoxide cripples the flow of oxygen to cells and tissues that cannot function without it. People who suffer from respiratory or circulatory problems are especially vulnerable to health problems from exposure to carbon monoxide.

Sulfur Dioxide

Sulfur dioxide is a toxic gas that can also be converted to a colorless liquid. It is produced when coal, oil, or sulfur is burned. A key ingredient in sulfuric acid, sulfur dioxide is also used in processes such as bleaching, preservation, and refrigeration. It is used heavily in generating paper and metal. Sulfur dioxide ranks as one of the most significant causes of air pollution, particularly in industrial areas.

Lead

Lead is a heavy, flexible metallic element that is often used in pipes and batteries. It is also

an ingredient in some gasoline and paint. Sources of lead in the environment include leaded gasoline, house and car paint, metal refineries (smelters), and the production of lead storage batteries. Lead can cause severe damage to the human brain or nervous system, particularly in children. It can also cause digestive problems, and some chemicals that contained lead have been shown to cause cancer in animals.

Lead-based paint can lead to serious health problems. Dust and chips can crack off the paint in tiny particles, but even a small amount of lead ingested into the system of a child or pregnant woman can have a serious impact. If a child swallows or inhales lead, it can cause learning disabilities and disorders of the nervous system. Adults who ingest high levels of lead may experience high blood pressure, headaches, digestive problems, pain in joints and muscles, and other health problems. In 1978, lead-based paint was banned because of the threat to public health, but homes and schools built before 1978 may still have lead-based paint in or on them. Lead-based gasoline is also in the process of being phased out.

Environmental Effects of Outside Air Pollution

According to the Environmental Protection Agency (EPA), 60 to 70 U.S. metropolitan areas—that are home to some 62 million Americans—do not meet air quality standards for one or more air pollutants. Total emissions of nitrogen oxides (NOx) that are thought to damage the environment have increased by 14 percent since 1970. Cars and power plants are large contributors to this problem. Chemicals that threaten the Earth's ozone layer (the atmospheric shield that protects the planet from harmful ultraviolet radiation) are another concern. If the integrity of the ozone layer is compromised, the Earth will be exposed to ultraviolet radiation and this could result in increases in the occurrence of skin cancer and cataracts (an eye disorder), as well as damage to crops and plankton (the tiny plants and animals that float in a body of water and are what fish eat). The reduction of plankton and plant life will lead to an increase in carbon dioxide levels. In fact, worldwide levels of carbon dioxide have increased by 8 percent since 1972. Although great strides have been made to control air pollution that is toxic to people and the environment, there is still a long way to go.

What to Do to Protect Against Outside Air Pollution

All the potential dangers in the air cannot be avoided, but it is important to try to limit exposure to pollutants or unhealthy levels of pollutants.

• Playing outside on days when the air quality is at an unhealthy level is not advisable (local television and radio stations generally report this).
• Homes and schools should be tested for lead-based paint.
• Lead-based paint must be properly contained or removed from homes and schools.
• Carpools can be coordinated to get to and from activities, thus cutting down on car fumes.
• People can get involved in recycling and pollution-control efforts in their communities.

INDOOR AIR POLLUTION

The quality of the air people breathe in outdoor activities is a concern, but the quality of the air indoors is an equally, possibly even more, significant issue of environmental health. Research suggests that Americans spend 90 percent of their time indoors. And, in recent years, scientific studies have revealed that the air in homes and other buildings may contain even more pollutants, or higher levels of pollutants, than the air outdoors. These severe levels of indoor air pollution have been found even in highly industrial metropolitan areas, where one might automatically assume that air pollution risks would be greater outdoors than indoors. In light of this research, organizations like the Environmental Protection Agency are taking a closer look at what's happening with air quality inside homes, schools, and offices. Some of the key threats to air quality, and in turn to human health, are discussed below.

Tobacco Smoke

Environmental tobacco smoke (ETS) is the mixture of the smoke from a lit cigarette, pipe, or cigar and the smoke exhaled by the person smoking. ETS exposure is sometimes referred to as passive smoking or secondhand smoking. Even though the affected person is not actively lighting up and inhaling, enough smoke is being breathed into the person's lungs to have a negative impact on his or her health.

ETS contains over 4,000 chemical compounds. According to the EPA, over 40 percent of these chemicals are known to cause cancer in humans or animals, and many of them are strong irritants. A 1992 EPA study (Respiratory Health Effects of Passive Smoking: Lung Cancer and Other Disorders) evaluated the risks of ETS to nonsmokers and concluded that ETS posed a significant health threat to nonsmokers, putting them at risk for a wide range of irritations and illnesses. Most significantly, the study indicated that, annually, exposure to ETS is responsible for about 3,000 lung-cancer deaths among nonsmoking adults.

The 1986 Surgeon General's Report concluded that physically separating smokers from nonsmokers in a home or office—by putting the smokers in a separate room—did not entirely eliminate a nonsmoker's exposure to ETS. Nonsmoking regulations have been put into effect in many offices and public areas to protect nonsmokers from the harmful effects of secondhand smoke. Nevertheless, individuals have to be conscientious about their exposure to ETS in private homes and unregulated public areas.

Radon

Radon is a colorless, odorless, radioactive gas produced by the naturally occurring breakdown of the chemical element uranium in soil or rocks. Radon gas is released into the air when radon is broken down. It can get into a home through dirt floors, cracks in concrete walls and floors, floor drains, and sumps (underground drainage system, or cesspool). When radon gas enters and becomes trapped in a home, it can build up to dangerous levels and pose threats to human health. In rare cases, building materials used in a home give off radon. Radon can also surface in well water.

REPORTED HEALTH EFFECTS OF ETS (SECONDHAND SMOKE) EXPOSURE

• There is an increased risk of lung cancer in nonsmoking adults.
• ETS endangers, or damages, the respiratory health of hundreds of thousands of children each year.
• Parents who smoke in the presence of their children increase the risk for the children to develop lower respiratory tract infections such as bronchitis.
• Infants and children exposed to ETS by smoking parents more frequently have problems with coughing, excess mucus, and wheezing.
• ETS annually causes between 150,000–300,000 lower respiratory infections in children under the age of eighteen months.
• Older children might experience reduced lung function due to ETS exposure.
• Asthmatic children are especially vulnerable to effects of ETS.
• Exposure to secondhand smoke can increase the number or severity of asthma attacks experienced by hundreds of thousands of young asthma sufferers each year.
• Each year, ETS might lead to the development of asthma in thousands of nonasthmatic children.
• The asthmatic condition of 200,000 to 1,000,000 children is worsened each year as a result of ETS exposure.
• ETS causes significant eye, ear, nose, and throat irritations.
• ETS may negatively affect cardiovascular (relating to the heart and lungs) health.

When inhaled, high levels of radon can cause lung cancer in people. It can also be unhealthy to swallow radon-contaminated water. But the most serious exposure is from breathing air with high levels of radon. Organizations like the Centers for Disease Control and Prevention, the American Lung Association, and the American Medical Association agree that radon causes thousands of lung-cancer deaths each year. There is also agreement that many of these deaths could be prevented by better controls on indoor air pollution. According to estimates by the Environmental Protection Agency, on average there are about 14,000 deaths caused by radon in the United States each year. Studies also suggest that smokers are especially vulnerable to health risks posed by radon.

Stoves, Heaters, Fireplaces, and Chimneys

Harmful pollutants, in the form of gases or particles, can be released into the air by combustion (or burning) processes that take place in the home. Poorly ventilated kerosene and gas space heaters, wood stoves, fireplaces, and gas stoves can release combustion products. Other sources include improperly installed chimneys and flues and cracked furnace equipment. Fireplaces and wood stoves, in particular, can backdraft (or draw) pollutants from the chimney into a room. Carbon monoxide and nitrogen dioxide particles are generated by combustion.

Carbon Monoxide

A colorless, odorless gas, carbon monoxide makes it difficult for the body to circulate oxygen. In large amounts, carbon monoxide can lead to unconsciousness and even death. Smaller amounts result in headaches, dizziness, nausea, disorientation, and fatigue. People who suffer from heart disease might experience increased chest pain when exposed to carbon monoxide. Beside people with chronic heart diseases, the negative health effects brought on by carbon monoxide exposure particularly endanger infants and the elderly.

Nitrogen Dioxide

Like carbon monoxide, nitrogen dioxide is a gas that cannot be seen or smelled. It irritates the eyes, ears, nose, and throat. Human exposure to large quantities of nitrogen dioxide (or repeated exposure to lower quantities over a long period of time) can cause shortness of breath or lead to increased risk of respiratory infection. Some studies with animals indicate that nitrogen dioxide exposure can lead to lung diseases such as emphysema. Adults and children who suffer from asthma or other breathing disorders are especially vulnerable if exposed to nitrogen dioxide.

