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Results for “Healthy Worker Effect”

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PubMed1997

[Mortality among workers in the pulp-paper industry. A successive follow up of the cohort].

After five successive years of observation the authors present a verified evaluation of the delayed health effects in the pulp and paper industry workers (with particular regard to mortality from malignant neoplasms). The cohort studied consisted of 10,460 workers employed for at least 12 months between 1967 and 1990 in the plants manufacturing sulfate pulp, paper, board and paper products. Subjects were assigned to three subcohorts according to the work areas: 1. pulp mill workers; 2. paper mill workers (paper and board as well as their products); 3. other workers. The workers were enrolled in the subcohort if they were employed for at least one year in one of these departments. One subject could be included in more than one subcohort. The vital status of the cohort was determined through a variety of sources over an observation period of 28 yrs (1967-95). Mortality data were analysed in terms of cause-specific standardized mortality ratios (SMRs) with expected deaths count based on the national mortality rates in Poland. The results of a twenty three-year cohort observation, published earlier, showed the lowered overall mortality (explained by a "healthy worker effect") and the excess of deaths from malignant neoplasms for some sites (peritoneum, prostate, brain). Due to a small number of deaths recorded, kind of exposure and its duration, were left out of the analysis. The results presented in this paper, obtained after five successive years of the male cohort observation, showed an excess of deaths from cancers of the respiratory tract and peritoneum. In the female cohort an excess of brain cancers was found. Only an excessive mortality from malignant neoplasms of the respiratory system was coherent with the exposure to higher concentrations of wood, paper and board dust. An excess mortality from diseases of the circulatory system was found in both males and females employed in paper production.

Adult↗

PubMed1996

Comparison of dust related respiratory effects in Dutch and Canadian grain handling industries: a pooled analysis.

OBJECTIVES: Four previously conducted epidemiological studies in more than 1200 grain workers were used to compare exposure-response relations between exposure to grain dust and respiratory health. METHODS: The studies included Dutch workers from an animal feed mill and a transfer grain elevator and Canadian workers from a terminal grain elevator and the docks. Relations between forced expiratory volume in one second (FEV1) and exposure were analysed with multiple regression analysis corrected for smoking, age, and height. Exposure variables examined included cumulative and current dust exposure and the numbers of years a subject was employed in the industry. Sampling efficiencies of the Dutch and Canadian measurement techniques were compared in a pilot study. Results of this study were used to correct slopes of exposure-response relations for differences in dust fractions sampled by Dutch and Canadian personal dust samplers. RESULTS: Negative exposure-response relations were shown for regressions of FEV1 on cumulative and current exposure and years employed. Slopes of the exposure-response relations differed by a factor of three to five between industries, apart from results for cumulative exposure. Here the variation in slopes differed by a factor of 100, from -1 to -0.009 ml/mg.y/m3. The variation in slopes between industries reduced to between twofold to fivefold when the Dutch transfer elevator workers were not considered. There was evidence that the small exposure-response slope found for this group is caused by misclassification of exposure and a strong healthy worker effect. Alternative, but less likely explanations for the variation in slopes were differences in exposure concentrations, composition of grain dust, exposure characteristics, and measurement techniques. CONCLUSION: In conclusion, this study showed moderately similar negative exposure-response relations for four different populations from different countries, despite differences in methods of exposure assessment and exposure estimation.

Adult↗

PubMed1997

A mortality study of employees of the nuclear industry in Oak Ridge, Tennessee.

