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Issue 6
, 2007
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Wastewater irrigation make vegetables toxic: Study

Source: Statesman, Date: , 2007

Vegetables grown in semi-urban areas, which use industrial wastewater for irrigation, have high levels of heavy metals such as lead, which is neurotoxic brain and cadmium, which can cause cancer, according to a new study by Indian and UK scientists.

The study, carried out by researchers from the University of Sussex, Toxics Link (an NGO), Delhi University and Benaras Hindu University, established an “unambiguous relationship between heavy metals contamination in food crops and its source in wastewater from industries, treatment plants and municipal and domestic source.”

Scientists said that in a rapidly urbanising world, where there is increasing concern about fresh water shortage, the practice of using wastewater for irrigation of food crops in urban fringe (peri-urban) areas is encouraged.

One potential risk of wastewater use is the contamination of food as a result of industrial pollution. It can have serious implications for the health and livelihoods of those that consume produce that was grown with wastewater irrigation, and for the poor in particular.

“Wastewater, used for irrigation in India, has no standards for heavy metals, though standards for bacterial content are there,” Mr Ravi Agarwal from Toxics Link, said. Even if waste water is treated before being used for irrigation, 40-60 per cent of heavy metals remain in the treated water, he said.

“Lead was found to be high in almost all the samples as per the country’s own Prevention of Food Adulteration (PFA) standards,” he said and added that Indian standards are lax in comparison to European standards.

Another heavy metal, cadmium, was found high in 60 per cent of samples as per Indian standards. But according to European standards, the two heavy metals were at “alarmingly high levels” in the vegetable samples tested. In the current policy and practice, there is little recognition of the link between industrial pollution and food safety, Mr Agarwal said.

The study was carried out during 2003-2007 in three areas of Varanasi ~ Dinapur (in the vicinity of the city’s major sewage treatment plant), Shivpur (to the north east of the city, close to the Shivpur industrial area) and Lohta (to the west of the city close to several industrial areas).

The heavy metals sampled include zinc, lead, copper, cadmium, chromium, manganese and nickel. Of these, potentially the most toxic are cadmium and lead. These heavy metals are widely associated with many small-scale industries in Varanasi that include metal works, paper manufacturers and chemical and paint works. Vegetables such as spinach, radish, brinjal, cauliflower, tomato and cabbage were tested.