Showing papers in "Occupational and Environmental Medicine in 1997"

Health and safety problems associated with long working hours: A review of the current position

Abstract: The European Community Directive on Working Time, which should have been implemented in member states of the European Community by November 1996, contains several requirements related to working hours, including the right of employees to refuse to work more than 48 hours a week. The United Kingdom government attempted to oppose the Directive, arguing that there is no convincing evidence that hours of work should be limited on health and safety grounds. Much of the research in this area has focused on the problems of shiftworking and previous reviews have therefore tended to emphasise this aspect of working hours. However, there is much less information about the effects of overtime work, which is a central element of the terms of the Directive. This paper reviews the current evidence relating to the potential effects on health and performance of extensions to the normal working day. Several gaps in the literature are identified. Research to date has been restricted to a limited range of health outcomes--namely, mental health and cardiovascular disorders. Other potential effects which are normally associated with stress--for example, gastrointestinal disorders, musculoskeletal disorders, and problems associated with depression of the immune system, have received little attention. Also, there have been few systematic investigations of performance effects, and little consideration of the implications for occupational exposure limits of extensions to the working day. Existing data relate largely to situations where working hours exceed 50 a week and there is a lack of information on hours below this level, which is of direct relevance to the European Community proposal. Finally, it is clear from investigations relating to shiftwork that a range of modifying factors are likely to influence the level and nature of health and performance outcomes. These include the attitudes and motivation of the people concerned, the job requirements, and other aspects of the organisational and cultural climate. It is concluded that there is currently sufficient evidence to raise concerns about the risks to health and safety of long working hours. However, much more work is required to define the level and nature of those risks.

Short term variations in hospital admissions and mortality and particulate air pollution.

Abstract: OBJECTIVES: To determine the presence and magnitude of any relation between short term variations in ambient concentrations of particulate matter under 10 microns in diameter (PM10) and hospital admissions and mortality in Birmingham, United Kingdom. To find the relative risk associated with various concentrations of PM10, and to estimate the potential public health benefit of reducing PM10 to below various thresholds. METHODS: Retrospective ecological study. Air pollution data were taken from a national network monitoring station between 1 April 1992 and 31 March 1994, and weather data for the same period from the University of Birmingham Weather Service. Daily total hospital admissions for the same period for asthma, bronchitis, pneumonia, chronic obstructive pulmonary disease (COPD), acute ischaemic heart disease, acute cerebrovascular disease, all respiratory conditions, and all circulatory conditions were obtained from the West Midlands Regional Health Authority, as well as daily total deaths from 1 April 1992 to 31 December 1994 for chronic obstructive pulmonary disease, pneumonia, all respiratory diseases, all circulatory diseases, and all causes. Multiple linear regression models were constructed after adjusting for confounding factors (day of week, month, linear trend, relative humidity, and temperature). Relative risk of admission at various thresholds of PM10 was calculated with the model, by comparing risk of admission over the threshold with mean risk of admission over the whole period. Potential public health benefits at various thresholds were calculated with the model to predict the number of admissions of deaths that could be saved if, on each day that the PM10 had exceeded that threshold, it had instead been kept at the threshold level. RESULTS: Significant associations were found between all respiratory admissions, cerebrovascular admissions, and bronchitis admissions and PM10 on the same day. Pneumonia, all respiratory admissions, and asthma admissions were significantly associated with the mean PM10 values for the past three days. Deaths from COPD, all circulatory deaths, and all causes mortality were significantly associated with PM10 24 hours previously, and COPD deaths also with PM10 on the same day. The effect of a 10 micrograms/m3 rise in PM10 was estimated to represent a 2.4% increase in respiratory admissions, a 2.1% increase in cerebrovascular admissions, and a 1.1% increase in all causes mortality. In a population of 1 million, this would represent 0.5 extra respiratory admissions and 0.3 extra deaths. The increase in relative risk was linear without evidence of a threshold. The impact of reducing PM10 to below 70 micrograms/m3 would be small, representing less than 0.1% of respiratory admissions and 0.2% all causes mortality. The impact would be greater at lower thresholds. CONCLUSION: Ambient outdoor concentrations of PM10 in the United Kingdom are significantly associated with several indicators of acute health effect. These associations are similar to and consistent with other studies. However, the estimated size of the public health effect is small, accounting for only a small proportion of hospital admissions and mortality over a two year period.

Daily time series for cardiovascular hospital admissions and previous day's air pollution in London, UK.

Abstract: OBJECTIVE: To test for a significant association between air pollution and emergency hospital admissions for circulatory diseases (international classification of diseases-9 390-459) in London, England, that would be consistent with a causal effect of pollution on the previous day. METHODS: Long term concurrent trends, temperature, humidity, day of the week, influenza epidemic of 1989, and cyclical covariations with periodicity > 20 days in daily measures of pollution and admissions for 1987-94 were allowed for. RESULTS: There were 373556 admissions. No association was found between O3 and circulatory diseases. Four other pollutants were associated with acute myocardial infarction and circulatory diseases combined. P values and attributable cases (95% confidence intervals) for acute myocardial infarction were: black smoke P = 0.003, 2.5% (0.8% to 4.3%); NO2 P = 0.002, 2.7% (0.8% to 4.6%); CO P = 0.001, 2.1% (0.7% to 3.5%); and SO2 P = 0.0006, 1.7% (0.7% to 2.6%). There were also associations between black smoke and angina (P = 0.02), NO2 and arrhythmia (P = 0.04), and CO and other circulatory diseases (P = 0.004), but none with heart failure. Acute myocardial infarction was the only diagnosis for which there were significant associations with and without adjustment for cyclical terms. The associations with acute myocardial infarction were significant only in the cool season. CONCLUSION: Population data were consistent with 1 in 50 heart attacks currently presenting at London hospitals being triggered by outdoor air pollution. Further research is now needed to investigate whether background concentrations of black smoke, NO2, CO, and SO2 are a preventable cause of myocardial infarction. These results, if applied to all myocardial infarctions in the United Kingdom, indicate a potential saving of 6000 heart attacks a year.

Musculoskeletal symptoms and job strain among nursing personnel: a study over a three year period.

