The amelioration of arsenic toxicity in Fischer 344 rats supplemented with selenite in the diet

Prior to the early 1970s, the people in rural areas of Bangladesh and West Bengal, India, where sanitary drinking water is scarce, had no ahemative to drinking severely polluted surface water (Henry 1990). During the 1970s, United Nations Intemational Children's Fund (UNICEF) fimded the digging of tube wells, which were to supply clean drinking water to the people from underground sources (Guha Mazumder 1998).

In 1993, 10-20 years after the first wells were dug, people began developing unusual symptoms: hyperpigmentation of the skin on unexposed areas of the body, thickening of the pahns of the hands and soles of the feet, skin lesions (both malignant and benign), and ahered hver, nerve, gastrointestinal, and/or lung fiinction (Guha Mazumder 1998). These symptoms are all characteristic of chronic arsenic (As) toxicity. Testing water samples from the tube wells determined the water contained levels of As from less than 3 ppb, which is virtuaUy arsenic free, to over 1000 ppm (Chowdhury 2000), well above the tolerable hmits set by World Heahh Organization (WHO) (50 ppb) (Smith 2000). It has been estimated that 120 milhon people in Bangladesh and West Bengal have been exposed to unsafe levels (greater than or equal to 50 ppb) of As as a result of obtaining it in the drinking water from these wells (Chowdhury 2000).

Attempting to alleviate the situation, WHO has ftinded many research projects (Anstiss 2001), mcluding those designed to remove As from the water, cheaply and effectively, as well as projects aimed at counteracting As toxicity in vivo. In the past, research has shown that As may amehorate selenium (Se) toxicity (Levander 1966b); As may act synergistically with Se (Obermeyer 1971); or Se may counteract As toxicity (Babich 1989). The objective of this study was to determine if Se counteracts As toxicity in rats.

The first phase of research was designed to detennine two effects: the tolerable upper limit (TUL) of As as 50% arsenite/ 50% arsenate in Fischer 344 rats and the effects of dietary Se supplementation on As toxicity. Fourteen groups of 6 rats were given 0, 25, 50, 100, 150, 175, or 200 ppm As in the water and 0.2 or lOppm Se in the food. After evaluating the data from the first phase, a second phase was conducted to determine a level of Se suitable for amehorating As toxicity in rats at the TUL (50 ppm). Nine groups of 6 rats were given 0 or 50 ppm As in the drinking water and either 0, 0.2, 1.25, 2.5, or 5ppm Se in their food. The Se deficient diet (0 ppm Se) was introduced to mimic a potential Se deficient diet in Bangladesh or West Bengal (J. SpaUholz, personal communication, March 27, 2002).

This study provides insight into the effects of Se supplementation on As toxicity, as well as demonstrates the TUL of As in rats. Once analyzed and summarized, the results of this study will be beneficial to those conducting ftirther research in As toxicity.