Air Pollutants
Carbon dioxide (CO2) is part of the natural air. Additionally, CO2 is produced by burning fossil fuels. Excess levels of CO2 in the atmosphere can trap the sun’s heat, which many scientists believe causes global warming. CO2 does not have a federally established standard and is not monitored in Pa. CO2’s exclusion from standards and monitoring is a reflection of its not posing a direct human health risk.
Carbon monoxide (CO) is a colorless and odorless gas that is part of a car’s exhaust and is produced by some heating devices and industrial processes. Statewide, almost two-thirds of CO emissions come from highway vehicles! CO is very dangerous to breathe, for it is absorbed into the circulatory system in place of oxygen, and, thus can cause shortness of breath, impaired vision and neurological functioning or even death.
The most common threat from outdoor carbon monoxide across the nation is during rush hour in urban areas and in areas such as ski resorts that have large numbers of wood stoves concentrated in a relatively small area. Neither of these situations poses much immediate trouble in Pa. Carbon monoxide is monitored in Pa., and there are two federal standards of 35 parts per million over one hour and 9 parts per million over eight hours.
The 1995 CO levels across Pa. are about 26 percent lower than the levels in 1986. All urban areas in Pa. meet the health standard for CO in 1995.
Lead is a metal that is highly toxic when ingested or inhaled. Lead can affect a person’s blood, bones, kidneys and liver, as well as their nervous system. Unfortunately, lead does not leave the human body once it is there, and so accumulates over time. Lead has been omitted from all gasoline in the US, which has reduced air borne lead by 78 percent. Lead in the environment is residual, however. Today, much of the newly suspended lead in the air comes from industrial sources, chiefly battery processing facilities. Pa. monitors for lead and has met the federal standard of no more than 1.5 micrograms per cubic meter over three months time for the past 10 years.
Methane seeps into the air from areas where there is a large amount of decomposition occurring and where this gas is not free to immediately escape into the atmosphere. Thus, methane seeps from swamps, rice paddies, land fills and sewage sludge operations. Trapped methane is released during mining and drilling operations. Additionally, cows and termites are a significant source of methane.
Methane is a concern because it contributes to the blanketing and warming of the earth. There are no federal standards for methane which is not monitored in Pa., because it has not yet been determined to be a human health hazard.
Nitrogen oxides (NOx, meaning NO, NO2, NO3 and others) is an always changing group of compounds produced by burning fossil fuels, such as coal, oil, gasoline and natural gas. About half is produced by automobiles, trucks, buses and airplanes. The remaining half comes from industries and power plants that burn fossil fuels to make electricity. Nitrogen oxides threaten our health by entering our lungs and making breathing difficult. NOx is one of two pollutants that leads to the creation of ground-level ozone, and it is one of two major pollutants that leads to acid rain. There is no standard established for this group of chemicals, because a standard cannot be set for a group of chemicals. Nitrogen oxides are monitored in Pa.
The nitrogen-in-air picture is made more complex by the fact that NOx may be oxidized in the air to form particles of nitrate. These particles can cause lung damage. There is no standard for nitrates, but Pa. monitors for nitrates in the air.
Nitrogen dioxide (NO2) can, if concentrations are high enough, appear as a reddish-brown gas with an odor. It irritates the eyes and mucous membranes of the nose, reduces visibility in general and reduces photosynthesis in plants by blocking sunlight. This gas is toxic and can cause acute effects in sufferers of respiratory diseases. The standard for NO2 is 0.05 parts per million over a year’s time, and is monitored in Pa. The 12 air basins that DEP monitors are at or below 50 percent of the annual air quality standard for NO2. In general, NO2 levels have remained the same over the last decade in the Commonwealth.
Ozone (O3) may seem a bit confusing to the first time air quality learner, because there are two different places where ozone can be located. Ozone at ground level is bad while ozone above the troposphere is not only good, but necessary. Just remember, "Good up high, bad nearby."
Ground-level ozone is the main ingredient in smog; a haze that often marks urban areas and poses a serious health threat. The same compound occurs naturally above the troposphere where it shields the earth from most of the sun’s ultraviolet radiation, and so protects life from the effects of excessive radiation. Increased radiation from the sun causes increases in skin cancer, cataracts and damage to the human immune system and plants. This damage to vast amounts of sea plants is thought to contribute to increasing CO2 levels and thus to global warming by reducing the effectiveness of these plants to photosynthesize. Ground-level ozone does not travel away from earth to replenish the protective ozone level in space. This protective shield of high ozone is continually and naturally reinforced when solar radiation splits oxygen molecules into atoms, which then join intact oxygen molecules to form ozone, O3. The production and use of chloroflurocarbons (CFCs), which began in the late 1920s, was found to break down this high ozone faster than it could be naturally replaced. The federal Clean Air Act developed a plan for the phase out of the use of CFCs, which is on schedule.
