||Air Quality Data Analysis System for Interrelating Effects, Standards, and Needed Source Reductions: Part 5. NO2 Mortality in Mice.
Larsen, Ralph I. ;
Gardner, Donald E. ;
Coffin, David L. ;
||Environmental Sciences Research Lab., Research Triangle Park, NC.
Nitrogen dioxide ;
Air pollution ;
Laboratory animals ;
Mathematical models ;
Air pollution effects(Animals)
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Mice have been exposed for durations of 6 min to 1 yr to NO2 concentrations of 0.5 to 28 ppm. Exposed mice and control mice have then inhaled an aerosol containing a lung pathogen and the excess mortality of exposed mice (compared with control mice) has been determined. A mathematical model (similar to a previously-developed model for vegetation injury) has been developed from an analysis of the resulting data to calculate expected excess mortality as a function of NO2 concentration and exposure duration. Excess mortality was found to be proportional to NO2 concentration multiplied by exposure duration raised to the 0.33 power. The concentration (c) expected to cause a certain mortality level (z), as a function of the hours of exposure (t), can be expressed as c = 9.55(2.42)zt-0.33. The model has been used to calculate expected excess mortality (1.1%) if mice had inhaled the ambient NO2 concentrations measured in downtown Chicago for each hour of 1974 (1 yr arithmetic mean of 0.05 ppm, the same as the present national ambient standard). NO2 affects mice much more than it affects men. If men were exposed to the NO2 dosages studied here, increased morbidity rather than increased mortality would be expected.