[ad_1]
In 1979, more and more scientific evidence led to an indisputable conclusion: polychlorinated biphenyls (PCBs) were toxic. These chemicals have been used for years in a wide variety of industrial applications, including insulators, electrical appliances and sealants for the road. But studies have shown that PCBs are also endocrine disruptors, thus altering the function of chemical signaling systems in the body. The US Environmental Protection Agency has banned the future production of these products. The rest of the world followed the Stockholm Convention in 2001.
At that time, however, the world had already produced about 1.5 billion pounds.
Although countries collectively agreed to introduce laws requiring the proper disposal of PCBs in landfills, much of these laws were found in the environment. Previous studies have shown the harmful effects of the chemical on seals, seabirds, porpoises and even humans. Yesterday (27 September), researchers led by a team from the University of Aarhus in Denmark and the University of St. Andrews published a study showing that PCBs in the ocean (paywall) also represent a serious predator for the ocean.
Orcas, also known as orcas, are not difficult to eat and if any of their prey contains trace amounts of PCBs, the chemical can accumulate in the fat of orcas after their meal. Because PCBs are fat soluble, mothers can also transmit the pollutant to their young through their milk. It affects the hormonal, reproductive and immune systems of orcas, which means that their remaining amount makes them sick or infertile.
Over the course of a decade, the team of researchers sampled fat from 351 orcas belonging to 19 different groups living around the world. They found that killer whales had between 10 and 50 milligrams of PCBs per kilogram of fat, equivalent to about 100 to 1,300 parts per million, according to the Atlantic. Although there has never been any studies on the effects of PCBs on killer whales in particular, studies have shown that seals become sterile when PCB levels in their fat reach around 60 parts per million.
By modeling current population rates, estimated diets and the amount of PCBs passed from mother to calf (which accounts for about 70% of a mother's PCB levels), the team projected how different Orc populations are likely to occur in the next few years. century. They found that 10 of the 19 pods studied would probably decrease. Some pods live off the coasts of Europe, Japan and the western United States, where the number of orcas is already dangerously low and where the waters have historically high concentrations of PCBs , could disappear completely.
Killer whales living in areas with low PCB concentrations, such as the Arctic oceans, are less likely to decline imminently, at least because of this type of pollution. However, other types of human activity also have an impact on killer whales. Dave Duffus, a marine biologist at the University of Victoria in Canada, told the New York Times (paywall) that he has already seen killer whale populations deteriorate due to declining food reserves and excessive noise from transport activities.
All hopes are not lost: for the moment, not all countries have disposed of equipment containing PCBs, Aarhus University postdoctoral researcher Jean-Pierre Desforges told the Times. If they do it by 2028, as they promised with the Stockholm Convention, the decline of the population might not be as fast in some pods.
Source link