Abstract: OBJECTIVES: To examine the variation of symptoms from the neck, shoulders, and back over a three year period among female nursing personnel and the relation between job strain and musculoskeletal symptoms. METHODS: At a county hospital the female nursing personnel answered a questionnaire at baseline and then once a year over a period of three years. There were 565, 553, 562, and 419 subjects who answered the questionnaire at the first, second, third, and fourth survey, respectively. Of the study group, 285 nursing personnel answered the questionnaire on four occasions. Ongoing symptoms of the neck, shoulders, and back were assessed by means of a 10 point (0-9) scale with the verbal end points "no symptoms" and "very intense symptoms." Cases were defined as nursing personnel reporting ongoing symptoms, score > 6, from at least one of the body regions. For assessments of job strain, a Swedish version of Karasek and Theorell's model was used. RESULTS: Of the 285 subjects, 13% were defined as cases at all four assessments, and 46% varied between cases and not cases during the study period. In the repeated cross sectional surveys the estimated rate ratio (RR) for being a case was between 1.1 and 1.5 when comparing the group with job strain and the group without job strain. For the combination of job strain and perceived high physical exertion the estimated RR was between 1.5 and 2.1. When the potential risk factors were assessed one, two, or three years before the assessment of symptoms the estimated RR for becoming a case was between 1.4 and 2.2 when comparing the group with job strain and the group without job strain. CONCLUSION: Almost half of the healthcare workers varied between being a case and not, over a three year period. The analysis indicated that job strain is a risk factor for musculoskeletal symptoms and that the risk is higher when it is combined with perceived high physical exertion.

Risk of spontaneous abortion in women occupationally exposed to anaesthetic gases: a meta-analysis.

Abstract: OBJECTIVES: To determine the association between maternal occupational exposure to anaesthetic gases and risk of spontaneous abortion. METHODS: A meta-analysis was performed of published epidemiological studies identified from literature reviews, unsystematic perusal of reference lists of relevant publications, and two Medline searches (1984-92, keywords: anaesthetic gases; anaesthetics; anaesthetics, local; operating rooms; operating room nursing; pregnancy; abortion; 1985-92, keywords: anaesthetics; adverse effects; occupational exposure; anaesthesia, inhalation; operating room nursing; pregnancy; abortion). All peer reviewed studies were retained. Student theses were excluded, as were conference abstracts, unpublished material, and two studies in which data on paternal and maternal occupational exposures were pooled. The relative risk of spontaneous abortion was estimated. RESULTS: One study found no increase in risk of abortion when gases were scavenged or when the exposure to unscavenged gases was low. None of the studies included ambient gas sampling. 24 comparisons between exposed and unexposed women, obtained from 19 reports, were included. The overall relative risk was 1.48 (95% confidence interval (95% CI), 1.4 to 1.58). To test whether this result was influenced by the quality of the studies, the validity of the reviewed papers was rated on the basis of three criteria: appropriateness of the unexposed comparison group, control for non-occupational confounding variables, and response rate. The estimate of risk increased to 1.9 (95% CI, 1.72 to 2.09) when analysis was restricted to the six comparisons which were rated the most rigorous. CONCLUSIONS: Epidemiological studies based on data obtained in the prescavenging era indicate an increased risk of spontaneous abortion. The estimated increased risk was not diminished but rather increased by exclusion of the more methodologically flawed studies.

Latex allergy: epidemiological study of 1351 hospital workers.

Abstract: OBJECTIVE: To determine the prevalence of latex sensitisation among a large group of healthcare workers, study the occupational and non-occupational factors associated with latex allergy, and characterise latex exposure in air and by gloves. METHODS: All 2062 employees of a general hospital in Hamilton, Ontario, Canada who regularly used latex gloves were invited to participate in a cross sectional survey, representing the baseline phase of a prospective cohort morbidity study. Attempts were made to recruit employees who were diagnosed with latex allergy before the survey. Glove extracts were assayed for antigenic protein, and area and personal air samples were obtained on two occasions (summer and winter) to estimate exposure to airborne latex protein. A questionnaire on medical and occupational information was administered by an interviewer. Skin prick tests were performed with latex reagents, three common inhalants, and six foods. RESULTS: The mean (SD) latex protein concentrations were 324 (227) micrograms/g in powdered surgical gloves and 198 (104) micrograms/g in powdered examination gloves. Personal latex aeroallergen concentrations ranged from 5 to 616 ng/m3. There was a total of 1351 (66%) participants. The prevalence of positive latex skin tests was 12.1% (95% confidence interval (95% CI) 10.3% to 13.9%). This prevalence did not vary by sex, age, hospital, or smoking status but subjects who were latex positive were significantly more likely to be atopic (P < 0.01). Participants who were latex positive were also significantly more likely to have positive skin tests to one or more foods (Mantel-Haenszel odds ratio (OR) adjusted for atopy 12.1, 95% CI 7.6 to 19.6, P < 10(-9)). Work related symptoms were more often reported among latex positive people, and included hives (OR 6.3, 95% CI 3.2 to 12.5), eye symptoms (OR 1.9, 95% CI 1.2 to 2.8), and wheezy or whistling chest (OR 4.7, 95% CI 2.8 to 7.9). The prevalence of latex sensitivity was highest among laboratory workers (16.9%), and nurses and physicians (13.3%). When the glove consumption per healthcare worker for each department was grouped into tertiles, the prevalence of latex skin test positivity was greater in the higher tertiles of glove use for sterile (surgical) gloves (P < 0.005) but not for examination gloves. CONCLUSIONS: In this large, cross sectional study of healthcare workers, the prevalence of latex sensitisation was 12.1% (9.5% among all those eligible), and there were significant associations with atopy, positive skin tests to certain foods, work related symptoms, and departmental use of gloves per healthcare worker. This cohort is being followed up prospectively and will be retested to determine the incidence of development of latex sensitivity.

Risk factors for carpal tunnel syndrome in a general population.