Particles

Particles are released when fuel does not burn completely. They can enter and bury themselves in human lungs, where they can cause irritation or damage. Particles also provide a hanger for other airborne pollutants (such as radon, for example) to latch onto and use to gain entry into human lung tissue. Cancer-causing radon, for example, could latch onto a particle produced by incomplete combustion. The radon would be inhaled with the particle and end up lodged deep in the human lungs where it could lead to cancer.

Household Products

Many household products contain organic (carbon-containing) chemicals. These products can release polluting organic chemicals or compounds while in use or storage. Products with organic chemical ingredients include paints; varnishes; wax; many disinfecting, degreasing, or cosmetic agents; and fuels. According to the EPA, twelve common organic pollutants have been found in the air in homes at levels two to five times higher than the levels at which they were found in the air outside homes (even in industrial areas). EPA studies also indicate that people using household products, as well as others, can be exposed to high levels of chemical pollutants. These chemical pollutants also linger in the air even after the product is no longer being applied.

Evidence is still being gathered as to the short- and long-term health risks of organic chemicals released by household products, and what concentrations or lengths of exposure are dangerous. Findings to date suggest that health risks include respiratory tract irritation, headaches, dizziness, visual disorders, and impaired memory. A larger concern is that many organic compounds have been shown to cause cancer in animals and are suspected, or proven, to be cancer-causing agents in humans. While research continues, household products should be used in well-ventilated areas and according to label instructions.

Asbestos

A mineral fiber, asbestos was frequently used to insulate or fireproof building materials until studies began to reveal asbestos-related health dangers. The EPA has banned some asbestos products and manufacturers are limiting their use of asbestos products, but some older homes and buildings built before 1978 were built with asbestos-based materials. In these buildings, asbestos can appear in pipe and furnace insulation materials, shingles, textured paints, and floor tiles.

Asbestos fibers are dangerous when airborne. They can become airborne if asbestos-containing materials are cut, sanded, or disturbed in removal or remodeling efforts. Once airborne, tiny asbestos fibers can be inhaled and accumulate in human lungs, where they can cause cancer, meso-thelioma (cancer of chest and abdominal linings), and asbestosis. Asbestosis creates scar tissue in the lungs that cannot be repaired; this can be a life-threatening condition. Asbestos-related diseases have mostly been traced to high exposure on the job, or exposure to asbestos particles carried into a home on clothing and equipment by someone working a job involving high exposure to asbestos.

Lead

Like other chemicals that pose health risks, lead cannot be seen, smelled, or tasted. Since it does not break down naturally, trained professionals must physically remove lead sources from the environment they are polluting. Before

the health risks of lead were known, lead was used in paint and water pipes. Today, most house paint is almost entirely lead-free, and lead-based materials are not used in household plumbing systems. On the other hand, homes and buildings built before 1960, and even as late as 1978, may contain lead-based paint. Lead-based paint in good condition usually does not pose a risk. But lead-based paint in bad condition can cause serious problems.

Lead gets into the body from breathing contaminated lead dust from air, swallowing contaminated water, or ingesting lead-filled paint chips or soil. Problem sites can include window frames, walls, doors and doorframes, stairs, railings, banisters, and any objects or surfaces covered in lead-based paint. Hobbies such as refinishing furniture and making pottery or stained glass can produce lead remains. Workers who have jobs in construction, demolition, radiator repair, or handling batteries could carry dust from their job sites back to their homes. Soil that contains lead can also be easily tracked into the house from outdoors.

In spite of the growing awareness about the dangers of lead poisoning, the Centers for Disease Control and Prevention report that one in eleven American children has a high level of lead in their blood. Children can have especially serious health problems if they consume lead, causing learning disabilities, decreased growth, hyperactivity, and even brain damage. Pregnant women are also especially sensitive to lead-related problems.

Pesticides

Surveys have shown that at least one indoor pesticide product is used in about 75 percent of U.S. homes each year. Insecticides and disinfectants are used even more. Indoor exposure is responsible for 80 percent of an average American's exposure to pesticides, according to a recent study. The study also found that the air content of average homes could have high levels of as many as twelve different pesticides. While this research attributes 80 percent of an average American's pesticide exposure to indoor sources, actual pesticide use in the home does not accurately account for all the pesticides that are found in the air in a home. Contaminated air, water, or soil that is brought into a household from the outdoors can also contribute to the pesticide content in the home. Other contributors are stored pesticides, and household objects and surfaces where pesticides can accumulate, then later be released.

According to the 1990 records of the American Association of Poison Control Centers (AAPCC), 79,000 children were exposed to, or poisoned by, a household pesticide in that year. The AAPCC also reported that in almost 50 percent of households with children under age five, at least one pesticide product was stored in a place children could access.

When people use pesticides (insecticides, disinfectants, repellants, and rodenticides) in and around their homes, they should always keep in mind that how and where they handle, apply, and dispose of pesticides might also affect the environment and other people, pets, plants, and wildlife.

Effects of Indoor Air Pollution

There can be both short- and long-term effects from exposure to indoor air pollution. Short-term or immediate effects include irritations of the eyes, nose, and throat; headaches; dizziness; and fatigue. Symptoms of diseases such as asthma might appear not long after a single, or repeated, exposure to indoor air pollutants. Other, more serious, health problems, such as respiratory diseases, heart disease, and even cancer, may surface a long time after a person's first exposure to an indoor air pollutant (or several indoor air pollutants). These serious, even fatal, diseases might also appear after a person has been repeatedly exposed to the same air pollutants over a long period of time.

What to Do to Protect Against Indoor Air Pollution

All the pollutants can't be eliminated from the air people breathe, nor can there be an avoidance of some exposure to them. It is possible, however, to have protection against exposure to indoor air pollution, or at least against dangerous levels of indoor air pollution, by taking some basic steps:

TOBACCO SMOKE. Tobacco smoke exposure can be reduced or eliminated by:

• not smoking
• discouraging smoking in the home
• discouraging people from smoking around infants and children

RADON. Exposure to radon can be controlled by:

• being sure all living space is properly ventilated
• encouraging parents/teachers to have the air circulating at home and in school checked for radon levels and other pollutants
• having well water tested, and if necessary treated, for high levels of radon
• taking time to identify the sources of air pollution problems
• keeping windows open when painting to control, or prevent, problems
• encouraging everyone at home or at school who works on painting or soldering projects or hobbies to work carefully and clean up thoroughly
• investigating products and services to improve ventilation and clean air
• keeping living and working spaces as clean and dust-free as possible

STOVES, HEATERS, FIREPLACES, AND CHIMNEYS. Pollution from stoves, heaters, fireplaces and chimneys can be eliminated or reduced by:

• following instructions when installing and using unvented, fuel-burning space heaters
• having exhaust fans over gas cooking stoves and adjusting burners correctly
• making sure wood-stove emissions meet EPA standards
• selecting a stove that is the correct size for the space in which it will be used
• arranging the annual inspection of central air conditioning and heating systems
• repairing damaged or broken parts immediately

HOUSEHOLD PRODUCTS. With household products it is advisable to:

• read and follow label instructions
• safely dispose of chemicals that are old or no longer used
• buy household products on a need-only basis so a lot of chemicals aren't stored
• limit exposure to paint strippers, adhesive removers, and aerosol spray paints
• ask dry-cleaners to remove as much as possible of the perchloroethylene (active chemical agent used in dry-cleaning)

ASBESTOS. Because of asbestos's hazardous nature one should:

• not tamper with asbestos material that is in good condition in the home
• avoid cutting, ripping, or sanding asbestos-based materials
• have a professional contain or remove asbestos in the home

LEAD. To prevent problems related to lead, it's important to:

• get tested for lead poisoning
• use a solution of water mixed with powdered dishwasher detergent to wash floors and windowsills
• be sure children are not chewing on objects or surfaces covered with lead-based paint
• get professional help to remove lead paint from the home
• have water tested for dangerous levels of lead
• run cold water for thirty to sixty seconds if it has not been used in over two hours to give pipes a chance to clear before drinking or cooking
• not store food or liquid in lead crystal or in pottery with high lead content

PESTICIDES. For protection from pesticides, it's important to:

• read and follow exactly all label instructions
• never use a large amount of a pesticide, or use it more frequently than what is indicated
• limit exposure to moth repellants
• keep living space clean and well ventilated
• avoid direct physical contact with pesticide being used
• cover exposed human/pet food and water containers before applying pesticides

ENDOCRINE DISRUPTERS

Most living animals, including human beings, have an endocrine system. The endocrine system—made up of glands such as the pituitary gland and thyroid gland—functions by releasing hormones into the bloodstream. Hormones are like packets of information, which are sent to different cells to stimulate specific reactions or processes that help to keep the body functioning properly. Some man-made chemicals look and act like these naturally-occurring hormones. These chemicals are called endocrine disrupters because, when they get into the bloodstream of a person or animal, they can prevent the real hormones from doing their jobs. Endocrine disrupters are synthetic chemicals or chemical byproducts. They are fat-soluble, which means they dissolve in fat, not water, and therefore remain in the body longer. Most endocrine disrupters come from pesticides or industrial chemicals.

