Assessing contact dermatitis risk among Manitoba workers in the Manitoba Occupational Disease Surveillance System.

INTRODUCTION: This exploratory study aimed to assess contact dermatitis (CD) risk among workers using the Manitoba Occupational Disease Surveillance System (MODSS). METHODS: The MODSS linked accepted time-loss claims from the Workers' Compensation Board of Manitoba (2006-2019), with administrative health data from medical and hospital records (1996-2020). CD risk by occupation and industry (hazard ratio, 95% confidence intervals) was estimated using Cox proportional hazard models, adjusted for age and stratified by sex. RESULTS: Increased risk of new onset CD was observed among some occupations and industries with known skin irritants and allergens. Some occupations with known increased risks of CD remained elevated when removing the accepted WCB cases was performed, suggesting that all CD cases in these occupations may not show up in WCB statistics. Increased risk was also observed for occupations and industries with unknown exposures related to CD, whereas some groups known to be at risk of CD were not observed to have elevated risks in this cohort. DISCUSSION: The MODSS successfully identified some occupations and industries known to be at high risk of occupational CD, but not others. Some occupations not typically associated with work-related CD were also identified, which warrants further investigation.

Lifetime excess absolute risk for lung cancer due to exposure to radon: results of the pooled uranium miners cohort study PUMA.

The Pooled Uranium Miners Analysis (PUMA) study is the largest uranium miners cohort with 119,709 miners, 4.3 million person-years at risk and 7754 lung cancer deaths. Excess relative rate (ERR) estimates for lung cancer mortality per unit of cumulative exposure to radon progeny in working level months (WLM) based on the PUMA study have been reported. The ERR/WLM was modified by attained age, time since exposure or age at exposure, and exposure rate. This pattern was found for the full PUMA cohort and the 1960 + sub-cohort, i.e., miners hired in 1960 or later with chronic low radon exposures and exposure rates. The aim of the present paper is to calculate the lifetime excess absolute risk (LEAR) of lung cancer mortality per WLM using the PUMA risk models, as well as risk models derived in previously published smaller uranium miner studies, some of which are included in PUMA. The same methods were applied for all risk models, i.e., relative risk projection up to <95 years of age, an exposure scenario of 2 WLM per year from age 18-64 years, and baseline mortality rates representing a mixed Euro-American-Asian population. Depending upon the choice of model, the estimated LEAR per WLM are 5.38 × 10-4 or 5.57 × 10-4 in the full PUMA cohort and 7.50 × 10-4 or 7.66 × 10-4 in the PUMA 1960 + sub-cohort, respectively. The LEAR per WLM estimates derived from risk models reported for previously published uranium miners studies range from 2.5 × 10-4 to 9.2 × 10-4. PUMA strengthens knowledge on the radon-related lung cancer LEAR, a useful way to translate models for policy purposes.

Characterizing occupational radon exposure greater than 100 Bq/m3 in a highly exposed country.

Radon is an established lung carcinogen concentrating in indoor environments with importance for many workers worldwide. However, a systematic assessment of radon levels faced by all workers, not just those with direct uranium or radon exposure, has not previously been completed. The objective of this study was to estimate the prevalence of workers exposed to radon, and the level of exposure (> 100-200 Bq/m3, 200-400 Bq/m3, 400-800 Bq/m3, and > 800 Bq/m3) in a highly exposed country (Canada). Exposures among underground workers were assessed using the CAREX Canada approach. Radon concentrations in indoor workplaces, obtained from two Canadian surveys, were modelled using lognormal distributions. Distributions were then applied to the susceptible indoor worker population to yield the number of exposed workers, by occupation, industry, province, and sex. In total, an estimated 603,000 out of Canada's 18,268,120 workers are exposed to radon in Canada. An estimated52% of exposed workers are women, even though they comprise only 48% of the labour force. The majority (68%) are exposed at a level of > 100-200 Bq/m3. Workers are primarily exposed in educational services, professional, scientific and technical services, and health care and social assistance, but workers in mining, quarrying, and oil and gas extraction have the largest number of exposed workers at high levels (> 800 Bq/m3). Overall, a significant number of workers are exposed to radon, many of whom are not adequately protected by existing guidelines. Radon surveys across multiple industries and occupations are needed to better characterize occupational exposure. These results can be used to identify exposed workers, and to support lung cancer prevention programs within these groups.

