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Daily News Archive
From October 31, 2006                                                                                                        

Colorado Town Bends To Public Pressure on Malathion
(Beyond Pesticides, October 31, 2006) Several years of public pressure has resulted in a decision by the mosquito district of Paonia, Colorado, to stop the use of malathion for adult mosquito control. However, the use of the remaining stock of the pesticide and future mosquito control practices are still up for debate.

Bill Kolb, president of the mosquito district board that serves the towns of Paonia and Hotchkiss, told the Grand Junction Daily Sentinel that letters to the editor and appearances at board meetings by Paonia citizens helped him decide to switch to a more natural-based substance. Mr. Kolb also stated that the mosquitoes may have built up some immunity over the last five years it has been used.

Mr. Kolb conveyed to the Daily Sentinel that he’s not convinced malathion causes health problems. “There’s nothing concrete that it does do the bad things they’re saying it does,” he said. He continued that only three barrels of malathion were used this year, and most mosquito control was done through killing the insects at the larval or pupal stage.

However, there are two remaining barrels of malathion. If the board can return these to Schall Chemical for a refund, they will not fog with malathion again. However, there is a possibility that malathion will be used for one more season. A replacement adulticide will be named this spring.

Malathion is a broad spectrum organophosphate insecticide used to control pests in agricultural crops, around domestic and comercial buildings and landscapes, and in public health mosquito control programs. Malathion targets the nervous system of insects by inhibiting cholinesterase (ChE). Malathion is classified as having “suggestive evidence of carcinogenicity,” and published literature studies have shown that malathion can affect immune function, among other health effects.

Malathion is mobile in soil and can leach into groundwater and surface waters and impact public water supplies. Malaoxon, the breakdown product of malathion, is estimated to be 61 times more toxic to adults than malathion. Malaoxon is also formed during the water treatment process. According to the Environmental Protection Agency's (EPA) recent Reregistration Eligibility Decision (RED) for Malathion, limited monitoring information indicates that conversion from malathion to malaoxon during the water treatment process may be as high as 100% and the chemical can remain stable for 72 hours, which is within delivery times for some publicly owned treatment works.

Data collected by the Florida Department of Agriculture and Consumer Services Bureau of Pesticides (1997) showed only concentrations of malathion entering the Hillsboro Water Treatment Plant and, following the treatment process, only concentrations of malaoxon exiting the plant. Once converted, malaoxon may remain stable in treated water long enough to be available at the tap for direct consumption.

Local residents disagree with the mosquito control district’s assessment of malathion effects. Dinah Lindarin of Paonia blamed malathion for the death of her dog from lung cancer in a letter she wrote to the Delta County Independent, the area’s local paper. Ms. Lindarin also said spraying malathion is “extremely ineffective” and just makes mosquitoes more aggressive.

Paonia residents filed four complaints to EPA in the last five years with no result. Now, oversight of the mosquito district will be under the Department of Agriculture. A biological larvicide will be used when mosquito control starts up in April, Mr. Kolb said, followed this summer by an adulticide that will be approved by the Department of Agriculture.

Laura Hepting, a Paonia native now working as special projects coordinator for Beyond Pesticides, says, “Mosquito spraying is hotly debated in Paonia – the town is very polarized over the issue. While some people in the next town over want their property to be included in the spray zone, others literally head for the hills on the night the truck is scheduled to pass by their homes. There really needs to be an open dialogue here and a comprehensive effort to work on effective alternatives to malathion and adulticiding in general, such as reducing the ample mosquito breading areas that exist in the North Fork Valley.”

Paonia is not alone. Local municipalities across the country are working to find ways to improve mosquito control practices. Find out more through the Alliance for Informed Mosquito Management.