Occupational liver injury. Present state of knowledge and future perspective

Changes of serum biochemical parameters and liver pathology in 18 patients with 1,1,2,2-tetrachloroethane-induced hepatotoxicity

OBJECTIVE

To evaluate the changes of serum biochemical parameters and liver pathology in patients with 1,1,2,2-tetrachloroethane (TTCE)-induced hepatotoxicity.

METHODS

A total of 18 patients were diagnosed as TTCE-induced hepatotoxicity with an incubation period of 11-56 days. Blood samples were obtained from all patients and liver biopsy was performed in 16.

RESULTS

All patients had fatigue, poor appetite and dark urine, 15 of whom suffered nausea, vomiting, abdominal distension and other gastrointestinal disorders. All patients had various degrees of liver function damage, and one died from liver failure. The prothrombin time was significantly prolonged in 6 patients. Histological findings showed varying degrees of necrosis, fatty degeneration and fibrosis in portal areas without cirrhosis. Patients with more severe jaundice had more severe pathologic changes, including piecemeal and bridge necrosis, and cholestasis.

CONCLUSIONS

TTCE-induced hepatotoxicity may cause the changes in serum biochemical parameters and liver pathology. Most patients might recover with regular treatment. Prevention and early diagnosis of TTCE-induced hepatotoxicity are necessary.

Examination of the relationships between environmental exposures to volatile organic compounds and biochemical liver tests: application of canonical correlation analysis

This study was to explore the relationships between personal exposure to 10 volatile organic compounds (VOCs) and biochemical liver tests with the application of canonical correlation analysis. Data from a subsample of the 1999-2000 National Health and Nutrition Examination Survey were used. Serum albumin, total bilirubin (TB), alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT) served as the outcome variables. Personal exposures to benzene, chloroform, ethylbenzene, tetrachloroethene, toluene, trichloroethene, o-xylene, m-,p-xylene, 1,4-dichlorobenzene, and methyl tert-butyl ether (MTBE) were assessed through the use of passive exposure monitors worn by study participants. The first two canonical correlations were 0.3218 and 0.2575, suggesting a positive correlation mainly between the six VOCs (benzene, ethylbenzene, toluene, o-xylene, m-,p-xylene, and MTBE) and the three biochemical liver tests (albumin, ALP, and GGT) and a positive correlation mainly between the two VOCs (1,4-dichlorobenzene and tetrachloroethene) and the two biochemical liver tests (LDH and TB). Subsequent multiple linear regressions show that exposure to benzene, toluene, or MTBE was associated with serum albumin, while exposure to tetrachloroethene was associated with LDH and total bilirubin. In conclusion, exposure to certain VOCs as a group or individually may influence certain biochemical liver test results in the general population.

Hepatic effects among workers exposed to ethylene glycol monoethyl ether acetate

Data about hepatic effects of ethylene glycol ethers had been limited and inconsistent. In this study, we determined whether ethylene glycol monoethyl ether acetate (EGEEA) was a hepatotoxin in exposed workers. Workers from one silk-screening shop (n=29), using EGEEA as the major cleaning solvent, were recruited as high exposure group. Another group of workers with indirect and low exposure to EGEEA (n=57) were selected as the comparison group. Air concentration of EGEEA was measured by 8-h personal sampling. The mean of air EGEEA concentration in the high exposure group was 7.41-16.5 ppm. The mean of air EGEEA concentration in the low exposure group was 0.07-3.62 ppm. Liver function profiles showed that the AST, ALT, ALP and gamma GT in both male and female EGEEA-exposed workers were not significantly different from those in the comparison group. After adjustment for potential confounders such as gender, body mass index, hepatitis B status, and duration of employment, no difference in hepatic dysfunction were found between exposed and comparison groups. In addition, a two-year follow-up study of these EGEEA-exposed workers, no significant change in hepatic function was noted either. The findings suggest that EGEEA is not a hepatotoxin in this workplace.