Mortality among uranium miners in North America and Europe: the Pooled Uranium Miners Analysis (PUMA).

BACKGROUND: The Pooled Uranium Miners Analysis (PUMA) study draws together information from cohorts of uranium miners from Canada, the Czech Republic, France, Germany and the USA. METHODS: Vital status and cause of death were ascertained and compared with expectations based upon national mortality rates by computing standardized mortality ratios (SMRs) overall and by categories of time since first hire, calendar period of first employment and duration of employment as a miner. RESULTS: There were 51 787 deaths observed among 118 329 male miners [SMR = 1.05; 95% confidence interval (CI): 1.04, 1.06]. The SMR was elevated for all cancers (n = 16 633, SMR = 1.23; 95% CI: 1.21, 1.25), due primarily to excess mortality from cancers of the lung (n = 7756, SMR = 1.90; 95% CI: 1.86, 1.94), liver and gallbladder (n = 549, SMR = 1.15; 95% CI: 1.06, 1.25), larynx (n = 229, SMR = 1.10; 95% CI: 0.97, 1.26), stomach (n = 1058, SMR = 1.08; 95% CI: 1.02, 1.15) and pleura (n = 39, SMR = 1.06; 95% CI: 0.75, 1.44). Lung-cancer SMRs increased with duration of employment, decreased with calendar period and persisted with time since first hire. Among non-malignant causes, the SMR was elevated for external causes (n = 3362, SMR = 1.41; 95% CI: 1.36, 1.46) and respiratory diseases (n = 4508, SMR = 1.32; 95% CI: 1.28, 1.36), most notably silicosis (n = 814, SMR = 13.56; 95% CI: 12.64, 14.52), but not chronic obstructive pulmonary disease (n = 1729, SMR = 0.98; 95% CI: 0.93, 1.02). CONCLUSIONS: Whereas there are important obstacles to the ability to detect adverse effects of occupational exposures via SMR analyses, PUMA provides evidence of excess mortality among uranium miners due to a range of categories of cause of death. The persistent elevation of SMRs with time since first hire as a uranium miner underscores the importance of long-term follow-up of these workers.

Estimating the burden of lung cancer in Canada attributed to occupational radon exposure using a novel exposure assessment method.

OBJECTIVE: Exposure to radon causes lung cancer. The scope and impact of exposure among Canadian workers have not been assessed. Our study estimated occupational radon exposure in Canada and its associated lung cancer burden. METHODS: Exposed workers were identified among the working population during the risk exposure period (1961-2001) using data from the Canadian Census and Labour Force Survey. Exposure levels were assigned based on 12,865 workplace radon measurements for indoor workers and assumed to be 1800 mg/m3 for underground workers. Lung cancer risks were calculated using the Biological Effects of Ionizing Radiation (BEIR) VI exposure-age-concentration model. Population attributable fractions were calculated with Levin's equation and applied to 2011 Canadian lung cancer statistics. RESULTS: Approximately 15.5 million Canadian workers were exposed to radon during the risk exposure period. 79% of exposed workers were exposed to radon levels < 50 Bq/m3 and 4.8% were exposed to levels > 150 Bq/m3. We estimated that 0.8% of lung cancers in Canada were attributable to occupational radon exposure, corresponding to approximately 188 incident lung cancers in 2011. CONCLUSIONS: The lung cancer burden associated with occupational radon exposure in Canada is small, with the greatest burden occurring among those exposed to low levels of radon.

Burden of non-melanoma skin cancer attributable to occupational sun exposure in Canada.

PURPOSE: Outdoor workers are exposed daily to solar ultraviolet radiation, an important contributor in the development of non-melanoma skin cancer. This study aimed to quantify the health burden of non-melanoma skin cancers among outdoor workers in Canada. METHODS: Solar ultraviolet radiation exposure and estimates of exposure levels were applied to employment information from Canada census data to determine the exposed population in the risk exposure period (1961-2001). Risk estimates were drawn from meta-analyses selected based on quality and relevance to the current study. Population-attributable fractions were calculated using Levin's equation and attributable cases were estimated based on incidence data reported by the Canadian Cancer Society. RESULTS: In 2011, 6.31% (4556 cases) of non-melanoma skin cancer cases were estimated to be attributable to occupational exposure to solar ultraviolet radiation. The majority of these cases occurred in men in the agriculture or construction industries. CONCLUSIONS: These estimates of the burden of non-melanoma skin cancer in Canada identify the need for further prevention efforts, particularly in agriculture and construction. Introducing workplace sun safety measures could be an important area for policy development.

