A team of British scientists led by the Institute of Zoology of the Zoological Society of London has found that almost half (48%) of marine mammals in seas around the UK are poisoned by substances called persistent organic pollutants (POPs). The study was published in the scientific journal magazine Environmental Science and Technology (EST).
POPs include a variety of toxic compounds previously used in pesticides, fire retardants and refrigerants. The use of many of these substances was banned 20 years ago, but they continue to occur in nature due to their resistance to degradation in natural conditions.
The team obtained toxicology samples spanning a 30-year period. This allowed biologists to find out what effects the pollutants still had on marine mammals.
While researchers have found levels of six key POPs are falling, experts are concerned that chemicals are increasingly leaching from coastal landfills as climate change increases flooding, extreme weather events and coastal erosion.
“These toxins are initially absorbed by plankton at the bottom of the food chain. These are chemicals that cannot be broken down or eliminated from the body, and their concentrations increase as they move up the food chain in a process known as biomagnification,” explained Dr Rosie Williams, lead author of the study.
Although the effects of these chemicals vary, they are consistently harmful. By accumulating in body fat, they can harm the reproductive system, immune system and hormonal cycles.
Scientists found that killer whales off the north coast of Scotland were most exposed to POPs in British waters. No calves have been born in the herd in the last 20 years, which may be the result of heavy polychlorinated biphenyl (PBC) pollution. These substances were previously used as refrigerants and electrical insulators. PBC suppresses the immune system and suppresses reproductive functions.
Additionally, more than half of bottlenose dolphins in British waters had critical levels of the pesticide DDT, which also damages the immune system. Sperm whales, as well as bottlenose dolphins, were also seriously affected by this substance.
Biologists hope that levels of POPs in the environment will continue to decline in the coming years due to better control of pollution sources.
Biologists before to create Concentrations of toxic chemicals in the bodies of rare Australian dolphins have been recorded.