ABSTRACT
A thin layer of a pesticide on a leaf can sublime into the air and then travel long distances until rain or cold weather brings it to earth. Analysis of the blood of the polar bears by techniques such as capillary gas chromatography and mass spectrometry has found highly chlorinated insecticides. Highly brominated flame retardants have also been known to travel long distances, and highly chlorinated insecticides are persistent in the environment. There is nothing that can be done for these particular polar bears. The Stockholm Convention on persistent organic pollutants can prevent further accumulation in distant places. Countries that ratify the treaty agree to outlaw the use of nine persistent organic pollutants. Dichlorodiphenyltrichloroethane (DDT) was exempted since it is still used to fight malaria in some countries. The treaty went into force in 2004. As of 2013, 178 countries have ratified the treaty, although the United States is not one of them. There are similar problems in the tropics. The black-footed albatrosses of Midway Island in the Pacific Ocean are having reproductive problems.2
