Comparison of industrial hygienists' exposure evaluations for an epidemiologic study

The design of a matrix linking work situations to chemical health risk at the workplace

In France, laws require each company to draw up an inventory of the risks that may threaten employees' health in order to prioritize the preventive actions to be implemented. Focusing on chemical risk, databases on hazards or exposures are widely available but they lack information regarding chemical risks resulting from combining the hazards of chemicals with their conditions of use, thus generating exposures. Our objective is to build a matrix of French work situations associated with their chemical risk. Eighty-eight work situations were collected from reports written by professionals from the French public health insurance service. Each work situation is defined by descriptive parameters of the task, the exposure, and the hazard. According to an expert elicitation method (Delphi, n = 21 experts), each work situation was assessed and a chemical risk score defined, taking into account all the descriptive exposure and hazard parameters. Chemical risk scores were expressed as a range of values from 0 to 100, with the size of the range chosen by the experts themselves according to their uncertainty. The experts' assessments were merged to assign one risk score for each work situation, variability, and confidence. The results showed that 50% of the work situations had a risk score between 40 and 60. The average variability and confidence were around 15% and 82%, respectively. This work situation matrix constructed from French data can be used by occupational safety and health managers that have similar work situations in their company (Western European industrial sector). In this context, it may be useful to easily determine the level of risks for similar tasks and prioritize those that are most risky. Moreover, it could be used to compare and define the differences between a risk assessment performed by "expertise" and another defined by a software.

Between-User Reliability of Tier 1 Exposure Assessment Tools Used Under REACH

When applying simple screening (Tier 1) tools to estimate exposure to chemicals in a given exposure situation under the Registration, Evaluation, Authorisation and restriction of CHemicals Regulation 2006 (REACH), users must select from several possible input parameters. Previous studies have suggested that results from exposure assessments using expert judgement and from the use of modelling tools can vary considerably between assessors. This study aimed to investigate the between-user reliability of Tier 1 tools. A remote-completion exercise and in person workshop were used to identify and evaluate tool parameters and factors such as user demographics that may be potentially associated with between-user variability. Participants (N = 146) generated dermal and inhalation exposure estimates (N = 4066) from specified workplace descriptions ('exposure situations') and Tier 1 tool combinations (N = 20). Interactions between users, tools, and situations were investigated and described. Systematic variation associated with individual users was minor compared with random between-user variation. Although variation was observed between choices made for the majority of input parameters, differing choices of Process Category ('PROC') code/activity descriptor and dustiness level impacted most on the resultant exposure estimates. Exposure estimates ranging over several orders of magnitude were generated for the same exposure situation by different tool users. Such unpredictable between-user variation will reduce consistency within REACH processes and could result in under-estimation or overestimation of exposure, risking worker ill-health or the implementation of unnecessary risk controls, respectively. Implementation of additional support and quality control systems for all tool users is needed to reduce between-assessor variation and so ensure both the protection of worker health and avoidance of unnecessary business risk management expenditure.

Determinants of the accuracy of occupational hygiene expert judgment

An experimental study was performed to determine the applicability and accuracy of occupational hygienist's expert judgment in occupational exposure assessment. The effect of tier 1 model application on improvement of expert judgments were also realized. Hygienists were asked to evaluate inhalation exposure intensity in seven operating units in a tile factory before and after an exposure training session. Participants' judgments were compared to air sampling data in the units; then after relative errors for judgments were calculated. Stepwise regressions were performed to investigate the defining variables. In all situations there were almost a perfect agreement (ICC >0.80) among raters. Correlations between estimated mean exposure and relative percentage error of participants before and after training were significant at 0.01 (correlation coefficients were -0.462 and -0.443, respectively). Results showed that actual concentration and experience resulted in 22.4% prediction variance for expert error as an independent variable. Exposure rating by hygienists was susceptible to error from several sources. Experienced subjects had a better ability to predict the exposures intensity. In lower concentrations, the rating error increased significantly. Leading causes of judgment error should be taken into account in epidemiological studies.

