Reevaluation of benzene exposure for the Pliofilm (rubberworker) cohort (1936–1976)

Abstract

The Pliofilm cohort is the most intensely studied group of workers chronically exposed to benzene. Information on this cohort has been the basis for regulations and/or guidelines for occupational and environmental exposure to benzene. Rinsky et al. (1986, 1987) and Crump and Allen (1984) developed different approaches for reconstructing the exposure history of each member of the group. The predicted levels of exposure, combined with the data on the incidence of disease, have been used to estimate benzene's carcinogenic potency. In this paper, recent information from worker interviews and historical records from the National Archives and elsewhere were used to evaluate the accuracy of prior exposure estimates and to develop better ones for the cohort. The following factors were accounted for: (1) uptake of benzene due to short-term, high-level exposure to vapors, (2) uptake due to background concentrations in the manufacturing building, (3) uptake due to contact with the skin, (4) morbidity and mortality data on workers in the Pliofilm process, (5) the installation of industrial hygiene engineering controls, (6) extraordinarily long work weeks during the 1940s, (7) data indicating that airborne concentrations of benzene were underestimated due to inaccurate monitoring devices and the lack of adequate field calibration mated due to inaccurate monitoring devices and the lack of adequate field calibration of these devices, and (8) likely effectiveness of respirators and gloves. Our estimates suggest that Crump and Allen (1984) overestimated the exposure of workers in some job classifications and underestimated others, and that Rinsky et al. (1981, 1986) almost certainly underestimated the exposure of nearly all workers. Airborne concentrations of benzene at the St. Marys facility during the years of its operation were found (on average) to be about half those of the two Akron facilities. Our analysis indicates that short-term, high-level exposure to benzene vapors and dermal exposure significantly increased (by about 25-50%) the total absorbed dose of benzene for some workers. One of the key findings was that, unlike prior analyses, the three facilities probably had significantly different airborne concentrations of benzene, especially during the 1940s and 1950s.

Dermal exposure assessment in occupational epidemiologic research

“…Therefore, an estimate of the concentration of the contaminant on the skin can only be assessed subjectively at present, using the concentration of the contaminant in the source or on contaminated surfaces as an estimate of the concentration of the hazardous substance on the skin. Information about the concentration of the contaminant in the source can be retrieved historically, at least in certain occupational settings, as was shown in two epidemiologic studies (21,25). Retrospective exposure assessment studies should therefore attempt to collect as much information as possible about the concentration of the active ingredient in the source(s) or on contact surface(s) over time, together with information about the actual mass of the contaminant on the skin.…”

“…The algorithm included the application method (tractor-or boom-, backpack-, bike-spraying), the method of mixing and loading (direct tank filling, pouring, or scooping), the method of bulb disinfection (manual or mechanical dipping), the application rate (milligrams per hectare), the bulb acreage (hectares), the number of applications, the number of bulbs disinfected per year (number of containers), and a protection factor for personal protective equipment (range: 0 = no protection to 1 = complete protection) (24). In a study of Pliofilm™ workers, exposure to benzene was calculated on the basis of the concentration of benzene in the cement being used, the number of skin contacts with the cement per day, the surface area of the contacted skin (square centimeters), and the contact time (hours per day) (25)(26)(27). Dermal uptake (milligrams per kilogram per day) was subsequently calculated using these dermal exposure estimates, the dermal absorption rate (milligram per square centimeter per hour), and body weight of the individual (kilograms).…”

Legionnaires' disease: evaluation of a quantitative microbial risk assessment model

“…This difficulty in validating a risk assessment holds even for a relatively well-studied contaminant with extensive human epidemiologic data, such as benzene. For benzene, the underlying exposure assessment components of the risk assessments arguably remain in debate, with the Pliofilm benzene-exposed cohort the subject of at least 4 distinct exposure assessments (Rinsky et al 1987;Paustenbach et al 1992;Crump 1996;Williams & Paustenbach 2003).…”

Benzene‐Associated Leukemia and its Risk Assessment

“…Thus, their estimated value at the early stage (TLV at that time= 100 ppm) was higher than that estimated by Rinsky et al 51 . Meanwhile, Paustenbach et al 103) estimated exposure levels considering that unusually long working hours were practiced in the 1940s, the exposure during this period might be underestimated due to the lack of sufficient measurement apparatus, and that considerable amounts of benzene must have been absorbed through the skin under the working conditions at that time. In comparison to the estimates of Paustenbach et al, it may be concluded that those of Rinsky et al underestimated the benzene exposure in almost all workers, and those of Crump and Allen overestimated the exposure in some job categories and underestimated in others.…”