• Volcanic ash spewed into the atmosphere,
• Smoke from wild fires ignited by lightning,
• Dust particles stirred up by the wind,
• Organic particles like pollen and mold spores

• Power plants
• Oil refineries
• Manufacturing plants
• Vehicles, planes, ships, trains
• Chemical plants
• Incinerators
• Home heating furnaces & stoves

 Sources of Air Pollution

Data from http://www.epa.gov/air/emissions/index.htm

 Health Effects of Criteria Pollutants

From http://www.epa.gov/region7/air/quality/health.htm

 Pollutant Concentrations Over Time

Data from http://www.epa.gov/airtrends/index.html

Carbon Dioxide

"Carbon monoxide is a colorless odorless poisonous gas formed when carbon in fuels is not burned completely. It is a byproduct of motor vehicle exhaust, which contributes more than two-thirds of all CO emissions nationwide. In cities, automobile exhaust can cause as much as 95 percent of all CO emissions."

"Carbon monoxide enters the bloodstream and reduces oxygen delivery to the body's organs and tissues. The health threat from CO is most serious for those who suffer from cardiovascular disease. Healthy individuals are also affected, but only at higher levels of exposure. Exposure to elevated CO levels is associated with visual impairment, reduced work capacity, reduced manual dexterity, poor learning ability, and difficulty in performing complex tasks."

NOTE: High concentrations, e.g., from a car running in an unvented garage or from poorly vented kerosene heaters, can be fatal.

See also CO in Smokers.

Lead

"Exposure to lead mainly occurs through inhalation of air and ingestion of lead in food, paint, water, soil, or dust. Lead accumulates in the body in blood, bone, and soft tissue. Because it is not readily excreted, lead can also affect the kidneys, liver, nervous system, and other organs. Excessive exposure to lead may cause anemia, kidney disease, reproductive disorders, and neurological impairments such as seizures, mental retardation, and/or behavioral disorders. Even at low doses, lead exposure is associated with changes in fundamental enzymatic, energy transfer, and other processes in the body. Fetuses and children are especially susceptible to low doses of lead, often suffering central nervous system damage or slowed growth. Recent studies show that lead may be a factor in high blood pressure and subsequent heart disease in middle-aged white males. Lead may also contribute to osteoporosis in postmenopausal women."

After banning lead additives in gasoline, the primary source of lead in the has become smelters and battery plants. The highest concentrations of lead are found in the vicinity of nonferrous smelters and other stationary sources of lead emissions.

Nitrogen Oxides

Nitrogen oxides form when fuel is burned at high temperatures and come principally from motor vehicle exhaust and stationary sources such as electric utilities and industrial boilers. A suffocating, brownish gas, nitrogen dioxide is a strong oxidizing agent that reacts in the air to form corrosive nitric acid, as well as toxic organic nitrates. It also plays a major role in the atmospheric reactions that produce ground-level ozone (or smog).

Health and Other Effects: Nitrogen dioxide can irritate the lungs and lower resistance to respiratory infections such as influenza. The effects of short-term exposure are still unclear, but continued or frequent exposure to concentrations that are typically much higher than those normally found in the ambient air may cause increased incidence of acute respiratory illness in children. EPA's health-based national air quality standard for NO2 is 0.053 ppm (measured as an annual average). Nitrogen oxides are important in forming ozone and may affect both terrestrial and aquatic ecosystems. Nitrogen oxides in the air are a potentially significant contributor to a number of environmental effects such as acid rain and eutrophication in coastal waters like the Chesapeake Bay. Eutrophication occurs when a body of water suffers an increase in nutrients that reduce the amount of oxygen in the water, producing an environment that is destructive to fish and other animal life."

Particulate Matter (PM2.5 and PM10)

"Particulate matter is the term for solid or liquid particles found in the air. Some particles are large or dark enough to be seen as soot or smoke. Others are so small they can be detected only with an electron microscope. Because particles originate from a variety of mobile and stationary sources (diesel trucks, wood stoves, power plants, etc.), their chemical and physical compositions vary widely."

