Commentary : Malathion Options Need Be Found
Aerial spraying of malathion in Orange County is expected to increase in frequency and area in the coming months, as efforts continue to eradicate the Mediterranean fruit fly. With the introduction of malathion into our environment come questions, some of which I will try, as a scientist and public official, to answer.
What Is Malathion?
Malathion is an organophosphate, one of a group of chemicals that functions by blocking nerve impulses--in other words, a nerve gas. In 1962, biologist and writer Rachel Carson pointed out that malathion is considered a less toxic compound because it can be detoxified by a liver enzyme. However, in 1984 James Warf reported that each exposure to malathion reduces the body’s ability to detoxify it. And, even before that, in 1969, the U.S. Department of Health, Education and Welfare warned that “skin penetration by organophosphates may be substantial. In view of the toxic potential of these compounds, protection of workers exposed to them assumes the utmost importance.”
Does Malathion Cause Birth Defects?
When malathion was injected into the yolk sac of fertile bird eggs prior to incubation as a test of toxicity, there was “not only a low percentage of hatch at a low level of the chemical tested, but there are also congenital abnormalities and other responses that raise extremely serious questions as to the safety to the consumers of any food contaminated with these chemicals,” Joseph McLaughlin reported in Toxicology and Applied Pharmacology in 1963.
Does Malathion Cause Cancer?
Cancer researcher Melvin Reuber, in reviewing the scientific literature on the carcinogenicity and toxicity of malathion in 1984, reported that cancerous growths on the endocrine organs, brain and liver, as well as ulcers, chronic renal disease and atrophy of the testes in laboratory rats had been reported. He observed that, “in tests undertaken to date, it has been demonstrated that virtually every chemical which has been found to be carcinogenic in humans is also carcinogenic in one or more mammalian test animals.”
Does Malathion Affect Other Living Organisms?
After the 1981-82 aerial eradication program in Santa Clara County, gardens in the area sprayed with malathion had more white flies, aphids and mites than did unsprayed gardens. Steve Dreistat and Donald Dahlsten, writing in the scientific publication Environment in 1986, observed that, “Malathion-bait sprays adversely affect pollinators such as honey bees. . . . Malathion is highly toxic to aquatic organisms--approximately 2,000 mosquito fish (gambusia) in Mission Creek were killed.” It should be noted that the Orange County Vector Control District stocks flood control channels with these fish to control mosquitoes.
Is Malathion Harmless at the Concentration Used in Spraying?
Dr. Marc Lappe, the principal author of the 1980 California Department of Health Services report “Assessment of Health Risks From the Proposed Aerial Application of Malathion in Santa Clara County,” refused to sign the final version, charging that it misrepresented his findings. “Various studies have suggested several potential adverse chronic health effects from exposure to malathion. These risks include birth defects, induction of genetic changes in germ cells and, perhaps, long-term effects on the nervous system. To my knowledge, none of this information has been made available to the public--I have never reached a decision as to what a safe exposure level is. For these same reasons, the World Health Organization declined to set a ‘safe’ limit for malathion in occupation settings. There have been omissions in the testing of this pesticide, and the United States Environmental Protection Agency, recognizing that fact, has ordered further studies concerning the long-term chronic effect of malathion exposure.”
Are There Other Means by Which the Medfly Can Be Controlled?
There are about 1 million insect species, and about 100 of those cause 90% of the damage to food crops. The ideal method of control affects only the target insect species, and a number of such controls are available. Sterile male fruit flies are being released, and that number should be increased. Chemical sex attractants are now available commercially for 30 major insect pests, including Japanese beetles. Such species-specific chemical attractants, or pheromones, should be developed for the Medfly. Other biological controls could include the introduction of predators, pathogens, parasites or viruses that affect the Medfly. Basic research in entomology should be initiated or accelerated by the California Department of Food and Agriculture.
Finally, a program of education that emphasizes personal responsibility for limiting the spread of the Medfly should be initiated immediately. Local elected officials, the Orange County Agriculture Department and the State Department of Food and Agriculture must cooperate with citizens of Orange County in this effort.
