Ischemic Heart Disease Mortality Reduction in an Arseniasis-Endemic Area in Southwestern Taiwan After a Switch in the Tap-Water Supply System

Arsenic has been identified as a major contributing risk factor for development of blackfoot disease (BFD), a unique peripheral vascular disease that was endemic to the southwestern coast of Taiwan, where residents imbibed artesian well water continuing high amounts of arsenic for more than 50 yr. Chronic arsenic exposure was found to be associated with ischemic heart disease (CHD) in a dose-dependent manner. A tap-water supply system was implemented in the early 1960s in the BFD-endemic areas. Artesian well water was no longer used for drinking and cooking after the mid-1970s. The objective of this study was to examine whether CHD-related mortality decreased after consumption of high-arsenic-containing artesian well water ceased and, if so, when the reduction occurred. Standardized mortality ratios (SMRs) for CHD were calculated for the BFD endemic area for the years 1971-2000. Cumulative-sum techniques were used to detect the occurrence of changes in the SMRs. Data show that mortality attributed to CHD declined gradually for approximately 17 to 20 yr following cessation of consumption of high-arsenic artesian well water. Based on the reversibility criterion, the association between arsenic exposure an1rd CHD-related mortality is likely to be causal.