Reliability and validity of expert assessment based on airborne and urinary measures of nickel and chromium exposure in the electroplating industry

The reliability and validity of six experts' exposure ratings were evaluated for 64 nickel-exposed and 72 chromium-exposed workers from six Shanghai electroplating plants based on airborne and urinary nickel and chromium measurements. Three industrial hygienists and three occupational physicians independently ranked the exposure intensity of each metal on an ordinal scale (1-4) for each worker's job in two rounds: the first round was based on responses to an occupational history questionnaire and the second round also included responses to an electroplating industry-specific questionnaire. The Spearman correlation (r(s)) was used to compare each rating's validity to its corresponding subject-specific arithmetic mean of four airborne or four urinary measurements. Reliability was moderately high (weighted kappa range=0.60-0.64). Validity was poor to moderate (r(s)=-0.37-0.46) for both airborne and urinary concentrations of both metals. For airborne nickel concentrations, validity differed by plant. For dichotomized metrics, sensitivity and specificity were higher based on urinary measurements (47-78%) than airborne measurements (16-50%). Few patterns were observed by metal, assessment round, or expert type. These results suggest that, for electroplating exposures, experts can achieve moderately high agreement and (reasonably) distinguish between low and high exposures when reviewing responses to in-depth questionnaires used in population-based case-control studies.

Agreement of experts and non-experts in a desktop exercise evaluating exposure to asthmagens in the cotton and textile, and other industries

In the absence of personal exposure measurements, expert assessment, generally on a case-by-case basis, is often used to estimate exposures. However, the decision processes of individual experts when making assessments are unknown, making it difficult to assess the quality of these assessments or to compare different assessments to each other. We conducted a study in primarily the textile and cotton industries, but also in baking, metal work, and agriculture industries in which we assessed agreement between experts assessing intensity and probability of exposure in the absence of exposure measurements to compare how well their performance compares to agreement of non-desktop-based exercises reported in literature. In addition, agreement was compared with that of non-experts undertaking the same exercise, and results were further stratified to assess the impact of factors expected of affected assessments. Intraclass correlation coefficients of absolute agreement (ICC1) and consistency (ICC3) between raters were calculated. Sensitivity and specificity were estimated using a probabilistic simulation methodology developed previously. Fourteen occupational hygienists and exposure assessors with complete data for all 48 job descriptions and 8 non-experts participated. Although confidence intervals about correlation-coefficient differences are not reported, the individual limits were found to be so broad as to suggest that no statistically significant comparisons can be made. Nevertheless, preliminary observations are presented here as suggested by the computed means. Absolute agreement between expert raters was fair-good, but was somewhat better for intensity (ICC1 = 0.61) than for probability (ICC1 = 0.44) of exposure and was better for experts than non-experts. Estimated sensitivity was 0.95 and specificity 0.82 for intensity, and 0.91 and 0.78 for probability of exposure, respectively. Stratification for factors hypothesized to affect agreement did not show statistically significant differences, but consistent patterns of point estimates indicated that agreement between raters (both expert on non-experts) dropped for medium levels of information compared with little or extensive information. Inclusion of a photo or video generally improved agreement between experts but not between non-experts, whereas the year of the job description had no influence on the assessments. These data indicate that the desktop exposure assessment exercise was of similar quality to previously reported levels of agreement. Agreements between experts' assessments were independent of the time period of the job and can be improved by inclusion of visual material. Agreement between experts as well as the non-experts does not increase with the detail of provided job information.

Comparison of algorithm-based estimates of occupational diesel exhaust exposure to those of multiple independent raters in a population-based case-control study

OBJECTIVES

Algorithm-based exposure assessments based on patterns in questionnaire responses and professional judgment can readily apply transparent exposure decision rules to thousands of jobs quickly. However, we need to better understand how algorithms compare to a one-by-one job review by an exposure assessor. We compared algorithm-based estimates of diesel exhaust exposure to those of three independent raters within the New England Bladder Cancer Study, a population-based case-control study, and identified conditions under which disparities occurred in the assessments of the algorithm and the raters.

