Arsenic naturally occurs in water, soil and rocks, but its levels may be higher in some areas than others. It readily enters the food chain and may accumulate in significant amounts in both animals and plants, some of which are eaten by humans.
As a result of human activities, arsenic pollution has been rising. The main sources of arsenic pollution include certain pesticides and herbicides, wood preservatives, phosphate fertilizers, industrial waste, mining activities, coal burning and smelting.
Arsenic often drains into groundwater, which is heavily polluted in certain parts of the world. From groundwater, arsenic finds its way into wells and other water supplies that may be used for crop irrigation and cooking.
Paddy rice is particularly susceptible to arsenic contamination, for three reasons:
- It is grown in flooded fields (paddy fields) that require high quantities of irrigation water. In many areas, this irrigation water is contaminated with arsenic.
- Arsenic may accumulate in the soil of paddy fields, worsening the problem.
- Rice absorbs more arsenic from water and soil compared to other common food crops.
Using contaminated water for cooking is another concern, because rice grains easily absorb arsenic from cooking water when they are boiled.