New Delhi: An analysis of arsenic-contaminated rice from the US, China, India, Australia and Europe reveals that though the American varieties had far more arsenic than the Indian varieties, they were much less toxic, according to a new study by the University of Cornell.
As a result, the study argues that mere reduction of arsenic content in rice isn’t enough. Instead, it suggests, the rice varieties must be bred such that they convert the inorganic form of arsenic to its organic variant, which is believed to be far less toxic and excreted more rapidly by a human being.
The study suggests that Indian rice varieties have more inorganic arsenic content while American rice has more of the organic variant, which is less harmful to human beings (Photo by: AFP)
“Previous studies have said that US rice varieties are in general more dangerous than the Asian ones simply because it contained 1.5-4 times the arsenic in Indian varieties,” said Yamili Zavala, one of the authors involved with the study in a statement, “but most of this extra arsenic is of the organic, much-less toxic variety.”
There might be some genetic factors, Zavala added in an email to Mint, that’s making the inorganic arsenic, organic. “But we don’t understand this conversion process yet and so yet don’t know which genes are responsible,” she added.
The Bangladeshi and Indian varieties of rice, according to the authors, have more inorganic content. They emphasize that as of now all the studies that describe the carcinogenic nature of arsenic involve the inorganic variety.
Though the World Health Organization has specified safety limits for the arsenic content in water, it doesn’t have similar standards for arsenic content in rice.
“The only standards we have are what the Chinese have set,” said John Duxbury, also involved with the study, “and that’s a maximum of 0.15 microgram of arsenic per gram of grain.”
In the last most comprehensive survey in 2005 that compared rice grains from across the world, Andrew Meharg of the University of Aberdeen in the UK tested rice bought from markets in Aberdeen that had been grown in America, Europe, India and Bangladesh. He found, per grain of rice, an average of 0.26 microgram of arsenic in each gram of US rice. Indian rice hit a low of 0.05 microgram per gram, whereas Bangladesh, which has had recurring problems with arsenic contamination owing to naturally high levels of the poison in groundwater, and Europe had about 0.15 microgram per gram. The results are published in the journal Environmental Science and Technology.
Ground water that is contaminated by arsenic is a well-documented health hazard in West Bengal and, experts add, is even spreading to Uttar Pradesh and Bihar.
A prolonged intake of arsenic is significantly associated with a host of cancers, such as skin and lung cancer, and cardiovascular disease. In West Bengal, long-term arsenic poisoning has typically resulted in skin lesions, neurological problems, pre-natal deaths and, in many cases, gangrene leading to amputation, says Dipankar Chakraborti, director of research at the School of Environmental Studies, Jadavpur University. He claims almost 15 million people across the state are arsenic-threatened.
As reported by Mint in October, scientists in West Bengal have embarked on a five-year project which, among other things, would develop new types of rice that would absorb less arsenic.
The way to getting around the arsenic-contaminated food crop would be to identify crucial genes responsible for the uptake of soil ingredients such as minerals, water—and the arsenic. “That’s a five-year project and at the end of it, we only hope to find these genes. Making them work, and develop subsequent varieties out of them is an altogether different ball game,” said one of the scientists involved with the project who requested anonymity, as he was unauthorized to speak to the media.