EPA Orders More Studies of Malathion

Citing “questionable” findings in previous studies, the U.S. Environmental Protection Agency has ordered more long-term investigations on the potential hazards of malathion, the pesticide currently being applied in the Los Angeles Basin to combat Mediterranean fruit flies.

Joanne Edwards, an EPA entomologist based in Virginia, said the agency ordered additional studies last February because some previous reviews were flawed and one pointed to the possibility of increased liver cancer in a strain of male mice fed high doses of the chemical. The agency also ordered the manufacturers to further study the pesticide’s potential association with birth defects.

The EPA, which polices chemicals released into the environment, has found no cause to suspend malathion usage and the state insists it is safe. Edwards described the request for new studies as “routine” in cases involving pesticides that have been on the market for many years and were registered when guidelines were less strict.

“We don’t have enough information to make a determination one way or another” on possible hazards, she said.

“We are being cautious,” Edwards said. “You probably have a lot of EPA scientists who believe it is not a carcinogen. We are just ensuring that (health and safety) guidelines are met.”

State and county officials began applying malathion over the Los Angeles Basin last August in the early stages of what has evolved into the worst outbreak of Medflies in county history. On Thursday night and again on Nov. 29, the state will spray a 22-square-mile section of East Los Angeles and the San Gabriel Valley. The pesticide also was applied heavily over residential neighborhoods during a statewide infestation that began in 1981.

No Delay in Spraying

The Los Angeles County Board of Supervisors on Tuesday called for a re-evaluation of the methods used for fighting the Medfly, but refused to delay further spraying. Dr. Paul Papanek, chief of the county health department’s toxics epidemiology program, told the supervisors that “we have yet to have a single call from a physician or other health care provider that there is even a suspected case of illness related to spraying.”

The state Department of Food and Agriculture, which has final authority in the Medfly battle, has determined in its own reviews that malathion--a common backyard pesticide--is not a carcinogen. Studies done after widespread spraying in 1981 and 1982 revealed no adverse health effects in humans, but linked deaths of thousands of fish and the loss of many beneficial insects, like honey bees and ladybugs, to the chemical.

Dr. Raymond Neutra, chief of epidemiological studies for the state Department of Health Services, said the earlier studies demonstrated that the chemical did not cause miscarriages or low birth weights in children born to mothers who lived in neighborhoods that were sprayed. However, he said, unpublished studies showed that residents experienced a variety of anxiety-induced symptoms, including headaches and nausea, prior to the sprayings. The symptoms ended during the application.

To battle Medflies, malathion is being dropped in a sticky bait that attracts the pest. As a result, the chemical cannot be inhaled by humans. Moreover, it “tends to be held in the bait rather than absorbed through the skin,” said Jay Schreider, a staff toxicologist with the state Department of Food and Agriculture. This reduces the likelihood the pesticide can harm people in the spray zones, officials said.

Schreider said the state looked at the studies that the EPA had found inadequate and “filled in the data gaps.” The long-term studies ordered by the EPA will not be completed for nearly four years. “Our conclusion was based on the weight of the evidence for all of the studies,” Schreider said.

Dr. Duncan Thomas, a USC medical professor who conducted the larger of two studies done on the effects of the spraying on pregnant women in 1981 and 1982, said his study showed “possible associations” with malathion and certain rare birth defects. Thomas, however, attributed the few instances of such abnormalities as cleft palate, club foot and gastrointestinal defects to “statistical flukes.”

“The study was not designed to look at those (incidents) with any real rigor and, by and large, they are not associations that seem biologically plausible,” Thomas said.

Janet Hathaway, an attorney who specializes in pesticides for the Natural Resources Defense Council, said malathion was the third most common cause of pesticide illness in California farm workers from 1981 to 1985. The pesticide is widely used on home gardens and a variety of fruit and vegetables.

Although the EPA has found no clear association between the chemical and cancer, Hathaway said she believes aerial sprayings should not be conducted until all the studies are complete. “Using chemicals that haven’t been adequately tested in animals is extremely problematic,” she said. “I find it terribly distressing that humans are the guinea pigs.”

A spokeswoman for the state Department of Food and Agriculture said a ranking of pesticides that caused farm workers to be hospitalized between 1980 and 1986 shows malathion was not at the top. There were 15 chemicals that caused more hospitalizations and 32 that resulted in fewer, she said.

“You’re talking about very small doses” that are being dropped aerially, she said. “This is about as close to a safe pesticide as you can get. You basically have to take a bath in it to have some effect.”

Wildlife Impact

Studies from the early 1980s on malathion’s effects on wildlife showed the chemical caused temporary outbreaks of insects harmful to plants and some fish-kills, primarily when the pesticide was applied during rainy weather.

Steve Dreisdedt, a senior writer with the integrated pest management project at UC Davis, said “quite a number of studies” showed that malathion was more toxic to beneficial insects, like stingless mini-wasps that kill aphids, than to harmful bugs like aphids, white flies and scales. The harmful insects tend to be spared because they are less mobile than the beneficial bugs and live on the undersides of leaves, which protects them from the pesticide.

He added that the pesticide probably will have no impact on the destructive ash white fly, which is killing many trees throughout Southern California.

Dreisdedt said the aerial spraying is “very unlikely” to cause bird poisonings because only extremely small amounts of the chemical are being dropped. “If it extended into the spring, when many birds depend on insects to feed their young, it could reduce food for young birds,” he said.

A 1982 study by the California Department of Fish and Game uncovered eight fish-kills in the south San Francisco Bay and creeks leading to it. Two of the die-offs occurred in dry weather: 140 fish were lost.

Another 2,300 fish, including striped bass and steelhead trout, died when the chemical was applied in rainy weather. Brian Finlayson, a Fish and Game official who worked on the study, said rain washed the chemical off streets into storm drains and eventually into creeks. As a result, the state no longer applies the pesticide from the air if there is a greater than 50% chance of rain within 48 hours of the application.

Los Angeles County supervisors, on a motion from board Chairman Ed Edelman, asked agricultural officials on Tuesday to study alternatives to spraying, including the possible release countywide of sterile flies, which are employed to breed fertile Medflies out of existence. County officials said a shortage of available sterile flies this week forced their decision to spray infested neighborhoods twice, rather than treat infested neighborhoods with only a single aerial application of malathion.

Monterey Park Mayor Patricia Rickenberg, one of the few elected officials to express qualms about the current application, said she does not want her city sprayed again in two weeks. She became worried when she noticed dead bees on her car windshield and backyard lawn last Friday morning, following a Thursday night application.

Joy Rowe said she became concerned about the effects of malathion when she, too, found dead bees and grasshoppers on her patio in Monterey Park last Friday, the morning after the pesticide was applied there.

“I saw these dead bees and thought, ‘Oh my God! This is killing all the beneficial insects, too.’ ” Rowe said. “There is a whole ecological balance that is being tampered with. And now they want to spray again? I don’t think they should.”

Times staff writers Stephanie Chavez and Richard Simon contributed to this report.