Photo by Roberto DazaAt Gavilan View Middle School in Salinas, children play near strawberry fields
California pesticide regulators plan to approve a new agricultural chemical to sterilize the soil of strawberry fields, but state records and interviews with scientists raise questions about whether workers and nearby communities can be adequately protected from the highly toxic chemical.
Currently, strawberry growers use a fumigant called methyl bromide, which is being phased out around the world because it damages the ozone layer. But the alternative, methyl iodide, a carcinogen and neurotoxin that can cause miscarriages and other medical problems, is considered far more toxic than methyl bromide.
In interviews with KQED's "Quest," members of a scientific review panel that examined the potential use of methyl iodide said it was clear to them that exposure levels would far exceed what they, along with staff scientists, had deemed safe.
"I understood those levels were unattainable," said panel member Edward L. Loechler, a professor of biology at Boston University. "It was blatantly obvious that those levels were unattainable."
The panel's chair, John Froines, a professor in the Department of Environmental Health Sciences at UCLA, said, "I honestly think this chemical will cause disease and illness. And so does everyone else on the committee."
Lea Brooks, a spokeswoman for the California Department of Pesticide Regulation, which has approved the use of methyl iodide, said in an email that risk managers at the agency have concluded that the chemical can be used safely "with the strict safeguards proposed."
"No pesticide," she said, "has been evaluated more than methyl iodide in the history of the Department of Pesticide Regulation."
Brooks said methyl iodide's approval comes with a list of required safeguards – tools like buffer zones and respirators – intended to keep workers and bystanders safe from inhaling dangerous levels of the chemical.
Farmers who use methyl iodide would be required to create buffer zones of 200 feet or more, depending on the number of acres being fumigated. The buffer zone would be extended to a half-mile for schools, hospitals and daycare centers.
At Gavilan View Middle School in Salinas, where little league teams practice just yards away from commercial strawberry fields, fumigation companies would have to ensure that the school remained vacant for 48 hours.
The buffer zones proposed for methyl iodide are similar, though more stringent, than what's required for methyl bromide.
In interviews, strawberry pickers said that buffer zones are generally enforced when fumigators are working in nearby fields. They said that they sometimes smell fumes, which drift across the fields.
"Sometimes you feel nauseous, or your head aches," said Alejandra Nolasco Campos, a mother of two who works in the Salinas-area strawberry fields. "But if you feel bad and you sit down for a while, then once you’ve recuperated, you head back."
Photo by Roberto DazaAccording to UC Davis research, fumigated strawberry beds are twice as productive as their nonfumigated counterparts.
Campos says that, like many women in the fields, she worked through the first five months of her pregnancy. Since methyl iodide is a neurotoxin that can cause miscarriage, scientists on the panel were particularly concerned that it could harm the brains of developing fetuses.
"The endpoint you're basing this on is death," said Loechler. "Even if the fetuses aren't dying, they may be experiencing other impacts that are subtler than death, but still serious."
Episodes of pesticide "drift," such as those described by Campos and other farm workers, are hard to count, because they're only recorded when workers end up in the hospital as a result of their exposure. According to the Department of Pesticide Regulation, there were an average of 37 such incidents each year between 2000 and 2007.
Because of the concerns around methyl iodide, the Department of Pesticide Regulation asked Froines to convene the scientific review panel to help assess the chemical's toxicity, and to recommend exposure levels at which it might be considered safe.
Members of the panel, along with staff scientists within the DPR, arrived at two numbers: 0.3 parts per billion for bystanders and 0.8 parts per billion for workers. Exposure above that amount, they said, would be unsafe. Field studies conducted by the DPR suggest that with the best available protective measures, including respirators and "virtually impermeable" tarps, a worker's exposure could reach 68 parts per billion.
The methyl iodide approval would set stringent rules for people who handle the chemical directly. Typically, these are employees of fumigation companies, which growers hire to treat their fields. Fumigation companies are responsible for enforcing buffer zones and other rules.
For these workers, there is no tool more important than a respirator, which filters air through two cannisters attached at the sides. In its approval of methyl iodide, DPR risk managers calculate that a respirator will filter out 90 percent of the methyl iodide exposure that a worker would otherwise inhale.
These calculations are spelled out in a document obtained by KQED's "Quest" through a public records request. Workers applying methyl iodide to a field – some of whom not wearing respirators – wore air-sampling devices that monitored exposure levels. The tests showed that without a respirator, a worker could be exposed to as much as 1,135 parts per billion of methyl iodide over an eight-hour workday. A respirator, they calculated, would bring that number down to 135 parts per billion.
Scientists on the panel believe that 90 percent reduction is unrealistic.
"The 90 percent number comes from laboratory studies," said panel member S. Katharine Hammond, an expert on chemicals and worker safety at UC Berkeley.
Hammond said that in order for a respirator to be effective, the filtering cannisters must be changed daily. A worker cannot have facial hair or sweat, lest small gaps between his face and mask suck in unfiltered air, she said.
Hammond notes that respirators are uncomfortable and prevent workers from communicating with each other: "It's not infrequent for those of us who [study this] to see people simply wearing their respirators around their necks."
Hammond and other members of the panel advised the DPR to use a 50 percent calculation for respirator effectiveness, rather than 90 percent. In her e-mail, Brooks said the DPR stands by its 90 percent number.
"The respirators provide a minimum of 90 percent protection if used according to our regulations. If the regulations are not being followed, there is an enforcement problem. Violations should be reported to the county agricultural commissioner."
In Monterey, one of the state's two largest strawberry-growing regions, Chief Deputy Agriculture Commissioner Karen Stahlman said her office oversaw 120,000 pesticide applications in 2009. Due to a limited staff, she said, inspectors conducted site visits on fewer than one percent of those applications.
In 2007, one of the state's largest fumigation companies, TriCal Inc. was fined $2,500 for fumigating while a home within the buffer zone was still occupied.
State records show that TriCal and another of the state's largest fumigation companies, Crop Production Services, have each been fined nine times in the last two years for various violations, including failing to have proper protective gear at hand and mishandling chemicals.
Given methyl iodide's toxicity, members of the scientific review panel say it's unwise to take chances with precautions that don’t always work.
"If you’re dealing with a chemical where the outcome is that your eyes burn or you have a scratchy throat, then the risks of maybe one-in-a-thousand-times having a problem, then, you know, maybe that’s an acceptable risk," said Katherine Hammond. "But if several things go wrong, and the consequences are serious adverse health effects, like cancer, like a child who has serious intellectual impairments, then that's a tragedy to the individual families involved and a public health problem."
Public comment on the DPR's methyl iodide decision runs through June 29. State Sen. Dean Florez, D-Fresno, is holding a hearing on the issue June 17 in Sacramento.
California Watch contributor Amy Standen is a radio reporter for KQED's QUEST, where she covers science and environmental issues facing Northern California. Listen to her KQED QUEST program about strawberries and worker safety here.