Feasibility study for a long-term follow-up in a historical cohort of Brazilian coalminers

Abstract

The first Brazilian historical mortality cohort study on miners was conducted. The cohortconsisted of 3224 workers in the underground coal mining industry in southernBrazil. This industry has been operating since 1942 without compliance with anyregulatory standards, since there were no relevant national regulations. Overalmost 60 years, about 5000 workers were exposed to high levels of radiation.However, later radiation exposure was significantly reduced, particularly that due toradon exposure. Recent radon concentration measurements indicated an averageannual exposure to radon progeny of 2.1 WLM, ranging from 0.2 to 7.2 WLM. Asradon exposure in the past was unknown, it can be suggested that mine workershave not been working safely as regards the health hazard related to radon andradon progeny exposure. The cohort inclusion criteria are as follows: (a) all maleemployees who had worked for at least one year at the coal mine; (b) workers withcomplete workplace information (underground and surface); (c) employment hiringbetween 1945 and 1997 and (d) the worker must have been alive on 1 January 1979.Through multiple strategies of search it was possible to follow up the members of thecohort with a success rate of 92%. This paper presents the characteristics of thestudy population and provides information about the feasibility of conducting aretrospective mortality study in Brazil, taking into account the methodologicaland logistical difficulties of conducting such a study in a developing country.