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Selected topics related to occupational exposures. Part IV. Occupational liver disease

Occupational and environmental substances associated with liver injury include industrial chemicals, drugs, certain bacterial and viral infections, and other physical agents. Hepatotoxic chemical agents can be classified as direct hepatotoxins, indirect hepatotoxins, or agents that cause liver injury as a result of host idiosyncrasy. More than 100 industrial chemicals have been shown to be acutely hepatotoxic. Occupations with hepatotoxin exposures are numerous and include farm workers, chemists, dry cleaners, electroplaters, garage workers, health care workers, nurses, painters, printers, rayon makers, and others. Clinical presentation of occupational liver disease may be acute/subacute or chronic but is often insidious. Some hepatotoxins are capable of causing malignancy. The key to diagnosis of occupational liver disease is exposure history. The occupational and environmental history should include a brief description of the patient's current and recent jobs to the extent necessary to assess their potential for workplace hepatotoxic exposures. Confounders such as obesity, alcohol, and viral hepatitis are common, and a careful history and examination are essential. A variety of tests are used to evaluate liver disease and may include serum markers, tests of synthetic liver function, clearance tests, and anatomic tests. A key responsibility of the primary care provider is to prevent further liver injury from preventable occupational exposures; not only the patient but also coworkers may be at risk. Efforts should be made to ensure that patients with potential hepatotoxic exposures are working or living in safe conditions. Collaboration with an occupational specialist may be especially useful in this regard.

Journal Article↗

An overview of occupational benzene exposures and occupational exposure limits in Europe and North America.

Benzene has become one of the most intensely regulated substances in the world. Its ubiquitous use as a solvent has led to many working populations being exposed; in the early days often in uncontrolled conditions, leading to high exposures. Current occupational exposures are tightly controlled and are largely confined to workers in the petrochemical industry, vehicle mechanics, firefighters, workers exposed to automobile emissions, and some other occupational groups. Typically, occupational exposure levels are currently at or below 3.25 mg/m3 (1 ppm), and environmental exposures are typically below 50 microg/m3 (15 ppb). Smoking remains a significant source of exposure in both occupationally and non-occupationally exposed individuals. The early experiences of high occupational exposures led to the identification of haematopoietic effects of benzene and the need for improved control and regulation. As with most occupational standards, there has been a reduction in exposure limits as effects have been identified at ever-lower levels, accompanied by a societal concern for improved standards of occupational health. In 1946, the United States occupational exposure limit for benzene, promulgated by the American Conference of Governmental Industrial Hygienists, was 325 mg/m3 (100 ppm), but nowadays most European and North American countries have harmonised at 1.63-3.25mg/m3 (0.5-1 ppm). This latter figure was agreed within the European Union in 1997 and was adopted within national legislation by all Member States. The data on which this limit is set are essentially the same as those used by other standard-setting committees; this is an excellent example of how standards are set using science, pragmatism and societal values in the absence of complete information.

Air Pollutants, Occupational↗

Using time-to-pregnancy data to study occupational exposures: methodology.

Occupational and environmental influences on fertility are for the most part unstudied, partly because sensitive methods for studying them have not been developed. We are developing a measure of fecundability, the monthly probability of pregnancy, by studying time to pregnancy, the number of noncontracepting menstrual cycles each couple requires to conceive. The relationship of this measure of reproductive impairment with others, such as spontaneous abortion, is not known. Preliminary data from two sources suggest that reduced fertility is not highly correlated with increased risk of spontaneous abortion, despite predictions to the contrary from the toxicology literature. A current study of occupational exposures of dental assistants will address questions of data quality by providing comparisons of brief responses from mail questionnaires and telephone interviews with very detailed data from telephone interviews. This study also will allow estimation of the magnitude of two potential selection biases: selection of only planned pregnancies (time-to-pregnancy data for accidental pregnancies are not meaningful), and selection against highly infertile and sterile couples (when studying currently or previously pregnant women, sterile couples are not represented at all and highly infertile couples are underrepresented).

Female↗

Exposure-response relationships between occupational exposures and chronic respiratory illness: a community-based study.

