Smoking characteristics of US workers, 1978-1980

Supplementing claims data analysis using self-reported data to develop a probabilistic phenotype model for current smoking status

OBJECTIVES

Smoking status is poorly record in US claims data. IBM MarketScan Commercial is a claims database that can be linked to an additional health risk assessment with self-reported smoking status for a subset of 1,966,174 patients. We investigate whether this subset could be used to learn a smoking status phenotype model generalizable to all US claims data that calculates the probability of being a current smoker.

METHODS

251,643 (12.8%) had self-reported their smoking status as 'current smoker'. A regularized logistic regression model, the Current Risk of Smoking Status (CROSS), was trained using the subset of patients with self-reported smoking status. CROSS considered 53,027 candidate covariates including demographics and conditions/drugs/measurements/procedures/observations recorded in the prior 365 days, The CROSS phenotype model was validated across multiple other claims data.

RESULTS

The internal validation showed the CROSS model achieved an area under the receiver operating characteristic curve (AUC) of 0.76 and the calibration plots indicated it was well calibrated. The external validation across three US claims databases obtained AUCs ranging between 0.82 and 0.87 showing the model appears to be transportable across Claims data.

CONCLUSION

CROSS predicts current smoking status based on the claims records in the prior year. CROSS can be readily implemented to any US insurance claims mapped to the OMOP common data model and will be a useful way to impute smoking status when conducting epidemiology studies where smoking is a known confounder but smoking status is not recorded. CROSS is available from https://github.com/OHDSI/StudyProtocolSandbox/tree/master/SmokingModel.

Mortality among Coast Guard Shipyard workers: A retrospective cohort study of specific exposures

In a previous analysis of a cohort of shipyard workers, we found excess mortality from all causes, lung cancer, and mesothelioma for longer work durations and in specific occupations. Here, we expand the previous analyses by evaluating mortality associated with 5 chemical exposures: asbestos, solvents, lead, oils/greases, and wood dust. Data were gathered retrospectively for 4,702 workers employed at the Coast Guard Shipyard, Baltimore, MD (1950-1964). The cohort was traced through 2001 for vital status. Associations between mortality and these 5 exposures were calculated via standardized mortality ratios (SMRs). We found all 5 substances to be independently associated with mortality from mesothelioma, cancer of the respiratory system, and lung cancer. Findings from efforts to evaluate solvents, lead, oils/greases, and wood dust in isolation of asbestos suggested that the excesses from these other exposures may be due to residual confounding from asbestos exposure.

Ischaemic heart disease mortality and years of work in trucking industry workers

OBJECTIVES

Evidence from general population-based studies and occupational cohorts has identified air pollution from mobile sources as a risk factor for cardiovascular disease. In a cohort of US trucking industry workers, with regular exposure to vehicle exhaust, the authors previously observed elevated standardised mortality ratios for ischaemic heart disease (IHD) compared with members of the general US population. Therefore, the authors examined the association of increasing years of work in jobs with vehicle exhaust exposure and IHD mortality within the cohort.

METHODS

The authors calculated years of work in eight job groups for 30,758 workers using work records from four nationwide companies. Proportional hazard regression was used to examine relationships between IHD mortality, 1985-2000, and employment duration in each job group.

RESULTS

HRs for at least 1 year of work in each job were elevated for dockworkers, long haul drivers, pick-up and delivery drivers, combination workers, hostlers, and shop workers. There was a suggestion of an increased risk of IHD mortality with increasing years of work as a long haul driver, pick-up and delivery driver, combination worker, and dockworker.

CONCLUSION

These results suggest an elevated risk of IHD mortality in workers with a previous history of regular exposure to vehicle exhaust.

Occupational lung cancer in US women, 1984-1998

BACKGROUND

Lung cancer is the leading cause of cancer death in US women, accounting for 72,130 deaths in 2006. In addition to smoking cessation, further reduction of the burden of lung cancer mortality can be made by preventing exposure to occupational lung carcinogens. Data for occupational exposures and health outcomes of US working women are limited.

METHODS

Population-based mortality data for 4,570,711 women who died between 1984 and 1998 in 27 US States were used to evaluate lung cancer proportionate mortality over time by the usual occupation and industry reported on death certificates. Lung cancer proportionate mortality ratios were adjusted for smoking, using data from the National Health Interview Survey (NHIS) and the American Cancer Society's Cancer Prevention Study II.

RESULTS

Analyses revealed that 194,382 white, 18,225 Black and 1,515 Hispanic women died 1984-1998 with lung cancer reported as the underlying cause of death. Following adjustment for smoking, significant excess proportionate lung cancer mortality was observed among US women working in the US manufacturing; transportation; retail trade; agriculture, forestry, and fishing; and nursing/personal care industries. Women employed in precision production, technical, managerial, professional specialty, and administrative occupations experienced some of the highest significantly excess proportionate lung cancer mortality during 1984-1998.

CONCLUSIONS

The results of our study point to significantly elevated risks for lung cancer after adjustment for smoking among women in several occupations and industries. Because 6-17% of lung cancer in US males is attributable to known exposures to occupational carcinogens, and since synergistic interactions between cigarette smoke and other occupational lung carcinogens have been noted, it is important to continue research into the effects of occupational exposures on working men and women.

Occupational status, work-site cessation programs and policies and menthol smoking on quitting behaviors of US smokers

AIM

This exploratory study sought to examine the relationships among occupational status, menthol smoking preference and employer-sponsored smoking cessation programs and policies on quitting behaviors.

DESIGN

Data for this cross-sectional study were obtained from the 2006 Tobacco Use Supplement to the Current Population Survey (TUS CPS), a large national survey representative of the civilian population, containing approximately 240,000 respondents. The total sample for the current study was 30,176.

MEASUREMENTS

The TUS CPS regularly collects data on cigarette prevalence, quitting behaviors, smoking history and consumption patterns. We performed a logistic regression with 'life-time quitting smoking for 1 day or longer because they were trying to quit' as outcome variable. Independent variables included type of occupation, employer-sponsored cessation programs and policies and menthol status.

FINDINGS

When controlling for occupational status and work-place policies, there were no differences for menthol versus non-menthol smokers on quitting behaviors [odds ratio (OR) = 0.98; 95% confidence interval (CI) = 0.83, 1.15]. Service workers were less likely to quit compared with white-collar workers (OR = 0.80; 95% CI = 0.69, 0.94), and those with no employer-sponsored cessation program were less likely to quit (OR = 0.70; 95% CI = 0.60, 0.83). White-collar workers, compared with blue-collar and service workers, were more likely to have a smoking policy in the work area (93% versus 86% versus 88%, respectively).

CONCLUSIONS

When occupational status and work-place smoking policies are controlled for, smokers of menthol cigarettes in the United States appear to have similar self-reported life-time rates of attempts to stop smoking to non-menthol smokers.

