Workplace measurements by the U.S. Occupational Safety and Health Administration since 1979: Descriptive analysis and potential uses for exposure assessment.

This letter summarizes modifications to the results presented in Lavoué et al. (2012): Lavoué, J., Burstyn, I.,Friesen, M. (2012) Workplace Measurements by the US Occupational Safety and Health Administration since1979: Descriptive Analysis and Potential Uses for Exposure Assessment. Annals of occupational hygiene57(1):77­97. Although several results were altered, the conclusions were not affected by the changes.

Workplace measurements by the US Occupational Safety and Health Administration since 1979: descriptive analysis and potential uses for exposure assessment.

BACKGROUND: Inspectors from the US Occupational Safety and Health Administration (OSHA) have been collecting industrial hygiene samples since 1972 to verify compliance with Permissible Exposure Limits. Starting in 1979, these measurements were computerized into the Integrated Management Information System (IMIS). In 2010, a dataset of over 1 million personal sample results analysed at OSHA's central laboratory in Salt Lake City [Chemical Exposure Health Data (CEHD)], only partially overlapping the IMIS database, was placed into public domain via the internet. We undertook this study to inform potential users about the relationship between this newly available OSHA data and IMIS and to offer insight about the opportunities and challenges associated with the use of OSHA measurement data for occupational exposure assessment. METHODS: We conducted a literature review of previous uses of IMIS in occupational health research and performed a descriptive analysis of the data recently made available and compared them to the IMIS database for lead, the most frequently sampled agent. RESULTS: The literature review yielded 29 studies reporting use of IMIS data, but none using the CEHD data. Most studies focused on a single contaminant, with silica and lead being most frequently analysed. Sixteen studies addressed potential bias in IMIS, mostly by examining the association between exposure levels and ancillary information. Although no biases of appreciable magnitude were consistently reported across studies and agents, these assessments may have been obscured by selective under-reporting of non-detectable measurements. The CEHD data comprised 1 450 836 records from 1984 to 2009, not counting analytical blanks and erroneous records. Seventy eight agents with >1000 personal samples yielded 1 037 367 records. Unlike IMIS, which contain administrative information (company size, job description), ancillary information in the CEHD data is mostly analytical. When the IMIS and CEHD measurements of lead were merged, 23 033 (39.2%) records were in common to both IMIS and CEHD datasets, 10 681 (18.2%) records were only in IMIS, and 25 012 (42.6%) records were only in the CEHD database. While IMIS-only records represent data analysed in other laboratories, CEHD-only records suggest partial reporting of sampling results by OSHA inspectors into IMIS. For lead, the percentage of non-detects in the CEHD-only data was 71% compared to 42% and 46% in the both-IMIS-CEHD and IMIS-only datasets, respectively, suggesting differential under-reporting of non-detects in IMIS. CONCLUSIONS: IMIS and the CEHD datasets represent the biggest source of multi-industry exposure data in the USA and should be considered as a valuable source of information for occupational exposure assessment. The lack of empirical data on biases, adequate interpretation of non-detects in OSHA data, complicated by suspected differential under-reporting, remain the principal challenges to the valid estimation of average exposure conditions. We advocate additional comparisons between IMIS and CEHD data and discuss analytical strategies that may play a key role in meeting these challenges.

Mental health in Alberta grain farmers using pesticides over many years.