An analysis was conducted of 27,982 deaths among 106,020 persons employed at four Federal nuclear plants in Oak Ridge, Tennessee, between 1943 and 1985. The main objectives were to extend the evaluation of the health effects of employment in the nuclear industry in Oak Ridge to include most workers who were omitted from earlier studies, to compare the mortality experience of workers among the facilities, to address methodological problems that occur when individuals employed at more than one facility are included in the analysis, and to conduct dose-response analyses for those individuals with potential exposure to external radiation. All-cause mortality and all-cancer mortality were in close agreement with national rates. The only notable excesses occurred for white males for lung cancer [standardized mortality ratio (SMR) = 1.18, 1,849 deaths] and non-malignant respiratory disease (SMR = 1.12, 1,568 deaths). A more detailed analysis revealed substantial differences in death rates among workers at the Oak Ridge plants. Evaluation of internally adjusted log SMRs using Poisson regression showed that workers employed only at Tennessee Eastman Corporation or K-25 and at multiple facilities had higher death rates than similar workers employed only at X-10 or Y-12, and that the differences were primarily due to non-cancer causes. Analysis of selected cancer causes for white males indicated large differences among the workers at the different facilities for lung cancer, leukemia and other lymphatic cancer. Dose-response analyses for external penetrating radiation were limited to a subcohort of 28,347 white males employed at X-10 or Y-12. Their collective recorded dose equivalent was 376 Sv. There was a strong "healthy worker effect" in this subcohort-all-cause SMR = 0.80 (4,786 deaths) and all-cancer SMR = 0.87 (1,134 deaths). Variables included in the analyses were age, birth cohort, a measure of socioeconomic status, length of employment, internal radiation exposure potential and facility. For external radiation dose with a 10-year lag, the excess relative risk was 0.31 per Sv (95% CI = -0.16, 1.01) for all causes and 1.45 per Sv (95% CI = 0.15, 3.48) for all cancer. The estimated excess relative risk for leukemia was negative but imprecisely determined. A preliminary dose adjustment procedure was developed to compensate for missing dose but not other dosimetry errors. Results of the analyses using the adjusted doses suggest that the effect of missing dose is an upward bias in dose-response coefficients and test statistics.

Dose-Response Relationship, Radiation↗

PubMed1995

Chronic and acute respiratory effects among grain mill workers.

Exposure to flour dust may induce chronic respiratory manifestations as well as acute ventilatory effects. We compared the prevalence of respiratory symptoms, ventilatory impairment, and variations in pulmonary function over the workshift in a group of mill workers exposed to wheat flour and in referent workers. One hundred and forty-two men exposed to flour in a mill and 37 referent workers were included in this study. Each subject completed a standardized questionnaire. Pulmonary function tests were performed before and after the workshift. The assessment of environmental exposure to flour showed high concentrations during some jobs with a high percentage of inhalable particles and a low concentration of respirable particles. The exposed workers had a significantly higher prevalence of usual cough and usual phlegm than the referents. The prevalence of asthma, based on the questionnaire, was similar. Before the workshift, the exposed workers had significantly lower mean lung function values for peak flow rate and forced expiratory flow rate at 75% of the vital capacity than the referents. After the workshift, all the lung function values showed a slight decrease, significant for forced vital capacity and forced expiratory volume during 1 s in both groups. Among the exposed workers, the asthmatic subjects had a significantly higher decrease across the shift than the nonasthmatic workers. This result is probably linked to bronchial hyperreactivity. Among nonasthmatic subjects, the decrease was larger in nonexposed workers than in exposed workers. A higher prevalence of respiratory symptoms and lower pulmonary function values were observed among mill workers by comparison with referents. Moreover, the data suggest that asthmatic status and the time of spirometric measurements need to be taken into account in epidemiological studies on exposure to airborne allergens. In addition, the study does not exclude a healthy worker effect with selection of dust-resistant subjects or better identification of asthmatic subjects among the workers exposed to an allergenic substance than among the nonexposed workers.

Adult↗

PubMed1996

Endotoxin exposure-response in a fiberglass manufacturing facility.

Peak expiratory flow (PEF) and workplace exposure to endotoxin, phenolic resin, and formaldehyde were measured to investigate asthma symptoms and medication use among employees in a fiberglass wool manufacturing plant. Self-recorded PEF was obtained from 37 workers, for a total of 181 days off work and 187 days at work with concurrent personal exposure monitoring. Pre- and post-shift spirometry were obtained on at least 2 days. The 8 hr time-weighted average personal exposure ranges were endotoxin; 0.4-759 ng/m3; phenolic resin, 5.7-327 micrograms/m3; and formaldehyde, 1.2-265 micrograms/m3. Amplitude percent mean peak flow was associated with years since starting regular work in the highest endotoxin exposure area, although current assignment in that area was associated with reduced amplitude--evidence for a healthy worker effect. Exposure-response was analyzed by regression of lung function change on exposure using generalized estimating equations with robust variance estimates. Endotoxin exposure above 4 ng/m3 (8 hr time-weighted average) was associated with a decline in lung function across the work shift, and with drops in lung function 16-20 hr after exposure. Phenolic resin exposure was not consistently associated with decrements, and formaldehyde was not associated with decrements in lung function.