Partner smoking characteristics: Associations with smoking and quitting among blue-collar apprentices

BACKGROUND

Studies suggest that the social context of blue-collar workers contribute to their low smoking cessation rates. However, little is known on the effect of partner smoking and requests to quit on workers' cessation attempts.

METHODS

Using data from a longitudinal smoking cessation intervention, multivariable logistic regression models were constructed to investigate the association of partner smoking characteristics with cessation among blue-collar apprentices.

RESULTS

Smokers were more likely to have partners who smoke (OR 13.06; 95% CI 8.52-20.01). Partner's request to quit was associated with higher odds of smoking cessation at 1 month (OR 3.74; 95% CI 2.49-5.63) and 6 months (OR 1.90; 95% CI 1.06-3.41) post-intervention. Having a partner who smoked was associated with lower odds of smoking cessation at 1 month (OR 0.41; 95% CI 0.27-0.62), but not 6 months post-intervention.

CONCLUSIONS

Results suggest that smoking cessation interventions that include partner support might improve cessation among blue-collar smokers.

Meta-analyses of occupational exposure as a painter and lung and bladder cancer morbidity and mortality 1950-2008

The International Agency for Research on Cancer (IARC) classified occupational painting as a human carcinogen based on lung and bladder cancers; however, no specific exposures were implicated. The authors conducted comprehensive meta-analyses of the epidemiological literature on occupational painting and these cancers. The authors abstracted study results and confounder information, and used quantile plots and regression models to evaluate heterogeneity and publication bias. Summary risk estimates were derived and sensitivity analyses performed to evaluate smoking, socioeconomic status (SES), and exposure variables. Where applicable, a Bayesian approach was used to externally adjust for smoking, a major risk factor for both cancers. For lung cancer cohort mortality studies, publication bias and heterogeneity were seen, and earlier studies reported higher risk estimates than later studies. Overall lung cancer summary risk estimates were 1.29 for case-control and 1.22 and 1.36 for cohort morbidity and mortality studies, respectively, and risk estimates for bladder cancer were 1.28 for case-control and 1.14 and 1.27 for cohort morbidity and mortality studies, respectively (all statistically significant). Risks did not differ between painters and mixed occupations. Nonsignificant summary estimates resulted for lung and bladder cancers when controlling for SES, or externally adjusting for smoking in lung cancer studies. Summary risks varied by control source for case-control studies. Residual confounding by smoking and SES, lack of exposure group effect, and publication bias limit the ability of the meta-analyses to explain associations observed between occupational painting and lung and bladder cancers. Given the long latencies for lung and bladder cancers, these weak associations, if real, may not be elucidated through studies of occupational painting today.

A follow-up study of mortality among women in the North American synthetic rubber industry

OBJECTIVE

To evaluate mortality from cancer and other diseases among 4863 women employed at eight North American styrene-butadiene rubber plants. Cancers of the lymphohematopoietic tissues, breast, and ovary were of strongest a priori interest.

METHODS

Cause-specific standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were estimated.

RESULTS

The observed number of deaths was approximately equal to that expected for leukemia (10 observed/13 expected), Hodgkin lymphoma (1/1.6), multiple myeloma (7/7.9), non-Hodgkin lymphoma (15/14), and cancers of the breast (72/74) and ovary (21/22). Ever-hourly women had more than expected deaths from lung (47/30, SMR = 159, CI = 117 to 211) and bladder (6/1.8, SMR = 332, CI = 122 to 723) cancers. Exposure-response analysis, done only for lung cancer, indicated no trend for butadiene or styrene.

CONCLUSIONS

The observed excesses of lung and bladder cancers may be attributable to nonoccupational factors rather than to workplace exposures.

Prevalence and correlates of active and ever-smokers in metropolitan China

This study investigated the prevalence and demographic correlates of active and ever-smokers in Beijing and Shanghai. Using a multi-stage household probability sampling method, 5201 participants aged 18-70 underwent face-to-face interviews using the Composite International Diagnostic Interview. 67.1% and 55.5% of male and 7.1% and 5.5% of female respondents were ever-smokers and active smokers respectively. Quitting was less common by proportion among those no longer married or never-married, middle-aged or working adults. After adjusting for other sociodemographic factors, the oldest age-group (>54 years) showed a significantly negative association with active smoking while those no longer married had significantly positive association with active smoking, among ever-smokers. Although the high prevalence of male smoking in Beijing and Shanghai was expected, the prevalence of female smoking was significantly higher than those found in previous surveys. This pattern of more female smoking not accompanied by an obvious decrease in male smoking defies the expectation of an orderly transition of smoking patterns and may foreshadow smoking patterns in other parts of China.

A population-based cohort study of occupational exposure to magnetic fields and cardiovascular disease mortality

PURPOSE

This cohort study aims to examine cardiovascular disease (CVD) mortality risks among workers in occupations potentially exposed to magnetic fields (MF).

METHODS

Risks for major CVD mortality by potential job-related MF exposure were examined in a sample of U.S. workers from the National Longitudinal Mortality Study using multivariate proportional hazards models.

RESULTS

After adjustment for demographic factors, there were no significant excess risks between individuals with medium (0.15 to <0.20 microT), high (0.20 to < 0.30 microT), or very high (>/= 0.30 microT) exposure levels as compared with individuals with background exposure levels of MF (<0.15 microT) for the CVD mortality outcomes. Indirect adjustment for potential confounding by current smoking prevalence did not change the pattern of these results.

CONCLUSION

Our study does not provide evidence for an association between occupational MF exposure and CVD mortality risk.

Using the National Health Interview Survey to understand and address the impact of tobacco in the United States: past perspectives and future considerations

OBJECTIVE

The National Health Interview Survey (NHIS) is a continuous, nationwide, household interview survey of the civilian noninstitutionalized population of the United States. This annual survey is conducted by the National Center for Health Statistics, part of the Centers for Disease Control and Prevention. Since 1965, the survey and its supplements have provided data on issues related to the use of cigarettes and other tobacco products. This paper describes the survey, provides an overview of peer-reviewed and government-issued research that uses tobacco-related data from the NHIS, and suggests additional areas for exploration and directions for future research.

DATA SOURCES

We performed literature searches using the PubMed database, selecting articles from 1966 to 2008. Study selection. Inclusion criteria were relevancy to tobacco research and primary use of NHIS data; 117 articles met these criteria. Data extraction and synthesis. Tobacco-related data from the NHIS have been used to analyze smoking prevalence and trends; attitudes, knowledge, and beliefs; initiation; cessation and advice to quit; health care practices; health consequences; secondhand smoke exposure; and use of smokeless tobacco. To date, use of these data has had broad application; however, great potential still exists for additional use.

CONCLUSION

NHIS data provide information that can be useful to both practitioners and researchers. It is important to explore new and creative ways to best use these data and to address the full range of salient tobacco-related topics. Doing so will better inform future tobacco control research and programs.

