Genetic Damage From Malathion Cited by State Science Panel : Health: But experts say there is still not enough information to determine if the pesticide can cause birth defects or cancer.

A panel of scientists has concluded from a review of existing scientific studies that malathion can cause increased chromosomal damage in laboratory cell cultures, animals and possibly humans. But it said there is insufficient data to determine the significance of the genetic damage, especially whether it would result in birth defects or cancer.

The scientists, who reported their findings at a meeting in Los Angeles on Thursday night, said the existing studies indicate a potential for malathion to be more harmful to humans than previously suspected.

“It’s disquieting to have these results,” said Kim Hooper, a state Department of Health Services biochemist and the chief author of the report. “But we don’t know what they mean.”

Bruce Ames, director of the National Institute of Environmental Health Sciences Center at UC Berkeley, cautioned against an overreaction to the announcement, saying that almost any chemical in a high-enough dosage will provoke some genetic damage.

“If you don’t get enough vegetables, that will break chromosomes,” Ames said. “A cup of coffee is filled with things that break chromosomes.”

Meanwhile, it was announced Friday that two more Medflies have been found--this time in San Bernardino County. No decision has been made on whether the discoveries will force more aerial applications of malathion.

Hooper said the assessment was based on a review of dozens of scientific studies that have been primarily conducted over the last decade. The report was presented at a meeting of the state’s Public Health Effects Advisory Committee. Twenty-three doctors and scientists voluntarily serve on the committee, a special panel convened this year to review health studies concerning malathion.

The existing studies that were reviewed rely on a series of sensitive laboratory tests, first developed for cancer research, that look for abnormal breaks, gaps and mutations in genes and chromosomes. The abnormalities reported in the studies frequently occur in nearly all forms of life and usually do not translate into cancer or physical defects.

Although the studies did show a greater number of abnormalities than commonly found, Hooper said other studies largely cleared malathion of causing birth defects or cancer, indicating that the abnormalities may not be significant.

Hooper said it is still difficult to determine how relevant the genetic studies are to understanding the hazards of malathion spraying.

He said the animal and cell culture tests generally involved near-lethal doses of malathion, making their relevance to aerial malathion spraying uncertain. Under the current aerial spray program, the state drops 2.8 ounces of malathion over each acre. The pesticide is contained in a harmless bait.

Human studies on laborers who spray pesticides also have shown increased chromosomal damage, although the studies were tainted by a lack of information on the workers’ exposure to other chemicals. Hooper said the studies also inadequately considered outside factors that could affect the outcome, such as whether the workers were smokers or drinkers.

Hooper and several other scientists from throughout the state, including USC biostatistics professor Duncan C. Thomas and UC Berkeley toxicology professor Martyn Smith, have recommended a new study of residents and workers involved in the current aerial spraying campaign in Southern California to resolve the questions about whether low doses of malathion cause genetic damage.

Meanwhile, officials announced Friday that a single immature female had been trapped in a lemon tree Tuesday in a residential section of Upland, about 30 miles east of Los Angeles. Then on Wednesday, another immature female Medfly was trapped in an orange tree in the city of San Bernardino.

The Medfly in Upland was found four miles away from where another Medfly had been trapped in Alta Loma last September.

State agriculture officials said that no decision has been made on whether aerial spraying of malathion will be ordered in the area.

Rex Magee, associate director of the state Department of Food and Agriculture, said the number of flies trapped is still small and no reason for serious concern.

“I’m not worried yet,” Magee said. “This will have no affect.”

But some members of the state’s panel of scientific advisers in the eradication campaign said the discoveries, along with another find this week in Rowland Heights, indicate that the pest is returning in surprising numbers despite a massive eradication effort in Los Angeles and Orange counties.

“It looks like they are all over out there,” said James R. Carey, a UC Davis entomologist and a member of the Medfly Science Advisory Panel.