For several years, chemical use in the Arctic has been a major concern. Harmful chemicals are causing serious health concerns in animals and marine life in the area. Fortunately, the Stockholm Convention of 2001 put significant bans on certain chemicals that were previously being used in the Arctic. And a new study shows that the bans are working.

The study, published in Science of the Total Environment, looked at data regarding the persistent organic pollutants (POPs) present in the Arctic. Researchers looked at contamination levels by examining samples of fat taken from shellfish and seabirds all the way back to the 1980s. Additionally, they looked at the air in the Arctic Circle in order to test for traces of pollution.

Dr. John Kucklick, a biologist from the National Institute of Standards and Technology, explained, “This paper shows that following the treaty and earlier phase-outs have largely resulted in a decline of these contaminants in the Arctic. When POP use was curtailed, the change was reflected by declining concentrations in the environment.”

So while POPs are generally slow to be removed from ecosystems, the data shows that the ones banned by the Stockholm Convention have steadily been decreased over the years. And it’s not just in the Arctic either. The 2001 treaty was signed by 152 countries with the intention to restrict and eliminate the use and production of 12 POPs. And over the years, more harmful chemicals have been added to the list, totally to 33 POPs that are banned in the agreeing countries.

The POPs that were banned were found to cause health problems not only for marine life, but people as well — especially with Americans eating an average of 14.9 pounds of seafood in 2016 alone. POPs have been linked to reproductive, neurological, immunological, and developmental problems. Because of the problems they can cause, there was a drastic population decline of animals affected by these chemicals.

While POPs are a problem in all areas of the world, they’re particularly harmful in the Arctic ecosystem. The ecosystem is especially fragile, mainly because the area can become polluted not only by local sources, but through air and water currents as well. And with the U.S. being the largest producer of chemical products around the world, there are plenty of chemicals that are able to enter ecosystems.

But the POP ban seems to be working on certain levels. Unfortunately, the work on banning chemicals isn’t over yet. While the research showed declining traces of several chemicals, there were also some increases as well. So scientists hope that people will continue working towards reducing and eliminating the use of harmful chemicals so ecosystems can be as healthy as possible.