what is o3

Ozone (O3) is an inorganic molecule composed of three oxygen atoms. It is a pale blue gas with a distinctively pungent smell. Ozone is an allotrope of oxygen that is much less stable than the diatomic allotrope O2, breaking down in the lower atmosphere. Ozone is both a natural and a man-made product that occurs in the Earths upper atmosphere (the stratosphere) and lower atmosphere (the troposphere) . Stratospheric ozone is formed naturally through the interaction of solar ultraviolet (UV) radiation with molecular oxygen (O2) . The "ozone layer," approximately 6 through 30 miles above the Earths surface, reduces the amount of harmful UV radiation reaching the Earths surface. Tropospheric or ground-level ozone is formed primarily from photochemical reactions between two major classes of air pollutants, volatile organic compounds (VOC) and nitrogen oxides (NOx) . NOx and VOCs are precursor gases that react in the air in the presence of sunlight to produce ozone. Ozone air pollution at ground level where we can breathe it causes serious health problems.