Polar bears are not endangered, though if hunting was not regulated they would be, due to their slow rates of population growth. They do face threats however, that must be constantly monitored (4). The Polar Bear Specialist Group reported in their 2005 meeting that the greatest challenge to the conservation of polar bears may be large-scale ecological change resulting from climatic warming, if the trend documented in recent years continues (5). Other threats to this species include pollution, poaching, and disturbances from industrial activities (4) (5). While the effects of climate change are not certain, it is recognised that even minor climate changes can have profound effects on polar bears and their sea-ice habitat (4). For example, if climate change results in increased snow in the Arctic, polar bears may be less able to hunt prey by entering seal birth lairs, which will affect the survival of both polar bear adults and cubs. On the other hand, if there is reduced snow and increased seasonal rain, seal productivity may be reduced as the lairs may not be thick enough to protect the pups as they develop, or lairs may collapse and kill the seals. In turn this would reduce prey for the polar bears. Unusual warm weather could also impact the polar bear's denning activity (6). Persistent Organic Pollutants (POP) also pose a threat to polar bears. Studies on the accumulation of organochlorines (caused by pollutants) through food chains have shown that polar bears, as top predators, are at risk of accumulating elevated levels of these compounds. These levels are associated with a range of effects, including neurological, reproductive and immunological changes, which may, for example, reduce ability to fight diseases and reproduce (6). In the 1960s and 1970s, extensive hunting of polar bears had pushed them to the brink of extinction. This threat had a considerable impact on polar bear populations, and, though hunting is now controlled, populations are still recovering (4).