home edit2 whole TSD November 2002 PDF format - OEHHA

3,3-DICHLOROBENZIDINE
CAS No: 91-94-1
I. PHYSICAL AND CHEMICAL PROPERTIES (From HSDB, 1994)
Molecular weight 253.1
Boiling point 402°C
Melting point
132-133°C
Vapor pressure
unknown
Air concentration conversion 1 ppm = 10.4 mg/m 3 (IARC, 1982)
II.
HEALTH ASSESSMENT VALUES
Unit Risk Factor: 3.4 E-4 (µg/m 3 ) -1
Slope Factor: 1.2 E+0 (mg/kg-day) -1
[Calculated from a cancer potency factor derived by RCHAS/OEHHA (CDHS, 1988)]
III.
CARCINOGENIC EFFECTS
Human Studies
The body of literature addressing the carcinogenicity of 3,3’-dichlorobenzidine in humans is scant.
Three retrospective epidemiological studies of occupational exposure have been conducted, focusing on
the possibility that 3,3’-dichlorobenzidine is a bladder carcinogen like its parent compound, benzidine.
None of the studies approximates exposure levels.
Gerarde and Gerarde (1974) conducted a study of 175 workers involved in the manufacture and use of
dichlorobenzidine in a chemical manufacturing plant in the United States between 1938 and 1957.
Workers were segregated from benzidine exposure. No bladder tumors were found among the
exposed workers. General population incidence of bladder tumors predicts 0-2 cases in a cohort of
this size.
Gadian (1975) conducted a study of 35 British workers exposed to dichlorobenzidine who had been
segregated from exposure to benzidine in a chemical plant from 1953 to 1973. Cumulative hours of
exposure were tabulated for all workers. No tumors were reported among the exposed workers at the
end of the study (through 1973).
MacIntyre (1975) reports on bladder tumor incidence among 225 Scottish production and service
workers, 119 of which had more than 5 years of exposure to dichlorobenzidine and 36 of which were
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