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PubMed1986

Employment status and women's protection against coronary heart disease. Findings from the San Antonio Heart Study.

This study examined whether currently employed women are at increased risk of coronary heart disease relative to full-time homemakers. Subjects were 1,041 Mexican-American and non-Hispanic white women aged 25-64 years, residing in households randomly selected from three socioculturally distinct neighborhoods in San Antonio, Texas. No statistically significant differences between employed women and homemakers were found for obesity, total serum cholesterol, low density lipoprotein cholesterol, systolic and diastolic blood pressures, or cigarette smoking. Highly significant differences favoring employed women over homemakers were found for both Mexican Americans and non-Hispanic whites in high density lipoprotein (HDL) cholesterol, ratio of HDL cholesterol to total cholesterol, and triglycerides. These differences were not explained by obesity, exercise, cigarette smoking, alcohol consumption, use of exogenous estrogens, and use of oral contraceptives, or by the healthy worker effect, and were observed at all occupational levels. Employed women ate a less atherogenic diet than full-time homemakers, but it is not clear that this nutritional factor could explain the differences in HDL cholesterol and triglycerides found in this study. The magnitude of the employment status difference in HDL cholesterol for both ethnic groups was in a range (3-4 mg/100 ml) associated with protection against coronary heart disease.

Adult↗
PubMed2000

Exposure to electromagnetic fields and risk of central nervous system disease in utility workers.

Occupational exposure to electromagnetic fields has been associated with neurological diseases such as amyotrophic lateral sclerosis, senile dementia, Parkinson disease, and Alzheimer disease. I studied the incidence of central nervous system diseases in 30,631 persons employed in Danish utility companies between 1900 and 1993. I linked the cohort to the nationwide, population-based Danish National Register of Patients and compared the numbers of cases of these diseases observed between 1978 and 1993 with the corresponding rates in the general population. In addition I fit to the data on utility workers a multiplicative Poisson regression model in relation to estimated levels of exposure to 50-Hz electromagnetic fields. Overall, there was an increase in risk for senile dementia and motor neuron diseases combined. The incidences of Parkinson disease, Alzheimer disease, and other diseases of the central nervous system were essentially unrelated to exposure to electromagnetic fields. A decreased risk of epilepsy compared with the general population probably reflects a healthy worker effect; I observed an increased risk of epilepsy based on internal comparisons. The increased risk for senile dementia and motorneuron diseases may be associated with above-average levels of exposure to electromagnetic fields.

Adult↗
PubMed2001

A meta-analysis of cohort studies describing mortality and cancer incidence among chemical workers in the United States and western Europe.

We evaluated the mortality and cancer experience of employees of the chemical industry in the United States and western Europe, as reported in the peer-reviewed literature between 1966 and 1997 (>1 million workers and >15 million person-years). Cohort studies (N = 461) were grouped (N = 181) so that specific populations could be traced from the earliest to the most recently published report, and we extracted observed and expected numbers of cases for each of 35 mortality and 23 cancer incidence endpoints. We then generated standardized mortality ratios or standardized incidence ratios and 95% confidence intervals, and undertook meta-analyses of subcohorts (for example, gender, latency, or duration of employment), as well as the entire cohort. With few exceptions, the observed cause-specific mortality and site-specific cancer incidences were reassuring: overall, 10% fewer deaths were observed than expected. Fewer than expected deaths from all causes, cardiovascular disease, noncancer respiratory disease, cirrhosis of the liver, and external causes were observed, some or all of which may be attributed to a "healthy worker effect." Meta-analyses revealed weak to moderate excesses of lung and bladder cancers likely caused by occupational exposure to known human carcinogens. We also observed a 10-15% increase in lymphatic and hematopoietic cancers. Additional research is required to gain a more complete understanding of the potential role that methodology and environmental or occupational influences may play in these associations.

Cause of Death↗
PubMed1989

Mortality of workers at the Hanford site: 1945-1981.

