Drinking Water—Safety on Tap
Drinking Water—Safety on Tap
Drinking Water—Safety on Tap
HOW MUCH WATER DO AMERICANS USE?
In the American Water Works Association's benchmark study, Residential End Uses of Water Study (1999, http://www.awwarf.org/research/topicsandprojects/exec Sum/241.aspx), Peter W. Mayer et al. report the results of their study on residential end uses of water in twelve hundred single-family homes in twelve North American locations from 1996 to 1998. Mayer et al. reveal that, on average, Americans on community water supplies use about one hundred gallons of water per person per day. People with private wells use slightly less. About sixty-nine gallons per day are used indoors and the rest is used outdoors. According to the University of North Carolina at Chapel Hill, in "Beverage Intake in the United States" (May 5, 2006, http://www.cpc.unc.edu/projects/beverage/beverage_home.html), of this daily supply, only a small portion—slightly more than one-third of a gallon—is consumed as drinking water.
Residential water consumers use most water for purposes other than drinking, such as toilet flushing, bathing, cooking, and cleaning. In the United States significant amounts of water are used for kitchen and laundry appliances, such as garbage disposals, clothes washers, and automatic dishwashers; for automobile washing; and for lawn and garden watering. Additional community use includes firefighting, fountains, public swimming pools, and watering of public parks and landscaping.
DRINKING WATER SOURCES
The two primary sources of drinking water are surface freshwater and groundwater. In 2000 more than half (63%; 27.3 billion gallons per day [Bgal/d] of 43.3 Bgal/d) of public-supply water withdrawals were from surface water sources (e.g., lakes, rivers, and reservoirs). (See Table 2.3 in Chapter 2.) The remaining water withdrawals (37%; 16 Bgal/d) were supplied with water that came from groundwater stored in aquifers. Aquifers are underground geologic formations that consist of layers of sand and porous rock that are saturated with water. Aquifer water is obtained from wells and springs. The only other source of drinking water is desalinated seawater, which is used in only a few locations around the world and provides little of the total amount of drinking water worldwide.
PUBLIC AND PRIVATE WATER SUPPLIES
As described in Chapter 2, public-supply water use is water withdrawn by public and private water suppliers (utility companies) and delivered for public uses: domestic, commercial, industrial, and thermoelectric power uses. It may be used for public services such as filling public pools, watering vegetation in parks, supplying public buildings, firefighting, and street washing. The latest data available from the U.S. Geological Survey show that 43.3 Bgal/d were supplied to users in 2000 by water utility companies (public supply). (See Table 2.2 in Chapter 2.) The rest of the water was self-supplied—that is, the water was withdrawn from groundwater or surface water sources by the users, not by water utility companies.
Public-supply water systems (which can be publicly or privately owned) have at least fifteen service connections or serve at least twenty-five people per day for sixty days of the year. According to the U.S. Environmental Protection Agency (EPA) report Factoids: Drinking Water and Ground Water Statistics for 2005 (December 2006, http://www.epa.gov/ogwdw/data/pdfs/statistics_data_factoids_2005.pdf), there were 156,582 of these systems of varying size in the United States in 2005. (See Table 5.1.) The amount and type of treatment provided varies with source and quality. For example, some public systems using a groundwater source require no treatment, whereas others may need to disinfect the water or apply additional treatment.
|Types of public water systems, by water source and population served, 2005|
|Water source||Systems||Population served||Percent of systems||Percent of population|
|Source: Adapted from "Water Source," in Factoids: Drinking Water and Ground Water Statistics for 2005, U.S. Environmental Protection Agency, Office of Water, December 2006, http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf (accessed January 8, 2007)|
|Community water systems|
|Nontransient noncommunity water systems|
|Transient noncommunity water systems|
There are three types of public water systems. Figure 5.1 shows a flowchart of drinking water systems, including public water systems. Table 5.1 displays their similarities and differences. Community water systems are those that supply water to the same population year-round. Most people in the United States are served by community water systems. In 2005 there were 51,755 community water systems serving 280.7 million (94%) out of 298.8 million people in the United States. Of these systems, 40,018 (77%) accessed groundwater for their water supply. Nevertheless, they served only 89.5 million (32%) of the community water system population. In 2005, 191.1 million (68%) of that population was served by 11,737 community water systems (23%) that access surface water for their water supply.
Nontransient noncommunity water systems are the second type of public water system. They serve the public but not the same people year-round. Examples of nontransient noncommunity systems are schools, factories, office buildings, hospitals, and other public accommodations. In 2005 there were 19,045 nontransient non-community water systems in the United States serving 6 million people, or 2% of the total U.S. population. (See Table 5.1.) Of these systems, 18,438 (97%) accessed groundwater for their water supply.
Transient noncommunity water systems are the third type of public water system. These are systems that provide water in places such as gas stations or campgrounds, where people do not remain for long periods of time. In 2005 there were 85,782 transient noncommunity water systems serving 12.1 million people, or 4% of the total U.S. population. (See Table 5.1.) Ninety-eight percent (83,930) of transient noncommunity water systems accessed groundwater for their water supply.
The EPA and state health and environment departments regulate public water supplies. Public suppliers are required to ensure that the water meets certain government-defined health standards under the Safe Drinking Water Act (SDWA). This law mandates that all public suppliers test their water regularly to check for the existence of contaminants and treat their water supplies, if necessary, to take out or reduce certain pollutants to levels that will not harm human health.
The EPA notes in Factoids that more water systems have groundwater than surface water as a source, but more people drink from a surface water system.
Table 5.2 shows that 149,182 (or 94%) of public water systems were small or very small in 2005, each serving fewer than 3,300 people. (See Table 5.2.) The remaining systems (9,039, or 6%) were comparatively few in number but serviced many more people. The medium-sized systems each provide water to between 3,301 and 10,000 people. The large and very large systems provide water to more than ten thousand people each. Together, the medium, large, and very large public water services provided water for the vast majority of people who drank water from a public supply in the United States in 2005: 261.8 million people.
Private Water Systems
According to the EPA, in Drinking Water from Household Wells (January 2002, http://www.epa.gov/safewater/privatewells/pdfs/household_wells.pdf), 15% of Americans obtain their water from private wells, cisterns, and springs. System owners are solely responsible for the quality of the water provided from these sources.
Personal private water supplies, usually wells, are not regulated under the SDWA. Many states, however, have programs designed to help well owners protect their own water supplies. Usually, these state-run programs are not regulatory, but provide safety information. In addition, the EPA is a source of information. This type of information is vital because private wells are often shallower than those used by public suppliers. The more shallow the well, the greater the potential for contamination.
