Occupational chemicals, dermal absorption estimates

Occupational exposures to 2-butoxyetlranol and 2-butoxyethanol acetate also occur primarily via inhalation or dermal absorption. Estimates from the National Occupational Exposure Survey (NOES) conducted by the National Institute of Occupational Safety and Health (NIOSH) indicate that from 1981 to 1983 more than 2 million workers were potentially exposed to 2-butoxyethanol, and more than 150,000 workers were potentially exposed to 2-butoxyethanol acetate (NIOSH 1989b). In addition to occupational exposures related to the production, processing, or handling of these chemicals, workers may be exposed to 2-butoxyethanol and 2-butoxyethanol acetate in a wide variety of occupations in which products containing these compounds are used. These occupations include janitors and cleaners, painters, mechanics, nurses and health aids, construction workers, printing machine operators, and furniture and wood finishers. 

Workers in industrial facilities manufacturing or using hexachloroethane as an intermediate in the manufacture of other products may be exposed to the chemical by inhalation or dermal absorption. In addition, military or civilian personnel working with smoke or pyrotechnic devices may be exposed. Based on information collected for the National Occupational Exposure Survey, the National Institute for Occupational Safety and Health (NIOSH) estimates that 8,515 workers were potentially exposed to hexachloroethane (NOES 1991). 

As an alternative to the assumption of a one-time exposure for 1,000 h at the time of facility closure, permanent occupancy of a disposal site following loss of institutional control could be assumed (see Section 7.1.3.4). The assumption of chronic lifetime exposure would affect the analysis for hazardous chemicals that induce deterministic effects only if estimated intakes due to additional pathways, such as consumption of contaminated vegetables or other foodstuffs produced on the site, were significant. Based on the results for lead in Table 7.8, an intake rate from additional pathways of about 50 percent of the assumed intake rate by soil ingestion, inhalation, and dermal absorption would be sufficient to increase the deterministic risk index above unity. The importance of additional pathways was not investigated in this analysis, but they clearly would warrant consideration. The increase in exposure time during permanent occupancy does not otherwise affect the analysis for chemicals that induce deterministic effects, provided RfDs are appropriate for chronic exposure, because chronic RfDs incorporate an assumption that the levels of contaminants in body organs relative to the intake rate (dose) are at steady state. 

Okrent and Xing (1993) estimated the lifetime cancer risk to a future resident at a hazardous waste disposal site after loss of institutional control. The assumed exposure pathways involve consumption of contaminated fruits and vegetables, ingestion of contaminated soil, and dermal absorption. The slope factors for each chemical that induces stochastic effects were obtained from the IRIS (1988) database and, thus, represent upper bounds (UCLs). The exposure duration was assumed to be 70 y. Based on these assumptions, the estimated lifetime cancer risk was 0.3, due almost entirely to arsenic. If the risk were reduced by a factor of 10, based on the assumption that UCLs of slope factors for chemicals that induce stochastic effects should be reduced by this amount in evaluating waste for classification as low-hazard (see Section 7.1.7.1), the estimated risk would be reduced to 0.03. Either of these results is greater than the assumed limit on acceptable risk of 10 3 (see Table 7.1). Thus, based on this analysis, the waste would be classified as high-hazard in the absence of perpetual institutional control to preclude permanent occupancy of a disposal site. 

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