Arsenic Toxicity: Contamination Through Groundwater and Food Chain and Role of Genetic Factors

Groundwater is one of our most precious natural resources. Many aquifers around the world have been found to be naturally contaminated with arsenic (As), a toxic metalloid and a potent human carcinogen. Chronic exposure to arsenic is harmful to human health causing skin lesions, hepatotoxicity, vascular disease, diabetes as well as cancers of various organs. High concentrations of arsenic in groundwater, more than the permissible limit (10 µg/L as per World Health Organization, WHO) have been reported from many countries of Asia, Africa, Europe, North and South America and Australia. Around 200 million people, majority of them living in South and South-East Asia, are at risk of arsenic toxicity mainly from contaminated groundwater. Minerals, such as pyrites and arsenopyrites, have a high amount of arsenic content and release it in groundwater upon breakdown under oxic environment. Several hypotheses, such as, pyrite oxidation, iron reduction, competitive exchange and geomicrobial process, have been proposed to elucidate the release mechanism and mobilization of arsenic from sediment to groundwater. Use of groundwater laden with high concentrations of arsenic for irrigation of agricultural crops and entry of arsenic in food chain including crops has been the subject of intense research in the last decade. Some recent reports on the assessment of population’s dietary intake suggest that rice and water are significant sources of arsenic. Induction of an oxidative stress through the generation of reactive oxygen species is one of the principal mechanisms of arsenic toxicity. These reactive oxygen species results in DNA damage, lipid peroxidation and loss of antioxidant defense and induction of stress response genes. Polymorphisms in the arsenic metabolism and detoxification, antioxidant defense and DNA repair genes could also contribute to the inter-individual differences in arsenic biotransformation and consequently, influence inter-individual susceptibility to the health effects of arsenic toxicity.