Major Air Pollutants|
Source: Environmental Protection Agency, EPA 450K-92002, October 1992.
A colorless gas that is the major constituent of photochemical smog at the Earth's surface. In the upper atmosphere (stratosphere), however, ozone is beneficial, protecting us from the sun's harmful rays.
|Ozone is formed in the lower atmosphere as a result of chemical reactions between oxygen, volatile organic compounds, and nitrogen oxides in the presence of sunlight, especially during hot weather. Sources of such harmful pollutants include vehicles, factories, landfills, industrial solvents, and numerous small sources such as gas stations, and farm and lawn equipment.||Ozone causes significant health and environmental problems at the Earth's surface. It can irritate the respiratory tract, produce impaired lung function and cause throat irritation, chest pain, cough, and lung inflammation. It can also reduce the yield of agricultural crops and injure forests and other vegetation. Ozone is the most injurious pollutant to plant life.|
Odorless and colorless gas emitted in the exhaust of motor vehicles and other kinds of engines where there is incomplete fossilfuel combustion.
|Automobiles, buses, trucks, small engines, and some industrial processes. High concentrations can be found in confined spaces like parking garages, poorly ventilated tunnels, or along roadsides during periods of heavy traffic.||Reduces the ability of blood to deliver oxygen to vital tissues, affecting primarily the cardiovascular and nervous systems. Lower concentrations have been shown to adversely affect individuals with heart disease; higher concentrations can cause dizziness, headaches, and fatigue.|
Light brown gas at lower concentrations; in higher concentrations becomes an important component of unpleasant-looking brown, urban haze.
|Result of burning fuels in utilities, industrial boilers, cars, and trucks.||One of the major pollutants that causes smog and acid rain. Can harm humans and vegetation when concentrations are sufficiently high.|
Solid matter or liquid droplets from smoke, dust, fly ash and condensing vapors that can be suspended in the air for long periods of time.
|Industrial processes, smelters, automobiles, burning industrial fuels, woodsmoke, dust from paved and unpaved roads, construction, and agricultural ground breaking.||These microscopic particles can affect breathing and respiratory health, causing increased respiratory disease and lung damage, and possibly premature death.|
Colorless gas, odorless at low concentrations but pungent at very high concentrations.
|Emitted largely from industrial, institutional, utility and apartment-house furnaces and boilers, as well as petroleum refineries, smelters, paper mills, and chemical plants.||One of the major pollutants that cause smog. Can also, at high concentrations, affect human health, especially among asthmatics, and acidify lakes and streams.|
Lead and lead compounds can adversely affect human health through either ingestion of lead-contaminated soil, dust, paint, or direct inhalation.
|Transportation sources using lead in their fuels, coal combustion, smelters, car battery plants, and combustion of garbage containing lead products.||Elevated lead levels can adversely affect mental development, kidney function, and blood chemistry. Young children are particularly at risk.|
|Toxic Air Pollutants
Includes pollutants such as arsenic, asbestos, and benzenes.
|Chemical plants, industrial processes, motor vehicle emissions and fuels, and building materials.||Known or suspected to cause cancer, respiratory effects, birth defects, and reproductive and other serious health effects.|
|Stratospheric Ozone Depleters
Chemicals such as chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform. These chemicals rise to the upper atmosphere where they destroy the protective ozone layer.
|Industrial household refrigeration, cooling and cleaning processes, car and home air conditioners, some fire extinguishers, and plastic foam products.||Increased exposure to UV radiation could potentially cause an increase in skin cancer, cataracts, suppression of the human immune response system, and environmental damage.|
Gases that build up in the atmosphere that may induce global climate change or the greenhouse effect.They include carbon dioxide, methane, and nitrous oxide.
|The main man-made source of carbon dioxide emissions is fossil fuel combustion for energy-use and transportation. Methane comes from landfills, cud-chewing livestock, coal mines, and rice paddies. Nitrous oxide results from industrial processes, such as nylon fabrication.||The extent of the effects of climate change on human health and the environment is still uncertain, but could include increased global temperature, increased severity and frequency of storms and other weather extremes, melting of the polar ice cap, and sea-level rise.|