Aldicarb Sulfoxide : Routine Tests Don’t Detect Melon Poison

Routine tests used by state inspectors to screen for pesticides on fresh fruit are not designed to detect the chemical that tainted thousands of watermelons and prompted a statewide epidemic of food poisoning, a top state agriculture official has acknowledged.

In an interview with The Times, Lori Johnston, assistant director of the Department of Food and Agriculture, said that even had the department’s inspectors tested one of the poisoned melons before the epidemic, the fruit would have been certified as edible and sent to market.

“Our screening methods do not screen for the breakdown products of the chemicals,” Johnston said. “We don’t have that kind of capability yet. That would be ideal.”

The state’s tests, she said, can pick up signs of the pesticide aldicarb, which is sold under the brand name Temik and is suspected of having been applied illegally to 23 California watermelon patches. The tests do not check for signs of aldicarb sulfoxide, the substance formed when the pesticide breaks down in the soil. It is aldicarb sulfoxide that has been blamed for causing a flu-like illness in at least 281 people who ate the tainted melons before they were pulled from supermarkets last week.

Once inspectors suspected that aldicarb sulfoxide had caused the epidemic, they were able to use a special test designed to check for that chemical. That test is being used this week in a state laboratory here to check about 3,500 sample melons pulled from patches across the state.

Dr. Peter Kurtz, the department’s medical coordinator, said the test now being used is ineffective for routine screening inspections because it checks only for aldicarb sulfoxide and would miss other toxic chemicals. Some environmentalists contend, however, that this shows that the state’s inspection system is fundamentally flawed.

Kurtz said the routine tests--which involve mashing and dissolving the fruit and placing it in an instrument to measure levels of pesticides--are used primarily to find excess levels of chemicals that are legal within certain limits. They are not designed to pick up evidence of prohibited chemicals.

“You can’t look for every chemical; it would take too long,” Kurtz said. “It’s a matter of logistics, of whether your lab can run tests for every chemical known to exist. The program is directed at that which is most likely to produce a payoff.”

Loophole in Law

Aldicarb is not legal for use on watermelons, but a review of Kern County permit procedures shows how it would be relatively easy for a farmer to obtain the chemical and use it on watermelon crops without following reporting requirements.

The Temik label says that 14 to 27 pounds of the chemical are needed for an acre of cotton, the crop for which it is normally used in Kern County. A grower, then, could report to a county agriculture commission that he had bought enough Temik to use 27 pounds for each acre of cotton. He could then use less than that amount on cotton and save the extra pesticide to use illegally on watermelon or other crops.

To combat such potential misuse, the Department of Food and Agriculture’s 400 inspectors routinely sample about 8,000 pieces of produce from wholesale markets each year. Rex Magee, the department’s associate director, said 20 to 25 watermelons are put through these “residue tests” annually.

Clare Berryhill, the department’s director, said this week that he may ask for more inspectors in the department’s pesticide and dairy enforcement branches in the wake of the watermelon scare and the recent contamination of Mexican-style cheese with a deadly bacterium that has been linked to 60 deaths.

‘A Little Complacent’

“I think we haven’t had problems in the past and we were maybe a little complacent as far as how many people we needed to do all these programs,” Berryhill said. “It’s a strong possibility we’re going to come back and ask for additional enforcement people.”

Environmentalists who have been critical of the state’s pesticide monitoring program contend that more inspectors, while helpful, will be of little value unless the state begins testing for the pesticides’ breakdown products.

Ralph Lightstone, an attorney with the California Rural Legal Assistance Foundation, said he believes that the screening program is “fundamentally flawed” if it cannot detect the poisons that are formed when pesticides break down. Often, he said, it is these metabolites and not the pesticide itself that are meant to kill the pests.

“If the program designed to monitor pesticides is missing the metabolites, then the public has no assurance that the food, water and air are safe,” Lightstone said. “It means the program has broken down and isn’t working.”

‘Even More Toxic’

Lawrie Mott, a scientist with the Natural Resources Defense Council, said: “The state assumes blithely that if you test for the parent compound and don’t find it, then there’s no cause for concern. In fact, the breakdown products may be even more toxic.”

Federal inspectors working for the U.S. Food and Drug Administration do have the ability to test routinely for such breakdown products, including aldicarb sulfoxide, according to Milton Luke, supervising chemist for pesticides in the agency’s Los Angeles office.

Luke said the FDA, which inspects produce that enters or leaves the state, uses different tests at different times of the season in an attempt to check for as many chemicals as possible.

“We deal with a vast amount of Mexican produce, and I have no idea what’s on that,” Luke said. “I try to vary the tests, rotate them around. I try to look for all the residues.”