CONTAMINANTS IN DRINKING WATER
Water can dissolve many substances. Pure water rarely occurs in nature, because both surface and groundwater dissolve minerals and other substances in the soil and deposited from the atmosphere. At low levels dissolved contaminants generally are not harmful in drinking water. Removing all contaminants would be extremely expensive and might not provide greater protection of health. The concentration of harmful substances in water is the main determinant in whether the water is safe to drink.
Contaminants in drinking water are grouped into two broad categories: chemical and microbial. Both chemical and microbial contaminants may be naturally occurring or may be caused by human activity. Chemical contaminants include metals, pesticides, synthetic chemical compounds, suspended solids, and other substances. Microbial contaminants include bacteria, viruses, and microscopic parasites. A rather thorough list of drinking water contaminants, their sources, and their potential health effects is shown in Table 4.1 in Chapter 4.
The health effects of drinking contaminated water can occur either over a short or long period. Short-term, or acute, reactions are those that occur within a few hours or days after drinking contaminated water. Acute reactions may be caused by a chemical or microbial contaminant. Long-term, or chronic, effects occur after water with relatively low doses of a pollutant has been consumed for several years or over a lifetime. Most chronic effects are caused by chemical contaminants.
The ability to detect contaminants improved considerably in the late twentieth century. Scientists can now identify specific chemical pollutants in terms of one part contaminant in one billion parts of water. In some cases scientists can measure them in parts per trillion. One part per billion (ppb) is equal to one pound in five hundred thousand tons. Although these measurements appear tiny, such small amounts can be significant in terms of health effects.
|Public water system, by size and population served, 2005|
|Very small 500 or less||Small 501-3,300||Medium 3,301-10,000||Large 10,001-100,000||Very large >100,000||Total|
|CWS = Community water system: A public water system that supplies water to the same population year-round.|
|NTNCWS = Nontransient noncommunity water system: A public water system that regularly supplies water to at least 25 of the same people at least six months per year, but not year-round. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.|
|TNCWS = Transient noncommunity water system: A public water system that provides water in a place such as a gas station or campground where people do not remain for long periods of time.|
|Source: "System Size by Population Served," in Factoids: Drinking Water and Ground Water Statistics for 2005, U.S. Environmental Protection Agency, Office of Water, December 2006, http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf (accessed January 8, 2007)|
|% of systems||56%||27%||9%||7%||1%||100%|
|% of population||2%||7%||10%||36%||45%||100%|
|% of systems||85%||14%||1%||0%||0%||100%|
|% of population||38%||45%||9%||8%||0%||100%|
|% of systems||97%||3%||0%||0%||0%||100%|
|% of population||52%||19%||4%||4%||21%||100%|
|Total # systems||129,365||19,817||4,961||3,688||390||158,221|
All drinking water contains minerals dissolved from the earth. In small amounts some of these minerals are acceptable because they often enhance the quality of the water (e.g., giving it a pleasant taste). A few minerals in small amounts, such as zinc and selenium, contribute to good health. Other naturally occurring minerals are not desirable because they may cause a bad taste or odor (such as excessive amounts of iron, manganese, or sulfur) or because they may be harmful to health (such as boron).
A wide variety of contaminants may cause serious health risks in water supplies. Not all contaminants are found in all water supplies; furthermore, some water supplies have no undesirable contaminants and some supplies have no contaminants that have health significance. Contaminant presence is frequently the result of human activity and may have long-term consequences. Even though harmful levels of microorganisms generally make their presence known quickly by causing illness with fairly obvious symptoms, the effects of some toxic chemicals may not be apparent for months or even years after exposure. Some chemical pollutants are known carcinogens (cancer-causing agents), whereas others are suspected of causing birth defects, miscarriages, and heart disease. In many cases the effects occur only after long-term exposure.
Arsenic is a naturally occurring element in rocks and soils and is soluble in water. Arsenic has been recognized as a poison for centuries. Recent research, however, shows that humans need arsenic in their diet as a trace element. However, Paolo Boffetta and Fredrik Nyberg report in "Contribution of Environmental Factors to Cancer Risk" (British Medical Bulletin, 2003) that too much arsenic can contribute to skin, bladder, and lung cancers after prolonged exposure. Because of this risk, the current maximum contaminant level (MCL) for arsenic in drinking water is ten ppb.
LEAD AND COPPER
Lead is a toxic metal that can cause serious health problems if ingested. Children are particularly at risk because their developing bodies absorb and retain more lead than adult bodies. Low-level exposures can result in a lowered intelligence quotient (IQ), impaired learning and language skills, loss of hearing, reduced attention spans, and poor school performance. High levels damage the brain and central nervous system, interfering with both learning and physical development. Pregnant women are also at risk. Lead can cause miscarriages, premature births, and impaired fetal development.
Unlike many water contaminants, lead has been extensively studied for its prevalence and effects on human health and for ways to eliminate it from the water supply. Lead is rarely found in either surface water or groundwater sources for drinking. This contaminant usually enters the water supply after it leaves the treatment plant or the well.
The major sources of lead exposure are deteriorated lead paint in older houses and dust and soil that are contaminated by old paint and past emissions of leaded gasoline. Plumbing in older buildings has also contributed to overall blood lead levels. Until about 1930 many buildings in the United States had lead pipes in their interior plumbing and for the service connections that linked buildings to the public water supplies. In addition, lead solder was commonly used to connect pipes. There is little lead piping in use any more within buildings, but some lead service piping still exists in one-hundred-year-old inner-city neighborhoods.
Copper pipes replaced lead in most buildings, but the practice of using lead solder to join the pipes continued. The corrosion of lead solder is believed to be the primary cause of most lead in residential water supplies today. Low pH (acidity), low calcium or magnesium levels in the water, and dissolved oxygen can all contribute to corrosion of lead solder. The common practice of grounding electrical equipment to water pipes also accelerates corrosion.
Most commonly, copper pipes are used to supply water from the street to a building, and to supply water to various parts of the building's interior. Although copper is a dependable material, it can be corroded by acidic water.
In June 1991 the EPA (August 24, 2006, http://www.epa.gov/safewater/lcrmr/index.html) established a regulation called the Lead and Copper Rule (LCR) to help control lead and copper in drinking water. The rule requires community and nontransient noncommunity water systems to monitor drinking water at customer taps. If lead concentrations exceed 15 ppb or copper concentrations exceed 1.3 parts per million (ppm) in more than 10% of the customer taps sampled, then action must be taken to control corrosion and possibly replace lead service lines. If lead levels are exceeded, then the public must be informed about how to protect themselves against lead poisoning.
The EPA (July 18, 2006, http://www.epa.gov/fedrgstr/EPA-WATER/2006/July/Day-18/w6250.pdf) proposed changes to the LCR in 2006 that focused on enhancing monitoring, treatment, customer awareness, and lead service line replacement. The changes will also help ensure that drinking water consumers receive meaningful, timely, and useful information to help them limit their exposure to lead in drinking water.
