Assessment of occupational exposures in a general population: comparison of different methods

Objectives-To evaluate the relative merits of job specific questionnaires a cid various alternative assessment methods of occupational exposures often used in general population studies. Methods-Subjects were participants in a hospital based case-control study o f risk factors for male infertility. Estimates of exposure to organic solve nts and chromium, based on job specific questionnaires, generic questionnai res, self reports of exposure, an external job exposure matrix (JEM), and a population specific JEM were compared with passive diffuse dosimeter resul ts and measurements in urine. Urine samples from the end of the shift were analysed for metabolites of toluene, xylene, several glycol ethers, trichlo roethylene, and chromium. Passive dosimeter date, metabolites of specific s olvents, and urinary chromium concentrations were available for 89, 267, an d 156 subjects, respectively. The alternative methods and measurements in u rine were compared by means of the Cohen's kappa statistic and by computing the positive predictive value, sensitivity, and specificity of the alterna tive methods against measurements in urine. Results-Passive dosimeter results indicated that exposure classifications w ith job specific questionnaire information could discriminate between high and low exposures. The kappa coefficients were <0.4, so agreement between t he various methods and measurements in urine was poor. Sensitivity of the m ethods ranged from 0.21 to 0.85, whereas specificity ranged from 0.34 to 0. 94. Positive predictive values ranged from 0.19 to 0.58, with the highest v alues for job specific questionnaires. Conclusions-The results indicate that the implementation of job specific qu estionnaires in a general population study might be worth the extra expense it entails, bearing in mind the paramount importance of avoiding false pos itive exposure estimates when exposure prevalence is low.