Cardiovascular mortality in mercury miners

BACKGROUND AND OBJECTIVES: To study the mortality from cardiovascular diseases after long-term exposure to inorganic mercury.

POPULATION AND METHOD: 3,998 workers exposed to mercury in Minas de Almadén y Arrayanes S.A. were studied. The follow-up period was a century, since 1895 to 1994. The study was completed assessing the vital status and the basic cause of death, in case of fatalities. Standardized mortality ratios (SMR) by age, sex and calendar period were calculated. Expected deaths were obtained from age, sex and calendar period specific from rates for the Spanish and regional populations.

RESULTS: A significant increase in mortality due to circulatory diseases was found (SMR 1.11, 95% confidence interval [CI], 1.02-1.20), especially for hypertension (SMR 2.78, 95% CI, 1.89-3.95), cerebrovascular diseases (SMR 1.17, 95% CI, 1.01-1.35), and other diseases of the heart (SMR 1.51, 95% CI, 1.29-1.76). Ischemic heart disease showed a significant decrease in these workers, with an SMR 0.69, and a CI between 0.57 and 0.84. Cerebrovascular diseases showed a trend over the time since first exposure, duration of exposure and with the accumulated expected exposure, while none of the exposure variables was linearly associated with mortality due to ischemic heart diseases. There was also a trend over the time since first exposure for mortality due to hypertension and other heart diseases.

CONCLUSIONS: This study suggests an association between long-term exposure to inorganic mercury in workers of mercury mines and an increased risk of circulatory mortality, especially mortality due to hypertension and cerebrovascular diseases.