Arsenic (As) is a common, naturally occurring drinking water contaminant, that originates from As-containing rocks and soil and is transported to natural waters through erosion and dissolution. Chronic As poisoning has become a worldwide public health issue. It is estimated that more than 130 million people from Asian countries have been potentially exposed to As contamination above World Health Organization (WHO) guideline value of As in drinking water (10 µg 1−1). Epidemiologic data from regions of the world with very high levels of As in drinking water (>150 µg/L) show a strong association between As exposure and risk of several internal cancers. Most human As exposure occurs from consumption of drinking water containing high amounts of inorganic As. Chronic effects of As exposure via drinking water include skin lesions, neurological effects, hypertension, peripheral vascular disease, cardiovascular disease, respiratory disease, diabetes mellitus, and malignancies including skin cancer.