BACKGROUND: Exposure to organophosphates and certain other pesticides has been related to symptoms of mental ill-health. There is particular interest in whether exposure over many years may result in chronic ill-health. AIMS: To relate lifetime history of pesticide exposure to symptoms and medical records of mental ill-health in elderly grain farmers in Alberta. METHODS: Two populations of grain farmers were identified for study: cohort A (n = 5986), members of an Alberta farm organization in 1983; cohort B (n = 4781), grain farmers registered with the provincial department of agriculture. In 2002-03 both groups completed a questionnaire on lifetime history of pesticide use, physician diagnosed disease and recent neuropsychological symptoms. Durations of exposure to seven pesticide components were calculated and a factor score extracted from responses to the symptom questionnaire. For a sub-cohort surviving to 2009 medical records for mental ill-health were identified. Records and symptom scores were related to pesticide exposures allowing for confounding. RESULTS: From cohort A, 1348 and cohort B, 1078 were alive and interviewed (median age 63 years; median duration in farming 40 years): 1371 were linked to the medical records database. Mental ill-health symptom scores were related to duration of exposure to phenoxy compounds (but not to other pesticides) and to mental ill-health in medical records. Those with mental ill-health in hospital discharge records were more likely to have been exposed to phenoxy compounds for ≥35 years. CONCLUSIONS: The relationship of long-term exposure to phenoxy herbicides and neuropsychiatric symptoms was unexpected but not explained by measured confounders.

Bayesian modelling of lung cancer risk and bitumen fume exposure adjusted for unmeasured confounding by smoking.

OBJECTIVES: Residual confounding can be present in epidemiological studies because information on confounding factors was not collected. A Bayesian framework, which has the advantage over frequentist methods that the uncertainty in the association between the confounding factor and exposure and disease can be reflected in the credible intervals of the risk parameter, is proposed to assess the magnitude and direction of this bias. METHODS: To illustrate this method, bias from smoking as an unmeasured confounder in a cohort study of lung cancer risk in the European asphalt industry was assessed. A Poisson disease model was specified to assess lung cancer risk associated with career average, cumulative and lagged bitumen fume exposure. Prior distributions for the exposure strata, as well as for other covariates, were specified as uninformative normal distributions. The priors on smoking habits were specified as Dirichlet distributions based on smoking prevalence estimates available for a sub-cohort and assumptions about precision of these estimates. RESULTS: Median bias in this example was estimated at 13%, and suggested an attenuating effect on the original exposure-disease associations. Nonetheless, the results still implied an increased lung cancer risk, especially for average exposure. CONCLUSIONS: This Bayesian framework provides a method to assess the bias from an unmeasured confounding factor taking into account the uncertainty surrounding the estimate and from random sampling error. Specifically for this example, the bias arising from unmeasured smoking history in this asphalt workers' cohort is unlikely to explain the increased lung cancer risk associated with average bitumen fume exposure found in the original study.

Exposure to inhalable dust and its cyclohexane soluble fraction since the 1970s in the rubber manufacturing industry in the European Union.

OBJECTIVES: As exposures to airborne particulates in the European rubber industry might still be causing genotoxic risks, it is important to assess trends in levels of inhalable dust and its cyclohexane soluble fraction (CSF) between the 1970s and 2003. METHODS: 13 380 inhalable and 816 respirable dust and 5657 CSF measurements, collected within the framework of the European Union Concerted Action EXASRUB, were analysed. Hierarchical mixed effects models were applied to assess exposure trends, taking into account between-factory, between-worker/location and day-to-day variances. RESULTS: Geometric mean levels of inhalable dust and CSF exposure changed by -4% (range -5.8 to +2.9%) and -3% (range -8.6 to 0%) per year, respectively. Significant reductions in inhalable dust concentrations were found in all countries for handling of crude materials and mixing and milling (-7% to -4% per year), as well as for miscellaneous workers (-11% to -5% per year), while significant CSF exposure reductions were found in curing (-8.6% per year) and maintenance and engineering departments (-5.4% per year). CONCLUSION: These analyses suggest that on average exposure levels of inhalable dust and its CSF in the European rubber manufacturing industry have steadily declined. Most likely genotoxic risks have also lessened over time since exposure levels have decreased and the most toxic chemicals have been replaced. In addition to differences in exposure reductions and levels among various stages of the production process, large differences across countries were noted. These patterns should be taken into account in retrospective assessment of exposure for epidemiological studies assessing cancer risk in the rubber industry.

Occupational exposure to NDMA and NMor in the European rubber industry.

