Occupational medicine (1)

The Status of Occupational Stress and Its Influence the Quality of Life of Copper-Nickel Miners in Xinjiang, China

The purpose of this study was to investigate the status of occupational stress and its influence on the quality of life of copper-nickel miners, in order to provide a theoretical basis for alleviating occupational stress to improve their quality of life. Stratified cluster sampling and a self-administered questionnaire survey were used. The Effort⁻Reward Imbalance (ERI) questionnaire and the SF-36 (36-Item Short Form) health survey scale were administered to all 2000 miners registered with a copper-nickel mining human resources department and who had been on duty for more than one year. In total, 1857 valid questionnaires were collected, with a response rate of 92.85%. The percentage of the copper-nickel miners suffering from occupational stress was 42.65%. A statistically significant difference was observed in relation to the prevalence of occupational stress among miners of different genders, ages, education levels, and operating units. The occupational stress detection rate was higher for males than females. Miners aged between 30 and 34 years exhibited the highest level of occupational stress compared to other age groups. Those with a junior college education exhibited the highest rate of occupational stress compared to those with other levels of education. Those working in the smelting unit exhibited the highest rate of occupational stress compared to those working in other operational units. Those classified as experiencing stress (an ERI score >1) had lower quality of life scores than miners classified as not experiencing stress (an ERI score ≤1). The results show that level of education, monthly income, and degree of occupational stress affect quality of life among copper-nickel miners. It was found that older age, lower income, higher education level, and higher degree of occupational stress were factors related to poorer quality of life. Copper-nickel miners have high levels of occupational stress, and occupational stress is a risk factor that can diminish quality of life.

Metals and disease: a global primary health care perspective

Metals are an important and essential part of our daily lives. Their ubiquitous presence and use has not been without significant consequences. Both industrial and nonindustrial exposures to metals are characterized by a variety of acute and chronic ailments. Underreporting of illnesses related to occupational and environmental exposures to chemicals including metals is of concern and presents a serious challenge. Many primary care workers rarely consider occupational and environmental exposures to chemicals in their clinical evaluation. Their knowledge and training in the evaluation of health problems related to such exposures is inadequate. This paper presents documented research findings from various studies that have examined the relationship between metal exposures and their adverse health effects both in developing and developed countries. Further, it provides some guidance on essential elements of a basic occupational and environmental evaluation to health care workers in primary care situations.

Dose-Response Relationships and Threshold Levels in Skin and Respiratory Allergy

A literature study was performed to evaluate dose-response relationships and no-effect levels for sensitization and elicitation in skin- and respiratory allergy. With respect to the skin, dose-response relationships and no-effect levels were found for both intradermal and topical induction, as well as for intradermal and topical elicitation of allergenic responses in epidemiological, clinical, and animal studies. Skin damage or irritation may result in a significant reduction of the no-effect level for a specific compound. With respect to the respiratory tract, dose-response relationships and no-effect levels for induction were found in several human as well as animal studies. Although dose-response relationships for elicitation were found in some epidemiological studies, concentration-response relationships were present only in a limited number of animal studies. Reported results suggest that especially relatively high peak concentrations can induce sensitization, and that prevention of such concentrations will prevent workers from developing respiratory allergy. Moreover, induction of skin sensitization may result in subsequent heightened respiratory responsiveness following inhalation exposure. The threshold concentration for the elicitation of allergic airway reactions in sensitized subjects is generally lower than the threshold to induce sensitization. Therefore, it is important to consider the low threshold levels for elicitation for recommendation of health-based occupational exposure limits, and to avoid high peak concentrations. Notwithstanding the observation of dose-response relationships and no-effect levels, due to a number of uncertainties, no definite conclusions can be drawn about absolute threshold values for allergens with respect to sensitization of and elicitation reactions in the skin and respiratory tract. Most predictive tests are generally meant to detect the potential of a chemical to induce skin and/or respiratory allergy at relatively high doses. Consequently, these tests do not provide information of dose-response relationships at lower doses such as found in, for example, occupational situations. In addition, the observed dose-response relationships and threshold values have been obtained by a wide variety of test methods using different techniques, such as intradermal exposure versus topical or inhalation exposure at the workplace, or using different endpoints, which all appear important for the outcome of the test. Therefore, especially with regard to respiratory allergy, standardized and validated dose-response test methods are urgently required in order to be able to recommend safe exposure levels for allergens at the workplace.

