Unsure where it's coming from, it's nearly impossible to regulate.
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Fifty years ago, Rachel Carson revealed in Silent Spring how toxic chemicals, like DDT, work their way from soil and plants into animal and human bodies. Her book was a call to action against the continued, unchecked addition of poisons to the environment.
Last week, Consumer Reports published findings of "worrisome" levels of arsenic in ordinary rice sold in the U.S. Arsenic contamination affected a variety of rice forms: brown and white, organic and regular, long and short-grain. The researchers found arsenic in dozens of commercial products including baby food, cereals, rice cakes and rice drinks. The FDA reported similar results in an initial statement released last week and is pursuing further studies of the matter.
Arsenic is a common, naturally-occurring element. The metalloid substance, famous for its tasteless, odorless and occasionally lethal properties, sits at number 33 in the periodic table. Arsenic arises in both organic and inorganic forms. One source of organic, dietary arsenic is seafood, particularly shellfish. Most studies of arsenic's toxicity have focused on its inorganic forms, including lead-arsenate, used in U.S. pesticides until the 1980s, and other chemical preparations still used in fertilizers, wood treatment and for other purposes today.
"The results came as no surprise," said Keeve Nachman, a researcher at the Johns Hopkins Center for a Livable Future. Arsenic is ubiquitous, he said, and it, derives from both natural and man-made processes. Because rice is grown in watery fields, it's prone to absorbing chemicals from groundwater. "The new analysis is important because it was the first to look closely at arsenic in a 'market basket' sample," he said.
Consumer Reports found that brown rice consistently had higher levels of arsenic than white rice of the same brand. This pattern might be explained by the polishing process in white rice manufacturing, which removes the outer grain layers. The bran removed in the milling process contained high arsenic levels, according to the report.
They also determined that white rice produced in the south-central U.S. -- in Arkansas, Louisiana, Missouri and Texas -- has higher levels of arsenic than similar products from California, Thailand and India. Some investigators have suggested that arsenic in rice from the cotton belt region is attributable to past use of arsenic-containing pesticides to control boll weevils.
The analysis provides a detailed table on total arsenic, in parts per billion, and inorganic arsenic, translated to micrograms per serving, for dozens of brand-name rice products ranging from Kellogg's Rice Krispies (relatively low, 2.3 - 2.6 micrograms arsenic/serving) to Trader Joe's Organic Brown Pasta Fusilli (relatively high, 5.9 - 6.9 micrograms arsenic/serving). The organization offers dietary recommendations for children and adults who might want to limit potential exposure to arsenic from rice.
"The take home point for consumers is to be concerned," says Michael Hansen, a senior scientist at Consumer Reports. "People should be aware of the levels they're eating and try to moderate their intake."
Apart from measuring arsenic in rice, the Consumer Reports group used a federal database, the National Health and Nutritional Examination Survey (NHANES), to establish that eating rice was associated with a significantly higher level of arsenic in urine. The NHANES work was carried out apart from the Consumer Reports research, so it's unlikely that participants' responses were influenced by concern about arsenic. Those who reported having eaten rice, and not shellfish (another potential source of dietary arsenic), on the day before the study had a 44 percent elevation in urine arsenic, overall, as compared to those who hadn't ingested either. Mexicans, other Hispanics, and Asians were most affected.
There's little doubt that arsenic causes disease. Arsenic is implicated in malignancies including skin, bladder and lung cancers. Both the National Toxicology Program and the International Agency for Research on Cancer list arsenic and inorganic arsenic compounds as human carcinogens. Short of causing cancer or death, chronic arsenic poisoning can lead to neuropathy, heart problems and kidney failure.
A problem that stymies environmental oncologists -- and extends beyond the issue of arsenic in rice -- is the difficulty of measuring an individual's exposure to a particular chemical over a lifetime, and the correlative nature of data on toxins' role in human disease. The rice foods industry balks at the prospect of regulations, and draws on the lack of absolute proof. On its website, the USA Rice Federation states: "We are unaware of any consumers being harmed by arsenic in rice ... Currently there is not sufficient data about arsenic levels in rice or potential risk to human health on which to base any recommendations to lower consumption."
"The Consumer Reports analysis ups the ante for regulatory agencies and industry to take measures to limit consumers' exposure to arsenic in rice," Nachman said.
Currently, the EPA limits arsenic in water to 10 parts per billion. There are no federal regulations or limits for arsenic in rice or most other foods. On September 20, the Consumers Union sent a letter to the FDA urging the agency to move forward on standards for arsenic levels in food products.
Deborah Blum, author of The Poisoner's Handbook, has pondered arsenic's toxic chemistry and myriad purposes. Years ago, arsenic was used in green dyes including food colorings for candies and cake decorations. In the Victorian period, women took Fowler's solution and other arsenic mixtures to achieve a pale complexion. In the 19th and early 20th centuries, arsenic was commonly available. "You could go down to any old pharmacy or grocery store and buy it as a rat or fly poison," she said. "It became an everyman's solution," she added. "Arsenic trioxide was super-easy and cheap to make."
Blum considers whether the arsenic findings have influenced her personal and family's food habits. "I'm just more aware now," she said. To minimize risk, she eats a variety of grains. "I believe in the principle of mixing it up," she says. "I look for geographical labeling of rice when I buy it, and I think about the portions."
The uncertainty about the source and clinical implications of arsenic in rice recalls concerns Carson raised years ago, when she exposed dangers of chemical toxins with likely but imperfectly-understood ill effects. Writing today in the New York Times Andrew Revkin cites a recent examination of Carson's original papers, which includes an excerpt from a draft of a chapter titled "Elixirs of Death":
... she tells us about the storage and accumulation of DDT in the human body, and how even small amounts have been shown to cause acute liver poisoning. She ends this section by telling us: "There has been no such parallel situation in medical history. We have some intimations as to what the ultimate consequences may be, but it is too early to know the full story."
"Rachel Carson's primary focus was on synthetic chemicals and man-made manipulation of the environment," Blum said. "The arsenic story reinforces her point of fifty years ago. We have to think about how we apply chemicals across a wide landscape and ourselves."
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