Proportionate mortality study of the United Association of Journeymen and Apprentices of the Plumbing and Pipe Fitting Industry

BACKGROUND

This study examined causes of deaths among unionized plumbers, pipefitters and allied trades.

METHODS

Deaths of union members from the years 1971, 1979, 1987, and 1995 were selected as a representative sample from a computer file provided by the union. These years provided 15,411 deaths for proportionate mortality ratio (PMR) analysis.

RESULTS

PMRs for lung cancer and asbestosis were significantly elevated compared to U.S. white males. PMRs for chronic disease of the endocardium and cardiomyopathy were also elevated. Elevations were not observed in other a priori causes: laryngeal cancer, lymphatic cancer, and neurological disorders. PMRs for transportation accidents for pipe/steam-fitters were elevated in 1971 and 1979, but not in 1987 or 1995.

CONCLUSION

Despite the limitations of a PMR analysis, study results indicate mortality related to asbestos exposure is, and will continue to be, an area of concern for members of the union.

Lung cancer and vehicle exhaust in trucking industry workers

BACKGROUND

An elevated risk of lung cancer in truck drivers has been attributed to diesel exhaust exposure. Interpretation of these studies specifically implicating diesel exhaust as a carcinogen has been limited because of limited exposure measurements and lack of work records relating job title to exposure-related job duties.

OBJECTIVES

We established a large retrospective cohort of trucking company workers to assess the association of lung cancer mortality and measures of vehicle exhaust exposure.

METHODS

Work records were obtained for 31,135 male workers employed in the unionized U.S. trucking industry in 1985. We assessed lung cancer mortality through 2000 using the National Death Index, and we used an industrial hygiene review and current exposure measurements to identify jobs associated with current and historical use of diesel-, gas-, and propane-powered vehicles. We indirectly adjusted for cigarette smoking based on an industry survey.

RESULTS

Adjusting for age and a healthy-worker survivor effect, lung cancer hazard ratios were elevated in workers with jobs associated with regular exposure to vehicle exhaust. Mortality risk increased linearly with years of employment and was similar across job categories despite different current and historical patterns of exhaust-related particulate matter from diesel trucks, city and highway traffic, and loading dock operations. Smoking behavior did not explain variations in lung cancer risk.

CONCLUSIONS

Trucking industry workers who have had regular exposure to vehicle exhaust from diesel and other types of vehicles on highways, city streets, and loading docks have an elevated risk of lung cancer with increasing years of work.

Tobacco smoking by occupation in Australia and the United States: a review of national surveys conducted between 1970 and 2005

Tobacco use represents a key issue in workplace health, and much can be learned from countries where occupational smoking data has been regularly collected on a national basis. This article reviews national smoking surveys previously conducted in Australia and the United States between 1970 and 2005, and examines their relevance to the field of occupational tobacco control. When the first preliminary research was undertaken over 35 years ago, tobacco smoking was a regular feature in the general population of both countries, albeit with higher rates often documented among blue collar workers. Recent national investigations however, suggest that certain historical differences in smoking prevalence rates by occupation are persisting as we enter the 21st century. Detailed examination also indicates that employee sub-groups, such as cleaners and construction workers, are now bearing much of the occupational smoking burden in Australia and the United States. As such, there is an urgent need for more aggressive and finely targeted tobacco control activities in the workplace, as well as increased cooperation between tobacco control organizations, labor unions and other stakeholders, so that they may more effectively combat this ongoing threat to workers' health.

A decade of work on organized labor and tobacco control: reflections on research and coalition building in the United States

Labor unions can and should make strong allies in tobacco control efforts. Through much of the 1980s and 1990s, however, the organized labor and tobacco control communities rarely formed coalitions to achieve mutual gains. Recently, labor unions and tobacco control organizations have begun to work together on smoking cessation programs, smoke-free worksite policies, and increased insurance coverage for cessation treatments. This paper explores the historic and present-day intersections among organized labor and tobacco control advocates. We summarize research in this area and report on our recent programmatic efforts to promote collaboration between the labor and tobacco control communities. We discuss lessons learned with the aims of promoting deeper understanding among tobacco control and labor advocates of how each views tobacco control issues, and most importantly, stimulating further collaboration toward mutual gains in protecting workers' health.

Tobacco Smoking by Occupation in Australia: Results from the 2004 to 2005 National Health Survey

OBJECTIVE

This study presents the most recent estimates of Australia's national tobacco smoking rates by occupation.

METHODS

Smoking data was extracted from the 2004 to 2005 National Health Survey, which captured approximately 26,000 persons and achieved a response rate of around 90%. Participants were limited to those of working age (18 to 64 years), with data stratified by job category and gender during the analysis.

RESULTS

The prevalence of smoking among Australian workers is estimated to be 25% (28% among males and 21% among females). Tobacco usage is considerably less common among those who are employed compared with the unemployed. By job category, smoking was most common among laborers and the least common among professionals, managers, or administrators.

CONCLUSIONS

Overall, this study suggests that Australian rates of tobacco smoking vary widely depending on occupation. Effective tobacco-control strategies targeting vulnerable sections of the workforce, particularly blue-collar workers, are clearly needed.

Methodological issues regarding confounding and exposure misclassification in epidemiological studies of occupational exposures

BACKGROUND

Confounding and exposure misclassification are issues that concern epidemiologists because of their potential to bias results of studies and complicate interpretations. In occupational epidemiology both are routinely raised to argue that an observed result is either a false positive or a false negative finding. Although it is important to consider the potential for limitations of epidemiologic investigations, judgment regarding their importance should be based on their actual likelihood of occurrence.

METHODS

This paper is based on our experience in epidemiologic analyses and a brief review of the literature regarding confounding and exposure misclassification.

RESULTS

Examples of substantial confounding are rare in occupational epidemiology. In fact, even for studies of occupational exposures and lung cancer, tobacco-adjusted relative risks rarely differ appreciably from the unadjusted estimates. This is surprising because it seems the perfect situation for confounding to occur. Yet, despite the lack of evidence that confounding is a common problem, nearly every epidemiologic paper includes a lengthy discussion on uncontrolled or residual confounding. On the other hand, exposure misclassification probably occurs in all studies. The only question is, how much? The direction and magnitude of nondifferential exposure misclassification (the type most likely to occur in cohort studies) on estimates of relative risks can be largely predicted given knowledge on the degree of misclassification, that is, relatively small amounts of misclassification can bias relative risks substantially towards the null. The literature, however, is full of discussions implying that misclassification of exposure is an explanation for a positive finding.

CONCLUSIONS

These comments are not to suggest that all potential limitations for epidemiologic studies should not be considered and evaluated. We do believe, however, that the likelihood of occurrence and the direction and magnitude of the effect should be more carefully and realistically considered when making judgments about study design or data interpretation.

