A progress report: the investigation of brain tumors at the Texas Division of Dow Chemical.

During the six-month period since this investigation was initiated, an increased risk of death due to brain tumor was linked with employment at the Texas Division of Dow Chemical by the results of a case-control study based on county death certificates. Specifically, the county-based case-control study yielded an odds ratio of 2.54 with a 90% confidence interval of the odds ratio extending from 1.23 to 6.80. Additional investigations were initiated which resulted in the ascertainment of 25 brain tumor deaths among former Dow employees. Of these cases, 84% were initially employed between 1940 and 1946 and 64% can be described as glioblastomas or astrocytomas grade III and IV. Detailed protocols have been developed for a sample-based cohort study and a series of in-plant case-control studies. The sample-based cohort study is nearing completion and the in-plant case-control studies are anticipated to begin in the near future. The study design serving as the framework of this investigation represents a modest departure from the traditional epidemiologic study designs. This sample-based approach was designed to circumvent or minimize the usual problems associated with the use of massive collections of data that have been partially automated, if at all. The anticipated benefits will be conservation of limited staff resources and a reduction of the time necessary to complete a large-scale epidemiologic investigation.