More than 40 years after the first initiatives were taken to ban the use of PCBs, the chemical pollutants remain a deadly threat to animals at the top of the food chain. A new study, just published in the journal Science, shows that the current concentrations of PCBs could lead to the disappearance of half of the world’s populations of killer whales from the most heavily contaminated areas within a period of just 30 to 50 years.