Abstract: OBJECTIVE: To determine the individual, physical, and psychosocial risk factors for carpal tunnel syndrome in a general population. METHODS: Population based case-control study in Marshfield epidemiological study area in Wisconsin, USA. Cases were men and women aged 18-69 with newly diagnosed carpal tunnel syndrome (n = 206 (83.1%) of 248 eligible). Controls were a random sample of residents of the study area who had no history of diagnosed carpal tunnel syndrome (n = 211 (81.5%) of 259 eligible). Cases and controls were matched by age. Telephone interviews and reviews of medical records obtained height and weight, medical history, average daily hours of exposure to selected physical and organisational work factors, and self ratings on psychosocial work scales. RESULTS: In the final logistic regression model, five work and three non-work variables were associated with risk of carpal tunnel syndrome, after adjusting for age. For each one unit of increase in body mass index (kg/m2), risk increased 8% (odds ratio (OR) 1.08; 95% confidence interval (95% CI) 1.03 to 1.14). Having a previous musculoskeletal condition was positively associated with carpal tunnel syndrome (OR 2.54; 95% CI 1.03 to 6.23). People reporting the least influence at work had 2.86 times the risk (95% CI, 1.10 to 7.14) than those with the most influence at work. CONCLUSIONS: Carpal tunnel syndrome is a work related disease, although some important measures of occupational exposure, including keyboard use, were not risk factors in this general population study. The mechanism whereby a weight gain of about six pounds increases the risk of disease 8% requires explanation.

Air pollution and life expectancy: is there a relation?

Abstract: The great smog disasters of the past have made clear that air pollution can kill people in a matter of days: extremely high concentrations of air pollution building up under conditions of low wind speed and stable atmospheric conditions have been associated with excess deaths in the Meuse Valley, Belgium (1930); Donora, PA, United States (1948); and London, United Kingdom (1952). In the developed market economies, great efforts have since been made to curtail air pollution related to the use of fossil fuels such as coal and oil, and exposures to substances such as SO2 and soot have been dramatically reduced. For a while it was thought that ambient concentrations of air pollution had become so low as to have no discernible influence on mortality or morbidity in the population any more. However, a series of recent studies have shown that even at low concentrations of substances-such as ozone and fine particulate matter in air-day to day variations in mortality, respiratory and cardiovascular hospital admissions, symptom exacerbations among asthmatic patients, lung function in schoolchildren, etc are still associated with day to day changes in concentrations of air pollution.' Although such findings are important in their own right, they do not directly prove that long term exposure to air pollution at present levels in the developed market economies increases the prevalence of (chronic) diseases in the population, possibly leading to decreased survival and hence, reduced life expectancy: the associations found between day to day variations in mortality and air pollution may, for example, represent a \"harvesting\" effect-that is, an advancement of death by a few days or weeks in subjects already about to die from other causes anyway. Clearly, such effects would not lead to discernible effects oflong term exposure to air pollution on life expectancy in the population. There is some evidence, however, that long term exposure to relatively low concentrations of ambient air pollution leads to a measurable reduction of survival in the population. In this paper, I briefly review the evidence, focusing on effects of airborne particulate matter, and I provide a simple estimate of the effect that long term exposure to air pollution may have on life expectancy, based on this evidence.

Work environment and low back pain: the influence of occupational activities.

Abstract: OBJECTIVES: To find associations between the prevalence of low back pain and occupational activities. METHODS: Interviews of a random sample of 5185 19-59 year old Danish employees analysed by logistic regression. RESULTS: Increased risks of low back pain were found for "vibration affecting the whole body" (odds ratio (OR) = 1.28), "physically hard work" (OR = 1.28), "frequently twisting or bending" (OR = 1.71), "standing up" (OR = 1.20), and "concentration demands" (OR = 1.28). In the analysis of dose-response relations between low back pain and the risk factors, the one year period prevalence increased with increasing exposure time during a working day to each of the risk factors. The prevalence proportion ratio for those reporting to be exposed for most of the working time were 1.30 for vibrations affecting the whole body, 1.54 for physically hard work, 1.48 for frequently twisting or bending, 1.29 for standing up, and 1.13 for concentration demands. These associations seemed to be stronger in the subset of subjects who worked for 37 hours or more per week. The population attributable fractions were 15.1% for frequently twisting or bending, 15.0% for standing up, 7.6% for concentration demands, and 4.4% for physically hard work. CONCLUSION: Vibrations affecting the whole body, physically hard work, frequently twisting or bending, standing up, and concentration demands proved to be risk factors for the occurrence of low back pain, even after controlling for age, sex, educational level, and duration of employment in a specific occupation.

Childhood exposure to PM10: relation between personal, classroom, and outdoor concentrations.

Abstract: OBJECTIVES: To investigate the validity of outdoor concentrations of particulate matter < 10 microns diameter (PM10) as a measure of exposure in time series studies, and to study the extent to which differences between personal and outdoor PM10 concentrations can be explained METHODS: Four to eight repeated measurements of personal and outdoor PM10 concentrations were conducted for 45 children, aged 10-12 years, from four schools in Wageningen and Amsterdam, The Netherlands Repeated PM10 measurements in the classrooms were conducted in three of the schools Averaging time was 24 hours for the personal and outdoor measurements, and eight hours (daytime) and 24 hours for the classroom measurements For each child separately, personal exposures were related to outdoor concentrations in a regression analysis The distribution of the individual correlation and regression coefficients was investigated Information about factors that might influence personal exposures was obtained by questionnaire RESULTS: Median Pearson's correlations between personal and outdoor concentrations were 063 for children with parents who did not smoke and 059 for children with parents who smoked For children with parents who did not smoke, excluding days with exposure to environmental tobacco smoke (ETS) improved the correlation to a median R of 073 The mean personal PM10 concentration was 105 micrograms/m3; on average 67 micrograms/m3 higher than the corresponding outdoor concentrations The main part of this difference could be attributed to exposure to ETS, to high PM10 concentrations in the classrooms, and to (indoor) physical activity CONCLUSIONS: The results show a reasonably high correlation between repeated personal and outdoor PM10 measurements within children, providing support for the use of fixed site measurements as a measure of exposure to PM10 in epidemiological time series studies The large differences between personal and outdoor PM10 concentrations probably result from a child's proximity to particle generating sources and particles resuspended by personal activities

Cancer mortality among electric utility workers exposed to polychlorinated biphenyls.

