Groundwaters with arsenic concentrations higher than the WHO provisional guide value of 10 μg/L are found in many parts of the world.
Widespread utilization of these groundwaters for drinking, irrigation of food crops and cooking over the past few decades
has resulted in chronic exposure to tens of millions of people, annual excess deaths of the order of thousands and annual
DALYs of the order of hundreds of thousands in Bangladesh, the worst impacted country. Chronic exposure to arsenic may result
in a wide range of cancerous and non-cancerous deleterious health impacts; particularly for cancers, these health impacts
may not manifest themselves until decades after the exposure. Many health end-points are non-fatal but nevertheless result
in considerable loss of quality of life. Calculation of arsenic-attributable DALYs is therefore important to inform policy-makers.
Assessing the overall risk of utilization of arsenic-bearing groundwaters may be achieved, in principle, by quantifying (1)
dose–response relationships; (2) exposure routes; and (3) groundwater arsenic hazard.
There is a clear association between chronic arsenic exposure and various cancers, particularly skin and lung cancers, at
drinking water concentrations above 100 μg/L but there is considerable argument over the nature of dose–response relationships
at concentrations much below this. Nutritional status, including intake of selenium and folate, genetic disposition, smoking
habits, age and gender are all contributory factors to the risk of acquiring arsenic-related diseases as a result of a given
chronic exposure.
The major exposure routes for arsenic from groundwaters are: (1) drinking groundwater; (2) eating rice and other food-crops
irrigated with groundwater; and (3) indirectly through cooking rice with high arsenic groundwater.
Assessing the impact of various arsenic remediation options needs to explicitly consider potential risk-substitution and,
in particular, the balance between DALYs arising from arsenic-related health impacts and those related to water-borne pathogens.