Silica exposure in a mining exploration operation.

BACKGROUND: Though there is extensive research on occupational exposure in production mines, there is limited information on exposure during the exploration phase of mining. METHODS: Air samples were collected in a core processing facility in Northern Ontario, Canada. All samples were analyzed for respirable dust (NIOSH 0600) and respirable crystalline silica (NIOSH 7602). Mean exposure levels were estimated and differences in exposure between work areas were investigated. RESULTS: Sixteen personal and nine area air samples were collected. Respirable dust exposure ranged from < LOD to 2.24mg-m-3; respirable silica exposure ranged from < LOD to 0.055mg-m-3. Silica concentrations were higher among workers in the core cutting and core sorting (pulp and reject) areas, as compared to those in the core logging area. CONCLUSIONS: Workers employed in core processing facilities as part of mining exploration activities are exposed to respirable silica; exposure controls may be needed.

Challenges and Opportunities for Occupational Epidemiology in the Twenty-first Century.

PURPOSE OF REVIEW: There are many opportunities and challenges for conducting occupational epidemiologic studies today. In this paper, we summarize the discussion of a symposium held at the Epidemiology in Occupational Health (EPICOH) conference, Chicago 2014, on challenges for occupational epidemiology in the twenty-first century. RECENT FINDINGS: The increasing number of publications and attendance at our conferences suggests that worldwide interest in occupational epidemiology has been growing. There are clearly abundant opportunities for new research in occupational epidemiology. Areas ripe for further work include developing improved methods for exposure assessment, statistical analysis, studying migrant workers and other vulnerable populations, the use of biomarkers, and new hazards. Several major challenges are also discussed such as the rapidly changing nature and location of work, lack of funding, and political/legal conflicts. As long as work exists there will be occupational diseases that demand our attention, and a need for epidemiologic studies designed to characterize these risks and to support the development of preventive strategies. Despite the challenges and given the important past contribution in this field, we are optimistic about the importance and continued vitality of the research field of occupational epidemiology.

Characteristics of work-related fatal and hospitalised injuries not captured in workers' compensation data.

OBJECTIVES: (1) To identify work-related fatal and non-fatal hospitalised injuries using multiple data sources, (2) to compare case-ascertainment from external data sources with accepted workers' compensation claims and (3) to investigate the characteristics of work-related fatal and hospitalised injuries not captured by workers' compensation. METHODS: Work-related fatal injuries were ascertained from vital statistics, coroners and hospital discharge databases using payment and diagnosis codes and injury and work descriptions; and work-related (non-fatal) injuries were ascertained from the hospital discharge database using admission, diagnosis and payment codes. Injuries for British Columbia residents aged 15-64 years from 1991 to 2009 ascertained from the above external data sources were compared to accepted workers' compensation claims using per cent captured, validity analyses and logistic regression. RESULTS: The majority of work-related fatal injuries identified in the coroners data (83%) and the majority of work-related hospitalised injuries (95%) were captured as an accepted workers' compensation claim. A work-related coroner report was a positive predictor (88%), and the responsibility of payment field in the hospital discharge record a sensitive indicator (94%), for a workers' compensation claim. Injuries not captured by workers' compensation were associated with female gender, type of work (natural resources and other unspecified work) and injury diagnosis (eg, airway-related, dislocations and undetermined/unknown injury). CONCLUSIONS: Some work-related injuries captured by external data sources were not found in workers' compensation data in British Columbia. This may be the result of capturing injuries or workers that are ineligible for workers' compensation, or the result of injuries that go unreported to the compensation system. Hospital discharge records and coroner reports may provide opportunities to identify workers (or family members) with an unreported work-related injury and to provide them with information for submitting a workers' compensation claim.

Population-based surveillance of asthma among workers in British Columbia, Canada.