Literature review of cancer mortality and incidence among dentists

This review assesses the epidemiological literature describing dentist mortality and cancer incidence risk. In the dental workplace a variety of hazards may have been historically present or currently exist which can impact dentists' long-term health, including their mortality and cancer incidence. The epidemiological literature of dentistry's health outcomes was reviewed with a focus on all cancers combined and cancers of the brain, lung, reproductive organs and skin. Relevant studies were identified using MEDLINE and NIOSHTIC through early 2006 and from references cited in the articles obtained from these databases. Dentist cancer mortality and incidence generally showed a favourable risk pattern for lung cancer and overall cancer occurrence. Nevertheless, several studies reported an increased risk for certain cancers, such as those of the skin and, to a lesser extent, the brain and female breast. These elevated risks may be related to social status or education level, or may alternatively represent the impact of hazards in the workplace. The evidence for an increased mortality or cancer incidence risk among dentists must be interpreted in light of methodological limitations of published studies. Future studies of dentists would benefit from the assessment of specific occupational exposures rather than relying on job title alone.

Smoking imputation and lung cancer in railroad workers exposed to diesel exhaust

BACKGROUND

An association between diesel exhaust exposure and lung cancer mortality in a large retrospective cohort study of US railroad workers has previously been reported. However, specific information regarding cigarette smoking was unavailable.

METHODS

Birth cohort, age, job, and cause of death specific smoking histories from a companion case-control study were used to impute smoking behavior for 39,388 railroad workers who died 1959-1996. Mortality analyses incorporated the effect of smoking on lung cancer risk.

RESULTS

The smoking adjusted relative risk of lung cancer in railroad workers exposed to diesel exhaust compared to unexposed workers was 1.22 (95% CI = 1.12-1.32), and unadjusted for smoking the relative risk was 1.35 (95% CI = 1.24-1.46).

CONCLUSIONS

These analyses illustrate the use of imputation in record-based occupational health studies to assess potential confounding due to smoking. In this cohort, small differences in smoking behavior between diesel exposed and unexposed workers did not explain the elevated lung cancer risk.

Results of a union-based smoking cessation intervention for apprentice iron workers (United States)

OBJECTIVE

Blue-collar workers are more likely to smoke, smoke more heavily, and have less success in quitting compared to white-collar workers, and this occupational gap is growing over time. Effective smoking cessation interventions among blue-collar workers are needed to address growing class-based disparities.

METHODS

We used a pre-post study design to test feasibility and effect size of a smoking cessation trial in a union apprenticeship training program for iron workers (n = 337). The 4-month intervention drew upon a health promotion-health protection model for smoking cessation among blue-collar workers. We conducted pairwise analyses to assess pre-post intervention differences in 7-day point prevalence smoking abstinence measured 1 month after intervention was completed. Additional secondary outcomes, including smoking frequency, intensity, intention and self-efficacy to quit, were also assessed.

RESULTS

Baseline smoking prevalence was 41%. We observed a 19.4% post-intervention quit rate among baseline smokers. There were statistically significant positive changes pre- and post-intervention in intention to quit smoking, self-efficacy to quit, and a reduction in the number of days smoked. Participation in pro-active intervention components was associated with a three-fold (OR = 3.0, 1.15, 7.83) increase in the likelihood of quitting. Overall, participation in intervention components was low.

CONCLUSIONS

Labor union apprenticeship programs represent a promising venue for smoking cessation interventions, particularly those that draw upon a health promotion-health protection model.

Obesity in US workers: The National Health Interview Survey, 1986 to 2002

OBJECTIVES

Obesity has emerged as one of the most important public health issues in the United States. We assessed obesity prevalence rates and their trends among major US occupational groups.

METHODS

Self-reported weight and height were collected annually on US workers, aged 18 years or older, from the 1986 to 1995 and the 1997 to 2002 National Health Interview Surveys. Overall, occupation-, race-, and gender-specific rates of obesity (defined as a body mass index>30.0 kg/m2) were calculated with data pooled from both study periods (n>600,000). Annual occupation-specific prevalence rates were also calculated, and their time trends were assessed.

RESULTS

Obesity rates increased significantly over time among employed workers, irrespective of race and gender. The average yearly change increased from 0.61% (+/-.04) during the period from 1986 to 1995 to 0.95% (+/-.11) during the period from 1997 to 2002. Average obesity prevalence rates and corresponding trends varied considerably across occupational groups; pooled obesity prevalence rates were highest in motor vehicle operators (31.7% in men; 31.0% in women).

CONCLUSIONS

Weight loss intervention programs targeting workers employed in occupational groups with high or increasing rates of obesity are urgently needed.

Longest Held Job in U.S. Occupational Groups: The National Health Interview Survey

OBJECTIVE

We sought to assess the validity of using current or most recent occupation as surrogate for longest-held job (and its exposures).

METHODS

The National Health Interview Survey (NHIS) is an annual, probability, cross-sectional U.S. population survey. The 1986 and 1988 NHIS occupational supplements provided information for more than 49,000 workers. Using Cohen's Kappa, concordance was assessed by occupational group and several subgroups.

RESULTS

Statistically significant results were observed for all occupational groups. More than 70% of 13 broad occupations had a Kappa of 50.0 or greater, with variable concordance by subpopulation. Among 206 occupational groups, there was more variability: Kappa ranged from 92.7 (dentists) to 9.2 (farm managers).

CONCLUSIONS

Moderate-to-high levels of agreement was observed in this large, representative sample of US workers. Therefore, current occupation can be used as a surrogate for longest-held job for many occupational subgroups.

Lung cancer in railroad workers exposed to diesel exhaust

Diesel exhaust has been suspected to be a lung carcinogen. The assessment of this lung cancer risk has been limited by lack of studies of exposed workers followed for many years. In this study, we assessed lung cancer mortality in 54,973 U.S. railroad workers between 1959 and 1996 (38 years). By 1959, the U.S. railroad industry had largely converted from coal-fired to diesel-powered locomotives. We obtained work histories from the U.S. Railroad Retirement Board, and ascertained mortality using Railroad Retirement Board, Social Security, and Health Care Financing Administration records. Cause of death was obtained from the National Death Index and death certificates. There were 43,593 total deaths including 4,351 lung cancer deaths. Adjusting for a healthy worker survivor effect and age, railroad workers in jobs associated with operating trains had a relative risk of lung cancer mortality of 1.40 (95% confidence interval, 1.30-1.51). Lung cancer mortality did not increase with increasing years of work in these jobs. Lung cancer mortality was elevated in jobs associated with work on trains powered by diesel locomotives. Although a contribution from exposure to coal combustion products before 1959 cannot be excluded, these results suggest that exposure to diesel exhaust contributed to lung cancer mortality in this cohort. Key words: diesel exhaust, lung cancer, occupational exposure.