Many nitrosamines are suspected of being human carcinogens, with the highest concentrations in the environment being measured in the rubber industry. Time trends of personal exposure to N-nitrosodimethylamine (NDMA) and to N-nitrosomorpholine (NMor) during the past two decades in the German rubber industry were analysed and compared with cross-sectional studies in the same period in the Netherlands, Poland, the UK and Sweden. In the majority of the surveyed departments exposures reduced over time, but considerable heterogeneity was present between departments and sectors. Significant reductions were primarily found in curing and post-treating departments and ranged from -3% year(-1) to -19% year(-1). In contrast, NDMA levels increased (+13% year(-1)) in maintenance and engineering in the tyres industry. Average NDMA-levels in general rubber goods (GRG) and NMor-levels in tyre production in Germany did not decrease significantly in the past two decades, whereas NDMA-levels in tyre production (-10% year(-1)) and NMor-levels in GRG (-7% year(-1)) declined significantly after the introduction of an exposure limit for total nitrosamines in Germany in 1988. Confidence intervals of average exposures in other studied countries largely overlap trends observed in Germany. Exposure to N-nitrosamines decreased on average two-to-five fold in the German rubber industry with comparable concentration levels in other European countries. Although average levels are well below the current limits exposure has not been eliminated, and incidental high exposures do still occur.

Adverse reproductive outcomes among male painters with occupational exposure to organic solvents.

OBJECTIVES: To assess the risks of reproductive disorders and birth defects in offspring of male painters with exposure to organic solvents, and to determine the shape of the dose-response relationship. METHODS: Random samples of painters and carpenters were drawn from workers affiliated with the Dutch Trade Union for Construction Workers, the Netherlands, 2001. Information on reproductive outcomes, occupational exposures, and lifestyle habits was retrospectively obtained through self-administered questionnaires filled in by 398 painters exposed to organic solvents in paints, thinners, and cleansers in the period of three months before the last pregnancy, and 302 carpenters with little or no exposure to solvents. A statistical model was used to estimate quantitative exposure measures. RESULTS: Workers employed as painters at three months before pregnancy had an increased risk (odds ratio 6.2, 95% CI 1.4 to 27.9) of congenital malformations in offspring compared to carpenters. There was a positive exposure-response trend with increasing exposure to organic solvents based on quantitative model predicted exposure estimates using toluene as a marker. There was some indication of an increased risk of functional developmental disorders in offspring among painters with intermediate and high model predicted exposure. The risk of low birth weight children seemed to be slightly increased among painters as well. Results for other reproductive outcomes (time to pregnancy, spontaneous abortion, and preterm birth) did not show increased risks. CONCLUSION: This study showed a positive association between paternal occupational exposure to organic solvents and congenital malformations in offspring. However, the small numbers of cases, especially when examining different exposure levels, as well as the self-reported nature of exposure and outcome variables, may hamper interpretation of the results.

Respiratory symptoms and airflow limitation in asphalt workers.

BACKGROUND: Asphalt workers are exposed to bitumen fume and vapour, and to exhaust from engines and passing traffic. AIMS: To assess the occurrence of respiratory symptoms and signs of airflow limitations in a group of asphalt workers. METHODS: All 64 asphalt workers and a reference group of 195 outdoor construction workers from the same company participated in a cross-sectional study. Spirometric tests and a questionnaire on respiratory symptoms and smoking habits were administered. Respiratory symptoms and lung function were adjusted for age and smoking. RESULTS: The FEV1/FVC% ratio was significantly lower in the asphalt workers than in the referents. Symptoms of eye irritation, chest tightness, shortness of breath on exertion, chest wheezing, physician diagnosed asthma, and chronic obstructive pulmonary disease (COPD) were all significantly more prevalent among the asphalt workers. CONCLUSION: In asphalt workers there is an increased risk of respiratory symptoms, lung function decline, and COPD compared to other construction workers.

Validity of empirical models of exposure in asphalt paving.