Analyses of mortality of workers at the Hanford Site were updated to include an additional three years of data (1979-81). Deaths occurring in the state of Washington in the years 1982-85 were also evaluated. Hanford workers continued to exhibit a strong healthy worker effect with death rates substantially below those of the general U.S. population. Comparisons by level of radiation exposure within the Hanford worker population provided no evidence of a positive correlation of radiation exposure and mortality from all cancers combined or of mortality from leukemia. Estimates of cancer risk due to radiation were negative, but confidence intervals were wide, indicating that the data were consistent with no risk and with risks several times larger than estimates provided by major groups concerned with risk assessment. Of 18 categories of cancer analyzed, a correlation of borderline statistical significance was identified for female genital cancers (p = 0.05), but was interpreted as probably spurious. The previously identified correlation for multiple myeloma persisted (p = 0.002).

Environmental Exposure↗
PubMed1992

Low back and neck/shoulder pain in construction workers: occupational workload and psychosocial risk factors. Part 1: Relationship to low back pain.

The prevalence rate of musculoskeletal problems, especially low back pain and severe low back pain in a randomly selected sample of 1,773 construction workers was studied. Its relationship to physical and psychosocial factors was analyzed. The workers answered a postal questionnaire. Workload was measured by means of eight manual materials handling indices and ten psychosocial indices, based on results from factor analyses. The 1-year prevalence rate of low back pain was 54% and of severe low back pain 7%. The relationship to heavy manual materials handling differed with age in such a manner that it could be interpreted as a healthy worker effect. Between severe low back pain and both stooping or kneeling a dose-response relationship was found. The most prominent of the psychosocial factors associated with low back pain and severe low back pain were the stress index and the psychosomatic and psychic indices. The age-standardized prevalence rate ratio of low back pain was 1.6 (95% confidence interval 1.4-1.8) and for severe low back pain 3.1 (95% confidence interval 2.3-4), when workers reporting "high" stress were compared to workers reporting "low" stress.

Adult↗
PubMed1988

Reanalysis of lung cancer mortality in a National Cancer Institute study on mortality among industrial workers exposed to formaldehyde.

The results of an historical cohort study of mortality among individuals occupationally exposed to formaldehyde were announced in 1986 by Blair et al (JNCI 1986; 76:1071-1084). The study was a joint undertaking of the National Cancer Institute and the Formaldehyde Institute, and concluded, ". . .this large multiplant cohort study provided little evidence to suggest that formaldehyde exposure affected the mortality experience of these industrial workers." However, there were concerns by a number of workers that the design and analysis of the study had possibly masked an existing occupational hazard. Analyzing time-integrated exposure to formaldehyde without simultaneously considering length of exposure and comparing mortality of formaldehyde workers to mortality of the general population could have masked an increase in cancer risks because of the healthy worker effect. A copy of the data of the study was obtained from the principal investigator and reanalyzed. We find a significantly increased risk for all cancers and for lung cancer as a function of cumulative exposure when workers with higher levels of exposure are compared with those with little or no exposure while simultaneously considering length of exposure. When the risk ratio (RR) for lung cancer at less than or equal to 0.1 ppm cumulative exposure (CX) is taken as 1.0, the lung cancer RR for CX of 0.1 to 0.5 ppm is 1.41 (1.20 to 1.66), the RR for CX of 0.5 to 2.0 ppm is 1.73 (1.42 to 2.11), and the RR for CX greater than or equal to 2.0 is 1.70 (1.32 to 2.18). Hourly workers have a significantly higher RR than salaried workers (RR = 1.58).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Mortality of iron foundry workers: IV. Analysis of a subcohort exposed to formaldehyde.

In the final phase of the mortality study of workers at an automotive iron foundry, a subset (N = 3929) of the original cohort of 8147 men, consisting of those exposed to formaldehyde during the period from January 1960 through May 1987, was analyzed. In addition to the external US population, an internal population (N = 2032), consisting of men who had worked in the same foundry during the same time period but not in formaldehyde-exposed jobs, was also used as a referent. Follow-up continued through December 31, 1989. Smoking status was ascertained for 65.4% of the exposed and for 55.1% of the unexposed cohorts. Detailed work histories and evaluation of occupational exposures by an industrial hygienist enabled us to categorize cumulative formaldehyde and silica exposures. Standardized mortality ratios were used to compare the mortality experience of the exposed cohort with the US population and, because of concerns about the healthy worker effect, with an occupational referent population. Relative risks for race, formaldehyde exposure status, smoking status, and silica exposure level were estimated by fitting a Poisson regression model to four causes of death: cancers of the buccal cavity and pharynx, lung cancer, diseases of the respiratory system, and emphysema. No association between formaldehyde exposure and deaths from malignant or nonmalignant diseases of the respiratory system was found. Cigarette smoking and silica exposure were found to be significantly associated with deaths attributed to lung cancer and disease of the respiratory system.

