Arsenic Again.

A Continuing Threat in Chile

Arsenic poisoning is serious business. Chronic exposure to high doses of the element in drinking water increases the risk of vascular diseases and skin, lung, and bladder cancers, and may be associated with diabetes mellitus. In addition, although less attention has been accorded to the effect of arsenic on reproduction, teratology in animals is well documented. In this month's issue, Claudia Hopenhayn-Rich of the University of Kentucky in Lexington and colleagues present findings concerning reproductive effects of arsenic in drinking water in two areas of Chile, and Allan H. Smith of the University of California at Berkeley and colleagues present findings concerning arsenic-induced skin lesions in a study of indigenous people who have resided in northern Chile for many centuries [EHP 108:667-673; 617-620].

Hopenhayn-Rich's study compared infant mortality rates in two areas of Chile, Antofagasta (north) and Valparaiso (central). Antofagasta experienced a 12-year period of substantially high arsenic concentration in its drinking water starting in 1958, when the city incorporated the Toconce River as its main drinking water source. The geologic, natural sources of the element in the river drove drinking water arsenic concentrations to as high as 860 micrograms per liter ([micro]g/L). This was largely remedied with the 1970 installation of an arsenic removal plant; today, the concentration is around 50 [micro]g/L. Valparaiso, on the other hand, does not have any recorded history of elevated arsenic in drinking water.

The authors used several statistical methods to examine the effects of time and location on the infant mortality trends observed between 1950 and 1996. The data indicate general declines in late fetal and infant mortality in both Antofagasta and Valparaiso over time, probably because of other nonarsenic-related factors such as improvements in health care and standard of living that affected all the regions in Chile. However, the data also show elevations in late fetal, neonatal, and postneonatal mortality rates for Antofagasta compared with Valparaiso for a defined period of time reflecting the rather sudden and sharp rise in the concentration of arsenic in the city's public water supply.

Hopenhayn-Rich and colleagues point out that although there is suggestive evidence for the developmental effects of arsenic, a clear causal association cannot yet be established, although their findings of increased late fetal, neonatal, and postneonatal mortality rates lend further support to previous studies. The authors stress the need for further studies using individual-level data, well-designed methods of exposure assessment, and collection of data on potential confounders to examine a broad range of reproductive and developmental end points.

Smith's study focused on the village in Chiu Chiu in northern Chile, where the native Atacameno people, who have inhabited this extremely and region for more than 9,000 years, drink water from rivers originating in the Andes Mountains. Many of these rivers contain high concentrations of inorganic arsenic; concentrations of arsenic in the drinking water can reach as high as 800 [micro]g/L. Despite this fact, some earlier reports had suggested that the Atacameno were less affected by arsenic than other exposed populations, giving rise to the theory that centuries of exposure had built up their resistance to the effects of arsenic, including characteristic skin effects such as dark brown spots, darkening of skin on the limbs and trunk, and keratoses on the palms of the hands and soles of the feet.

The scientists selected 11 families of Chiu Chiu likely to have the greatest exposure to arsenic, as determined by factors including age of family members, how long they had lived in the area, and principal source of drinking water. A total of 45 people underwent skin exams by four different physicians. Six were found to have definite arsenic-induced skin effects, including 4 men with over 20 years of exposure to arsenic, 1 boy, and 1 girl. These prevalences are similar to those reported in studies in Taiwan and West Bengal. Furthermore, despite evidence from those studies that malnutrition might increase susceptibility to the effects of arsenic, the people of Chiu Chiu eat a wide range of fruits and vegetables and, on the average, consume red meat and chicken at least once a week. Women fared better, however, with no incidences of skin effects, for reasons still unknown.

The authors conclude that arsenic-induced skin effects persist among the Atacameno despite good nutrition and thousands of years of potential exposure. They recommend providing low-arsenic water to this population and note that as an interim solution the people of Chiu Chiu are now receiving water from the town of Calama, where the arsenic concentration has been lowered through treatment to 45 [micro]g/L.