WHAT DOES THE ENDOCRINE SYSTEM DO?

Body functions affected by the endocrine system in humans are:

body growth; organ development; metabolism; kidney function; body temperature; calcium regulation; blood pressure; reproductive cycles.

In addition to the above list, the following are also affected just in animals:

mating behaviors; migration; fat distribution; hibernation

What Endocrine Disrupters Do

Endocrine disrupters usually interfere with real hormones in one of three ways. They can be mimics, blocks, or triggers. Mimics imitate real hormones. The mere presence of these chemical imposters disturbs the body's delicate hormonal balance. When this balance is off, the body does not function properly. Blocks are endocrine disrupters that actually get in the way of real hormones. Hormones have to attach to a certain part of a cell, called a receptor site, to tell the cell what it needs to do to keep a particular organ or process running smoothly. Endocrine disrupters can block this information by attaching to a receptor site so that the real hormone cannot. With the endocrine disrupter in the way, the information the cell needs to function does not get through. Triggers do not just imitate or block real hormones; these endocrine disrupters actually give the body directions about what it should do. When the body responds to these signals, things go wrong because, unlike the real hormones, the endocrine disrupters do not know what they should be telling the body to do. The artificial triggers cause inappropriate growth, changes in metabolism, or other abnormal interactions that can create biological chaos.

Where Endocrine Disrupters Come From?

A wide range of synthetic chemicals and chemical byproducts developed for commercial and industrial purposes are suspected of being, or producing, endocrine disrupters. Many detergents, pesticides, plastics, and varnishes, for example, are made with or from endocrine disrupter chemicals. Through production and use of these products, endocrine disrupters are released into the environment where they can pollute food and water sources. Later, these artificial, hormone-disrupting substances can get into the bloodstreams of the people or animals who consume food and water from the contaminated sources.

Endocrine disrupters do not just come from environmental pollution. They can also be contained in synthetic drugs and be absorbed into a person's bloodstream when the drug is taken.

Most Common Endocrine Disrupters

The most common endocrine disrupters are known as environmental estrogens. Examples include PCBs and Dioxin. Environmental estrogens mimic the natural estrogens (female sex hormones) and androgens (male sex hormones), which control reproduction and sexual characteristics. Environmental estrogens have their biggest impact on fetuses (infants developing in a mother's womb). Once a baby is born, their sexual features are developed, but in the womb the sex hormones play a key role in shaping an infant's sexual makeup. The presence of artificial hormones in the mother's body can interfere with, or alter, the normal course of a fetus's sexual development.

Environmental estrogens have a particularly dramatic effect on males. Exposure to environmental estrogens in the womb can lead to a male being born with an unnatural amount of female sexual characteristics, or even a hermaphroditic condition, which is when a person has both male and female sexual features.

Sexual characteristics are not the only element that environmental estrogens can affect. Other biological features—such as bones, cardiovascular system, memory, and immune system—can be weakened in a male or female baby who is exposed to environmental estrogens in the womb.

DOCUMENTED EFFECTS OF ENDOCRINE DISRUPTERS

Polluted Species from the Great Lakes

The Great Lakes area is known to be a highly contaminated area, with particularly elevated levels of endocrine disrupters. Studies done on species from the Great Lakes area have revealed a range of abnormalities, such as the following:

• Low rates of egg production, abnormal enlargement of the thyroid gland, early mortality rates, and low reproduction rates have been seen in several fish species, especially salmon.
• Birds in the area (including bald eagles and herring gulls) that feed on these fish have demonstrated symptoms similar to those observed in the fish.
• Hermaphroditic fish (genetically male fish with female genitals) have been observed.

The Florida Everglades

A study of male alligators was conducted in Lake Apopka, Florida, which is situated near a nowclosed chemical processing plant. DDE, a byproduct of the pesticide DDT, was generated at this plant. The male alligators in this area were found to have abnormally small penises, while male alligators in other (nonpolluted) Florida regions had normal size genitalia. Scientists attribute the Lake Apopka alligators' condition to exposure to DDE.

DES

A prescription drug called diethylstilbestrol (DES) was produced in the 1940s. The drug, which contained a synthetic estrogen compound, was administered to women who experienced complications during their pregnancies. It was later discovered to cause problems in the daughters of the women. The daughters who had had fetal exposure to the drug had depression, decreased fertility, abnormal pregnancies, organ dysfunction, and increased occurrences of cancers, especially of reproductive organs.

The Risks Associated with Endocrine Disrupters

Many studies conducted on animal populations in chemically contaminated areas strongly suggest that endocrine disrupters are potent and frequent pollutants of our food and water sources. Abnormalities, particularly sexual

abnormalities, have been observed in the offspring of the animals that live, feed, and drink in these contaminated areas. Although similar studies have not been undertaken in human populations, many scientists are concerned that the risks of human exposure to endocrine disrupters might be significant.

Pesticides can get into food supplies directly or indirectly. They can be sprayed on crops, which people later consume. Industrial pollution releases endocrine disrupters into the environment, exposing fish, cattle, hogs, and poultry. If the fish and animals ingest the chemicals, they will be contained in their fat and later passed on to human consumers.

Scientists have also expressed concern about plastics and artificial materials used in food preparation and storage. They are concerned that a leaching process might take place. Leaching is when dangerous products found in plastics move from the plastics into the food in the container. Although it is in the early stages, recent research has shown that endocrine disrupters can leach out of plastic containers into the liquid they are holding. Similar concerns have been raised about tin cans. Research suggests that the coating a tin can is treated with might contain endocrine disrupter chemicals, which are able to leach into the can's contents.

Incinerators and other equipment that use combustion release endocrine disrupters into the atmosphere. Once released into the atmosphere, they pose a risk to human life and wildlife.

Drinking water sources must also be monitored carefully. Contaminated drinking water could also expose humans to endocrine disrupters.

The effects of exposure to endocrine disrupters are not always immediate. It may take awhile for symptoms to surface, or the effects and problems could show up in the next generation (meaning in the children of the person who was exposed).

What Can Be Done to Protect Against Endocrine Disrupters

The scientific community is pursuing research in the area of endocrine disrupters. Environmental groups like the World Wildlife Foundation are encouraging the government to crack down on industry's use of chemicals that are proven (or suspected) to be endocrine disrupters. And more testing needs to be done to determine other chemicals that are endocrine disrupters. While investigation and regulation of endocrine disrupters is taking place on a national scale, people can protect and educate themselves on an individual level, too. Some suggestions for limiting exposure to endocrine disrupters are to:

THE BLACK PLAGUE

Environmental health has been an issue since ancient times. Even in the earliest days of civilization, it became clear that infections could be produced and spread in certain environments. Bubonic plague, nicknamed "the Black Plague," which claimed 25 million lives in Europe from 1347 to 1532, is an example of an infectious disease made worse by environmental conditions. Unsanitary living conditions gave the fleas and rats that carried the disease access to homes, bedding, and food. As people realized how important the proper management of drinking water, food supplies, and sewage was, new methods were developed to combat contamination and pollution. In modern society, health problems are now more commonly thought to be lifestyle-related, rather than correlated to environmental causes. But health risks from the environment can be substantial even in a sophisticated, technologically advanced society. In fact, many of the modern processes and products themselves are responsible for creating a whole new range of environmental risks to be explored and controlled.

• limit fat and oil intake (since endocrine disrupters tend to accumulate in fats)
• avoid cooking, microwaving, and storing food in plastic or styrofoam containers
• use pesticide-free, organically-grown foods
• not handle pesticides
• investigate the origin of fish, poultry, and meat by asking the grocery store manager what the source is
• encourage local store owners and managers to purchase produce and animal-based products from waters, farms, and rangelands that have been tested for pollution and contamination
• get involved in antipollution efforts in your community
• write to state legislators to find out their views on key statewide environmental issues

FOR MORE INFORMATION

Books

Dolan, Edward F. Our Poisoned Waters. New York: Cobblehill, 1997.

Kahl, Jonathan D.W. Hazy Skies: Weather and the Environment. Minneapolis, Minn.: Lerner Publications, 1997.

Willis, Terri and Wallace B. Black. Cars: An Environmental Challenge. New York: Children's Press, 1992.

Wright, David. Facts on File Environmental Atlas. New York: Facts on File, 1998.

Young, Lisa. Pesticides. New York: Lucent Books, 1995.

Zike, Dinah. Earth Science Book: Activities for Kids. New York: John Wiley and Sons, 1993.

Zonderman, Jon. Environmental Diseases (Bodies in Crises). New York: Twenty-First Century Books, 1995.

