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Pollutant Information

Ozone • PM2.5 • Carbon Monoxide • Nitrogen Dioxide • Sulfur Dioxide • Lead
The six pollutants listed below are considered "criteria" pollutants and have National Ambient Air Quality Standards (NAAQS) set by the EPA Office of Air Quality Planning and Standards (OAQPS).

Ozone (O3)
Description: A colorless gas that is a major constituent of photochemical smog.
Sources: Forms in the air from other pollutants -- volatile organic compounds (VOCs) and nitrogen oxides (NOx). Ozone does not come directly from tailpipes or smokestacks. The VOCs that form ozone come from vehicle and industrial exhaust as well as evaporation of gasoline, solvents and paints, and many other sources.
Health Impacts: Irritates the lungs and breathing passages, causing coughing and pain in the chest and throat. Increases susceptibility to respiratory infections and reduces the ability to exercise. Effects are more severe in people with asthma and other respiratory ailments. Long-term exposure may lead to scarring of lung tissue and lowered lung efficiency. When ozone reaches unhealthy levels, children and people with asthma are most at risk.


Fine Particulates (PM2.5)
Description: Solid matter or liquid droplets with aerodynamic diameter of 2.5 microns and less.
Sources: Diesel cars, trucks and buses, power plants, industry and many other sources.
Health Impacts: Aggravates existing heart and lung diseases, changes the body's defenses against inhaled materials, and damages lung tissue. The elderly, children and those with chronic lung or heart disease are most sensitive. Lung impairment can persist for 2-3 weeks after exposure to high levels of particulate matter. Chemicals in and on particulates can also be toxic. Very fine particulates can be inhaled deeply into the lungs. When PM2.5 reaches unhealthy levels, people with respiratory or heart disease, the elderly and children are most at risk. Also damages paint, soils clothing and furniture and reduces visibility.


Carbon Monoxide (CO)
Description: An odorless, colorless gas resulting from incomplete combustion of fossil fuel combustion.
Sources: Automobiles, buses, trucks, small engines, boilers and some industrial processes. High concentrations can be found in confined spaces like parking garages, poorly ventilated tunnels, or traffic intersections, especially during peak hours.
Health Impacts: Weakens the heart's contractions and lowers the amount of oxygen carried by the blood. It reduces your ability to exercise and is dangerous for people with chronic heart disease. It can cause nausea, dizziness, headaches, and when it's very concentrated, even death. When carbon monoxide reaches unhealthy levels, people with heart disease are most at risk.


Nitrogen Dioxide (NO2)
Description: A yellowish brown, highly reactive gas that is the primary ingredient in production of ground level ozone.
Sources: Power plants, large industrial facilities, and motor vehicles.
Health Impacts: Irritates the nose and throat, especially in people with asthma. Appears to increase susceptibility to respiratory infections. Also combines with volatile organic compounds (VOCs) to form ozone. When nitrogen dioxide reaches unhealthy levels, children and people with respiratory disease are most at risk.


Sulfur Dioxide (SO2)
Description: A colorless gas, odorless at low concentrations but pungent at very high concentrations.
Sources: Power plants, large industrial facilities, diesel vehicles, and even oil-burning home heaters.
Health Impacts: Aggravates existing lung diseases, especially bronchitis. Constricts the breathing passages, especially in asthmatic people and people doing moderate to heavy exercise. Causes wheezing, shortness of breath, and coughing. High levels of particulates appear to worsen the effect of sulfur dioxide, and long-term exposures to both pollutants leads to higher rates of respiratory illness. When sulfur dioxide reaches unhealthy levels, people with asthma are most at risk.


Description: A heavy metal which can cause adverse health effects either through ingestion or direct inhalation.
Sources: Mostly from a few industrial facilities, such as coal combustion, smelters, car battery plants, and combustion of garbage containing lead products. Also from transportation sources using lead in their fuel, and sanding or wearing away of old lead-based paint.
Health Impacts: Causes damage to the brain and other parts of the body's nervous system. Children are most susceptible to the effects of lead. Lead can also harm wildlife.



VT DEC Air Quality & Climate Division Davis Building 2nd Floor, 1 National Life Drive   Montpelier, VT  05620-3802  Tele: 802-828-1288 Fax: 802-828-1250

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