INTRODUCTION: Population-based health databases were used for the surveillance of asthma among workers in British Columbia for the period 1999 to 2003. The purpose was to identify high-risk groups of workers with asthma for further investigation, education and prevention. METHODS: Workers were identified using an employer-paid health premium field in the provincial health registry, and were linked to their physician visit, hospitalization, workers' compensation and pharmaceutical records; asthma cases were defined by the presence of an asthma diagnosis (International Classification of Diseases [ICD]-9-493) in these health records. Workers were assigned to an ''at-risk'' exposure group based on their industry of employment. RESULTS: For males, significantly higher asthma rates were observed for workers in the Utilities, Transport/Warehousing, Wood and Paper Manufacturing (Sawmills), Health Care/Social Assistance and Education industries. For females, significantly higher rates were found for those working in the Waste Management/Remediation and Health Care/Social Assistance industries. CONCLUSION: The data confirm a high prevalence of active asthma in the working population of British Columbia, and in particular, higher rates among females compared to males and in industries with known respiratory sensitizers such as dust and chemical exposures.

Priority issues in occupational cancer research: Ontario stakeholder perspectives.

INTRODUCTION: Workers are potentially exposed to known and suspected carcinogens in the workplace, many of which have not been fully evaluated. Despite persistent need, research on occupational cancer appears to have declined in recent decades. The formation of the Occupational Cancer Research Centre (OCRC) is an effort to counter this downward trend in Ontario. The OCRC conducted a survey of the broad stakeholder community to learn about priority issues on occupational cancer research. METHODS: The OCRC received 177 responses to its survey from academic, health care, policy, industry, and labour-affiliated stakeholders. Responses were analyzed based on workplace exposures, at-risk occupations and cancers by organ system, stratified by respondents' occupational role. DISCUSSION: Priority issues identified included workplace exposures such as chemicals, respirable dusts and fibres (e.g. asbestos), radiation (e.g. electromagnetic fields), pesticides, and shift work; and occupations such as miners, construction workers, and health care workers. Insufficient funding and a lack of exposure data were identified as the central barriers to conducting occupational cancer research. CONCLUSION: The results of this survey underscore the great need for occupational cancer research in Ontario and beyond. They will be very useful as the OCRC develops its research agenda.

Early changes in respiratory health in trades' apprentices and physician visits for respiratory illnesses later in life.

OBJECTIVES: An inception cohort of trades' apprentices had rapid declines in lung function (forced expiratory volume in 1 s (FEV(1))) and rapid increases in bronchial responsiveness ( upward arrowBR) over the first 2 years of employment. We used physician visit data to assess respiratory health over the following 13 years. METHODS: Construction painter, electrician, insulator and machinist apprentices beginning at a British Columbia trade school in 1988 were invited to participate and were followed up 2 years later. Subjects were linked to provincial medical databases to examine physician visits for asthma and other respiratory illnesses for the 13 years following. Multivariable models with rapid decline in FEV(1) and rapid increase in BR from years 1 to 3 were constructed. Respiratory symptoms were also examined as predictors of visit rates and meeting a case definition (for asthma or other respiratory illness). RESULTS: The cohort included 281 apprentices (97% are men). Sixteen subjects met the asthma case definition (>or=2 visits coded as asthma in 1 year) and 20 met the other respiratory illness case definition (>or=3 visits for bronchitis, emphysema, respiratory symptoms in 1 year). In models controlling for demographic factors and smoking, subjects with bronchitis symptoms at baseline were more likely to develop other respiratory illness during follow-up (RR 4.4, 95% CI 1.6 to 11.9). Apprentices who developed asthma symptoms over the first 2 years were approximately six times more likely to become asthma cases (95% CI 1.9 to 18.8). Those with a rapid increase in BR were at increased risk of becoming asthma cases (RR 5.5, 95% CI 1.9 to 16.1), as well as having higher asthma visit rates (RR 6.5). Subjects with rapid decline in FEV(1) were 3.2 times more likely to become asthma cases (95% CI 0.8 to 12.1). CONCLUSIONS: Changes in respiratory health early in adulthood, especially increased BR, are associated with respiratory physician visits. These findings are important for workplace screening and prevention and also suggest that physician visit databases are promising research tools in respiratory epidemiology.

Population-based asbestosis surveillance in British Columbia.