Web sites

Children's Environmental Health Network. [On-line] http://www.cehn.org (Accessed August 19, 1999)

Earthforce. [Online] http://www.earthforce.org (Accessed August 19, 1999)

Environmental Health Coalition. [Online] http://www.environmentalhealth.org (Accessed August 19, 1999)

The Environmental Protection Agency's (EPA) site for students. [Online] http://www.epa.gov/students (Accessed August 19, 1999)

National Education Association Health Information Network. [Online] http://www.nea.org (Accessed August 19, 1999)

ENVIRONMENTAL HEALTH

Environmental health is "the segment of public health that is concerned with assessing, understanding, and controlling the impacts of people on their environment and the impacts of the environment on them" (Moeller, p. 1). The importance of environmental health has received increasing attention since the early 1990s as the connections between health and environment have come to be better understood and environmental challenges to health have become more pronounced.

Environmental health problems arise from poor air quality, lack of clean water, unhygienic living conditions, dangerous workplaces, unsafe food, careless disposal and treatment of wastes, and toxic pollution. A number of longer-range and more globally dispersed problems also pose significant challenges to health, including global climate change, depletion of the ozone layer, acid rain, nitrogen loading, loss of biodiversity, deforestation, loss of topsoil, increased pressure on resources as a result of changing patterns of consumption, and a rapid increase in the human population (McMichael, 2001; McCally, 2002).

The Global Environmental Health Picture

Although health around the world improved on average over the last half century—due mainly to improvements in environmental health fundamentals such as access to clean water, nutritious food, and adequate sanitation, alongside public health basics such as prenatal care and immunizations— it is likely that these gains will be lost if the environmental foundation for health continues to deteriorate. Billions of people already suffer from the effects of degraded environments: At the beginning of the twenty-first century fully one-third of the global burden of disease was attributed to environmental factors (Murray and Lopez).

Lack of clean water for drinking, inadequate sanitation, and lack of hygiene affect a third to a half of the world's population and are responsible for 7 percent of all death and disease globally. Chemical agents, particularly in the form of air pollution, are considered major causative factors in increased rates of bronchitis, heart disease, and cancer. The incidence of asthma is mushrooming. Certain forms of cancer are on the rise. The health of people around the world is diminished by exposure to toxic substances such as lead, mercury, arsenic, cadmium, and dioxins. As local and global ecosystems show increasing signs of stress, human health is likely to become far less stable and far more difficult to maintain. Children are hit especially hard by environmental health problems: The World Health Organization estimates that environmental hazards kill at least 3 million children under age five each year (United Nations Environment Programme).

There is a broad international consensus that the earth's ecosystems are under considerable strain, and global environmental decline will be the defining public health context in the twenty-first century (McMichael, 2001). According to an international report, the overall health of the earth's natural systems declined by 37 percent in the 1990s (World Wildlife Fund), fueled largely by population growth combined with unsustainable levels of consumption and production, which have increased in aggregate even more quickly than have human numbers.

Environmental Health in the United States

Concern with environmental health in the United States has long focused almost exclusively on the problem of toxic pollution, and concern about toxins has shaped the American regulatory, legislative, and philosophical approach to environmental health. Since the publication of Silent Spring (Carson) the country has been alerted to the mortal danger of exposing human beings and other life-forms to many products and by-products of an industrialized lifestyle. Although the negative effects of environmental pollution on human health cannot be denied, the existence and magnitude of danger associated with particular processes and products remain controversial.

One reason for the controversy is that powerful interests typically have a stake in denying that their industries create health hazards. Nuclear industries deny that low-level radiation causes cancer. Cigarette manufacturers deny a causal link between passive smoking and cancer. Manufacturers of asbestos products take a similar stand about asbestos, as do manufacturers of agricultural pesticides in regard to their products.

A second reason for the continued controversy is that because causal connections between human health and environmental pollution are inherently difficult to establish, the affected industries can hire competent scientists to dispute claims of environmental hazards to human health. In general, three types of evidence can be used to show that an environmental constituent is a health hazard, but none can establish that connection beyond dispute (Luoma).

First, nonhuman animals can be exposed to a suspected health hazard and the effect can be observed. This cannot prove anything conclusively about human exposure because human beings are biochemically different from nonhuman animals. Also, to establish a connection quickly and at minimal cost, nonhuman animals often are exposed to doses much larger than those to which human beings are expected to be exposed. The effect of a small dose on human beings cannot be established conclusively from evidence about the effects of much larger doses on nonhuman animals.

A second method of investigation is to expose human beings over short periods to mild doses of materials suspected of causing serious health problems when exposure is considerably greater or more prolonged. The problem here is that some substances may be so toxic that it would violate human rights to expose people deliberately even to mild doses. Other substances, in contrast, may not have a deleterious effect at low levels of exposure but may be toxic at higher concentrations or over longer periods. In these cases public health hazards may be underestimated or missed entirely.

Third, in epidemiological studies a substance is tested by comparing the rate of disease in one population with that in another in an attempt to correlate differences between the two populations' rates of disease with differences in their rates of exposure. However, it is difficult to establish in that way a connection between a specific suspected toxin and illness or death because under normal conditions people are exposed constantly to many suspected toxins of various strengths for varying periods. It therefore is difficult to isolate the effect of any single substance. Also, the effect of exposure, if there is one, is often weak. In a small population, for example, few additional cancers can be expected to result from exposure to low-level radiation. In addition, the cancer effect is long delayed and spread out in the population over a forty-year period, making it difficult to detect at any specific time (Stewart). Finally, radiation exposure and cancer exist in the human population in any case, and so it is impossible to determine that any given cancer is caused by exposure to low-level radiation or that the low-level radiation in question is related, for example, to a nuclear industry (Stewart).

Basically the same considerations apply when the issue is the effect of exposure to passive smoking, asbestos, or agricultural pesticides. Thus, controversies can continue for decades. Nevertheless, the weight of evidence supports the claim that the exposure of human beings to chemicals and other products and by-products of industrial civilization is often harmful to human health.

The Problem of Toxins in the United States

"Since the 1950s, age-standardized cancer incidence rates in the U.S. have increased by 43.5 percent" (Epstein, 1992, p.233). Death from cancer has increased at a similar rate. The best attempts to isolate the causes of cancer have resulted in the conclusion that environmental factors account for 60 to 90 percent of cancers. The rest are attributable to inherited tendencies and internal biochemical malfunctions (Ep-stein, 1987).

Studies have shown cancer effects from doses of radiation that previously were thought to be safe. In one study a distinguishing fact about children who died of cancer before age ten compared with both those who died of other causes and those who survived to age ten is that the cancer victims' mothers received on average twice as many X rays while pregnant (Stewart). Another study showed a strong statistical association between a father's exposure to external radiation while working at a nuclear-waste reprocessing plant before a child was conceived and that child's chance of contracting leukemia (Gardner).

Radiation is not the only risk factor for cancer: Pesticides and other chemicals are implicated as well. A study showed that the mammary adipose tissue of women with breast cancer contained significantly more residues of chemicals associated with pesticides than did the mammary tissue of women with nonmalignant tumors (Falck et al.). Another study revealed that among white male scientists and engineers those who were members of the American Chemical Society had significantly more deaths from leukemia and lymphatic cancer (Arnetz et al.). A study of men from Iowa and Minnesota showed a link between elevated environmental chemical exposures that resulted from living near a factory and two types of cancer: non-Hodgkin's lymphoma and leukemia (Linos et al.). Non-Hodgkin's lymphoma also has been linked to the use of certain pesticides (Weber). Foundry workers in Denmark who were exposed to elevated levels of silica dust, metallic fumes, carbon monoxide, and several organic chemicals had markedly elevated rates of lung cancer (Sherson et al.). Occupational exposure to asbestos is considered responsible for 8,000 to 12,000 deaths each year in the United States (Rauber).

Typically, years intervene between exposure to environmental contaminants and an associated cancer or death. However, in some cases the connection between environmental pollution and human mortality is more direct. The "U.S. Office of Technology Assessment estimates that the mix of sulphates and particulates in ambient air may cause 50,000 premature deaths in the United States each year— about 2 percent of annual mortality" (Postel, 1986, p. 34). Toxic chemicals released into the air in 1988 were estimated by the U.S. Environmental Protection Agency (EPA) to cause "up to 3,000 cases of fatal cancer yearly as well as birth defects, lung disease, nervous system disorders, liver damage, and other health problems" (U.S. General Accounting Office, p. 8). When all types and sources of air pollution are considered, the American Lung Association puts the toll at 120,000 premature deaths per year (French).

There is increasing evidence that indoor air is often a health hazard. Radon in homes is believed to be a leading cause of cancer. The "sick building" syndrome is also a concern; it is the phenomenon of buildings inducing illnesses of various sorts in a large percentage of the people who spend considerable amounts of time in them. For example, chemicals in materials used to build and decorate the Dupage County Judicial and Office Facility in Wheaton, Illinois, were considered responsible for a variety of employee illnesses. As a result, a nearly new building was evacuated temporarily.