Particles less than 10 microns (micrometers) in diameter can be inhaled, and these are divided into PM-10 and PM2.5. PM-10 includes particles with a diameter of 10 microns or less; these tend to be generated by wind or mechanical agitation from plowing, grinding, etc. Particles between 2.5-10 microns tend to adhere to the mucus in the trachea and bronchi; they are then gradually swept up to the pharynx by the cilia on epithelial cells lining the respiratory tract. Once they reach the pharynx, they can be swallowed or expectorated.

PM-2.5 particles with a diameter of 2.5 microns or less, often referred to as "fine particulates", are mostly generated from combustion. Ultrafine particles, <0.1 microns, are generated from diesel engines, particularly when they are idling. Particles <2.5 microns are able to reach the lower respiratory tract and alveoli because they are small and light and can be carried easily with the inspired air.

Health Effects:

"Major concerns for human health from exposure to particulate matter are: effects on breathing and respiratory systems, damage to lung tissue, cancer, and premature death. The elderly, children, and people with chronic lung disease, influenza, or asthma, tend to be especially sensitive to the effects of particulate matter. Acidic particulate matter can also damage manmade materials and is a major cause of reduced visibility in many parts of the U.S. Click here for more information on the health effects of particulate matter."

Sulfur Oxides

"These gases are formed when fuel containing sulfur (mainly coal and oil) is burned, and during metal smelting and other industrial processes.

Health and Other Effects: The major health concerns associated with exposure to high concentrations of SO2 include effects on breathing, respiratory illness, alterations in pulmonary defenses, and aggravation of existing cardiovascular disease. Major subgroups of the population that are most sensitive to SO2 include asthmatics and individuals with cardiovascular disease or chronic lung disease (such as bronchitis or emphysema) as well as children and the elderly. EPA's health-based national air quality standard for SO2 is 0.03 ppm (measured on an annual average) and 0.14 ppm (measured over 24 hours). Emissions of SO2 also can damage the foliage of trees and agricultural crops. EPA has a secondary SO2 national ambient air quality standard of 0.50 ppm (measured over 3 hours) designed to prevent this type of environmental deterioration. Together, SO2 and NOX are the major precursors to acid rain, which is associated with the acidification of lakes and streams, accelerated corrosion of buildings and monuments, and reduced visibility."

Volatile Organic Compounds

"Unlike other pollutants, ozone is not emitted directly into the air by specific sources. Ozone is created by sunlight acting on nitrogen oxides (NOx) and volatile organic compound (VOC) emissions in the air. There are literally thousands of sources of these gases. Some of the more common sources include gasoline vapors, chemical solvents, combustion products of various fuels, and consumer products. They can originate from large industrial facilities, gas stations, and small businesses such as bakeries and dry cleaners. Often these "precursor" gases are emitted in one area, but the actual chemical reactions, stimulated by sunlight and temperature, take place in another. Combined emissions from motor vehicles and stationary sources can be carried hundreds of miles from their origins, forming high ozone concentrations over very large regions.

Health and Other Effects: Scientific evidence indicates that ground-level ozone not only affects people with impaired respiratory systems (such as asthmatics), but healthy adults and children as well. Exposure to ozone for 6 to 7 hours, even at relatively low concentrations, significantly reduces lung function and induces respiratory inflammation in normal, healthy people during periods of moderate exercise. It can be accompanied by symptoms such as chest pain, coughing, nausea, and pulmonary congestion. Recent studies provide evidence of an association between elevated ozone levels and increases in hospital admissions for respiratory problems in several U.S. cities. Results from animal studies indicate that repeated exposure to high levels of ozone for several months or more can produce permanent structural damage in the lungs.

Ozone Formation

The naturally occurring ozone in the stratosphere protects the earth from the damaging effects of ultraviolet radiation from the sun. However, so called ground level ozone that forms as a result of man-made pollution, is harmful to health. Ozone is produced in the atmosphere by a chemical reaction between nitrogen oxides, volatile organic compounds, and light and heat energy from the sun.