El Cajon Braces for Threat From the Partly Known

There’s plenty of heat but a lot less light in the discussions over whether El Cajon residents might be harmed by aerial spraying of malathion to kill Mexican fruit flies.

Unless El Cajon Municipal Judge J. Michael Bollman rules today in favor of a suit filed Friday to halt the action, six Bell 204 helicopters will begin spraying a sticky malathion mixture over a 16-square-mile area tonight. The only certainty then is that the spraying will be noisy and, for some residents, frightening.

To calm those fears, science can offer only probabilities, observations and inferences about risk:

It looks as though malathion does not have serious short-term effects on humans who breathe it, swallow it or have it on their skin in small amounts.

It looks as though malathion does not affect development of fetuses.

It looks as though malathion does not trigger cancer, but more studies are needed to be sure.

On the other hand, key studies about the effects of chronic exposure to malathion are lacking. The best anyone can do is point to chemical industry workers who have worked with malathion for 20 years or more; those people show no untoward health effects, their bosses say.

At least 1,000 studies have been published on the pesticide since it was first marketed by American Cyanamid Co. in 1952.

Some studies are so narrowly focused that extrapolating their results to humans is difficult or even silly. (What relevance do genetic mutations in bacteria bathed in malathion have to people?) Other studies of cancer and birth defects used faulty or outdated methods and, consequently, are in doubt today.

What most of these studies share is that they were done after the fact. Malathion became a mainstay insect killer for farmers and home gardeners long before the studies were even conceived of.

Malathion use also became widespread long before the dawning of an environmental consciousness that underlies today’s safety standards for pesticides.

Indeed, it wasn’t until recently that the U.S. Environmental Protection Agency--which didn’t exist when malathion was first used--decided to conduct further studies of whether the pesticide triggers cancer or birth defects. Those studies won’t be complete for another four years.

Nonetheless, the California Department of Food and Agriculture confidently states in the flyer going out to El Cajon residents: “Health authorities agree that, at this extremely low dose, pregnant women have no cause for concern.”

Public officials and agriculturists base this on the fact that study after study reveal very few short-term effects from malathion--and only at exposure levels that are massive compared to the amounts that would be dropped tonight.

The problem for people concerned about malathion raining down from the sky is that, to some of them, even a little bit of exposure to the chemical is too much.

But the scientific literature on malathion is far less emphatic than its critics are.

One study fed 10 volunteers 16 or 24 milligrams of malathion every day for 1 1/2 to 2 months. No negative effects.

Another put men in a room into which malathion was sprayed at initial concentrations of 5 to 85 milligrams per cubic meter of air. No negative effects. (Concentrations in the air during Medfly spraying have been about 1 microgram per cubic meter, the state reports.)

In another study, volunteers dusted themselves and their clothes with 90 grams of malathion powder five days a week for as long as 16 weeks. Two subjects complained of skin irritation. Only the volunteers using 10% concentration of malathion showed any suppression of normal neural activity.

In the latter experiment, the amount of malathion taken in through the skin before minor neural effects appeared was 2.8 grams of malathion per day.

Consequently, since they will drop only about .002 of a gram of malathion on each square foot of the targeted area of El Cajon, officials don’t see any need for people in the copters’ path to be concerned about their health.

Furthermore, the droplets from the helicopters will be about 10 microns across, too large to penetrate deep into the lungs, officials say.

Bill Routhier, the state Department of Food and Agriculture official who is overseeing the spraying, is confident enough of the state’s position that he plans to take his daughter along while he monitors the spraying Monday night.

Malathion is a phosphate-containing organic chemical that is regarded in the pesticide industry as posing very little potential damage to the nervous system.

It is used wherever insects can be a problem: on food and crops and flowers, as a spray inside large shipping or storage containers for grain, as a remedy for lice and for mosquito control.

If malathion has a bad name, industry spokesmen say, it’s because of other, much more neurotoxic organophosphates such as parathion, developed since malathion went on the market.

On contact with water or water vapor in the air, malathion begins breaking down. Under mild Southern California weather conditions, half the malathion to be sprayed will decompose in the environment within as little as two days, officials say.

Initially, this breakdown produces malathion’s toxic byproduct, malaoxon, and acidic chemicals that some people blame for the skin and eye irritation they experience when exposed to malathion.

The malaoxon is the chemical about which critics of malathion-spraying worry the most. Called a cholinesterase inhibitor, malaoxon blocks the body’s normal system of allowing muscle cells to relax after they contract.

Malaoxon does this by binding chemically to the enzyme cholinesterase. In the absence of active cholinesterase, the neurotransmitter chemical that tells muscle cells to contract persists in the body.

Insects suck up the malathion sprayed on plants, and the malaoxon triggers enough of this cholinesterase blocking that the insect becomes paralyzed and dies.

In mammals, massive cholinesterase blockage would slow the heart and make breathing difficult, since the diaphragm would not be able to move in and out. Milder cases are characterized by nausea, vomiting and dizziness, with victims giving off a malathion odor.

Death can result but is rare. Even in cases when suicidal people have deliberately ingested malathion, its effects were reversed with with drugs.

In addition, the human liver contains enzymes that naturally break down malathion and malaoxon--thought to be the reason that human tolerance for the pesticide is higher than that of insects.

Effects of chronic exposure to malathion are unclear.

