Two Sticky Points with Rice: Arsenic and Climate Change

The world’s No. 2 staple food takes a couple hits from scientists.

Rice 101

Okay, if you know your rice basics, you probably know that it comes in three basic types: long-, medium- and short-grain. But did you know there are more than 40,000 varieties from four major categories: Indica, japonica, aromatic and glutinous?

The varieties include wild rices (which are actually aquatic grasses*), aromatic rices such as basmati and jasmine, Arborio rice (the stuff used for risotto), and good old American long-grain rice.

And rice is not just multifarious; it’s downright popular, right behind corn as the world’s most popular foodstuff. And it’s a staple food for more than half the world’s population.

Last year some 700 million metric tons of paddy rice were grown, which translates into about 450 million tons [pdf] of milled rice.

Asia grows and eats 90 percent of the world’s rice, but the United States is no slouch, producing about 8.4 million tons of paddy rice (about 5.9 million metric tons of milled rice) or 1.3 percent of world production, mostly long-grain varieties. According to the lobby group U.S.A. Rice Federation, rice, which has been cultivated in North America since the 17th century, is currently grown in primarily seven states: Arkansas, California, Texas, Louisiana, Mississippi, Missouri, and Florida.

While we grow a lot of rice today, it’s not nearly enough to meet demands in the more populous world envisioned in the coming decades. It’s projected that production would have to increase to about 650 million tons of milled rice by 2050 — an increase of 45 percent [pdf].

What’s in that rice you’re eating

Turns out that while humanity has been scarfing down those many grains of rice, we’ve been ingesting a bit of arsenic in the process. That’s right — arsenic.

Maybe you’re familiar with this startling finding from the big news item in September: a study by Consumer Reports on the topic called the levels of arsenic in rice “worrisome” and recommended that people eat less of it, a recommendation not found in a government study on the same topic that was publicized around the same time.

So where is the arsenic coming from? From man-made pollution? Or is it naturally occurring? Here’s what the FDA says:

“Arsenic is a chemical element distributed in the Earth’s crust. It is released from volcanoes and from the erosion of mineral deposits. It is found throughout the environment—in water, air and soil. For that reason, it is inevitably found in some foods and beverages.
Human activities also add arsenic to the environment. They include burning coal, oil, gasoline and wood, mining, and the use of arsenic compounds as pesticides, herbicides and wood preservatives.
FDA has been monitoring arsenic levels in rice for more than 20 years. Its analysis thus far does not show any evidence of a change in total arsenic levels. The change is that researchers are better able to measure whether those levels represent more or less toxic forms of arsenic.”

In other words, we don’t know.

So what, if anything, should we rice eaters do about it? For the time being, the FDA recommends no dietary changes except to make sure, in the words of FDA Commissioner Margaret A. Hamburg, M.D., you “eat a balanced diet that includes a wide variety of grains — not only for only for good nutrition but also to minimize any potential consequences from consuming any one particular food.”

As ABCNEWS reports, Consumer Reports recommends that “rice eaters limit themselves to one serving a day, especially for babies. Rinsing and then boiling rice in a 6 to 1 water ratio removes about 30 percent of its arsenic. They also caution that children under the age of 5 should not be given rice drinks as part of their daily diet” while the FDA completes its analysis.

In other words, another caveat emptor from TheGreenGrok.

The climate conundrum

On another front, growing rice has serious implications for the globe. Rice cultivation uses about 10 percent of arable land and is a major source of greenhouse gas emissions, primarily methane. Currently, rice accounts for about “10% of human-induced [methane] CH4 emissions, or 20% of total agricultural CH4 emissions,” and its global warming potential is about four times higher than either corn or wheat.

That’s today, but what about the future? The climate is changing. How will those changes affect the climatic impact of rice cultivation? Will it make it worse or better?

Writing in the journal Nature Climate Change last week, Kees Jan van Groenigen of Trinity College Dublin and colleagues attempted to address those questions. They start from the premise that climate change will impact rice (and other crops’) yields in two opposite ways:

1) increasing concentrations of carbon dioxide (CO2) are expected to increase yields (the fertilizing effect) while

2) warming temperatures are expected to decrease yields.

Rising CO2 and temperature will also impact methane emissions from rice. To figure out what the net effects of all these impacts will be, the authors performed a meta-analysis of 63 studies of rice yields and emissions. Their findings? In Jan van Groenigen’s words, “Our results show that rice agriculture becomes less climate-friendly as our atmosphere continues to change.”

Specifically, the authors found that both rising CO2 concentrations and warming temperatures caused the greenhouse gas intensity of rice cultivation (on a yield basis) to increase — possibly almost doubling it by 2100.

This suggests a double climate whammy from rice is in store for the world: more rice cultivation, by as much as 50 percent near the mid-century mark, and more emissions per ton of rice produced, by as much as a factor of two.

Add the whole arsenic-in-rice thing to this bad news about rice and climate change and to the falling out of PC-grace for rice at weddings, and one could easily envision rice lovers everywhere Crying Out to Heaven.

____________

End note

* According to the U.S.A. Rice Federation, wild rice is “not true rice at all but an aquatic grass, which grows wild but is also cultivated. The grains are long and slim and range in colour from dark brown to black.”

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