Mortality Patterns and Trends Among 127,266 U.S.-Based Men in a Petroleum Company: Update 1979–2000

[Environmental and occupational risk factors for myelodysplastic syndrome]

Chemotherapy and radiotherapy for a previous cancer can lead to subsequent myelodysplastic syndrome (MDS). However, these therapy-related cases are hypothesized to explain only 5 % of diagnosed MDS cases. Environmental or occupational exposure to chemicals or radiations has also been reported to be associated with higher risk of MDS. The present review analyses those studies evaluating the association of MDS with environmental or occupational risk factors. There is sufficient evidence that environmental or occupational exposure to ionizing radiation or benzene can cause MDS. Tobacco smoking is also a sufficiently documented riskfactor for MDS. A positive association has been reported between exposure to pesticides and MDS. However, there is only limited evidence that this association could be causal.

Mortality of 196,826 Men and Women Working in U.S.-Based Petrochemical and Refinery Operations: Update 1979 to 2010

OBJECTIVE

To describe mortality trends of men and women working in various petrochemical and refinery operations of a U.S.-based company.

METHODS

The cohort consists of full-time employees with at least 1 day of service during 1979 through 2010. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were calculated for 111 possible causes of death studied.

RESULTS

SMRs for malignant mesothelioma and asbestosis were highest for the 1940s decade of hire. Increased SMRs were observed for malignant melanoma and motor neuron disease with no obvious work patterns. Decreasing mortality patterns were observed for aplastic anemia and acute nonlymphocytic leukemia.

CONCLUSIONS

Mortality surveillance of this large established cohort aids in assessing the chronic health status of the workforce. Identifying methods for incorporating job-exposure matrices and nonoccupational risk factors could further enhance interpretations for some findings such as motor neuron disease.

Cancer Incidence and Mortality among Petroleum Industry Workers and Residents Living in Oil Producing Communities: A Systematic Review and Meta-Analysis

Petroleum extraction and refining are major sources of various occupational exposures and of air pollution and may therefore contribute to the global cancer burden. This systematic review and meta-analysis is aimed at evaluating the cancer risk in petroleum-exposed workers and in residents living near petroleum facilities. Relevant studies were identified and retrieved through PubMed and Web of Science databases. Summary effect size (ES) and 95% confidence intervals (CI) were analysed using random effect models, and heterogeneity across studies was assessed (I2). Overall, petroleum industry work was associated with an increased risk of mesothelioma (ES = 2.09, CI: 1.58-2.76), skin melanoma (ES = 1.34, CI: 1.06-1.70 multiple myeloma (ES =1.81, CI: 1.28-2.55), and cancers of the prostate (ES = 1.13, Cl: 1.05-1.22) and urinary bladder (ES = 1.25, CI: 1.09-1.43) and a decreased risk of cancers of the esophagus, stomach, colon, rectum, and pancreas. Offshore petroleum work was associated with an increased risk of lung cancer (ES = 1.20; 95% CI: 1.03-1.39) and leukemia (ES = 1.47; 95% CI: 1.12-1.92) in stratified analysis. Residential proximity to petroleum facilities was associated with childhood leukemia (ES = 1.90, CI: 1.34-2.70). Very few studies examined specific exposures among petroleum industry workers or residents living in oil producing communities. The present review warrants further studies on specific exposure levels and pathways among petroleum-exposed workers and residents living near petroleum facilities.

The importance of evaluating specific myeloid malignancies in epidemiological studies of environmental carcinogens

INTRODUCTION

Although myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), myeloproliferative neoplasms (MPN) - including chronic myeloid leukemia (CML) - and myelodysplastic/myeloproliferative neoplasms (MDS/MPN) are largely clinically distinct myeloid malignancies, epidemiological studies rarely examine them separately and often combine them with lymphoid malignancies, limiting possible etiological interpretations for specific myeloid malignancies.

METHODS

We systematically evaluated the epidemiological literature on the four chemical agents (1,3-butadiene, formaldehyde, benzene, and tobacco smoking, excluding pharmaceutical, microbial and radioactive agents, and pesticides) classified by the International Agency for Research on Cancer as having sufficient epidemiological evidence to conclude that each causes "myeloid malignancies." Literature searches of IARC Monographs and PubMed identified 85 studies that we critically assessed, and for appropriate subsets, summarized results using meta-analysis.

