Arsenic from irrigation water entering food chain in Bihar: Study
Arsenic from irrigation water is entering the food chain in the arsenic-affected villages of Bihar. This has resulted in food with higher arsenic content than drinking water, a study by British Council and Union science ministry has found. It is the first time a study has found arsenic in locally grown food items – rice, wheat and potato – even though the presence of the chemical in groundwater was known for years. As many as 22 of the 38 districts in the state have an arsenic level above the World Health Organisation (WHO)’s permissible limit of 10 micrograms/ litre.
Bihar is the second most affected Indian state with arsenic contamination after West Bengal. Arsenic is naturally present in groundwater. In all, nine states in India are affected by arsenic groundwater contamination.
“The findings are alarming,” said Ashok Kumar Ghosh, chairman of the Bihar State Pollution Control Board (BSPCB) and a member of a 12-member team that conducted the study.
He said for the first time, they have evidence that there is arsenic in food and its quantity was higher than that found in drinking water. Such is the vicious circle that water used to cook food adds to arsenic content resulting in cooked rice having higher arsenic than in raw paddy.
“We all have been focusing on the presence of arsenic in groundwater. Irrigation water was hitherto untouched. But our study has confirmed the presence of arsenic in the food chain in Bihar through irrigation water,” he said.
The reason for arsenic in food is that irrigation is dependent on shallow tube wells hardly 30-70 feet deep. Arsenic is present more in shallow water. Arsenic in water used by Shivshankar Prasad, a farmer of Bichoo Ka Dera village of Buxar district, is 336.2 micrograms/litre. In the case of fellow villager Kamlesh Yadav, it is 574.6 micrograms/ litre. The reason for this difference is that Yadav’s handpump is shallower than Prasad’s. And that is the reason Ghosh said that the only solution to the problem is deeper tube wells.
Quoting the study, he said, rice, wheat and potato have elevated levels of arsenic that can increase the disease burden of the exposed persons.
The study was conducted in 19 villages of arsenic affected districts. Ghosh said the study was exhaustive and is based on the detailed dietary assessment and estimation of arsenic in drinking water, cooked rice, wheat flour and potato collected from 91 households covering 19 villages. If the study is implied to all arsenic impact areas, around 10% of the state’s population may be consuming arsenic-contaminated food.
The study was funded by British Council and was recently published in the journal Science of the Total Environment.
Ghosh said that the study found that the presence of arsenic in the food chain was more pronounced in districts situated on the southern bank of Ganga such as Buxar, Bhojpur, Patna and Bhagalpur than those situated on the northern bank such as Vaishali, Naugachia, etc.
According to the study, the effects of high arsenic content is an increase in lifetime cancer risk, skin diseases like Keratosis, Melanosis and Bowen’s disease, etc.
“We focused on rice, wheat and potato because cereals, followed by vegetables and milk, form a staple diet of the rural Bihar. This is the first study where a detailed dietary assessment was conducted on arsenic exposed populations of Bihar to estimate the arsenic exposure from the three major staple foods,” he said.
The study also found that at least 77% of the surveyed households had an arsenic concentration in drinking water below the WHO guideline value of 10 micrograms/ litre. At least 37% of households reported some form of improved water for drinking, indicating that a significant proportion of drinking water in the studied population may have had arsenic levels lower than 10 micrograms/ litre, the study said.
In the homes, where arsenic in drinking water was within the WHO limit, the study found that the overall arsenic exposure was 36%, showing that the source of the chemical was water used for irrigation. The study concluded that arsenic in food was higher than in drinking water.
Ghosh said that although there is no fixed WHO guideline on the normal value of arsenic in food, the food had more arsenic content than drinking water. He said this was even when arsenic levels in drinking water were above the WHO provisional guide value of 10 micrograms/ litre.