Data from a random sample of 3,606 adults 40 to 69 yr of age residing in Beijing, China, were analyzed to investigate the association of reported occupational exposures to dusts and gases/fumes with the prevalence of chronic respiratory symptoms and level of pulmonary function. The prevalence of occupational dust exposure was 32%, and gas or fume exposure, 19%. After we adjusted for age, sex, area of residence, smoking status, coal stove heating, and education, an increased prevalence of chronic phlegm and breathlessness was significantly related to both types of exposures. Chronic cough was significantly related only to dust exposure, and persistent wheeze only to fume exposure. The global estimates of the relative odds of the four symptoms were 1.30 (95% CI [confidence interval] 1.09 to 1.48) and 1.27 (95% CI 1.09 to 1.48), respectively, for dusts and for gases/fumes. These two occupational exposures are associated with chronic respiratory symptoms independent of smoking, gender, and each other. There was an increasing prevalence of each symptom with increasing dust and fume exposure, represented by the index of cumulative exposure duration and exposure intensity. Linear trends for increased prevalence of chronic bronchitis and breathlessness were significant for both exposures, while the linear trend for wheeze was only significant for gases/fumes. Among subjects who did not report using coal stove heating, dust exposure was a significant predictor for FEV1, FEV1/FVC, FEF25-75, and peak expiratory flow rate (PEFR). There was also a significant decrease for FEV1 and FVC with increase of gas/fume exposure levels. Both current and former smokers appeared to be more susceptible to the effect of dusts than the never smokers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

[The toxicology and prevention of the risks of occupational exposure to aromatic polycyclic hydrocarbons. I. Guide lines for the prevention of the risks of occupational exposure to aromatic polycyclic hydrocarbons. Società Italiana Valori di Riferimento and Cattedra di Medicina del Lavoro, Università di Brescia].

These guidelines mainly deal with prevention of carcinogenic effects following occupational exposure to polycyclic aromatic hydrocarbons (PAH). After some toxicological remarks, the guidelines define a possible method to demonstrate and evaluate occupational exposure to PAH. In particular, it is illustrated the strategy of environmental monitoring and indicated which PAH should be measured, with suggestion about the most appropriate analytical techniques. As regards biological monitoring, the 1-OH-pyreneseems to be currently the most useful indicator since it reflects the recent and global exposure to PAH. The guidelines also give elements to interpret monitoring data, taking into account environmental and biological reference and limit values suggested by some authors, Associations, or current regulations. The most important health effects are carcinogenic and excess risks have been described mainly for lung, bladder and skin cancer in some PAH exposed workers. The studies on cytogenetic effects showed contradictory results. On the basis of such information and current regulations, the guidelines show how to perform health surveillance in preventive and periodical examinations and how to proceed for the information and formation of exposed workers. It is not advisable, on the basis of the current scientific data, to screen asymptomatic PAH exposed workers for early diagnosis of lung or bladder cancer, nor it is opportune the use of tumor markers for health surveillance nor is genetic screening applicable for individual susceptibility evaluation outside research programs.

Carcinogens↗

Benzene in blood as a biomarker of low level occupational exposure.

The occupational airborne exposure to benzene of 150 workers employed in petrol stations and a refinery plant was assessed using personal sampling pumps. All workers provided blood samples after the end of work and on the following morning before resuming work. Benzene concentrations in the blood of 243 non-occupationally-exposed subjects were also measured. The median occupational benzene exposure for all 150 workers studied was 80 micrograms/m3. Overall median blood benzene of all workers was 251 ng/l at the end of the shift, and 174 ng/l the following morning. The benzene concentrations measured in blood collected the following morning proved to be significantly lower than those measured at the end of the shift. Median blood benzene for the 243 'normal' subjects was 128 ng/l, which was significantly lower than that measured in the workers before a new work shift. The median blood benzene concentration was significantly higher in smokers than in non-smokers, both in the general population (210 ng/l vs. 110 ng/l) and in the exposed workers at the end of the shift (476 ng/l vs. 132 ng/l) and the following morning (360 ng/l vs. 99 ng/l). End-of-shift blood benzene correlated significantly with environmental exposure; this correlation was better in the 83 non-smokers than in the 67 smokers. In non-smokers with the median benzene occupational exposure of 50 micrograms/m3, no difference was found in blood benzene concentration in exposed and non-exposed subjects.

Adolescent↗

National Institute for Occupational Safety and Health; occupational exposure to inorganic lead: request for comments and information; republication--NIOSH. Request for comments and information relevant to occupational exposure to inorganic lead.

