There is arsenic in some of our groundwater—a worrying thought at a time when groundwater is being used for drinking, irrigation and cooking in villages and towns where access to treated water through government-laid pipes is limited.

Groundwater is considered a comparatively clean and uncontaminated source. In effect, however, the practice has led to the “largest-scale mass poisoning in history," says S. Vishwanath, a water quality expert and adviser, Arghyam, Bengaluru. Arghyam is a grant-making foundation that focuses on issues of groundwater and sanitation.

According to a report released last month by the Union ministry of drinking water and sanitation, as many as 46 million people in India are exposed every day to contaminated water. Arsenic, fluoride, iron or nitrate contaminate water in 78,508 rural habitations. Arsenic poisons the water in 1,991 of these habitations, adds the report.

The World Health Organization recommends that water for drinking and irrigation should have less than 50 parts per billion (ppb) of arsenic to be considered safe. According to the Arghyam website, around 13 million people across eight states are exposed to arsenic contamination that is greater than 50 ppb: West Bengal, Bihar, Uttar Pradesh, Jharkhand, Uttarakhand, Chhattisgarh, Assam and Odisha. “The number of Indians affected by arsenic contamination ranges between 12-100 million, depending on which expert you talk to," says Vishwanath.

There are two forms of arsenic, organic and inorganic—the latter is considered more poisonous. Countries like India and Bangladesh naturally have a higher level of inorganic arsenic in their minerals and rocks. Long-term exposure to inorganic arsenic can lead to arsenicosis, with symptoms including disfiguring skin lesions, cardiovascular disease and reproductive disorders, including an increased likelihood of stillbirths, according to a 2013 Unicef position paper, Arsenic Contamination In GroundWater. Studies show that children are particularly vulnerable; arsenic can inhibit their intellectual development. Arsenic can also cause bladder and lung cancer—the International Agency for Research on Cancer has classified it as a carcinogen.

While it is known that India has higher levels of inorganic arsenic in its rocks and groundwater, we don’t know which parts of the country, apart from the states in the Gangetic belt, are affected.

The Himalayan rocks contain inorganic arsenic and the Ganga river absorbs this as it flows down to the plains. “There probably are other areas of the country that are similarly affected, but we don’t know much about them," says Chetan Malhotra, research team leader, new solutions, Tata Research Development and Design Centre (TRDDC), Pune. The TRDDC, a research centre established in 1981 by information technology company Tata Consultancy Services, has developed Swach, a low-cost water purifier. Malhotra’s team is now working on a low-cost purification device that removes arsenic from groundwater.

While people who live in cities and have access to pipe water may believe they need not worry about arsenic, that may not be true. Since arsenic-laced water is used for irrigation, the food crops that grow in it can and do get contaminated.

The good thing is that most grains don’t absorb enough arsenic to be a health concern. Rice, however, is one grain that does. It absorbs arsenic in its shoots, and since it’s grown in flooded conditions, the absorption is even greater.

There are a few ways to minimize exposure to arsenic. If you’re having rice, make sure it is washed and use a ratio of six cups of water to one cup while cooking. Also, remember to drain the excess water before eating the rice. The washing and draining remove a substantial amount of arsenic.

Last year, researchers from Okayama University, Japan, University of Zurich, Switzerland, Pohang University of Science and Technology and Kyung Hee University, South Korea, published their discovery of a transport molecule in the rice plant that makes arsenic less toxic and also reduces its uptake into the grain. The findings were published in the Proceedings Of The National Academy Of Sciences in November. Using this knowledge, researchers will one day be able to genetically engineer a variety of rice that absorbs negligible quantities of arsenic.

Meanwhile, if rice is the main grain in your diet, consider switching to a multigrain diet; that will be better for your overall health anyway.

Sujata Kelkar Shetty, PhD, is a wellness consultant, life coach and former clinical research scientist trained at the National Institutes of Health in Bethesda, USA.