Scientists have been concerned particularly about exposure to heavy metals such as lead and mercury. Although exposure to lead has been reduced greatly, pockets of the population still are exposed to lead in peeling household paint, and everyone is exposed to lead in outdoor air pollution and food. The health effects of lead are well documented and include serious and irreversible impairment of children's neurobehavioral development (Brooks et al.). Mercury contamination also has been of particular concern. As with lead, the health effects of mercury are relatively well understood, largely because of several largescale exposures, including the Minimata Bay disaster, in which a whole Japanese village was poisoned after eating mercury-laced fish. Methylmercury is absorbed readily by fish in polluted aquatic environments. When humans eat contaminated fish, the methylmercury is absorbed readily into the bloodstream and tissues. Mercury can cause tremors, dementia, and congenital neurological deformities (Brooks et al.).

Beginning in the 1990s, concern has intensified about a group of chemicals called persistent organic pollutants (POPs). Those chemicals include the polychlorinated biphenyls (PCBs); pesticides such as DDT, chlordane, aldrin, and heptachlor; and industrial by-products such as dioxins. POPs are fat-soluble and accumulate in the fatty tissues of animals, where they persist for long periods. Research suggests that POPs are "endocrine disruptors": They mimic hormones and may play a significant and largely unacknowledged role in altering reproduction and development. Endocrine disruptors have long concerned wildlife biologists, who believe that declines in avian and amphibian populations are linked to POPs in the environment (Colborn, Dumanoski, and Myers). The way in which these chemicals affect humans is unknown, although some research has connected exposure to POPs with diminished sperm quality and quantity, impaired sexual function, increased testicular cancer, hypospadias, and cryptorchidism (Solomon and Schettler).

Environmental Racism

The risks of contracting environmentally influenced diseases and deaths are not distributed evenly across the population in the United States. Geographically, the people at greatest risk are those who live near sources of industrial pollution such as factories and certain types of mines and those who live near deposits of toxic waste. For example, it seems that a geometrically increasing cancer rate for people in some communities in Cape Cod, Massachusetts, is due to toxic deposits from the nearby Otis Air Force Base (Hallowell). By 1989, 14,401 sites of toxic contamination had been noted in 1,579 military installations around the United States (Renner). When cancer rates are plotted on a map of the nation, the places that show the highest rates are areas of industrial production such as Chicago, Detroit, northern New Jersey, and the lower Mississippi valley.

There is also a disparate impact on minority communities that is referred to as environmental racism. "Three out of every five African Americans and Hispanics live in a neighborhood with a hazardous waste site, and … race is the most significant variable in differentiating communities with such sites from the communities without them" (Steinhart, p.18). "Probably the greatest concentration of hazardous-waste sites in the United States is on the predominantly black and Hispanic South Side of Chicago" (Russell, p. 25). With 28 million pounds of toxics poured into that area annually, the U.S. Environmental Protection Agency (EPA) estimates that the risk of cancer is 100 to 1,000 times the normal risk (Lavelle). According to the federal Centers for Disease Control, "lead poisoning endangers the health of nearly 8 million inner-city, largely black and Hispanic children" all over the United States (Russell, p. 24). Rural minority groups suffer disproportionately as well: "2 million tons of radioactive uranium tailings have been dumped on Native American lands; reproductive organ cancer among Navajo teenagers is seventeen times the national average" (Russell, p. 24).

Environmental racism is international as well as domestic. Toxic waste from industrial countries has been deposited in Africa (Jacobson). Some corporations in industrial countries continue to manufacture pesticides that are considered too dangerous for use in their own countries. Those pesticides are sold to farmers in the Third World, resulting in 10,000 to 40,000 poisonings per year (Postel, 1988). The Bhopal accident, in which 2,000 people were poisoned by a chemical leak from a factory in India, highlights the fact that environmental safeguards in the Third World are sometimes inadequate. The company that owns the factory is based in the United States, where it maintains higher standards of safety in its factories.

The Legal Structure

According to traditional Anglo-American jurisprudence, when one person injures another person, the injured party can sue in court to recover damages. The legal rules governing those proceedings constitute the law of torts. This body of law is largely unhelpful, however, when injuries are due to most forms of environmental pollution because it is difficult to prove that a harm such as a case of cancer resulted from a particular emission of radioactivity or a certain dumping of toxic waste. Also, it would be inefficient for each injured party to sue individually, as was done traditionally, when the activity in question is alleged to affect many people, possibly thousands. Finally, tort actions can take place only after harm is done, and it is preferable to use the law to avoid harms when possible. Thus, the major role of government in the area of environmental health lies in the regulatory process.

In 1970 the National Environmental Policy Act was signed into law to "fulfill the responsibilities of each generation as trustee of the environment for succeeding generations." The EPA, which was established soon afterward, required that most federally funded projects be accompanied by an environmental impact statement so that the deleterious effects of those projects could be recognized and possibly ameliorated. Subsequent legislation has given the EPA the authority, for example, to regulate processes that pollute the air and water (the Clean Air Act and the Clean Water Act); locate, authorize, and fund the cleanup of hazardous wastes (the Resource Conservation and Recovery Act, which established the Superfund); and control the use of pesticides (the Federal Insecticide, Fungicide, and Rodenticide Act). States have their own EPAs that perform similar functions.

The U.S. EPA is not the only agency with the responsibility to oversee activities that can affect environmental health. The U.S. Department of Energy (DOE) oversees the disposal of nuclear waste, the U.S. Department of Agriculture (USDA) helps determine consumer exposure to pesticide residues in food, and the U.S. Department of Labor protects the health of workers through the Occupational Safety and Health Administration (OSHA). In addition, most states have administrative agencies with similar responsibilities for intrastate activities.

Because Congress has authorized those agencies and the many subagencies through which they operate to protect the public, courts are reluctant to intervene, making private lawsuits particularly difficult. If an agency is operating within its congressional mandate and arguably is doing its job in a reasonable fashion, the courts usually will protect both the agency and those in compliance with its standards from private lawsuits seeking compensation for environmentally related illnesses. Thus, the protection of environmental health depends much more directly on the actions of those agencies than on the concerns of private citizens and their elected representatives.

Enforcement Problems

As was noted above, the protection of human health from environmental contamination in the United States is largely the responsibility of the EPA and other federal and state agencies. Unfortunately, the performance of those agencies is sometimes disappointing. The EPA's regulation of pesticides exemplifies the general problem. The EPA regulates pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act. The general public is exposed to pesticides primarily through residues in food and contamination of the groundwater that serves as a major source of drinking water. The EPA recognized in 1988 that "forty-six pesticides … contaminate groundwater solely as a result of normal agricultural use" (Fultz, p. 3). However, a registered chemical can remain in use for up to fifteen years after it is discovered in groundwater before a decision is made about its continued use. An example is atrazine, a pesticide that is in widespread agricultural use (Fultz). For pesticides that already have been found to be toxic, the EPA has not lowered acceptable exposure through residues in food in light of additional exposure through drinking water.

Not all pesticides in widespread use are registered with the EPA, resulting in the continued exposure of the public through food and water to pesticides that have not been tested for their "potential to cause birth defects, cancer, and other chronic health effects" (Fultz, p. 5). Exemption from the registration requirement is given in so-called emergencies for one year at a time, but some exemptions have been granted for more than a decade, during which time people have been exposed to pesticides of unknown toxicity (Guerrero, 1991b). Also, the EPA continues to emphasize the control of point sources of water pollution such as factories and municipal sewer systems instead of nonpoint sources such as agricultural runoff despite evidence that nonpoint sources pose a greater water pollution problem (Guerrero, 1991b). This may be due to the fact that the USDA promotes the use of many pesticides to increase crop yields even though those chemicals constitute health hazards.

Unfortunately, the EPA's inadequate protection of public health from the dangers of pesticides is typical. Similar stories can be told about surface-water pollution, hazardous waste management and cleanup, enforcement of the Clean Air Act, and U.S. Department of Energy (DOE) decisions about the disposal of nuclear waste: "The National Research Council estimated that only 2 percent of at least 60,000 chemicals that are used widely have been comprehensively studied for toxic effects" (Ziem and Davidoff, p. 88).

In addition to poor funding, a general reason for inadequate protection is that agencies tend to establish such close ties to the industries they are charged with regulating that they identify with industry perspectives and needs. An agency's capture by industry results partly from industry offers of future high-paying employment to regulatory personnel who are "reasonable." Another factor may be pressure on an agency by the legislators who are responsible for approving its budget. Those legislators may depend on the regulated industry for campaign contributions (Sanjour).

Conscientious federal employees who try to regulate effectively are relegated to tasks that have little impact. Employees who blow the whistle on an agency's failure to do its job must go before the presidentially appointed Merit System Protection Board, which may be more interested in protecting the president and "the system" than in protecting the whistle-blower (Sanjour).

