Oxides of nitrogen

Health effects

Nitrogen dioxide is known to affect the throat and the lung. The main effects are emphysema and cellular damage which reduce the efficiency of breathing. In levels encountered in polluted air, people with respiratory problems, particularly infants, may be affected.

Sources

The main source of nitrogen dioxide in the urban atmosphere is the combustion of fossil fuels (petrol, coal, gas). Nitrogen dioxide may be emitted directly from sources, but is mainly produced subsequently from a closely related chemical - nitric oxide - which is also emitted when fossil fuels are burnt.

Current standards

The current standard limit for nitrogen dioxide is 0.12 parts per million (ppm) for one hour and 0.03ppm for one year.

Goal

Maximum allowable exceedences should be one day a year for one-hour standard limit.

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