Abstract: OBJECTIVES: To assess whether excess mortality from cancer, malignant melanoma of the skin, and cancers of the brain and liver in particular, is associated with long term occupational exposure to polychlorinated biphenyls (PCBs). METHODS: An epidemiological study of mortality was conducted among 138,905 men employed for at least six months between 1950 and 1986 at five electrical power companies in the United States. Exposures were assessed by panels composed of workers, hygienists, and managers at each company, who considered tasks performed by workers in 28 job categories and estimated weekly exposures in hours for each job. Poisson regression was used to examine mortality in relation to exposure to electrical insulating fluids containing PCBs, controlling for demographic and occupational factors. RESULTS: Neither all cause nor total cancer mortality was related to cumulative exposure to PCB insulating fluids. Mortality from malignant melanoma increased with exposure; rate ratios (RRs) relative to unexposed men for melanoma were 1.23 (95% confidence interval (95% CI) 0.56 to 2.52), 1.71 (0.68 to 4.28) and 1.93 (0.52 to 7.14) for men with 2000-10,000, and > 10,000 hours of cumulative exposure to PCB insulating fluids, respectively, without consideration of latency. Lagging exposure by 20 years yielded RRs of 1.29 (0.76 to 2.18), 2.56 (1.09 to 5.97), and 4.81 (1.49 to 15.50) for the same exposure levels. Mortality from brain cancer was modestly increased among men with 2000-10,000 hours exposure (RR 1.79, 95% CI 0.81 to 3.95), but there were no deaths from brain cancer among the most highly exposed men. A lag of five years yielded slightly increased RRs. Mortality from liver cancer was not associated with exposure to PCB insulating fluids. CONCLUSIONS: This study was larger and provided more detailed information on exposure than past investigations of workers exposed to PCBs. The results suggest that PCBs cause cancer, with malignant melanoma being of particular concern in this industry.

Mortality of doctors in different specialties: findings from a cohort of 20000 NHS hospital consultants.

Abstract: OBJECTIVES: To examine patterns of cause specific mortality in NHS hospital consultants according to their specialty and to assess these in the context of potential occupational exposures. METHODS: A historical cohort assembled from Department of Health records with follow up through the NHS Central Register involving 18,358 male and 2168 female NHS hospital consultants employed in England and Wales between 1962 and 1979. Main outcome measures examined were cause specific mortality during 1962-92 in all consultants combined, and separately for 17 specialty groups, with age, sex, and calendar year adjusted standardised mortality ratios (SMRs) for comparison with national rates, and rate ratios (RRs) for comparison with rates in all consultants combined. RESULTS: The 2798 deaths at ages 25 to 74 reported during the 30 year study period were less than half the number expected on the basis of national rates (SMR 48, 95% confidence interval (95% CI) 46 to 49). Low mortality was evident for cardiovascular disease, lung cancer, other diseases related to smoking, and particularly for diabetes (SMR 14, 95% CI 6 to 29). Death rates from accidental poisoning were significantly raised among male consultants (SMR 227, 95% CI 135 to 359), the excess being most apparent in obstetricians and gynaecologists (SMR 934); almost all deaths from accidental poisoning involved prescription drugs. A significantly raised death rate from injury and poisoning among female consultants was due largely to a twofold excess of suicide (SMR 215, 95% CI 93 to 423), the rate for this cause being significantly raised in anaesthetists (SMR 405). Compared with all consultants, significantly raised mortality was found in psychiatrists for all causes combined (RR 1.12), ischaemic heart disease (RR 1.18), and injury and poisoning (RR 1.46); in anaesthetists for cirrhosis (RR 2.22); and in radiologists and radiotherapists for respiratory disease (RR 1.68). There were significant excesses of colon cancer in psychiatrists (RR 1.67, compared with all consultants) and ear, nose, and throat surgeons (RR 2.25); melanoma in anaesthetists (RR 3.33); bladder cancer in general surgeons (RR 2.40); and laryngeal cancer in ophthalmologists (RR 7.63). CONCLUSIONS: Lower rates of smoking will have contributed substantially to the low overall death rates found in consultants, but other beneficial health related behaviours, and better access to health care, may have also played a part. The increased risks of accidental poisoning in male consultants, and of suicide in female consultants are of concern, and better preventive measures are needed. The few significant excesses of specific cancers found in certain specialties have no obvious explanation other than chance. A significant excess mortality from cirrhosis in anaesthetists might reflect an occupational hazard and may warrant further investigation.

A systematic review of controlled clinical trials on the prevention of back pain in industry

Abstract: OBJECTIVE: To assess the effectiveness of lumbar supports, education, and exercise in the prevention of back pain in industry. METHODS: A computerised search for controlled clinical trials was conducted. A criteria list was used to assess the methodological quality of the studies. The available evidence for the effectiveness of the interventions was graded with a rating system for the level of evidence. Effect sizes of individual studies were combined if the studies were sufficiently similar. RESULTS: 11 studies were identified for the review. The methodological quality of all studies was low, with a maximum score of three out of seven for internal validity. There was no evidence for the effectiveness of lumbar supports due to contradictory outcomes of the studies. Five of the six studies on education reported no effect. Thus there is limited evidence that education does not help to prevent back pain. All three studies on exercise reported a positive result, indicating limited evidence for the effectiveness of exercise. The combined effect size for exercise was 0.53, which is a medium sized effect. CONCLUSIONS: Although widely used, there is little evaluative research on the preventive measures studied here. The review showed that there is limited evidence that exercise has some effect in the prevention of back pain and that education is not effective. No conclusive evidence was found for or against the effectiveness of lumbar supports. Research of higher methodological quality is needed before firm conclusions on the effectiveness of lumbar supports, education, and exercise in the prevention of back pain in industry can be drawn.

Risks of beryllium disease related to work processes at a metal, alloy, and oxide production plant.