RESULTS

Only two epidemiological studies on 1,3-butadiene were identified, but reported findings were inadequate to evaluate specific myeloid malignancies. Studies on formaldehyde reported results for AML and CML - and not for MDS or MPN - but reported no increased risks. For benzene, several specific myeloid malignancies were evaluated, with consistent associations reported with AML and MDS and mixed results for CML. Studies of tobacco smoking examined all major myeloid malignancies, demonstrating consistent relationships with AML, MDS and MPN, but not with CML.

CONCLUSIONS

Surprisingly few epidemiological studies present results for specific myeloid malignancies, and those identified were inconsistent across studies of the same exposure, as well as across chemical agents. This exercise illustrates that even for agents classified as having sufficient evidence of causing "myeloid malignancies," the epidemiological evidence for specific myeloid malignancies is generally limited and inconsistent. Future epidemiological studies should report findings for the specific myeloid malignancies, as combining them post hoc - where appropriate - always remains possible, whereas disaggregation may not. Furthermore, combining results across possibly discrete diseases reduces the chances of identifying important malignancy-specific causal associations.

Systematic Review and Meta-Analysis of Selected Cancers in Petroleum Refinery Workers

OBJECTIVE

We studied the risk of 11 cancers of a priori interest in petroleum refinery workers.

METHODS

Iterative searches identified 36 studies for the 11 cancer sites. Statistical heterogeneity and publication bias were assessed to enhance interpretation of meta-relative risks.

RESULTS

Statistical heterogeneity was marked for mesothelioma, but was largely due to study quality. Higher quality studies showed a meta-relative risk (RR) of 3.22, (95% prediction interval 1.45 to 7.23). Melanoma (meta-RR = 1.23) and acute lymphoid leukemia (meta-RR = 1.51), showed results consistent with higher risk, but both were driven by one or two studies. Eight other cancer outcomes showed summary meta-RR's consistent with unity.

CONCLUSIONS

Most cancer outcomes are consistent with background risk in refinery workers. This work has clarified an excess mesothelioma risk, conditional on study quality stratification. Continued surveillance is warranted for melanoma and ALL.

Occupational chemical exposure and diabetes mellitus risk

Diabetes mellitus (DM) is a group of metabolic diseases that may originate from an interaction between genetic and lifestyle risk factors. However, the possible role of occupational chemical exposures in the disease development and progression remains unclear. Therefore, this review aimed to provide a comprehensive evaluation of the relationship between occupational exposure to specific chemical substances or industrial activities and DM morbidity and mortality outcomes. Although some positive findings may support the diabetogenic role of certain pesticides and dioxins in different workplaces, the variable conditions of exposure, the lack of quantitative environmental or biological monitoring data and the different outcomes evaluated do not allow defining a specific exposure-disease causality. Therefore, further epidemiological studies will be necessary to adequately assess modes of action for different substances, dose–response relationships as well as individual susceptibility factors potentially affecting the exposure-disease continuum. Overall, this appears important to adequately assess, communicate and manage risks in occupational chemical exposure settings with the aim to protect workers and build healthier job conditions for diabetic employees.

Increased Standardised Incidence Ratio of Malignant Pleural Mesothelioma in Taiwanese Asbestos Workers: A 29-Year Retrospective Cohort Study

Objective. This paper aimed to determine the standardised incidence ratio (SIR) of malignant pleural mesothelioma (MPM) in workers exposed to asbestos in Taiwan. Methods. All workers employed in asbestos-related factories and registered by the Bureau of Labour Insurance between 1 March, 1950, and 31 December, 1989, were included in the study and were followed from 1 January, 1980, through 31 December, 2009. Incident cases of all cancers, including MPM (ICD-9 code: 163), were obtained from the Taiwan Cancer Registry. SIRs were calculated based on comparison with the incidence rate of the general population of Taiwan and adjusted for age, calendar period, sex, and duration of employment. Results. The highest SIR of MPM was found for male workers first employed before 1979, with a time since first employment more than 30 years (SIR 4.52, 95% CI: 2.25–8.09). After consideration of duration of employment, the SIR for male MPM was 5.78 (95% CI: 1.19–16.89) for the workers employed for more than 20 years in asbestos-related factories. Conclusions. This study corroborates the association between occupational asbestos exposure and MPM. The highest risk of MPM was found among male asbestos workers employed before 1979 and working for more than 20 years in asbestos-related factories.