Adult↗

PubMed1996

Reduced lung cancer mortality in dairy farmers: is endotoxin exposure the key factor?

From two areas in the Province of Padova, we selected 2,283 male farmers who worked either in cattle raising or in crop/orchard cultivation. There were 422 cohort deaths from 1970 to 1992. Using the regional population as a reference, the standardized mortality ratio (SMR) was calculated, with 95% confidence intervals (CI) based on the Poisson distribution. Cancer mortality was significantly reduced among the 1,561 dairy farmers (SMR = 0.65; CI = 0.53-0.81); there was a significant decrease in lung cancer (SMR = 0.49; CI = 0.31-0.74), whereas a significant increase from brain tumors was found (SMR = 2.83; CI = 1.04-6.17). Neither overall cancer mortality nor the lung cancer SMR deviated significantly from unity for the 722 crop/orchard farmers. Among dairy farmers, moreover, lung cancer SMRs showed a significant downward trend across the quartiles of increasing length of work, 0.96 in the first quartile, and 0.48, 0.40, and 0.25 in the second, third, and fourth quartiles, respectively. Moreover, lung cancer risk decreased with increasing farm land area, with SMRs in the quartiles of 0.89, 0.37, 0.41 and 0.19. This decrease cannot be attributed to either a selection (healthy worker effect) or a confounding (lower percentage of smokers) bias. Nor was it due to an artifact introduced by differences in age distribution among the quartiles. Dairy farmers are known to be exposed to higher airborne endotoxin concentrations; reasonably, this cumulative exposure increases further with years of work and area of farm. Endotoxins may have protected the dairy farmers against lung cancer through the tumor necrosis factor produced by alveolar macrophages.

Adolescent↗

PubMed1999

Asthma and allergy in New Zealand farmers.

AIMS: To examine the prevalence of symptoms of asthma and allergy in different farming groups in New Zealand. METHODS: A postal questionnaire was sent to a random sample of 2,500 farmers throughout New Zealand. RESULTS: The response rate was 77% (1,706 of 2,203 eligibles). The 12-month period prevalence of current asthma was 11.8% overall, compared with 15% in the general population. Asthma prevalence was higher for horse breeders/groomers (16.5%), pig farmers (18.2%), poultry farmers (17.4%), and those working with oats (17.4%). Asthma was also significantly elevated among those working with cleaning powders (14.7%). Women were more likely to report current asthma than were men (OR 1.8, 95% CI 1.3-2.5). Hay fever was significantly higher in deer and crop farmers, and farmers working with horses and goats; eczema was higher for goat and deer farmers. CONCLUSIONS: The lower overall prevalence of asthma in farmers may be due to the healthy worker effect. Among farmers, the types of farming associated with an elevated prevalence of asthma and allergy in New Zealand are deer and goat farming, working with horses, poultry, pigs, and crop farming. Females reported more current asthma than males.

Adolescent↗

PubMed2000

Mesothelioma and lung tumors attributable to asbestos among petroleum workers.

BACKGROUND: Asbestos exposure has been definitively found to be associated with both mesothelioma and lung cancer. Nevertheless, in the overall population of oil refinery workers potentially exposed to asbestos, many studies clearly show a definitely increased risk of mesothelioma, but no proven excess of lung cancer after comparison to the general population. Through the presentation of new data and the re-appraisal of two recent and independent epidemiological studies conducted in Liguria, Italy, and Ontario, Canada, we attempt to shed light on this apparently paradoxical finding. METHODS: Lung cancer mortality was studied among maintenance workers exposed to asbestos, and among two other subgroups of refinery employees: blue collar and white collar workers. The comparison with blue collar workers was performed in order to take into account the role of healthy worker effect, smoking habit, and the socioeconomic level. The comparison with white collar workers was performed to control for other occupational lung carcinogens. RESULTS AND CONCLUSIONS: Results reveal a consistency between the two studies and show that 96-100% of the mesotheliomas and 42-49% of the lung tumors arising among maintenance workers were attributable to asbestos exposure. Our new analysis, estimating two cases of asbestos-related lung cancer for each case of mesothelioma, confirms published findings on the magnitude of asbestos-related tumors in oil refineries.

