Orcas and Other Marine Animals Continue to be Harmed by Pollutants

Persistent organic pollutants, or POPs, are dangerous chemicals that resist degradation and therefore stay in the environment for a very long time. Recent research published in Science has shown that even though POPs have been banned in most countries, they’re continuing to harm marine life.

Scientists Paul Jepson and Robin Law analyzed data to determine just how harmful POPs are. They found that the chemicals are especially dangerous to larger marine animals, including sharks and whales. POPs make their way through the food chain and end up concentrated in the larger predators. A fish might consume a small amount of a POP, such as DDT, but not enough to seriously harm them. Then, a larger fish might come along and eat several smaller fish, allowing the POPs to build up. If an orca or shark then eats the larger, contaminated fish, they end up with dangerous levels of POPs in their body. This not only causes health problems and lower lifespans but the authors found evidence that it can lower fertility. Jepson and Law point to the recent population decline in orcas, speculating that POPs may be to blame. Past research has shown that orcas are the animals with the highest concentration of POPs in their bodies.

Examples of persistent organic pollutants are polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT). Both chemicals, as well as other known POPs, are harmful to humans and illegal to use in most countries. The problem is that they’re very difficult to remove from the environment and so have continued to harm wildlife. POPs also make their way into the food supply; they are sometimes present in seafood and represent a serious human hazard.

The authors recommend that future studies be conducted to determine just how harmful these chemicals are to marine animals. The main sources of POP contamination need to be identified, as well as possible solutions for removing them from the environment.


P.D. Jepson et al. Persistent pollutants, persistent threats, Science (2016).

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