Abstract: OBJECTIVES: To describe relative hazards in sectors of the beryllium industry, risk factors of beryllium disease and sensitisation related to work process were sought in a beryllium manufacturing plant producing pure metal, oxide, alloys, and ceramics. METHODS: All 646 active employees were interviewed; beryllium sensitisation was ascertained with the beryllium lymphocyte proliferation blood test on 627 employees; clinical evaluation and bronchoscopy were offered to people with abnormal test results; and industrial hygiene measurements related to work processes taken in 1984-93 were reviewed. RESULTS: 59 employees (9.4%) had abnormal blood tests, 47 of whom underwent bronchoscopy. 24 new cases of beryllium disease were identified, resulting in a beryllium disease prevalence of 4.6%, including five known cases (29/632). Employees who had worked in ceramics had the highest prevalence of beryllium disease (9.0%). Employees in the pebble plant (producing beryllium metal) who had been employed after 1983 also had increased risk, with a prevalence of beryllium disease of 6.4%, compared with 1.3% of other workers hired in the same period, and a prevalence of abnormal blood tests of 19.2%. Logistic regression modelling confirmed these two risk factors for beryllium disease related to work processes and the dependence on time of the risk at the pebble plant. The pebble plant was not associated with the highest gravimetric industrial hygiene measurements available since 1984. CONCLUSION: Further characterisation of exposures in beryllium metal production may be important to understanding how beryllium exposures confer high contemporary risk of beryllium disease.

Measurement, evaluation, and assessment of occupational exposures to hand-transmitted vibration.

Abstract: The measurement of hand-transmitted vibration converts oscillatory movements to a form in which they can be evaluated with respect to human responses and assessed for their acceptability. This paper presents methods of measurement, evaluation, and assessment currently advocated in standards and other forms of guidance. The degree to which the methods of evaluating different frequencies, directions, and durations of vibration affect the assessment of vibration on different tools is illustrated. With the frequency weighting currently used to allow for the effects of different frequencies there is little need to measure vibration at frequencies as high as 1000 Hz; this has significant implications to the design and evaluation of proposed antivibration devices, including gloves. Without the current frequency weighting, vibration at frequencies greater than 250 Hz can contribute to the magnitude of the vibration, but many common causes of injury from hand-transmitted vibration have their dominant components of vibration below 250 Hz. On many powered tools, although the dominant frequency of vibration is the same before and after frequency weighting, the reported magnitude of vibration is greatly affected by the frequency weighting. On tools with dominant low frequencies, their vibration is rated as being of far greater importance relative to other tools when considering frequency-weighted acceleration than when considering unweighted acceleration. It is shown that the effect of considering three axes of vibration as opposed to one axis has a greater effect on some tools than on others. The uncertainties and assumptions involved in the measurement, evaluation, and assessment of hand-transmitted vibration are reviewed. It is suggested that whereas current decisions on health and welfare should be based on current assessment methods, the measurement and evaluation of hand-transmitted vibration should involve the collection and reporting of data which allow other interpretations in the future.

Time to pregnancy: a measure of reproductive function in either sex. Asclepios Project.

Abstract: INTRODUCTION: Growing evidence of reproductive effects associated with occupational and environmental agents has created the need for research with sensitive and well validated methods. There is a complex relation between manifest effects and underlying pathogenic processes. Conceptions will on average tend to be delayed in a population exposed to an agent that causes embryonic damage, an increase in germ cell mutations, or decreased fertility. STUDYING TIME TO PREGNANCY: Time to pregnancy can be used to measure the degree of delay in conceiving, across the whole continuum of biological fertility, in either men or women. The distribution of time to pregnancy largely reflects a sorting process, as the more fertile couples become progressively less well represented with the passage of time. The basic research strategy is comparison of the time to pregnancy within groups defined by their exposures, allowing for potential confounding factors relating not only to the study subject but also to his or her partner. MEASUREMENT AND VALIDITY: Prospective and retrospective methods are available, and each has strengths and weaknesses. Prospective studies have some theoretical advantages, but have unrepresentative populations and problems of feasibility and cost. Retrospective assessment of time to pregnancy is feasible with a short questionnaire, without intruding into sensitive areas of respondents9 lives, with good validity at the group level, and without the necessity of large populations. Potential biases have been identified that can be minimised by careful design and analysis; the principal remaining problem is difficulty in obtaining exposure data retrospectively.

Exposure-response analysis of risk of respiratory disease associated with occupational exposure to chrysotile asbestos.

Abstract: OBJECTIVES: To evaluate alternative models and estimate risk of mortality from lung cancer and asbestosis after occupational exposure to chrysotile asbestos. METHODS: Data were used from a recent update of a cohort mortality study of workers in a South Carolina textile factory. Alternative exposure-response models were evaluated with Poisson regression. A model designed to evaluate evidence of a threshold response was also fitted. Lifetime risks of lung cancer and asbestosis were estimated with an actuarial approach that accounts for competing causes of death. RESULTS: A highly significant exposure-response relation was found for both lung cancer and asbestosis. The exposure-response relation for lung cancer seemed to be linear on a multiplicative scale, which is consistent with previous analyses of lung cancer and exposure to asbestos. In contrast, the exposure-response relation for asbestosis seemed to be nonlinear on a multiplicative scale in this analysis. There was no significant evidence for a threshold in models of either the lung cancer or asbestosis. The excess lifetime risk for white men exposed for 45 years at the recently revised OSHA standard of 0.1 fibre/ml was predicted to be about 5/1000 for lung cancer, and 2/1000 for asbestosis. CONCLUSIONS: This study confirms the findings from previous investigations of a strong exposure-response relation between exposure to chrysotile asbestos and mortality from lung cancer, and asbestosis. The risk estimates for lung cancer derived from this analysis are higher than those derived from other populations exposed to chrysotile asbestos. Possible reasons for this discrepancy are discussed.

People can detect poor air quality well below guideline concentrations: a prevalence study of annoyance reactions and air pollution from traffic.

Abstract: OBJECTIVES: Motor vehicle exhaust fumes are the main source of atmospheric pollution in cities in industrialised countries. They cause respiratory disease and annoy people exposed to them. The relation between ambient exposure to air pollution mainly from motor vehicles and annoyance reactions in a general population was assessed. Also, the importance of factors such as age, sex, respiratory disease, access to the use of a car, and smoking habits on the reporting of these reactions was studied. METHODS: A postal questionnaire was sent out in 55 urban areas in Sweden that had nearly identical air quality monitoring stations of the urban air monitoring network. From each area, 150 people aged 16-70 were randomly selected. The questionnaire contained questions on perception of air quality as well as a question on how often exhaust fumes were annoying. RESULTS: Six-monthly nitrogen dioxide concentrations correlated consistently with the prevalence of reported annoyance related to air pollution and traffic exhaust fumes. Black smoke and sulphur dioxide had no significant effects. The frequency of reporting annoyance reactions was higher among people with asthma, women, and people with lack of access to a car. CONCLUSIONS: In this study town dwellers could detect poor air quality at concentrations well below current guidelines for outdoor air pollution. This suggests that questionnaire studies have a place in monitoring air quality.