Asbestos↗

PubMed2002

An alternate characterization of hazard in occupational epidemiology: years of life lost per years worked.

BACKGROUND: Standardized mortality ratios (SMRs) and other measures of relative risk by themselves may not suffice as descriptors of occupational hazards for many audiences including decision-makers and those at direct risk from hazardous work. To explore other approaches, we calculated excess years of potential life lost and excess lifetime risk for both lung diseases and fatal injuries in a cohort of uranium miners with historical records of exposure to radon gas. METHODS: We used relatively simple life table (SMR) methods and also analyzed lung cancer mortality with Poisson regression methods permitting control for smoking. RESULTS: Among uranium miners hired after 1950, whose all-cause SMR was 1.5, 28 percent would experience premature death from lung diseases or injury in a lifetime of uranium mining. On average, each miner lost 1.5 yr of potential life due to mining-related lung cancer, or almost 3 months of life for each year employed in uranium mining. As a consequence of all excess lung disease and injury risks combined, a year of mining was associated with 5.9 months loss of potential life. For each year actually working underground, miners lost more than 8 months of potential life. When controlled for smoking (and healthy worker effect) with Poisson regression, the estimates for radon-related lung cancer effects were slightly larger. Although chronic disease deaths dominated in excess years of life lost (due to radon, silica and possibly other exposures), more years were lost on average per individual injury death (38 yr), than per excess lung cancer (20 yr) or other lung disease death (18 yr). Fatal-injury dominated the potential years of life lost up to about age 40. CONCLUSIONS: Years of life lost per years employed provides another, more intuitive summary of occupational mortality risk.

Accidents, Occupational↗

PubMed2004

Cancer mortality among French Atomic Energy Commission workers.

BACKGROUND: All causes and cancer mortality of 58,320 workers employed at the Commissariat à l'Energie Atomique (CEA) between 1946 and 1994 were compared with that of the general population in a retrospective cohort study. METHODS: Standardized Mortality Ratios (SMR) were computed with reference to the French national population. RESULTS: Between 1968 and 1994, 4,809 deaths occurred. A healthy worker effect is observed for men (SMR = 0.57, CI(90%) = [0.56;0.59]) and for women (SMR = 0.72, CI(90%) = [0.67;0.77]). Nine sites of cancer death were found to be in statistically significant deficit among men, none among women. An excess of pleural cancers is observed among men (SMR = 1.79, CI(90%) = [1.27;2.45]) and of malignant melanoma (SMR = 1.50, CI(90%) = [1.04;2.11]). An excess of breast cancer is observed among women on the borderline of significance (SMR = 1.14, CI(90%) = [0.94;1.37]). CONCLUSIONS: Excesses observed will have to be related to occupational exposures in the on-going cohort study on French nuclear workers which includes a retrospective exposures assessment.

Adult↗

PubMed2005

Outcomes in work-related injuries: a comparison of older and younger workers.

BACKGROUND: The "graying of the workforce" has generated concerns about the physical capacity of older workers to maintain their health and productivity on the job, especially after an injury occurs. There is little detailed research on age-related differences in work outcomes after an occupational injury. METHODS: A self-report survey about occupational, health, and financial outcomes, and related factors was administered 2-8 weeks post-injury to workers aged < 55 and > or = 55 who had lost time due to a work injury. RESULTS: Despite more severe injuries in older workers, most outcomes were similar in both age groups. In multivariate models, age was unrelated or inversely related to poor outcomes. Injury severity, physical functioning, and problems upon return to work were associated with adverse work injury outcomes. CONCLUSIONS: Older workers appear to fare better than younger workers after a work injury; their relative advantage may be primarily due to longer workplace attachment and the healthy worker effect.

Absenteeism↗

PubMed2006

Airway disease in highway and tunnel construction workers exposed to silica.