AIMS: To investigate the validity of empirical models of exposure to bitumen fume and benzo(a)pyrene, developed for a historical cohort study of asphalt paving in Western Europe. METHODS: Validity was evaluated using data from the USA, Italy, and Germany not used to develop the original models. Correlation between observed and predicted exposures was examined. Bias and precision were estimated. RESULTS: Models were imprecise. Furthermore, predicted bitumen fume exposures tended to be lower (-70%) than concentrations found during paving in the USA. This apparent bias might be attributed to differences between Western European and USA paving practices. Evaluation of the validity of the benzo(a)pyrene exposure model revealed a similar to expected effect of re-paving and a larger than expected effect of tar use. Overall, benzo(a)pyrene models underestimated exposures by 51%. CONCLUSIONS: Possible bias as a result of underestimation of the impact of coal tar on benzo(a)pyrene exposure levels must be explored in sensitivity analysis of the exposure-response relation. Validation of the models, albeit limited, increased our confidence in their applicability to exposure assessment in the historical cohort study of cancer risk among asphalt workers.

Literature review of levels and determinants of exposure to potential carcinogens and other agents in the road construction industry.

Workers in the road construction industry include asphalt plant, ground construction, and road paving workers. These individuals can be exposed to a wide range of potentially hazardous substances. A summary of levels of exposure to different substances measured during road construction is presented. In modern road paving, workers typically are exposed to 0.1 to 2 mg/m3 of bitumen fume, which includes 10 to 200 ng/m3 of benzo(a)pyrene. Sampling strategies and analytical methods employed in each reviewed survey are described briefly. The published reports provide some insight into the identity of factors that influence exposure to bitumen among road construction workers: type of work performed, meteorological conditions, temperature of paved asphalt. However, there is a lack of (a) comprehensive and well-designed studies that evaluate determinants of exposure to bitumen in road construction, and (b) standard methods for bitumen sampling and analysis. Information on determinants of other exposures in road construction is either absent or limited. It is concluded that data available through published reports have limited value in assessing historical exposure levels in the road construction industry.

Statistical modelling of the determinants of historical exposure to bitumen and polycyclic aromatic hydrocarbons among paving workers.

INTRODUCTION: An industrial hygiene database has been constructed for the exposure assessment in a study of cancer risk among asphalt workers. AIM: To create models of bitumen and polycyclic aromatic hydrocarbons (PAH) exposure intensity among paving workers. METHODS: Individual exposure measurements from pavers (N = 1581) were collected from 8 countries. Correlation patterns between exposure measures were examined and factors affecting exposure were identified using statistical modelling. RESULTS: Inhalable dust appeared to be a good proxy of bitumen fume exposure. Bitumen fume and vapour levels were not correlated. Benzo(a)pyrene level appeared to be a good indicator of PAH exposure. All exposures steadily declined over the last 20 years. Mastic laying, re-paving, surface dressing, oil gravel paving and asphalt temperature were significant determinants of bitumen exposure. Coal tar use dictated PAH exposure levels. DISCUSSION: Bitumen fume, vapour and PAH have different determinants of exposure. For paving workers, exposure intensity can be assessed on the basis of time period and production characteristics.

Designing an international industrial hygiene database of exposures among workers in the asphalt industry.

OBJECTIVES: The objective of this project was to construct a database of exposure measurements which would be used to retrospectively assess the intensity of various exposures in an epidemiological study of cancer risk among asphalt workers. METHODS: The database was developed as a stand-alone Microsoft Access 2.0 application, which could work in each of the national centres. Exposure data included in the database comprised measurements of exposure levels, plus supplementary information on production characteristics which was analogous to that used to describe companies enrolled in the study. RESULTS AND DISCUSSION: The database has been successfully implemented in eight countries, demonstrating the flexibility and data security features adequate to the task. The database allowed retrieval and consistent coding of 38 data sets of which 34 have never been described in peer-reviewed scientific literature. We were able to collect most of the data intended. As of February 1999 the database consisted of 2007 sets of measurements from persons or locations. The measurements appeared to be free from any obvious bias. CONCLUSIONS: The methodology embodied in the creation of the database can be usefully employed to develop exposure assessment tools in epidemiological studies.