National Geographic : 1987 Apr
NO (nitric oxide): from motor vehi cles, coal and oil furnaces; readily oxi dizes to NO,. NO 2 (nitrogen dioxide): formed in sunlightfrom NO; produces ozone; causes bronchitis,lowers resistance to influenza. 03 (ozone): formed in sunlightfrom nitrogenoxides and hydrocarbons; irritateseyes, aggravatesasthma. OH (hydroxyl radical):formed in sunlightfrom hydrocarbonsand nitro gen oxides; reacts with othergases to form acid droplets. PAN (peroxyacetyl nitrate): formed in sunlightfrom nitrogen oxides and hydrocarbons;irritateseyes, aggra vates asthma. Pb (lead): from motor vehicles, smelt ers; causes braindamage, high blood pressure, impairsgrowth. SiF4 (silicon tetrafluoride): from chemical plants; irritateslungs. SO 2 (sulfur dioxide): from coal and oil furnaces, smelters; obstructs breathing,irritateseyes.