Ground-level ozone is produced when quick-to-evaporate or volatile organic compounds and nitrogen oxides (NOx) react in the presence of intense sunlight. Sources of NOX and volatile organic compounds include gasoline vapors, fossil fuels use, automobile emissions and vapors from solvents such as those used in cleaning and industrial processes. Ozone can irritate eyes and damage lung tissue. In the young, the old and those with impaired breathing abilities such as folks with asthma, this damage can become a quality of life factor. Additionally, ozone damages crops and degrades materials such as rubber.
Ozone concentrations in the troposphere are erratic and depend, to a large extent, on weather conditions. The longer, warmer days of summer more easily lead to elevated ozone levels than blustery fall days, for example. The current federal standard for ground level ozone is 0.12 parts per million over an hour’s time. In 1995, in Pennsylvania, exceedances of this standard occurred in Southeast Pennsylvania and in the Lancaster Air Basin, along with a site in Murrysville, Westmoreland County, which is downwind from Pittsburgh.
The Commonwealth’s two Clean Air Stakeholder groups developed courses of anti-ozone actions tailored to each region. Both ozone nonattainment area programs have plans in place to alert people to high ozone days and to ask people to take voluntary reduction measures until the ozone level improves.
Ozone trends varied across the Commonwealth during the past decade. Refer to the chart titled Figure G-1, Ozone Trends in PA 1986 to 1995. This chart is located on page 29.
Particulates are the solid or liquid matter suspended in the air from combustion, eroded soil, industrial processes and condensed vapors. The smallest of these particles are breathed into the lungs where they can cause or aggravate respiratory ailments. Particles which settle onto the ground, a process called dry deposition, may cause direct plant damage and may be incorporated into the food chain by plant eaters. These particles can be corrosive to human-made products such as rubber and masonry. Acidic particles can dissolve in water and become acid rain. It would not be unheard of to have 43 tons of particulates settle in a square mile area in a month’s time! This amount is the Pa. standard for settleable particulates, which is a reflection of the total suspended particles (TSP). There has been little if any improvement in TSP in the Commonwealth over the past 10 years. In fact, the 1995 level of TSP was a 17 percent increase over the TSP level of 1993.
The federal government abandoned the use of TSP as an air quality standard several years ago, when it became clear from research that it was the very finest of particles that were causing the most health risk. The larger particles tend to settle before they are inhaled. If larger particles are inhaled they often become trapped in mucous membranes and are dealt with by the body in a fairly efficient manner. It is the particle less than 10 micrometers in diameter that can find its way into lung tissue. The particle that makes it this far, in addition to being undesirable by itself, can carry chemicals with it that are dangerous. Therefore, the state began monitoring for these tiny particles, called PM10, in 1985. The source of these smaller particles is primarily from transportation and industrial processes. The federal standard for PM10 is no more than 150 micrograms per cubic meter in 24 hours and 50 micrograms per cubic meter over one year. There has been a slight improvement of PM10 levels in Pa. over the last 10 years.
Sulfur dioxide or S02 is a gas commonly released from coal and oil burning power plants and furnaces. When inhaled, it can restrict air passages and impair breathing. People with asthma, young childrenand the elderly are especially susceptible to its negative effects, as are those with cardiovascular diseases. Additionally, SO2 damages plants directly and is a main component in acid rain. It combines with water vapor in the atmosphere to form sulfuric acid, which returns to the earth in the form of acid rain, snow or fog. Because of this pollutant’s link to fuels used in keeping warm, seasonal variations in its concentrations are demonstrated. Sulfur dioxide is monitored in Pa. The federal standards are 0.5 parts per million over three hours; 0.14 parts per million over 24 hours; and 0.03 parts per million as a yearly average. Sulfur dioxide levels in Pa. have improved slightly, or remained the same over the last 10 year period.
Sulfur is also involved in air pollution when it is in the form of sulfate. Sulfates can be emitted directly into the atmosphere from industrial processes. Additionally, sulfates can be formed in the atmosphere from other sulfur containing compounds in photochemical reactions. Sulfates are monitored in Pa. using units of micrograms per cubic meter. The state standard is no more than 30 micrograms of sulfates per cubic meter in a 24 hour period and no more than 10 micrograms per cubic meter in 30 days. The sulfate standard was violated at all monitoring sites in PA in 1995.