Pollutants & Health Effects

Particulate Matter (PM)

Particulate matter or PM consists of soot and dust particles that are smaller than the diameter of a human hair. There are two classifications for particulate matter, PM10 and PM2.5. All particles smaller than 10 microns in diameter are classified as PM10, or coarse size particles. Fine size particles, or PM2.5, are those particles less than or equal to 2.5 microns in diameter. Particles that are smaller 2.5 microns are smaller than 1/8th the diameter of a human hair. Sources of PM include diesel exhaust, soil dust, tire wear, and soot. These particles penetrate deeply into the lungs and are captured by lung tissue. A major contributor to the PM pollution problem is exhaust from diesel vehicles, which produce 79% of the particulate emissions from mobile sources. The most dangerous aspect of PM pollution from diesel vehicles is the hundreds of different chemicals that are adsorbed to the particle. Exposure to PM pollution has been associated with respiratory and cardiac problems, infections, asthma attacks, lung cancer and decreased life expectancy. The World Health Organization has estimated that 500,000 premature deaths each year may be associated with PM pollution. Fine particulate air pollution (<2.5 microns) is thought to be more dangerous because of its ability to penetrate deeper into lung tissue. A recent study found that even a small increase in PM2.5 can result in a significant increase in mortality. In fact, The American Lung Association believes that PM2.5 represents the most serious threat to our health. Segments of the population that are more susceptible to PM pollution include children, athletes, senior citizens, and people with pre-existing respiratory problems.

Ozone (O3)

Ozone forms when hydrocarbons combine with nitrogen oxides and chemically react in sunlight. Hydrocarbons and nitrogen oxides are primarily produced by motor vehicles and various industrial practices. Ozone is a highly reactive oxidizing agent that breaks-down organic materials. Ozone is the primary component of smog, which has plagued Los Angeles for many years. A natural phenomenon called an "inversion layer" traps these gases and prevents them from dissipating into the atmosphere. The result is a serious smog problem in the valleys and basins of Southern California. Smog and the related high ozone levels are not just a California problem; Texas City, Texas recorded the highest one-day ozone level in the country for 1999. As populations grow, ozone and smog are becoming problems for large cities throughout the country. Symptoms of ozone exposure are coughing, shortness of breath, wheezing, fatigue, throat dryness, chest pain, headache and nausea. Ozone has been shown to cause inflammation of lung tissue and reduced lung capacity. Development of asthma, increased lung cancer mortality rates, and accelerated lung aging have all been linked to ozone exposure. Lung damage from long-term exposure to ozone can be permanent, while short-term exposure appears to be reversible. Ozone reduces the respiratory system's ability to fight infection and remove foreign particles such as particulate matter. Segments of the population that are more susceptible to ozone pollution include children, athletes, senior citizens, and people with pre-existing respiratory problems.

Hydrocarbons

Hydrocarbons are a class of reactive organic gases or ROG, which are formed solely of hydrogen and carbon. Hydrocarbons contribute to the formation of ozone and the resulting smog problem. Carcinogenic forms of hydrocarbons are considered hazardous air pollutants, or air toxics. The incomplete burning of any organic matter such as oil, wood, or rubber produces hydrocarbons. Combustion engine exhaust, oil refineries, and oil-fueled power plants are the primary sources of hydrocarbons. Another source of hydrocarbons is evaporation from petroleum fuels, solvents, dry cleaning solutions, and paint. The primary health effect of hydrocarbons results from the formation of ozone and its related health effects. High levels of hydrocarbons in the atmosphere can interfere with oxygen intake by reducing the amount of available oxygen through displacement.

Nitrogen Oxides (NOx)

Nitrogen monoxide (NO) and nitrogen dioxide (NO2) are the two forms of nitrogen oxide found in the atmosphere. Nitrogen oxides contribute to the formation of ozone, production of particulate matter pollution, and acid deposition. The presence of nitrogen oxides gives smog its brown appearance. Factories, motor vehicles and power plants that burn fossil fuels produce nitrogen oxides. Diesel engines produce a disproportionately large amount of NOx when compared to gasoline engines because of their high temperature combustion process. Nitrogen dioxide has been shown to irritate lung tissue, cause bronchitis and pneumonia, and reduce resistance to respiratory infections. The presence of NO2 in the atmosphere can have synergistic effects with other forms of air pollution. The health effects of ozone are magnified in the presence of nitrogen dioxide. Frequent or long-term exposure to high levels of nitrogen oxides can increase the incidence of acute respiratory illness in children.

Carbon Monoxide (CO)

Carbon monoxide is a colorless, odorless gas that is produced by burning organic matter such as oil, natural gas, fuel, wood, and charcoal. Motor vehicles produce 67% of the man-made CO that is released into the atmosphere. Carbon monoxide displaces oxygen in red blood cells, which reduces the amount of oxygen that human cells need for respiration. Exposure to CO can result in fatigue, angina, reduced visual perception, reduced dexterity, and death. The elderly, young children, and people with pre-existing respiratory conditions are particularly sensitive to carbon monoxide pollution. Carbon monoxide is extremely deadly in an enclosed space, such as a garage or bedroom.

Sulfur Dioxide (SO2)

Sulfur dioxide is a colorless gas produced by motor vehicles, refineries, and power plants that burn fossil fuels. Fossil fuels like coal and oil vary in sulfur concentrations and as a result the amount of sulfur dioxide they produce when burned. A high level of sulfur dioxide in exhaust gas can interfere with emission control mechanisms for other pollutants. Sulfur dioxide reduces respiratory volume, and increases breathing resistance in those exposed, especially asthmatics. Studies have also shown that sulfur dioxide increases nasal airway resistance. Other research has shown that daily mortality rates are consistently associated with sulfur dioxide and ozone levels.

Air Toxics

Air toxics, which are also known as hazardous air pollutants, are 188 toxic and potentially toxic compounds listed by the Federal Clean Air Act. Air toxics are generally organic chemicals, including some hydrocarbons that are highly evaporative in nature. Sources for air toxics are motor vehicles, chemical plants, paint, and any other operation that uses organic compounds. Benzene, formaldehyde, acetaldehyde, 1,3-butadiene, and acrolein are typical examples of air toxics. Air toxics are pollutants that cause or are suspected of causing cancer in those exposed to them. Cancer is the primary health effect studied due to the low exposure concentrations of these air toxics such as benzene, and formaldehyde. Benzene has been shown to cause aplastic anemia and acute myelogenous leukemia in occupational studies of workers exposed to it. Known health concerns related to aldehydes include cancer, asthma, and respiratory tract irritation. It is also believed that these air toxics have impacts on the reproductive system by causing chromosomal aberrations or mutations. The nature of air toxics still poses many uncertainties about their true health effects. These chemical compounds have many different forms and metabolites as they are broken down, and little is known about how they interact with the body. The health effects of particulate matter from diesel exhaust are thought to be attributable to the many air toxics that are adsorbed to the particles. These small particles penetrate deeply into the lungs, and are the perfect vehicle for delivering air toxics into the body.