It may have taken decades, but regulations have finally led to a decrease in the quantity of dangerous chemicals in Arctic fish and wildlife.
“A lot of these bad chemicals are going down in the Arctic biota,” says John Kucklick, a research biologist at the National Institute of Standards and Technology and one of the coauthors of a study published recently in the Science of the Total Environment.
But while concentrations of many older, phased-out chemicals are dropping, they still persist in some parts of the Arctic where they could be affecting marine mammals, seabirds, fish and even the northern people that subsist on these animals. Meanwhile, the study shows that newer chemical threats are starting to turn up in northern ecosystems.
The research is part of long-term monitoring in Canada, the U.S., Greenland, the Faroe Islands, Sweden, Norway, and Iceland which tracks the levels of chemicals restricted or banned by the Stockholm Convention on Persistent Organic Pollutants, an international treaty focused on eliminating or restricting the use and production of persistent organic pollutants (POPs) such as the DDT used in pesticides, polychlorinated biphenyls (PCBs) used widely as a flame retardant and the dioxins emitted when incinerators burn hazardous waste. Nearly the entire world has agreed to the treaty, other than a handful of countries including the U.S., Israel, Haiti and Brunei, though the U.S. has phased out a number of the chemicals covered by the treaty on its own. The treaty originally covered 12 chemicals but has added 16 more since 2001.
Many of the chemicals originate from temperate or tropical zones, but they are particularly hardy—one of the reason they’re called persistent organic pollutants—traveling thousands of miles north by sea currents or through the air. Once in the Arctic, they stay there, getting absorbed into plant roots or being eaten by plankton or other small creatures. Those smaller quantities aren’t digested but instead accumulate in the larger fish, marine mammals or seabirds that eat them. While the long-term effects of many of these pollutants are unknown, scientists suspect that they can affect the physiology, reproductive systems and hormones of organisms.
“The fact that it’s up there in the first place is disconcerting. It tells you how easily these things can move around the globe,” Kucklick says of the chemicals in the Arctic.
The Arctic Monitoring and Assessment Program, has been running since 1991 and is an amalgamation of many country-specific monitoring programs from Arctic countries, though researchers have also examined archived samples going back to the 1980s. This study itself is the latest of close to a dozen conducted so far at various points over the past 20 years on the ever-growing resource of thousands of animal tissue samples stored in the archival banks of the countries involved. Many of these samples come from trapping fish specifically for the purpose of monitoring, while others come from marine mammals hunted from northern peoples, or from tranquilized polar bears. Most of the 28 listed chemicals were tracked in the recent study, with the only some exceptions due to lack of a long-term record.
Melissa McKinney, an assistant professor of natural resources sciences at McGill University in Canada who was not involved in the recent study, says that the paper is important for establishing up-to-date Arctic-wide trends.
“It is a good news story that declines have occurred for some older chemicals, and even some newer chemicals, due to voluntary phase-outs and national and international regulations,” she says.
But this doesn’t mean that Arctic species are out of the woods yet. “On the other hand, current levels are still of concern in Arctic species like polar bears, despite these earlier declines, and there is an increasing number of newer chemicals, some which are replacements for the older ones,” she says, adding that the new chemicals that have replaced the phased-out flame retardants and newer polyfluoroalkyl substances used in paints, packaging material and textiles are now turning up in polar bear tissue, for example.
McKinney says that modeling work has suggested that tissue concentrations of POPs bring a risk to the immunity and reproductive systems in polar bears as well as potentially causing cancer.
According to Robert Letcher, a research senior scientist at Environment and Climate Change Canada, the country's environmental agency, the problem is exacerbated in pollution hot spots such as around the Norwegian island of Svalbard or off the coast of parts of Greenland. He says that we just don’t know how these pollutants might affect wildlife, because research has so far been limited.
Polar bears are the one exception, since they have been studied more extensively. Letcher says some research has found that DDT and PCBs was found in Svalbard polar bears’ thyroid hormones in levels high enough in some cases that they affect the bears’ memory and motor functions. Another study found POPs could negatively impact female sexual hormones in polar bears.
Letcher says that the good news is that polar bears’ bodies can break down some of these chemicals. Not so with toothed whales like orcas, he says.
“Killer whales, even worse than polar bears, have PCB levels that are right through the roof,” he says. The whales' situation could get even worse, since many orcas are now relying on larger prey like sea lions or seals due to a collapse in fish stocks.
“If you feed higher in the food chain, then you have a lot more contaminants,” he says.
Mark Mallory, Canada research chair and associate biology professor at Acadia University in Nova Scotia, has studied how birds can ingest some of these chemicals through the marine food they consume, and subsequently dump these chemicals back onto land through their feces.
He says that in terms of the research, “declining concentrations of anthropogenic chemicals is generally good news for birds, period.”
Some evidence shows that POPs can affect the incubation periods of birds as well as their immune systems in Svalbard, he says. But different species are affected quite differently.
“The breeding strategy of different species dictates whether they bring a lot of reserves with them or gather most of those when they get to the Arctic,” he says, adding that some research in 2014 showed that dovekies wintering off the coast of Newfoundland in Canada absorb more mercury—an element that wasn’t tracked in the recent monitoring research but can also cause problems for Arctic wildlife— than they do when breeding off the coast of the island of Svalbard in Norway. Other researchers were actually able to trace the wintering areas of skuas by the specific chemical mixtures inside them. “So it pretty much goes on a case-by-case basis.”
He says that as well as ingesting chemicals in the Arctic, seabirds can also be conduits for transporting these chemicals from southern regions during their migrations.
Mallory cautions that the science on possible effects of some of the newer chemicals is less clear, but adds that the more researchers look into them, the more problems they find.
And humans aren’t immune to these chemicals either. Kucklick says that many northern communities rely on animals like polar bears and marine mammals as a major source of sustenance, which puts them at the top of the food chain and the largest consumers of accumulated POPs.
“There is a lot of concern in native communities about what’s in their food,” he says.
One chemical, PFOS, which used to be used in stain- and water-repellent sprays like Scotchgard and which was phased out in many places in the early 2000s, continues to be found in Arctic tissue samples, and levels aren't decreasing. Meanwhile, a flame retardant which was added to the Stockholm Convention in 2017 increased by 7.6 percent every year since monitoring began nearly three decades ago. Letcher says that it’s difficult sometimes to keep up with the new chemicals being found, and since it takes time before they appear in Arctic ecosystems, long-term monitoring such as the research recently published is critical.
Meanwhile, Mallory says the Arctic continues to be a sink for contaminants released in the temperate and tropical regions, and he expects more news about subtle negative effects of chemical ingestion.
“It’s just one more stressor on wildlife already living in a stressed ecosystem,” Mallory says.