Evaluation of the Q16 questionnaire on neurotoxic symptoms and a review of its use.

Abstract: OBJECTIVES: The questionnaire 16 (Q16) is commonly used to study prevalences of neurotoxic symptoms among workers exposed to organic solvents. It has also been recommended that exposed workers reporting more than six symptoms should be referred for further examination of possible chronic toxic encephalopathy. It would be useful to know whether symptoms reported in the questionnaire also reflect impairment of similar functions measured with objective or semiobjective methods in a formerly highly exposed group. METHODS: 135 painters and 71 carpenters answered the Q16, were interviewed about symptoms compatible with an organic brain damage, and took a battery of psychometric tests. A subsample of 52 painters and 45 carpenters were interviewed for psychiatric diagnosis according to Diagnostic and Statistical Manual for Mental Disorders, 3rd version (DSM III) and their vibration thresholds in hands and feet were measured. The entire group was followed up in the register of diagnoses at early retirement 1971-93. The lifetime exposure to organic solvents was assessed. Current exposure to organic solvents was found to be low or none. RESULTS: The prevalence of people with more than six symptoms in the Q16 rose with increasing cumulative exposure to solvents. The sensitivity of the questionnaire (more than six symptoms) to detect people who were assessed to exhibit symptoms compatible with an organic brain damage was only 38%. One of seven people who had retired early with a diagnosis compatible with a chronic toxic encephalopathy, and two of five people with a psychiatric diagnosis compatible with this condition, had more than six symptoms in the Q16. The agreement between Q16 replies and psychometric test results, as well as other examinations, was low. CONCLUSIONS: The notable exposure-response relation indicates that the questionnaire is useful for comparison of groups with different exposures to organic solvents. There was low agreement between the number of symptoms on the questionnaire and the assessment of symptoms compatible with organic brain damage, as well as psychiatric, or early retirement diagnoses compatible with chronic toxic encephalopathy. The questionnaire does not seem useful for screening of patients with chronic toxic encephalopathy in groups without ongoing exposure to organic solvents.

Physician based surveillance system for occupational respiratory diseases: the experience of PROPULSE, Québec, Canada.

Abstract: OBJECTIVE: To evaluate the feasibility of implementing a physician based surveillance system of occupational respiratory diseases (PROPULSE) in Quebec with regard to physician participation rate, characteristics of reported cases, and comparison with official statistics from the Workers' Compensation Board (WCB). METHODS: All chest physicians and allergists in Quebec were asked to report suspected new cases of occupational respiratory diseases, on a monthly basis, between October 1992 and September 1993. For each case, personal information was collected and the physician's opinion on whether the condition was related to work was categorised as highly likely, likely, and unlikely. RESULTS: Of the 161 physicians initially approached, 68% participated. Physicians rated 48% of suspected cases as highly likely, 29% as likely, and 20% as unlikely. The most often reported diagnosis was asthma (63%), followed by diseases related to asbestos (16%). Silicosis was less frequent (5%) but it was reported for six workers under 40 of whom five were involved in sandblasting activities. The high proportion of cases of asthma probably reflects the increasing importance of this disease but may also reflect the different patterns of reporting among physicians with different expertise. The distribution of cases by diagnostic category is quite different between the PROPULSE system and that of the WCB (annual mean number of compensated cases during a four year period). Asthma and allergic alveolitis are more frequent in PROPULSE, reactive airways dysfunction syndrome are about the same in both systems, and other diseases are more frequent among compensated cases. The most frequent sensitising agents reported for asthma were the same in both systems (isocyanates, flour, and wood dust). 15% of the PROPULSE cases were not covered by the WCB, and therefore would not be found in the board's official statistics. CONCLUSIONS: A physician based reporting procedure can be implemented as part of a surveillance system to supplement data from other sources and thus provide a better understanding of the occurrence of occupational respiratory diseases.

A case-control study to investigate the risk of leukaemia associated with exposure to benzene in petroleum marketing and distribution workers in the United Kingdom.

Abstract: OBJECTIVES: To investigate the risk of leukaemia in workers in the petroleum distribution industry who were exposed to low levels of benzene. METHODS: From the cohort of distribution workers, 91 cases were identified as having leukaemia on either a death certificate or on cancer registration. These cases were compared with controls (four per case) randomly selected from the cohort, who were from the same company as the respective case, matched for age, and alive and under follow up at the time of case occurrence. Work histories were collected for the cases and controls, together with information about the terminals at which they had worked, fuel compositions, and occupational hygiene measurements of benzene. These data were used to derive quantitative estimates of personal exposure to benzene. Odds ratios (OR) were calculated conditional on the matching, to identify those variables in the study which were associated with risk of leukaemia. Examination of the potential effects of confounding and other variables was carried out with conditional logistic regression. Analyses were carried out for all leukaemia and separately for acute lymphoblastic, chronic lymphocytic, acute myeloid and monocytic, and chronic myeloid leukaemias. RESULTS: There was no significant increase in the overall risk of all leukaemias with higher cumulative exposure to benzene or with intensity of exposure, but risk was consistently doubled in subjects employed in the industry for > 10 years. Acute lymphoblastic leukaemia tended to occur in workers employed after 1950, who started work after the age of 30, worked for a short duration, and experienced low cumulative exposure with few peaks. The ORs did not increase with increasing cumulative exposure. The risk of chronic lymphocytic leukaemia seemed to be related most closely to duration of employment and the highest risk occurred in white collar workers with long service. These workers had only background levels of benzene exposure. There was no evidence of an association of risk with any exposure variables, and no evidence of an increasing risk with increasing cumulative exposure, mean intensity, or maximum intensity of exposure. The patterns of risk for acute myeloid and monocytic leukaemia were different from those of the lymphoid subgroups, in which duration of employment was the variable most closely related to risk. Risk was increased to an OR of 2.8 (95% confidence interval (95% CI) 0.8 to 9.4) for a cumulative exposure between 4.5 and 45 ppm-years compared with

Lung cancer mortality in a cohort of workers employed at a cadmium recovery plant in the United States: an analysis with detailed job histories.

