Published this month (22 July) in Scientific Reports by scientists from the Indian Institute of Chemical Biology (IICB), Kolkata, and the University of Manchester, the report shows that high levels of genotoxicity are associated with regular consumption of high arsenic rice.
The authors studied urothelial cells isolated from urine samples of more than 400 people in the Midnapore, Nadia and Murshidabad districts of West Bengal who drank water low in arsenic (less than 10 micrograms per litre).
The scientists found the number of micronuclei — a small nucleus that forms from chromosomal damage and is incorporated into daughter nuclei during cell division — to be higher in the cells of people who consumed high-arsenic rice (more than 200 micrograms per kilogram).
The authors say an increase in micronuclei leads to damaged DNA and that, while similar genotoxic effects have been observed in people exposed to high arsenic in drinking water, this is the first time it has been observed in people whose only source of arsenic is rice.
David Polya, professor of environmental geochemistry, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, and one of the authors of the report, stresses that rice was the cereal most susceptible to absorbing arsenic during cultivation.
"This is, in part, because of the nature of the cultivation method which involves flooding, which in turn produces reducing conditions under which inorganic arsenic occurs as arsenous acid and this is actively incorporated into the rice plant through structures known as aquaporins," Polya told SciDev.Net.
"Arsenic exposure can be reduced somewhat but not eliminated through appropriate cooking methods," says Ashok K. Giri, a scientist at the IICB. He recommends washing rice before cooking and using arsenic-free cooking water.
Aparajita Majumdar, a microbiologist working on arsenic mitigation through biological methods at Bidhan Chandra Krishi Viswavidyalaya, Nadia district, West Bengal, suggests that arsenic-resistant bacteria could play a crucial role in helping grow safer rice.
Such bacteria create reducing conditions in flooded rice fields and, thereby, oxidise arsenic and reduce its uptake by rice plants. "We are working on identifying such bacteria," she told SciDev.Net.
Link to article in Scientific Reports