GEF

Unit 3  |  Primary Sustainability Issues 79 Pesticide usage may have unknown consequences. Polychlorinated biphenyls (PCBs) are considered an espe- cially harmful set of chemicals. PCBs were extensively used in the manufacture of coolants, insulating fluids, and for other industrial purposes. They were banned by the U.S. in 1979 and globally by the Stockholm Convention of 2011. However, for decades, PCBs were produced in large quantities and released into the environment with little restriction. One extreme case involves an area in Japan whose population was suddenly struck in 1968 with frightening illnesses, ranging from discol- ored and blistering skin to intense intestinal tract problems. It was soon discovered that the source of these severe health problems was PCB-contaminated rice oil. Even with this clear evidence, it took Japan four more years to ban the chemical. A significant challenge presented by PCBs and other chemi- cal pollutants is their tendency to become distributed far from their point of production and concentrated within the bodies of humans or animals. High concentrations of PCBs have even been detected in polar bears far north of the Arctic Circle. The magnification of toxic substances within the bodies of animals is called biomagnification and occurs as these chemicals move up the food chain when larger animals feed on smaller animals. POLYCHLORINATED BIPHENYLS (PCBS) A class of highly toxic chemicals that were used in electrical components and have been found even in remote ecosystems. BIOMAGNIFICATION Increase in concentration of a chemical as it moves through a food chain.