Daily News Archive
From September 10, 2001

Dangerous Chemical Combinations Used to Prevent West Nile Virus

Two chemicals commonly used to prevent West Nile virus are a dangerous combination. A recent scientific study showed that Permethrin, a pesticide used to kill adult mosquitoes, combined with insect repellents containing DEET causes cell destruction in rats. Dr. Mohammed Abou-Donia, a Duke University pharmacologist and co-author of this study, recommends that DEET should not be used with other chemicals or by people who are taking medication.

In response to recent human illnesses from West Nile virus, Maryland is spraying permethrin to rid areas of mosquitoes carrying this disease. And state health officials are advising that citizens wear DEET to protect themselves from mosquito bites. While they have stated that this product should only be applied to clothing, it is too difficult to ensure that everyone will follow those instructions.

Dr. Abou-Donia is concerned these chemicals are not only used in areas where there are healthy people, but are used where there are infants, children, and pregnant women. These and other vulnerable populations have a higher risk of becoming ill due to pesticide and DEET exposure. Several cases of DEET poisonings have been reported by EPA, including three fatalities.

Rather than use repellents containing DEET, Beyond Pesticides recommends using products containing geraniol (MosquitoSafe), citronella (Natrapel), or a combination of soybean, geranium and coconut oils (Bite Blocker). These are safer, effective mosquito repellants, but may need to be reapplied throughout the day.

Although the Environmental Protection Agency tests individual chemicals, they do not test the synergistic effects of using combined chemicals. More studies should be conducted to determine negative health effects of combined chemicals.