West Nile and the environment

Now that West Nile virus has been reported here in the Bay Area and elsewhere in California, it is important to make informed public-health decisions.

Spraying doesn't work

Spraying is not an effective or efficient way to prevent death or illness associated with insect-borne West Nile virus.

A large part of this has to do with the life cycle of mosquitoes and their biology. Another large part has to do with the inability, especially in an urban environment, to hit target insects with typical ground spraying from trucks or by aerial application.

For example, on the night of Aug. 4, workers from the Greater Los Angeles County Vector Control District used pick-up trucks to spray resmethrin, a synthetic pyrethroid designed to kill adult mosquitoes, along two riverbeds where infected mosquitoes and birds had been found, according to the District. Officials had expected the pesticide would kill about 70% of adult mosquitoes in the area, but this did not happen. According to Minoo Madon, District scientific-technical-services director, monitoring revealed that the pesticide did not kill 70% of mosquitoes. Madon would not disclose the actual percentage killed, but said, "Let's just say the results were not satisfactory." Madon suggested that a stiff breeze might have prevented the spray from actually reaching the mosquitoes.

While recognizing the public health threat of West Nile virus and other mosquito-borne diseases, but given the limited efficacy of pesticides meant to target adult mosquitoes, it is important to weigh the public-health hazards associated with widespread pesticide exposure. The pesticides most commonly used across the country are neurotoxic and have been linked to cancer and other illnesses. People with compromised immune systems, chemically sensitive people, pregnant women, and children with respiratory problems, such as asthma, are particularly vulnerable to these pesticides and will suffer disproportionately from exposure.

Even under ideal conditions only a small amount of these pesticides ever reaches the target pests, they do little to restrict breeding in adult mosquitoes, and mosquitoes can become resistant to them, on top of dangers to humans and the environment.

It is important for local governments to provide accurate public education and safe, long-term solutions. More effective mosquito-management techniques include increased public education, elimination of breeding grounds, personal protection, and the use of larvicides to kill mosquito larvae before they become biting adults.

Wetlands

There are many misconceptions about the relation between wetlands and mosquito problems. In fact, restoration of tidal wetlands can reduce mosquito populations, as tidal fluctuations keep water moving so that mosquitoes do not have standing water in which to breed. Tidal marshes do not provide good habitat for the two most troublesome mosquito species.

Non-tidal wetland restoration can be designed to provide drainage or keep water moving so that it does not become stagnant and become a breeding ground for mosquitoes.

What You Can Do

You can help prevent the spread of West Nile virus by eliminating all standing water around your home.

Wear long, light-colored clothing and use mosquito repellent when spending time outdoors. Consider avoiding the outdoors during peak mosquito biting times at dawn and dusk.

For more information on pesticide hazards and West Nile, see the web site of Beyond Pesticides at www.beyondpesticides.org

If you are concerned about the spraying of pesticides in your community or local environment, want a copy of Beyond Pesticides' organizing packet, or want to get involved in any way, please act now and contact Shawnee Hoover at Beyond Pesticides at (202) 543-5450 or email shoover -at- beyondpesticides.org