No abstract

The AgDRIFT aerial dispersion model is well validated and closely related to the AGDISP model developed by the USDA Forest Service to determine on-and off-target deposition and penetration of aerially applied pesticide through foliage of trees. The Exposure Opportunity Index (EOI) model was developed to estimate relative exposure of ground troops in Vietnam to aerially applied herbicides. We compared the output of the two models to determine whether their predictions were in substantial agreement, but found a total lack of concordance. While the AgDRIFT model estimated that ground-level deposition through foliage was reduced more than 20 orders of magnitude at less than 1 km from the flight line, the EOI model predicted deposition declines less than one order of magnitude 4 km from the flight line. Interestingly the EOI model predicts a four-fold variability in EOI on the flight line, where exposure should be essentially invariant because the spray apparatus is designed to apply herbicide at a constant rate. We believe that the EOI model cannot be used to provide individual exposure estimates for the purpose of conducting epidemiologic studies. Moreover, evaluation of the position data for both herbicide spray swaths and troop locations, together with the actual patterns of spray deposition predicted by the AgDRIFT model, suggests that precise individual-level exposure assessments for ground troops in Vietnam are impossible. However, we suggest that well-validated tools like AgDRIFT can be used to estimate exposure to groups of individuals.

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An historical cohort mortality study of a continuous filament fiberglass manufacturing plant was undertaken to determine whether an elevated lung cancer risk would be observed on a cohort basis. A nested case-control study of white male lung cancer deaths was incorporated into the study design. An interview survey to obtain information on sociodemographic factors, including smoking, and an historical environmental reconstruction to identify elements in the plant environment to which workers might be exposed were included in the study design. Respirable glass (Beta) fibers were produced only from 1963 to 1968. The lung cancer odds ratio (OR) among those workers exposed to respirable glass fibers is below unity, as are ORs for exposure to asbestos, refractory ceramic fibers, respirable silica (except for the lowest exposure level), total chrome and arsenic. There is a suggestion of an increase with exposure among smokers only for exposure to formaldehyde, although the OR for the highest level is based on only one case and is not likely to be meaningful. None of these plant exposures suggests an increase in lung cancer risk for this population. Although the lung cancer standardized mortality ratios are slightly elevated, results of the case-control investigation confirm that neither respirable glass fibers nor any of the substances investigated as part of the plant environment are associated with an increase in lung cancer risk for this population.

A case-control study was conducted to determine the influence of non-workplace factors on risk of respiratory disease among workers at the Owens-Corning Fiberglas plant in Newark, Ohio. Cases and controls were drawn from a historical cohort mortality study conducted on behalf of the Thermal Insulation Manufacturers Association (TIMA) of workers employed at Newark for at least one year between 1 January 1940 and 31 December 1963 and followed up to the end of 1982. The TIMA study reported a statistically significant increase in respiratory cancer (compared with national death rates). Interviews were completed for 144 lung cancer cases and 299 matching controls and 102 non-malignant respiratory disease cases and 201 matching controls. Unadjusted odds ratios (ORs) were used to assess the association between lung cancer or non-malignant respiratory disease and birthplace, education, income, marital state, smoking with a duration of six months or more, age at which smoking first started, and duration of smoking. Only the smoking variables were statistically significant. For lung cancer, of the variables entered into a conditional logistic regression model, only the smoking OR of 23.4 (95% CI 3.2-172.9) was statistically significant. For non-malignant respiratory disease no variables entered into the final model were statistically significant. Results of the interview portion of our case-control study clearly indicate that smoking is the most important non-workplace factor for risk of lung cancer in this group of workers. Smoking does not seem to play as important a part, however, for non-malignant respiratory disease. Prevalence of cigarette smoking at the Newark plant was estimated for birth cohorts by calendar year. Corresponding data for the United States were compiled from national smoking surveys. Prevalence of cigarette smoking for Newark in 1955 appears to be sufficiently greater than the corresponding United States data in 1955 to suggest that some of the previously reported excess of lung cancer for Newark based on United States mortality may be accounted for by differences in the prevalence of cigarette smoking between white men in Newark and those in the United States as a whole.