On rice and arsenic

Source: Wikimedia Commons

Last week, a team of researchers from Dartmouth University released a widely publicized study with the somewhat provocative title  “Arsenic, Organic Foods and Brown Rice Syrup.”

The study was yet another general reminder that words like “organic” or “natural” are not synonymous with the word “safe.”  But more specifically it detailed unexpected amounts of poisonous arsenic compounds in everything from infant formula to snack bars, especially compounds containing rice or sweetened with brown organic rice syrup as a healthier alternative to high fructose corn syrup.

I’ll return to the question of exact amounts later; let us just note for now that all findings were in part per billions,  numbers that may raise concerns about long-term exposure but do not suggest that anyone will be dropping dead after snacking on a cereal bar.

The more interesting immediate question anyway, at least to me, was:  why were Dartmouth chemist Brian Jackson and his colleagues looking for arsenic in these supposedly healthy products at all?  I rapidly discovered though that I just hadn’t been paying attention. They were simply following up on an issue well known in health science, a body of work establishing a troubling connection between rice and arsenic in the food supply.

In fact, my use of the word “unexpected” probably is more accurate in describing dismayed public reaction to the results.  The authors of the new study emphasized that their working hypothesis, from the start, was that  brown rice syrup would introduce arsenic into these foods.

So why rice in particular?

Rice Field: Wikimedia Commons

As it turns out, the rice plant is uniquely engineered to pick up arsenic from the environment. This begins with the fact that the plant is designed to easily absorb the mineral silicon which helps give  rice grains their elegantly smooth structure. The crystalline structure of arsenic is just close enough that rice plants readily uptake arsenic as well. In fact, a toxic metal study, also from Dartmouth, described rice as “a natural arsenic accumulator.”

The efficiency of this system also means that the arsenic tends to be absorbed directly in its more toxic inorganic from rather than being converted to an organic form of arsenic. Here I mean organic not in the USDA-approved farming sense but in the chemistry sense in which organic refers to carbon-based compounds. And this is important because we metabolize organic arsenic compounds pretty neatly, reducing their toxic potential. It’s inorganic arsenic that’s most dangerous  – it tends to bond tightly into living cells where it destroys them by disrupting their metabolism. And rice, experts say, may be the largest source of inorganic arsenic in our diets.

How does rice find the arsenic? Well, as I said, arsenic is a naturally occurring

Arsenic Map of the World/Source: Harvard University

element, sprinkled through soil and rock across the planet.  I’ve put a basic arsenic map of the world here to the left to show you the general distribution and hotspots. This is geologic map, of course, and there can also be human introduction of arsenic into a region. A 2007 report, titled “U.S. Rice Serves Up Arsenic” noted that rice-growing regions in the Southeast appeared also show signs of contamination from early 20th century use of arsenic-based insecticides to control for pests like the cotton boll weevil. That study found higher levels of inorganic arsenic in Louisiana rice, for instance, than that from California’s Central Valley, which has a far greater natural distribution of arsenic.

But that map should also remind us that although rice seems to have an affinity for arsenic, we’re surrounded by and exposed to that poison on a daily basis in many different ways.  A very thorough Consumer Reports write up of this latest research points out that last fall similar concerns were raised about arsenic contamination of fruit juices.

The Dartmouth study, in fact, did not turn up an arsenic free food product. The researchers looked at 29 brands of cereal bars, 22 contained a rice product and seven did not. All the cereal bars contained some trace of arsenic. Those without rice ranged from 7 to 28 parts per billion. As you might now expect, the readings from the rice products were higher, ranging from 23 ppb to a high reading of 128 ppb. Infant formula sweetened with rice syrup hovered close to 60 ppb.

And what does all that really mean? As the authors note,  the U.S. Food and Drug Administration (FDA) does not set a safe arsenic standard for food.  (And we’re not along in that. A Canadian Broadcasting Corporation story on the Dartmouth findings also noted a lack of public health standards for arsenic food exposure in that country.) But the U.S. Environmental Protection Agency (EPA) has established a 10 part-per-billion level for drinking water.

In an interview with NPR, Jackson said the EPA standard should probably be considered in assessing risk for something like infant formula – also a liquid consumed on a daily basis. It works less well for cereal bars and occasional consumption only and by a generally much larger, less vulnerable human being. And it’s almost important to note than the  10 ppb standard signifies EPA’s effort to set standards far, far below an actual toxic effect.

In other words, these are pay attention numbers rather than immediate alarm numbers.  They should remind us that, as always, a varied diet is healthier than relying too much on any single source of food. But as Jackson also pointed out the growing body of work on arsenic contamination of food in general, should also serve as prompt to our government agencies to take some of these unexpected hazard issues out of our food supply, start working out those much needed official safety standards for arsenic in our diet, and provide us with some kind of realistic assessment that will allows to make our own decisions about such risks.

I couldn’t agree more.

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19 Responses to On rice and arsenic

  1. Pingback: Study: Organic Rice Syrup Linked to High-Arsenic Baby Formula – Environmental Leader | Health Corner

  2. Gaythia Weis says:

    Arsenic is also common in significant concentrations in well waters in the US: http://water.usgs.gov/nawqa/trace/arsenic/
    Fallon, Nevada is one community with As so high that expensive remediation methods have been put into place:http://www.epa.gov/ogwdw/arsenic/casestudies/pdfs/casestudy_fallon.pdf

    These methods would be out of reach by communities elsewhere, such as in Bangladesh. The original switch to well water there was supposed to improve the quality of drinking water, but then tragically, As poisoning resulted. I believe that strategies for minimizing As uptake into rice are being investigated. In Bangladesh, obviously just telling people to vary their diet will not be an effective strategy.

