Long-Banned Toxin Harm Killer Whales

PCBs form thick liquids that are used as hydraulic fluids, lubricating oils, paint and concrete stabilizers, and nonflammable insulation in electrical transformers. These liquids were also used to make carbonless copy paper. Millions on tons of PCBs were produced prior to their link to cancer and immune system, reproductive, and endocrine related health problems in both people and animals. The U.S. banned production of PCBs in 1978 and their worldwide ban was effective in 2004.

Although PCB concentrations in the environment dropped, these pollutants do not break down easily. These pollutants are still leaking into the environment from sources such as landfills, river-bottom sediments, and their dumping grounds. PCBs are consumed by microbes, which transfer the pollutant to the food chain. These pollutants build up in fat and blubber of animals such as killer whales that prey on animals such as seals or fish, which also carry PCBs. Several surveys have reported reduce in population of killer whales and some have revealed high levels of PCBs in these animals. In a study published in the journal Science on September 27, 2018, the researchers from Michigan State University analyzed the scientific literature for all studies related to killer whale PCB levels and killer whale population changes.

The researchers choose to estimate the toll of the PCBs as testing animals directly for health consequences was not possible as killer whales are a protected species. The built on lab studies showed that PCBs extracted from whale blubber affect killer whale immune function. In mice studies, it was revealed that PCB levels raise susceptibility to disease and impair fertility. Based on the lab results and the year-on-year PCB concentrations data in individual killer whales, the team predicted the probable casualties due to PCBs in the near future. The models suggested that of the 19 populations studied, over half will decline due to effects of PCBs. The most susceptible population includes those in Brazil, the North Sea off the U.K., and around the Straits of Gibraltar.

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