Pollution emissions are down since 1970, the year when the first Clean Air Act Amendments took effect. The exception is oxides of nitrogen, usually abbreviated as NOXs. Particulate matter (dust, soot, usually reported as PM-10) went down from 1985 to 1995, but then rose again a little in 1998. The steep drop of lead in the air — it went from 220,900 tons in 1970 to 4,000 tons in 1998 — happened at the filling station. Leaded gasoline was phased out. Overall, levels of these air pollutants have been below the EPA's standards for safety since the 1970s. But some urban, industrialized cities still don't meet safety standards. In 1997, the EPA lowered the standards for ground-level ozone (source of the famous LA smog), to which volatile organic chemicals (VOCs) and NOXs are contributors. U.S. air quality continues to exceed these new standards.
What are these pollutants? What are their effects?
Lead (Pb) occurs naturally as a metal and has been used in many products. Its greatest use in modern times has been as an anti-knock component of gasoline. In 1970, 78% of lead emissions came from motor vehicles. Unleaded gasoline came to be introduced in 1975 for use with cars equipped with catalytic converters. In December 1995, EPA banned leaded gasoline altogether. From 1980 to 1999, lead emissions dropped by 94%. Currently, 52% of lead emissions come from metals-processing facilities. Urban areas with high traffic levels, trash incinerators, or industrial facilities that burn fuel still have a problem with high lead levels in the air. In 1999, 10 cities still failed to meet EPA's levels for lead.
Children and infants are most sensitive to lead in the air. They continue to have the highest lead levels in their blood among the general population. Children are also exposed to lead by ingesting paint chips, soil, food, and water contaminated with lead. Leaded paint was banned in 1978, but older homes may still have it. Lead accumulates in the blood. Continued exposure, even at low levels, can ultimately lead to organ damage, osteoporosis, and reproductive disorders. High levels of lead can lead to seizures, mental retardation, and behavior problems. Lead exposure is also implicated in high blood pressure and in heart disease, especially in men. Animals suffer as do people — and even low levels of lead can inhibit the growth of vegetation and cause reproductive and neurological damage in marine life.
Particulate matter (PM-10) is a mixture of solid particles and liquid droplets in the air. Particles 2.5 micrometers or larger are found in windblown dust and come from grinding operations. Tinier particles (2.5 micrometers or smaller) come from fuel combustion, power plants, trucks and buses burning diesel. These tiny objects are the most dangerous because they easily reach the deep recesses of the lungs. PM-10 has thus been linked to premature death, asthma, and other breathing ailments. The elderly, children, those with heart or lung disease, and asthmatics are most affected by this pollutant.
PM-10 also causes haze. In the west, natural visibility is 140 miles, but particulate pollution has reduced the range to somewhere between 33 to 90 miles. It's worse in the east. Natural visibility is 90 miles, but the current range is merely 14 to 24 miles. Thirty-three percent of the haze in the Grand Canyon is caused by PM-10 emissions from Southern California. PM-10 can also damages to buildings and erodes our monuments.
Sulfur dioxide (SO2) gas is formed when coal and oil are burned. It's also found during metal smelting and other industrial processes. Exposure to this gas has been linked to breathing difficulties, lower immunity to respiratory infections, and aggravation of cardiovascular disease (if exposed in combination with PM-10). The elderly, children, those with preexisting cardiovascular and lung disease, and asthmatics are most affected by this pollutant.
SO2 and acid rain are linked. The sulfur compound dissolves in the rain. The sour liquid acidifies soil, lakes, and streams. In turn this conditions kills crops and wildlife. Sulfur oxides also attack buildings and monuments. On June 24, 2002, China announced a program to reduce SO2 emissions 10% by 2005 by targeting its biggest industrial polluters. The U.S. reduced SO2 emissions by 18% from 1986 to 1995 (13% in 1994-1995 alone).
Volatile organic chemicals (VOCs). These chemicals are used in household products such as paints, varnishes, and cleaners. They are organic solvents. When used they spread in the air. Indoor air pollution is largely a consequence of VOCs. The EPA's studies found levels of some organic chemicals to be 2 to 5 times higher inside homes than out of doors. These chemicals can cause eye, nose, and throat irritation; headaches; nausea; and damage to liver, kidney, and the central nervous system. Some, like benzene, cause cancer in humans. Methylene chloride and perchloroethylene (used in paint strippers and dry cleaning, respectively) have been found to cause cancer in animals.
VOCs are known to contribute to the development of smog. When inhaled (even in small amounts), smog can cause respiratory problems, inflammation of lung tissue, and it reduces a person's immunity to bronchitis and pneumonia. Children and asthmatics are susceptible to the effects of smog — but so are healthy adults who moderately exercise in the summer. They can experience 15 to 20% reduction in lung function over several hours of exposure to low levels of smog.
Nitrogen oxides (NOXs) are a family of gases produced during high temperature fuel combustion (cars, utilities). They contribute to ground-level ozone (smog), acid rain, and eutrophication2. Nitrous oxide, one type of NOX, is a greenhouse gas. Greenhouse gases cause climate changes — global warming. NOXs irritate the lungs and lower immunity to respiratory infections. Those with respiratory problems and heart disease are most affected. But exposure to these gases may also cause these types of health problems.
Carbon monoxide (CO) is a colorless, odorless poisonous gas emitted from the incomplete combustion of hydrocarbon-based fuels (like gasoline, diesel, coal, and gas). In the
U.S., 66% of the carbon monoxide emissions come from motor vehicles. In urban areas, motor vehicles contribute about 90% of the carbon monoxide. In 1992, carbon monoxide levels in 20 U.S. cities exceeded the Federal air quality standard and affected 14 million people. CO is still with us despite the fact that auto companies added catalytic converters to their passenger vehicles in the 1970s — which reduce carbon monoxide emissions by 80% per vehicle.
Carbon monoxide inhibits a person's blood from carrying oxygen to organs and tissues. The monoxide grabs hold of oxygen to form carbon dioxide, the gas we breathe out. Those with heart disease are highly susceptible to the effects of carbon monoxide and may experience chest pains if they breathe in the gas while exercising. Infants, the elderly, and people with respiratory problems also have sensitivity to CO.
Sources: Chart data for 1940-1960: U.S. Census Bureau. Statistical Abstract of the United States, 1994. Chart data for 1970-1998: U.S. Census Bureau. Statistical Abstract of the United States, 2001. "Sulfur Dioxide." Retrieved June 25, 2002 from http://www.cleanairtrust.org/sulfurdioxide.html. U.S. Environmental Protection Agency data retrieved June 24-26, 2002 and July 8-10, 2002 from http://www.epa.gov. Patricia Primi and Michael H. Surgan. Look Out For Lead!, July 1999. Retrieved July 3, 2002 from http://www.oag.state.ny.us/envi-ronment/lead96.html. World Health Organization. "Air Pollution Fact Sheet," September 2000. Retrieved July 10, 2002 from http://www.who.int/inf-fs/en/fact187.html.
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