2008-04-17 / News

Are pesticides killing Rhode Island lobsters? Part II

By Sam Bari

The Newport City Council voted to ban the toxic chemical methoprene from the city's mosquito abatement program at their April 9 meeting.

The issue arose when Newport City Councilman Charles Y. Duncan called for a resolution that bans the use of any of the toxic poisons, such as methoprene, in the mosquito program. Methoprene is thought to be a contributing factor in the decline of the area lobster population.

URI scientific data

Professor David A. Bengtson, who chairs the Department of Fisheries of Animal & Veterinary Science at the University of Rhode Island, said that URI graduate student Mari Butler wrote a thesis published in 2006 on methoprene effects in Rhode Island. The study was done in conjunction with RIDEM and Dr. Al Gettman, the mosquito control coordinator and was funded by the Rhode Island Agricultural Experimental Station.

Bengtson said, "The key experiment that Butler did involved putting 3.5 grams of methoprene pellets into each of two catch basins that drained into Pt. Judith Pond. One week later, when the dissolved methoprene concentrations in the water should have been the highest, Butler added about 1,200 gallons of water to the system that flushed both catch basins to simulate a strong rain event.

"The experiment was intended to introduce the maximum amount of methoprene into the pond's waters in a single event. Butler then sampled the pond waters immediately afterward at the outflow site and at 30 meters away. She then resampled an hour later.

"The results showed that of the 12 samples taken (replicate samples were taken at each time and place), two samples collected at the outflow showed methoprene concentrations of 0.05 and 0.06 parts per billion (ppb). All the rest, including others taken at the outflow, showed no detectable methoprene."

Dr. Bengtson went on to say that to put this information in some context relating to lobster larvae, a published laboratory study in 2005 indicated methoprene to be toxic to stage II lobster larvae at a concentration of one part per billion (ppb).

He also said that methoprene causes molting difficulties to stage IV lobster larvae at 5 ppb. According to Dr. Bengtson, in cases like these, scientists do something called Ecological Risk Assessment. In simple terms, one compares the concentrations that have an effect on organisms, known as the Effect Concentration, in this case, one or five ppb, with the actual concentrations out in the environment, known as the Exposure Concentration. The best guess we have for the worst-case scenario that Butler tested is maximum 0.06 parts per million (ppm), but those minuscule amounts are essentially undetectable, Bengtson said. The conclusion, based on Butler's study is that the amount of methoprene that gets out into the water is not enough to harm lobster larvae.

According to the DEM, the amount of methoprene (3.5 grams) used in the experiment is substantially more than the half teaspoon per treatment put into catch basins. Consequently, the dilution per treatment would be substantially less.

Dr. Bengtson agreed that the experiment had limitations. He said that although there was conclusive evidence that one treatment did not produce a high enough concentration to harm lobster larvae, the experiment did not study the results of prolonged or repeated applications. He also said that the experiment did not study the effects of methoprene on shell disease.

Dr. Bengtson continued to explain that under the Toxic Substance Control Act (TSCA), the Environmental Protection Agency regulates the introduction of new chemicals and puts the burden of proof on the manufacturer to demonstrate that the chemical will not harm the environment or human health. Companies are required to give EPA minimal information on the chemical without disclosing any proprietary information like the actual chemical structure, and EPA scientists have to decide what level of testing will be required on that chemical.

These studies are paid for by the company marketing the product, Bengtson said, and EPA examines the data to determine whether to proceed to the next level of testing or allow the chemical to be produced and sold. EPA works from a cost-benefit perspective, weighing the potential environmental or human health impacts against the potential benefits.

In conclusion, Dr. Bengtson said, "The problem is that there are so many new chemicals being submitted to EPA every year that we, the American people via EPA, cannot fully study every possible thing that could happen over the long term. EPA does the best it can with the limited resources provided by the American people, in this case, the administration and Congress." He also said, "I think I'm safe in saying that DEM does not have the resources to carry out these kinds of studies either. My position, like everyone else's, is that we should proceed with caution. I've tried to point out that EPA does, to the degree that it can by law, public opinion, and resources.

Rhode Island Sea Grant

"There are many things that each of us contributes to the environment. Just look in your cabinet of products that ultimately end up in the rivers, streams and oceans - our antibiotics. The real question here is how do we live on this planet doing the least amount of harm?" said Dr. Kathy Castro of the URI-based Rhode Island Sea Grant program.

"Earth Day is coming up and we have long forgotten why that was even made into a day of its own. It's a good time to go back and read Rachael Carson's Silent Spring, and then all of us sit down together and find other ways and options.

"We have alternatives to pesticides if it is done in a comprehensive fashion. The key is public education. Would each household buy a Mosquito Magnet? Or should our tax dollars go to DEM to put in Altosid tablets? That is a societal decision. Here is a platform we can all stand together on to make a difference instead of blaming someone else. Making someone else wrong does not make us right."

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