Mesothelioma in occupational cohort studies: methodological considerations

OBJECTIVE

This article describes effective strategies for the identification and valid assessment of mortality due to mesothelioma.

METHODS

We manually reviewed all death certificates for mention of mesothelioma for all International Classification of Diseases (ICD) revisions. We tested the accuracy of our ascertainment method by comparing New Jersey death certificate data from our health status registry with histologically confirmed cases from the New Jersey State Cancer Registry.

RESULTS

We found reasonably good agreement between death certificate diagnoses and histologically confirmed cases, κ coefficient 0.86 (95% confidence interval, 0.76 to 0.95). Most mesothelioma deaths in our test and North American cohorts were coded to unspecified anatomical sites.

CONCLUSIONS

Limiting ascertainment to pleura and peritoneum ICD codes underestimates mesothelioma deaths. Reviewing all ICD codes that could contain mesothelioma is the only effective method for complete capture of mesothelioma diagnoses.

Cancer mortality and quantitative oil production in the Amazon region of Ecuador, 1990-2010

Purpose

Controversy persists over whether cancer risk is increased in communities surrounding oil fields, especially in the Oriente region of Ecuador. This ecologic study uses quantitative exposure data, updated mortality data, and improved statistical methods to study the impact of oil exploration and production activities on cancer mortality rates in the Oriente.

Methods

Cancer mortality rates in the Oriente in 1990 through 2010 were compared between seven cantons with active oil exploration and production as of 1990 and thirteen cantons with little or no such activities. Poisson regression was used to estimate mortality rate ratios (RRs) adjusted for age and sex. In a two-stage analysis, canton-specific log-RRs were regressed against quantitative estimates of cumulative barrels of oil produced and well-years per canton, adjusting for canton-level demographic and socioeconomic factors.

Results

Overall and site-specific cancer mortality rates were comparable between oil-producing and non-oil-producing cantons. For overall cancer mortality in males and females combined, the RR comparing oil-producing to non-oil-producing cantons was 0.85 [95 % confidence interval (CI) 0.72–1.00]. For leukemia mortality, the corresponding RR was 0.80 (95 % CI 0.57–1.13). Results also revealed no excess of mortality from acute non-lymphocytic, myeloid, or childhood leukemia. Standardized mortality ratios were consistent with RRs. Canton-specific RRs showed no pattern in relation to oil production volume or well-years.

Conclusions

Results from this first ecologic study to incorporate quantitative measures of oil exploration and production showed no association between the extent of these activities and cancer mortality, including from cancers associated with benzene exposure.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-013-0308-8) contains supplementary material, which is available to authorized users.

The healthy worker effect in cancer incidence studies

Use of the general population as a reference might cause serious underestimation of the risk of cancer in working populations because of the healthy worker effect. Using incidence rates, we studied how this underestimation varied according to subtypes of cancer by comparing a large cohort of randomly selected Norwegian workers hired between 1981 and 2003 (n = 366,114) with the general Norwegian population. The cohort was linked to the Cancer Registry of Norway, including all new cancer cases (n = 11,271) reported up to 2003. We found marked potential for the healthy worker effect for overall cancer incidence in male workers (standardized incidence ratio (SIR) = 0.91, 95% confidence interval: 0.89, 0.93) but not in female workers (SIR = 0.99, 95% confidence interval: 0.95, 1.03). A statistically significantly lower incidence was found among men for cancers of the head and neck (SIR = 0.78), lung (SIR = 0.81), prostate (SIR = 0.93), kidney (SIR = 0.83), and bladder (SIR = 0.77) and for leukemia (SIR = 0.80), whereas an increased incidence was found for malignant melanoma among both men (SIR = 1.09) and women (SIR = 1.29) and for ovarian cancer in women (SIR = 1.32). Depending on the type of cancer being studied, marked potential exists for both underestimation and overestimation of cancer risk when the general population is used as the reference for studies of worker populations.

