Air and water purity

DEFINITION: Extent to which natural water and air supplies are free of harmful forms of contamination.

SIGNIFICANCE: Various forms of chemical and biological contaminants that pollute air and water supplies are responsible for death, disease, climate shifts, and the alteration of fragile ecosystems around the world. Techniques used to investigate the nature and causes of pollution are allied with forensic toxicology.

Although challenges to air and water purity have always existed, the assault has taken on forbidding aspects since the advent of the industrial age. So ubiquitous are the sources of air and water pollution that they have become woven into the fabric of everyday modern life. However, it is important to note that although much pollution comes from the processes of industry and commerce, pollution is also a product of natural biological and geographic processes. It should also be kept in mind that purity and pollution are relative. For example, although oxygen is necessary for animal life, it is highly toxic to certain organisms that flourish in an atmosphere of methane, which would be lethal to human beings.

Human-made pollutants come from the combustion of fuels that power ships, aircraft, motor vehicles, factories, and power-generating plants. Natural pollutants come from the discharges of wildfires and volcanoes. Pollutants also come from chemical discharges and landfill outgassing, as well as military operations that generate nuclear fallout, pathogens, and toxic gases. Pollutants even ride the wind in the form of dust.

A notorious example of the damage inflicted when human activities alter the air’s chemistry comes in the form of chlorofluorocarbons (CFCs), which find wide applications as refrigerants, insulating foams, and solvents. CFCs eventually make their way into the stratosphere, where the ultraviolet (UV) rays of sunlight break the CFCs’ chemical bonds and release their chlorine atoms. As one chlorine atom is capable of breaking apart 100,000 ozone molecules, the damage to Earth’s ozone layer is great. The ozone layer protects Earth’s surface from the damaging UV rays of the sun; without its protection, human beings are vulnerable to immune disorders, skin cancer, and cataracts. Additionally, increased UV radiation can reduce crop yields and cause serious dislocations in the marine food chain.

The quality of naturally occurring freshwater may be degraded through natural sources such as bedrock salts or sediment containing organic material. Additional degradation of water quality may be caused by human manipulation, such as fertilizers and petroleum products. When water pollution comes from a single source, such as a sewage-outflow pipe, it is called point-source pollution; when the exact source of pollution is not as clear, as in agricultural or urban runoff, it is called non-point-source pollution.

The principal water polluters are industry and agriculture. Rain helps to cleanse air of pollutant emissions from motor vehicles, factories, and heating boilers, but the pollutants ultimately find their way into groundwater and streams. More direct forms of water pollution come from industrial discharges, construction detritus, and agricultural runoff. All these forms of pollution change the chemistry of water, changing its acidity, conductivity, and temperature. Nitrogen runoff fertilizes water, causing it to be choked with new vegetation.

The consequences for human society of impure water are alarming. Intractable diarrhea is a leading cause of death around the world among children under five, and its main cause is degraded drinking water. Cholera, a potentially deadly bacterial infection that plagues much of the underdeveloped world, requires only clean drinking water and proper sanitation to be eliminated as a problem. Contaminated drinking water is responsible for up to fourteen thousand deaths every day in developing countries.

Sources of water pollution include sewage, industrial discharges, surface runoff from farms and construction sites, underground storage tank leakage, and acid rain. It is convenient to categorize water contaminants into subgroups: microorganisms, disinfectants, disinfection by-products, inorganic chemicals, organic chemicals, and radionuclides. The US government’s Environmental Protection Agency (EPA) lists eighty-six specific water contaminants, along with their sources and potential health effects.

Examples of specific pollutants include alachlor, an herbicide used in row crops that increases human risks of cancer and can also cause eye, liver, and kidney disease. Cadmium, which reaches water supplies from corroded galvanized pipes and discharges from metal refineries, can cause kidney damage. Dioxin is a chemical discharge from factories that causes cancer and reproductive disorders. Giardia lamblia is a protozoan parasite found in human and animal waste that often causes gastrointestinal disturbances. Toxaphene, an active ingredient in insecticides used in cotton farming and cattle production, increases cancer risk and can cause kidney, liver, and thyroid problems. Vinyl chlorides from plastic manufacturing discharges and leaching from polyvinyl chloride pipes also increase cancer risks.

Air Quality

Air pollution not only threatens the health of human beings but also compromises the well-being of animal and plant life. It degrades bodies of freshwater, thins the atmosphere’s protective ozone layer, and creates haze that shrouds the beauty of nature. The EPA attempts to sustain reasonable levels of air purity through regulatory enforcement and voluntary programs, such as Energy Star and Commuter Choice. Through the federal Clean Air Act of 1990, the EPA restricts the amounts of specific pollutants allowed into the atmosphere to help protect public health.

Under the surveillance of the EPA are these broad categories of atmospheric pollutants: aerosols, asbestos, carbon monoxide, chlorofluorocarbons, ground-level ozone, hazardous air pollutants, hydrochlorofluorocarbon refrigerants, lead, mercury, methane gas, nitrogen oxides, particulate matter, propellants, radon, refrigerants, sulfur oxides, and volatile organic compounds. The EPA is armed with government regulations. Through a cooperative effort that involves private industry and state and local governments, the agency calls for the discontinuation of ozone-depleting substances, the elimination of specified toxic chemicals, and the treatment of polluted areas.

To assess air quality, the EPA’s Office of Air Quality Planning and Standards (OAQPS) monitors specific pollutants that can harm human health, the environment, and property. All common throughout the United States, these pollutants include sulfur dioxide, particulate matter, nitrogen dioxide, lead, and carbon monoxide. Based on national ambient air quality standards, geographic areas are designated as attainment or nonattainment areas. OAQPS gives the standards more meaning by subdividing them into primary and secondary standards. Primary standards are about issues of health, whereas secondary standards consider damage to crops, vegetation, or buildings. Further, they assess the health effects for their potential long- or short-term damage.

Bibliography

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