Friday, June 4, 2010

California May Approve Methyl Iodide for Strawberry Crops

It will hardly be a revelation to anyone who reads this blog to learn that I try to keep my produce organic whenever possible. I encourage others to do the same, for both health and environmental reasons. (Health claims can be split into nutritional claims and body-burden claims.) However, some people can't afford to buy organic produce, some don't have access to it, and some don't believe the health claims and don't care about the environmental costs. Pesticides aren't going away anytime soon.

Not all pesticides are created equal, however. California's Department of Pesticide Regulation is considering approving the use of methyl iodide for use on strawberry, tomato, and pepper crops. The notice of proposed decision and extended comment period is available here.

First, let's note that strawberries and peppers are both members of the Environmental Working Group's "Dirty Dozen." 90% of the strawberries tested by the EWG had pesticide residue left on the skin, even after washing, and 61% of the sweet bell peppers tested carried residues of 63 separate chemicals. In part because you can't really scrub a strawberry before you eat it, if you eat non-organic strawberries, you're significantly more likely than not to be eating some pesticide residue.

Now, let's talk about methyl iodide (MeI). MeI was approved for use as a pesticide by the EPA in 2007, over the concerns of research scientists. To quote from a 2007 letter from 50 scientists, including Nobel Laureates, to the EPA:

"[C]hemists who work with this material use the smallest amounts possible and take great precautions to avoid exposure. Because of methyl iodide’s high volatility and water solubility, broad use of this chemical in agriculture will guarantee substantial releases to air, surface waters and groundwater, and will result in exposures for many people. In addition to the potential for increased cancer incidence, U.S. EPA’s own evaluation of the chemical also indicates that methyl iodide causes thyroid toxicity, permanent neurological damage, and fetal losses in experimental animals. EPA’s exposure assessment suggests that the Agency is willing to accept exposures at levels that may cause these effects in humans up to five percent of the time near the application site."

Perhaps the CDPR thinks that there won't be a problem because "no dietary exposure is expected" (pg. 4). Risk evaluation was rather based on inhalation exposure, with dermal exposure being considered negligible (id.). Protection methods proposed include buffer zones (100 and 200 feet, depending on application methods) (pg. 5), tarps, maximum usage rates, and prevention of farm workers from re-entering the field for 14 days after application (pg. 7).

The atmospheric lifetime of MeI is 6.9 days in northern and mid-hemispheric latitudes. This means that, with no wind, proper tarping, and functional hazmat suits for farm workers, inhalation risks may be fairly minimal. This does not, however, mean that all the MeI disappears within 7 days, however: "Gan and Yates (1996) reported half-lives ranging from 13 to 43 days in unsterilized soil, and neutral hydrolysis half-lives in the range of 50 – 113 days have been reported (Mabey and Mill, 1978; Schwarzenbach et al. 1993, DPR, 2002b). Initial investigations into the environmental fate of iodomethane recommended a cautious approach due to the potential for ground water contamination (Gan and Yates, 1996; Gan and Yates, 1997). However, USEPA concluded that 'based on environmental fate data, the residual contents in soils (from field studies), and Tier I and II model estimated concentrations, the Agency does not expect iodomethane to adversely affect ground water.'" The risk characterization goes on to explain how other compounds in the soil will prevent transmission to groundwater (RCD pg. 7).

The risk characterization does not address any potential residue on the fruit itself.

An external Scientific Review Committee has expressed serious concerns about the public health impacts of approving MeI: "The Scientific Review Committee noted in their report: 'Based on the data available, we know that methyl iodide is a highly toxic chemical and we expect that any anticipated scenario for the agricultural or structural fumigation use of this agent would result in exposures to a large number of the public and thus would have a significant adverse impact on the public health. Due to the potent toxicity of methyl iodide, its transport in and ultimate fate in the environment, adequate control of human exposure would be difficult, if not impossible.'”

I'm not a scientist, and I'm not going to pretend to understand all of the degradation pathways which may make MeI less concerning than it's being treated in the blogosphere at the moment. With the concerns of the scientists quoted above, however, the possibility of serious carcinogenic tendencies documented (MeI is listed as a carcinogen under Prop. 65), and poisoning consequences as described here, I'd rather it stay far away from my food supply.

2 comments:

  1. Curious: Do you know if California is the first state to approve this pesticide?

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  2. Mmmmmm, pesticide-free strawberries

    ReplyDelete