OBJECTIVES: To investigate the use of multiple health data sources for population-based asbestosis surveillance in British Columbia, Canada. METHODS: Provincial health insurance registration records, workers' compensation records, hospitalisation records, and outpatient medical service records were linked using individual-specific study identifiers. The study population was restricted to individuals > or = 15 years of age living in the province during 1992-2004. RESULTS: 1170 new asbestosis cases were identified from 1992 to 2004 for an overall incidence rate of 2.82 (men: 5.48, women: 0.23) per 100,000 population; 96% of cases were male and average (SD) age was 69 (10) years. Although the annual number of new cases increased by 30% during the surveillance period (beta = 2.36, p = 0.019), the observed increase in annual incidence rates was not significant (beta = 0.02, p = 0.398). Workers' compensation, hospitalisation and outpatient databases identified 23%, 48% and 50% of the total new cases, respectively. Of the new cases, 82% were identified through single data sources, 10% were only recorded in the workers' compensation records, and 36% only in each of the hospitalisation and outpatient records. 84% of hospitalisation cases and 83% of outpatient cases were not included in the workers' compensation records. The three data sources showed different temporal trends in the annual number of new cases and annual incidence rates. CONCLUSIONS: Single data sources were not sufficient to identify all new cases, thus leading to serious underestimations of the true burden of asbestosis. Integrating multiple health data sources could provide a more complete picture in population-based surveillance of asbestosis and other occupational diseases.

A retrospective assessment of occupational noise exposures for a longitudinal epidemiological study.

OBJECTIVES: Chronic exposure to high levels of noise may be associated with increased risk of cardiovascular disease. We therefore undertook a quantitative retrospective exposure assessment using predictive statistical modelling to estimate historical exposures to noise among a cohort of 27,499 sawmill workers as part of an investigation of acute myocardial infarction mortality. METHODS: Noise exposure data were gathered from research, industry and regulatory sources. An exposure data matrix was defined and exposure level estimated for job title/mill/time period combinations utilising regression analysis to model determinants of noise exposure. Cumulative exposure and duration of exposure metrics were calculated for each subject. These were merged with work history data, and exposure-response associations were tested in subsequent epidemiological studies, reported elsewhere. RESULTS: Over 14,000 noise measurements were obtained from British Columbia sawmills. A subset, comprising 1901 full-shift dosimetry measurements from cohort mills was used in producing a predictive model (R(2) = 0.51). The model was then used to estimate noise exposures for 3809 "cells" of an exposure data matrix representing 81 jobs at 14 mills over several decades. Various exposure metrics were then calculated for subjects; mean cumulative exposure was 101 dBA*year. Mean durations of employment in jobs with exposure above thresholds of 85, 90 and 95 dBA, were 9.9, 7.0 and 3.2 years, respectively. CONCLUSIONS: The utility of predictive statistical modelling for occupational noise exposure was demonstrated. The model required input data that were relatively easily obtained, even retrospectively. Remaining issues include adequate handling of the use of hearing protectors that likely bias exposure estimation.

Hypertension in noise-exposed sawmill workers: a cohort study.

OBJECTIVE: To investigate the hypothesised association between exposure to high levels of noise and risk of hypertension using quantitative exposure assessment and administrative health data. METHODS: This study followed a cohort of 10 872 sawmill workers in British Columbia from 1991 to 1998. Subjects were linked with provincial hospital discharge, outpatient and vital status databases. Cases were males who died, had at least one hospital admission, or who had three doctor visits within 70 days, for hypertension (ICD-9 codes 401-405). We used four exposure metrics: cumulative exposure, and duration of exposure above thresholds of 85 dBA, 90 dBA and 95 dBA. Relative risks were estimated using Poisson regression with the low-exposure group as controls and adjusting for age, ethnicity and calendar period. RESULTS: 828 cases were identified. The results showed a monotonic increase in hypertension incidence with cumulative exposure. The risk in the highest exposed population was 32% higher than baseline. Similar results were found using duration of exposure metrics. The highest relative risk was 1.5 in workers exposed for more than 30 years at 85 dBA. Exposure-response trends were statistically significant. CONCLUSIONS: The risk of hypertension was positively associated with noise exposure above 85 dB.

From expert-based to quantitative retrospective exposure assessment at a Soderberg aluminum smelter.

