Controversy flares over rice research

A widely quoted 2005 ES&T paper reporting high levels of arsenic in U.S. rice has drawn a strong response from the USA Rice Federation. On the federation’s website, a commentary dated August 9, 2005, and removed February 1, 2006, labeled the paper “maliciously untrue” and “inaccurate in the highest degree”.

The paper, from corresponding author Andrew Meharg of the University of Aberdeen (U.K.), reported that 7 samples of U.S. rice purchased in supermarkets in Aberdeen had an average of 0.26 µg As/g of rice. The World Health Organization’s provisional value for a maximum tolerable daily intake of inorganic arsenic is 2 µg/kg bodyweight/day.

The authors suggest that the high levels of arsenic in the rice are a legacy from the days when arsenical pesticides and herbicides were applied to cotton growing in the same fields now used for rice. Meharg found that the arsenic in U.S. rice was mainly in the organic form, which is less worrisome than inorganic arsenic.

“The primary intent of the original article was to establish baseline data for arsenic levels and speciation in Bangladeshi rice, by comparing it with other rice-growing regions, and to see if there was genetic variability in grain levels and speciation,” Meharg says. In the 3 studies of U.S. rice that Meharg cites in the ES&T paper, average arsenic levels in rice were 0.24–0.30 µg/g, whereas in 18 studies of Bangladeshi rice, the averages were 0.10–0.95 µg/g.

However, a very different message was delivered to the media, says David Coia, vice president of communications with the USA Rice Federation. Meharg’s research was highlighted in a broad range of publications, including Nature and the newspaper USA Today. “It’s important, I think, to know who picked up this article and why they picked it up and what their perspectives were when they read it,” Coia points out.

The news coverage focused on the arsenic levels of the 7 samples of U.S. rice bought in Aberdeen supermarkets, says Coia. “It presents all U.S. long-grain rice in a negative light.” He argues that most reporters based their stories on only the paper’s abstract, which, according to Coia, drew attention to the U.S. rice data. The reporters “didn’t look at this article, didn’t read it.”

In its response, Enough Nonsense about Arsenic Already!, the federation says that the sample numbers are too small and that its own proprietary data show much lower arsenic concentrations. Coia even speculates that, despite the labels, the tested samples may not actually have been from the U.S.

Although the authors said nothing in their ES&T paper about the health effects of consuming the grain, Nature reported that Meharg had decided to stop eating U.S. rice.

Meharg labels the USA Rice Federation’s response as “insulting”. He says the paper’s authors were surprised at the levels of arsenic in their U.S. rice samples, but he counters: “We found our results [to be] entirely consistent with previous studies... . The 3 other independent studies that I know of on U.S. rice had a [combined] sample size of 50, and our sample of 7 was entirely in agreement with this,” he adds. “These studies are in refereed academic papers, including one recently published in ES&T. ” The new ES&T study reports 0.24 µg/g total arsenic in 2 commercially obtained samples of U.S. long-grain rice. “Also, they were all U.S. market-based surveys, not a U.K. survey like mine.”

Richard Loeppert at Texas A&M University points out that more research is needed because “arsenic concentration and speciation in rice is extremely variable, whether in South Asia or the U.S.” Coia agrees, adding, “I think [the studies] need to be done in a comprehensive way.”

However, Meharg argues that the industry bears some responsibility for the arsenic concern. “By not addressing this problem [of arsenic] that has been ignored for decades, the U.S. cotton-belt rice industry is doing itself an injustice,” warns Meharg. “Had the problem been addressed in the past, given that it is well known that arsenic in paddy soils was a problem in the U.S.... safe soils would have been identified and low grain arsenic rice varieties developed.” —BARBARA BOOTH