Adolescent↗
PubMed1996

Evaluation of the utility of spirometry in a regional public health screening program for workers exposed to welding fumes.

The objective of this study was to determine the usefulness of spirometry in the screening of chronic pulmonary problems related to exposure to welding fumes, in a regional public health-based screening program. Pulmonary questionnaires and spirometric tests were administered twice at 5-year intervals on 229 welders/cutters (mean age, 39.9 years from 31 metal manufacturing plants. The baseline mean value at the first test for the forced expiratory volume in one second (FEV1) was 102% of predicted, the forced vital capacity (FVC) was 107%, and the FEV1/FVC ratio was 79%. The mean annual changes in the three spirometric indicators were -47 mL, -46 mL, and -0.3%, respectively. The usefulness of spirometry was assessed by looking at the relationship between exposure to welding fumes and changes in spirometric indices, in multivariate linear regression analysis, accounting for age, height, and smoking. A high lifetime exposure to welding fumes was associated with better lung functions in the cross-sectional approach (healthy worker effect) but not in the longitudinal approach, where no association was found. We concluded that the public health regional application of this screening program generated too many sources of variation for spirometry to fulfill the objective of early detection of pulmonary function decline related to exposure to welding fumes. Based on these observations, we recommend that maintaining questionnaire screening, with spirometry reserved as a second-line diagnostic intervention.

Adult↗
PubMed1997

A mortality study of oil refinery and petrochemical employees.

Results from a prospective mortality surveillance of 3803 refinery and petrochemical workers at a Shell Oil Company facility in Louisiana are presented. This report includes employees who worked more than 6 months before January 1, 1994 and pensioners who were alive as of January 1, 1973. Vital status was ascertained through 1993. Regardless of the comparison population used to calculate expected numbers (United States, Louisiana, or the surrounding tri-parish area), significantly fewer deaths were observed for all causes combined, all malignant neoplasms, heart disease, nonmalignant respiratory disease, and cirrhosis of the liver among male employees after 10 or more years' latency. With the United States as comparison, the all causes combined standardized mortality ratio (SMR) was 0.72 (95% confidence interval [CI] = 0.65 to 0.79), and the SMR for all cancer was 0.75 (95% CI = 0.61 to 0.92). The brain cancer rate for this group was nonsignificantly increased, with five observed deaths and three expected deaths, whereas mortality from leukemia was consistently lower than expected. The overall favorable mortality experienced by employees at this refinery and chemical plant is probably a result of a combination of factors, such as the healthy worker effect, relatively low risks related to the workplace, and the beneficial effects of continuing employment.

Adult↗
PubMed1999

Pulmonary function in workers exposed to low levels of fuel-oil ash.

Previously, we reported significant lung function changes after exposure to fuel-oil ash during a boiler overhaul in which median PM10 and vanadium concentrations were 2.9 mg/m3 and 11.9 micrograms/m3, respectively. In this study, we examined prospectively 18 boilermakers involved in the short-term, partial overhaul of a large, oil-fired boiler where occupational exposures to PM10 and metals were relatively low. Vanadium and PM10 exposure levels were measured before and during boiler work. For PM10, median exposure before and during boiler work was 0.5 and 0.6 mg/m3, respectively. For vanadium, median exposure before and during boiler work was 1.0 and 12.7 micrograms/m3, respectively, comparable with the results of our previous study. Spirometric (PFT) testing was done three times: first day on the job (PFT1), end of overhaul (PFT2), and 2 weeks post-overhaul (PFT3). Spirometry results were analyzed using repeated measures analysis of variance. No significant differences were found. Boilermakers working on a short-term overhaul of an oil-fired boiler exhibited no significant change in any lung function parameter comparing pre-, during, and 2 weeks post-exposure. The comparatively low levels of exposure to PM10 and vanadium observed during boiler work, the short duration of the overhaul, and the healthy worker effect are possible explanations for these results.

