Vivian Grisogono


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On 24th March 2007, the UK press reported a study by researchers from Aberdeen University, which showed that rice cultivated on former cotton fields in the USA’s south central states, Arkansas, Louisiana, Mississippi, Missouri and Texas, contained high levels of arsenic, up to five times higher than arsenic levels in rice samples from California and other parts of the world. These raised levels gave rise to worries about increased risks of bladder and lung cancer.

China had recently imposed a safety limit for arsenic contamination of 0.15 mg per kilogram of rice, whereas the UK and Europe allowed 1 mg per kilo. Professor Andy Meharg, who led the research, suggested that the European level should be reduced to the Chinese level, to take account of research showing the effects of long-term arsenic consumption.

Professor Andrew Meharg had published a previous study in “Environmental Science and Technology”  (2nd August 2005, authors Williams P N et al, online). It was thought then that when rice was first cultivated in former cotton fields, the crops failed because of a disease called “straight-head”, which was caused by arsenic residues. Straight-head resistant varieties were then bred, but these were possibly more likely to accumulate arsenic within apparently healthy grains.

Arsenic occurs naturally in soils, in two forms: the less dangerous is ‘organic’, in which arsenic atoms are bound up with carbon-based molecules, while the ‘inorganic’ form, found in drinking water, is known to be more harmful. There is, naturally, debate about exactly how harmful, if at all, the arsenic contamination in rice crops might be.

Professor Meharg is convinced that there is a specific danger caused by growing rice in former cotton fields.