(VCCEP) Tier 1 Pilot Submission for BENZENE - Tera

Table 7.43: Recently Published Data on Occupational Exposure to Benzene
Occupation
Benzene VCCEP Submission
March 2006
145
Average 8-hour
TWA
Concentration
(ppm)
Reference
Chemical Manufacturing 0.22 Collins et al., 1997
Aircraft Maintenance Personnel – Military 0.006 - 0.05
Wildland Firefighter – General Crew 0.003 – 0.004
Wildland Firefighter – Engine Operator 0.13
Lemasters et al., 1997,
1999
Reinhart and Ottmar,
2000
Reinhart and Ottmar,
2000
Municipal Firefighter 0.4 - 3.4
Austin, et al 2001a,b;
Bolstad-Johnson,et al,
2000
Incinerator 0.005 Thrall et al., 2001
Because the data suggest that except for the municipal fire fighter, benzene exposures in these
occupations are either similar to or much lower than that of a worker employed in the benzene
production industry, occupational exposures to benzene have been quantified using the data
from the Consortium. The occupational exposure for a prospective parent employed in the
benzene manufacturing industry is assumed to be 0.11 ppm as typical 8-hour TWA exposure
and 0.39 ppm as a high-end 8-hour TWA exposure; the mean and 95 th percentile in Table 7.41.
Dermal Exposures
Occupational chemical exposure studies typically do not report dermal exposure due to the
difficulty of properly estimating the contribution of the dermal route, and very few in vivo human
studies of dermal exposure to solvents have been published (Kezic et al., 2001). EPA’s
“Dermal Exposure Assessment: Principles and Applications” provides guidance related to
assessing dermal exposure. This document, as well as most other published guidance on
dermal exposure focuses on two pathways: direct contact with water and direct contact with soil.
Unless a site has been contaminated, however, most workers’ dermal exposure to benzene will
occur during use or production of chemical products.
The basic theory of calculating the intake resulting from dermal contact with a substance is that
the outermost layer of the epidermis (the surface layer of dead skin cells) provides the major
barrier to absorption of a chemical into the blood stream. The percent absorbed (ABS) is the
fraction of a dose applied to the skin that is absorbed across the outer layer of the epidermis in
a specified time. The dermal intake could then be calculated by multiplying the absorption
factor by concentration of the chemical in its carrier vehicle, the area of skin in contact with the
chemical and the thickness of the vehicle on the skin. Absorption factors for chemicals with
high vapor pressures, such as benzene, are generally low due to their high volatility. Absorption
factors for benzene are summarized on Table 7.44.