Black Carbon or soot, is a type of dark particulate matter produced by the incomplete combustion of fossil fuels, wood, and other biofuels. It commonly originates from motor vehicles, residential stoves/fireplaces and forest fires.  Black Carbon can be an irritant to lung health, inflaming the lungs and aggravating respiratory illnesses such as bronchitis and asthma.

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Nitrogen Dioxide

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NMVOC is a general term that refers to any of a number of compounds called hydrocarbons.  Hydrocarbons are compounds mainly composed of carbon and hydrogen.  All compounds that fall under the group called Total Hydrocarbons are considered VOCs.  Because THC includes such a wide variety of compounds, these compounds are usually present in the air because of the wide variety of common sources such as automobile exhaust.  Ambient levels of THC are typically 1000 ppb or less.

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Sulfur dioxide is a colorless gas.  At elevated concentrations, it has a sharp odor.  The majority of SO2 is from manmade activities associated with burning fossil fuels in power plants and other industrial processes.  Naturally occurring sources of sulfur dioxide include volcanic eruptions.  Sulfur dioxide is used in various chemical reactions to make other chemical products such as sulfuric acid.  Sulfur dioxide is also used as a food preservative for various dried fruits, and historically was used as a refrigerant before the development of chlorofluorocarbons.^2,3

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