Nitrates are plant nutrients that enter both surface and groundwater primarily from fertilizer runoff, human sewage, and livestock manure, especially from feedlots. Nitrates in drinking water can be an immediate threat to children under six months of age. In some babies high levels of nitrates react with the red blood cells to reduce the blood's ability to transport oxygen.
The MCL for nitrates is set at ten ppm. When nitrate levels exceed this limit, a water supplier must notify the public and provide additional treatment to reduce levels to meet the standards. The number of community water systems with MCL violations for nitrates declined between 1980 and 1998. The highest number of systems in violation was registered in 1985, with 340 community water systems having levels over the limit.
In Factoids, the EPA reports that 943 nitrate violations were reported in 540 community and nontransient noncommunity water systems in fiscal year 2005. The number of people served by suppliers cited for nitrate violations in 2005 was 608,472.
Microbes (bacteria, viruses, and protozoa) are found in untreated surface water sources used for drinking water. Groundwater does not contain microbes unless they have been introduced through pollution of the aquifer. Unless the treatment system fails or contaminated water is introduced accidentally into the distribution system, treated drinking water is normally free of microorganisms or they are present in extremely low levels. When a water source or system is contaminated with human or animal fecal waste, some of the microorganisms may be pathogens (disease-causing organisms). The resulting illnesses can have symptoms that include headache, nausea, vomiting, diarrhea, abdominal pain, and dehydration. Although usually not life threatening, these illnesses can be debilitating and uncomfortable for victims. Extended illness or death may occur among young or elderly individuals or those who are immunocompromised (having weakened immune systems). Immunocompromised people include human immunodeficiency virus and acquired immunodeficiency syndrome patients, those receiving treatment for certain kinds of cancer, organ-transplant recipients, and people on drugs that suppress their immune system.
Waterborne pathogens have been the cause of serious diseases throughout the world. In the United States in the early 1900s, the diseases cholera and typhoid fever were commonly associated with drinking water from public supplies. The practice of water treatment was begun to address this problem by reducing the number of pathogens present in water supply systems below an infective dose. The infective dose is the number of a particular microorganism required to induce disease and is different for different microbes. For example, one Cryptosporidium protozoan can induce disease, whereas ten thousand to one hundred thousand Salmonella bacteria are generally necessary for serious illness to occur.
HOW TURBIDITY AFFECTS MICROBIAL CONTAMINATION
Turbidity is a measure of the clarity of water. Turbidity is caused by suspended matter or impurities that make the water look cloudy. These impurities may include clay, silt, fine organic and inorganic matter, and plankton (minute floating aquatic plants and animals).
Figure 5.2 shows the types of activities in a watershed that cause turbidity in a water source. A watershed is the land area that drains water into a river system or other body of water. Figure 5.2 shows that water falls on the land as rain or snow, and that water runs along the ground and eventually seeps into the groundwater or surface water. Human activities such as timber harvests, road building, and residential development compact, pave, and clear the soil of much of its vegetation. During storms, rain runs over this land and erodes it, carrying with it impurities.
Turbidity (excessive cloudiness in water) is unappealing and may represent a health concern in drinking water. It interferes with the effectiveness of disinfection, which is the practice of killing pathogens in water by adding certain chemicals (e.g., chlorine or ozone) or exposing the water to ultraviolet light. Microorganisms can find shelter in the particulate matter, reducing their exposure to disinfectants and ultraviolet light. Although turbidity is not a direct indicator of health risk, many studies show a strong relationship between the removal of turbidity and the removal of pathogens.
Coliform bacteria are a group of closely related, mostly harmless bacteria that live in soil, water, and the intestines of animals. These bacteria are generally divided into two groups: total coliform and fecal coliform. The total coliform group includes all coliform bacteria. The fecal coliform group is a subgroup found in the intestines and fecal waste of warm-blooded animals. There are a few organisms in the fecal coliform group that can be harmful to humans, particularly to children and to immunocompromised people.
The total coliform group is used as a first indicator to assess drinking water quality. This practice began in the early 1900s. It is based on the assumption that because coliform bacteria are always present in sewage from warm-blooded animals (including humans), and pathogens may be present in this same sewage, the presence of coliform bacteria may indicate the potential presence of pathogens. The most common problem caused by fecal pathogens is gastroenteritis, a general illness characterized by diarrhea, nausea, vomiting, and cramps. Even though gastroenteritis is typically not harmful to healthy adults, it can cause serious illness in children and immunocompromised individuals.
Testing the water for each of a wide variety of potential pathogens is difficult and expensive. Testing for total coliform, by comparison, is easy and inexpensive. For this reason, total coliform are used to indicate whether a water system is vulnerable to pathogens. The presence of total coliform in the water distribution system may indicate that the disinfection process is faulty, that a break or leak has occurred in the distribution piping, or that the distribution pipes need to be cleaned. No more than 5% of the drinking water samples collected monthly from a water supplier may be positive for total coliform. All samples that are positive for total coliform are analyzed for the presence of the fecal coliform group or Escherichia coli (E. coli), a specific member of the fecal coliform group, both of which are more sensitive indicators of sewage pollution.
GIARDIA LAMBLIA AND CRYPTOSPORIDIUM
Giardia lamblia and Cryptosporidium are microscopic single-celled protozoa that can infect humans and other warmblooded animals. They are frequently found in surface waters contaminated with animal or human fecal waste. Both organisms have a life stage called a cyst, in which the organism is dormant and protected by an outer shell that allows it to exist outside a host's body for a long time. If cysts are ingested, they can become active and cause an intestinal illness, the symptoms of which are nausea, vomiting, fever, and severe diarrhea. The symptoms last for several days, and a healthy human can generally rid his or her body of the organisms in one or two months. These two organisms are the most frequent cause of waterborne illness in the United States.
The EPA, in "Drinking Water Contaminants" (November 28, 2006, http://www.epa.gov/safewater/contaminants/index.html), indicates that it requires water suppliers using surface water, or groundwater under the direct influence of surface water, to disinfect their water to control Giardia at the 99.9% inactivation and removal level. Groundwater is considered to be under the direct influence of surface water when the geologic formations (usually limestone or fractured bedrock) in which the aquifer lies do not provide adequate natural filtration.
A smaller parasite than Giardia, Cryptosporidium is fifty times more resistant to chlorine (the most commonly used drinking water disinfectant) than Giardia is. Because of its high resistance to chemicals typically used to treat drinking water, it must be physically removed by filtration. The EPA notes in "Drinking Water Contaminants" that as of January 2002 water systems serving ten thousand or more people are required to provide filtration and achieve 99% removal or inactivation of Cryptosporidium. This requirement was applied to water systems serving less than ten thousand people in January 2005.