Surface modification of quartz inhibits toxicity, particle uptake, and oxidative DNA damage in human lung epithelial cells

Quartz (crystalline silica) is not consistently carcinogenic across different industries where similar quartz exposure occurs. In addition, there are reports that surface modification of quartz affects its cytotoxicity, inflammogenicity, and fibrogenicity. Taken together, these data suggest that the carcinogenicity of quartz is also related to particle surface characteristics, and so we determined the genotoxic effects of DQ12 quartz particles versus DQ12 whose surface was modified by treating with either aluminum lactate or polyvinylpyridine-N-oxide (PVNO). The different particle preparations were characterized for hydroxyl-radical generation using electron spin resonance (ESR). DNA damage was determined by immunocytochemical analysis of 8-hydroxydeoxyguanosine (8-OHdG) and the alkaline comet-assay using A549 human lung epithelial cells. Cytotoxicity was measured using the LDH- and MTT-assays, and particle uptake by the A549 cells was quantified by light microscopy, using digital light imaging evaluation of 800 nm sections. The ability of quartz to generate hydroxyl-radicals in the presence of hydrogen peroxide was markedly reduced upon surface modification with aluminum lactate or PVNO. DNA strand breakage and 8-OHdG formation, as produced by quartz at nontoxic concentrations, could be completely prevented by both coating materials. Particle uptake into A549 cells appeared to be significantly inhibited by the PVNO-coating, and to a lesser extent by the aluminum-lactate coating. Our data demonstrate that respirable quartz particles induce oxidative DNA damage in human lung epithelial cells and indicates that surface properties of the quartz as well as particle uptake by these target cells are important in the cytotoxic and the genotoxic effects of quartz in vitro.

Imaging of occupational lung disease

Occupational lung disease comprises a wide variety of disorders caused by the inhalation or ingestion of dust particles or noxious chemicals. These disorders include pneumoconiosis, asbestos-related pleural and parenchymal disease, chemical pneumonitis, occupational infection, hypersensitivity pneumonitis, and organic dust toxic syndrome. Most of these disorders produce diffuse lung disease. Although many of the disorders can be detected at chest radiography, high-resolution computed tomography (CT) has been shown to be superior to chest radiography in depicting parenchymal, airway, and pleural abnormalities. Some occupational lung diseases have characteristic radiologic features suggesting the correct diagnosis, whereas in others, a combination of clinical features, related occupational history, radiologic findings, and literature supporting an association between the exposure and the disease process is required for diagnosis. With advances in chest radiology, including high-resolution CT, radiologists play a key role in the clinical evaluation of occupational lung diseases and should continue their involvement in the diagnosis and treatment of these diseases.

N-acetyl L-cysteine attenuates oxidant-mediated toxicity induced by chrysotile fibers

Chrysotile, an important commercial variety of asbestos, is known to cause oxidative stress by enhancing production of hydrogen peroxide (H(2)O(2)) and thiobarbituric acid reactive substances (TBARS), depleting glutathione (GSH) and altering levels of GSH redox system enzymes. N-acetyl L-cysteine (NAC), a compound that increases GSH levels, protects cells against chrysotile toxicity. In the present study, rats were exposed intratracheally to a single dose (5 mg/rat) of chrysotile. This was followed by a daily dose of NAC 50 mg/kg. b. wt., i.p. At 1, 4, 8 and 16 days post chrysotile exposure lung lavage fluid was collected to determine H(2)O(2) generation, TBARS production, GSH level and its redox system enzymes activities. A significant decrease in H(2)O(2) and TBARS, an increase in GSH content and its redox system enzymes was observed in chrysotile+NAC animals in comparison to chrysotile-exposed animals. In this preliminary study it appears that NAC may be protecting cells against oxidative damage. This protection may be due to its ability to maintain intracellular GSH/oxidative scavenging capability.

Labor Day and the war on workers

We celebrate Labor Day every year with barbecues and picnics, rarely remembering that the holiday was born in the midst of tremendous labor struggles to improve working conditions. In the last century, 16-hour workdays and 6- and 7-day workweeks led to terribly high injury rates in the nation's mines and mills. Thousands upon thousands of workers died, caught in the grinding machinery of our growing industries. Today, despite improvements, thousands of workers still die in what has been described as a form of war on the American workforce. This commentary reminds us of the historical toll in lives and limbs that workers have paid to provide us with our modern prosperity. It also reminds us that the continuing toll is far too high and that workers who died and continue to die in order to produce our wealth deserve to be remembered and honored on this national holiday.

