Many industrial manufacturing processes use or produce chemicals that may harm people’s health or the environment. For instance, paper pulp bleaching uses chlorine (Cl), while power generation using coal creates acid rain. Although factory chimneys producing black smoke are rare in most industrial nations these days, invisible pollutants may still enter the air, ground, or surface water. Even at low levels, they may cause harm, particularly in the long term.
Environmental law now requires industry to take more responsibility for any emissions that could harm the environment. Ongoing independent monitoring of the air and water supply are necessary to check for any breaches of legislation. Cleaner technologies, including green chemistry, can reduce production of pollutants from their source. However, there is still a legacy of industrial pollution from the past with contaminated sites that have residues of long-lasting chemicals such as polychlorinated biphenyls, or PCBs (C12H10-xClx), which were once very widely used.
Historical Background and Scientific Foundations
Pollution generally refers to a change that is harmful to the environment. A typical example might be discharge of chlorine-containing organic solvents from a factory pipe into a river. Industrial pollution on a large scale began with the Industrial Revolution of the nineteenth century, when factories emitting dirty smoke were seen as a sign of growing prosperity. Soot and acid rain deposition in towns and cities was common and few were aware of their impact on human health and the environment.
Coal was the predominant source of fuel. Its potential to pollute arises from its sulfur (S) content, which can be as high as 10%. Coal also contains significant amounts of toxic heavy metals, including lead (Pb), cadmium (Cd), and mercury (Hg), which remain in the ash when it is burned. Oil began to grow in importance as a fuel in the early part of the twentieth century. By the 1940s, a massive petrochemical industry had grown up, using petroleum as a raw material for the synthesis of a range of new organic compounds, including plastics, pesticides, and pharmaceuticals.
Any modern industry has the potential to produce some pollution. Often this is in the form of wastewater that has been used in processing or for cleaning equipment, and has thereby become contaminated with pollutants. Some byproducts of industrial processes are polluting, such as the toxic dioxins (C4H4O2) produced in the manufacture of certain herbicides, or the acidic sulfur dioxide (SO2) produced by burning coal. The paper and pulp industry has attracted criticism from environmental campaigners in the past over its use of chlorine as a bleaching agent. The chlorine combines with organic compounds in the wood to make a number of hazardous organochlorine compounds, including furans (C4H4O) and dioxins. There has been a move within the industry toward chlorine-free technology, but this is not yet universal.
The chemical industry has produced thousands of synthetic compounds with a very wide range of applications that are often taken for granted in everyday life. These compounds are xenobiotics, which means they do not occur in nature and may take a long time to break down in the environment by microbial action. One example would be the relative rates of decay of a paper bag and a plastic bag, left out to rot. Paper is based on cellulose, a natural material, and is therefore biodegradable. It will take two to five months to rot away, but the plastic bag will, according to laboratory estimates, take
WORDS TO KNOW
BIOLOGICAL MAGNIFICATION: Increase in concentration of toxins as they pass up the food chain.
POINT SOURCE POLLUTION: Pollution arising from a fixed source, such as a pipe.
POLLUTION: Physical, chemical or biological changes that adversely affect the environment.
XENOBIOTICS: Synthetic organic compounds that are hard to break down in the environment.
500 to 1,000 years. Plastic is not, in itself, harmful, so the main problem with plastic bags is that they take up space in expensive landfills. Other synthetic organic compounds pose a far greater threat to the environment.
Chlorofluorocarbons (CFCs) were developed in the 1930s. They are non-toxic, inert, nonflammable, and very cheap to produce, and they were therefore soon widely used as a refrigerant, as propellant in spray cans, and in insulation. In 1985, scientists for the British Antarctic Survey discovered a “hole” in the stratospheric ozone layer over the South Pole. This ozone protects against ultraviolet light from the sun and its depletion
raises the risk of skin cancer and plant damage. CFCs are so stable that their emissions reach the stratosphere without breaking down, where they then participate in a series of chemical reactions whose end result is the destruction of ozone. CFCs are now being phased out, thanks to the Montreal Protocol of 1987, but the CFCs already in the atmosphere will continue to do damage for many years to come.
Another group of chemicals with a hefty environmental price tag is the polychlorinated biphenyls (PCBs), which are high up on the U.S. Environmental Protection Agency’s list of toxic and hazardous substances. PCBs were once widely used in electrical equipment as an insulating material, but their production was banned in the United States in 1977 when it became clear that they could affect the liver, immune, and nervous systems of wildlife and humans. PCBs still persist in old electrical equipment and on sites contaminated by hazardous waste.
Future problems from industrial pollution could come from environmental estrogens, also known as endocrine disrupters. These chemicals, widely distributed in toiletries, plastics, and other everyday products, have an action like the female sex hormone estrogen on living cells. Their presence at even low levels in water resources has been linked with fertility and development problems in fish and falling sperm count in human males.
Water and air are both at risk from industrial pollution. Factories are point sources of pollution because emissions enter water from a specific location such as pipe or ditch, which at least makes them easier to monitor and regulate. Toxins in water may enter at a low concentration, but they are concentrated in the tissue of organisms as they pass up the food chain. People eating polluted fish may be putting their health at risk. A notorious example from the 1950s and 1960s is Minamata, Japan, where thousands were poisoned after eating shellfish containing mercury waste from a nearby chemical factory.
Pollution of the water supply need not be chemical in nature. Many industrial processes generate heat and use large amounts of cooling water, which may be drawn from the nearest river or lake. It is then returned to its source, possibly at a higher temperature if it has been insufficiently cooled beforehand. This artificial warming may have a deleterious impact on local ecosystems, because aquatic organisms do not usually adapt well to rapid temperature change. Oxygen solubility decreases with rising temperature, putting species requiring high oxygen levels at risk.
Thick smogs and smokes resulting from industrial pollution are now less common in developed countries, thanks to tighter controls on emissions. The major industrial pollutants affecting air quality are sulfur dioxide, volatile organic solvents, and particulate materials, such as metal dust. Burning waste, particularly plastics, can also produce dioxins and other hazardous chlorinated compounds. Sulfur emissions form particles of sulfuric acid (H2SO4) to make acid rain, which can damage surface water and trees many miles away from its source.
Impacts and Issues
Industry has been forced to take measures to reduce its impact on the environment in recent years due to government regulation. Cleaner technologies may require investment in the short term but could save money in the end by reducing the use of raw materials and costs in dealing with emissions.
In the United States, the 1972 Clean Water Act requires industries to have a permit for dumping their waste in surface water and to disclose what they are letting into the water supply. The act has significantly reduced, although not eliminated, water pollution from industry. The Clean Air Act was introduced in 1963 and has been amended many times, amid criticism from industry that controls cost too much and complaints from environmental groups that the public is given too little protection. The legislation has worked well in helping clean up sulfur dioxide emissions, with industry finding that it costs far less than originally estimated.
Cunningham, W.P., and A. Cunningham. Environmental Science: A Global Concern. New York: McGraw-Hill International Edition, 2008.
Kaufmann, Robert, and Cutler Cleveland. Environmental Science. New York: McGraw-Hill, 2007.
Friends of the Earth. “The Environmental Consequences of Paper and Pulp Manufacture.” 2001. http://www.foe.co.uk/resource/briefings/consequence_pulp_paper.html (accessed April 20, 2008).
U.S. Environmental Protection Agency. “Introduction to the Clean Water Act.” October 28, 2002. http://www.epa.gov/watertrain/cwa (accessed April 20, 2008).