Cryptosporidium was responsible for what many people view as the nation's worst drinking water disaster. In April 1993 residents of Milwaukee were infected with Cryptosporidium in the city water supply, which had been turbid for several days. For a week, more than eight hundred thousand residents were without drinkable tap water. By the end of the disaster, fifty people had died and over four hundred thousand people had been infected. Besides the human suffering, the disease outbreak cost millions of dollars in lost wages and productivity.
MODERN WATER TREATMENT
Although the Greek physician Hippocrates is credited with emphasizing the importance of clean water for good health as early as 400 BC (he recommended boiling and straining rainwater), the first recorded observation of the connection between drinking water and the spread of disease came from John Snow, a London physician, in 1849. Snow noted that his patients who were getting their drinking water from one particular well were contracting cholera, whereas patients getting drinking water from other wells were not. His solution to the problem was to remove the handle from the contaminated well's pump so that no one could get water, thereby stopping a cholera epidemic. This event is generally credited as the beginning of modern water treatment.
The most significant water treatment event in the United States was the introduction of chlorine as a disinfectant in water supplies. Adding chlorine to water supplies began in the early 1900s. As towns and cities began implementing this practice, epidemics and incidence of typhoid, cholera, and dysentery were dramatically reduced. From this humble beginning evolved the complex drinking water treatment technology that is currently available.
The multiple-barrier approach is the basis for modern water treatment. This approach recognizes that contaminants reach drinking water through many pathways. Working together, water suppliers and health professionals try to erect as many barriers as possible to prevent contaminants from reaching consumers. These barriers include:
- Protecting the water source from contamination by eliminating or limiting waste discharges to the water source through a variety of protection programs
- Improved contaminant detection methods
- New and ongoing research into contaminants and their effects
- Removing contaminants or reducing contaminant levels through various treatments
- Elimination of cross connections and breaks in the distribution lines
- Safe plumbing in residences and businesses
The water treatment process begins with choosing the highest quality groundwater or surface water source available and ensuring its continued protection. (For an annotated illustration of the drinking water treatment process, see Figure 5.3.) Groundwater is usually pumped directly into the treatment plant. In many cases, however, because groundwater is naturally filtered as it seeps through layers of rock and soil, disinfection is the only treatment needed before the water is distributed to consumers.
Surface water is transported to the water treatment plant through aqueducts or pipes. A screen at the intake pipe removes debris such as tree branches and trash.
Water suppliers use a variety of treatments to remove contaminants. These treatments are usually arranged in a sequential series of processes called the treatment train. In the plant the water is aerated to eliminate gases and add oxygen. Chemicals may be added to remove undesirable contaminants or to improve the taste. If the water is hard, lime or soda is added to remove the calcium and magnesium. Hard water can clog pipes, stain fixtures, and interfere with soap lathering.
Coagulation or flocculation is typically the next step. Alum, iron salts, or synthetic polymers are added to the water to combine smaller particles into larger particles (floc) to remove contaminants. In the sedimentation basins, the floc settles to the bottom and is removed. Additional treatment may be required if the raw water shows signs of high levels of toxic chemicals. The water is then sent to sand filtration beds to remove the remaining small particles, clarify the water, and enhance the effectiveness of disinfection. Chlorine, ozone, or ultraviolet light may be used as disinfectants.
At various points in the treatment process, the water is monitored, sampled, and tested using various physical, chemical, and microbial testing procedures. As the water leaves the treatment plant and enters the distribution system, chlorine is added as a disinfectant, particularly where ozone or ultraviolet light are used as disinfectants, to keep it free of microorganisms.
The water then goes to holding units, where it is stored until needed. These may be water towers, which use gravity to bring the water to the consumer without extra energy expense, or ground-level containers that require pumps to move the water. The water that ultimately flows from the tap should be clear, tasteless, and safe to drink.
The most extensively used disinfectant in the United States is chlorine, which is used to kill infectious microorganisms and parasites in water. Disinfection with chlorine or other similar chemicals prevents waterborne-disease outbreaks (WBDOs). The practice of chlorination began in the early 1900s to eliminate the cholera and typhoid outbreaks that were widespread in the United States.
In the early 1970s some scientific researchers became concerned by the possible health effects of total trihalomethanes (TTHMs), a byproduct of chlorination. Chlorine reacts with naturally occurring organic substances in water to form TTHMs. The level of TTHMs formed varies widely across water supplies and is dependent on the amount of organic material in drinking water and the amount of chlorine applied. TTHMs are removed by passing the water through activated carbon filters.
The health effects of TTHMs are unclear. Some studies of human populations—such as Paolo Boffetta's "Human Cancer from Environmental Pollutants: The Epidemiological Evidence" (Mutation Research, September 28, 2006)—indicate a slightly higher incidence of bladder, lung, kidney, rectal, and colon cancer in areas where the water is chlorinated. Whereas other studies, such as Will D. King et al.'s "Case-Control Study of Colon and Rectal Cancers and Chlorination By-products in Treated Water" (Cancer Epidemiology Biomarkers and Prevention, 2000), report that an increased cancer risk is inconclusive.
Fluoride, which occurs naturally in combination with other minerals in rocks and soils, is nature's cavity fighter. Water fluoridation is the process of adjusting the naturally occurring level of fluoride in most water systems to a concentration (a range of 0.7 to 1.2 ppm) sufficient to protect against tooth decay. The decision to add fluoride to drinking water is left to each community. If the community elects to use fluoride, the water must meet the EPA maximum concentration limit.
In 1945 Grand Rapids, Michigan, became the first city in the world to add fluoride to its drinking water to prevent tooth decay. Since that time most community water systems in the United States have introduced water fluoridation. Fluoridation of drinking water proved so effective in reducing dental cavities that researchers also developed other methods to deliver fluoride to the public (such as toothpastes, rinses, and dietary supplements). The widespread use of these products has ensured that most people have been exposed to fluoride. The American Dental Association (2007, http://www.ada.org/public/manage/you/working_water.asp) reports that, thanks in large part to community fluoridation, half of all children aged five to seventeen have never had a cavity in their permanent teeth. In "Ten Great Public Health Achievements—United States, 1900–1999" (Morbidity and Mortality Weekly Report, April 2, 1999), the Centers for Disease Control and Prevention (CDC) recognizes fluoridation as one of the ten great public health achievements of the twentieth century.
