Internal combustion engine the atmosphere by the reaction of and volatile organic compounds in the presence of sunlight. Ground-level ozone is harmful to human health and the environment. Though the same chemical substance, ground-level ozone should not be confused with stratospheric ozone, or the ozone layer, which protects the earth from harmful ultraviolet rays. Carbon fuels contain sulfur and impurities that eventually produce sulfur monoxides (SO) and sulfur dioxide (SO) in the exhaust, which promotes acid rain. In the United States, nitrogen oxides, PM, carbon monoxide, sulphur dioxide, and ozone, are regulated as criteria air pollutants under the Clean Air Act to levels
Nitrogen dioxide This reaction is negligibly slow at low concentrations of NO characteristic of the ambient atmosphere, although it does proceed upon NO uptake to surfaces. Such surface reaction is thought to produce gaseous HNO (often written as HONO) in outdoor and indoor environments. Nitric acid decomposes slowly to nitrogen dioxide by the overall reaction: The nitrogen dioxide so formed confers the characteristic yellow color often exhibited by this acid. is used to generate anhydrous metal nitrates from the oxides: Alkyl and metal iodides give the corresponding nitrites: is introduced into the environment by natural causes, including entry from the stratosphere, bacterial