L-arginine uptake and metabolism by lung macrophages and neutrophils following intratracheal instillation of silica in vivo

Nitric oxide (NO) has been associated with lung inflammation following exposure to silica. L-arginine can be converted to NO and L-citrulline by nitric oxide synthase (NOS), or into urea and L-ornithine by arginase. We tested the hypothesis that after instillation of silica into rat lungs in vivo, lung inflammatory cells increase L-arginine metabolism by both NOS and arginase, which is associated with an increase in L-arginine uptake. We isolated lung inflammatory cells 3 d after silica or saline (control) exposure. The uptake of [3H]L-arginine at 24 h by cells from silica-exposed lungs (73.9 +/- 4.8%) was significantly greater than uptake by control cells (24.7 +/- 2.2%; P < 0.05) and was a saturable process. The greater [3H]L-arginine uptake by cells from silica-exposed lungs was associated with greater NO and urea production than by control cells. The uptake of [3H]L-arginine by cells from control or silica-exposed lungs was blocked in a dose-dependent manner by L-ornithine (an inhibitor of L-arginine transport) and by Nomega-nitro-L-arginine methyl ester (L-NAME) (an NOS inhibitor), but not by L-valine (an arginase inhibitor). The production of NO by cells from silica-exposed lungs was completely blocked by L-NAME. The addition of L-arginine to media resulted in dose-dependent production of NO and urea. The results show that lung inflammatory cells increase L-arginine uptake and metabolism by both NOS and arginase following in vivo silica exposure. The increase in L-arginine uptake may represent a mechanism to maintain an intracellular supply of this amino acid. NO can react to generate peroxynitrite, a potential mediator of lung injury following silica exposure.

Study of employees with anhydride-induced respiratory disease after removal from exposure

The purpose of this study was to determine the clinical and immunologic status of hexahydrophthalic anhydride (HHPA)-exposed employees who had developed an immunologic respiratory disease and who have been removed from exposure for at least 1 year. In a surveillance study spanning 4 years, we identified 28 employees with HHPA-induced immunologic respiratory disease who had been removed from exposure for at least 1 year. Seven had asthma, nine had hemorrhagic rhinitis, four had both, and eight had allergic rhinitis alone. Respiratory symptoms were assessed by physician-administered questionnaires. For each employee, a physical examination, spirometry, and chest roentgenograph were performed. Antibody against HHPA conjugated to human serum albumin (HHP-HSA) was measured using an enzyme-linked immunosorbent assay. Symptoms, signs, and spirometry normalized in all but one employee. There were no chest-roentgenograph findings at follow-up that could be attributed to HHPA. There was a decline in antibody liter for both immunoglobulin E and G against HHP-HSA. In this group of 28 employees, there was only one employee with mild asthma after removal from exposure for at least I year. Although specific antibody was still present in many, the titers were generally lower at follow-up than at presentation.

What role does occupational and environmental health law have in graduate and continuing medical education?

A two-stage survey that used the Delphi technique was performed to determine the attitudes and needs of physicians that practice occupational and environmental medicine (OEM) regarding continuing medical education (CME) and Master of Public Health (MPH) curriculum in the area of health law. Forty-six of the 80 subjects (58%) responded to the first survey, and 39 of these 46 (85%) responded to the follow-up survey. The results showed that most subjects agreed with the need for CME to devote approximately 14 hours over the next two years (1993-1995) to occupational/environmental health laws and regulations. Interest was also expressed in some practical business law that would be helpful to medical practices. The survey's results showed agreement on the need for a three-credit hour MPH course for OEM residents. The differences between the subgroups of academic faculty-post-1990 graduates of MPH or occupational medicine residencies, pre-1990 graduates, and those with no formal OEM education-were also investigated. Pre-1990 graduates consistently desired more hours of CME for the topics surveyed. This study should be helpful for planners of OEM CME courses and for residency directors.