METHODS

Occupational diesel exhaust exposure was assessed previously using an algorithm and a single rater for all 14 983 jobs reported by 2631 study participants during personal interviews conducted from 2001 to 2004. Two additional raters independently assessed a random subset of 324 jobs that were selected based on strata defined by the cross-tabulations of the algorithm and the first rater's probability assessments for each job, oversampling their disagreements. The algorithm and each rater assessed the probability, intensity and frequency of occupational diesel exhaust exposure, as well as a confidence rating for each metric. Agreement among the raters, their aggregate rating (average of the three raters' ratings) and the algorithm were evaluated using proportion of agreement, kappa and weighted kappa (κw). Agreement analyses on the subset used inverse probability weighting to extrapolate the subset to estimate agreement for all jobs. Classification and Regression Tree (CART) models were used to identify patterns in questionnaire responses that predicted disparities in exposure status (i.e., unexposed versus exposed) between the first rater and the algorithm-based estimates.

RESULTS

For the probability, intensity and frequency exposure metrics, moderate to moderately high agreement was observed among raters (κw = 0.50-0.76) and between the algorithm and the individual raters (κw = 0.58-0.81). For these metrics, the algorithm estimates had consistently higher agreement with the aggregate rating (κw = 0.82) than with the individual raters. For all metrics, the agreement between the algorithm and the aggregate ratings was highest for the unexposed category (90-93%) and was poor to moderate for the exposed categories (9-64%). Lower agreement was observed for jobs with a start year <1965 versus ≥1965. For the confidence metrics, the agreement was poor to moderate among raters (κw = 0.17-0.45) and between the algorithm and the individual raters (κw = 0.24-0.61). CART models identified patterns in the questionnaire responses that predicted a fair-to-moderate (33-89%) proportion of the disagreements between the raters' and the algorithm estimates.

DISCUSSION

The agreement between any two raters was similar to the agreement between an algorithm-based approach and individual raters, providing additional support for using the more efficient and transparent algorithm-based approach. CART models identified some patterns in disagreements between the first rater and the algorithm. Given the absence of a gold standard for estimating exposure, these patterns can be reviewed by a team of exposure assessors to determine whether the algorithm should be revised for future studies.

Effect of training on exposure judgment accuracy of industrial hygienists

Results are presented from a study that investigated the effect of data interpretation training on exposure judgment accuracy of industrial hygienists across several companies in different industry sectors. Participating companies provided monitoring information on specific exposure tasks. Forty-nine hygienists from six companies participated in the study, and 22 industrial tasks were evaluated. The number of monitoring data points for individual tasks varied between 5 and 24. After reviewing all available basic characterization information for the job, task, and chemical, hygienists were asked to provide their judgment on the probability of the 95th percentile of the underlying exposure distribution being located in one of four exposure categories relative to the occupational exposure limit as outlined in the AIHA exposure assessment strategy. Ninety-three qualitative judgments (i.e., without reviewing monitoring data) and 2142 quantitative judgments (i.e., those made after reviewing monitoring data) were obtained. Data interpretation training, with simple rules of thumb for estimating 95th percentiles, was provided to all hygienists. A data interpretation test was administered before and after training. All exposure task judgments were collected before and after training. Data interpretation test accuracy for the hygienists increased from 48% to 67% after training (p < 0.001) and a significant underestimation bias was removed. Hygienist quantitative task judgment accuracy improved from 46% to 69% (p < 0.001) post-training. Accuracy results showed good improvement in industrial hygienists' quantitative judgments as a result of training. Hence, the use of statistical tools is promoted to improve judgments based on monitoring data and provide feedback and calibration to improve qualitative judgments. It may be worthwhile to develop standard training programs to improve exposure judgments.

Inter-rater reliability of assessed prenatal maternal occupational exposures to solvents, polycyclic aromatic hydrocarbons, and heavy metals