OBJECTIVES: Expert judgement of exposure levels is often only poorly or moderately correlated with directly measured levels. For a follow-up of a historical cohort study at a Söderberg aluminum smelter we updated an expert-based semiquantitative job exposure matrix of coal tar pitch volatiles (CTPV) to quantitative estimates of CTPV and benzo(a)pyrene (BaP). METHODS: Mixed effects models to predict exposure for potroom operation and maintenance jobs were constructed from personal CTPV and BaP measurements. Mean exposures of jobs in non-potroom locations were directly calculated when measurements were available. Exposure estimates for jobs/time periods with no measurements were based on proportion of time spent in exposed areas compared to jobs where exposure was modeled or measured. For pre-1977, the original expert exposure assignments were calibrated using the updated 1977 estimates. RESULTS: The rate of change in exposure levels varied by time period and was accounted for in mixed models with a linear spline time trend. Other variables significant in the models were job, potroom group and season as fixed effects, and worker as a random effect. The models for potroom operations explained 45 and 27% of the variability in the CTPV and BaP measurements, respectively. The models for maintenance jobs explained 40 and 19% of the variability in the CTPV and BaP measurements, respectively. For 1977-2000 model estimates, direct calculation of means and extrapolation from modeled/measured exposures accounted for 57, 6 and 37% of the exposed person-years, respectively. CONCLUSIONS: The above methodology maximized the use of exposure measurements and largely replaced the original expert-based estimates. Finer discrimination between exposure levels was possible with the updated exposure assessment. The new estimates are expected to reduce exposure misclassification and help better assess the exposure-response relationships.

Predicting historical dust and wood dust exposure in sawmills: model development and validation.

Nonspecific dust measurements are used as a surrogate for wood dust exposure in sawmills. However, the wood dust component of dust has been found to vary by job and work area. Thus, the use of nonspecific dust exposure levels in epidemiologic studies may introduce exposure misclassification when assessing wood-related health effects. To improve exposure assessment in a retrospective cohort of 28,000 sawmill workers, we developed and evaluated the validity of two empirical models of exposure: one for nonspecific dust and one for wood dust. The dust model was constructed using 1,395 dust measurements collected in 13 sawmills for research or regulatory purposes from 1981 to 1997. Inter-sampler conversion factors were used to obtain inhalable dust equivalents if necessary. The wood dust model was constructed after applying adjustment factors to subtract nonwood components of the dust from the original measurements. The validity of the two models was tested against measurements (n = 213) from a technologically similar mill that was not part of the cohort study. The proportions of variability explained by the dust and wood dust models were 35% and 54%, respectively. When tested against the validation mill, the biases in the dust model were -33% for outdoor jobs and 2% for indoor jobs. The biases in the wood dust model were 2% for outdoor jobs and -3% for indoor jobs. Strong correlations were observed between the predicted and observed geometric means of jobs (0.79 and 0.70 for the dust model and wood dust model, respectively). Testing the validity of predictive models examines the generalizability of the models. The low overall bias, especially in the wood-specific model, increases our confidence in the use of these models for all sawmills to assess both nonspecific particulate and wood-related health effects in the historical cohort study.

Validation of a semi-quantitative job exposure matrix at a Söderberg aluminum smelter.

OBJECTIVES: We tested the validity of a job exposure matrix (JEM) for coal tar pitch volatiles (CTPV) at a Söderberg aluminum smelter. The JEM had been developed by a committee of company hygienists and union representatives for an earlier study of cancer incidence and mortality. Our aim was to test the validity and reliability of the expert-based assignments. METHODS: Personal CTPV exposure measurements (n = 1879) overlapped 11 yr of the JEM. The arithmetic mean was calculated for 35 job/time period combinations (35% of the exposed work history), categorized using the original exposure intervals, and compared with the expert-based assignments. RESULTS: The expert-based and the measurement-based exposure assignments were only moderately correlated (Spearman's rho = 0.42; weighted kappa = 0.39, CI 0.10-0.69). Only 40% of the expert-based medium category assignments were correctly assigned, with better agreement in the low (84%) and high (100%) categories. Pot operation jobs exhibited better agreement (rho = 0.60) than the maintenance and pot shell repair jobs (rho = 0.25). The mid-point value of the medium category was overestimated by 0.3 mg/m(3). CONCLUSIONS: The expert-based exposure assignments may be improved by better characterizing the transitions between exposure categories, by accounting for exposure differences between pot lines and by re-examining the category mid-point values used in calculating the cumulative exposure. Lack of historical exposure measurements often requires reliance on expert knowledge to assess exposure levels. Validating the experts' estimates against available exposure measurements may help to identify weaknesses in the exposure assessment where improvements may be possible, as was shown here.