Environmental hypothesis: is poor dietary selenium intake an underlying factor for arsenicosis and cancer in Bangladesh and West Bengal, India?

To reduce the incidence of dysentery, cholera and other water-borne diseases and mortality of people drinking from surface contaminated sources of water, the World Bank and United Nations Children's Fund began to sink tube wells into the underlying aquifers of Bangladesh and West Bengal, India, in the 1970s. Many of the tube wells were drilled into underground aquifers that provided microbiologically clean water that was later determined to contain arsenic (As). As contamination of drinking water is a problem of natural occurrence throughout the world and domestic water often exceeds the World Health Organization limit of 50 microg As/l in the countries of Bangladesh, West Bengal, India and Nepal as well as other areas occupying much of the Ganges-Brahmaputra delta. It is estimated that as many as one-half of these tube wells discharge water with sufficient amounts of As to produce arsenicosis, i.e. As toxicity in the human population. Access to clean As free water is the priority of most organized relief efforts. Where As free domestic water cannot be provided, an improved diet and/or dietary supplements may ameliorate As toxicity or prevent its toxicity all together. The dietary status of the essential human trace element, selenium (Se) may be adversely affected by a chronic excessive ingestion of As. As added to animal diets has been known to counteract Se toxicity in animals since the 1930s. It is reasoned therefore, that high levels of chronic As ingestion from well water by people within the delta will accelerate the excretion of Se lowering the body's content of this essential trace element. Excessive Se excretion owing to Se/As complexation may add to the likelihood of As being more toxic and carcinogenic over time, due to the oxidative stress imposed by the excessive As and low Se ingestion. Because of the unique environment of the Ganges-Brahmaputra delta in which millions of people are presently exposed to As, we ask the question: are low dietary Se ingestion and accelerated Se depletion by As possible contributing factors to arsenicosis?