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<br /> at concentrations ranging from 1.0 to X35 ppm.These disturbances Trichloroethylene came under suspicion as a possible carcinogen
<br /> increased with the length of exposure(up to five years or more),and as a result of a report from the National Cancer Institute"31 that oral
<br /> were reported to be distinctly more frequent when average trichloro- administration of trichloroethylene resulted in hepatocellular car-
<br /> ethylene concentrations exceeded 40 ppm. cinomas in mice. In this bioassay, male and female rats (Osbome-
<br /> Barododej and Vyskocil'191 also recommended a limit of about 40 Mendel)and mice(6600)were intubated with trichloroethylene
<br /> ppm,finding signs and symptoms of chronic trichloroethylene poison- daily for 18 months with an observation period of 3 to 6 months
<br /> ing including intolerance to alcohol,tremors,giddiness,and anxiety following treatment. Rats were given doses at either 1000 mg/kg or
<br /> at an exposure above 40 ppm. 500 mg/kg, 5 times a week. Male mice were given 2400 or 1200
<br /> Lilis and co-workers 1201 reported that workers exposed at concen- mg/kg and female mice 1800 mg/kg or 900 mg/kg doses 5 times/
<br /> " trations averaging about 10 ppm (12°/° of the tests showed values week. Hepatocellular carcinomas were not seen in the rats; 30 of
<br /> { about 40 ppm)complained of headache, dizziness,and sleepiness. the 98 (30.6%)micegiven the low dose,and 41 of the 95 (43.2%)
<br /> a The symptoms reported from these industrial exposure situations mice given the high dose developed hepatocellular carcinomas. Only
<br /> are highly subjective and are common findings in control individ- one(2.5%)of the 40control mice developed carcinoma,an unusually
<br /> uals with no chemical exposure.Yet,the consistency-of these reports low incidence for this tumor in this strain of mice which often has
<br /> suggests the possibility of some subjective complaints as concentra- a 40% background incidence.
<br /> tions exceed about 50 ppm. In these industrial environments, ex- Maltoni completed a lifetime chronic study"" in Sprague-Dawley
<br /> posure concentrations are variable and the effects reported may be rats Which did not indicate any carcinogenic effect Trichloroethy-
<br /> associated with transient, high concentrations rather than with the lene was administered in olive oil by gavage 4 to 5 time/week for,
<br /> time-weighted average value during the work shift. Furthermore, one year at dose levels of 50 and 250 mg/kg body weight.
<br /> worker populations are variable with respect to age, health status, When trichloroethylene was applied to mouse skin by several
<br /> nutrition,and intake of alcohol,caffeine,and medicinals,all factors methods, Van Duuren et aP 51 found low doses to be inactive. One
<br /> which might influence worker response to TCE. mg/kg of the material was applied three times weekly to the dorsal
<br /> In contrast,controlled laboratory studies with relatively homogen- skin with or without phorbol myristate acetate as a promotor. It was
<br /> eous populations of young, healthy subjects have shown less effect also injected subcutaneously at weekly intervals at a dosage of 0.5
<br /> of TCE than reported in the industrial setting.The air concentrations mg/kg with no significant effect and intragastrically with no increase
<br /> of TCE in these studies are, of course, more precisely known and in tumors of the forestomach.
<br /> relatively constant throughout the exposure. Stopps and McLaugh- In an inhalation study, rats, mice, and Syrian hamsters were ex-
<br /> lin'21 exposed human volunteers to 100 ppm of trichloroethylene posed 6 hours/day, 5 days/week for 18 months to either 0, 100,or
<br /> and found no changes in various performance tests,but noted some 500 ppm of pure trichloroethylene stabilized only with an amine
<br /> changes at higher concentrations. Stewart and associates1221 reported base. The authors concluded,
<br /> that in an early study, volunteers exposed-to 200 ppm of trichloro- "No significant increase in tumor formation was observed in any
<br /> ethylene for 7 hours/day reported mild responses such as slight fatigue species or dosing group,except in malignant lymphomas,which
<br /> and sleepiness on the fifth day of exposure. There were no meas- were increased in female mice in the following incidence rates:
<br /> urable objective responses and no control studies were included. g/29(controls), 17/30(100 ppm),and 18/28(500 ppm). Whether
<br /> Stewart et al did not confirm these effects in subsequent, better or not this high occurrence of lymphomas, which is peculiar to
<br /> controlled studies. In the later studies, male subjects were exposed this strain of mice (NMRI) has any relationship to tri-exposure
<br /> for
<br /> 20, or ppm and female subjects to 100 ppm 7.5 hours/day cannot be decided upon by the present experiment. It is con-
<br /> cluded that from these findings no indication for a carcinogenic
<br /> " . .the data obtained do not prove that TCE has a well defined potential of pure trichloroethylene can be deduced.'"361
<br /> deleterious behavioral effect upon humans at either 100 or 200 A recently completed study'371 investigated the possible differences
<br /> ppm in the atmosphere for the 7.5 hr per day,5 days/week. . .The in metabolism and pharmacokinetics between mice and rats exposed
<br /> 1 ppm concentration probably has a three to four-fold mar- to tricholoroethylene. A comparison of metabolized trichloroethy-
<br /> lene on a weight basis indicates that the mouse metabolizes 2.2 times
<br /> The authors stress the importance of controlling for learning by the more than the rat at 10 ppm and 3.6 times at 600 ppm. Hepatic
<br /> test subjects, a phenomenon which has not been appreciated ade- macromolecular binding was greater in the mouse than in the rat.
<br /> quately in many other studies including the earlier one by Stewart's The binding data suggest that tumor formation in the mouse exposed
<br /> group. to trichloroethylene occurred via a nongenetic mechanism and tumors
<br /> Triebig et 0141 exposed seven healthy volunteers to 100 ppm of are not expected if liver injury does not occur.
<br /> trichloroethylene for five days and observed no impairment in mental There is no evidence in three epidemiological studies completed
<br /> or psychological capacities. On the other hand, Ertle et al,'25' in a to-date to suggest that trichloroethylene has increased cancer in man.
<br /> similar study,observed fatigue,lassitude,and headache in volunteers. An epidemiology study"81 on the hepatic tumor incidence in sub-
<br /> Trichloroethylene was neither embryotoxic nor teratogenic in jects working with trichloroethylene in Czechoslovakia failed to show
<br /> Sprague-Dawley rats and Swiss Webster mice inhaling trichloro- a correlation between liver concentration and occupational exposure
<br /> ethylene.126'These results have been confirmed in two other studies to trichloroethylene. A cohort study on trichloroethylene exposure
<br /> in female rats exposed in one case to 500 ppm and in other to 1800and cancer in man, conducted recently in the Scandinavian coun-
<br /> ppm.(27.28) tries""of 7688 workers exposed to relatively small concentrations
<br /> Trichloroethylene was found to be weakly mutagenic in E.coli in of trichloroethylene,did not reveal any excess cancer mortality. Half
<br /> the presence of a metabolizing system,f291 and negative in dominant of the population under study was exposed to trichloroethylene for
<br /> lethal assays in rats and mice,"'.31 or in extensive studies in more than 10 years;548 persons were exposed to trichloroethylene
<br /> Drosophila.132) Positive effects in some studies may be due to epoxy concentrations greater than 30 ppm,3095 persons to concentrations
<br /> stabilizers sometimes present in trichloroethylene. smaller than 30 ppm.The exposure was evaluated from urinary ex-
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