Ethyl Benzene: Cancer Hazard

Do you use this common solvent?

The International Agency for Research on Cancer (IARC), a part of the World Health Organization, has classified ethylbenzene (EB) as a possible carcinogen. Ethyl benzene is present at up to 25% in technical grades of mixed xylenes, and up to 15% in gasoline. Most occupational exposures are related to technical grades of mixed xylenes used as solvents in various paints and coatings, inks, insecticides and in rubber and plastic production, as well as from the production and handling of gasoline.

Ethylbenzene was tested by inhalation exposure in single experiments in mice and rats. In mice, it increased the incidence of lung tumors in males and of liver tumors in females. In male and female rats, it increased the incidence of renal tumors.

Ethylbenzene is well absorbed from the skin, lungs and gastrointestinal tract. The fate of ethylbenzene is similar in animals and humans. Limited data were available to evaluate the toxic effects of ethylbenzene in humans. Liver and kidney weights were increased in rats following exposure to ethylbenzene. Chemical metabolism enzymes were induced in both liver and kidney of ethylbenzene-exposed rats. Ethylbenzene caused changes in brain chemistry and milk producing hormone secretion in rats. No data on reproductive or developmental effects of ethylbenzene in humans were available. In rats, mice and rabbits, developmental abnormalities are reported from exposure during pregnancy.

Ethylbenzene was non-mutagenic in some, but active in other genetic toxicology tests.

IARC concluded: "There is inadequate evidence in humans for the carcinogenicity of ethylbenzene. There is sufficient evidence in experimental animals for the carcinogenicity of ethylbenzene. Ethylbenzene is therefore possibly carcinogenic to humans (Group 2B)."

UAW Commentary

IARC is the best known international body evaluating the carcinogenic potential of chemicals. A UAW staff member participated in the working group which met in February 2000 and reached this conclusion. EB is one of a number of solvents which cause lung and tumors in mice by inhalation. The tests which demonstrated this hazard were conducted by the National Toxicology Program. Commercial xylene contains EB because the molecules have identical weights and can't be separated by distillation. Therefore, EB exposure is expected in most painting operations. The OSHA PEL for EB, as well as the NIOSH REL and the ACGIH TLV were set without taking the IARC conclusions into account.

The UAW is not prepared to recommend an exposure limit. However, the UAW recommends that all painting operations where there is a detectable odor of solvent be sampled by a method sensitive to 1 ppm. This sensitivity can routinely be achieved by charcoal tubes. Hazard Communication training and labels must be repeated to take this new information into account.

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