Table 1.
Common health impacting air pollutants, grouped by origin
| Air Pollutant | Typical Sources |
|---|---|
| 1: Predominantly Outdoor Air Pollutants | |
| Sulfur dioxide (SO2) | Fuel combustion, smelters |
| Ozone (O3) | Generated via photochemical reactions in the atmosphere from nitrogen oxides (NOx) and volatile organic compounds (VOCs), as well as natural processes (e.g., stratosphere) |
| Arsenic (As), Chromium (Cr) | Coal combustion fine particulate matter (PM2.5) |
| Nickel (Ni), Vanadium (V) | Residual oil combustion fine particulate matter (PM2.5) |
| 2. Predominantly Indoor Air Pollutants | |
| Radon | Building materials (concrete, stone), ground water |
| Asbestos, mineral, synthetic fibers | Fire-retardant, acoustic, thermal, or electrical insulation |
| Biological contaminant | Infections, dust mites, animal dander, allergens |
| 3: Both Outdoor and Indoor Air Pollutants | |
| Suspended particulate matter (PM) | |
| Fine PM (PM2.5) | Outdoor: Fossil fuel combustion, gas-to-particle conversion, biomass burning Indoor: Biomass fuel combustion, tobacco smoking |
| Coarse PM (PM2.5–10) | Outdoor: Dust storms, windblown soil, pollens Indoor: Mold spores, re-suspended dust |
| Nitrogen dioxide (NO2) | Outdoor: Fossil fuel combustion (e.g., diesel vehicle emissions) Indoor: Tobacco smoking, gas cooking stoves |
| Volatile organic compounds (VOCs) | Outdoor: Petrochemical solvents, evaporated fuels, biogenics Indoor: Fuel and paint vapors, combustion, adhesives, cosmetics, solvents, particleboard (formaldehyde), insulation, furnishings, tobacco smoke |
| Carbon monoxide (CO) | Outdoor: Fossil fuel combustion, biomass burning, wildfires Indoor: Tobacco smoke, unvented gas heaters |
| Lead (Pb) | Outdoor: Industrial emissions, leaded fuel combustion, lead processing Indoor: Leaded paint wear |
| Mercury (Hg) | Outdoor: Coal combustion, ore refining Indoor: Fungicides in paints, thermometer breakage, ritual use |
| Pesticides | Outdoor: Agricultural Indoors: Home applications of herbicides, insecticides, fungicides, etc. |
| Ammonia | Outdoor: Livestock yards Indoor: Metabolic activity, cleaning products |
| Hazardous air pollutants (HAPs) (e.g., benzene, 1,3-butadiene, formaldehyde, acids) | Outdoor: Incomplete combustion, chemical processing Indoor: Solvent use |
Adapted from: World Health Organization (WHO). Estimating Human Exposures to Air Pollutants. Offset Pub. No. 69. Geneva: World Health Organization; 1982 and International Agency for Research on Cancer (IARC). Outdoor Air Pollution. Volume 109. Lyon: International Agency for Research on Cancer; 2013.