The fight over a much-needed pesticide: methyl iodide

  • Farmworkers weed strawberries in a field near California's Central Coast. While methyl iodide dissipates before fruit is harvested for consumption, scientists worry exposure to the fumigant could harm the health of workers and residents nearby.

    Gosia Wozniacka, Associated Press
  • Workers wearing masks and hazmat suits inject methyl iodide into a field in Fresno County, then cover the field with tarps, in the state's first application of the controversial chemical.

    Fresno County Department of Agriculture

In May, on a farm outside of Sanger, Calif., a man in a white hazmat suit and a gas mask drove a hulking tractor over bare ground, injecting toxic gas 12 inches deep in the soil. Behind the machine, plastic tarps unrolled like Saran Wrap over the land to contain the chemical. In the next two weeks, the fumigant would spread through the soil, killing everything from worms to weeds before peppers would be planted.

On that sunny day in the San Joaquin Valley, California received its first commercial dose of methyl iodide. The controversial chemical was approved by the state late last year as an all-purpose pesticide to replace methyl bromide, a similar fumigant being phased out for depleting the ozone layer.

But while it's gentler on the sky, methyl iodide brings problems of its own. Critics warn of possible health impacts to farmworkers and nearby residents, citing laboratory studies linking it to thyroid cancer, neurological problems and late-term miscarriages. On June 2, around the time the tarps were removed from the pepper field, protesters showed up at the Fresno County agricultural commissioner's office, holding signs saying "We will not be poisoned" and demanding that the chemical be banned.

That was just the latest salvo in a two-year fight by labor and environmental groups now aimed at revoking what they see as the state's illegal approval of a dangerous fumigant. Farmers, on the other hand, say methyl iodide is essential for growing delicate, high-value crops, including $2.3 billion worth of California strawberries. The conflict has moved to the national stage, as environmental and health groups petition the Environmental Protection Agency to reconsider its initial permitting of the pest- and weed-killer. Meanwhile, the ongoing controversy has raised broader questions about how regulators can protect public health when big business depends on toxic chemicals.

Before methyl iodide ever got to California, it had to pass muster with the EPA. Agency scientists assessed its health and environmental risks; regulators then looked for ways to mitigate those risks without overly burdening farmers financially. In what it calls "one of the most thorough risk assessment processes ever completed by the agency," the Bush-era EPA signed off on methyl iodide in 2007 despite protest from the scientific community, including a letter from 54 scientists decrying its toxicity.

Even after EPA's go-ahead for nationwide use, some states sought extra protections. California, whose strawberry industry was poised to be the country's largest user, gave methyl iodide a three-year review. Scientists at the state's Department of Pesticide Regulation analyzed its potential health impacts, and the agency commissioned a special scientific review committee. Last February, the committee reported back, recommending exposure rates that were so low they would essentially prohibit its use. The report cited major gaps in the health data and warned that "due to the potent toxicity of methyl iodide ... adequate control of human exposure would be difficult, if not impossible."

Meanwhile, conventional farmers needed something to take the place of methyl bromide. Other fumigants exist, but methyl iodide is the most efficient at killing the disease-causing pests that can decimate fragile crops like strawberries. Without an effective replacement, growers could face lower yields, costing an estimated $100 million yearly, according to the Giannini Foundation, an agricultural economics institute at the University of California. 

In late December, despite warnings from scientists both inside and outside of the state pesticide agency, then-DPR head Mary-Ann Warmerdam, who was appointed by then-Gov. Arnold Schwarzenegger, signed off on methyl iodide, approving exposure levels over 100 times higher than committee scientists recommended. These are, however, the strictest methyl iodide regulations in the country: Exposure limits remain well below those of the EPA, and no fumigation is allowed within a half-mile of schools and hospitals, with smaller buffers around neighborhoods.

Even so, John Froines, the toxicology professor at the University of California-Los Angeles who headed the scientific review committee, was dismayed. "You got the best science you could get," he says. "And then there was the disappointment that the scientific findings weren't followed."

Now, opposition to methyl iodide has become a rallying cry for groups like Pesticide Action Network and Earthjustice. On Dec. 30, Earthjustice, representing environmentalists and farmworker advocates, sued to revoke the state's approval of the chemical. In addition to ignoring scientists' recommendations, the group contends the agency's timing was suspect, saying it rushed the pesticide's final approval to get it done by Dec. 20, sending methyl iodide to market just before Gov. Jerry Brown -- a potential ally of the critics -- took office in January.

The agency's approval of methyl iodide ignores real-world farming conditions, critics say. For example, DPR assumes that approved respirators will be available and used by farm workers. Opponents counter that this assumption is unrealistic in the heat and rush of harvest season. The agency says tarps over fumigated fields will keep the chemical from drifting into neighborhoods; opponents point to incidents when such tarps have blown off in high winds, releasing dangerous chemicals. As strict as the state's standards are, enforcement falls on the shoulders of already-strapped county agricultural agencies. "It's like having a speed limit without any cops to enforce it," says Susan Kegley, a chemist for the Pesticide Research Institute, a consulting firm that works with environmental groups.

California regulators stand by their decision. Only trained workers will be allowed to apply the chemical, they say, and county enforcement will keep workers and communities safe.

But a lack of understanding about exactly how DPR arrived at its final exposure standards has helped spark rampant speculation about political influence and corporate pressure. The agency is reluctant to talk about its process, citing the pending lawsuit. Two lead DPR scientists who warned of methyl iodide's risks have since left; both declined to comment. Director Warmerdam resigned from the agency and took a job at the Clorox Company.

Last March, the fight went federal when environmentalists and farmworker advocates petitioned the EPA to revoke its 2007 decision. In response, EPA opened public comment on the petition. Pesticide watchdog groups submitted over 200,000 signatures asking EPA to reconsider, and on May 7, a group of 39 scientists sent another letter warning of methyl iodide's dangers. California Gov. Brown has promised to "take a fresh look" at the issue.

Whether EPA will actually rethink its methyl iodide approval remains to be seen, but the agency must still consider potential losses to farmers. When those are high, as in the case of a toxic fumigant without a comparable alternative, the decision almost always goes in favor of the fumigant, Kegley says.

With fall planting season fast approaching, California strawberry fields could soon see methyl iodide for the first time. But ongoing protests and bad press keep farmers uneasy about the public response. "We do have to be careful as an industry," says Mark Bolda, farm advisor for the University of California agricultural extension in Santa Cruz County. "You will be in the newspaper if you use (methyl iodide) and the public perception of you as a grower will not be good."

In the heart of strawberry country, farmers -- and municipalities -- are taking heed. Last November, the Central Coast city of Watsonville passed a resolution against the chemical. The action was symbolic, since the town can't stop applications, but so far no local farmers have applied for a permit, according to Mary Lou Nicoletti, agricultural commissioner for Santa Cruz County. "Nobody wants to be first," she said.

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