Because direct measurements of past occupational exposures are rarely available in population-based case-control studies, exposure assessment of job histories by multiple expert raters is frequently used; however, the subjective nature of this method makes measuring reliability an important quality control step. We evaluated inter-rater reliability of 7729 retrospective jobs reported in the National Birth Defects Prevention Study. Jobs were classified as exposed, unexposed, or exposure unknown by two independent industrial hygienists; exposed jobs were further evaluated for intensity, frequency, and routes. Exposure prevalence ranged from 0.1-9.8%. Inter-rater reliability for exposure (yes/no), assessed by kappa coefficients, was fair to good for cadmium (κ = 0.46), chlorinated solvents (κ = 0.59), cobalt (κ = 0.54), glycol ethers (κ = 0.50), nickel compounds (κ = 0.65), oil mists (κ = 0.63), and Stoddard Solvent (κ = 0.55); PAHs (κ = 0.24) and elemental nickel (κ = 0.37) had poor agreement. After a consensus conference resolved disagreements, an additional 4962 jobs were evaluated. Inter-rater reliability improved or stayed the same for cadmium (κ = 0.51), chlorinated solvents (κ = 0.81), oil mists (κ = 0.63), PAHs (κ = 0.52), and Stoddard solvent (κ = 0.92) in the second job set. Inter-rater reliability varied by exposure agent and prevalence, demonstrating the importance of measuring reliability in studies using a multiple expert rater method of exposure assessment.

Validity and reliability of exposure assessors' ratings of exposure intensity by type of occupational questionnaire and type of rater

BACKGROUND

In epidemiologic studies that rely on professional judgment to assess occupational exposures, the raters' accurate assessment is vital to detect associations. We examined the influence of the type of questionnaire, type of industry, and type of rater on the raters' ability to reliably and validly assess within-industry differences in exposure. Our aim was to identify areas where improvements in exposure assessment may be possible.

METHODS

Subjects from three foundries (n = 72) and three textile plants (n = 74) in Shanghai, China, completed an occupational history (OH) and an industry-specific questionnaire (IQ). Six total dust measurements were collected per subject and were used to calculate a subject-specific measurement mean, which was used as the gold standard. Six raters independently ranked the intensity of each subject's current job on an ordinal scale (1-4) based on the OH alone and on the OH and IQ together. Aggregate ratings were calculated for the group, for industrial hygienists, and for occupational physicians. We calculated intra-class correlation coefficients (ICCs) to evaluate the reliability of the raters. We calculated the correlation between the subject-specific measurement means and the ratings to evaluate the raters' validity. Analyses were stratified by industry, type of questionnaire, and type of rater. We also examined the agreement between the ratings by exposure category, where the subject-specific measurement means were categorized into two and four categories.

RESULTS

The reliability and validity measures were higher for the aggregate ratings than for the ratings from the individual raters. The group's performance was maximized with three raters. Both the reliability and validity measures were higher for the foundry industry than for the textile industry. The ICCs were consistently lower in the OH/IQ round than in the OH round in both industries. In contrast, the correlations with the measurement means were higher in the OH/IQ round than in the OH round for the foundry industry (group rating, OH/IQ: Spearman rho = 0.77; OH: rho = 0.64). No pattern by questionnaire type was observed for the textile industry (group rating, Spearman rho = 0.50, both assessment rounds). For both industries, the agreement by exposure category was higher when the task was reduced to discriminating between two versus four exposure categories.

CONCLUSIONS

Assessments based on professional judgment may reduce misclassification by using two or three raters, by using questionnaires that systematically collect task information, and by defining intensity categories that are distinguishable by the raters. However, few studies have the resources to use multiple raters and these additional efforts may not be adequate for obtaining valid subjective ratings. Thus, improving exposure assessment approaches for studies that rely on professional judgment remain an important research need.

Maternal exposure to polychlorinated biphenyls and the secondary sex ratio: an occupational cohort study

BACKGROUND

Though commercial production of polychlorinated biphenyls was banned in the United States in 1977, exposure continues due to their environmental persistence. Several studies have examined the association between environmental polychlorinated biphenyl exposure and modulations of the secondary sex ratio, with conflicting results.

OBJECTIVE

Our objective was to evaluate the association between maternal preconceptional occupational polychlorinated biphenyl exposure and the secondary sex ratio.

METHODS

We examined primipara singleton births of 2595 women, who worked in three capacitor plants at least one year during the period polychlorinated biphenyls were used. Cumulative estimated maternal occupational polychlorinated biphenyl exposure at the time of the infant's conception was calculated from plant-specific job-exposure matrices. A logistic regression analysis was used to evaluate the association between maternal polychlorinated biphenyl exposure and male sex at birth (yes/no).

