An interdisciplinary framework for derivation of occupational exposure limits.

Protecting the health and safety of workers in industrial operations is a top priority. One of the resources used in industry to ensure worker safety is the occupational exposure limit (OEL). OELs are derived from the assessment and interpretation of empirical data from animal and/or human studies. There are various guidelines for the derivation and implementation of OELs globally, with a range of stakeholders (including regulatory bodies, governmental agencies, expert groups and others). The purpose of this manuscript is to supplement existing guidance with learnings from a multidisciplinary team approach within an industry setting. The framework we present is similar in construct to other risk assessment frameworks and includes: (1) problem formulation, (2) literature review, (3) weight of evidence considerations, (4) point of departure selection/derivation, (5) application of assessment factors, and the final step, (6) derivation of the OEL. Within each step are descriptions and examples to consider when incorporating data from various disciplines such as toxicology, epidemiology, and exposure science. This manuscript describes a technical framework by which available data relevant for occupational exposures is compiled, analyzed, and utilized to inform safety threshold derivation applicable to OELs.

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.

Mortality Update of a Cohort of Canadian Petroleum Workers.

OBJECTIVE: This study updates the mortality experience of over 25,000 workers in a large Canadian petroleum company through December 31, 2006. METHODS: Standardized mortality ratios were generated for all-cause and specific cause mortality. RESULTS: All cause and all cancer mortality were favorable compared with the general Canadian population. Cancers of previous interest were largely consistent with expectation. There is a continuing excess of mesothelioma, which is of similar magnitude as the previous update, although based on larger numbers. This excess is mostly attributable to men who died in their 50s and 60s and who worked in the refining sector. CONCLUSION: Most causes of death show mortality rates lower than the Canadian general population. Given the excess of mesothelioma observed, this study supports ongoing vigilance in asbestos exposure control programs, as refineries continue to remove asbestos from their facilities.

Age correction in monitoring audiometry: method to update OSHA age-correction tables to include older workers.

OBJECTIVES: The US Occupational Safety and Health Administration (OSHA) Noise Standard provides the option for employers to apply age corrections to employee audiograms to consider the contribution of ageing when determining whether a standard threshold shift has occurred. Current OSHA age-correction tables are based on 40-year-old data, with small samples and an upper age limit of 60 years. By comparison, recent data (1999-2006) show that hearing thresholds in the US population have improved. Because hearing thresholds have improved, and because older people are increasingly represented in noisy occupations, the OSHA tables no longer represent the current US workforce. This paper presents 2 options for updating the age-correction tables and extending values to age 75 years using recent population-based hearing survey data from the US National Health and Nutrition Examination Survey (NHANES). Both options provide scientifically derived age-correction values that can be easily adopted by OSHA to expand their regulatory guidance to include older workers. METHODS: Regression analysis was used to derive new age-correction values using audiometric data from the 1999-2006 US NHANES. Using the NHANES median, better-ear thresholds fit to simple polynomial equations, new age-correction values were generated for both men and women for ages 20-75 years. RESULTS: The new age-correction values are presented as 2 options. The preferred option is to replace the current OSHA tables with the values derived from the NHANES median better-ear thresholds for ages 20-75 years. The alternative option is to retain the current OSHA age-correction values up to age 60 years and use the NHANES-based values for ages 61-75 years. CONCLUSIONS: Recent NHANES data offer a simple solution to the need for updated, population-based, age-correction tables for OSHA. The options presented here provide scientifically valid and relevant age-correction values which can be easily adopted by OSHA to expand their regulatory guidance to include older workers.

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.

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.

Mortality patterns and trends among 127,266 U.S.-based men in a petroleum company: update 1979-2000.

OBJECTIVE: To assess patterns and trends in mortality among men employed in U.S. operating segments of a petroleum company. METHODS: We defined a cohort of 127,266 men with at least 1 day of employment during the period of 1979 through 2000. Computerized human resources databases were the basis of the cohort definition as well as the source of demographic and most work history information. Standardized mortality ratios (SMR) and 95% confidence intervals (CI) were calculated for 94 causes of death, including analyses by operating segment and job type. RESULTS: Most SMR results are below unity. The main exception is mesothelioma (SMR = 1.49; 95% CI = 1.15 to 1.90), which has elevations three times greater than expectation among some groups of men working in manufacturing sites who were hired before 1960. SMRs for cancers of the blood and blood-forming organs are generally close to unity, whereas men in the chemicals segment have 17 deaths due to acute non-lymphocytic leukemia (SMR = 1.81; 95% CI = 1.06 to 2.90), with no temporal or job type patterns. Men in the downstream segment have an elevation of aplastic anemia (SMR = 2.19; 95% CI = 0.95 to 4.32), based on eight deaths. There are eight deaths from malignant melanoma among downstream drivers (SMR = 2.46; 95% CI = 1.06 to 4.84), and motor vehicle accident rates are slightly elevated among some groups of younger and shorter-term operators. CONCLUSIONS: This comprehensive study indicates an overall favorable mortality profile for this workforce. For a few elevations, the study helps guide decisions about future surveillance, focused studies, and other follow-up actions.

