Ozone: The unstable triatomic form of oxygen, O3. It is a powerful oxidant that is produced for various chemical and industrial uses. Its production is also catalyzed in the ATMOSPHERE by ULTRAVIOLET RAY irradiation of oxygen or other ozone precursors such as VOLATILE ORGANIC COMPOUNDS and NITROGEN OXIDES. About 90% of the ozone in the atmosphere exists in the stratosphere (STRATOSPHERIC OZONE).Oxidants, Photochemical: Compounds that accept electrons in an oxidation-reduction reaction. The reaction is induced by or accelerated by exposure to electromagnetic radiation in the spectrum of visible or ultraviolet light.Air Pollutants: Any substance in the air which could, if present in high enough concentration, harm humans, animals, vegetation or material. Substances include GASES; PARTICULATE MATTER; and volatile ORGANIC CHEMICALS.Ozone Depletion: A shift in the balance between production and destruction of STRATOSPHERIC OZONE that results in a decline of the amount of OZONE in the lower stratosphere.Air Pollution: The presence of contaminants or pollutant substances in the air (AIR POLLUTANTS) that interfere with human health or welfare, or produce other harmful environmental effects. The substances may include GASES; PARTICULATE MATTER; or volatile ORGANIC CHEMICALS.Atmosphere: The gaseous envelope surrounding a planet or similar body. (From Random House Unabridged Dictionary, 2d ed)Nitrogen Dioxide: Nitrogen oxide (NO2). A highly poisonous gas. Exposure produces inflammation of lungs that may only cause slight pain or pass unnoticed, but resulting edema several days later may cause death. (From Merck, 11th ed) It is a major atmospheric pollutant that is able to absorb UV light that does not reach the earth's surface.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.Chlorine Compounds: Inorganic compounds that contain chlorine as an integral part of the molecule.Smog: A mixture of smoke and fog polluting the atmosphere. (Dorland, 27th ed)Environmental Exposure: The exposure to potentially harmful chemical, physical, or biological agents in the environment or to environmental factors that may include ionizing radiation, pathogenic organisms, or toxic chemicals.Particulate Matter: Particles of any solid substance, generally under 30 microns in size, often noted as PM30. There is special concern with PM1 which can get down to PULMONARY ALVEOLI and induce MACROPHAGE ACTIVATION and PHAGOCYTOSIS leading to FOREIGN BODY REACTION and LUNG DISEASES.Inhalation Exposure: The exposure to potentially harmful chemical, physical, or biological agents by inhaling them.Sulfur Dioxide: A highly toxic, colorless, nonflammable gas. It is used as a pharmaceutical aid and antioxidant. It is also an environmental air pollutant.Stratospheric Ozone: Ozone in the Earth's stratosphere. It is produced continuously by the action of solar ULTRAVIOLET RAYS on oxygen in the stratosphere. The stratospheric ozone (especially at the ozone layer) blocks much of the solar UV radiation of wavelengths of 320 nanometers or less from being transmitted to lower ATMOSPHERE of the Earth.Chlorofluorocarbons: A series of hydrocarbons containing both chlorine and fluorine. These have been used as refrigerants, blowing agents, cleaning fluids, solvents, and as fire extinguishing agents. They have been shown to cause stratospheric ozone depletion and have been banned for many uses.Indigo Carmine: Indolesulfonic acid used as a dye in renal function testing for the detection of nitrates and chlorates, and in the testing of milk.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Pentanes: Five-carbon saturated hydrocarbon group of the methane series. Include isomers and derivatives.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Disinfection: Rendering pathogens harmless through the use of heat, antiseptics, antibacterial agents, etc.Cities: A large or important municipality of a country, usually a major metropolitan center.Disinfectants: Substances used on inanimate objects that destroy harmful microorganisms or inhibit their activity. Disinfectants are classed as complete, destroying SPORES as well as vegetative forms of microorganisms, or incomplete, destroying only vegetative forms of the organisms. They are distinguished from ANTISEPTICS, which are local anti-infective agents used on humans and other animals. (From Hawley's Condensed Chemical Dictionary, 11th ed)Weather: The state of the ATMOSPHERE over minutes to months.Bronchoalveolar Lavage Fluid: Washing liquid obtained from irrigation of the lung, including the BRONCHI and the PULMONARY ALVEOLI. It is generally used to assess biochemical, inflammatory, or infection status of the lung.Air Movements: The motion of air currents.Respiratory Tract Diseases