Hepatic injuries of hexachloroethane smoke inhalation: the first analytical epidemiological study

There has been no human epidemiological data regarding the hepatic injuries of hexachloroethane-zinc oxide (HC/ZnO) inhalation. This is the first epidemiological study to investigate whether HC/ZnO inhalation exposure can induce hepatic dysfunction in exposed soldiers. Twenty soldiers, exposed to high concentration of HC/ZnO smoke for 3-10 min in a narrow tunnel (0.6 m in width) during military training, were recruited as exposed group and they were divided into high-exposed group (n=10) and low-exposed group (n=10) by the distance from the explosion locale as a surrogate of exposure condition. Another 64 soldiers, not visiting the explosion areas, were recruited as referents. Venous blood was collected for liver function analyses. After log transformation of alanine aminotransferase (ALT) and adjustment for potential confounders, serum ALT in high-exposed soldiers was statistically significantly higher than those of referents for the 3 weeks following exposure. The serum ALT in low exposed soldiers was statistically significantly higher than those of referents at the 3rd week following exposure. The mean ALT levels also showed decreasing gradients by the distance from exposure locale. In addition, the proportions of abnormality on ALT (>40U/L) were also significantly different among three exposure conditions. Follow-up study showed that the hepatic dysfunction started from 1 to 2 weeks and peaked from 3rd to 5th week after exposure. ALT level was then returned to normal within 6-8 weeks after removing from HC/ZnO smoke exposure. No sequelas in hepatic dysfunction were found until 72 weeks follow-up.

CONCLUSION

We concluded that inhalation of HC/Zn smoke can induce acute, dose-dependent and definite temporal relationship hepatic dysfunction.

Alteração de enzimas hepáticas em trabalhadores de refinaria de petróleo

OBJETIVO: A exposição ocupacional típica de uma refinaria de petróleo pode alterar a função hepática de seus trabalhadores. Assim, o objetivo do estudo foi identificar fatores de risco de alterações em enzimas hepáticas em trabalhadores de uma refinaria de petróleo. MÉTODOS: Os trabalhadores de uma refinaria de petróleo, localizada em São Francisco do Conde, Estado da Bahia, eram submetidos a exames periódicos anuais de 1982 a1998. O estudo caso-controle investigou todos os 150 casos de indivíduos com alteração simultânea de gama-glutamil transferase e de alanino amino transferase, de pelo menos 10% acima do valor de referência. Como controles, foram selecionados 150 indivíduos sem quaisquer alterações de enzimas hepáticas ou de bilirrubinas, desde a sua admissão. Foram calculadas as razões de chance e respectivos intervalos de confiança de 95% a partir de modelos de regressão logística. RESULTADOS: Em todos os setores de produção, o risco de alteração de enzimas hepáticas foi significantemente mais elevado do que no setor administrativo (RC=5,7; IC 95%: 1,7-18,4), estando controlados os efeitos do álcool, obesidade e antecedentes médicos de hepatite. No período 1992-1994 foram registrados 89 casos, 88 deles provieram dos diversos setores da produção. CONCLUSÕES: A exposição ocupacional desempenha papel importante na determinação de alterações de enzimas hepáticas em trabalhadores do refino de petróleo, além dos fatores de risco eminentemente biológicos e/ou comportamentais como obesidade e o consumo de álcool.

Harm to the liver among employees of the Municipal Police Force

The purpose of the study is to assess whether employees of the Municipal Police Force of a big city exposed to urban pollution are at risk of hepatotoxicity. The usual clinical practice tests like AST, ALT, gamma-GT, AP, conjugated and total bilirubin were carried out, accompanied by a questionnaire designed to identify the possible risk factors and the principal non-professional confounding factors for hepatotoxicity. The study covered 118 male Municipal Police employees performing traffic duties and 118 male blood donors engaged in office work. There were significant differences between exposed and controls with regard to the average AST and ALT values and values above the normal laboratory range; this was also the case for the distribution. The results suggest that there may be the possibility of liver damage among asymptomatic members of the Municipal Police Force and that periodic hepatic screening, with the above-mentioned tests, could be useful. It is presumed that chemical agents present in urban air in big cities may cause damage to the liver, even at exposure levels that fluctuate around the admissible environmental concentrations.