RESULTS

Maternal body mass index at age 20, smoking status, and race did not vary between those occupationally exposed and those unexposed before the child's conception. Polychlorinated biphenyl-exposed mothers were, however, more likely to have used oral contraceptives and to have been older at the birth of their first child than non-occupationally exposed women. Among 1506 infants liveborn to polychlorinated biphenyl-exposed primiparous women, 49.8% were male; compared to 49.9% among those not exposed (n = 1089). Multivariate analyses controlling for mother's age and year of birth found no significant association between the odds of a male birth and mother's cumulative estimated polychlorinated biphenyl exposure to time of conception.

CONCLUSIONS

Based on these data, we find no evidence of altered sex ratio among children born to primiparous polychlorinated biphenyl-exposed female workers.

The role of exposure reconstruction in occupational human health risk assessment: current methods and a recommended framework

Exposure reconstruction for substances of interest to human health is a process that has been used, with various levels of sophistication, as far back as the 1930s. The importance of robust and high-quality exposure reconstruction has been recognized by many researchers. It has been noted that misclassification of reconstructed exposures is relatively common and can result in potentially significant effects on the conclusions of a human health risk assessment or epidemiology study. In this analysis, a review of the key exposure reconstruction approaches described in over 400 papers in the peer-reviewed literature is presented. These approaches have been critically evaluated and classified according to quantitative, semiquantitative, and qualitative approaches. Our analysis indicates that much can still be done to improve the overall quality and consistency of exposure reconstructions and that a systematic framework would help to standardize the exposure reconstruction process in the future. The seven recommended steps in the exposure reconstruction process include identifying the goals of the reconstruction, organizing and ranking the available data, identifying key data gaps, selecting the best information sources and methodology for the reconstruction, incorporating probabilistic methods into the reconstruction, conducting an uncertainty analysis, and validating the results of the reconstruction. Influential emerging techniques, such as Bayesian data analysis, are highlighted. Important issues that will likely influence the conduct of exposure reconstruction into the future include improving statistical analysis methods, addressing the issue of chemical mixtures, evaluating aggregate exposures, and ensuring transparency with respect to variability and uncertainty in the reconstruction effort.

The influence of sociodemographic characteristics on agreement between self-reports and expert exposure assessments

BACKGROUND

Often in exposure assessment for epidemiology, there are no highly accurate exposure data and different measurement methods are considered. The objective of this study was to use various statistical techniques to explore agreement between individual reports and expert ratings of workplace exposures in several industries and investigate the sociodemographic influences on this agreement.

METHODS

A cohort of 1,282 employees at 4 industries/14 worksites answered questions on workplace physical, chemical, and psychosocial exposures over the past 12 months. Occupational hygienists constructed job exposure matrices (JEMs) based on worksite walkthrough exposure evaluations. Worker self-reports were compared with the JEMs using multivariable analyses to explore discord.

RESULTS

There was poor agreement between the self-reported and expert exposure assessments, but there was evidence that agreement was modified by sociodemographic characteristics. Several characteristics including gender, age, race/ethnicity, hourly wage and nativity strongly affected the degree of discord between self-reports and expert raters across a wide array of different exposures.

CONCLUSIONS

Agreement between exposure assessment tools may be affected by sociodemographic characteristics. This study is cross-sectional and therefore, a snapshot of potential exposures in the workplace. Nevertheless, future studies should take into account the social contexts within which workplace exposures occur.

Inter-rater agreement for a retrospective exposure assessment of asbestos, chromium, nickel and welding fumes in a study of lung cancer and ionizing radiation

