Comparison of industrial hygienists' exposure evaluations for an epidemiologic study.

OBJECTIVES: A study was conducted to determine what level of information is required by industrial hygienists before they can develop exposure estimates comparable with those developed from a more in-depth evaluation.
METHODS: Three industrial hygienists evaluated formaldehyde exposures of 300 jobs selected from an earlier epidemiologic study. The jobs were evaluated over the following 6 cycles: (i) job title and industry; (ii) job title, industry, dates; (iii) job and department title and industry; (iv) cycle 3 information with dates; (v) cycle 3 information with a plant report; and (vi) job and department title, industry, dates, and the report. Each hygienist assigned jobs to 1 of 4 exposure categories, which were compared with the categories in the original epidemiologic study.
RESULTS: Overall, the mean differences between the hygienists' evaluations and the standard, although small, changed little over the cycles. The kappa statistic was poor to moderate for all the cycles, but the agreement was greater than expected due to chance. There was moderate improvement in overall agreement over the cycles using the weighted kappa statistic, but little improvement in the intraclass correlation coefficients of the hygienists' evaluations, which ranged from 0.4 to 0.5. Department information improved the agreement with the standard by 5--10%, but dates did not the improve agreement. There were some differences by type of plant, job function, exposure level, and date of the estimate. Using a hypothetical exposure-response scenario, this level of misclassification would have resulted in missing an association.
CONCLUSIONS: Although there was slight improvement with increasing levels of information, these findings suggest that the subjective categorical assessment of exposures by industrial hygienists will not produce exposure estimates comparable to more in-depth evaluations of exposure.