Nitrogen dioxide

CAS RN:10102-44-0

Exposure Summary

Nitrogen dioxide is an ubiquitous product of combustion, occurring in exhaust from motor vehicles, emissions from the combustion of stationary fuel sources such as coal, oil or natural gas and various industrial sources. Atmospheric oxidation of nitric oxide (NO) may also lead to the formation of nitrogen dioxide. Natural sources, such as forest fires, atmospheric lightning discharges and the biogenic oxidation of nitrogen containing compounds in soils may also release quantities of nitrogen dioxide directly to the environment. Nitrogen dioxide's production and use as an intermediate in the manufacture of nitric acid and as an oxidizing agent may also lead to its release to the environment through various waste streams. If released to air, a vapor pressure of 900 mm Hg at 25 deg C indicates nitrogen dioxide will exist solely as a gas in the ambient atmosphere. Gas-phase nitrogen dioxide is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals with an estimated atmospheric half-life of 35 hours. Nitrogen dioxide dissolves with water to form nitric acid, which is a major constituent of acid rain. Nitrogen dioxide compound is expected to undergo direct photolysis in the environment, ultimately leading to the production of ozone and smog conditions in the lower troposphere. If released to soil, this compound is expected to decompose to nitric acid in moist soil surfaces. Nitrogen dioxide is expected to volatilize from dry soil surfaces based upon its vapor pressure. If released into water, nitrogen dioxide is expected to decompose to nitric acid. Occupational exposure to nitrogen dioxide may occur through inhalation and dermal contact with this compound at workplaces where nitrogen dioxide is produced or used or where combustion processes are important. The general population may be exposed to nitrogen dioxide through the inhalation of ambient air and by smoking tobacco products. (SRC)
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