A retrospective exposure assessment of asbestos, welding fumes, chromium and nickel (in welding fumes) was conducted at the Portsmouth Naval Shipyard for a nested case-control study of lung cancer risk from external ionizing radiation. These four contaminants were included because of their potential to confound or modify the effect of a lung cancer-radiation relationship. The exposure assessment included three experienced industrial hygienists from the shipyard who independently assessed exposures for 3519 shop/job/time period combinations. A consensus process was used to resolve estimates with large differences. Final exposure estimates were linked to employment histories of the 4388 study subjects to calculate their cumulative exposures. Inter-rater agreement analyses were performed on the original estimates to better understand the estimation process. Although concordance was good to excellent (78-99%) for intensity estimates and excellent (96-99%) for frequency estimates, overall simple kappa statistics indicated only slight agreement beyond chance (kappa < 0.2). Unbalanced distributions of exposure estimates partly contributed to the weak observed overall inter-rater agreement. Pairwise weighted kappa statistics revealed better agreement between two of the three panelists (kappa = 0.19-0.65). The final consensus estimates were similar to the estimates made by these same two panelists. Overall welding fume exposures were fairly stable across time at the shipyard while asbestos exposures were higher in the early years and fell in the mid-1970s. Mean cumulative exposure for all study subjects was 520 fiber-days cc(-1) for asbestos and 1000 mg-days m(-3) for welding fumes. Mean exposure was much lower for nickel (140 microg-days m(-3)) and chromium (45 microg-days m(-3)). Asbestos and welding fume exposure estimates were positively associated with lung cancer in the nested case-control study. The radiation-lung cancer relationship was attenuated by the inclusion of these two confounders. This exposure assessment provided exposure estimates that aided in understanding of the lung cancer-radiation relationship at the shipyard.

Methodological issues regarding confounding and exposure misclassification in epidemiological studies of occupational exposures

BACKGROUND

Confounding and exposure misclassification are issues that concern epidemiologists because of their potential to bias results of studies and complicate interpretations. In occupational epidemiology both are routinely raised to argue that an observed result is either a false positive or a false negative finding. Although it is important to consider the potential for limitations of epidemiologic investigations, judgment regarding their importance should be based on their actual likelihood of occurrence.

METHODS

This paper is based on our experience in epidemiologic analyses and a brief review of the literature regarding confounding and exposure misclassification.

RESULTS

Examples of substantial confounding are rare in occupational epidemiology. In fact, even for studies of occupational exposures and lung cancer, tobacco-adjusted relative risks rarely differ appreciably from the unadjusted estimates. This is surprising because it seems the perfect situation for confounding to occur. Yet, despite the lack of evidence that confounding is a common problem, nearly every epidemiologic paper includes a lengthy discussion on uncontrolled or residual confounding. On the other hand, exposure misclassification probably occurs in all studies. The only question is, how much? The direction and magnitude of nondifferential exposure misclassification (the type most likely to occur in cohort studies) on estimates of relative risks can be largely predicted given knowledge on the degree of misclassification, that is, relatively small amounts of misclassification can bias relative risks substantially towards the null. The literature, however, is full of discussions implying that misclassification of exposure is an explanation for a positive finding.

CONCLUSIONS

These comments are not to suggest that all potential limitations for epidemiologic studies should not be considered and evaluated. We do believe, however, that the likelihood of occurrence and the direction and magnitude of the effect should be more carefully and realistically considered when making judgments about study design or data interpretation.

Inter-rater agreement in the assessment of exposure to carcinogens in the offshore petroleum industry

OBJECTIVES

To evaluate the reliability of an expert team assessing exposure to carcinogens in the offshore petroleum industry and to study how the information provided influenced the agreement among raters.

METHODS

Eight experts individually assessed the likelihood of exposure for combinations of 17 carcinogens, 27 job categories and four time periods (1970-1979, 1980-1989, 1990-1999 and 2000-2005). Each rater assessed 1836 combinations based on summary documents on carcinogenic agents, which included descriptions of sources of exposure and products, descriptions of work processes carried out within the different job categories, and monitoring data. Inter-rater agreement was calculated using Cohen's kappa index and single and average score intraclass correlation coefficients (ICC) (ICC(2,1) and ICC(2,8), respectively). Differences in inter-rater agreement for time periods, raters, International Agency for Research on Cancer groups and the amount of information provided were consequently studied.

RESULTS

Overall, 18% of the combinations were denoted as possible exposure, and 14% scored probable exposure. Stratified by the 17 carcinogenic agents, the probable exposure prevalence ranged from 3.8% for refractory ceramic fibres to 30% for crude oil. Overall mean kappa was 0.42 (ICC(2,1) = 0.62 and ICC(2,8) = 0.93). Providing limited quantitative measurement data was associated with less agreement than for equally well described carcinogens without sampling data.