A historical cohort mortality study among shipyard workers in Genoa, Italy

BACKGROUND

A historical cohort mortality study was conducted among 3984 shipyard workers assigned to ship repair, refitting, and construction in the harbor of Genoa, Italy, between 1960 and 1981. These workers were exposed to asbestos fibers, welding fumes and gases, silica dust, polycyclic aromatic hydrocarbons, and solvents.

METHODS

Workers were classified in 20 different job-titles depending upon the type of activity. Standardized mortality ratios (SMRs) were computed using male residents of the Province of Genoa as the referent population.

RESULTS AND CONCLUSIONS

For the whole cohort significantly increased SMRs were detected for all causes, all cancers, liver, larynx, lung, pleural and bladder cancers, respiratory tract diseases, and cirrhosis of the liver. The analysis by job-title showed increased SMRs not only for pleural cancer, but also for lung, laryngeal cancers and respiratory tract diseases in occupations entailing heavy asbestos exposure. Bladder and liver cancers and liver cirrhosis mortality also appeared to be related to occupational exposure.

Liver damage among shoe repairers

BACKGROUND

The risk of hepatotoxicity in the shoe industry has already been suggested, however, there has been no investigation among the craftsmen who repair shoes.

METHODS

A group of 33 shoe repairers who work in supermarkets, and who use the same glues which contain mixtures of potentially hepatotoxic solvents were identified. A control group of 61 workers not exposed to hepatotoxic substances was also examined. All participants completed a questionnaire designed to identify potential risk factors and the main non-occupational confounding factors for hepatotoxicity. Laboratory tests, commonly used in clinical practice, were done to check whether they were useful markers of hepatotoxicity due to exposure to solvent mixtures, and to investigate which tests should be used in the screening campaigns.

RESULTS

The exposed workers had a higher prevalence of elevated mean alanine aminotransferase (ALT), aspartate aminotransferase (AST), conjugated bilirubin (P=0.0001), and alkaline phosphatase (AP) (P=0.004) than controls did. The number of workers who had values outside the upper limit of normal for our laboratory was significantly higher (ALT P=0.034, AST P=0. 037, conjugated bilirubin P=0.014). Exposed workers all had a ratio of ALT to AST greater than 1, with a mean of 1.5; it was > 1.6 in more than half the exposed workers.

CONCLUSIONS

The findings suggest that there is the possibility of liver involvement among even asymptomatic shoe repairers, and that periodic liver screening may be useful; furthermore, use of these tests (especially the ratio of ALT to AST) for craftsmen who repair shoes, and are exposed to solvent mixtures, is advisable even when environmental monitoring indicates levels below the threshold limit values (TLVs).

Elevated mortality from nonalcohol-related chronic liver disease among female rubber workers: is it associated with exposure to nitrosamines?

BACKGROUND

Despite several case reports describing liver toxicity of nitrosamines and the fact that some N-nitroso compounds are used to induce cirrhosis of the liver in animal models, this association has not been investigated in epidemiological studies.

METHODS

A cohort of 2,875 female rubber workers who were active on January 1, 1976, or hired thereafter, and who had been employed for at least 1 year in one of five plants producing tires or technical rubber goods was followed for mortality from January, 1976, through December, 1991. Work histories were reconstructed using routinely documented "cost center codes" and classified into six work areas. Age and calendar year standardized mortality ratios (SMR) and 95% confidence intervals (95% CI) were calculated and stratified by plant, work area, year of hire, and years of employment in the respective work area.

RESULTS

The excess mortality from cirrhosis of the liver was most pronounced for nonalcohol-related cirrhosis of the liver (ICD-9 571.4-571.9: 10 deaths, SMR 202; 95% CI 97-372). Mortality from alcohol-related cirrhosis of the liver (ICD-9 571.0-571.3: 3 deaths, SMR 153; 95% CI 31-446) and from other alcohol-related diseases (organic psychoses, injury, and poisoning) was not statistically significantly elevated. All 10 cases of nonalcohol-related cirrhosis had worked in production of technical rubber goods (SMR 279; 95% CI 134-514) and risks increased with earlier years of hire and with longer duration of employment in this work area.