In Fluoride in Drinking Water: A Scientific Review of EPA's Standards (March 2006, http://dels.nas.edu/dels/rpt_briefs/fluoride_brief_final.pdf), the National Academies of Science presents its most up-to-date research review on fluoridation and its effects on health. The EPA regulates the amount of this chemical permissible in drinking water sources, because—at high levels—fluoride can be detrimental to health. Besides fluoridated water, people can ingest fluoride in non-beverage foods, fluoridated dental products, and certain medications. Additional sources include exposure to this chemical in pesticides, in the air, and in water sources polluted with naturally high concentrations of fluoride. However, most people exposed to harmfully high concentrations of fluoride are athletes or people with certain diseases who drink unusually large quantities of water, people exposed to fluoride in their work, or children who use large amounts of fluoridated tooth paste and swallow it rather than spitting it out.
There are three types of possible detrimental health effects from the consumption of high levels of fluoride: enamel fluorosis, skeletal fluorosis, and bone cancer. Enamel fluorosis, a mild discoloration to severe staining of the teeth, occurs in approximately 10% of children who drink water at or near the allowable fluoride concentration of four milligrams per liter (mg/L). The incidence of this condition is much lower in children who drink water having a fluoride concentration of about two mg/L. Evidence is inconclusive as to whether severe fluorosis of the enamel increases the risk of cavities. Skeletal fluorosis is a bone and joint condition in which increased bone density results in joint pain and stiffness. The incidence of skeletal fluorosis in the United States is rare. Research on the relationship of fluoridated water to bone cancer is inconclusive.
SAFE DRINKING WATER ACT
Federal regulation of drinking water quality began in 1914, when the U.S. Public Health Service established standards for the bacteriological quality of drinking water. The standards applied only to systems that supplied water to interstate carriers such as trains, ships, and buses. The Public Health Service revised these standards in 1925, 1942, and 1962. The 1962 standards, which regulated twenty-eight substances, were adopted by the health departments of all fifty states, even though they were not federally mandated. The Public Health Service continued to be the primary federal agency involved with drinking water until 1974, when the authority was transferred to the EPA via the Safe Drinking Water Act (SDWA), which is the main federal law that ensures the quality of Americans' drinking water. Table 5.3 shows a history of EPA drinking water regulations enacted since 1974.
|EPA drinking water regulations by year enacted, 1974–2006|
|Source: Jennifer L. Liang et al., "Table 1. U.S. Environmental Protection Agency Regulations Regarding Drinking Water, by Year Enacted—United States, 1974–2006," in "Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water Not Intended for Drinking—United States, 2003–2004," Morbidity and Mortality Weekly Report, Surveillance Summaries, vol. 55, no. SS-12, December 22, 2006, http://www.cdc.gov/mmwr/pdf/ss/ss5512.pdf (accessed January 5, 2007)|
|Safe Drinking Water Act (SDWA)||1974|
|Interim Primary Drinking Water Standards||1975|
|National Primary Drinking Water Standards||1985|
|Surface Water Treatment Rule (SWTR)||1989|
|Total Coliform Rule||1989|
|Lead and Copper Regulations||1990|
|Information Collection Rule||1996|
|Interim Enhanced SWTR||1998|
|Disinfectants and Disinfection By-Products (D-DBPs) Regulation||1998|
|Contaminant Candidate List||1998|
|Unregulated Contaminant Monitoring Regulations||1999|
|Ground Water Rule (proposed)||2000|
|Lead and Copper Rule—action levels||2000|
|Filter Backwash Recycling Rule||2001|
|Long Term 1 Enhanced SWTR||2002|
|Unregulated Contaminant Monitoring Regulations||2002|
|Drinking Water Contaminant Candidate List 2||2005|
|Long Term 2 Enhanced SWTR||2006|
|Stage 2 D-DBP Rule||2006|
|Ground Water Rule finalized||2006|
The SDWA mandated that the EPA establish and enforce minimum national drinking water standards for any contaminant that presents a health risk and is known to, or is likely to, occur in public drinking water supplies. For each contaminant that was regulated, the EPA was to set a legal limit on the amount of contaminant allowed in drinking water. In addition, the EPA was directed to develop guidance for water treatment and to establish testing, monitoring, and reporting requirements for water suppliers.
Congress intended that, after the EPA had set regulatory standards, each state would be granted primacy; that is, states would have the primary responsibility for enforcing the requirements of the SDWA. To be given primacy, a state must adopt drinking water standards and conduct monitoring and enforcement programs at least as stringent as those established by the EPA. Forty-nine states and all U.S. commonwealths and territories have received primacy. The EPA implements the drinking water program on Native American reservations. According to the fact sheet "Safe Drinking Water Act 30th Anniversary Drinking Water Monitoring, Compliance, and Enforcement" (June 2004, http://www.epa.gov/ogwdw/sdwa/30th/factsheets/monitoring_compliance.html), the EPA states that Wyoming and the District of Columbia have not received primacy over enforcement of the SDWA.
The EPA established the primary drinking water standards by setting MCLs for contaminants that are known to be detrimental to human health. The contaminants and their MCLs are shown in Table 4.1 in Chapter 4.
All public water systems in the United States are required to meet the primary standards. Only two contaminants regulated thus far, microorganisms and nitrates, pose an immediate health problem when the standards are exceeded. All other contaminants for which standards have been established must be controlled because ingesting water that exceeds these MCLs over a long period may cause long-term health problems, such as cancer, liver, or kidney disease or other harmful effects.
Secondary standards cover aspects of drinking water that have no health risks, such as odor, taste, staining properties, and color. Secondary standards are recommended but not required.
SDWA AMENDMENTS AND REGULATIONS
The EPA is continuing its work to protect drinking water from unsafe contaminant levels, to oversee the activities of the states that enforce federal or their own stricter standards, and to solicit public input as it develops new standards or other program requirements. Over the years the SDWA has been amended to require the EPA to:
- Set a maximum contaminant level goal (MCLG). An MCLG is the maximum amount of a contaminant that is not expected to cause any health problems over a lifetime of exposure. The EPA is mandated to set the MCL as close to the MCLG as technology and economics will permit.
- Specify the "best available technology" for treating each contaminant for which the EPA sets an MCL.
- Provide states with greater flexibility to implement the SDWA to meet their specific needs while arriving at the same level of public health protection.
- Set contaminant regulation priorities based on data about adverse public health effects of the contaminant, the occurrence of the contaminant in public water supplies, and the estimated reduction in health risk that can be expected from any new regulations.
- Provide a thorough analysis of the costs to water supplies and benefits to public health.
- Increase research to develop sound scientific data to provide a base for regulations.
- Ban the use of lead pipes and lead solder in new drinking water systems and in the repair of existing water systems.
- Establish a federal-state partnership for regulation enforcement.
COMPANION LEGISLATION TO THE SDWA
Water Efficiency Act of 1992
The Water Efficiency Act of 1992 established uniform national standards for manufacture of water-efficient plumbing fixtures, such as low-flow toilets and showers. The purpose was to promote water conservation by residential and commercial users.