Trends in US smoking rates in occupational groups: the National Health Interview Survey 1987-1994

It is unknown if reductions in U.S. adult smoking rates are uniform across occupational groups. The National Health Interview Survey (NHIS) is a multistage area probability cross-sectional survey of the U.S. civilian population. Data on occupational and smoking status were collected on 141122 adult participants from the 1987, 1988, and 1990 -1994 NHIS annual surveys. Overall smoking rates ranged from 58% in roofers to 4% in physicians, with higher rates found among blue collar professions. There were reductions in smoking from 1987-1994 within 72% of occupational groups; 19 of these downward trends were significant and occurred exclusively within white collar professions. Blue collar workers continue to smoke in large numbers, whereas white collar workers report lower rates along with corresponding significant downward trends in rates among selected occupational groups. The development of effective smoking prevention strategies targeting blue collar groups is needed.

Mortality and cancer incidence among alachlor manufacturing workers 1968-99

BACKGROUND

Alachlor is the active ingredient in pre-emergent herbicide formulations that have been used widely on corn, soybeans, and other crops. It has been found to cause nasal, stomach, and thyroid tumours in rodent feeding studies at levels that are much higher than likely human exposures.

AIMS

To evaluate mortality rates from 1968 to 1999 and cancer incidence rates from 1969 to 1999 for alachlor manufacturing workers at a plant in Muscatine, Iowa.

METHODS

Worker mortality and cancer incidence rates were compared to corresponding rates for the Iowa state general population. Analyses addressed potential intensity and duration of exposure.

RESULTS

For workers with any period of high alachlor exposure, mortality from all causes combined was lower than expected (42 observed deaths, SMR 64, 95% CI 46 to 86) and cancer mortality was slightly lower than expected (13 observed deaths, SMR 79, 95% CI 42 to 136). Cancer incidence for workers with potential high exposure was similar to that for Iowa residents, both overall (29 observed cases, SIR 123, 95% CI 82 to 177) and for workers exposed for five or more years and with at least 15 years since first exposure (eight observed cases, SIR 113, 95% CI 49 to 224). There were no cases of nasal, stomach, or thyroid cancer.

CONCLUSIONS

There were no cancers of the types found in toxicology studies and no discernible relation between cancer incidence for any site and years of alachlor exposure or time since first exposure. Despite the small size of this population, the findings are important because these workers had chronic exposure potential during extended manufacturing campaigns, while use in agriculture is typically limited to a few days or weeks each year.

Reducing occupation-based disparities related to tobacco: roles for occupational health and organized labor

BACKGROUND

Persistent and growing occupation-based disparities related to tobacco pose a serious public health challenge. Tobacco exacts a disproportionate toll on individuals employed in working class occupations, due to higher prevalence of smoking and exposure to secondhand smoke among these workers compared to others.

METHODS

We provide an overview of recent advances that may help to reduce these disparities, including research findings on a successful social contextual intervention model that integrates smoking cessation and occupational health and safety, and a new national effort to link labor unions and tobacco control organizations around their shared interest in reducing tobacco's threat to workers' health.

CONCLUSIONS

Implications of these efforts for future research and action are discussed.

Working class matters: socioeconomic disadvantage, race/ethnicity, gender, and smoking in NHIS 2000

OBJECTIVES

We sought to describe the burden of smoking on the US population, using diverse socioeconomic measures.

METHODS

We analyzed data from the 2000 National Health Interview Survey.

RESULTS

Overall, the prevalence of current smoking was greatest among persons in--and independently associated with--working class jobs, low educational level, and low income. Attempts to quit showed no socioeconomic gradient, while success in quitting was greatest among those with the most socioeconomic resources. These patterns held in most but not all race/ethnicity-gender groups. Finer resolution of smoking patterns was obtained using a relational UK occupational measure, compared to the skill-based measure commonly used in US studies.

CONCLUSIONS

Reducing social disparities in smoking requires attention to the complexities of class along with race/ethnicity and gender.

Smoking and occupation from the European Community Respiratory Health Survey

BACKGROUND

Smoking is among the most important personal and modifiable risk factors for adverse health outcomes. The workplace offers a potentially effective venue for tobacco prevention programmes; identifying occupational groups with high smoking prevalence may assist in targeting such programmes.

AIMS

To examine smoking prevalence among occupational groups in the European Union.

METHODS

The European Community Respiratory Health Survey (ECRHS), a cross sectional health survey conducted in 1992-93, was used to examine smoking prevalence by occupation among 14 565 subjects from 30 centres in 14 participating countries.

RESULTS

There was an approximately twofold range in smoking prevalence by occupation. For occupational groups with at least 50 subjects, the highest smoking prevalence was seen in metal making and treating for men (54.3%) and cleaners for women (50.7%). Increased smoking prevalence by occupation persisted after adjustment for age, country, and age at completion of education. Smoking was also increased among occupations with high exposure to mineral dust and gas or fumes.

CONCLUSIONS

Smoking rates vary significantly by occupation. Prevention efforts in the workplace should focus on occupations with high smoking prevalence and large employment bases.

Cancer mortality among European asphalt workers: an international epidemiological study. I. Results of the analysis based on job titles

BACKGROUND

Inhalation of bitumen fumes is potentially carcinogenic to humans.

METHODS

We conducted a study of 29,820 male workers exposed to bitumen in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers unexposed to bitumen, and 17,757 workers not classifiable as bitumen workers, from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality follow-up during 1953-2000. We calculated standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates. Poisson regression analyses compared mortality of bitumen workers to that of building or ground construction workers.

RESULTS

The overall mortality was below expectation in the total cohort (SMR 0.92, 95% CI 0.90-0.94) and in each group of workers. The SMR of lung cancer was higher among bitumen workers (1.17, 95% CI 1.04-1.30) than among workers in ground and building construction (SMR 1.01, 95% CI 0.89-1.15). In the internal comparison, the relative risk (RR) of lung cancer mortality among bitumen workers was 1.09 (95% CI 0.89-1.34). The results of cancer of the head and neck were similar to those of lung cancer, based on a smaller number of deaths. There was no suggestion of an association between employment in bitumen jobs and other cancers.

CONCLUSIONS

European workers employed in road paving, asphalt mixing and other jobs entailing exposure to bitumen fume might have experienced a small increase in lung cancer mortality risk, compared to workers in ground and building construction. However, exposure assessment was limited and confounding from exposure to carcinogens in other industries, tobacco smoking, and other lifestyle factors cannot be ruled out.

Cancer mortality among European asphalt workers: an international epidemiological study. II. Exposure to bitumen fume and other agents

BACKGROUND

An increased risk of lung cancers among asphalt workers has been suggested in epidemiological studies based on large scale statistical analyses.