    In my opinion, humans probably have always coexisted with As, and the key will be not in eliminating As from food and water supplies but in finding hot spots and concentrating mechanisms that can be reduced. Food examples would include soil testing for native As and residual As pesticides; varying irrigation water, and addressing concerns about the concentrating effect of some food processing such as the rice syrup as described in the article above.

  3. Mary says:

    Huh–I wonder if NH has the same problem as Maine. When we lived in Maine we used to joke about going to people’s houses for parties, because the arsenic levels were so high in the water. We used to first ask, “So, how are your pets lately?” and look around for them before we’d take a glass of water….

    But some of that organic baby formula and that water–wow. That could be somethin’.

  4. Deborah Blum says:

    Wow, that’s a great story. But underneath it smart – my take is that it makes sense to be aware of things that might add significant extra arsenic to your diet. Groundwater is a big one. Here’s a link to a USGS map of arsenic contamination of groundwater in the US which might help some with your questions: http://water.usgs.gov/nawqa/trace/arsenic/

  5. Deborah Blum says:

    Yes, I wrote a post about the arsenic poisoning of well water in Bangladesh a while back, called “How to Poison a Small Country”: http://blogs.plos.org/speakeasyscience/2010/10/13/how-to-poison-a-small-country/

    And I agree with you on living with arsenic that the focus should be on awareness and, when needed, remediation. The value of government safety standards is that they encourage both. Or so we hope.

  6. Gaythia Weis says:

    I am interested in how this information is spreading rapidly through the media, (yea bloggers!) and how quickly some US rice growers have prepared an online response, and have started on plans to address this issue:
    http://www.lundberg.com/Info/Arsenic.aspx

  7. Judy Langston says:

    Regarding your paragraph about rice being “uniquely engineered to pick up arsenic from the environment”, and the Dartmouth comment that rice is “a natural arsenic accumulator,” you might find of interest the article “A Guide to Poultry Litter Use in Louisiana Rice Production” published by Louisiana State University Ag. Center in January of 2010 (www.lsuagcenter.com), The article says that poultry litter has increased rice productivity levels and its usage is increasing in Louisiana rice fields. From other articles I have encountered, Louisiana is far from being the only place poultry litter is being used on rice crops. It is interesting to note that none of these articles recommending chicken litter as a nutrient rich plant food mention that it also contains lots of arsenic.
    In your own Nov. 2010 article for the L.A. Times “Arsenic and Tom Turkey” you talk about an arsenic compound fed to poultry resulting in arsenic being found in relatively high levels in both the meat and in the waste products of the chicken. So when poultry manure is used to fertilize rice, there will likely be a great deal more arsenic for the rice to pick up. Even when it is not used on the rice crops specifically, its use for fertilizer on other crops or livestock pastures could contaminate the soil and the water in proximity to the rice fields. And rice is probably not the only crop vulnerable to arsenic contamination from poultry fertilizer.
    Another article of interest might be “It’s not just chicken feed,” published in the Bay Weekly (http://bayweekly.com) in December 2011. The Maryland General Assembly was sufficiently concerned about arsenic in the chicken litter being spread on Maryland soil and getting into Maryland waters that they commissioned a study by the University of Maryland’s Hughes Center. Their conclusion was that “the use of arsenic as a feed additive is not a sustainable practice.” and could potentially lead to cancer and other serious health issues.

  8. Deborah Blum says:

    Thanks for sharing this, Gaythia. You are so right – really interesting to see such a strong response from rice producers and really encouraging. I put it on Twitter as well, just to underline the point.

  9. Deborah Blum says:

    Thanks for writing about this, Judy, and in such a thorough and thoughtful way. I used the example of early 20th century use of arsenic-based fertilizers in my piece but you are absolutely right that this practice might also be having an effect. It would be very helpful to see some coordination between the FDA (which helped engineer at least a temporary suspension of the arsenic-infused poultry food, Roxarsone) and the EPA on this one. Worth keeping the pressure on, I think.

  10. Scott says:

    Government regulatory bodies and NGOs like Codex Alimentarius are defining maximum “acceptable” levels of toxins in food. Mind you, we’re talking about 1 Part per million or billion difference separating “acceptable” from “unacceptable.” To me, it’s all just a guess. There are no long term toxicology tests for human health safety, I’m sure, for many of these industrial byproducts. All the regulators have done is set forth a standard to allay consumer fears while allowing the unfettered ruination of our air, water and soil from these crazy manufacturing processes. In the name of sustainable unstinted growth, we’re expected to make sacrifices. It’s just that most people didn’t sign on that being slowly poisoned.

  11. Thanks for writing such a through article about arsenic. Most articles out there only talk about the issue, not the body of studies that have shown this link for many years. When I heard about the issue, I knew something wasn’t right and dug as well to find the 2007 study by Professor Meharg that you referenced. After reading his study and talking with him, I was outraged that the FDA and the EU hadn’t set arsenic levels.

    Consequently, I wrote two different articles on my site about the the Dartmouth study and how to eat rice safely. In addition, I started a campaign over on Change.org to ask the FDA and the EU to address the arsenic. http://chn.ge/zyKERf (Both articles are listed in the Change.org petition.)

    Thanks again for such a through article making sense of the situation.

  12. Pingback: Your Questions About Chemistry | Signs You Met the Right One

  13. Bipin Prasad says:

    I have a Solution of arsenic in Food chain. we have devlop a Nutrient solution which will decrease the arsenic accumulation to the rice….for more details can contact at infoepwo@gmail.com

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