home edit2 whole TSD November 2002 PDF format - OEHHA

BENZENE
CAS No: 71-43-2
I. PHYSICAL AND CHEMICAL PROPERTIES (from HSDB, 1998)
Molecular weight 78.1
Boiling point
80.1° C
Melting point
5.5° C
Vapor pressure
100 mm Hg @ 26.1° C
Air concentration conversion 1 ppm = 3.2 mg/m 3 @ 25° C
II.
HEALTH ASSESSMENT VALUES
Unit Risk Factor 2.9 E-5 (µg/m 3 ) -1
Slope Factor 1.0 E-1 (mg/kg-day) -1
[Human occupational exposure leukemia incidence (Rinsky et al., 1981); excess risk calculated
using a Weighted Cumulative Exposure/relative risk procedure (CDHS, 1984).]
III.
CARCINOGENIC EFFECTS
Human Studies
Case studies of workers exposed to benzene were responsible for generating the hypothesis that
benzene causes leukemia in humans. Epidemiological studies performed to test the hypothesis
supported the causal nature of the benzene-leukemia association. A summary of some of the more
salient features from 23 major epidemiologic studies are shown in Table 1.
Table 1:
Epidemiologic studies of carcinogenicity in humans.
Study Population Studied Duration Results 1
Tabershaw Cooper
Assoc. (1974)
Thorpe (1974)
Aksoy et al. (1974,
1976)
McMichael et al.
(1976)
Vigliani (1976)
petroleum industry
Increase in rate of lymphomas (NS)
workers
petroleum industry 1962-1972 Leukemia SMR=121 (NS) (SMR in worker controls = 60)
workers
Shoemakers exposed 1967-1975 Annualized crude rate of acute leukemia 2-fold greater
to 210-650 ppm
than expected
benzene
rubber industry
Excess in mortality from: chronic lymphatic leukemia,
workers
myelogenous leukemia, lymphosarcoma
patients with benzene
Leukemia incidence:
hemopathy;
1942-1975 11/66
exposures estimated at 1959-1974 13/135
200-500 ppm
Estimated relative risk (RR)=20
82