Adult↗
PubMed2003

Respiratory symptoms and ventilatory function in workers exposed to portland cement dust.

The healthy worker effect and incomplete exposure information have been problems in former studies regarding the association between exposure to Portland cement dust and respiratory effects. We included former workers and made an individual estimation of particle exposure to reduce the selection bias in this controlled cross-sectional study on the effects of cement dust exposure on respiratory symptoms and ventilatory function in long-term exposed Norwegian cement plant workers. A total of 119 workers from the largest cement plant in Norway and 50 workers from a nearby control plant, born 1918 to 1938, performed spirometry and gave information on respiratory symptoms in 1998 and 1999. The prevalence of symptoms and mean pulmonary function indices were similar for exposed workers and controls. There was no dose-response-related increase in symptoms or decrease in lung function indices. The estimated power to detect a true difference between forced expiratory volume in one second (FEV1) in the two groups of 0.3l was 0.90, assuming 95% significance level. The prevalence of chronic obstructive pulmonary disease was 14.3% in the exposed group and 14.0% among the controls. These findings do not support the hypothesis that cement dust exposure has a negative impact on lung function or gives an increase in respiratory symptoms.

Adult↗
PubMed2006

Lung cancer mortality in the German chromate industry, 1958 to 1998.

OBJECTIVES: We conducted a mortality study of two German chromate production facilities and evaluated possible dose-response relationships between hexavalent chromium exposure and lung cancer. METHODS: Mortality was followed-up through 1998 and limited to those employed since each plant converted to a no-lime production process. More than 12,000 urinalysis results of chromium levels were available, as was smoking information. RESULTS: All-cause mortality indicated a healthy worker effect (standardized mortality ratio [SMR] = 0.80, 95% confidence interval [CI] = 0.67-0.96); however, lung cancers appeared to be increased (SMR = 1.48, 95% CI = 0.93-2.25). No clear dose-response was found in stratified analyses by duration of employment and time since hire. On the basis of urinary chromium data, lung cancer risk was elevated only in the highest exposure group (SMR = 2.09, 95% CI = 1.08-3.65). CONCLUSIONS: These data suggest a possible threshold effect of occupational hexavalent chromium exposure on lung cancer.

Adult↗
PubMed1999

The incidence of epilepsy and unprovoked seizures in multiethnic, urban health maintenance organizations.

PURPOSE: Studies of the incidence of epilepsy are limited to a few populations in which new cases can be ascertained. Health maintenance organization (HmO) populations were studied to determine the incidence in a multiethnic, urban United States population. METHODS: Cases of initial unprovoked seizure disorder or epilepsy while enrolled in an HMO between 1988 and 1994 were ascertained. Ethnicity was obtained from the medical records and was part of a nested case-control study. RESULTS: There were 197 incidence cases of epilepsy and 275 of initial unprovoked seizure diagnosis. The incidence rate in the age range 0-64 years was 35.5 per 100,000 for epilepsy and 50.9 for initial unprovoked seizure. When compared with population-based studies, rates were slightly higher in children younger than 15, similar for the 15- to 24-year age group, but lower for ages 25-64 years. The ethnicity-specific odds ratios for initial unprovoked seizure, by using non-Hispanic white as the referent, were 1.04 (0.73-1.49) for African-American, 0.97 (0.64-1.48) for Hispanic, and 0.25 (0.08-0.84) for Asian-American. CONCLUSIONS: The lower rate in the HMO population is presumably due to a healthy-worker effect. The ethnicity-specific incidence rates do not differ in this population.

Adolescent↗
PubMed1993

Comparing toxicologic and epidemiologic studies: methylene chloride--a case study.

