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INTRODUCTION
Blackfoot disease (BFD) was an endemic peripheral vascular disease confined to the southwestern coast of Taiwan. Typical symptoms and signs of progressive arterial occlusion were mainly found in the lower extremities, but the upper extremities might also be involved in rare cases. Ulceration, gangrene, and spontaneous or surgical amputation were typical results (1, 2). Sporadic cases of BFD occurred as early as in the early 20th century, and peak incidence was noted between 1956 and 1960, with prevalence rates ranging from 6.51 to 18.85 per 1000 population in different villages. The disease could afflict patients in a wide range of ages, from 2 to 87 y, but the mean age of onset was 52 y (1). The sex ratio for men to women was 1.5:1 (1). The etiology of this endemic disease has been extensively sought during the past 50 y. This paper reviews the link between the exposure to arsenic from drinking artesian well water and the development of the disease.
ARSENIC EXPOSURE AND PREVALENCE OF BLACKFOOT DISEASE
BFD is an endemic disease confined to the southwestern coast of Taiwan. The disease is characterized by progressive narrowing of the peripheral vessels involving mainly the lower extremities. In rare cases, the upper extremities can also be involved (1). Clinical manifestations are characteristic of ischemia involving the lower legs, such as numbness or coldness, intermittent claudication, or absence of peripheral pulsation in the initial stage (1). The afflicted subjects might develop ulceration and gangrene in the involved extremities in a later stage, and spontaneous or surgical amputation was the typical result. Sporadic cases were noted since the early 20th century. However, not much attention had been paid until after the mid-20th century when cumulative case numbers became noticeable. Peak incidence of BFD was found between 1956 and 1960 (2, 3). The concentration of arsenic in the drinking water from the artesian wells in the endemic areas has been found to be high, with the median concentration ranging from 0.70 to 0.93 mg L^sup -1^ (4, 5), in comparison with the shallow well water in other areas of Taiwan, which ranged between nondetectable and 0.30 mg L^sup -1^ with a median of 0.04 mg L^sup -1^ (5). Tseng collected a series of more than 1600 cases...