Diet determines orcas’ pollution exposure

In 2001, more than 90 nations signed a treaty to reduce or possibly eliminate the production and use of the so-called dirty dozen highly toxic chemicals that accumulate in the environment. These include pesticides such as DDT and chlordane and industrial compounds such as polychlorinated biphenyls (PCB). All these chemicals take decades to break down, get passed along the food chain, and are hazardous to humans and animals. Over the years, at least a dozen more persistent organic pollutants have been added to the treaty’s list . Orcas, also known as killer whales, are among the most affected marine animals . A recent study led by McGill University researchers found that the North Atlantic Ocean orcas they studied that mostly ate fish were less contaminated than orcas that preyed on marine mammals such as seals and dolphins ( Environ. Sci. Technol. 2023, DOI: 10.1021/acs.est.3c05516 ). In the Canadian Arctic Ocean,