According to the U.S. General Accounting Office (now the U.S. Government Accountability Office), in Water Infrastructure: Water-Efficient Plumbing Fixtures Reduce Water Consumption and Wastewater Flows (August 2000, http://www.gao.gov/new.items/rc00232.pdf), preliminary results from studies by the American Water Works Association and the EPA indicate that by 2020 water consumption could be reduced by 3% to 9% in the areas studied. Wastewater flows to sewage treatment plants could be reduced 13% by 2016. For the sixteen localities analyzed, the use of water-efficient plumbing fixtures could reduce the local water consumption enough to save local water utilities between $165.7 million and $231.2 million by 2020 because planned investments to expand drinking water treatment or storage capacity could be deferred or avoided.
Federal Water Pollution Control Act
The 1972 Federal Water Pollution Control Act (FWPCA) established the framework for regulating the discharge of pollutants to U.S. waters. This framework was strengthened by amendments in 1977 (the Clean Water Act) and in 1987 (the Water Quality Act).
The FWPCA and its amendments established the National Pollution Discharge Elimination System (NPDES) to reduce discharge of pollutants into water, including drinking water sources. States may apply for and receive primacy for the NPDES program in a manner similar to SDWA primacy.
The FWPCA also requires the EPA and the states to identify water resources that need to be cleaned up to meet water quality standards and to establish stringent controls where needed to achieve the water quality standards. States are required to develop lists of contaminated waters, to identify the sources and amounts of pollutants causing water quality problems, and to develop individual control strategies for the sources of pollution.
Aggressive use of the FWPCA by the EPA and the states can reduce the contaminant loads reaching drinking water sources. Preventing contaminants from reaching drinking water sources protects public health and reduces the need for and cost of water treatment instead of passing the costs on to the water consumer.
COST OF CLEAN DRINKING WATER
From 1976 to 2004 the number of contaminants regulated under the SDWA roughly quadrupled. (See Figure 5.4.) As a result, new treatment technologies have been required. This has significantly increased the cost of water treatment in many locations. More than ninety contaminants are now regulated.
Besides treating water, public water supply systems must:
- Protect their water source
- Build, maintain, and repair the treatment plants and distribution systems
- Replace aging systems
- Recruit, pay, and train system operation staff
- Meet the expanding treatment requirements of the SDWA and its monitoring and reporting requirements
- Expand service areas
- Provide necessary administrative and support services to accomplish these tasks
Most of the money to support these services comes directly from users. The remainder of revenues comes from connection or inspection fees, fines, penalties, and other nonconsumption-based charges, as well as local or state grants or loans. The EPA, in Water on Tap: What You Need to Know (October 2003, http://www.epa.gov/safewater/wot/pdfs/book_waterontap_full.pdf), states that "despite rate increases, water is generally still a bargain compared to other utilities, such as electricity and phone service. In fact, in the United States, combined water and sewer bills average only about 0.5 percent of household income."
HOW CLEAN IS THE WATER?
Safe drinking water is a cornerstone of public health. Drinking water in the United States is generally safe. The vast majority of U.S. residents receive water from systems that have no reported violations of MCLs or flaws in treatment techniques, monitoring, or reporting.
However, in the Natural Resources Defense Council's 3,500-page report Victorian Water Treatment Enters the 21st Century (1994), Brian Cohen and Eric Olson document some 250,000 violations of the SDWA that occurred in 1991 and 1992. Cohen and Olson find that 43% of the water systems (serving about 120 million people) had committed violations.
Even though substantial progress has been made in reducing SDWA violations since this study was issued, the EPA estimates in Factoids that 79.1 million people (out of 282.3 million; see Table 5.2) were supplied with water from community water systems that registered one or more violations for health-based SDWA standards in 2004. (See Table 5.4.) In 2003 there were 81.7 million people affected by systems registering violations; this represents a decrease of 3% from 2003 to 2004.
However, the number of systems experiencing violations rose 4%, from 20,343 in 2003 to 21,200 in 2004. (See Table 5.5.) Furthermore, the number of violations increased 33%, from 88,695 in 2003 to 118,420 in 2004. (See Table 5.6.) The EPA suggests in Factoids that small water systems are more likely to violate regulations than all other sizes. Because of their small size, manpower and funding to maintain and upgrade equipment and to meet monitoring and reporting requirements is extremely limited.
|Community water system violations by population affected, 2001–04|
|Source: Adapted from "CWS Violations Reported by FY, Population Affected," in Factoids: Drinking Water and Ground Water Statistics for 2005, U.S. Environmental Protection Agency, Office of Water, December 2006, http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf (accessed January 8, 2007)|
|Community water system violations by number of systems in violation, 2001–04|
|Number of systems in violation|
|Source: Adapted from "CWS Violations Reported by FY, Number of Systems in Violation," in Factoids: Drinking Water and Ground Water Statistics for 2005, U.S. Environmental Protection Agency, Office of Water, December 2006, http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf (accessed January 8, 2007)|
|Community water system violations by number of violations, 2001–04|
|Number of violations|
|Source: Adapted from "CWS Violations Reported by FY, Number of Violations," in Factoids: Drinking Water and Ground Water Statistics for 2005, U.S. Environmental Protection Agency, Office of Water, December 2006, http://www.epa.gov/safewater/data/pdfs/statistics_data_factoids_2005.pdf (accessed January 8, 2007)|
Disease Caused by Contaminated Drinking Water
It is difficult to know the exact incidence of illness caused by contaminated drinking water. People may not know the source of their illnesses and may attribute them to food poisoning, chronic illness, or infectious agents. Some researchers believe that the actual number of drinking water disease cases is higher than the reported number, but the diseases are not reported because victims believe them to be "stomach upsets" and treat themselves.
Since 1971 the CDC and the EPA have maintained a surveillance system for collecting and reporting data on WBDOs. In "Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water Not Intended for Drinking—United States, 2003–2004" (Morbidity and Mortality Weekly Report, December 22, 2006), Jennifer L. Liang et al. examine CDC data about outbreaks associated with water intended for drinking water and those associated with water used for recreation, such as beaches, hot tubs, and swimming pools.
During the 2003–04 period, eighteen states reported a total of thirty WBDOs in water intended for drinking—twelve in 2003 and eighteen in 2004. (See Figure 5.5.) Liang et al. report that those outbreaks caused an estimated 2,760 people to become ill and led to 4 deaths. As Figure 5.5 shows, five states had the highest number of outbreaks (three each) for the 2003–04 period: New York, New Jersey, Pennsylvania, Ohio, and Florida.