NIOSH is reviewing its recommendations contained in the document Criteria for a Recommended Standard.... Occupational Exposure to Inorganic Lead, Revised Criteria--1978 [NIOSH 1978]. The evaluation of recent literature indicates that the NIOSH recommended exposure limit [REL] of 100 micrograms/m3 as an 8-hour time-weighted average [TWA] in that document does not sufficiently protect workers from the adverse effects of exposure to inorganic lead. NIOSH is requesting comments and information relevant to the evaluation of the potential health risks associated with occupational exposure to inorganic lead, as well as case reports or other data that demonstrate adverse health effects in workers exposed to inorganic lead at or below the OSHA permissible exposure limit [PEL] of 50 micrograms/m3 as an 8-hour TWA and any information pertinent to evaluating the technical feasibility of establishing a more protective REL for inorganic lead. NIOSH is also soliciting information on worker blood lead levels [BLLs] including data on methodologies used in measuring BLLs in the workplace and information that can be used for comparing airborne inorganic lead concentrations to observed BLLs. NIOSH intends to analyze the feasibility of developing preventive measures including an REL that would provide better protection for workers. In the interim, NIOSH plans to adopt the more protective current OSHA PEL as its REL.

Humans↗

Pesticide exposure of non-occupationally exposed subjects compared to some occupational exposure: a French pilot study.

Data about non-dietary exposure to different chemical classes of pesticides are scarce, especially in France. Our objective was to assess residential pesticide exposure of non-occupationally exposed adults, and to compare it with occupational exposure of subjects working indoors. Twenty unexposed persons, five gardeners, seven florists and nine veterinary workers living in Paris area were recruited. Nineteen residences, two greenhouses, three florist shops and three veterinary departments were then sampled. Thirty-eight insecticides, herbicides and fungicides were measured in indoor air with an air sampler for 24 h, and on hands by wiping them with isopropanol-wetted swabs. After extraction, samples were analysed by gas and high-performance liquid chromatography. Seventeen different pesticides were detected at least once in indoor air and twenty-one on the hands. An average of 4.2+/-1.7 different pesticides was detected per indoor air sample. The organochlorines lindane, alpha-endosulfan and alpha-HCH were the most frequently detected compounds, in 97%, 69% and 38% of the samples, respectively. The organophosphates dichlorvos and fenthion, the carbamate propoxur and the herbicides atrazine and alachlor were detected in more than 20% of the air samples. Indoor air concentrations were often low, but could reach 200-300 ng/m(3) in residences for atrazine and propoxur. Propoxur levels significantly differed between the air of veterinary places and other places (Kruskal-Wallis test, p<0.05) and dieldrin levels between residences and workplaces (p<0.05). There was a greater number of pesticides on hands than in air, with an average of 6.3+/-3.3 different pesticides detected per sample, the most frequently detected being malathion, lindane and trifluralin, in more than 60% of the subjects. Maximal levels (up to 1000-3000 ng/hands) were observed either in the general population or in workers, depending on the pesticide. However, no significant difference was observed between workers and general population handwipe pesticide levels. As expected, gardeners were exposed to pesticides sprayed in greenhouses. Florists and veterinary workers, whose pesticide exposure had not been described until now, were also indirectly exposed to pesticides used for former pest control operations. Overall, general population was exposed to more various pesticides and at levels sometimes higher than in occupational places. The most frequent pesticides in residences were not the same as in US studies but levels were similar. These preliminary results need to be confirmed in a greater number of residences from different parts of the country, in order to better assess pesticide exposure of the general population and its influencing factors.

Acetamides↗

Post-exposure prophylaxis following non-occupational exposure to HIV: risks, uncertainties, and ethics.

Post-exposure prophylaxis (PEP) is the standard of care for occupational exposure to HIV infection although it has not been evaluated following non-occupational exposure. Although the most effective methods for preventing HIV infection remain those that prevent exposure to HIV in the first place, this article discusses the dilemmas surrounding post-exposure therapy following non-occupational exposure.

Anti-HIV Agents↗

Modification of risk of arsenic-induced skin lesions by sunlight exposure, smoking, and occupational exposures in Bangladesh.

BACKGROUND: The risk of skin lesions associated with arsenic exposure from drinking water in Bangladesh is considerably greater in men than in women. METHODS: Using baseline data from 11,062 cohort members in the Health Effects of Arsenic Longitudinal Study in Araihazar, Bangladesh, we performed a cross-sectional analysis to evaluate whether the association between arsenic exposure from drinking water and the risk of skin lesions is modified by tobacco smoking, excessive sunlight, the use of fertilizer, and the use of pesticides. A time-weighted well arsenic concentration was estimated for each participant by incorporating history of well use. Relative excess risk for interaction (RERI) and its 95% confidence intervals (CIs) were estimated using adjusted prevalence odds ratios. RESULTS: We observed a synergistic effect between the highest level of arsenic exposure (> 113 microg/L) and tobacco smoking on risk of skin lesions in men (RERI = 1.5 [95% CI = 0.3 to 2.7] overall and 1.7 [0.2 to 3.4] for the subpopulation with longer-term arsenic exposure). We also observed suggestive synergistic effects between higher levels (28.1-113.0 microg/L and 113.1-864.0 microg/L) of arsenic exposure and fertilizer use in men (RERI = 1.0 [-0.2 to 2.2] and 1.3 [-0.2 to 2.9] respectively). Furthermore, the risk of skin lesions associated with any given level of arsenic exposure was greater in men with excessive sun exposure. The patterns of effect estimates in women indicate similar-but-weaker interaction effects of arsenic exposure with tobacco smoking and fertilizer use. CONCLUSIONS: These findings help explain why the risk of arsenic-related skin lesions was much greater in men than in women in Bangladesh. Because most arsenic-induced skin cancers arise from these skin lesions, treatment and remediation plans should take into consideration these etiologic cofactors.