Exposure to methylene chloride induces lung and liver cancers in mice. The mouse bioassay data have been used as the basis for several cancer risk assessments. The results from epidemiologic studies of workers exposed to methylene chloride have been mixed with respect to demonstrating an increased cancer risk. The results from a negative epidemiologic study of Kodak workers have been used by two groups of investigators to test the predictions from the EPA risk assessment models. These two groups used very different approaches to this problem, which resulted in opposite conclusions regarding the consistency between the animal model predictions and the Kodak study results. The results from the Kodak study are used to test the predictions from OSHA's multistage models of liver and lung cancer risk. Confidence intervals for the standardized mortality ratios (SMRs) from the Kodak study are compared with the predicted confidence intervals derived from OSHA's risk assessment models. Adjustments for the "healthy worker effect," differences in length of follow-up, and dosimetry between animals and humans were incorporated into these comparisons. Based on these comparisons, we conclude that the negative results from the Kodak study are not inconsistent with the predictions from OSHA's risk assessment model.

Animals↗
PubMed1992

Mortality and occupational exposure to radiation: first analysis of the National Registry for Radiation Workers.

OBJECTIVE: To study cause specific mortality of radiation workers with particular reference to associations between fatal neoplasms and level of exposure to radiation. DESIGN: Cohort study. SETTING: United Kingdom. SUBJECTS: 95,217 radiation workers at major sites of the nuclear industry. MAIN OUTCOME MEASURE: Cause of death. RESULTS: Most standardised mortality ratios were below 100: 83 unlagged, 85 with a 10 year lag for all causes; 84 unlagged, 86 lagged for all cancers; and 80 for all known other causes, indicating a "healthy worker effect." The deficit of lung cancer (75 unlagged, 76 lagged) was significant at the 0.1% level. Standardised mortality ratios were significantly raised (214 unlagged, 303 lagged) for thyroid cancer, but there was no evidence for any trend with external recorded radiation dose. Dose of external radiation and mortality from all cancers were weakly correlated (p = 0.10), and multiple myeloma was more strongly correlated (p = 0.06); for leukaemia, excluding chronic lymphatic, the trend was significant (p = 0.03; all tests one tailed). The central estimates of lifetime risk derived from these data were 10.0% per Sv (90% confidence interval less than 0 to 24%) for all cancers and 0.76% per Sv (0.07 to 2.4%) for leukaemia (excluding chronic lymphatic leukaemia). These are, respectively, 2.5 times and 1.9 times the risk estimates recommended by the International Commission on Radiological Protection, but 90% confidence intervals are large and the commission's risk factors fall well within the range. The positive trend with dose for all cancers, from which the risk estimate was derived, was not significant. The positive association between leukaemia (except chronic lymphatic leukaemia) was significant and robust in subsidiary analyses. This study showed no association between radiation exposure and prostatic cancer. CONCLUSION: There is evidence for an association between radiation exposure and mortality from cancer, in particular leukaemia (excluding chronic lymphatic leukaemia) and multiple myeloma, although mortality from these diseases in the study population overall was below that in the general population. The central estimates of risk from this study lie above the most recent estimates of the International Commission on Radiological Protection for leukaemia (excluding chronic lymphatic leukaemia) and for all malignancies. However, the commission's risk estimates are well within the 90% confidence intervals from this study. Analysis of combined cohorts of radiation workers in the United States indicated lower risk estimates than the commission recommends, and when the American data are combined with our analysis the overall risks are close to those estimated by the commission. This first analysis of the National Registry for Radiation Workers does not provide sufficient evidence to justify a revision in risk estimates for radiological protection purposes.

Adult↗
PubMed1993

Risk of fatal accidents occurring other than at sea among Icelandic seamen.

