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NCCOS Project

Risk Assessment of Mosquito-control Agents

This project began in January 2007 and is Ongoing

We are identifying the toxic effects that mosquito-control agents may have on estuarine species and the coastal environment. The information we gather is being placed in a database of mosquito-control products, to include chemical properties, application rates, and toxicity data, that will be continuously updated and shared with coastal resource managers. Ultimately, the program will enhance both mosquito-control product selection and management strategies for competing coastal resources.

Why We Care
More than 2,500 mosquito species exist worldwide, with approximately 200 species occurring in the United States. Many of the insecticides used to control mosquitoes pose a risk to coastal ecosystems, especially when used in large-scale applications (via plane or truck). These chemicals can migrate to the coastal environment through spray drift and surface water runoff, and they may damage sensitive estuarine species. Commercial shellfish growers have expressed concerns regarding potential effects of mosquito-control pesticides on their nursery and hatchery operations.

What We’re Finding
To date, we’ve found that certain aquatic species are more sensitive to these chemicals than others. Grass shrimp are more sensitive than are fish to most mosquito-control compounds, and clams, oysters, and algae are relatively insensitive. We have also found that some chemicals are more toxic to a species’ larval stages of life than its adult form.

Our survey of regional county mosquito abatement programs has shown that most adult mosquito control programs use organophosphate chemicals, such as naled, and pyrethroid compounds, such as resmethrin. For controlling mosquito larvae, methoprene (the juvenile hormone mimic) is most commonly applied. At present, 28 mosquito-control agents have been entered into the database.

What We’re Doing
Our project focuses on the toxicity of mosquito-control compounds in estuarine organisms. Specifically, we’re studying the effects of compounds on survival, growth, and cellular function in fish, shrimp, clams, oysters, and algae. In addition, we’re looking at the effects of these compounds on the larval and juvenile life stages of estuarine fish and shellfish. The database will evolve continuously to include new compounds and changes in application patterns to provide coastal managers the most current toxicological risk assessment data.

Next Steps
We will continue to test the effects of different mosquito-control agents on estuarine organisms, using longer chemical exposures to look at effects on growth and reproduction.

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