There is also the appearance of racism in the EPA's enforcement efforts: "Penalties under hazardous waste laws at sites having the greatest white population were about 500 percent higher than penalties at sites with the greatest minority population" (Lavelle, p. S2). This disparity can be accounted for only by race, not by income. There is a similar disparity of 46 percent in penalties concerning nontoxic waste, air pollution, and water pollution. It takes 20 percent longer for toxic waste sites in minority areas to be placed on the priority list for cleanup, and the cleanup in minority areas is more likely than that in white areas to consist only of containment of the waste rather than treatment that removes its toxicity.

Environmental racism also appears to affect government regulation of international trade. For example, pesticides banned in the United States because of their toxicity to human beings can be manufactured and then sold abroad. Some return as residues on imported food.

Decisional Frameworks

How should decisions about environmental health be made? Advocates of free trade and free markets suggest that market mechanisms can protect public health adequately. However, from the perspective of firms competing for customers, environmental protection seldom makes sense. A manufacturer's plastic toys, for example, seldom are more attractive to customers because the water and air used in its manufacturing processes were purified before being released into the environment. Similarly, catalytic converters on automobiles add to cost but do not improve cars in most customers' eyes. Without government mandates requiring all the producers in an industry to protect the environment, the cost of such protection impairs the competitiveness, or reduces the profits, of conscientious firms that act alone. Thus, the free market discourages the protection of environmental health in the absence of government-mandated regulations such as those administered by OSHA and the EPA.

The EPA and other government agencies have been faulted for their failure to oppose the market-driven activities of private enterprise with sufficient vigor. Three kinds of reforms may be ameliorative. First, agency personnel could be barred for five years from employment, directly or indirectly, by companies that their agency regulates. This would encourage greater independence of agency personnel from the perspectives of regulated companies. Second, campaign finance reform could help diminish the influence of financial interests on the regulatory process. Third, whistle-blowers could be given special job and financial protection (Sanjour).

What decisional framework should those agencies employ? Some libertarians, who stress the importance of individual rights, maintain that any environmental pollution that may harm anyone should be disallowed. The government should "enjoin anyone from injecting pollutants into the air, and thereby invading the rights of persons and property. Period" (Rothbard, p. 5). However, this purist approach seems unrealistic because it would disallow, for example, most manufacturing and almost all uses of fossil fuels, including use in automobiles. Polluting the environment in ways that are potentially harmful to human health is too ingrained in industrial ways of life to be eliminated entirely.

Pointing to the benefits of industrialization—airconditioning in the summer, heating in the winter, rapid transportation, and sophisticated medical interventions— some people maintain that pollution should be allowed until the risks to people outweigh the benefits. According to this view, government agencies such as the EPA should use risk-benefit analysis to determine permissible kinds and levels of pollution (Ruckelshaus).

Critics maintain, however, that risk-benefit analysis favors continued pollution over health-related concerns. First, current levels of pollution often are assumed to be acceptable and are used as precedents for future decisions. Second, whereas the benefits of current pollution practices are assumed, risks must be proved scientifically, a task that is difficult. Third, risk-benefit analysis depends largely on subjective judgments of "experts" whose opinions may reflect employers' interests (Winner).

Some people suggest avoiding subjectivity by using cost-benefit analysis (CBA), in which all the costs and benefits of proposed pollution-controlling regulations are expressed in monetary terms. The alternative with the highest net benefit should be chosen. Costly health hazards thus would be taken into account. The EPA usually allows environmental impact statements to employ CBA, and the Nuclear Regulatory Commission uses CBA regularly.

However, there are many problems with CBA. First, the costs and benefits associated with the length and quality of human life, which are affected by environmental health, cannot be translated reliably into monetary terms. Second, subjectivism remains because there is great uncertainty in projections of health hazards (Shrader-Frechette). Third, by employing money as its standard, CBA takes into account views and desires only insofar as they are expressed in monetary terms. The opportunity for that expression is proportional to the money at people's disposal. Using CBA, then, agencies would give protection to people not equally but in proportion to their wealth or income. In regard to the actions of government agencies CBA denies equal protection of the law. Fourth, using normal economic techniques, CBA discounts the future, making a present cost or benefit larger than an otherwise equivalent but future cost or benefit. This biases public policy toward the short term. If the duty to avoid or minimize harming people is based on human rights, harming future generations is morally equivalent to harming contemporaries. CBA discounts the lives and well-being of future generations (Wenz).

Alternative Frameworks

Instead of CBA, the following are possible rules of thumb. First, the burden of proof should be reversed from that employed in risk-benefit analysis. Before a potentially harmful addition is made to the environment, its safety should be demonstrated. At the beginning of the twenty-first century, for example, potentially carcinogenic pesticides can be used widely for ten to fifteen years before investigations are completed. Products are withdrawn then only if they are demonstrated to harm public health. The burden to demonstrate its safety should be on those who want to expose people to a new chemical.

Second, the people at greatest risk should be given the greatest voice in decisions about creating or using potentially hazardous substances (Shrader-Frechette). For example, corporate officials and owners interested in manufacturing processes that create toxic wastes would retain a significant voice in regulatory decisions if they could and would store the wastes near themselves and their families.

Third, through subsidies the government should encourage sustainable agriculture, integrated pest management, mass transit, energy conservation, and other practices and products that reduce the introduction of health hazards into the environment.

Fourth, when the indirect costs of a product can be calculated reliably, those costs should over time be added as a tax to the consumer price of that product. For example, the price of gasoline should reflect the costs associated with the deleterious health effects of smog. Only then will consumers be guided by accurate information about how much a product actually costs them. Such information generally improves the results of reliance on market mechanisms.

Fifth, agencies should discourage practices that hide the existence or severity of environmental health problems. Storage of nuclear wastes underground so that the continuing health hazard is not noticed and the war on cancer that lulls people into thinking a cure is near lead the public to underestimate its jeopardy. This should be avoided in part because an informed public is central to addressing problems of pollution. In the absence of an objective formula for balancing alleged benefits against alleged harms to determine the acceptability of pollution, an informed public must be the ultimate judge of government decisions related to environmental health.

peter s. wenz (1995)

revised by jessica pierce

SEE ALSO: Environmental Ethics; Environmental Policy and Law; Future Generations, Reproductive Technologies and Obligations to; Hazardous Wastes and Toxic Substances; Occupational Safety and Health; Public Health; Sustainable Development

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Environmental health

Environmental health is concerned with the medical effects of chemicals , pathogenic (disease-causing) organisms, or physical factors in our environment . Because our environment affects nearly every aspect of our lives in some way or other, environmental health is related to virtually every branch of medical science. The special focus of this discipline, however, tends to be health effects of polluted air and water, contaminated food, and toxic or hazardous materials in our environment. Concerns about these issues makes environmental health one of the most compelling reasons to be interested in environmental science .

For a majority of humans, the most immediate environmental health threat has always been pathogenic organisms. Improved sanitation , nutrition, and modern medicine in the industrialized countries have reduced or eliminated many of the communicable diseases that once threatened us. But for people in the less developed countries where nearly 80% of the world's population lives, bacteria, viruses, fungi , parasites , worms, flukes, and other infectious agents remain major causes of illness and death. Hundreds of millions of people suffer from major diseases such as malaria , gastrointestinal infections (diarrhea, dysentery, cholera ), tuberculosis, influenza, and pneumonia spread through the air, water, or food. Many of these terrible diseases could be eliminated or greatly reduced by a cleaner environment, inexpensive dietary supplements, and better medical care.

For the billion or so richest people in the world—including most of the population of the United States and Canada—diseases related to lifestyle or longevity tend to be much greater threats than more conventional environmental concerns such as dirty water or polluted air. Heart attacks, strokes, cancer , depression and hypertension, traffic accidents, trauma, and AIDS lead as causes of sickness and death in wealthy countries. These diseases are becoming increasingly common in the developing world as people live longer, exercise less, eat a richer diet, and use more drugs, tobacco , and alcohol. Epidemiologists predict that by the middle of the next century, these diseases of affluence will be leading causes of sickness and death everywhere.

Although a relatively minor cause of illness compared to the factors above, toxic or hazardous synthetic chemicals in the environment are becoming an increasing source of concern as industry uses more and more exotic materials to manufacture the goods we all purchase. There are many of these compounds to worry about. Somewhere around five million different chemical substances are known, about 100,000 are used in commercial quantities, and about 10,000 new ones are discovered or invented each year. Few of these materials have been thoroughly tested for toxicity. Furthermore, the process of predicting what our chances of exposure and potential harm might be from those re-leased into the environment remains highly controversial. Toxins are poisonous, which means that they react specifically with cellular components or interfere with unique physiological processes. A particular chemical may be toxic to one organism but not another, or dangerous in one type of exposure but not others. Because of this specificity, they may be harmful even in very dilute concentrations. Ricin, for instance, is a protein found in castor beans and one of the most toxic materials known. Three hundred picograms (trillionths of a gram) injected intravenously is enough to kill an average mouse. A single molecule can kill an individual cell. If humans were as sensitive as mice, a few teaspoons of this compound, divided evenly and distributed uniformly could kill everyone in the world. By the way, this points out that not all toxins are produced by industry. Many natural products are highly toxic.