CONCLUSION

The overall kappa and single-score ICC indicate that the raters agree on exposure estimates well above the chance level. The levels of inter-rater agreement were higher than in other comparable studies. The average score ICC indicates reliable mean estimates and implies that sufficient raters were involved. The raters seemed to have enough documentation on which to base their estimates, but provision of limited monitoring data leads to more incongruence among raters. Having real exposure data, with the inherent variability of such data, apparently makes estimating exposure in a rigid semiquantitative manner more difficult.

Assessing Exposure Misclassification by Expert Assessment in Multicenter Occupational Studies

BACKGROUND

In a multicenter case-control study of lung cancer in central and eastern Europe and in Liverpool, exposure to occupational agents was assessed by teams of local experts. We performed an interteam agreement study to estimate the levels of exposure misclassification and the expected attenuation of the risk estimate.

METHODS

Eight teams of experts and a reference rater assessed exposure to 70 putative lung carcinogens for 19 jobs. Agreement among teams was calculated through Cohen's kappa, sensitivity, and specificity.

RESULTS

Each team showed an overall fair to good agreement with the reference (kappa between 0.53 and 0.64). The agreement among teams in the presence of exposure was excellent for 9 agents, fair to good for 16, and poor for 29. For all agents the specificity was high (average 0.94), although sensitivity varied considerably.

CONCLUSIONS

This study of expert exposure assessment showed a small range in reliability among teams of experts, but large differences among agents. This paper presents the range in levels of misclassification that can be expected using experts for assessing occupational exposure to different agents, and the attenuation of the odds ratio that can be expected to result from this misclassification.

Occupational silica exposure and risk of various diseases: an analysis using death certificates from 27 states of the United States

BACKGROUND

Although crystalline silica exposure is associated with silicosis, lung cancer, pulmonary tuberculosis, and chronic obstructive pulmonary disease (COPD), there is less support for an association with autoimmune disease, and renal disease.

METHODS

Using data from the US National Occupational Mortality Surveillance (NOMS) system, a matched case-control design was employed to examine each of several diseases (including silicosis, lung cancer, stomach cancer, oesophageal cancer, COPD, pulmonary tuberculosis, sarcoidosis, systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, and various types of renal disease). Cases were subjects whose death certificate mentioned the disease of interest. A separate control group for each of the diseases of interest was selected from among subjects whose death certificate did not mention the disease of interest or any of several diseases reported to be associated with crystalline silica exposure. Subjects were assigned into a qualitative crystalline silica exposure category based on the industry/occupation pairing found on their death certificate. We also investigated whether silicotics had a higher risk of disease compared to those without silicosis.

RESULTS

Those postulated to have had detectable crystalline silica exposure had a significantly increased risk for silicosis, COPD, pulmonary tuberculosis, and rheumatoid arthritis. In addition, a significant trend of increasing risk with increasing silica exposure was observed for these same conditions and for lung cancer. Those postulated to have had the greatest crystalline silica exposure had a significantly increased risk for silicosis, lung cancer, COPD, and pulmonary tuberculosis only. Finally, those with silicosis had a significantly increased risk for COPD, pulmonary tuberculosis, and rheumatoid arthritis.

CONCLUSIONS

This study corroborates the association between crystalline silica exposure and silicosis, lung cancer, COPD, and pulmonary tuberculosis. In addition, support is provided for an association between crystalline silica exposure and rheumatoid arthritis.

Occupational exposure assessment in case-control studies: opportunities for improvement

Community based case-control studies are an efficient means to study disease aetiologies, and may be the only practical means to investigate rare diseases. However, exposure assessment remains problematic. We review the literature on the validity and reliability of common case-control exposure assessment methods: occupational histories, job-exposure matrices (JEMs), self reported exposures, and expert assessments. Given the variable quality of current exposure assessment techniques, we suggest methods to improve assessments, including the incorporation of hygiene measurements: using data from administrative exposure databases; using results of studies identifying determinants of exposure to develop questionnaires; and where reasonable given latency and biological half life considerations, directly measuring exposures of study subjects.