Geoscience Reference
In-Depth Information
Acute inhalation and oral exposure to high levels of CT have been observed
primarily to damage the liver (swollen, tender liver; changes in enzyme levels; and
jaundice) and kidneys (nephritis, nephrosis, proteinuria) of humans. Depression of
the CNS also has been reported. Symptoms of acute exposure in humans include
headache, weakness, lethargy, nausea, and vomiting (EPA
2000a
). Occasional
reports have noted the occurrence of liver cancer in workers exposed to CT by
inhalation; however, the data are not sufficient to establish a cause-and-effect
relationship. Liver tumors have developed in rats and mice exposed to CT, by
experimentally placing the chemical in their stomachs (ATSDR
1994
; IARC
1972
,
1982
). The EPA has classified CT as a Group B2, probable human carcinogen
(EPA
2000a
).
Chlorinated ethanes and ethylenes comprise ethyl chloride, ethylene dichloride
(EDC) (1,2-dichloroethane), vinyl chloride, trichloroethylene (TCE), perchloro-
ethylene (PCE, also called tetrachloroethylene), and several CFCs. Some of the
major uses of these compounds are as degreasing agents, dry-cleaning solvents,
building blocks for manufacturing of polymers (e.g., PVC, ethyl cellulose), and
raw material for the production of tetraethyl lead and CFCs. We discuss EDC,
TCE, and PCE as examples of this group.
EDC is used primarily in the production of vinyl chloride monomer (HSDB
2000
). It also is an intermediate in the manufacture of trichloroethane and flu-
orocarbons and used as a solvent. In the past, EDC was used as a gasoline additive
and a soil fumigant. The reported toxicological effects on exposure of workers to
levels of 10-37 ppm were nausea, vomiting, dizziness, and unspecified blood
changes (Brzozowski et al.
1954
). In other studies, adverse CNS and liver effects
were reported in workers occupationally exposed to concentrations of 16 ppm
EDC (Kozik
1957
) and less than 25 ppm (Rosenbaum
1947
). EDC is reasonably
anticipated to be a human carcinogen based on experiments on animals (IARC
1987
). When administered by gavage, 1,2-dichloroethane increased the incidence
of hepatocellular carcinomas in male mice, mammary gland adenocarcinomas and
endometrial stromal neoplasms of the uterus in female mice, and lung adenomas in
mice of both sexes. Furthermore, gavage administration of 1,2-dichloroethane
increased the incidence of squamous cell carcinomas of the forestomach, subcu-
taneous fibromas, and hemangiosarcomas in male rats and mammary gland ade-
nocarcinomas in female rats. No adequate data were available to evaluate the
carcinogenicity of 1,2-dichloroethane in humans (IARC
1987
).
The first documented synthesis of TCE was in 1864, and by the early 1900s, a
manufacturing process was initiated, becoming a full industrial process by the
1920s (Mertens
2000
). The main use of TCE is metal degreasing (over 90 % of
production and consumption). TCE also was used extensively for dry cleaning and,
in the past, as an extraction solvent for natural fats and oils for food, cosmetic, and
drug production (e.g., extraction of palm, coconut, and soybean oils; decaffeination
of coffee; isolation of spice oleoresins) (Doherty
2000a
; Linak et al.
1990
).
Additional applications of TCE are as components in adhesive and paint stripping
formulations, as a low-temperature heat-transfer medium, as a nonflammable
solvent carrier in industrial paint systems, and as a solvent base for metal
