Validity and reliability of a method for retrospective evaluation of chlorophenate exposure in the lumber industry

Abstract

This paper describes the validity and reliability of a method to retrospectively assess exposure to antisapstain agents used in sawmills (chlorophenates). The method is based on experienced workers' estimates of exposure for each job title at the sawmill where they work. At a pilot mill, 10 randomly selected workers estimated the frequency and duration of exposures to chlorophenates for all 59 job titles. The reliability of their mean exposure estimates was very high, with an intraclass correlation coefficient for all raters of 0.91 (based on a calculated index of exposure). To assess validity, urinary chlorophenate levels were measured for 86% of the workers at the mill during the summer and/or fall, and compared to experienced workers' estimates of exposure. The correlation between workers' exposure estimates and the urinary chlorophenate levels for each job title were consistently above 0.65 for all analyses and greater than 0.72 when summer and fall urine sample results were averaged. The evidence indicates that the validity and reliability of worker exposure estimates are high enough to justify investigation of the method's generalizability to other sawmills.

Childhood cancer in the offspring of male sawmill workers occupationally exposed to chlorophenate fungicides.

“…retrospective cohort studies there exists some possibility of exposure misclassification, the initial study of cancer incidence and mortality among male sawrnill workers used an exposure assessrnent that was shown to be valid and reliable (Teschke et al 1996, Teschke et al 1990, Hertzman et al 1988 fiom the above two studies should probably be taken with caution. They both, however, may warrant M e r research to follow-up on and corroborate their observations.…”

“…However, any misclassification that did occur would likely have been non-differential and therefore would have biased the fïndings towards the null, and therefore obscured true dose-response relationships. This dampening of dose-response has been descri bed in a paper examining the reliability and validity of a retrospective exposure assessment to tetra and pentachlorophenates in the sawmill industry (Hertzman et al 1988 childhood cancer are the two leading causes of mortality among children. However, the rate for these causes of death is so low that it is unlikely that many person-years of observation would be censored, nor should the nsk of death for children of fathers with high chlorophenate exposures differ from those with low exposures.…”

“…A detailed description of the procedure and urinary analysis can be found in Hertzman et al 1988. At the time of sampling, each worker completed a self-admuiistered questiomaire about his job and personal protective equipment used.…”

Reliability of a semi-quantitative method for dermal exposure assessment (DREAM)

“…Kromhout et al (1987) reported kappa values between 0.23 and 0.50 for two occupational hygienists, who ranked tasks with inhalation exposures to total solvents, and different types of dust (organic, fibers, welding fumes) on a semi-quantitative 4-point scale by means of workplace observations. Hertzman et al (1988) found an ICC of 0.55 for 10 workers, applying an exposure index that was based on assessed frequency and duration of exposure to chlorophenates for 59 jobs. Siematycki et al (1997) reported a weighted kappa of 0.70 for two experts assessing inhalation exposures for 294 workplace chemicals on the basis of job histories.…”

“…Semi-quantitative exposure assessment has generally aimed at assessing inhalation exposures and hardly at assessing dermal exposures (Kromhout et al, 1987;Hertzman et al, 1988;Hawkins and Evans, 1989;Teschke et al, 1989;Post et al, 1991;de Cock et al, 1996; Siematycki et al, 1997; Benke et al, 1997;Cherrie and Schneider, 1999;Vermeulen et al, 2002;Walker et al, 2003). Even for contaminants for which dermal exposure is known to contribute significantly to internal dose (e.g., pesticides, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls (PCB)), exposure assessment is often directed to inhalation exposures, resulting in inaccurate and imprecise exposure estimates (Vermeulen et al, 2002).…”