title: Studies of air-borne pollutant levels.
mesh_terms: D000397:Air Pollution / Q000032:analysis*; D006838:Hydrocarbons / Q000032:analysis*; D007854:Lead / Q000032:analysis*; D010084:Oxidation-Reduction; D010126:Ozone / Q000032:analysis; D010414:Pennsylvania; D010777:Photochemistry; D013997:Time Factors
chemical_list: D006838:Hydrocarbons; D007854:Lead; D010126:Ozone