OBJECTIVE: To study mortality among seamen, particularly from fatal accidents that occurred other than at sea. DESIGN: Cohort study. SETTING: Iceland. SUBJECTS: 27,884 seamen, both fishermen and sailors from the merchant fleet, who had been members of a pension fund from 1958 to 1986. MAIN OUTCOME MEASURES: Cause of death (ICD seventh revision), standardised mortality ratio. RESULTS: Most standardised mortality ratios were greater than 1, being 1.26 for all causes and 1.83 for all external causes. There was no healthy worker effect. The excess of deaths from all external causes included all subcategories of death from accidents, poisonings, and violence and not just accidents at sea (water transport accidents, ICD codes E850-E858). A significant trend was found for length of employment and mortality from all accidents at sea, drowning at sea, accidental poisoning, other accidents, and accidental drowning; correlation coefficients for all causes, all accidents, suicide, and injuries undetermined whether accidentally or purposely inflicted were 0.7-0.8. Compared with seamen who started work during 1968-77, those who started work in 1978 or later had higher mortality from all causes, road traffic accidents, poisoning, other accidents, homicide, and injuries unknown whether accidentally or purposely inflicted, but not from all accidents at sea and accidental drowning. CONCLUSION: Seamen seem to be a special group with a high risk of fatal accidents occurring not only at sea. The association between fatal accidents other than at sea and length of employment as seamen indicates that seamen are modified by their occupation towards hazardous behaviour or a risky lifestyle.

Accident Proneness↗
PubMed2004

Update of a prospective study of mortality and cancer incidence in the Australian petroleum industry.

AIMS: To update the analysis of the cohort mortality and cancer incidence study of employees in the Australian petroleum industry. METHODS: Employees from 1981 to 1996 were traced through the Australian National Death Index and the National Cancer Statistics Clearing House. Cause specific mortality and cancer incidence were compared with those of the Australian population by means of standardised mortality ratios (SMRs) and standardised incidence ratios (SIRs). Associations between increased incidence of specific cancers and employment in the petroleum industry were tested by trends according to period of first employment, duration of employment, latency, and hydrocarbon exposure, adjusting for personal smoking history where appropriate. Total follow up time was 176 598 person-years for males and 10 253 person-years for females. RESULTS: A total of 692 of the 15 957 male subjects, and 16 of the 1206 female subjects had died by the cut off date, 31 December 1996. In males, the all-cause SMR and the SMRs for all major disease categories were significantly below unity. There was a non-significant increase of the all-cancer SIR (1.04, 95% CI 0.97 to 1.11). There was a significant increase of the incidence of melanoma (SIR 1.54, 95% CI 1.30 to 1.81), bladder cancer (SIR 1.37, 95% CI 1.00 to 1.83), and prostate cancer (SIR 1.19, 95% CI 1.00 to 1.40), and a marginally significant excess of pleural mesothelioma (SIR 1.80, 95% CI 0.90 to 3.22), leukaemia (SIR 1.39, 95%CI 0.91 to 2.02), and multiple myeloma (SIR 1.72, 95% CI 0.96 to 2.84). CONCLUSIONS: Most cases of mesothelioma are probably related to past exposure to asbestos in refineries. The melanoma excess may be the result of early diagnosis. The excess bladder cancer has not been observed previously in this industry and is not readily explained. The divergence between cancer incidence and cancer mortality suggests that the "healthy worker effect" may be related to early reporting of curable cancers, leading to increased likelihood of cure and prolonged mean survival time.

Australia↗
PubMed1982

Census-based mortality study of fertiliser manufactures.

This study was designed to investigate whether exposure to nitrate-containing dust during fertiliser manufacture was associated with an excess of deaths from cancer in general or specifically from cancers of the digestive tract, liver, lung, and bladder. It was based on data extracted from census schedules by the Office of Population Censuses and Surveys, occupational characteristics recorded by fertiliser workers at the 1961 and 1971 censuses of England and Wales being related to subsequent mortality ascertained through the National Health Service Central Register. The 1961 cohort, followed up until 1978, showed a "healthy worker effect" and no evidence of excess mortality from cancer at any site. The 1971 cohort also showed below average mortality during 1971-7 for all causes of death and for circulatory diseases, but there were more deaths from cancer than expected, due mainly to an excess of cancers of the lung and digestive tract. The excess of cancer was more pronounced, but not statistically significant, when compared with other employed men. Though the numbers for comparison were small, there was weak evidence of an association between cancer mortality and frequency of exposure to nitrate-containing dust in this cohort. It is difficult to reconcile the excess cancer mortality in the 1971 cohort with the more favorable level in the earlier cohort, since industrial hygiene has improved and the cohorts showed a similar distribution by region and social class. To examine further these conflicting results the 1971 cohort will be followed for a longer period and re-examined when more deaths have accrued.

Adult↗