In the wake of millions of dollars in damage claims and charges of a scientific cover-up, state officials have begun to consider a test of the long-term effects of 160,000 gallons of Mediterranean fruit fly insecticide sprayed over Californians in the last year.

California faces enormous economic losses if the Medfly is not eradicated, and government officials, bolstered by reports from top scientists that Malathion does little harm in small doses, have been unusually sensitive to any statements that might create more public protests to use of the pesticide.

Dr. Melvin D. Reuber, a board-certified pathologist whose work helped lead to a federal ban on two other pesticides, said he was forced to resign from a government research laboratory last year after he challenged research that led to a National Cancer Institute conclusion that Malathion did not cause cancer.

A letter from Reuber's supervisor said his "obstreperous actions" had a "multimillion-dollar implication" for California's agriculture industry, the state's leading money-maker.

A California state pathologist, Marc Lappe, was removed as head of the hazard evaluation unit of the health services department after he publicly disclosed an internal study that made Malathion look riskier than the department had said it was.

Lappe's research unit had initially reported that the spraying posed minimal risk to humans, but he said in a recent interview that the assessment was based on six Malathion sprayings, not the 15 sprayings that have been carried out in some parts of the San Francisco Bay area.

Lappe is working on a National Science Foundation-funded project at the University of California at Berkeley. A spokesman for the state health services department said Lappe was removed as unit chief because of "administrative problems," not because of his criticism of the department's Malathion report.

State officials, who did a spot survey of hospital emergency rooms and a telephone survey of 127 residents inside and outside the spraying area, say there is no indication that health complaints increased after the sprayings. But they say they are interested in exploring long-term effects of the pesticide if the legislature will provide the money.

Although the number of reported cases of harm from Malathion spraying appears to be relatively small, it indicates that some individuals may react violently to a very small exposure to the chemical.

Ruth Lindsey, 51, a supervisor for Pacific Telephone, said that three days after Medfly project helicopters sprayed over her San Jose home her face had "this terrible tingling, the same as in your arm when it goes asleep." She said her face turned red and swollen and that she suffered headaches and nausea that caused her to miss 47 days of work.

She has filed a $1 million claim against the state, backed by affidavits from two doctors attributing her symptoms to Malathion. More than $10 million in damage claims have been filed against the state, most charging automobile damage, but many also making health complaints.

Amanda Hawes, 38, a San Jose attorney who has handled many of the claims against the state and is an activist in Campaign Against Spraying, a group formed in the San Francisco peninsula area, said one of her small children developed sudden loss of appetite and vomited after a spraying.

She and her family arranged to stay with friends in an unsprayed area whenever helicopters sprayed over her neighborhood, "but after doing that 12 weeks in a row it tends to get on your nerves," she said.

Malathion is an organophosphate, chemically related to nerve gas, which kills Medflies by acting on their nervous system.

James Mahoney, special assistant to the director of the state health services department, said the state has invited two Massachusetts researchers, Dr. Frank H. Duffy of the Harvard medical school and David Culver of Braintech Inc., to study the long-range effects of exposure to the pesticide.

Work by Duffy and James L. Burchfiel, based on studies of monkeys and 77 workers accidentally exposed to a similar chemical, shows "long-term change in brain function in both monkey and man," according to their article in the scientific journal Neurotoxicology.

Culver's firm employs a new technique, called BEAM for Brain Electrical Activity Mapping, which provides unusually sensitive computer-analyzed electroencephalogram readings.

Duffy said his studies indicate that the change in brain activity caused by exposure to organophosphates can produce excessive dreaming, altered sex drive, memory loss and irritability. Other studies indicate that even if the exposure is slight, as in Malathion spraying, the effects may be cumulative after several exposures.

Duffy, in a telephone interview, said he was preparing a proposal for a controlled study of the spraying effects in the San Francisco Bay area.

But there will be difficulties, Mahoney said. Potential subjects might be distressed to learn that they have some apparent brain disorder, he said, and the BEAM system has never been used to measure the effects of pesticide spraying in very small doses.

"There is also a serious question whether such a study would be financed," Mahoney said. He said the legislature has killed funds for an expanded survey of cancer cases in the spraying area.

Reuber, the Maryland scientist who resigned from the Frederick Cancer Research center last year, said he questioned three animal studies that led to a National Cancer Institute conclusion that Malathion did not cause cancer.

In reassessing 24,000 tissue slides from rats and mice in the studies, he concluded that benign and malignant tumors occurred in significantly greater numbers in animals that had received the pesticide over a long period of time.

When Reuber passed on his findings without authorization to the director of the California Food and Agriculture Department, he was severely reprimanded by Dr. Michael G. Hanna Jr., the cancer research center director.

Now a consultant based in Potomac, Md., Reuber said he knew of no attempt since to make an official review of the cancer and Malathion studies as recommended by several other pathologists.

A spokesman for the National Cancer Institute said some of the data from the studies was difficult to interpret, and that researchers are considering a reassessment of some conclusions.