A Method to Estimate Concentrations of Chemicals for Unmeasured Jobs

The estimation of chemical exposures for unmeasured jobs is a well-recognized problem in occupational epidemiologic studies. This paper has described a simple Z-score method and its application in providing styrene concentration estimations by job and plant for a case cohort study on styrene exposure and ischemic heart disease as an example. This method of estimation assumes that the relative exposure of a job was similar across the industry because tasks associated with the job are similar, but individual plants may have overall differences in the actual levels of the chemicals. The exposure for an unmeasured job in a specific plant could be estimated based on the relative exposure level of that job from other plants and the concentration distribution parameters of measured jobs form the same plant. This method has overcome some disadvantages of existing methods for concentration estimation for unmeasured jobs.