HEPATIC-FUNCTION IN WORKERS OCCUPATIONALLY EXPOSED TO CARBON-TETRACHLORIDE

Objectives-To identify any differences in hepatic function between wor kers exposed to carbon tetrachloride and controls, and to identify the best variable with which to examine any effects. Methods-In a cross s ectional study of hepatic function in workers occupationally exposed t o carbon tetrachloride, 135 exposed employees were compared with 276 n on-exposed controls. The exposed group was taken from three sites in t he north west of England and the control group included non-exposed wo rkers from one of these sites and another site located nearby. Demogra phic and alcohol consumption data were collected from both groups by q uestionnaire. Each member of the study group was allotted a notional e stimated exposure to carbon tetrachloride, calculated from historic pe rsonal monitoring data and job category. A fasting sample of blood was taken from all participants and analysed for a variety of biochemical and haematological variables, The techniques of univariate and multiv ariate analysis of variance were used to investigate tire effect on bi ochemical and haematological indices of a range of factors. Results-Mu ltivariate analysis of variance of four core liver function variables, alanine transaminase, aspartate transaminase, alkaline phosphatase, a nd gamma-glutamyl transferase, showed a significant difference between exposed and non-exposed workers. The univariate analyses identified i ncreases in only alkaline phosphatase and gamma-glutamyl transferase w ithin the exposed group and these did not show a significant dose-resp onse relation. Univariate analysis of variance did show effects of alc ohol and age on several variables. Significant differences between exp osed and control groups for three haematological variables, haemoglobi n, packed cell volume, and red blood count, were thought not to be due to the effects of exposure. Clinical review of exposed subjects with abnormal results did not show clinically evident disease that could ha ve been associated with exposure to carbon tetrachloride. Also, a foll ow up study conducted three years after the cross sectional study at t he site with highest exposures to carbon tetrachloride showed no evide nce of any further changes in liver function variables. Conclusions-Th e most sensitive statistical methods have shown significant difference s in the liver function variables measured between people exposed to c arbon tetrachloride and the control group. The interpretation of the d ata collected was that these differences may be due to exposure to car bon tetrachloride but this was not clearly shown. Furthermore, the cha nges found have not given rise to any clinical disease.