Abstract: OBJECTIVES: To identify and measure any relations between occupational exposure to cadmium compounds (oxide, sulphide, and sulphate) and the risk of mortality from lung cancer. METHODS: The mortality experience of 571 male production workers from a cadmium recovery facility in the United States was investigated for the period 1940-82. All study subjects were first employed in the period 1926-69; they had all been employed for at least six months between 1 January 1940 and 31 December 1969. Newly abstracted detailed job histories for the period 1926-76 were combined with assessments of exposures to cadmium over time to develop individual estimates of cumulative exposure to cadmium (total exposure and exposures received both in the presence and absence of "high" exposures to arsenic trioxide). Poisson regression was used to investigate risks of mortality from lung cancer in relation to four concentrations of cumulative exposure to cadmium ( 2000 mg.m-3.days). RESULTS: After adjustment for age attained, year of hire, and Hispanic ethnicity, there was a significant positive trend (P < 0.05) between cumulative exposure to cadmium and risks of mortality from lung cancer. Relative to a risk of unity for the lowest exposure category (first level), risks were 2.30 (95% confidence interval (95% CI) 0.72 to 7.36), 2.83 (95% CI 0.75 to 10.72), and 3.88 (95% CI 1.04 to 14.46) for the second, third, and fourth categories, respectively. Similar findings were obtained after adjustment for age only. Trends were more pronounced when employment histories were lagged first by 10 years and then by 20 years. A separate analysis examined the independent effects of exposure to cadmium received in the presence of high exposures to arsenic trioxide (mainly cadmium oxide) and exposures to cadmium received without such exposure to arsenic (mainly cadmium sulphide and cadmium sulphate). A significant trend for a risk of lung cancer was found only for exposures to cadmium received in the presence of arsenic trioxide. CONCLUSIONS: Hypotheses which are consistent with the study findings include: (a) cadmium oxide in the presence of arsenic trioxide is a human lung carcinogen, (b) cadmium oxide and arsenic trioxide are human lung carcinogens and cadmium sulphate and cadmium sulphide are not (or they are less potent carcinogens), or (c) arsenic trioxide is a human lung carcinogen and cadmium oxide, cadmium sulphate, and cadmium sulphide are not. There were only 21 deaths from lung cancer available for this analysis and it is impossible to gauge which, if any, of these hypotheses are correct.

Prevalence of occupational lung disease among Botswana men formerly employed in the South African mining industry.

Abstract: OBJECTIVE: To determine whether previous health experiences affect the prevalence of occupational lung disease in a semirural Botswanan community where there is a long history of labour recruitment to South African mines. METHOD: A cross sectional prevalence study of 304 former miners examined according to a protocol including a questionnaire, chest radiograph, spirometry, and medical examination. RESULTS: Overall mean age was 56.7 (range 28-93) years, mean duration of service 15.5 (range 2-42) years. 26.6% had a history of tuberculosis. 23.3% had experienced a disabling occupational injury. Overall prevalence of pnemoconiosis (> 1/0 profusion, by the International Labour Organisation classification) was 26.6%-31.0%, and 6.8% had progressive massive fibrosis (PMF). Many were entitled to compensation under South African law. Both radiograph readers detected time response relations between pneumoconiosis and PMF among the 234 underground gold miners. PMF could result from < 5 years of exposure, but was not found < 15 years after first exposure. Both pulmonary tuberculosis (PTB) and pneumoconiosis were found to be associated with airflow limitation. CONCLUSIONS: Former miners in Botswana have a high prevalence of previously unrecognised pneumoconiosis, indicative of high previous exposures to fibrogenic respirable dust. Their pneumoconiosis went unrecognised because they had no access to surveillance after employment. Inadequate radiographic surveillance or failure to act on results when employed or when leaving employment at the mines could have contributed to under recognition. Community based studies of former miners are essential to fully evaluate the effects of mining exposures. Our findings indicate a failure of established measures to prevent or identify pneumoconiosis while these miners were in employment and show that few of the social costs of occupational lung diseases are borne by mining companies through the compensation system.

Occupational asthma in New Zealanders: a population based study.

Abstract: OBJECTIVES: To examine the effect of occupation on respiratory symptoms in a randomly selected adult population aged 20-44 years. METHODS: It is based on the phase II sampling of the New Zealand part of the European Community respiratory health survey. 1609 people (63.9% response rate) completed a detailed respiratory questionnaire. Of those responding, 1174 (73%) underwent skin tests and 1126 (70%) attended to undergo methacholine bronchial challenge. Current occupation was recorded and a previous occupation was also recorded if it had led to respiratory problems. 21 occupational groups were used for analysis for the five definitions of asthma wheezing in the previous 12 months; symptoms related to asthma; bronchial hyperresponsiveness (BHR); BHR with wheezing in the previous 12 months; and BHR with symptoms related to asthma. RESULTS: Prevalence odds ratios (ORs) were significantly increased for farmers and farm workers (OR 4.16, 95% confidence interval (95% CI) 1.33 to 13.1 for the combination of wheezing and BHR). Increased risks of prevalence of asthma were also found for laboratory technicians, food processors (other than bakers), chemical workers, and plastic and rubber workers. Workers had also been divided into high and low risk exposure categories according to relevant publications. The prevalence of wheezing was greater in the high risk group (OR 1.57, 95% CI 0.83 to 2.95) than in the low risk group. Atopy was associated with asthma, but the prevalence of atopy did not differ significantly between occupational exposure groups. The attributable risk of wheezing that occurred after the age of 15 years and that was estimated to be due to occupational exposure (based on the defined high risk group) was 1.9%, but this increased to 3.1% when farmers and food processors (other than bakers) were also included in the high risk group. CONCLUSIONS: This population based study has identified certain occupations significantly associated with combinations of asthmatic symptoms and BHR.

Medical insurance claims associated with international business travel.