Biological markers and occupational lung disease: mineral dust-induced respiratory disorders

There is a need for methods to monitor early adverse effects, exposure, and/or susceptibility of individual subjects due to occupational and environmental causes. This paper discusses the experimental origin, value, and validity of several biological indicators, termed biomarkers, that were used to study coal dust-induced respiratory disorders. The findings are presented in a framework to visualize problems and challenges when developing biomarkers. Taking the framework of mineral dust-induced lung disorders as an example, it is demonstrated how carefully designed follow-up studies are a prerequisite to test the validity and use of events often put forward as biomarkers. It is concluded from the data that serum type III procollagen is neither an exposure nor an (early) effect marker, antioxidant enzyme expression is related to the early inflammatory response after mineral dust inhalation, while the evidence is accumulating that tumor necrosis factor-alpha is a susceptibility marker for progression in mineral dust-induced lung fibrosis.

Occupational hydrocarbon exposure and chronic nephropathy

This review aims at discussing the questions raised by the hydrocarbon-related chronic nephropathy and its possible consequence, the hydrocarbon-related chronic renal failure. It has been attempted to adopt the point of view of the clinician. Therefore, the most important part of the review is devoted to a presentation and an analysis of the available data on humans. The main features of the available studies on human subjects are presented, their conclusions discussed in the light of the possible methodological flaws, and practical conclusions drawn. After a discussion of the main difficulties encountered for selecting the suitable exposure indicator, the studies are discussed in order of decreasing quality of the study design (cohort, case-control, cross-sectional studies, and the case reports). It is concluded that a great deal of controversies about chronic hydrocarbon-related nephropathy is explained by differences in the study design and that hydrocarbon-induced nephropathy is probably more than a mere hypothesis, although a causal relationship has not yet been proven. Finally, some practical consequences for dealing with a hydrocarbon-exposed patient diagnosed with a kidney disease and the need for further research are discussed.

The teaching of occupational health in US medical schools: little improvement in 9 years

A questionnaire survey of the 127 US medical schools was undertaken to assess the present status of occupational health teaching as a follow-up to two prior similar studies. The present study revealed that 78 (68%) of the 115 responding schools specifically taught occupational health during the 1991/92 academic year, in comparison with 50% in the 1977/78 and 66% in the 1982/83 academic years. The median required curriculum time was 6 hours in 1991/92, as compared with 4 hours in both previous surveys. Despite the increasing recognition of occupational health and growth of information in this field of medicine, occupational health teaching to medical students has not progressed proportionately.

Respiratory effects of air pollution on allergic disease

Allergic patients have an increased susceptibility to the adverse effects of both natural and man-made air pollutants. This goes for both indoor and outdoor air pollutants and manifests itself with biochemical, cellular, and pathophysiologic expressions of adverse health effects in allergic individuals. Also occupationally induced allergic diseases will remain very important. This area has been reviewed recently by Cullen et al. Since allergic patients comprise somewhere between 15% and 20% of the population, this increased susceptibility is of crucial importance not only for medical care and research but for legislative and regulatory consideration to protect these vulnerable individuals.

Integrating occupational health into the medicine clerkship using problem-based learning

OBJECTIVE

To improve medical students' ability and willingness to obtain occupational histories from their patients.

PARTICIPANTS

General medicine faculty and internal medicine teaching residents, who participated as instructors, and medical students during their required internal medicine clerkships.

SETTING

The primary teaching hospitals of two medical schools.

DESIGN

During alternate months, students participated in problem-based sessions that included occupational health objectives (intervention) or attended the standard small-group didactic sessions (control). Process evaluations were collected from students and faculty in the intervention group following each session. Outcome evaluation was performed using chart audit and multiple-choice testing to compare the intervention and control groups.

INTERVENTION

Intervention students participated in at least one problem-based session incorporating occupational aspects of disease into clinical internal medicine. Instructors received information packets and materials but had no other expertise in occupational medicine.

MEASUREMENTS AND MAIN RESULTS

The great majority of ratings on the process evaluations showed that the students were "moderately" to "extremely" interested in the session attended. No student rated any session to be a "waste of time," and over 90% of students would recommend the session being evaluated to a friend. Chart audit showed that students in the intervention group recorded slightly more occupational information than did those in the control group (an average of 2.97 vs. 2.37 pieces of information, p = 0.06). When the most commonly documented data (employment status and job title) were ignored, the difference between group means (1.1 vs. 0.91) was significant (p = 0.03), suggesting that intervention students were more likely to probe further into a patient's occupational history. Both groups of students collected less occupational information from women than from men (t = 3.22, p = 0.0035). Multiple-choice tests revealed no difference between the two groups in overall medical knowledge or occupational medicine knowledge.

CONCLUSIONS

Problem-based learning with specific occupational content is well accepted by students and modestly improves their occupational history taking.