Ambient Air Exposures

The levels of atmospheric lead are gradually decreasing, mainly as a result of the decreased use of lead in gasoline. As is expected, urban atmospheres contain higher lead concentrations than rural atmospheres. In 1974, the arithmetic mean of urban lead concentrations was 0.89 pg/m, as compared to the rural mean of 0.11 pg/m. When rural locations are classified according to their proximity to large population centers, the lead concentrations decrease with distance from the urban environment [73]. 

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Brysson and co-workers (7) conducted a study in St. Louis, Missouri, on the effects of urban air pollution on the tensile strength of cotton duck material. Samples were exposed at seven locations for up to 1 year. Figure 9-3 shows the relationship between tensile strength and pollutant exposure. For two levels of ambient air exposure, the materials exhibited less than one-half their initial tensile strength when exposed to air pollution for 1 year. 

Air Contaminants (29 CFR 1910.1000). OSHA requires that employees who must work in or near industrial operational areas with an ambient air exposure limit above a set level wear appropriate respiratory protection. The permissible exposure levels (PELs) of major concern for colorant and additive formulators are as follows ... 

All ex situ prepared catalysts must be activated prior to experiments to remove residual contamination from the preparation procedure and hydrocarbons from ambient air exposures. Such activations normally include an oxidation step followed by a reduction step. The pretreatments may be... 

Exposure (concentrations and concentration fluctuations in the ambient air, exposure time, physical exertion). The alveolar concentration of solvents or the difference between air and blood concentration levels determine the diffusion process into alveolar blood vessels. Physical exertion influences lung parameters, especially ventilation, and consequently alveolar and blood concentrations. 

Normalized conductivity versus days of ambient air exposure for l2-doped, S-(CH)x film ( ), N-(CH)x film ( ) and stretched 70 X 220 % , 330 and 550 % a. These films were prepared by washing, stretching and, finally, doping. 

Exposure (concentrations and concentration fluctuations in the ambient air, exposure time, physical exertion). The alveolar concentration of solvents or the differ-... 

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