Human data occupational experience

For classification purposes, reliable epidemiological data and experience on the effects of chemicals on humans (e.g. occupational data, data from accident databases) should be taken into account in the evaluation of human health hazards of a chemical. Testing on humans solely for hazard identification purposes is generally not acceptable. 

The human experience regarding exposure to dimethylhydrazines is limited to case reports describing severe but nonlethal effects following accidental acute exposures. There are limited data suggesting subclinical hepatotoxicity following subchronic occupational exposure to unspecified low levels of 1,1-dimethylhydrazine. No definite exposure concentrations or durations were available in these reports, and the data are not useful for quantitative derivation of AEGLs. 

Occupational and toxicological studies have demonstrated adverse health effects from exposure to toxic air contaminants. Data on outdoor levels of toxic air contaminants have not been available for most communities in the United States, making it difficult to assess the potential for adverse human health effects from general population exposures. Models and new experiments provide a great amount of new data (Woodruff et al., 1998). 

This is because of the wide range of exposure levels that workers experience and the difficulty in estimating exact levels from area sampling done at different times and with different methods. Moreover, historical exposure data are lacking in most of the studies, and occupational studies frequently encompass concomitant exposures to other chemicals. However, decreased survival associated with ventricular fibrillation in rats has been noted following oral exposure to carbon disulfide (Hoffman 1987). There are no studies available that address death following dermal exposure in humans or animals. 

The objective of the work described here was to examine whether a similar approach can be used to assess chemical uptake into the skin in vivo from contaminated soil. It is now well recognized that human skin contact with contaminated soil can represent an important route of exposure to toxic compounds in occupational, environmental, and recreational settings. Data on the dermal uptake of chemicals from soil, especially in vivo, are limited, however, and those that do exist may underrepresent the true risk. This is because the amount of soil applied to skin in these experiments (1) greatly exceeds the mass of soil adhering to skin during a typical exposure (U.S. Environmental Protection Agency, 2001) and (2) may have provided multiple soil layers that do not contribute equally to dermal absorption (Bunge and Parks, 1998). 

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