Calvert also tells WebMD, "I think it would be important to do surveillance wherever malathion is sprayed." However, much will have to change before that occurs. Only eight states currently have government-run pesticide surveillance programs of any type today, although up to 30 states require the reporting of suspected pesticide-related illnesses.
Of the 230 reported cases of problems, 107 were discounted due to a lack of information or because the symptoms being reported were incompatible with pesticide exposure. Without specific laboratory or environmental tests, the CDC does not classify any cases as a "definite" result of exposure, and no reports met this requirement. The balance, 123 cases, were thought to be either "possibly" or "probably" related to the malathion. These people experienced multiple problems, from nausea, diarrhea, and vomiting to problems with breathing, burning eyes, blurred vision, and skin rashes.
Malathion is also sprayed in Florida and other states to kill mosquitoes. It was used most recently in New York City to combat an outbreak of encephalitis caused by mosquitoes.
But the effects of the medfly spraying cannot be applied to malathion used for mosquitoes, Calvert contends. "The concentrations are pretty much equivalent. The difference is with the medfly, the application persists longer. The aerosol [for mosquitoes] dissipates in one hour. With medfly, the bait can persist for one to 30 days. We think, on average, it persists for four days. There is more opportunity for skin exposure." In addition, it isn't known whether the bait contributes some toxicity to the malathion. "The researchers weren't able to tease out what was causing" the symptoms, according to Calvert.
People should tell their physician if they have ever been exposed to pesticides in the environment or from their occupations so they can match symptoms to possible exposure, Calvert says. An acute reaction to exposure can include rapid tearing of the eyes, runny nose, and increased sweating.
"If it is a pretty heavy exposure, it can be fatal," Calvert says. "The problem with pesticide exposure is often the signs and symptoms are nonspecific. They might be diagnosed as upper respiratory infections and acute gastroenteritis," the symptoms of which include nausea, vomiting, and abdominal pain. If exposure is suspected, blood tests can be done to look for reduction of an enzyme called cholinesterase, he adds.