BACKGROUND: Construction workers employed in a unique type of tunnel construction known as tunnel jacking were exposed over an 18-month period to respirable crystalline silica at concentrations that exceeded the OSHA permissible exposure limit. The present study examines workplace exposures and occurrence of airway disease in these workers. METHODS: Medical and occupational histories and chest radiographs were obtained on 343 active construction workers who had worked on the site during the period in question. Chest radiographs were interpreted according to the ILO-1980 system of classification. Standardized questions were used to develop an algorithm to define symptoms consistent with asthma (SCA) and to determine these respiratory outcomes: chronic bronchitis, shortness of breath (SOB), and physician-diagnosed asthma (current vs. not current). Relationships with each of three work activities were examined: slurry wall breakthrough (SWB), chipping caisson overpour, and tunneling/mining. RESULTS: Participants included laborers, carpenters, tunnel workers, ironworkers, operating engineers, and electricians. No cases of silicosis were found on chest X-ray. Overall prevalence of chronic bronchitis, SCA, SOB, and physician-diagnosed asthma was 10.7%, 25%, 29%, and 6.6%, respectively. Odds ratios (OR) for carpenters compared to laborers were significantly elevated for chronic bronchitis, SCA, and SOB. SWB was associated with chronic bronchitis and SCA (OR 4.93, 95% CI = 1.01, 24.17; OR 3.32, 95% CI = 1.25, 8.84, respectively). The interaction between SWB, SCA, and trade was significant for carpenters (OR 6.87, 95% CI = 1.66, 28.39). Inverse trends were observed for months on the site and chronic bronchitis, SCA, and SOB (P = 0.0374, 0.0006, and 0.0307, respectively). CONCLUSIONS: Tunnel construction workers exposed to respirable crystalline silica and cement dust are at increased risk for airway disease. Extent of risk varies by trade and work activity. Our data indicate the importance of bystander exposures and suggest that tunnel jacking may be associated with greater risk compared to more traditional methods of tunnel construction. A healthy worker effect is suggested.

Adult↗

PubMed1986

Mortality of a municipal worker cohort: II. Females.

Women have become an increasingly important segment of the total work force, yet there are very few published occupational mortality studies of female workers. This paper reports the findings of a retrospective cohort mortality study of 1,371 full-time female municipal employees of the City of Buffalo, New York, who were employed at least 1 day between January 1, 1950, and October 1, 1979, and who worked a minimum of 5 years. Vital status was ascertained for 88% of the female cohort, resulting in the identification of 214 observed deaths. This predominantly white-collar, service-oriented female cohort demonstrated significantly lower mortality than that expected based on U.S. mortality rates for white females. This strong "healthy-worker effect" was consistent across the time period of the study, across cause-specific mortality especially for all malignant neoplasms and all diseases of the circulatory system, and across different workers groups. Findings are discussed in light of the methodological issues involved in occupational studies of female workers.

Adult↗

PubMed1987

Historic cohort study in Montreal's fur industry.

A historic cohort mortality study was carried out among two groups of male workers in the Montreal fur industry: 263 dressers and dyers and 599 fur garment manufacturers. The first group is exposed to a very wide variety of chemicals used in tanning, cleaning, and dyeing fur, including substances considered to be carcinogenic and/or mutagenic. The second group is exposed to residue from the dressing and dyeing stage and to respirable fur dust. The cohorts consisted of all active members of two unions as of January 1, 1966. The mean age of the workers was 43.2 and the mean number of years since first employment 14.1. The follow-up period was from January 1, 1966, to December 31, 1981; 95% of the workers were successfully traced. Observed deaths were compared with those expected based on mortality rates of the population of metropolitan Montreal. Standardized mortality ratios (SMRs) for the manufacturers were significantly low, probably because of the ethnic composition of the cohort and a healthy worker effect. SMRs for the dressers and dyers were also low, but not as low as for the manufacturers. When attention was restricted to the French Canadians in the cohort, the observed deaths were close to the expected; there was a noteworthy excess of colorectal cancer (four observed, 0.8 expected) for dressers and dyers. Apart from this weak suggestive evidence, the results did not indicate any excess mortality risks in the fur industry. However, because of the relatively small number of expected and observed deaths in the cohort and especially among the heavily exposed dressers and dyers, the confidence intervals around SMR estimates were wide and excess risks cannot be ruled out.

Adult↗

PubMed1987

Mortality among female employees of a chemical company.

