(Beyond Pesticides, June 12, 2008) A new study reports that pesticides, including DDT and tributyltin (TBT), have been found in deep-sea squids and octopods. This study is the first to analyze the chemical contamination of these deep sea organisms, and adds to the body of literature that demonstrates the far-reaching effects of pesticide use on global ecosystems. Pesticide contamination has been documented as far away from the point of use as the arctic and now the deep sea.
In the study, to be published in the journal Marine Pollution Bulletin, Michael Vecchione of the National Oceanic and Atmospheric Administration (NOAA), and colleagues from the Virginia Institute of Marine Science of The College of William and Mary report finding a wide variety of chemical contaminants in nine species of cephalopods, a class of organisms that includes cuttlefishes and nautiluses along with squids and octopods. Cephalopods are important to the diet of cetaceans, which are marine mammals such as whales, dolphins and porpoises. Persistent organic pollutants (POPs) in the blubber of whales and some deep sea fish has already been documented.
The twenty-two specimens analyzed were taken from depths between 1000 and 2000 meters (approximately 3,300 and 6,600 ft.) in the North Atlantic Ocean. “The cephalopod species we analyzed span a wide range of sizes and represent an important component of the oceanic food web,” Vecchione said. “The fact that we detected a variety of pollutants in specimens collected from more than 3,000 feet deep is evidence that human-produced chemicals are reaching remote areas of the open ocean, accumulating in prey species, and therefore available to higher levels of marine life. Contamination of the deep-sea food web is happening, and it is a real concern.”
Pesticides discovered in the tissue of these organisms include tributyltin (TBT) and dichlorodiphenyl-trichloroethane (DDT), along with polycyclic aromatic hydrocarbons (PAHs), which have many sources, one of which is creosote used for wood preservation. The scientists also discovered high levels of other industrial pollutants including polychlorinated biphenyls (PCBs) and brominated diphenyl ethers (BDEs).
TBT was once used on nearly all of the world’s 30,000 commercial ships as an algae and barnacle killer, but is now subject to an international ban because of its severe effects on marine wildlife and its persistence in the aquatic environment. However, TBT containing compounds are still registered for use by the U.S. Environmental Protection Agency (EPA) as bacteriocides, microbiocides, fungicides, algaecides, slimicides, and virucides and can be used in livestock operations and hatcheries, materials preservation, and non pressure-treated wood operations. The EPA recently had a comment period for the reregistration of TBT-containing compounds.
The results of this study highlight how critical it is to take regulatory action on chemicals that are persistent in the environment and reach all ends of the food web, including humans who eat contaminated seafood. The ban on TBT used on ships will not signal an end to the presence of TBT in aquatic ecosystems for many years to come, just as the U.S. ban on DDT in 1972 did not put an end to DDT contamination within the U.S. (DDT is still in use in some countries for mosquito control, despite its toxicity and the availability of less toxic alternatives). Other chemicals that have similar persistence and chemical characteristics to DDT, such as lindane are still registered for some uses in the United States.
While the use of many persistent chemicals is on the decline because of mounting evidence of their lingering negative effects, the use of some persistent pesticides in different chemical families is increasing. Despite the public health and environmental threats they pose, these chemicals have largely avoided public scrutiny. One such chemical that Beyond Pesticides finds particularly disconcerting is the ubiquitous triclosan. This antimicrobial pesticide has been linked to numerous adverse health effects in humans and aquatic life, and triclosan levels in waste water have been steadily increasing. For more information on triclosan, please see the Beyond Pesticides antibacterials page. EPA’s comment period for the reregistration of triclosan is open and you may submit public comments here.