Levels of some of the most dangerous Pfas compounds have dramatically fallen in Canadian seabird eggs, which the authors of a new peer-reviewed study say illustrates how regulations are effective.

Researchers looked at Pfas levels in the eggs of northern gannets in the St Lawrence Seaway basin over a 55-year period. Pfas levels shot up from the 1960s through the peak of the chemicals’ use in the late 1990s and early aughts, then fell.

The fall coincides with several developments – facing regulatory scrutiny, the chemical giant 3M, which is one of the largest producers of Pfas, began moving away from Pfos, among its most common and toxic compounds. By 2015, major chemical makers reached an agreement with the US Environment Protection Agency to phase out Pfos and Pfoa, the latter a similarly problematic compound.

Raphael Lavoie, a co-author and ecotoxicologist with Environment and Climate Change Canada, called the findings “good news”.

“We see this incredible rise to a peak where concentrations seem to be higher than toxicological threshold for those birds, then it really decreases in a nice way,” Lavoie said. “The regulations are having a good effect.”

Pfas are a class of at least 16,000 chemicals commonly used to make products resist water, stains and heat. They are called “forever chemicals” because they do not naturally break down, and they are linked to a range of health issues such as cancer, thyroid disease, kidney problems and decreased immunity.

The eggs were collected from the remote Bonaventure Island, which holds North America’s largest northern gannet colony. Data shows the levels of Pfos fell from a peak level in the eggs of 100 parts per billion (ppb) to a level of 26ppb by 2024, a 74% drop. Levels of Pfoa are down about 40% over this time, though they ticked back up in recent years.

Meanwhile, PFHxS, another common, toxic Pfas compound fell from 0.69 to 0.19ppb, or about 72%.

The paper details how Pfas production increased sharply between 1969 and the mid-1990s, driven by widespread applications from firefighting foams to stain guards, as well as various manufacturing processes. With virtually no regulatory oversight, the chemicals rapidly accumulated in the environment, exposing wildlife like the northern gannet. The birds faced high risk as the St Lawrence received water pollution from the upper midwest manufacturing centers around the Great Lakes. The chemicals reached levels in the eggs that suggested ecotoxicological risks, Lavoie said.

As the dangers of the most commonly used Pfas came into focus around this time, the US, Europe and Canada each ratcheted up regulatory pressure with proposed regulations or risk actions. The United Nations similarly targeted Pfos, and the compound was also listed in the 2009 Stockholm convention, which requires signatory countries to restrict its production and use. In recent decades, militaries and other users of firefighting foam switched to Pfas-free products, or stopped using the chemicals during training exercises, which has significantly reduced water pollution.

However, it is not all good news. The chemical makers moved to a newer generation of smaller Pfas, and those also present risks to the environment and wildlife. The levels of those compounds have probably grown, and the study found one example of a shift, but the new Pfas are more difficult to measure in bird eggs because they do not accumulate in wildlife as much, Lavoie said.

Moreover, compounds such as Pfos stay in the environment or animals’ bodies for decades, so the birds and environment will remain contaminated for the foreseeable future, which the authors wrote “emphasizes the importance of maintaining scientific and regulatory vigilance”.