METHODS

In a multi-country study of 29,820 male workers employed in road paving, asphalt mixing and roofing, 32,245 ground and building construction workers and 17,757 other workers from Denmark, Finland, France, Germany, Israel, the Netherlands, Norway, and Sweden, with mortality that was documented from 1953-2000. Exposures to bitumen fume, coal tar, 4-6 ring polycyclic aromatic hydrocarbons, organic vapor, diesel exhaust, asbestos, and silica dust were assessed via a job-exposure matrix. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) based on national mortality rates, as well as relative risks (RRs) based on Poisson regression models were calculated.

RESULTS

The SMR of lung cancer among workers exposed to bitumen fume (1.08, 95% CI 0.99-1.18) was comparable to that of non-exposed workers (SMR 1.05, 95% CI 0.92-1.19). In a sub-cohort of bitumen-exposed workers without exposure to coal tar, the SMR of lung cancer was 1.23 (95% CI 1.02-1.48). The analysis based on the semi-quantitative, matrix-based exposures in the whole cohort did not suggest an increased lung cancer risk following exposure to bitumen fume. However, in an analysis restricted to road pavers, based on quantitative estimate of bitumen fume exposure, a dose-response was suggested for average level of exposure, applying a 15-year lag, which was marginally reduced after adjustment for co-exposure to coal tar. The results for cancer of the head and neck were similar to those of lung cancer, although they were based on a smaller number of deaths. There was no clear suggestion of an association with bitumen fume for any other neoplasm.

CONCLUSIONS

The results of the analysis by bitumen fume exposure do not allow us to conclude on the presence or absence of a causal link between exposure to bitumen fume and risk of cancer of the lung and the head and neck.

Cancer incidence in the United Farmworkers of America (UFW), 1987-1997

BACKGROUND

The purpose of this study was to evaluate cancer incidence in the membership a largely Hispanic farmworker labor union in California, the United Farmworkers of America (UFW) and to examine cancer-site specific distributions as well as histology and stage of cancer at diagnosis in this group.

METHODS

An electronic record linkage was conducted between a membership roster of the UFW and the database of the California Cancer Registry, the population-based cancer registry in California for the years 1987-1997. Based upon the results of the linkage, morbidity odds ratios were calculated using the distribution of cancer in the California Hispanic population as the reference to determine if risk of specific cancers was higher or lower in the UFW. Time since first joining the union was evaluated, as was the proportional distribution of histologic subtypes and stage at diagnosis, again comparing the experience of the UFW membership to the California Hispanic population.

RESULTS

Several types of cancer were elevated in the UFW membership in comparison to the California Hispanic population. Morbidity odds ratios and 95% confidence limits were elevated for leukemia (O.R. = 1.59: 95% C.I. = 1.07-2.37), stomach cancer (O.R. = 1.69: 95% C.I. = 1.24-2.27), uterine cervix cancer (O.R. = 1.63: 95% C.I. = 1.11-2.44) and uterine corpus cancer (O.R. = 1.68: 95% C.I. = 1.05-2.67). Brain cancer was also elevated although not significantly so (O.R. = 1.57: 95% C.I. = 0.96-2.53).

CONCLUSIONS

Risk of leukemia, stomach, cervix and uterine cancers was elevated in California farmworkers. The histologic distribution of leukemia and brain cancers within the UFW membership did not differ from the distribution in the general California population although small numbers of cancers in the UFW hindered interpretation of these results. Members of the UFW experienced later stage of disease at diagnosis in comparison to California Hispanics for most major cancer sites but not for breast cancer.

Prevalence of cigarette smoking by occupation and industry in the United States

BACKGROUND

This study was undertaken to estimate the most recent prevalence of cigarette smoking by occupation and industry in the US, using the data from the third National Health and Nutrition Examination Survey (NHANES III), 1988-1994.

METHODS

Included in NHANES III are data on the cigarette smoking status, occupation, industry, and other demographic information of US non-institutionalized civilians obtained through household interview surveys. The study population included 20,032 adults aged 17 years and older. To estimate the prevalence of cigarette smoking across occupation and industry groups, we used the Survey Data Analysis (SUDAAN) software.

RESULTS

The prevalence of cigarette smoking was highest among material moving occupations, construction laborers, and vehicle mechanics and repairers. The lowest smoking prevalence was found among teachers. Among industry groups, the construction industry had the highest prevalence of cigarette smoking.

CONCLUSIONS

These findings provide information useful for targeting education activities focusing on adverse health effects of cigarette smoking and also for indirect adjustments in analysis of morbidity and mortality by occupation. Am. J. Ind. Med. 40:233-239, 2001. Published 2001 Wiley-Liss, Inc.

A technique to re-assess epidemiologic evidence in light of the healthy worker effect: the case of firefighting and heart disease

The healthy worker effect (HWE) is a bias that is believed to have strongly affected the validity of previous cohort mortality studies on the relationship between firefighting and heart disease. There is a strong healthy hired effect (a component of the HWE) among firefighters, owing particularly to the recruitment of nondiabetic candidates. This is shown in previous studies in which the reported standardized mortality ratios for diabetes are much less than unity, generally around 0.3 to 0.5. Because diabetes is known to increase the risk of heart disease, a deficit of diabetes among firefighters is expected to lead to a deficit of heart injury and disease. This would make the cohort mortality studies incapable of detecting any increase in risk of heart injury and disease among firefighters. There is also a strong healthy worker survivor effect (another component of the HWE) among firefighters. In addition, heart disease is a classic example of the HWE because heart disease is chronic and its risk factors can be identified in the selection process. It is believed that (1) a major problem of previous studies on firefighting and heart disease is their failure to recognize the importance of the HWE when interpreting their results, and (2) a technique to re-assess results in light of the HWE is urgently needed. This article addresses the generally accepted principles relating to the HWE, including its definition and sources, and proposes a technique for re-assessing the literature in light of the HWE. The technique was applied to carefully re-assess 23 studies that provided direct evidence for the relationship between firefighting and heart disease. Before the re-assessment, 7 of the 23 studies showed positive evidence and 16 showed no evidence. After the re-assessment, 11 studies showed positive evidence and 12 showed no evidence. Based on the results of the re-assessment of the 23 studies, we concluded that (1) there is strong evidence of an increased risk of death overall from heart disease among firefighters; (2) there is insufficient evidence, even after considering the HWE, that there is an increased risk of death from aortic aneurysm among firefighters; and (3) there is insufficient evidence, even after considering the HWE, for a relationship between firefighting and any heart disease subtype, such as acute myocardial infarction.

Diesel exhaust exposure and lung cancer: adjustment for the effect of smoking in a retrospective cohort study

BACKGROUND

The extent that cigarette smoking may confound the relationship between diesel exhaust exposure and lung cancer was assessed in a retrospective cohort study of 55,395 U.S. railroad workers followed from 1959 to 1976.

