Ethanol-Induced Increase in the Metabolic Clearance of 1,1,1-Trichloroethane in Human Volunteers

Differential diagnosis between occupational chronic intoxication with organic solvents and ethanol abuse by biological markers. Case report and literature review

Given the occupational exposure to substances contained in petroleum heated to high temperature, cholestatic liver disease, neurological signs and symptoms can occur. We present a case report of a male patient with no tobacco exposure or alcohol use, but with prolonged occupational exposure to petroleum vapours and natural gases like methane, propane butane who developed liver and neurologic disease, in the absence of protective equipment. Delayed diagnosis was established after 9 years of the first symptoms occurrence. Differential diagnosis with alcoholic etiology was considered and biological biomarkers were useful.

The relationship of liver function tests to mixed exposure to lead and organic solvents

Objective

This study aims to compare liver function indices (aspartate aminotransferase [AST], alanine aminotransferase [ALT], and gamma glutamyl transferase [GGT]) among males who work with lead, organic solvents, or both lead and organic solvents, under the permissible exposure limit (PEL).

Methods

A total of 593 (out of 2,218) male workers who agreed to share their personal health information for medical research were selected for this study. Those excluded were hepatitis B carriers, individuals exposed to occupational risk factors other than lead and organic solvents, and individuals without liver function results. The 593 were divided into five groups: a lead-exposed group, an organic solvent-exposed group exposed to trichloroethylene (TCE co-exposed solvent group), an organic solvent-exposed group not exposed to trichloroethylene (TCE non-exposed solvent group), a lead and organic solvent-exposed group (mixed exposure group), and a non-exposed group (control group).

We performed a one way-analysis of variance (one way-ANOVA) test to compare the geometric means of liver function indices among the groups, using a general linear model (GLM) to adjust for age, work duration, body mass index (BMI), smoking, and alcohol intake. In addition, we performed a binary logistic regression analysis to compare the odds ratios among groups with an abnormal liver function index, according to a cut-off value.

Results

The ALT and AST of the mixed exposure group were higher than those of the other groups. The GGT of the mixed exposure group was higher than the TCE co-exposed solvent group, but there was no difference among the control group, TCE non-exposed solvent group, lead-exposed group, and mixed exposure group. The same result was evident after adjusting by GLM for age, work duration, BMI, smoking, and alcohol intake, except that ALT from the mixed exposure group showed no difference from the TCE co-exposed solvent group.

When the cut-off values of the AST, ALT, and GGT were 40 IU/L, 42 IU/L, and 63 IU/L, respectively, a logistic regression analysis showed no differences in the odds ratios of those who had an abnormal liver function index among the groups. However, if the cut-off values of the AST, ALT, and GGT were 30 IU/L, 30 IU/L, and 40 IU/L, respectively, the odds ratio of the AST in the mixed exposure group was 4.39 (95% CI 1.86-10.40) times higher than the control.

Conclusion

This study indicates that a mixed exposure to lead and organic solvents is dangerous, even if each single exposure is safe under the permissible exposure limit. Therefore, to ensure occupational health and safety in industry, a continuous efforts to study the effects from exposure to mixed chemicals is needed.

Effects of 1,1,1-trichloroethane on enzymatic activity and bacterial community in anaerobic microcosm form sequencing batch reactors

1,1,1-Trichloroethane (TCA), a major organic and groundwater contaminant, has very strong toxic effects on humans, plants and microorganisms. Effects of TCA on enzymatic activity and microbial diversity were investigated in the anaerobic sequencing batch reactor (ASBR) under methanogenic, nitrate-reducing, sulfate-reducing and benzene/toluene degrading conditions. The activities of three enzymes (lactate dehydrogenase, phosphatase and protease) were significantly decreased in the presence of 5 mg/L TCA. Within these three affected enzymes, phosphatase activity may serve as a noteworthy marker of bacterial toxicity. The activity of phosphatase was 0.2 U/L in methanogenic conditions with 5 mg/L TCA, which was 99% lower than the controls, and the enzyme activity was 18.6 U/L in methanogenic conditions with 1 mg/L TCA, which was 7% lower than the controls. DGGE profiles showed that TCA altered the bacterial community distribution and diversity obviously during the 21 day of TCA exposure. The enzyme activities decreased second lowest but TCA degrading strains Clostridium sp. DhR-2/LM-G01, Bacterial clone DCE25 and Bacterial clone DPHB06 were enriched in the methanogenic ASBR amended TCA.

Genetic polymorphism in CYP2E1: Population distribution of CYP2E1 activity

Cytochrome P-450 2E1 (CYP2E1) is a key enzyme in the metabolic activation of a variety of toxicants including nitrosamines, benzene, vinyl chloride, and halogenated solvents such as trichloroethylene. CYP2E1 is also one of the enzymes that metabolizes ethanol to acetaldehyde, and is induced by recent ethanol ingestion. There is evidence that interindividual variability in the expression and functional activity of this cytochrome (CYP) may be considerable. Genetic polymorphisms in CYP2E1 were identified and linked to altered susceptibility to hepatic cirrhosis induced by ethanol and esophageal and other cancers in some epidemiological studies. Therefore, it is important to evaluate how such polymorphisms affect CYP2E1 function and whether it is possible to construct a population distribution of CYP2E1 activity based upon the known effects of these polymorphisms and their frequency in the population. This analysis is part of the genetic polymorphism database project described in the lead article in this series and followed the approach described in that article (Ginsberg et al., 2009, this issue). Review of the literature found that there are a variety of CYP2E1 variant alleles but the functional significance of these variants is still unclear. Some, but not all, studies suggest that several upstream 5' flanking mutations affect gene expression and response to inducers such as ethanol or obesity. None of the coding-region variants consistently affects enzyme function. Part of the reason for conflicting evidence regarding genotype effect on phenotype may be due to the wide variety of exposures such as ethanol or dietary factors and physiological factors including body weight or diabetes that modulate CYP2E1 expression. In conclusion, evidence is too limited to support the development of a population distribution of CYP2E1 enzyme activity based upon genotypes. Health risk assessments may best rely upon data reporting interindividual variability in CYP2E1 function for input into physiologically based pharmacokinetic (PBPK) models involving CYP2E1 substrates.