DISCUSSION

Although our results must be interpreted with caution, they suggest that the observed excess deaths from cirrhosis of the liver are associated with occupational risk factors. In light of additional evidence from case reports and animal data, exposure to nitrosamines may be a plausible risk factor for the observed excess mortality.

Effects of occupational and nonoccupational factors on liver function tests in workers exposed to solvent mixtures

A total of 368 workers from six paint-manufacturing factories participated in this study. The workers were classified according to type of exposure: direct, intermittent, and no exposure. The workers' liver-function tests were influenced greatly by gender, hepatitis B, alcohol consumption, and body mass index. Both the serum concentration and the odds of abnormality of total serum bile acids were elevated among the directly exposed group. The authors concluded that analysis of covariance should take into account occupational and nonoccupational factors on liver-function tests to avoid any errors. Total serum bile acids also indicated liver dysfunction from solvent exposure.

Elevated serum liver enzymes in coke oven and by-product workers

Coke oven and by-product workers are potentially exposed to coke oven emissions (COE), which contain hundreds of chemicals and are primarily composed of polycyclic aromatic hydrocarbons (PAH) and volatile organic compounds. Some of these compounds are hepatotoxins. The objective of this study was to examine the relationship between work in coke oven and by-product plants and serum activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), the most commonly performed liver-function tests. The exposed group was composed of current workers who had been employed at least 3 months in the two coke-operation work areas, including one coke oven plant and one by-product plant (Area I: n = 117; Area II: n = 96) of a large steel company in Taiwan. Control subjects (Area III: n = 131), not visiting either coke-operation area in the last 3 months, were collected from the administrative and nonproduction areas in the same company. PAH exposure, as a surrogate of COE, was measured monthly by PM-10 size-selective high-volume-area air samplers in or around these three areas between June and December 1990, as well as between November 1992 and June 1993. The mean total respiratory particulate PAH exposure levels (< 10 microns) between November 1992 and June 1993 in Area I, II, and III were 6.8 x 10(3), 2.1 x 10(3), and 6.5 x 10(1) ng/m3, respectively. AST, ALT, and hepatitis B surface antigen tests were performed in 1994. Workers who showed either AST or ALT levels greater than reference levels (abnormal > 25 IU/L) were regarded as showing "elevated liver enzyme levels." Workers in Area I had AST levels that were 17% higher (95% confidence interval [CI], 3% to 32%]) and ALT levels that were 35% higher (95% CI, 10% to 65%)] than those in Area III after controlling for appropriate confounders. The adjusted odds ratio (Area I vs Area III) for elevated liver enzymes was 4.4 (95% CI, 1.5 to 13.4). In addition, coke oven (n = 91) and by-product workers (n = 26) from Area I had ALT levels 37% and 45% higher, respectively, compared with control subjects from Area III, after adjusting for appropriate confounders. Similar effects are also seen for AST. Workers in Area II had slightly, but not significantly, elevated AST and ALT levels. These results indicate that workers most heavily exposed to COE exhibit elevated aminotransferase levels.

Liver damage in pharmaceutical industry workers

A group of workers who were employed at a pharmaceutical manufacturing company and who participated in the entire production cycle were studied. Numerous substances, including iodo-chloro-oxyquinoline, erythromycin, disinfectants, small amounts of cortisones, and preserving agents (prevan and parabenzoates), were used in the manufacturing processes. A control group comprised individuals who were not exposed to hepatotoxic substances. This investigation was designed to determine the risk of hepatotoxicity in the pharmaceutical industry, and a protocol was used that allowed for ease of screening. In the presence of a physician, all subjects completed a clinical history questionnaire. They all underwent a general clinical examination, and specific blood chemistry tests were performed. Certain liver indices that were correlated with cytotoxicity were significantly higher in the pharmaceutical workers than among the controls. The findings confirmed that there was a problem of hepatic involvement among workers in this sector, indicating that the clinical-biohumoral screening protocol used in this study was valid for identifying subjects at risk of hepatotoxicity.

