Descriptions of various pollutants

Ozone (ground level)
Sources: Produced by chemical reactions among pollutants, released mainly by motor vehicles (nitrogen oxides and volatile hydrocarbons).
Environmental impacts: A strong oxidant gas that damages animal respiratory systems, plant leaf cells, reducing photosynthesis.
Human health concerns: A respiratory irritant causing damage to the lungs, reducing lung capacity and aggravation respiratory problems, especially in the elderly, the very young, and the asthmatic.
EPA maximum allowable level: An average of 80 ppm (parts per million) for any 8 hour period. It is important to note that the current guidelines have been found to be inadequate in protecting human health and are in the process of being revised.

Particulate Matter
There are three size classes of particles in the air that are regulated: fine (less than 2.5 micrometers [um] in diameter); coarse (less than 10 um in diameter); and total (all particles up to about 50 um). While the regulations govern only the amount of these particles in our air, their composition (which may include toxic compounds as well as dust, salts, and soot) is also a concern.
Sources: Industrial and vehicle combustion, woodsmoke, refining, industrial and vehicle abrasion, road dust, quarrying, milling, large scale transfer of dusty materials.
Environmental impacts: Visibility reduction, respiratory irritant, and nuisance.
Human health concerns: Fine particles are a respiratory irritant, causing lung damage, bronchitis, and asthma; all particles can be somewhat irritating, especially to those with respiratory problems.
EPA maximum allowable level: Fine (PM 2.5) 15 micrograms per cubic meter (ug/m3 ) annual average and 65 ug/m3 for any 24 hour period. Coarse (PM 10) 50 ug/m3 annual average and 150 ug/m3 for any 24 hour period. Total (TSP)

Benzene:
Sources: Vehicle exhaust, vapors at gas pump, fossil fuel emissions and wood stove combustion.
Human health concerns: Long-term exposure to elevated levels may damage tissues, cause anemia, and leukemia.
State maximum allowable level: 0.12 ug/m3
1994 annual average in Burlington: 2.62 ug/m3

1,3,-Butadiene:
Sources: Vehicle exhaust, and the emissions from wood burning and waste incinerators.
Human health concerns: Irritant to eyes, nose and throat; exposure to high levels can damage the central nervous system, cause blurred vision, nausea, fatigue, decrease blood pressure and pulse rate. Increased incidences of heart disease, lung disease, and cancer have been noted in workers who have inhaled butadiene for long periods of time.
State maximum allowable level: 0.035 ug/m3
1994 annual average in Burlington: 0.64 ug/m3

Carbon tetrachloride:
Sources: Refrigerant and aerosol propellant. Has been used in the past used in degreasers, cleaning fluids, and fire extinguishers.
Human health concerns: Has been classified as human carcinogen by the EPA.
State maximum allowable level: 0.067 ug/m3
1994 annual average in Burlington: 0.71 ug/m3

Chloroform
Sources: Emissions from pulp and paper mills and used in wastewater treatment plants as a disinfectant.
Human health concerns: Inhaling large amounts can affect the central nervous system. Chloroform breaks down into phosgene and hydrogen chloride, both of which are toxic. Has been classified as a probable human carcinogen by the EPA.
State maximum allowable level: 0.043 ug/m3
1994 annual average in Burlington: 0.22 ug/m3

Formaldehyde
Sources: A byproduct of combustion in vehicles and wood stoves. Used in wood processing plants and glues.
Human health concerns: Eye, nose, and throat irritant. Has been classified as a probable human carcinogen by the EPA.
State maximum allowable level: 0.08 ug/m3
1994 annual average in Burlington: 3.24 ug/m3

Methyl Chloride
Sources: Released during wood burning and used in chlorinated swimming pools.
Human health concerns: Repeated exposure to high amounts may effect nervous system and reproductive system, harm liver and kidneys, and effect heart rate and blood pressure. Has been classified as a probable human carcinogen by the EPA.
State maximum allowable level: 0.01 ug/m3
1994 annual average in Burlington: 1.39 ug/m3

Methylene Chloride
Sources: Found in spray cans and furniture strippers and very low levels are found in chlorinated drinking water, spice extracts, and decaffeinated coffee.
Human health concerns: Short-term inhalation of large amounts may depress the central nervous system. Has been classified as a probable human carcinogen by the EPA.
State maximum allowable level: 2.0 ug/m3
1994 annual average in Burlington: 5.20 ug/m3

Tetrachloroethylene
Sources: Solvent used extensively in dry cleaning and also used in waste incinerators.
Human health concerns: Inhaling large amounts in brief periods of time can effect central nervous system, cause dizziness, headaches, sleepiness or nausea. Has been classified as a probable human carcinogen by the EPA.
State maximum allowable level: 0.41 ug/m3
1994 annual average in Burlington: 0.62 ug/m3

1,2,4-Trimethyl Benzene
Sources: Found in paints, gasoline, surface coatings, and print pressing.
Human health concerns: Irritant to eyes and respiratory tract. Inhalation can cause headaches, fatigue, nausea, skin irritation, central nervous system depression, and asthmatic bronchitis.
State maximum allowable level: 0.15 ug/m3
1994 annual average in Burlington: 2.11 ug/m3

Mercury (methyl mercury and metallic mercury)
Sources: Released into the atmosphere during the burning of fossil fuels at coal burning power plants, industrial fossil fuel boilers, and waste incinerators. Also leeks into ecosystem from landfills.
Environmental impacts: Methyl mercury is carried from atmosphere into streams and lakes via rainwater. It then collects in lake bottom sediments where it is eaten by plankton and other bottom feeders. Humans can consume it by eating contaminated fish.
Human health concerns: Consuming mercury can effect the central nervous system, kidneys, and the development and cognitive functions of a developing fetus.
State maximum allowable level: 0.12 ug/m3
1993 annual average in Burlington: 0.00183 ug/m3

Styrene
Sources: Released during industrial processes, in vehicle exhaust, and by body shops.
Human health concerns: Central nervous system adversely impacted by exposure to large amounts in short periods of time. Has been classified as a probable human carcinogen by the International Agency for Research on Cancer.
State maximum allowable level: 512 ug/m3
1994 annual average in Underhill: 5.41 ug/m3

Acrolein
Sources: Released into atmosphere during combustion and it is a product of secondary atmospheric chemical reactions.
Human health concerns: Eye, nose, throat, and lung irritant. Extreme concentrations have been known to produce severe lung damage and can be fatal. Has been classified as a probable human carcinogen by the EPA.
State maximum allowable level (current standards are being revised): 2.5 ug/m3
1994 annual average in Rutland: 0.31 ug/m3