home edit2 whole TSD November 2002 PDF format - OEHHA

CHLOROFORM
CAS No.: 67-66-3
I. PHYSICAL AND CHEMICAL PROPERTIES (From HSDB, 1998)
Molecular weight 119.49
Boiling point
61° C
Melting point
-63.5° C
Vapor pressure
200 mm Hg 25º C
Air concentration conversion 1 ppm = 4.9 mg/m 3 at 25º C
II.
HEALTH ASSESSMENT VALUES
Unit Risk Factor: 5.3 E-6 (µg/m 3 ) -1
Slope Factor: 1.9 E-2 (mg/kg-day) -1
[Calculated by CDHS (1990) using a nonthreshold linear procedure. This unit risk is the
arithmetic average of unit risks generated by CDHS and Bogen et al. (1989) for renal tumors
observed in rats and mice reported by Jorgenson et al. (1985) and NCI (1976), and the
geometric mean for supporting data sets (Roe et al., 1979; Tumasonis et al., 1985).]
III.
CARCINOGENIC EFFECTS
Human Studies
There is no information currently available in the open literature which examines the potential relationship
between exposure to chloroform in an occupational setting and human cancer. However, several
studies are available which examine the relationship between trihalomethanes (THM) in drinking water
and human cancer.
Many studies have concentrated on chlorination of water and concomitant production of halogenated
carcinogens as a causative factor in human cancers. Cantor et al. (1978) compared age-adjusted
cancer mortality rates by site and sex for whites in the years 1968-71 to measures of THM and the
drinking water. A weighed linear regression model was used to predict cancer rates in 923 U.S.
counties which were over 50% urban in 1970. Reasonably strong associations between bladder cancer
and THM levels in drinking water were found after controlling for confounding by urbanization, ethnicity,
social class, and county industrialization. The association was not changed by controlling for occupation
in certain high-risk (for bladder cancer) industries nor by lung cancer rates used as a surrogate measure
for cigarette smoking. The measure of THM most associated with bladder cancer in both white males
and females was that of bromine-containing trihalomethanes (BTHM). Chloroform and total
trihalomethanes (TTHM) were not as well associated. There were inconsistent associations between
other cancer sites and THM levels. However, there was some evidence of and association of
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