ANNAPOLIS – As the Maryland Department of Agriculture prepares to spray for mosquitoes across the state, public interest groups warned consumers about the possible health risks of some pesticides.
Two chemicals in particular – the insect repellent DEET, and the insecticide permethrin – have been the subject of studies suggesting they may cause brain and testicular damage when used in conjunction.
Permethrin is the chemical the Agriculture Department sprays to control adult mosquitoes, and the Department of Health and Mental Hygiene recommends using insect repellents containing DEET to prevent mosquito bites.
Studies performed by Mohamed Abou-Donia, a toxicologist at Duke University, showed that rats suffered damage to the testicles and the parts of the brain which control motor functions and movement, as well as memory, learning and concentration after being exposed to a mix of the chemicals for 60 days.
However, more studies need to be done on these chemicals, including studies involving shorter exposure times – a few days to a week – and recovery studies, where the test subjects are given a chance to recuperate after being exposed, he said.
Because of these concerns, the Maryland Pesticide Network recommends that people work to reduce mosquito numbers by eliminating the standing water where they breed rather than use pesticides, said Ruth Berlin, coordinator of the Maryland Pesticide Network.
The Agriculture Department’s Mosquito Control Section prefers eliminating breeding sites, and applying a biological pesticide to kill larvae over spraying for the adult bugs, but the pesticides are safe when used properly, said Patricia Ferrao, a section entomologist.
But, Berlin disagreed, saying “there is no such thing as a safe pesticide . . . they’re toxins, they’re made to kill.”
Abou-Donia’s studies “have no valdidity,” and permethrin is safe when used in accordance with directions on the product’s label, said Timothy Dickens, owner and chief executive officer of Scientific Coordination Inc., a company which develops permethrin technology for the Department of Defense.
Permethrin offers one of the best combinations in its class of chemicals of low risks and beneficial effects, particularly for preventing tick bites, although it is effective on mosquitoes as well, Dickens said.
Although DEET and permethrin are believed to be relatively non-toxic on their own, “it does really make sense . . . to look at them in combination,” said Lynn Goldman, a professor of environmental health science at the Johns Hopkins Bloomberg School of Public Health.
The research shouldn’t be taken as conclusive, and we don’t know that it means there could be similar effects in humans, but it would be prudent to pursue this line of inquiry, she said.
The Environmental Protection Agency does not normally require testing pesticides for chemical interactions before approving them for sale.