Table 5.7 lists the eleven WBDOs that were traced to contamination at or in the source water, treatment facility, or distribution system. They are listed by etiologic (disease-causing) agent and type of water system. Five of the outbreaks were associated with bacteria, one with parasites, two with chemicals, two with more than one microbe (mixed agents), and one unidentified. The highest percentage of outbreaks was associated with community (36%) and noncommunity (36%) water systems. However, more people were affected (72%) during the one outbreak with a mixed system. Liang et al. report that this mixed system involved noncommunity and individual water systems that both accessed sewage-contaminated groundwater. Cracks in the limestone aquifer allowed bacterial and viral contaminants to flow into the groundwater from the soil above, and people drank this untreated groundwater.
Table 5.8 lists the eight WBDOs that were traced to contamination at or in the source water or treatment facility. They are listed by etiologic agent and water source. Eighty-eight percent of the disease outbreaks and 97% of the cases (people affected) were associated with groundwater. The remainder were associated with surface water.
Figure 5.6 shows that WBDOs occurred year-round between 2003 and 2004 except for February. The number of outbreaks steadily increased during the spring and into July. The number dropped in August and leveled out through the fall, with an increase in November and another increase in January.
The number of WBDOs associated with drinking water in the United States declined from a peak of over fifty outbreaks in 1980. (See Figure 5.7.) Since 1987 there have been fewer than twenty WBDOs each year, except for 1992 and 2000.
Figure 5.8 shows the distribution of outbreaks during the 2003–04 period by disease-causing agents, water system, and water source. Legionella bacteria alone accounted for nearly one out of every four outbreaks (26.7%). (Legionella bacteria are commonly found in bodies of water, including air conditioning cooling towers, sink taps, and showerheads. Some species cause Legionnaires' disease, a pneumonia-like illness that often includes kidney, liver, and gastrointestinal symptoms as well.) All bacteria, including Legionella, were responsible for slightly more than 43% of outbreaks. Chemicals and other toxins accounted for another one-fourth (26.7%) of all outbreaks. Parasites and viruses were each the cause of 3.3% of outbreaks. Most (87.5%) of the outbreaks were linked to groundwater sources. Community and noncommunity water systems each experienced 36.4% of the outbreaks.
ARE AMERICANS CONCERNED ABOUT THEIR DRINKING WATER?
A Gallup poll conducted in 2006 indicates that water purity was one of the most important environmental concerns to Americans. Table 5.9 shows the results of this survey in which pollsters asked Americans to list their greatest environmental concerns along with their level of concern. Their greatest concerns focus on various aspects of water pollution. A majority (54%) had a great
|Number of waterborne-disease outbreaks (WBDOs) associated with drinking water, by causative agent and type water system, 2003–04|
|Etiologic agent||Type of water systema|
|Note: WBDOs with deficiencies 1-4 (i.e., surface water contamination, ground water contamination, water treatment deficiency, and distribution system contamination) were used for analysis.|
|aCommunity and noncommunity water systems are public water systems that have >15 service connections or serve an average of >25 residents for >60 days/year. A community water system serves year-round residents of a community, subdivision, or mobile home park. A noncommunity water system serves an institution, industry, camp, park, hotel, or business and can be nontransient or transient. Nontransient systems serve ≥25 of the same persons for ≥6 months of the year but not year-round (e.g., factories and schools), whereas transient systems provide water to places in which persons do not remain for long periods of time (e.g., restaurants, highway rest stations, and parks). Individual watersystems are small systems not owned or operated by a water utility that have <15 connections or serve <25 persons.|
|bExcludes commercially bottled water, therefore not comparable to previous summaries.|
|cMultiple etiologic agent types (e.g., bacteria, parasite, virus, and/or chemical/toxin) identified.|
|dNoncommunity and individual water systems.|
|Source: Jennifer L. Liang et al., "Table 8. Number of Waterborne-Disease Outbreaks (WBDOs) Associated with Drinking Water (n = 11), by Etiologic Agent and Type of Water System—United States, 2003–2004," in "Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water Not Intended for Drinking—United States, 2003–2004," Morbidity and Mortality Weekly Report, Surveillance Summaries, vol. 55, no. SS-12, December 22, 2006, http://www.cdc.gov/mmwr/pdf/ss/ss5512.pdf (accessed January 5, 2007)|
|C.jejuni and shigella spp.||0||0||0||0||1||57||0||0||1||57|
|C.jejuni, C. lani, Cryptosporidium spp., and helicobacter canadensis||1||82||0||0||0||0||0||0||1||82|
|C.jejuni, norovirus, and G.intestinalis||0||0||0||0||0||0||1d||1,450||1||1,450|
|Number of waterborne-disease outbreaks (WBDOs) associated with drinking water, by causative agent and type of water source, 2003–04|
|[Sample size = 8]|
|Etiologic agent||Water source|
|Ground water||Surface water||Unknown||Mixed source||Total|
|Note: WBDOs with deficiencies 1-3 (i.e., surface water contamination, ground water contamination, and water treatment deficiency) were used for analysis.|
|*Multiple etiologic agent types (e.g., bacteria, parasite, virus, and/or chemical/toxin) identified.|
|Source: Jennifer L. Liang et al., "Table 9. Number of Waterborne-Disease Outbreaks (WBDOs) Associated with Drinking Water (n = eight), by Etiologic Agent and Water Source—United States, 2003–2004," in "Surveillance for Waterborne Disease and Outbreaks Associated with Drinking Water and Water Not Intended for Drinking—United States, 2003–2004," Morbidity and Mortality Weekly Report, Surveillance Summaries, vol. 55, no. SS-12, December 22, 2006, http://www.cdc.gov/mmwr/pdf/ss/ss5512.pdf (accessed January 5, 2007)|
|C. jejuni and shigella spp.||0||0||1||57||0||0||0||0||1||57|
|C. jejuni, norovirus, and giardia intestinalis||1||1,450||0||0||0||0||0||0||1||1,450|
deal of concern about pollution of drinking water and 27% had a fair amount of concern. Thus, 81% were concerned about this issue. Respondents were also concerned about the contamination of the soil and water by toxic waste; pollution of rivers, lakes, and reservoirs; and maintenance of the nation's supply of freshwater for household needs.
Table 5.10 compares respondents' levels of concern regarding the pollution of drinking water with their levels of concern since 1990. Although a majority of Americans were concerned about this issue in 2006, the percentage of those who have a "great deal" of concern has dropped from a high of 72% in 2000. The percentages of those who care a "fair amount," "only a little," and "not at all" have risen since 1990.
Water is called bottled water only if it meets federal and state standards, is sealed in a sanitary container, and is sold for human consumption. The U.S. Food and Drug Administration (FDA) and state governmental agencies regulate bottled water as a packaged food product. The members of the International Bottled Water Association (IBWA) produce and distribute about 85% of the bottled water sold in the United States. IBWA members must adhere to association standards besides those imposed by the government and undergo annual unannounced plant inspections by an independent third-party organization.
