Handbook of Solvents - George Wypych - ChemTech - Ventech!

1398 David K. Bonauto, C. Andrew Brodkin, William O. Robertson
The ACGIH has set a TLV of 10 ppm over an 8 hour time weighted average and a 40
hour work week for chloroform. Because chloroform is a potential carcinogen, the lowest
possible exposure is recommended. Occupational hepatotoxicity below the ACGIH TLV
has been demonstrated, with evidence of adverse effects between 2 and 10 ppm. 51,58
Clinical manifestations of chloroform toxicity involve multi-organ system effects including
damage to the central nervous system, the kidney and lung as well as the liver. 59
Fulminant toxic hepatitis appears within one to three days following exposure, with death at
approximately one week in severe poisonings. 57 In nonfatal cases, hepatic inflammatory
changes,with hepatomegaly and transaminitis can occur within hours. 57 Ingestion or significant
inhalational exposure should be managed in a closely monitored hospital setting.
20.8.2.4 Dichloromethane
Dichloromethane is commonly used as a degreaser and a paint stripper. It is metabolized in
the liver by the cytochrome p-450 pathway to produce carbon monoxide. 60 An independent
pathway of metabolism occurs via conjugation with glutathione. 60 Animal experimentation
has demonstrated hepatotoxicity at near lethal concentrations of dichloromethane. 61,62 Dichloromethane
potentiates carbon tetrachloride hepatotoxicity in rat livers. 38 Short term exposure
to both ethanol and dichloromethane demonstrate an antagonistic relationship, while
chronic exposure potentiates hepatotoxicity. 63
Cases of human hepatotoxicity to dichloromethane have been reported. 62,64 Workers in
an acetate fiber production plant, exposed to 140 to 475 ppm of dichloromethane, with concomitant
exposures to acetone and methanol, were observed to have elevated bilirubin and
ALT levels relative to workers exposed to acetone alone. 64 Bilirubin elevations were dependent
on the level of dichloromethane exposure. 64 Other studies have shown no significant
effects in the range of 5 to 330 ppm of dichloromethane. 65 Chronic exposure (greater
than 10 years) to dichloromethane levels greater than 475 ppm was not associated with significant
elevations in liver function tests. 66 There is minimal evidence of human
hepatotoxicity of dichloromethane less than the ACGIH TLV of 50 ppm over an 8 hour
time weighted average. 43
20.8.2.5 Trichloroethanes
There are two isomers of trichloroethane, namely methyl chloroform and
1,1,2-trichloroethane. Animal hepatotoxicity to 1,1,2-trichloroethane is documented in the
literature 67 with potentiation of toxicity in association with acetone, 68 isopropyl alcohol 69
and ethanol. 70 Hepatotoxicity, with steatosis, necrosis, elevated serum enzymes, and increased
liver weight have been observed in animal models exposed to 1000 ppm of methyl
chloroform. 71 Human studies consist of case reports documenting hepatotoxicity, with elevated
serum transaminases and fatty liver disease related to 1,1,1-trichloroethane exposure.
72,73 Epidemiologic evidence suggests little hepatotoxicity related to this agent at exposure
levels