METHODS

The relative risk (RR) of lung cancer due to diesel exhaust was indirectly adjusted using job-specific smoking data from a case-control study of railroad workers who died between 1981-1982 and from a survey of 514 living workers from an active railroad in 1982. Adjustment factors were developed based on the distribution of job-specific smoking rates.

RESULTS

The unadjusted RR for lung cancer was 1.58 (95% CI = 1.14-2. 20) for workers aged 40-44 in 1959, who experienced the longest possible duration of exposure, and the smoking adjusted RR was 1.44 (1.01-2.05).

CONCLUSIONS

After considering differences in smoking rates between workers exposed and unexposed to diesel exhaust in a relatively large blue-collar cohort, there were still elevated risks of lung cancer in workers in jobs with diesel exhaust exposure.

Occupational bladder cancer mortality among racial and ethnic minorities in 21 states

BACKGROUND

Occupational bladder cancer mortality among minority racial/ethnic groups is not well described compared to occupational bladder cancer mortality among non-minority males in the United States.

METHODS

Race/ethnicity- and sex-specific bladder cancer mortality (1985-1992) of workers employed in 21 states was examined using a proportionate mortality study design. Mortality of specific racial/ethnic/occupational groups was compared separately with workers in the specific occupation and with members of the specific racial/ethnic group.

RESULTS

This study identified elevated bladder cancer mortality among African American males and females and Latino males in several occupational groups with exposure to suspected bladder carcinogens as well as among Asian males in sales (PMR = 2. 13) and Asian females in the personal services industry (PMR = 5.25; CI: 1.64-16.75).

CONCLUSIONS

Surveillance of occupational cancer risks among racial/ethnic minorities using regularly available death certificate data is facilitated when states code both usual occupation/industry and race/ethnicity.

Exposure to environmental tobacco smoke and the risk of lung cancer: a meta-analysis

A meta-analysis was carried out to calculate a pooled estimate of relative risk of lung cancer following exposure to environmental tobacco smoke (ETS) and to determine whether there was any heterogeneity in the pooled estimates according to selected characteristics of the studies. A total of 35 case-control and five cohort studies providing quantitative estimates of the association between lung cancer and exposure to ETS published between January 1981 and March 1999 were identified. Using fixed- and random-effects models, we calculated pooled estimates of relative risk for exposure to ETS from subjects' parents (during childhood), spouses, and coworkers. As well, we investigated whether the pooled estimates of relative risk varied by study location, degree of control of potential confounding variables, proportion of cases confirmed histologically, proportion of surrogate respondents, nonresponse rates, and year of publication. The relative risk of lung cancer among non smoking women ever exposed to ETS from their husbands' smoking was 1.20 (95% confidence interval (CI): 1.12-1.29). The pooled relative risk was 1.19 (95% CI: 1.10-1.29) for case-control studies and 1.29 (95% CI: 1.04-1.62) for cohort studies. In various subgroup and meta-regression analyses, we found no statistically significant differences by selected characteristics of the studies. In addition, we found that the risk of lung cancer increased consistently with increasing levels of exposure. The 11 studies reporting relative risks among male non smokers yielded a pooled relative risk of 1.48 (95% CI: 1.13-1.92) for ever exposed to ETS, and the relative risk of lung cancer for ever being exposed to ETS at work was a 1.16 (95% CI: 1.05-1.28). These results are consistent with the hypothesis that exposure to ETS increases the risk of lung cancer. While there may be alternative explanations to the data, it is more likely that the observed association is not an artifact and that ETS causes lung cancer in non smokers.

Mortality patterns among electrical workers employed in the U.S. construction industry, 1982-1987

BACKGROUND

Studies of electrical workers in the utility and manufacturing industries have reported excess site-specific cancer. No previous studies of electrical workers in the construction industry have been conducted.

METHODS

Our study evaluated the mortality patterns of 31,068 U.S. members of the International Brotherhood of Electrical Workers who primarily worked in the construction industry and died 1982-1987.

RESULTS

Comparison to the U.S. population by using the NIOSH life table showed significantly elevated proportionate mortality for many causes. Excess mortality for leukemia (proportionate mortality ratio (PMR)=115) and brain tumors (PMR=136) is similar to reports of electrical workers with occupational exposure to electric and magnetic fields in the electric utility or manufacturing industry. Excess deaths due to melanoma skin cancer (PMR=123) are consistent with findings of other PCB-exposed workers. A significantly elevated PMR was observed for the diseases caused by asbestos: lung cancer (PMR=117), asbestosis (PMR=247), and malignant mesothelioma (PMR=356) and from fatal injuries, particularly electrocutions (PMR=1180). The findings of statistically significant excess deaths for prostate cancer (PMR=107), musculoskeletal disease (PMR=130), suicide (PMR=113), and disorders of the blood-forming organs (PMR=141) were unexpected.

CONCLUSIONS

Results suggest that more detailed investigations of occupational risk factors and evaluation of preventive practices are needed to prevent excess mortality in this hazardous occupation. Am. J. Ind. Med. 36:630-637, 1999. Published 1999 Wiley-Liss, Inc.

Occupational cancer among women: research status and methodologic considerations

Occupational causes of cancer have not been well-evaluated among women. An increase in the number of women in the work force in jobs with potentially hazardous exposures during the past few decades raises the question as to whether there is a need to enhance our efforts in this area. The inability to evaluate occupational causes of female gynecologic tumors in studies of men, plus the potential for variation in outcome responses between men and women because of gender-based exposure and susceptibility differences, underscore the need for investigations specifically focused on women. Investigations of occupational exposures and cancer risk among women may require design considerations that differ somewhat from studies of men. Issues to consider include the impact of studying outcomes with high survival (e.g., breast cancer), gender-specific exposure patterns and toxicokinetic processing of some chemicals, special limitations in the use of the general population as the referent, and the need to control for established risk factors for gynecologic tumors.

Cancer mortality in women with probable exposure to silica: a death certificate study in 24 states of the U.S

BACKGROUND

Silica exposure is known to cause an increased risk of pneumoconiosis and some types of cancers. Exposure to silica is becoming an increasingly common occupational hazard for women. Studies contradict each other on whether or not women suffer more occupational pneumoconiosis than men, but no studies have evaluated cancer risks among women exposed to silica.

METHODS

Death certificate data on occupation and industry from 24 states in the U.S. between 1984 and 1993 were used to calculate proportional mortality ratios (PMRs) for workers exposed to silica.

RESULTS

Over 20,000 deaths (4% of all deaths in persons with possible work-related silica-exposure) occurred among women. The PMR for pneumoconiosis among women working in occupations or industries with possible silica exposure was 13.6 (95% CI: 7.2-23.2), for men 3.8 (CI: 3.7-4.0). Both men and women had higher than expected PMRs for respiratory diseases, lung and esophageal cancers, and external causes of death. In the group with probable silica exposure (both occupation and industry associated with silica), women had elevated PMRs for thyroid cancer (PMR = 5.5), multiple myeloma (PMR = 1.3), digestive organ cancers (PMR = 1.2), whereas men had no increased PMRs for these cancers. Both genders had significantly decreased PMRs for breast cancer, cerebrovascular diseases, nervous system diseases, and brain and other central nervous system cancers.