Abstract: OBJECTIVES: Preliminary investigations of whether 10,884 staff and consultants of the World Bank experience disease due to work related travel. Medical insurance claims filed by 4738 travellers during 1993 were compared with claims of non-travellers. METHODS: Specific diagnoses obtained from claims were analysed overall (one or more v no missions) and by frequency of international mission (1, 2-3, or > or = 4). Standardised rate of claims ratios (SSRs) for each diagnostic category were obtained by dividing the age adjusted rate of claims for travellers by the age adjusted rate of claims for non-travellers, and were calculated for men and women travellers separately. RESULTS: Overall, rates of insurance claims were 80% higher for men and 18% higher for women travellers than their non-travelling counterparts. Several associations with frequency of travel were found. SRRs for infectious disease were 1.28, 1.54, and 1.97 among men who had completed one, two or three, and four or more missions, and 1.16, 1.28, and 1.61, respectively, among women. The greatest excess related to travel was found for psychological disorders. For men SRRs were 2.11, 3.13, and 3.06 and for women, SRRs were 1.47, 1.96, and 2.59. CONCLUSIONS: International business travel may pose health risks beyond exposure to infectious diseases. Because travellers file medical claims at a greater rate than non-travellers, and for many categories of disease, the rate of claims increases with frequency of travel. The reasons for higher rates of claims among travellers are not well understood. Additional research on psychosocial factors, health practices, time zones crossed, and temporal relation between travel and onset of disease is planned.

Transient increase of serum Clara cell protein (CC16) after exposure to smoke.

Abstract: OBJECTIVES: Smoke inhalation is a well known cause of airways injury in firefighting personnel. The aim of this study was to evaluate whether toxic effects of smoke on the respiratory tract can be detected by measuring Clara cell protein (CC16), a recently described serum marker of lung function. METHODS: CC16 was measured by a sensitive latex immunoassay in the serum of six voluntary firefighters from a chemical plant who had inhaled smoke from the combustion of polypropylene for about 20 minutes. The protein was measured immediately after the fire and 10 days later. The values were compared with those of six control workers examined simultaneously. RESULTS: The mean (SD) concentration of CC16 in the serum of firefighters after the fire (54.4 (34.9) micrograms/l) was significantly higher than that of controls (19.5 (11.7), P = 0.04). 10 days later, serum CC16 from firefighters had returned to the concentrations found in controls (15.9 (2.76) v 17.7 (12.5)). With the values at day 10 as a baseline, the rise of serum CC16 was estimated at 328% on average (range 100%-564%). These changes were found in the absence of any functional sign of lung impairment. CONCLUSION: Acute exposure to smoke results in a transient increase of CC16 in serum due most likely to an increased permeability of the bronchoalveolar/blood barrier. Serum CC16 seems potentially to be a new biomarker for the early detection of acute airways injury caused by smoke.

Risk of stillbirth from occupational and residential exposures.

Abstract: OBJECTIVES: To analyse the risk of stillbirth from 12 residential and occupational maternal exposures during pregnancy. METHODS: Stillbirths and neonatal deaths in 1984 within 24 hours of birth from 10 California counties were identified from death certificates. Controls were randomly selected from live births born in 1984 and frequency matched to cases by maternal age and county. Data sources included vital statistics and a self-administered postal questionnaire. Logistic regression and proportional hazards modelling were performed; the proportional hazards considered the truncated opportunity for exposure among cases. Special focus was given to two cause of deaths groups: congenital anomalies (12% of deaths) and complications of the placenta, cord, and membranes (37% of deaths). RESULTS: Occupational exposure to pesticides during the first two months of gestation was positively associated with stillbirths due to congenital anomalies (odds ratio (OR) 2.4, 95% confidence interval (95% CI) 1.0 to 5.9), and during the first and second trimesters with stillbirths due to all causes of death (risk ratios (RR) 1.3-1.4, 95% CI 1.0 to 1.7) and stillbirths due to complications of the placenta, cord, and membranes (RR 1.6-1.7, 95% CI 1.1 to 2.3). Occupational exposure to video display terminals in the third trimester was found to have a modest inverse association with stillbirths (RR 0.7, 95% CI 0.6, 0.9). Home pesticide exposure was positively associated with stillbirths due to congenital anomalies (OR 1.7, 95% CI 1.0 to 2.9). CONCLUSIONS: Occupational exposure to pesticides, especially during early pregnancy, had a clear positive association with stillbirths regardless of cause of death. Methodologically, this study of stillbirths is unique in its analysis of specific causes of death and use of time specific exposure windows.

Occupational exposure to dust: inflammation and ischaemic heart disease.

Abstract: OBJECTIVES: To review the possible association between occupational exposure to dust and ischaemic heart disease (IHD). METHODS: A literature search was performed of relevant studies regarding IHD in specific exposures to dust. The chosen exposures were arsenic, asbestos, beryllium, lead, polycyclic aromatic hydrocarbons, and quartz. The chosen occupations were farmers, paper and paper pulp workers, sawyers, and welders. DISCUSSION: A theory was launched in 1995 that urban particulate air pollution may provoke alveolar inflammation, with release of mediators capable of increasing blood coagulability in susceptible people and cause cardiovascular deaths. The present review expands this hypothesis and links occupational exposure to inhaled particles with the occurrence of ischaemic heart disease. CONCLUSION: This hypothesis should be tested by comparing the concentrations of fibrinogen in workers exposed and nonexposed to particles with control for other possible confounders such as smoking habits.

Structural nerve changes at wrist level in workers exposed to vibration.

Abstract: OBJECTIVES: To analyse the character of morphological changes occurring in a well defined peripheral nerve in humans exposed to vibration from hand held tools. METHODS: Biopsies of the dorsal interosseus nerve just proximal to the wrist were taken from 10 men exposed to vibration and from 12 male age matched necropsy controls. The nerve was resected for pain relief either as the sole procedure or in conjunction with carpal tunnel release. All specimens were sectioned and examined by light microscopy in standard sections, thin epon sections, and teasing preparations. RESULTS: The combined results of the analyses showed pathological changes in all 10 patients dominated by breakdown of myelin and by interstitial and perineurial fibrosis. All but one of the 12 controls were normal. CONCLUSION: These findings often show severe nerve injury previously not described at this level. They indicate that demyelination may be the primary lesion in neuropathy induced by vibration followed by fibrosis associated with incomplete regeneration or with organisation of oedema. Vibration can induce structural changes in peripheral nerves just proximal to the wrist and such changes may constitute a structural component in carpal tunnel syndrome among people exposed to vibration. This may help to explain the poor results achieved by carpal tunnel release in these patients.