RETROSPECTIVE BENZENE AND TOTAL HYDROCARBON EXPOSURE ASSESSMENT FOR APETROLEUM MARKETING AND DISTRIBUTION WORKER EPIDEMIOLOGY STUDY

A quantitative exposure-estimating algorithm for benzene and total hyd rocarbons was developed for a case control study of petroleum marketin g and distribution workers. The algorithm used a multiplicative model to adjust recently measured quantitative exposure data to past scenari os for which representative exposure measurement data did not exist. T his was accomplished through the development of exposure modifiers to account for differences in the workplace, the materials handled,the en vironmental conditions, and the tasks performed. Values for exposure m odifiers were obtained empirically and through physical/chemical relat ionships. Dates for changes that altered exposure potential were obtai ned from archive records, retired employee interviews, and from curren t operations personnel. Exposure modifiers were used multiplicatively, adjusting available measured data to represent the relevant exposure scenario and time period. Changes in exposure modifiers translated to step changes in exposure estimates. Though limited by availability of data, a validation exercise suggested that the algorithm provided accu rate exposure estimates for benzene (compared with measured data in in dustrial hygiene survey reports); the estimates generally differed by an average of less than 20% from the measured values. This approach is proposed to quantify exposures retrospectively where there are suffic ient data to develop reliable current era estimates and where a histor ical accounting of key exposure modifiers can be developed, but where there are insufficient historic exposure measurements to directly asse ss historic exposures.