Aviation Emissions and Air Quality Handbook  • Electrical Usage  –  Emissions associated with the  onsite generation of electricity using  coal, oil, or natural gas;  • Refrigerants  –  A range of chemicals used for refrigeration and air conditioning that are  comprised of substances possessing  high global warming characteristics (e.g., Freon,  chlorofluorocarbons, etc.); and  • Waste Management  –  Emissions associated with the solid waste gene rated and the  recycling and solid waste disposal practices employed by the airport.  There are a variety of air pollutants associated with aviation-related activities that can potentially  have an impact on the environment. This section identifies and discusses these pollutants which  consist of EPA’s criteria pollutants and their precursors, GHGs, and HAPs.  As discussed in  Section 2  ( Regulatory Framework ), the EPA has established the NAAQS under  the CAA for six common air pollutants known as “criteria pollutants”. These air pollutants  consist of CO, Pb, NO $_{2}$, O$_{3}$, PM, and SO $_{2}$. The criteria pollutants are generally described in  Table 3-1  ( EPA Criteria Air Pollutants ).  3.2.1.  Criteria Pollutants  3.2.  Pollutants of Concern  Table 3-1. EPA Criteria Air Pollutants  Pollutant  General Characteristics  Carbon  Carbon monoxide is a colorless, odorless, tasteless gas that is a product of incomplete combustion of  Monoxide  organic materials. In the ambient environment, it may temporarily accumulate into localized “hot - (CO)  spots”, especially in calm weather conditions and in the wintertime when  CO forms easily and i s chemically most stable.  In humans, CO can be absorbed by the lu ngs and react with hemoglobin to reduce carrying capacity of the blood. At elevated concentrations CO can have cardiovascular and  central  nervous system effects.  Lead  Lead is a heavy metal that occurs in the atmosphere as lead oxide aerosol or lead dust. Lead is most  (Pb)  commonly associated with emissions from industrial sources including production, smelting, and battery manufacturing.  Most avgas (general a viation fuel for pisto engines) also contains Pb. Lead is a highly stable compound that accumulates in the environment  and in living organisms.  In humans, Pb exposures can interfere with the maturation and development of red blood cells, affect  liver and kidney functions, and cause nervous system damage.  Nitrogen  Nitrogen dioxide is a reddish-brown to dark brown gas with an irritating odor . NO$_{2}$, nitric oxide  Dioxide  (NO), and the nitrate radical (NO $_{3}$) are collectively called oxides of  nitrogen (NO$_{x}$). These three (NO$_{2}$)  compounds are interrelated, often changing from one form principal man-made source of NO x  is fuel combustion in motor vehicles and power plants aircraft also contributing. NO$_{2 }$ emissions from these sources are highest duri ng high-temperature  combustion conditions. Reactions of NO x  with other chemicals (such as VOCs) can lead to 3  formation and acidic precipitation.  Additionally, secondary PM can be  formed within t atmosphere from precu rsor gases, such as NO $_{x}$, through gas-phase photochemical reactions through liquid phase reactions in clouds and fog droplets.  In humans, NO$_{2 }$can be a lung irritant capable of producing pulmonary edema at high concentrations  and can lead to other respiratory illnesses such as bronchitis and pneumonia.  13$_{ }$