Imported European bottled water must meet the same federal and state standards. In addition, it must meet the strict standards set by the European Union. International bottler members who sell products in the United States must submit a certificate of inspection to the IBWA.
According to the Beverage Marketing Corporation in "2005 Stats" (2006, http://www.bottledwater.org/public/Stats_2005.doc), Americans consumed about 7.5 billion gallons of bottled water during 2005, a 10.7% increase from 2004. That figure translates into about twenty-six gallons per person in the United States, with bottled water ranking second only to carbonated soft drinks as the American beverage of choice.
Why Do Americans Like Bottled Water?
American consumers give a variety of reasons for their preference for bottled water. Some say they dislike the smell or taste of water from the tap or drawn from wells. Others cite the convenience of bottled water. In "Are Americans Financially Prepared for Disaster?" (Gallup Organization, October 18, 2005), Dennis Jacobe reports that 71% of Americans keep bottled water on hand in case of emergency.
Besides convenience, taste, and emergency use, concerns over the safety of public water supply systems since the September 11, 2001, terrorist attacks on the United States are prompting more Americans to rely on bottled water for their drinking water needs. According to the article "Take Me to the Water" (Supermarket News, May 26, 2003), a number of retailers report that concerns about terrorism have fueled a surge in the consumption of bottled water in the United States. The article states that between 1998 and 2003 sales of bottled water increased 150%.
DRINKING WATER SOURCE PROTECTION AND CONSERVATION
Because good sources of drinking water are a limited resource, the cost of developing and treating new sources is expected to rise. In addition, existing water suppliers are faced with the need to provide water to expanding service areas. As a result, the water industry is looking for cost-effective alternatives and is evaluating water conservation and reuse practices, as well as removing salt from seawater (desalinization) to create drinking water. Water suppliers are offering customers rebates for using water-efficient toilets and showers, and in some areas are limiting the amount that can be used for lawn and landscape watering or car washing. In some locations municipal and county water departments are promoting the reuse of treated wastewater for irrigation and lawn watering instead of using precious drinking water.
WATER IN THE THIRD WORLD—A DEADLY DRINK
Water quality varies greatly in developing nations, as poverty often results in inadequate distribution of resources, including food and water, and sanitation practices are generally poor. According to the United Nations (UN), in Water—A Shared Responsibility: World Water Development Report 2 (March 2006, http://unesdoc.unesco.org/images/0014/001444/144409E.pdf), one-sixth (1.1 billion) of the world's population is without access to an improved (safe and/or treated) water supply and 2.6 billion lack improved sanitation.
According to The 1st UN World Water Development Report: Water for People, Water for Life (March 2003, http://www.unesco.org/water/wwap/wwdr1/table_contents/index.shtml), as many as seven billion people in sixty countries could face water shortages by 2050. The report also suggests that pollution is a major problem, with 50% of the population in developing countries exposed to polluted water. A key goal, the UN report states, is to reduce by 50% the proportion of people who lack access to clean water by 2015.
Adequate quantities of safe water for drinking and for use in promoting personal hygiene are complementary measures for protecting public health. The lack of improved domestic water supply in the home leads to disease through two principal transmission routes: fecal-oral transmission and water-washed transmission.
In the fecal-oral transmission route, water contaminated with fecal material (sewage) is drunk without being treated or boiled, or food is prepared using this contaminated water, and waterborne disease occurs. Diseases transmitted by the fecal-oral route include typhoid, cholera, diarrhea, viral hepatitis A, dysentery, and dracunculiasis (guinea worm disease).
Water-washed transmission, the second route, is caused by a lack of sufficient quantities of clean water for washing and personal hygiene. People cannot keep their hands, bodies, and home environments clean and hygienic when there is not enough safe water available. The quantity of water that people use depends on their access to it. When water is available through a hose or house connection, people will use large quantities for hygiene. When water has to be hauled for more than a few minutes from source to home, the use drops significantly. Without enough clean water for good personal hygiene, skin and eye infections are easily spread, as are the fecal-oral transmission diseases.
The impact of poor water supply on human lives in developing and undeveloped countries is staggering. In Ecosystems and Human Well-Being: Health Synthesis (2005, http://www.who.int/globalchange/ecosystems/ecosysbegin.pdf), the World Health Organization states these statistics: "Water-associated infectious diseases claim up to 3.2 million lives each year, approximately 6% of all deaths globally. The burden of disease from inadequate water, sanitation and hygiene totals 1.7 million deaths and the loss of more than 54 million healthy life years." Good drinking water, improved personal hygiene, and better sanitation practices would reduce this worldwide disease burden dramatically.
|Public opinion on concern about the environment, 2006|
|Great deal||Fair amount||Great deal/fair amount|
|Source: Joseph Carroll, "Environmental Concerns," in Water Pollution Tops Americans' Environmental Concerns, Gallup Poll News Service, April 21, 2006, http://www.galluppoll.com/content/?ci=22492&pg=1 (accessed February 1, 2007). Copyright © 2006 by The Gallup Organization. Reproduced by permission of The Gallup Organization.|
|Pollution of drinking water||54||27||81|
|Contamination of soil and water by toxic waste||52||29||81|
|Pollution of rivers, lakes, and reservoirs||51||33||84|
|Maintenance of the nation's supply of fresh water for household needs||49||27||76|
|Damage to the Earth's ozone layer||40||28||68|
|The loss of tropical rain forests||40||24||64|
|The "greenhouse effect" or global warming||36||26||62|
|Extinction of plant and animal species||34||29||63|
|Public concern about pollution of drinking water, selected years 1990–2006|
|PLEASE TELL ME IF YOU PERSONALLY WORRY ABOUT THE POLLUTION OF DRINKING WATER A GREAT DEAL, A FAIR AMOUNT, ONLY A LITTLE, OR NOT AT ALL.|
|Great deal||Fair amount||Only a little||Not at all||No opinion|
|*Less than 0.5% of respondents|
|—Question was not asked for a given profession in this survey.|
|Source: "How much do you personally worry about … pollution of drinking water?" in Gallup's Pulse of Democracy: Environment, Gallup Poll News Service, March 2006, http://www.galluppoll.com/content/default.aspx?ci=1615&pg=2 (accessed February 1, 2007). Copyright © 2006 by The Gallup Organization. Reproduced by permission of The Gallup Organization.|
|2006 Mar 13-16||54||27||12||7||*|
|2004 Mar 8-11||53||24||17||6||*|
|2003 Mar 3-5||54||25||15||6||—|
|2002 Mar 4-7||57||25||13||5||*|
|2001 Mar 5-7||64||24||9||3||*|
|2000 Apr 3-9||72||20||6||2||*|
|1999 Apr 13-14||68||22||7||3||*|
|1991 Apr 11-4||67||19||10||3||1|
|1990 Apr 5-8||65||22||9||4||*|