Biological Effects of Short, High-Level Exposure to Gases: Nitrogen Oxides.
Phase rept. May 79-May 80,
ENVIRO CONTROL INC ROCKVILLE MD
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This report presents an analysis of the available literature describing the health and performance effects of exposure to nitrogen oxides NOx. The US Armys concern is with high-level, short-term exposures that may exceed present threshold limit values of the American Conference of Governmental Industrial Hygienists 5 ppm 9 mgcum as a TWA intended changes are a TWA of 3 ppm 5.4 mgcum with a short term exposure limit of 5 ppm 9 mgcum for 15 minutes. Dose-response relationships were developed for intensities of exposure from the highest fatal level to thresholds of minimal response. It is concluded that NOx can in general be equated to nitrogen dioxide NO2 because this is much more toxic than the only other oxide of importance, nitric oxide NO, which oxidizes to NO2 in air. If NO is present in equal or greater concentration, an allowance for its effect is recommended. NO2 exhibits mainly two sets of toxicological characteristics immediate irritancy and delayed, cumulative tissue damage. Proven effects are mainly on the respiratory tract. Intense exposures result in death, hospitalization with recovery, or severe responses not requiring hospitalization. Survivors may be free from permanent effects. This range covers concentrations from 20 ppm 38 mgcum to 200 ppm 376 mgcum and up, for single exposures of a few minutes up to 1 hour.