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The Federal Drug Administration is investigating research that has found some rice contains inorganic arsenic levels being characterized as "worrisome." Their review of the research may result in their finally setting a maximum limit of inorganic arsenic in our foods.
While this should be good news to consumers, the media's coverage seems to be missing some crucial information. Like where the arsenic comes from and how we can avoid it.
The FDA's data found inorganic arsenic levels between 3.5 and 6.7 micrograms per serving in their sampling. And a recent Consumer Reports study found similar levels. But this really is not news.
Numerous studies have been published over the past decade documenting arsenic content in rice grown from around the world. Dr. Andrew Meharg, a professor of biogeochemistry at the University of Aberdeen, has led or been part of the research teams in many of these studies.
In 2007, Dr. Meharg led a study that measured arsenic levels among rice grown throughout the U.S. He and his team analyzed 107 samples of rice grown in Louisiana, Mississippi, Texas, Missouri, and Florida, and 27 samples of rice grown in California.
Meharg and his team found that the 107 southern US and central US rice samples averaged .30 micrograms per gram of arsenic (equivalent to 4.4 micrograms per serving), and the California rice samples averaged 0.17 micrograms/gram (ppm) (about 2.5 mcg per serving).
However, <em>Organic brown rice grown in California had the lowest levels of all 134 samples, with 0.10 micrograms/gram.</em> This is equivalent to about 1.5 micrograms per serving - far less than the "worrisome" levels found in the FDA and Consumer Reports data. This indicates that organic rice will most likely be significantly lower in arsenic.
It should also be noted that these findings were on total arsenic content. Organic arsenic is a natural component of soils and is considered a trace mineral necessary for health. Inorganic arsenic is another creature altogether.
Inorganic arsenic has been found to be carcinogenic.
Dr. John Duxbury of Cornell University studied U.S. rice samples from different regions and found the total arsenic content averaged only 22% inorganic, while Dr. Meharg's findings showed that the percentage of inorganic arsenic to total arsenic content averaged 42%. This is explained by the fact that different soils have different levels of chemical contamination.
Organic arsenic in its unoxidized form is not necessarily harmful to the body in trace amounts. The body utilizes and metabolizes this form. The inorganic forms – oxidized versions such as arsenic oxides or arsenic trioxide, are produced with synthetic chemicals. These are the forms that have been found to be the most carcinogenic, although large amounts of organic arsenic are considered harmful and possibly even carcinogenic.
In other words, organic arsenic is readily present in natural soils, while inorganic arsenic is found in soils that have been sprayed with arsenic-based chemical pesticides, or watered with water containing chemicals high in arsenic. And since the plants will readily retain and store both forms, foods grown in soils that undergo chemical spraying - or have in the past - will contain higher levels of inorganic arsenic.
For example, cotton has been known to contain some of the highest levels of arsenic among U.S. crops. This is because cotton crops have historically been sprayed heavily with arsenic-based pesticides to control boll weevils.
Accordingly, Louisiana rice – where a fair amount of rice is grown in soils previously farmed in cotton – had the highest levels of arsenic in Dr. Meharg's research. Louisiana rice had 0.66 micrograms/gram of arsenic. This means that the arsenic levels of the organic rice were 15% of the arsenic levels of the Louisiana conventional (non-organic) rice.
In addition to cotton, fruit trees were sprayed with lead hydrogen arsenate for many decades. Now, conventional fruit trees are often sprayed with disodium methyl arsenate (DSMA) or monosodium methyl arsenates. These yield oxidized arsenic, but without the lead. Oxidized arsenic is also used in wood preservatives, antifungals and many other chemicals.
While there is no arsenic standard in food, there is an arsenic standard for drinking water, set by the U.S. Environmental Protection Agency. Using the average arsenic levels found in Dr. Meharg's research, one would have to consume over 115 grams of rice to exceed the EPA's standard of 10 micrograms/liter, equivalent to 10 parts per billion (ppb). The average American consumes only about 12 grams of rice per day. Asian Americans, however, average more than 115 grams of rice in a day.
A more recent Meharg study from Spain showed that most rice-based infant formulas - which used conventionally grown rice from around the world - also contained high arsenic content.
Other studies by Dr. Meharg found that arsenic levels in rice milk often exceed the U.S. as well as E.U. arsenic drinking water limits. Dr. Meharg and his team found that 80% of rice milk samples tested from supermarkets in 2008 exceeded the 10 microgram/liter limit. Rice cakes and crackers also contained higher levels of arsenic according to another study.