While groundwater is an important source of drinking water worldwide, contamination of groundwater sources is on the rise. Arsenic contamination of groundwater has been found to affect as high as 300 million people worldwide exposing them to a number of health risks.

Arsenic contamination of groundwater in India

India has been found to be one of the major arsenic hotspots along with other countries such as Taiwan, Chile, Mexico, China, Bangladesh and Argentina. Recently, a few cases have also been reported from Poland, Hungary, Japan, Canada and USA.

The paper 'Arsenic exposure in Indo Gangetic plains of Bihar causing increased cancer risk' published in Nature Scientific Reports, informs that Bihar, located in the Ganga-Meghna-Brahmaputra (GMB) basin faces severe problems due to arsenic contamination of groundwater.

Groundwater is the main source of drinking water and caters to more than 80 per cent of drinking source in rural Bihar, thus increasing the risk of population exposed to the risks due to arsenic.

Eighteen out of 38 districts in the state of Bihar have high arsenic contamination of groundwater. According to the Ministry of Water Resources, Government of India, 1600 habitations from 67 blocks of 18 districts of the states are severely affected with arsenic poisoning. This has caused threat to an estimated 50 million population of the state out of which 13.85 million people are drinking arsenic contaminated water above the WHO/BIS permissible limit of 10 μg/L.

Why is arsenic so dangerous?

Arsenic is very toxic in high doses. Inorganic arsenic through drinking water reaches the blood through gastrointestinal tract, is converted into organic form. Arsenic remains in the blood for 2 to 6 hours and gets deposited in the skin, hair and nails causing keratosis, melanosis, rain drop pigmentation or other skin manifestations. It also affects the vascular systems and the nervous systems.

Acute poisoning can occur due to excessive arsenic in the body leading to vomiting, diarrhoea, abdominal pain, general body weakness, vertigo, nausea, muscle cramps etc. It can also lead to peripheral neuropathy, renal failure, gastrointestinal disruption, hypertension, diabetes, conjunctivitis, anaemia, loss of appetite, breathlessness, mental disability, hormonal imbalances, suppression of bone marrow and cardiovascular diseases.

In extreme cases, entry of arsenic into the body over long durations can lead to life threatening diseases like cancer of the skin, bladder, lungs, kidney, liver, and prostate.

Very few studies have found the correlation between increased incidence of cancer and drinking water contaminated with arsenic. While increasing cases of cancer are being detected in Bihar, there is very little evidence of its correlation with arsenic contamination of water. This study attempts to decipher the root cause of the cancer incidences in the Gangetic basin of Bihar and its association with arsenic.

The study was conducted at Mahavir Cancer Sansthan and Research Centre, Patna, Bihar. Two thousand cancer patients were identified and their blood samples were collected for the study along with 200 blood samples of subjects free of cancer from arsenic free pockets of Patna urban agglomeration, for a case control study. Distribution of cancer patients by districts with cancer types was also plotted using GIS mapping.

The study findings

• The study found very high incidence of cancer in the arsenic prevalent Gangetic basin. Most of the cancer cases reported were from the cities or towns which were located near the river Ganga. The study found that districts located near the course of Himalayan bound river basins had more incidences of cancer in comparison to non-Himalayan river basins.
• Majority of the cancer cases were from the districts of Buxar, Bhojpur, Saran, Patna, Vaishali, Samastipur, Munger, Begusarai and Bhagalpur.

• Consumption of arsenic contaminated groundwater and food led to major health issues in the population and long duration exposure led to cancer.
• The most common cancers found were skin cancer, skin melanoma, lung cancer, bladder cancer, hepatobiliary cancer, renal cell carcinoma, breast cancer, ovarian cancer, endometrium cancer. These were found with other typical symptoms of arsenicosis indicating that there was a significant correlation with the arsenic.
• Cancer types like carcinomas were found to be more aggressive than the other types like leukemias, lymphomas and sarcomas.

This study found that people living in the Gangetic basin are getting exposed to the continued arsenic toxicity leading to the development of several types of cancers. The paper argues for the need to have more systematic studies to understand the molecular mechanisms of arsenic toxicity in cases of cancer and its progression, and to establish the correlation by understanding the signaling pathways for arsenic exposed human cancer.

This will greatly help in devising measures to prevent people from drinking arsenic contaminated water by looking for alternative sources of water and also help in developing an improved therapeutic approach, argues the paper.