Subclinical increases in serum transaminase activities among female workers exposed to toluene at sub-OEL levels.

Despite the general belief that toluene is not very hepatotoxic under occupational conditions1,2), hepatic damage was sometimes reported among glue sniffers3-5), accident victims6) and laboratory animals7,8) exposed either to toluene or its homologue xylene. Trials are made in the present study to examine if there are any detectable changes in hepatic functions in relation to the intensity of the exposure to toluene in occupational settings. Three groups of female subjects were examined. Those in Group A were female workers in a rubber-bag container plant where toluene was the sole organic solvent present in the glue. Group B consisted of 18 female employees engaged in the production of rubber boots utilizing the glue containing toluene as a major solvent together with minute amount of methyl ethyl ketone. Hospital nurses, 50 in total, served as controls. Time-weighted average of exposure to toluene was determined using carbon felt dosimeters as personal samplers9,10). Urine samples, collected from the exposed groups at the end of the afternoon shifts, were subjected to the analyses for hippuric acid and o-cresol as the indices of exposure to toluene by the methods previously reported11). Hepatic function tests and hematological examinations were carried out by the conventional methods with blood samples collected during the morning shifts. Statistical evaluations were made with Student's t-test with an assumpiton of normal distribution, except for urinary metabolites for which a log-normal disribution was assumed12). In Table 1 are summarized the results of hepatic function tests together with the intensities of exposure to toluene. The time-weighted average exposure concentration of toluene as measured by personal sampling was 69 ppm for Group A and 45 ppm for Group B, both being well below the current occupational exposure limit (OEL) of 100 ppm13). Such exposures could be confirmed by the elevated levels of the two metabolites in urine. No hematological abnormalities were detected in any groups. When hepatic functions were examined, elevations of both GOT and GPT levels were detected; the increases were, even though subclinical, statistically significant (p<0.01) and dose-dependent. Possible effect of alcohol intake could be ruled