Fish-eating resident killer whales also are highly contaminated because salmon are high on the food web. Male orcas carry the chemicals their entire lives, which could explain why they live only half as long as females. The killer whales apparently are getting the chemicals from salmon and seals. Some of the PCBs clearly come from local waters, where industrial and port operations deposited the chemicals in the years before they were banned. But Asia also is probably contributing to the Pacific Northwest's problem.
Airborne contaminants blow from China to North America in about a week.
Salmon also probably pick PCBs up from Asia when they migrate into the North Pacific. Alaska's killer whales also are highly contaminated, even though there are no local dumps or sources, said Craig Matkin, a scientist with the North Gulf Oceanic Society. Individually, the orcas off Washington and Vancouver Island seem robust and healthy. But experts have noticed some disturbing trends. The death rate has climbed in the last five years among the three heavily studied resident pods that frequent the San Juan Islands.