There have been few mortality studies conducted on working women despite their increasing presence in the work environment. This paper presents the findings of a cohort mortality study of 10,839 female employees with three or more days of service between 1940 and 1982 at the Midland or Bay City, Michigan, locations of the Dow Chemical Company. The cohort included substantial numbers of production and research personnel but was primarily comprised of clerical and office workers. Vital status was ascertained through 1982 for 89.4 percent of the cohort members, and death certificates were obtained for 94.0 percent of the 467 decedents. Comparisons of observed mortality with expected levels based on mortality rates for the U.S., Michigan, and a local 7-county area revealed consistently lower mortality in the cohort from the major causes of death, indicating a strong "healthy worker effect." Mortality from cancer of the cervix was significantly below expected levels, especially among women who were hired before 25 years of age. This observation, when combined with a nonsignificant excess of breast cancer, suggests a different distribution of maritally and sexually related risk factors between working and general populations of women. This and other findings are discussed relative to methodologic problems likely to accompany studies of working women.

Adult↗

PubMed1988

Mortality among workers at a nuclear fuels production facility.

A retrospective cohort mortality study was conducted in a population of workers employed at a facility with the primary task of production of nuclear fuels and other materials. Data for hourly and salaried employees were analyzed separately by time period of first employment and length of employment. The hourly (N = 6,687 with 728 deaths) and salaried (N = 2,745 with 294 deaths) employees had a mortality experience comparable to that of the United States and, in fact, exhibited significant fewer deaths in many categories of diseases that are traditionally associated with the healthy worker effect. Specifically, fewer deaths were noted in the categories of all causes, all cancers, cancer of the digestive organs, lung cancer, brain cancer (hourly workers only), diabetes, all diseases of the circulatory system, all respiratory diseases, all digestive system diseases, all diseases of the genitourinary system (hourly only), and all external causes of death. A statistically significant, and as yet unexplained increase in leukemia mortality (6 observed vs. 2.18 expected) appeared among a subset of the hourly employees, first hired before 1955, and employed between 5-15 years.

Cohort Studies↗

PubMed1991

Evaluation of selection bias in a cross-sectional survey.

Selection bias is inherent in all occupational cohorts. Selection bias at entry has long been known and is commonly referred to as a "healthy worker effect." Less well appreciated is selection during the life of a cohort resulting from life-style factors (e.g., cigarette smoking); aging with accompanying chronic diseases, economic and demographic circumstances; and diseases that might result from exposures suffered by the cohort being studied, that influence whether individuals remain in a trade. These factors weigh differently at different times. Thus, at any point in time, "surviving" members of a cohort reflect an amalgam of selection factors. When such groups are studied in cross-sectional surveys there can be uncertainty whether clinical, radiological and physiological findings are necessarily representative for the trade or occupation as a whole. We analyzed the results of a large clinical field survey of long-term asbestos insulation workers to investigate whether the non-participants differed substantially from those who were examined. Five thousand three hundred and fifty-five (5,355) men, of an initial cohort of 17,800 established January 1, 1967, had reached 30 or more years from onset of their work by July 1, 1981. All were invited to come for examination. Two thousand and seventy-seven (2,077) came, and 3,278 did not. We questioned a sample of 1,393 non-responders to see why they failed to appear. The answers did not give evidence of significant health-related selection influence. Sickness only infrequently kept them away. We then followed both groups--those examined and those not examined--to the end of 1987 for their mortality experience. There was no great difference. The non-responders had somewhat fewer deaths overall and proportionately fewer of asbestos-associated cancers, such as mesothelioma and lung cancer. The results indicated that, in this cohort, there did not seem to be health-related selection bias that determined whether or not cohort members responded to invitations for examinations.

Asbestos↗

PubMed1992

Cancer of the stomach and the colon-rectum among workers in a coke gas plant.

Four thousand nine hundred and eight male workers of the Hamburg gas plant, employed for 10 or more years during the period from January 1, 1900 to December 31, 1989, have been traced for cancer mortality. Based on their jobs, they were grouped into three subcohorts: gas furnace workers, workers in other parts of the plant, and white-collar workers. Despite the general "healthy worker effect," gas furnace workers showed a significant incidence of cancer of all sites (standardized mortality ratio [SMR] = 186), particularly cancers of the lung (SMR = 288), stomach (SMR = 177), and the colon-rectum (SMR = 184). In comparison to the death rates of white-collar workers, the manual workers in other parts of the plant also showed an excess of cancer mortality for cancer of these sites. The reason for this excess in cancer mortality seems to be due to the working conditions. The results contribute to the current evidence that exposure to coal carbonization fumes causes not only lung cancer, but also cancers of the stomach and colon-rectum.

Adult↗