Toxins that have chronic (long-lasting) or irreversible effects are of special concern. Among some important examples are neurotoxins (attack nerve cells), mutagens (cause genetic damage), teratogens (result in birth defects ), and carcinogens (cause cancer). Many pesticides and metals such as mercury , lead , and chromium are neurotoxins. Loss of even a few critical neurons can be highly noticeable or may even be lethal making this category of great importance. Chemicals or physical factors such as radiation that damage genetic material can harm not only cells produced in the exposed individual, but also the offspring of those individuals as well.

Among the most dread characteristics of all these chronic environmental health threats are that the initial exposure may be so small or have results so unnoticeable that the victim doesn't even know that anything has happened until years later. Furthermore the results may be catastrophic and irreversible once they do appear. These are among our worst fears and are powerful reasons that we are so apprehensive about environmental contaminants. There may be no exposure—no matter how small—of some chemicals that is absolutely safe. Because of these fears, we often demand absolute protection from some of the most dread contaminants. Unfortunately, this may not be possible. There may be no way to insure that we are never exposed to any amount of some hazards. It may be that our only recourse is to ask how we can reduce our exposure or mitigate the consequences of that exposure.

In spite of the foregoing discussion of the dangers of chronic effects from minute exposures to certain materials or factors, not all pollutants are equally dangerous nor is every exposure an unacceptable risk. Our fear of unknown and unfamiliar industrial chemicals can lead to hysterical demands for zero exposure to risks. The fact is that life is risky. Furthermore, some materials are extremely toxic while others are only moderately or even slightly so.

This is expressed in the adage of the German physician, Paracelsus, who said in 1540 that "The dose makes the poison." It has become a basic principle of toxicology that nearly everything is toxic at some concentration but most materials have some lower level at which they present an insignificant risk. Sodium chloride (table salt), for instance, is essential for human life in small doses. If you were forced to eat a kilogram all at once, however, it would make you very sick. A similar amount injected all at once into your blood stream would be lethal.

How a material is delivered—at what rate, through which route of entry, in what form—is often as important as what the material is. The movement, distribution, and fate of materials in the environment are important aspects of environmental health. Solubility is one of the most important characteristics in determining how, when, and where a material will travel through the environment and into our bodies. Chemicals that are water soluble move more rapidly and extensively but also are easier to wash off, excrete, or eliminate. Oil or fat soluble chemicals may not move through the environment as easily as water-soluble materials but may penetrate very efficiently through the skin and into tissues and organs. They also may be more likely to be concentrated and stored permanently in fat deposits in the body.

The most common route of entry into the body for many materials is through ingestion and absorption in the gastrointestinal (GI) tract. The GI tract, along with the urinary system are the main routes of excretion of dangerous materials. Not surprisingly, those cells and tissues most intimately and continuously in contact with dangerous materials are among the ones most likely to be damaged. Ulcers, infections, lesions, or tumors of the mouth, esophagus, stomach, intestine, colon, kidney, bladder, and associated glands are among the most common manifestations of environmental toxins. Other common routes of entry for toxins are through the respiratory system and the skin. These also are important routes for excreting or discharging unwanted materials.

Some of our most convincing evidence about the toxicity of particular chemicals on humans has come from experiments in which volunteers (students, convicts, or others) were deliberately given measured levels under controlled conditions. Because it is now considered unethical to experiment on living humans, we are forced to depend on proxy experiments using computer models, tissue cultures, or laboratory animals. These proxy tests are difficult to interpret. We can't be sure that experimental methods can be extrapolated to how real living humans would react. The most commonly used laboratory animals in toxicity tests are rodents like rats and mice. However, different species can react very differently to the same compound. Of some 200 chemicals shown to be carcinogenic in either rats or mice, for instance, about half caused cancer in one species but not the other. How should we interpret these results? Should we assume that we are as sensitive as the most susceptible animal, as resistant as the least sensitive, or somewhere in between?

It is especially difficult to determine responses to very low levels of particular chemicals, especially when they are not highly toxic. The effects of random events, chance, and unknown complicating factors become troublesome, often resulting in a high level of uncertainty in predicting risk. The case of the sweetener saccharin is a good example of the complexities and uncertainties in risk assessment . Studies in the 1970s suggested a link between saccharin and bladder cancer in male rats. Critics pointed out that humans would have to drink 800 cans of soft drink per day to get a dose equivalent to that given to the rats. Furthermore, they argued, most people are not merely large rats.

The Food and Drug Administration uses a range of estimates of the probable toxicity of saccharine in humans. At current rates of consumption, the lower estimate predicts that only one person in the United states will get cancer every 1,000 years from saccharine. That is clearly inconsequential considering the advantages of reduced weight, fewer cases of diabetes, and other benefits from this sugar substitute. The upper estimate, however, suggests that 3,640 people will die each year from this same exposure. That is most certainly a risk worth worrying about.

An emerging environmental health concern with a similarly high level of uncertainty but potentially dire consequences is the disruption of endocrine hormone functions by synthetic chemicals. About ten years ago, wildlife biologists began to report puzzling evidence of reproductive failures and abnormal development in certain wild animal populations. Alligators in a lake in central Florida, for instance, were reported to have a 90% decline in egg hatching and juvenile survival along with feminization of adult males including abnormally small penises and lack of sperm production. Similar reproductive problems and developmental defects were reported for trout in the Great Lakes , seagulls in California, panthers in Florida, and a number of other species. Even humans may be effected if reports of global reduction of sperm counts and increases of hormone-dependent cancers prove to be true.

Both laboratory and field studies point to a possible role of synthetic chemicals in these problems. More than 50 chemicals, if present in high enough concentrations, are now known to mimic or disrupt the signals conveyed by naturally occurring endocrine hormones that control almost every aspect of development, behavior, immune functions, and metabolism . Among these chemicals are dioxin , polychlorinated biphenyl, and several persistent pesticides. This new field of research promises to be of great concern in the next few years because it combines dread factors of great emotional power such as undetectable exposure, threat to future generations , unknown or delayed consequences, and involuntary or inequitable distribution of risk.

In spite of the seriousness of the concerns expressed above, the Environmental Protection Agency warns that we need to take a balanced view of environmental health. The risks associated with allowable levels of certain organic solvents in drinking water or some pesticides in food are thought to carry a risk of less than one cancer in a million people in a lifetime. Many people are outraged about being exposed to this risk, yet they cheerfully accept risks thousands of times as higher from activities they enjoy such as smoking, driving a car, or eating an unhealthy diet. According to the EPA, the most important things we as individuals can do to improve our health are to reduce smoking, drive safely, eat a balanced diet, exercise reasonably, lower stress in our lives, avoid dangerous jobs, lower indoor pollutants, practice safe sex, avoid sun exposure, and prevent household accidents. Many of these factors over which we have control are much more risky than the unknown, uncontrollable, environmental hazards we fear so much.

[William P. Cunningham Ph.D. ]

RESOURCES

BOOKS

Foster, H. D. Health, Disease and the Environment. Boca Raton: CRC Press, 1992.

Moeller, D. W. Environmental Health. Cambridge: Harvard University Press, 1992.

Morgan, M. T. Environmental Health. Madison: Brown & Benchmark, 1993.

PERIODICALS

Hall, J. V., et al. "Valuing the Health Benefits of Clean Air." Science 255 (February 14, 1991): 812–17.

ENVIRONMENTAL HEALTH

The word environment as applied to health is elastic in use. Conventionally it refers to the external factors–physical, chemical, and microbiological–that impinge on human health, usually through shared exposures among members of communities or whole populations, and that therefore are not under the control of individuals. A broader definition embraces the social environment, including the aspects of social capital that influence health within the community at large. Indeed, in the early twenty-first century about half of all people live in urban environments as Homo sapiens becomes an urbanized species. The urban environment is essentially a habitat: a system of interacting physical, demographic, social, and cultural environments. These wider dimensions of the environment necessitate a more ecological, systems-based approach.

External environmental exposures can be either natural or human-made and have a local, regional, or global scale. The modern preoccupation is with human-made environmental hazards. Historically, however, concerns focused on aspects of the natural environment, including weather extremes, infectious agents, physical disasters, and local micronutrient deficiencies. For example, one-fifth of the world population lives on ancient, leached, and often mountainous iodine-deficient soils. This puts many populations at risk of iodine deficiency disorders, including goiter, reproductive impairment, and congenital disorders, including cretinism (Hetzel and Pandav 1994).

