Organochlorines (OCs) concentrate through the arctic marine food webs and are stored in the adipose tissue due to their high lipophilic and persistent characteristics. The polar bears receive high doses of POPS through their diet and a controlled experimt was need to resolve effect on the immune system and effects on internal organs. Such a controlled experiment on sledge dogs as a replacement test organism for the polar bear was conducted from 2004-2006 to investigate dose-response effects.