gamma-Glutamyltransferase isoenzyme pattern in workers exposed to tetrachloroethylene

In compliance with the mandatory medical surveillance of workers exposed to tetrachloroethylene (PCE) in Italy, isoenzyme fractioning of serum gamma-glutamyltransferase (GGT) was performed on 141 workers of both sexes and on 130 control subjects. None of the workers showed any clinical symptoms of liver disease and their enzymatic profiles, including AST, ALT, 5'-NU, ALP, and GGT, were within the normal reference limits. A statistically significant increase in total GGT serum level was found in the exposed subjects, which was associated with an increase in one of the two fractions normally present in healthy individuals (GGT-2), as well as with the appearance and progressive increase of the level of a fraction (GGT-4) considered to be an expression of hepato-biliary impairment. Further research is ongoing among these workers, which will clarify whether or not electrophoretic GGT tests may be useful in detecting liver function changes due to occupational exposure to PCE.

Environmental diseases of the digestive system

Environmental factors are important mediators of many diseases of the digestive system, defined as the alimentary tract and the accessory organs of digestion, the liver and pancreas. In this review, we principally focus on the action of chemical agents which are classified as (1) naturally occurring compounds, (2) occupational hazards, (3) therapeutic drugs, and (4) constituents of substances of abuse. In addition, the putative role of dietary habits in the pathogenesis of malignant diseases of the digestive system is discussed.

The use of single sample clearance estimates to probe hepatic drug metabolism in rats. I

1. Conditions were examined under which estimates of drug clearance made from a single measurement of plasma concentration effectively represented multisample estimates of clearance. When plasma concentrations were measured at various post-dose times, both individual and mean values of single sample clearance estimates, Cl, corresponded closely to multisample clearance estimates, Cl, and significant differences between Cl and Cl could not be detected. 2. Best post-dose sampling times were: theophylline, 6 h; phenytoin, 2 h; valproic acid, 20 min; antipyrine, 4 h; and S-warfarin, 48 h. 3. When theophylline clearance was evaluated by both multisample and single sample experiments during diethyl ether versus urethane anaesthesia, clearances were about 50% slower for ether-anaesthetized rats. This outcome was qualitatively and quantitatively the same regardless of whether single sample or multiple sample clearances were estimated, and single sample theophylline clearances were virtually identical to multisample clearances under both anaesthetic conditions. 4. We conclude that multiple drugs can be potentially useful for probing hepatic drug metabolizing activity in rats when using a single plasma measurement to estimate clearance. An appropriate array of such probes might effectively be used to handprint host-factor influences on drug metabolizing activity.

Serum bile acid concentrations as a liver function test in workers occupationally exposed to organic solvents

Liver injury has long been associated with occupational exposure to a wide variety of chemicals. The controversial data existing in relation to hepatotoxicity of organic solvents might be explained as a consequence of the different exposures or it may well be that the tests used for evaluating liver function might not be sensitive enough to detect any mild changes at an early stage. To study liver function during exposure to solvent mixtures, we determined serum bile acid (SBA) concentrations as compared with conventional liver function tests in a selected group of workers (n = 30) occupationally exposed to a mixture of organic solvents (mostly toluene, xylene, acetone, n-butylacetate, n-butanol, ethylacetate) and in a reference group (n = 20). The mean levels of liver enzyme activities and bilirubin concentrations in the two groups were similar, whereas mean SBA levels increased in the exposed group (8.0 +/- 6.0 mumol/l vs 2.8 +/- 1.4 mumol/l) and the difference as compared with the controls was significant (P less than 0.01). In 73% of the exposed workers, SBA levels were higher than 5.6 mumol/l (the cut-off value) as compared with 5% of the controls. These results demonstrate the higher sensitivity in detecting liver dysfunction achieved with the SBA test as compared with conventional hepatic function tests. As increased SBA concentrations are considered to reflect an impairment of anion transport across the liver, higher SBA levels in the group of workers exposed to organic solvents might be explained as a slight and early sign of liver dysfunction. Therefore, SBA determination in biological monitoring of workers exposed to potentially hepatotoxic chemicals might be proposed.