Adult↗

[Abnormalities of respiratory function in civil defence firefighter-submarine divers. Respective role of diving and occupational exposure related to occupational firefighter's functions].

Lung function was studied in 20 firemen-submarine divers (mean age 36 +/- 1.2 years) of the French civil defence undergoing the medical check-up compulsory for professional divers (lung function tests are not systematically performed in ordinary firemen). Compared with the CECA standards: (1) vital capacity (VC) was increased, residual volume (RV) was decreased and total lung capacity (TLC) was unchanged; (2) with the exception of peak respiratory flow, all expiratory flow values (FEV1, MEF50, MEF25) were decreased; (3) the permeability factor (KCO) was decreased. These functional abnormalities were moderately worse in subjects who smoked. Some abnormalities (increased VC, decreased RV) are typical of diving activities, but the deterioration of effort-dependent expiratory flow values and alveolar-capillary diffusion must be ascribed to specific nuisances (fumes, polluants, toxic substances) associated with fireman's activities. Monitoring lung function in all professional firemen therefore seems to be necessary, if not indispensable.

Adult↗

Neuropsychological function in retired workers with previous long-term occupational exposure to solvents.

OBJECTIVES: It is plausible that neurodegenerative processes of aging might have a contributing role in the development of chronic effects of exposure to organic solvents. This study evaluated the risk for neuropsychological deficits among retired workers, relative to their histories of exposure to occupational solvents. METHODS: This cross sectional study evaluated retired male workers, 62-74 years of age, including 89 people with previous long-term occupational exposure to solvents (67 retired painters and 22 retired aerospace manufacturing workers), and 126 retired carpenters with relatively minimal previous exposure to solvents. Subjects completed a standardised neuropsychological evaluation and psychiatric interview, structured interviews for histories of occupational exposure and alcohol consumption, and questionnaires assessing neurological and depressive symptoms. RESULTS: By comparison with the carpenters, the painters on average reported greater cumulative alcohol consumption and had lower scores on the WAIS-R vocabulary subtest, usually presumed to reflect premorbid intellectual functioning. These findings, however, were not sufficient to account for the other study findings. Controlling for age, education, vocabulary score, and alcohol use, the painters had lower mean scores on test measures of motor, memory, and reasoning ability; and a subgroup of aerospace workers with moderate to high cumulative exposure to solvents (n = 8) had lower mean scores on measures of visuomotor speed, and motor, attention, memory, and reasoning ability. Subjects were more likely to have an increased number of relatively abnormal test scores (three or more outlier scores on 17 test measures) among both the painter group (odds ratio (OR), 3.1; 95% confidence interval (95% CI) 1.5 to 6.2) and the subgroup of aerospace workers with higher cumulative exposure (OR 5.6; 95% CI 1.0 to 38). The painters, but not the aerospace workers, reported significantly more neurological and depressive symptoms. CONCLUSIONS: The findings are consistent with residual central nervous system dysfunction from long-term exposure to organic solvents, persisting years after the end of exposure.

Aged↗

Compliance versus risk in assessing occupational exposures.

Assessments of occupational exposures to chemicals are generally based upon the practice of compliance testing in which the probability of compliance is related to the exceedance [gamma, the likelihood that any measurement would exceed an occupational exposure limit (OEL)] and the number of measurements obtained. On the other hand, workers' chronic health risks generally depend upon cumulative lifetime exposures which are not directly related to the probability of compliance. In this paper we define the probability of "overexposure" (theta) as the likelihood that individual risk (a function of cumulative exposure) exceeds the risk inherent in the OEL (a function of the OEL and duration of exposure). We regard theta as a relevant measure of individual risk for chemicals, such as carcinogens, which produce chronic effects after long-term exposures but not necessarily for acutely-toxic substances which can produce effects relatively quickly. We apply a random-effects model to data from 179 groups of workers, exposed to a variety of chemical agents, and obtain parameter estimates for the group mean exposure and the within- and between-worker components of variance. These estimates are then combined with OELs to generate estimates of gamma and theta. We show that compliance testing can significantly underestimate the health risk when sample sizes are small. That is, there can be large probabilities of compliance with typical sample sizes, despite the fact that large proportions of the working population have individual risks greater than the risk inherent in the OEL. We demonstrate further that, because the relationship between theta and gamma depends upon the within- and between-worker components of variance, it cannot be assumed a priori that exceedance is a conservative surrogate for overexposure. Thus, we conclude that assessment practices which focus upon either compliance or exceedance are problematic and recommend that employers evaluate exposures relative to the probabilities of overexposure.

