Monday, May 6, 2013

Lead in rice?

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Last month, the BBC reported that US rice imports 'contain harmful levels of lead' (as published on 10 April 2013), followed by an article in Time Magazine, Worrisome levels of lead found in imported rice. Both cited research from Monmouth University that was pending publication in a scientific journal.
The topic got wide media coverage, yet the results were surprising to experts working in rice, including scientists at the International Rice Research Institute (IRRI).

Results under review

The BBC has since updated its article (still with the same title), but it now includes a critical new paragraph: “However, the results are preliminary and will be extensively reviewed prior to publication in a journal.” This reaffirms the work has not yet been published and that there is still a question mark over the validity of the data on the amount of lead reported to have been found in the rice samples.
Dr.Tsanangurayi Tongesayi, Associate Professor - Analytical and Environmental Chemistry at Monmouth University, and the researcher behind the work, explained, “We put our paper on hold pending the data verification exercise that we are carrying out.”
Some media outlets have followed up on this and published counter articles such as in Natural News, which delves into the topic in detail, Exclusive: Scientific paper that announced high levels of lead in rice suddenly retracted by its author and the Herald Online, Lead in rice study retracted; truth about heavy metals in rice revealed.
Dr. Tongesayi explained that the first method they used to analyze lead content was an XRF instrument, which he says is widely agreed to be an excellent method for analyzing total metal content 1. He explained that when they went to verify the amount of lead they had found in the rice using a different method they received very different results showing much less lead than originally recorded.
He said they were now doing more analyses using more than one method in an effort to get verifiable data on the amount of lead found in the rice.
“The most important issue for me at this point is to make sure the data is accurate,” Dr. Tongesayi said. “If it is not accurate we will obviously not publish the paper.”

Is rice safe to eat?

Previous research 2 , 3 , has shown that lead is not a significant concern for food safety of rice. Even where the soil is contaminated with a lead spill, a number of studies have shown that rice plants do not take up a significant amount of lead and move it to the grains. Human exposure to lead comes primarily through inhalation of exhaust fumes (in places where lead is still used in gasoline) or direct ingestion of lead-containing dust or paint.
IRRI supports the existing evidence that demonstrates that rice consumption is not considered a significant source of exposure to lead.


1. Palmer PT, Jacobs R, Baker PE, Ferguson K, and Webber S. (2009). Use of field-portable XRF analyzers for rapid screening of toxic elements in FDA-regulated products. J Agric Food Chem. 2009 Apr 8;57(7):2605-13.
2. Shimbo S, Zhang ZW, Watanabe T, Nakatsuka H, Matsuda-Inoguchi N, Higashikawa K, and Ikeda M. (2001). Cadmium and lead contents in rice and other cereal products in Japan in 1998-2000. Sci Total Environ. 2001 Dec 17;281(1-3):165-75.
3. Moon C S, Zhang ZW, Shimbo S, Watanabe T, Moon DH, Lee CU, Lee BK, Ahn KD, Lee SH, and Ikeda M. (1995). Dietary intake of cadmium and lead among the general population in Korea. Environ Res. 1995 Oct;71(1):46-54.