Chronic Arsenic Exposure and Risk of Infant Mortality in Two Areas of Chile

Article excerpt

Chronic arsenic exposure has been associated with a range of neurologic, vascular, dermatologic, and carcinogenic effects. However, limited research has been directed at the association of arsenic exposure and human reproductive health outcomes. The principal aim of this study was to investigate the trends in infant mortality between two geographic locations in Chile: Antofagasta, which has a well-documented history of arsenic exposure from naturally contaminated water, and Valparaiso, a comparable low-exposure city. The arsenic concentration in Antofagasta's public drinking water supply rose substantially in 1958 with the introduction of a new water source, and remained elevated until 1970. We used a retrospective study design to examine time and location patterns in infant mortality between 1950 and 1996, using univariate statistics, graphical techniques, and Poisson regression analysis. Results of the study document the general declines in late fetal and infant mortality over the study period in both locations. The data also indicate an elevation of the late fetal, neonatal, and posmeonatal mortality rates for Antofagasta, relative to Valparaiso, for specific time periods, which generally coincide with the period of highest arsenic concentration in the drinking water of Antofagasta. Poisson regression analysis yielded an elevated and significant association between arsenic exposure and late fetal mortality [rate ratio (RR) = 1.7; 95% confidence interval (CI), 1.5-1.9], neonatal mortality (RR = 1.53; CI, 1.4-1.7), and posmeonatal mortality (RR = 1.26; CI, 1.2-1.3) after adjustment for location and calendar time. The findings from this investigation may support a role for arsenic exposure in increasing the risk of late fetal and infant mortality. Key words, arsenic, Chile, drinking water, infant mortality, neonatal death, reproductive effect, stillbirth. Environ Health Perspect 108:667-673 (2000). [Online 6 June 2000] /108p667-673hopenhayn-rich/abstract.html

Arsenic is a naturally occurring element that is present in the environment in both organic and inorganic forms. Human exposures to the more toxic inorganic arsenic compounds result from exposures in occupational settings, such as metal smelting and pesticide production, as well as from medicinal treatments and environmental sources (1,2). The use of drinking water with elevated arsenic concentrations, primarily from natural contamination, has been the main source of environmental exposures in populations worldwide, including but not limited to communities in Taiwan (3), India (4), Bangladesh (5), Thailand (6), Mexico (7), Chile (8), Argentina (9), China (10), and Hungary (11). In the United States, it is estimated that 350,000 people obtain their drinking water from sources containing [is greater than] 50 [micro]g/L arsenic, the current maximum contaminant level (MCL) set by the U.S. Environmental Protection Agency (EPA) (12). Although higher exposures are more common in western states, recent concerns have also focused on other geographic regions where private well use is common. In areas where arsenic has been more extensively measured, levels are near the EPA MCL (12) or the World Health Organization recommended guidance values of 10 [micro]g/L (e.g., Minnesota, New Hampshire, and Michigan) (13-15).

Chronic arsenic exposure at high doses has neurologic, dermatologic, vascular, and carcinogenic effects (1,2,15,17). Exposure to arsenic from drinking water increases the risks of skin, lung, and bladder cancers (18-20), and also seems to be associated with diabetes (21,22).

The possible impact of arsenic on reproductive effects has been given less attention, but the collective evidence from human and laboratory studies suggests the potential for adverse effects on several reproductive end points. Studies have reported adverse reproductive impacts among the offspring of employees and nearby residents of a Swedish copper smelter where arsenic exposures were documented (23-26). …