Work-related leukemia: a systematic review

Leukemia is a complex disease, which only became better understood during the last decades following the development of new laboratory techniques and diagnostic methods. Despite our improved understanding of the physiology of the disease, little is yet known about the causes of leukemia. A variety of potential risk factors have been suggested so far, including personal habits and lifestyle, and a wide range of occupational or environmental exposures. A causal association with leukemia has only been documented to date for ionizing radiation, benzene and treatment with cytostatic drugs, but there is an ongoing scientific debate on the possible association of leukemia with a number of other work-related hazards. In this article, we have reviewed scientific studies, published over the past 5 years, which investigated potential associations between leukemia and exposure to occupational risk factors. The systematic literature review took place via electronic databases, using specific search criteria, and independent reviewers have further filtered the search results to identify the number of articles, presented in our paper. A large number of studies included in the review referred to the effects of ionizing radiation, where new data suggest that the effects of exposure to small doses of ionizing radiation should probably be reevaluated. Some other works appear to substantiate a potential association of the disease with certain pesticides. Further research is also suggested regarding the role of infectious agents or exposure to certain chemicals like formaldehyde or butadiene in the pathogenesis of leukemia.

Risk of MS is not associated with exposure to crude oil, but increases with low level of education

BACKGROUND

Offshore workers in the Norwegian upstream petroleum industry are exposed to a number of chemicals such as organic solvents, mineral oils and other hydrocarbons, possibly contributing to an increased risk of multiple sclerosis (MS).

OBJECTIVE

To estimate the risk of MS in this population compared with the general working population in Norway, adjusting for education.

METHODS

Using the Norwegian Registry of Employers and Employees we included all 27,900 offshore workers registered from 1981 to 2003 and 366,805 referents from the general working population matched by gender, age and community of residence. The cohort was linked to the Norwegian MS Registry and the Norwegian Education Registry.

RESULTS

There was no increased risk of MS among the offshore workers. We found a marked and linear inverse relationship between level of education and the risk of MS in the total study population, with a rate ratio of 0.48 (95% CI, 0.53 to 0.88) for workers with a graduate degree compared to workers with elementary school only.

CONCLUSIONS

These findings do not support a major aetiological role of petroleum-based products, but rather point to smoking and other lifestyle factors related to the level of education as being important for the risk of MS.

Strategies for using the National Death Index and the Social Security Administration for death ascertainment in large occupational cohort mortality studies

This paper describes a multistage process to improve the completeness and time-/cost-effectiveness of ascertaining deaths in large employee cohorts. The process uses the vital status data service of the Social Security Administration (SSA) to identify people who can be confirmed as living, in order to reduce the number of records submitted for a National Death Index (NDI) search. The accuracy of SSA results is verified by submitting a sample of known-living and known-deceased people. For the NDI search results, an algorithm based on a discrete combination of matching variables is applied to distinguish NDI records as true, false, or questionable matches to reduce the number of death certificate requests to state offices. Subsequent decision making is based on manual reviews at various stages. In a cohort of over 200,000 employees, an SSA vital status search reduced the size of the NDI death record search by 85%. The algorithm sorted thousands of NDI records into 15 distinct strata and reduced the number of death certificate requests by 76%. The authors believe that the matching process is enhanced by obtaining paper copies of death certificates from the states, because death certificates often provide additional information and aid in determining true matches to company employees.

Mortality patterns and trends among 49,705 U.S.-based women in a petroleum company: update 1979-2000

OBJECTIVE

To examine mortality patterns and trends in a cohort of women employed in U.S. operating segments of a petroleum company.

METHODS

Based on human resources databases, we defined a cohort of 49,705 U.S.-based women with at least one day of company employment during 1979 to 2000. These data sources provided demographic and most work history information. Standardized mortality ratios and 95% confidence intervals were calculated for 95 causes of death for the total cohort and with separate analyses by job type and operating segment when numbers allowed.

RESULTS

Cohort women have a 25% lower overall death rate than the general U.S. female population comparison. This lower rate is expected in light of the "healthy worker effect" that influences employee studies. Circulatory diseases have a deficit of 40%, and external causes of death and cancer have deficits of 13% and 9%, respectively. For analyses by job type, office/clerical workers have an elevation in ovarian cancer (standardized mortality ratio = 1.40, 95% confidence interval = 1.02 to 1.87), based on 46 deaths, with no work-related patterns. White-collar groups have generally large overall deficits for noncancer causes of death. In contrast, and based on smaller numbers, operators and laborers have elevations of motor vehicle accidents and other external causes of death, and laborers also have elevations of cerebrovascular disease and chronic obstructive pulmonary disease. These variations by job type are probably associated with differences in lifestyle factors.

CONCLUSIONS

This large mortality surveillance study of women in the petroleum industry provides an opportunity for meaningful analysis of many causes of death. The study found an overall favorable mortality profile and, for a small number of elevations, helped identify possible subgroups for health and safety prevention programs and interventions.