Air Pollutants, Occupational↗

[Two cases of pleural mesothelioma following unusual and unrecognized exposure to asbestos. The role of Occupational Health and Safety Service in identifying past occupational exposure].

BACKGROUND: In Italy there was a wide use of asbestos in various manufacturing sectors and for many different uses, some of which are still partly or completely unknown. A detailed reconstruction of the work histories of mesothelioma patients made it possible, in some cases, to identify ignored circumstances of asbestos exposure. Moreover, the identification of cluster of cases takes on special significance in suggesting a possible previous asbestos exposure, where the information collected on single cases do not imply as much. OBJECTIVES: This report concerns two cases of malignant mesothelioma that occurred in two workers employed in the same processes in a small factory that manufactured and repaired electric motors for hand tools. METHODS AND RESULTS: In the Province of Brescia (one million inhabitants) a Mesothelioma Register is in operation. The first case was classified, according to Re.Na.M.1996 criteria (National Mesothelioma Register) as "unknown" occupational exposure. The identification of a second case, that was discovered thanks to the surveillance system of the Mesothelioma Register, encouraged the local Occupational Health and Safety Service to perform a more detailed investigation that revealed, for both subjects, previously unknown occupational exposure. This consisted of grinding, in a damp setting, electric motor parts bushed with phenolic thermosetting resins reinforced with chrysotile asbestos. Moreover, weekly cleaning of the plants could have been an occasion for dust dispersion. It is likely that this exposure did not last long and was limited in extent. Other similar reports of such circumstances of occupational exposure were not available in the literature. CONCLUSIONS: The results confirm the high information value of systematic collection of incidental cases in the population, which is feasible thanks to the disease register, and the significant role of the local Occupational Health Services in demonstrating past asbestos exposure.

Adult↗

Carcinogenicity and other health effects of acrylonitrile with reference to occupational exposure limit.

The occupational exposure limit for acrylonitrile (AN) has been set by many organizations on the basis of its carcinogenicity. However, recent epidemiological studies do not afford evidence supporting the hypothesis that AN is carcinogenic to humans. Review of the 18 published cohort studies revealed that, although there is not adequate evidence in humans for carcinogenicity of AN, the possibility of a causal association between high exposure to AN and lung cancer in humans cannot be excluded. It was pointed out that carcinogenic potential of AN may be weak, if any, to humans, and the current occupational exposure limit (OEL) for AN of 2 ppm was evaluated as appropriate in view of AN exposure levels reported by epidemiological studies. Based also on review of the literature on health effects other than carcinogenicity, it was concluded that the current OEL for AN is a reasonable value and there is no need for a revision at present.

Acrylonitrile↗

Biological monitoring of occupational exposure to tetrahydrofuran.

Occupational exposure to tetrahydrofuran (THF) was studied by analysis of environmental air, blood, alveolar air, and urine from 58 workers in a video tape manufacturing plant. Head space gas chromatography (GC) with an FID detector was used for determination of THF concentration in alveolar air, urine, and blood. Environmental exposure to THF was measured by personal sampling with a carbon felt passive dosimeter. When the end of shift urinary THF concentrations were compared with environmental time weighted average (TWA) values, urinary THF concentration corrected for specific gravity correlated well with THF concentration in air (r = 0.88), and uncorrected urinary THF concentration gave a similar result (r = 0.86). Correction for creatinine in urine weakened the correlation (r = 0.56). For exposure at the TWA concentration of 200 ppm the extrapolated concentration of THF was 33 mumol/l in blood and 111.9 mumol/l (61 mumol/g creatinine) or 109 mumol/l at a specific gravity of 1.018 in urine. The correlation between exposure to THF and its concentration in exhaled breath and blood was low (r = 0.61 and 0.68 respectively). Laboratory methodological considerations together with the good correlation between urinary THF concentration and the environmental concentration suggest that THF concentration in urine is a useful biological indicator of occupational exposure to THF.

Adult↗