Chemicals produced by humans have been found in deep-sea squid and other creatures, further evidence that contaminants make their way deep into the marine food web, scientists said Monday.

Researchers found a variety of chemical contaminants in nine species of cephalopods, which include octopods, squids, cuttlefishes and nautiluses. These species are food for dolphins, narwhals, killer whales and other toothed whales. The researchers collected nine species of cephalopods up to a mile down and deeper in the western North Atlantic Ocean by trawling.

"It was surprising to find measurable and sometimes high amounts of toxic pollutants in such a deep and remote environment," said Michael Vecchione, a researcher with the National Oceanic and Atmospheric Administration (NOAA).

Among the chemicals detected, all of which don't degrade and therefore persist for a very long time:

  • Tributyltin (TBT), an additive used to control growth of organisms and is found in antifouling paints for boats, wood preservatives.
  • Dichlorodiphenyl-trichloroethane (DDT), a pesticide banned in the U.S. in the 1970s but still used on a limited basis in some parts of the world to control diseases like malaria.
  • Polychlorinated biphenyls (PCBs), used to insulate electrical transformers and capacitors and in coatings, sealants, adhesives, paints, wood floor finishes, and in carbonless copy paper. PCB production was banned in the U.S. in the 1970s.
  • Brominated diphenyl ethers (BDEs), used as flame retardants in a variety of household products, from plastics to foam in furniture and fabrics.

The findings will be published in the journal Marine Pollution Bulletin.

Recent studies have reported the accumulation of such chemicals in the blubber and tissues of whales and other predatory marine mammals as well as in some deep-sea fish. Other investigators had speculated that the pollutants in marine mammals had resulted from feeding on contaminated squids. However, almost no information existed prior to this study about POPs in deep-sea cephalopods.

Vecchione and colleagues wanted to see if whales had a unique capacity to accumulate pollutants or if they were simply one of the top predators in a contaminated deep-sea food web.

"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."