Malathion Controversy

Recently I was interviewed by Michael Balter on the matter of risk assessment and he struck me as an intelligent and well-intentioned journalist. But I think his Aug. 11 Op-Ed piece, “Drops of Mistrust Cloud Malathion Spray,” was much more misleading than any of the public reassurances he so vigorously attacked.

Our department funded the USC study he discussed, yet I hardly recognize it from his description. He failed to tell your readers that this large study of malathion did not show even a hint of extra risk for sensitive toxic indicators such as premature labor or intrauterine growth retardation. There was no significant extra risk of miscarriages (which is also thought to be a sensitive early indicator of toxicity) or for the totality of birth defects taken together. These measurements were the study’s strong points, the areas in which it was quite sensitive.

Yet Mr. Balter chose to emphasize to your readers some very weakly positive results which the study’s author did not view as biologically credible.

Of course it is true that epidemiological studies cannot absolutely rule out any risk from a product. Indeed, no kind of scientific study can do this.

But Mr. Balter’s very selective account of the USC study has probably convinced most of your readers that malathion as applied in Los Angeles is dangerous to them, and that public officials have been hiding incriminating evidence. I believe that neither assertion is true.

The fact is that the USC study is as big and as good an epidemiological study as you are ever going to get. Taken together with what we know about the low exposure from malathion protein bait (it’s not a liquid spray) and the balance of the biological evidence (it’s been used to treat head lice in England), a lot of well-trained scientists who have dedicated their careers to public health happen to think that aerial application of malathion to control Medfly is safe for public use.

I regret that Mr. Balter thinks that this evaluation of safety is “exaggerated” or “misrepresents” the evidence. Your readers should know, however, that he has treated them to a very selective and filtered picture of that scientific evidence.

Dr. RAYMOND R. NEUTRA, Chief Epidemiological Studies Section

Calif. Dept. of Health Services