CONCLUSIONS

An in depth look at the types of silica exposures (specific work duties) and adjustment for confounders is warranted to determine the importance of these gender-specific excess mortalities associated with possible silica exposure.

Smoking as a confounder in case-control studies of occupational bladder cancer in women

BACKGROUND

In studies in men, risk estimates on occupation and bladder cancer are distorted by about 10% when not adjusting for smoking. We examined the degree to which occupational risk estimates for bladder cancer in women are confounded by smoking, and the degree of residual confounding by inadequate control of this effect.

METHODS

Primary data of 11 case-control studies on occupation and bladder cancer from Denmark, France, Germany, Greece, Italy, and Spain were pooled. Information for smoking and lifetime occupational history for 700 female cases and 2,425 female controls ages 30-79 was abstracted and recoded. Logistic regression was used to calculate odds ratios (OR) by occupation, applying five models which differed in their degree of adjustment for smoking.

RESULTS

In major occupational groups, risk estimates were distorted by less than 10% when not adjusting for smoking. A statistically significant excess risk for bladder cancer was found in 13 specific occupations and industries. In most occupations, adjustment for smoking led the ORs towards the null value, but all statistically significant associations were maintained after adjustment. In three occupations (lathe operators, field crop workers, and wood manufacturers), a statistically significant excess risk was masked when not adjusting for smoking. In six occupations, estimates were distorted by more than 10% (-22% up to +40%). In occupations where smoking acted as a positive confounder, the proportion of confounding removed using a dichotomous smoking variable (ever/never) was around 60%. In one occupation (buyers), controlling for smoking status (ever, never) led to over-adjustment, because the percentage of smokers was high but the quantity smoked was low.

Cohort mortality study of 57,000 painters and other union members: a 15 year update

OBJECTIVES

To study mortality patterns in the largest existing cohort of painters.

METHODS

15 years of follow up were added to a study of 42,170 painters and 14,316 non-painters based on union records. There were 23,458 deaths, compared with 5313 in the earlier follow up.

RESULTS

Comparisons with the United States population showed significantly increased rates in painters for lung cancer (standardised mortality ratio (SMR) 1.23, 95% confidence interval (95% CI) 1.17 to 1.29), bladder cancer (SMR 1.23, 95% CI 1.05 to 1.43), liver cancer (SMR 1.25, 95% CI 1.03 to 1.50), and stomach cancer (SMR 1.39, 95% CI 1.20 to 1.59). However, in direct comparisons with non-painters only the excesses for lung cancer (SRR 1.23, 95% CI 1.11 to 1.35, increasing to 1.32, 95% CI 16 to 1.93 with 20 years latency) and bladder cancer (SRR 1.77, 95% CI 1.13 to 2.77) were confirmed. Some confounding by smoking may affect these two outcomes, particularly with external referents. Cirrhosis of the liver was increased for both painters and non-painters (SMRs 1.21, 95% CI 1.07 to 1.35, and 1.26, 95% CI 1.03 to 1.51, respectively), possibly indicating high alcohol consumption. Suicide (SMR 1.21, 95% CI 1.05 to 1.38) and homicide (SMR 1.36, 95% CI 1.04 to 1.75) were increased for painters but not for non-painters; neuropsychiatric diseases have been associated with painters in earlier studies.

CONCLUSIONS

The results suggest modest occupational risks for lung and bladder cancer; these results are consistent with existing publications. The International Agency for Research on Cancer has classified painting as an occupation definitely associated with cancer.

Cancer among farmers: a meta-analysis

PURPOSE

We conducted a meta-analysis of 37 studies to assess whether farmers had elevated rates for several cancers, as was concluded in a previous meta-analysis of 21 studies.

METHODS

We identified studies from the reference list of the previous meta-analysis and from a MEDLINE search through December 31, 1994. The primary purpose of our analysis was to identify and, if possible, understand the sources of heterogeneity in the literature. Stratified analyses of studies and linear modeling with inverse variance weights were used to assess the impact of study characteristics on results. We calculated summary relative risks as a weighted average of the log relative risks across studies using inverse variance weights. Fixed and random effects models were used as appropriate.

RESULTS

The results for most cancers were markedly heterogeneous by study design and, for fewer cancers, by geographic location, and whether the studies focused on crop and livestock farmers. There was some indication of publication bias due to underreporting of near null or sub null findings. Lip cancer was the only cancer that was clearly elevated among farmers.

CONCLUSIONS

The results do not suggest that farmers have elevated rates of several cancers. However, the known heterogeneity of exposures by type of farming, geographic area, time period, and other factors limits the informativeness of meta-analyses of these studies for assessing potential carcinogenic exposures in agriculture.

An alternative explanation for the apparent elevated relative mortality and morbidity risks associated with exposure to environmental tobacco smoke

Insofar as industrial and other blue collar workers are more likely to bring home toxic materials on their person, and also are more likely to smoke than those in other occupations, members of a household are more likely to be subject to paraoccupational exposure and belong to lower socioeconomic strata if the household contains a smoker than if the household does not contain a smoker. Thus observed differences in risk of mortality or morbidity ascribed to ETS on the basis of a comparison of households with and without smokers may be partly or entirely due to differences in paraoccupational exposure and socioeconomic strata. Similarly, differences in mortality and morbidity ascribed to paraoccupational exposure may be partly or entirely due to differences in ETS exposure that are also related to social class and to types of occupation. Unfortunately, there are no data now in existence that could help determine separately the effects of these major confounded variables. There exists, then, a situation in which two explanations are advanced for respiratory diseases among members of a household, each based on similar study populations but focused on different major risk variables: ETS on the one hand, socioeconomic status and paraoccupational exposure on the other. Properly focused investigations need to be initiated.

[Confounding of occupational cancer risk in epidemiological studies due to ignorance of smoking data as exemplified by bladder and lung cancer in painters]

Studies on occupational risk factors for cancer are frequently carried out without information on smoking habits. However, the proportion of smokers may vary considerably across occupational groups. Thus it is unclear, whether an observed increased cancer risk in an occupational group is at least partly the result of a higher proportion of smokers in that group. The paper demonstrates the possible extent of such confounding by using hypothetical and empirical examples of studies concerning the lung cancer and bladder cancer risk in painters. A formula for the indirect control of such confounding is applied. Relative risks greater than 1.2 for bladder cancer and 1.3 for lung cancer should thus not be considered solely the result of confounding. The degree of confounding is less than generally assumed. However, the evaluation of this degree remains questionable in case of an interaction between smoking and occupational exposure.