Review of the literature on benzene exposure and leukemia subtypes.

The epidemiologic literature on benzene exposure and leukemia in the MEDLINE and TOXNET databases was examined through October 2004 using the keywords "benzene", "leukemia" and "adverse health effects". This search was complemented by reviewing the reference lists from extant literature reviews and criteria documents on benzene. Published studies were characterized according to the type of industry studied and design, exposure assessment, disease classification, and control for confounding variables. Study design consisted of either cohort studies or case-control studies, which were further categorized into population-based and nested case-control studies. Disease classification considered the source of diagnostic information, whether there was clinical confirmation from medical records or histopathological, morphological and/or cytogenetic reviews, and as to whether the International Classification of Diseases (ICD) or the French-American-British (FAB) schemes were used (no studies used the Revised European-American Lymphoma (REAL) classification scheme). Nine cohort and 13 case-control studies met inclusion criteria for this review. High and significant acute myeloid leukemia risks with positive dose response relationships were identified across study designs, particularly in the "well-conducted" cohort studies and especially in more highly exposed workers in rubber, shoe, and paint industries. Risks for chronic lymphocytic leukemia (CLL) tended to show elevations in nested case-control studies, with possible dose response relationships in at least two of the three studies. However, cohort studies on CLL show no such risks. Data for chronic myeloid leukemia and acute lymphocytic leukemia are sparse and inconclusive.

Mortality updates (1970-1997) of two refinery/petrochemical plant cohorts at Baton Rouge, Louisiana, and Baytown, Texas.

OBJECTIVE: The purpose of this retrospective cohort study is to update mortality experience at refinery/petrochemical plant facilities in Baton Rouge, Louisiana, and Baytown, Texas. METHODS: Standardized mortality ratios (SMRs) were calculated for 1970-1997 based on death rates in the respective states. RESULTS: SMRs are near or below unity for most causes of death. Among elevations, Baton Rouge has an SMR of 2.42 (95% CI = 1.16-4.45) for chronic lymphocytic leukemia, 1.58 (95% CI = 1.17-2.08) for hypertension with heart disease, and 1.47 (95% CI = 0.98-2.11) for non-Hodgkin's lymphoma. Baytown has an SMR of 2.13 (95% CI = 1.10-3.73) for acute nonlymphocytic leukemia (ANLL) and 3.11 (95% CI = 1.01-7.26) for unspecified brain/spinal cord neoplasms. The above findings pertain to pre-1950 hires and exhibit no apparent job-related patterns. Both cohorts have approximately twofold increases in mesothelioma deaths, similar to the last update, with most decedents having held maintenance jobs. CONCLUSIONS: Periodic examination of mortality patterns has an important role in assessing overall employee health status and identifying potential areas of increased risk. Mortality surveillance will continue to monitor these outcomes among more recent workers.

An analysis of the risk of B-lymphocyte malignancies in industrial cohorts.

Among numerous studies of occupational groups with varied chemical exposures (e.g., farmers, petroleum workers, and rubber workers), some have reported excess risk for non-Hodgkin's lymphoma (NHL), multiple myeloma, and other cancers of the B-lymphocyte cell line. While not conclusive, these studies raise questions about the effects of chemical exposures on the lymphocytic versus myeloid cell lines. Almost 70 occupational cohort studies were identified that addressed B-cell cancer risks in 9 major industrial categories, in order to look for common patterns across industries. This effort was substantially limited by the inconsistent nature of lymphohematopoietic (LH) classification schemes across studies and over time, and the relative paucity of B-cell-specific results in studies for any given industry. Taking these limitations into consideration, a descriptive, graphical analysis suggested a pattern of B-cell cancer elevations in the rubber and "general chemical" industries, but no consistent patterns in petroleum production/distribution or petrochemical production. The limited data sources, which lack detail about differences in hazard and exposure for different types of products/chemicals, did not allow a comprehensive look at possible common exposures associated with B-cell cancer elevations across industries. This study suggests that evaluation of possible associations between specific chemical exposures and B-cell malignancies would require additional studies with clear and common definitions of B-cell outcomes. The article concludes by giving an example of a possible common framework for categorizing NHL, the diseases for which most classification issues arise.