The environmental health agenda also must encompass the risks to population health that result from humankind's larger-scale disruption of the planet's ecological and geophysical systems. These are the systems that provide nature's "goods and services": climatic stability, food yields, the supply of clean fresh water, and the healthy functioning of biotically diverse natural ecosystems that recycle nutrients, cleanse the air and water, and produce useful materials. This disruption or depletion of the biosphere's life support systems can affect health through pathways that are less direct and sometimes less immediate than the effects of specific traditional hazards.

In industrialized countries attention has been directed predominantly to the plethora of chemical contaminants entering air, water, soil, and food, along with physical hazards such as ionizing radiation, nonionizing radiation, urban noise, and road trauma. In the popular understanding prototypical environmental health events include the disasters of Chernobyl, Bhopal, Seveso, Minamata Bay, and the Great London Smog of 1952. As technologies evolve and as levels of consumption rise, the list of candidate hazards lengthens: In the late 1990s questions arose about the cancer hazard of electromagnetic radiation from mobile phones, the risk to a fetus from chlorinated organic chemicals in chlorine-treated water supplies, and the possible toxicity and allergenic and other consequences of genetically modified foods. In low-income countries the major environmental concerns continue to be the microbiological quality of drinking water and food, the physical safety of housing and work sites, indoor air pollution, and traffic hazards.

The relative importance of environmental exposures as a cause of human disease and premature death remains a matter of contention. Depending on definitions and assumptions, estimates of the environmental contribution to the global burden of disease and premature death vary. The World Health Organization has estimated that about 25 percent of the global burden, as measured in disability-adjusted life years (DALYs), is caused by environmental hazards, along with around one-sixth of the total burden in children. Kirk Smith and colleagues (1999), in an analysis that encompassed disease initiation, progression, and case outcome, estimated that 25 to 33 percent of the global burden of disease and premature death is attributable to direct environmental risk factors.

Relationships between Environment, Population, Poverty, and Health

The relationships among ambient environmental conditions, socioeconomic circumstances, demographic change, and human health are complex and multidirectional. Some of the relationships are immediate; for example, poverty today causes malnutrition today. Other relationships involve long time lags; for example, current poverty contributes to the need to clear local forests for fuel and to farm marginal lands, inducing ecological attrition and hunger in the future. Time lags aside, there is not a simple linear causal chain connecting these variables. Population pressure and poverty in rural populations often lead to land degradation, with consequences for supplies of food and materials. Meanwhile, poverty influences fertility rates, and vice versa. Environmental degradation often causes further impoverishment and also may impair health through increases in infectious disease, nutritional deficiencies, and toxic environmental exposures.

In many African, Asian, and Latin American countries life expectancy is 20 to 30 years less than it is in rich Western countries. Infectious diseases remain the main killer, particularly of children below five years of age. Much of this health deficit reflects the widespread poverty, adverse social consequences of export-oriented economic development, and environmental adversity caused by the exploitation of natural resources.

Some larger-scale environmental stresses may heighten social tensions, leading to conflict and adverse health consequences. For example, Ethiopia and the Sudan, upstream of Egypt, increasingly need the Nile's water for their crops. Worldwide, approximately 40 percent of the world's population, living in 80 countries, now faces some degree of water shortage. The prospect of international conflict caused by environmental decline, dwindling resources, and ecological disruption enlarges the shadow over the prospects for human health.

It is difficult to confirm or refute the widely assumed linkage between poverty, environment, and health. Both poverty and environmental degradation, through independent pathways, increase risks to health. There is also a strong but complex relationship between income level and environmental quality. For many important environmental pollutants, as average incomes rise, the effect on environmental quality can be represented by an inverted Ushaped curve. Initially the pollutant loads increase; then, as wealth, literacy, and political liberalism increase, negative feedback processes emerge and societies act to reduce those pollutants. However, the indexes of several larger-scale sources of environmental degradation, such as emissions of the greenhouse gas carbon dioxide, display a continuing increase. These are "global commons" problems for which there is not yet sufficiently clear evidence of adverse social, economic, or health consequences to generate negative feedback responses through the policy process. Humankind has not yet learned how to mitigate, with international cooperation, these large-scale threats.

Conclusion

Throughout history human communities have depleted natural resources and degraded local ecosystems. Often the consequences have been a recession in local human numbers and impairment of nutrition, health, and social viability. Demographers have long debated the classic Malthusian problem in which local population needs exceed the local environmental carrying capacity. In the early twenty-first century that postulated process of ecological deficit budgeting has become global, an unprecedented development for humankind with significant implications for human population health.

For the last two centuries environmental health concerns in the industrializing world have focused mainly on toxicological or, less often, microbiological risks to health from specific agents in the local environment. In low-income countries the traditional hazards from infectious agents in air, food, and water, along with malnutrition and the physical hazards of living environments, have predominated. The escalating impact of human numbers and economic activity has begun to alter some of the major global biophysical systems that underpin the health of humans and all other species. Humankind is at risk of incurring global ecological deficits as, increasingly, people live beyond the planet's overall environmental carrying capacity.

See also: Climate Change and Population: Future; Disease and History.

bibliography

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Grossman, G. 1995. "Pollution and Growth: What Do We Know?" In The Economics of Sustainable Development, eds. I. Goldin, and L. A. Winters. Cambridge, Eng.: Cambridge University Press.

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World Health Organization. 1997. Health and Environment in Sustainable Development: Five Years after the Earth Summit. Geneva: World Health Organization.

A. J. McMichael

Environmental Health

Environmental health describes the effects of civilization, culture, personal habits, pollution, population growth, and travel on human health. It is a new science that measures a variety of factors leading to acquired and congenital diseases. Acquired diseases are illnesses people get from exposure to harmful chemicals, injurious activities, and pathogenic organisms. Congenital diseases are caused by genetic defects or factors that harm fetal development.

Throughout history people have witnessed the increase in human disease with the growth of agriculture and cities. It was not until the late nineteenth century that people had scientific explanations for the cause of the diseases. Urban growth and overpopulation are associated with higher incidences of communicable diseases spread by insects, rats, and humans. Agriculture also resulted in a host of new human diseases. A variety of diseases, such as influenza, measles, and smallpox, may have been developed from diseases originally found in agricultural animals.

In the past twenty years, plastics have become the most popular material for manufacturing a variety of products including automobiles, household goods, and medical devices. Plastics have replaced many traditional uses of glass, metal, and wood. They have permitted the development of fuel-efficient automobiles, lightweight airplanes, durable furniture, and safer food containers. With all these benefits comes a high environmental cost. Many scientists are discovering that many plastics leak pollutants capable of altering the body's endocrine system, which is responsible for body maintenance, growth, and reproduction.

The role of pollution and health was not well known to the public until the publication of Silent Spring, written by Rachel Carson in 1962. She alerted people to the health effects of pesticides and other pollutants on humans and wildlife. Many scientists supported her views, and this resulted in the formation of the Environmental Protection Agency by the U.S. government in 1970. The National Institutes of Health was later set up to look at other environmental health issues. This agency focuses on illnesses associated with household and work environments. In 1948 the World Health Organization was formed by the United Nations to deal with international environmental health problems.

Occupational health and wellness includes health issues related to the work environment. Some issues include injuries due to certain activities or illness due to handling certain chemicals. Ergonomics is a field of study that has linked conditions such as carpal tunnel syndrome to repetitive hand actions such as continuous typing on a keyboard or handling automobile parts on an assembly line.

Mental health is also a concern of public health agencies working in environmental health. Abuse, poverty, violence, and stressful work environments are associated with mental illnesses. Public health agencies seek ways of changing the social environment in attempts to reduce mental disease.

Today, scientists are continuously conducting research linking environmental factors to human illness. There are two types of environmental health research: experimental research and epidemiological research.

Environmental health experiments involve laboratory and field tests that show how an environmental factor can cause a particular disease. For example, animal experiments are showing that many types of water pollution will cause birth defects, cancer, and reproductive disorders. Epidemiological research techniques involve collecting data associating a particular illness to a certain activity or environmental factor. The data are gathered through surveys, public medical records, and field studies. Air pollution has been linked to increases in asthma and emphysema in epidemiology human studies. This was determined by comparing high rates of asthma and emphysema to increased levels of air pollution in an area.

Laws prohibiting smoking in many public areas are recent examples of government policy based on environmental health research. Food safety regulations controlling the amount of pesticides in foods are another example. The Environmental Protection Agency set laws that limit pollution to levels that do not cause illness to humans and wildlife.

see also Carson, Rachel; Disease; Epidemiologist

Brian R. Shmaefsky

Bibliography

Miller, Tyler. Environmental Science, Sustaining the Earth, 4th ed. Belmont, CA: Wadsworth Publishing Company.

U.S. Environmental Protection Agency. <www.epa.gov>.

U.S. National Institutes of Health. <www.nih.gov>.

World Health Organization. <www.who.int>.