“Although the agency possesses a number of studies on the chronic effects of malathion and its principal metabolite, malaoxon, several of these studies are deficient scientifically and must be repeated,” the EPA says in its fact sheet on malathion.

This document concludes that only three of five cancer studies in rats and mice are scientifically acceptable as having shown no carcinogenicity. Studies of birth defects in rodents were largely unacceptable, it says.

In human studies, two projects analyzing birth defects in children conceived during the 1981-82 malathion spraying campaign in Northern California found no serious problems. But the authors conceded that subtler effects would not be detectable by the studies because the number of deformities in some cases was too small.

Earlier this month, a state panel of health experts in charge of reviewing scientific information on malathion reported that early evidence suggests that the pesticide causes genetic damage in laboratory cell cultures, animals and humans.

Kim Hooper, the chief author of the report, called the evidence “disquieting.” But he added that some of these genetically damaging doses were near lethal levels. Whether the genetic damage may result in birth defects or cancer is uncertain, he said.

Critics of spraying in the Los Angeles area have complained that the malathion flights killed off bees, aphid-eating ladybugs and other insects directly beneficial to humans.

State agriculture officials have relied on several studies of insect and wildlife populations conducted during the 1980-82 Medfly eradication program in Northern California as proof that spraying causes no irreparable harm to the environment.

Those University of California studies showed that some species of beneficial insects suffered only temporary population reductions.

But three entomologists who worked on the studies now say the results are ill-suited for the current sprayings because of climatic and geographic variations between Northern and Southern California. Also, they say, the studies focused on only a few insects and were funded for only a year, preventing long-term analysis.

“It is simplistic for the state to say that you expect things will bounce back. How do you know?” said Donald L. Dahlsten, a professor of entomology and chairman of UC Berkeley’s conservation and resource department. “You must monitor, do long-term studies to see what the effects are. . . .”

His “best scientific guess” is that some plants will die from insect infestation while others will recover. But Richard L. Tasson, a UC Berkeley entomologist also involved in early-1980s malathion studies, found no documentation “of massive eradication of beneficial insects and an explosion of pests. . . . “

Still, scientists involved in the earlier studies say that a unique opportunity to understand more about the interaction of beneficial insects and pests has been lost by the state’s failure to fund more research.

State officials say that no fish or wildlife kills have been linked to malathion. Although there have been no studies examining whether malathion can sicken wildlife, state officials recently were forced by federal officials to reduce about five square miles of their planned Woodcrest spray zone in Riverside--home to the endangered Stephen’s kangaroo rat.

State officials were forced to make the move because they have no data proving that malathion would not harm the small animal.

When the helicopters start spraying El Cajon tonight, perhaps the biggest inconvenience will be from noise, said project manager Routhier.

In the Los Angeles area, residents complained of children being wakened and pets being terrified by the noise.

The six copters are from San Joaquin Helicopters in Delano, the same company used in Los Angeles. The aircraft aren’t modified to cut down on noise, Routhier said.

They will fly in formation from east to west across the 4-by-4 mile area, beginning in the north. Spraying is scheduled to take place between 9 p.m. and 1 a.m., but Routhier said he hopes it can be completed in two hours.

CAMPAIGN AGAINST THE MEXFLY

There are three nozzles on each side of the helicopter.

The bait-pesticide mixture is a combination of 2.8 ounces of malathion for every 12 ounces of the mixture.

The mixture is sprayed at a pressure of 20 psi, and dispenses at a rate of 3 gallons per minute.

FLYING IN FORMATION

The helicopters fly at 80 mph, and at an altitude of 500 feet.

Six Bell 204 helicopters will each carry 1 45-foot boom. The pipe is 1.5 inches wide.

MALATHION TARGET AREA AND PRECAUTIONS

TIPS FOR RESIDENTS

Cover cars, since sticky protein bait mixed with malathion can damage a car’s paint.

Cover lawn furniture or other outdoor items.

If items are sprayed, wash them no later than the following morning to prevent permanent spotting.

Stay inside during spray times, between 9 p.m. and 1 a.m.

Officials say pets can stay outside, but some owners prefer keeping them inside.

State officials say swimming pools may remain uncovered.

Fish are killed quickly by small amounts of malathion. Cover ponds during spraying but uncover shortly afterward to prevent oxygen starvation.

Outdoor aviary owners may harm birds if they cover cages, since birds are more frightened by helicopter noise if covered.

State says no special precautions needed, but some doctors advise asthmatics, cardiac patients on beta-blocker drugs and pregnant woman to stay outside spray area for 12 hours.

HOW MALATHION WORKS

Malathion is called a cholinesterase inhibitor because a byproduct of it, malaoxon, blocks the enzyme that breaks down acetylcholine in the body. Acetylcholine is used by nerve cells to send signals to each other and also to muscle cells. The amount of enzyme blockage depends on the dose of malathion given.

Normal:

1. Nerve call releases acetylcholine, signaling muscle cell to contract.

2. Enzyme called cholinesterase deactivates acetylcholine by attaching to it.

3. Muscle relaxes.

With Malathion present:

1. Nerve cell releases acetylcholine, signaling muscle cell to contract.

2. Malaoxon attaches to cholinesterase, preventing it from acting on acetylcholine.

3. Muscle cell cannot relax.