New research suggests a common insecticide may be contaminating the sediments accumulating urban wetlands. Photo by UPI/NOAA | License Photo

June 28 (UPI) -- Researchers in Australia are concerned about the dramatic rise in bifenthrin concentrations in wetland sediments. Bifenthrin is a common insecticide chemical, and the latest research suggests the contaminant is harming aquatic life.

Environmental scientists at the University of Melbourne didn't measure contaminant levels in water samples, but in sediment samples collected from the bottom of wetlands in and around the city of Melbourne. The research team identified a variety of chemicals that can harm underwater bugs growing and living on the wetland floor.


Bifenthrin is found in a wide range of insecticides, both for commercial and domestic use. It is toxic to insects, spiders, mites and fish. Testing suggests the chemical is relatively safe for humans and other mammals.

The insecticide is long-lasting, which makes it effective in killing insects, but problematic when the chemical seeps into the environment.

In 2012, Melbourne researchers found bifenthrin in just 20 percent of wetland sediment samples. Most recently, scientists found toxic levels of bifenthrin in 75 percent of sediment samples. Of the 99 samples collected and analyzed, 40 boasted levels toxic enough to kill an amphipod, a common waterbug.

Researchers detailed their more recent findings in a new scientific paper, published this week in the journal Environmental Science and Technology.

The paper's authors aren't entirely sure where all the bifenthrin is coming from. The insecticide isn't water soluble, so it shouldn't wash away with storm runoff. It can attach itself to dirt and dust particles and get carried away by runoff, but in Melbourne, stormwater runoff passes through a variety of filtration systems to ensure toxin-carrying particles are removed.

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Researchers say more work needs to be done to identify and curb sources of bifenthrin. It's a problem unlikely to be isolated to Melbourne.

Researchers suggest other environs are likely to be experiencing similar spikes in problematic insecticides, including reports that scientists have identified rising bifenthrin concentrations in California.