Duluth researchers check tree swallow eggs, chicks for 'forever chemical' toxicity

ALONG BOULDER LAKE — Halle Lambeau had to duck just a bit when an adult tree swallow sprung for its next box and flew off, rattled by Lambeau's effort to look inside the box for eggs.

"You now have a mama mobbing you right behind you," said Noah Grode.

Lambeau, a University of Minnesota Duluth graduate student, and Grode, an instructor at the school, were opening human-made tree swallow boxes placed along the shoreline at the Boulder Lake Environmental Learning Center just north of Duluth.

"So far they’ve never actually attacked us," Lambeau said with a grin.

The researchers check the boxes every two days this time of year to follow along as the clutch size grows, to an average of about six eggs per box, and then watch for the chicks to hatch. The eggs are tiny, about the size of a large blueberry.

The boxes here are among 300 built and placed in and around Duluth over the last three springs as scientists geared-up for a study on how PFAS (per- and polyfluoroalkyl substances), commonly known as "forever chemicals," are impacting swallows, especially swallow reproduction. (They look like bluebird boxes, but are square and are always placed near water.)

The effort is headed by Matthew Etterson, a research ecologist at the U.S. Environmental Protection Agency's Great Lakes Toxicology and Ecology Division Laboratory in Duluth.

"The boxes make it really easy for us to capture and study the egg and the hatchlings, the chicks, because we know right where they are and can get at them easily," Etterson said. "We don't have to go looking for nests."

The swallows so far seem to like the boxes — more than half at this site were occupied and, across the study, more than one-third are being used. Other boxes are being placed for chickadees and wrens, too.

A couple eggs from each box are passed on to Mike Thiel and Alex Lowery, also UMD researchers, who use a respirometer to determine the metabolic rate of the growing bird inside the egg "to see how well it's developing," Thiel noted.

Researchers said they can put the eggs back in the nest to hatch with no issues of the mother rejecting them, as long as they don't take all of the eggs out of the nest at once.

Live chicks are studied, too, to see how much PFAS they have accumulated already, either inherited from their parents or from the insects they are being fed almost constantly. They are insect species that are likely to have hatched from sediment or water, where PFAS are likely to accumulate in the environment. And because tree swallows do their hunting close to their nest, within a few hundred yards, usually, it's clear that the source of any contaminants is local.

After 12 days in the egg and another 12 days in the nest, the chicks fledge and fly away, as do the adults, dispersing across the region in their endless hunt for insects before they head back south in August or September, many heading back to the Gulf Coast.

"And then we wrap up this field work until next spring," Etterson said.

Because swallows eat insects likely to hatch where PFAS are likely to show up, namely in water or sediment, they are the canary in the coal mine for PFAS for other species.

Swallows have declined across their range in recent decades, about 30%-50% by some estimates, but are still numerous enough to be widespread across the continent.

In addition to Boulder Lake, you may have seen the tree swallow nesting boxes at other locations around Duluth:

"We are trying to understand how PFAS chemicals impact swallows," Etterson said. "Are they being exposed to them — and we already know they are, at least at some level — and are they exposed to levels high enough to cause issues? Most likely adverse reproductive issues."

One study near 3M's PFAS-producing facilities in the eastern Twin Cities found adverse issues, noticeably lower reproduction among swallows with high PFAS levels. But another study in Michigan near a highly PFAS-polluted military site did not.

Part of the problem is that there are more than 9,000 different PFAS family compounds — none of them found naturally on Earth — and it's not clear which ones, or which combinations, may have the most impact on living organisms.

The study is funded by the U.S Department of Defense as part of the massive, ongoing effort to find and, eventually, clean up PFAS contamination on hundreds of current and former military bases across the U.S. where PFAS-laden firefighting foam was used, including the Duluth air base.

The Environmental Working Group in February released a report with an interactive map that used published research data to show PFAS are far more common than previously believed, not just in a few species near military bases and manufacturing plants but in hundreds of species across the planet, even in remote areas. It's unclear how the PFAS are spreading so far and wide.

The group says PFAS contamination of freshwater fish not only poses risks to fish health, but also creates environmental justice concerns for the communities that rely on those fish for their diets, since they are being exposed to PFAS when they consume the fish. The group compared eating just one PFAS-contaminated freshwater fish per month could be the equivalent of drinking a glass of water with very high levels of PFOS (perfluorooctane sulfonic acid) or other "forever chemicals."

Back in Duluth, the results of the swallow research so far have been as expected. The highest PFAS levels have come in and near the air base in Duluth, with levels from 50-150 parts per trillion and even higher in a couple birds. PFAS have been found at more "background" levels — likely pretty much everywhere — among Boulder Lake swallows, less than 10 parts per trillion. Swallows at Boy Scout Landing have so far been in the middle, running from 10-20 parts per trillion.

Etterson noted these results are preliminary with the study funded to run through 2026.

It's the latest in a seemingly endless global effort to find out where PFAS are and what it's doing to living creatures great and small. The U.S. government now says the stuff, in varying amounts, is inside all of our bodies, most of our drinking water supplies and even the fish we catch and eat. PFAS have been found in polar bears in the arctic, dolphins at sea, smelt in Lake Superior and yes, in swallows captured and studied in the Duluth area.

The effects of PFAS exposure on humans remain a matter of debate, specifically around the causal links between exposure and poorer human health. But experts say there are associations that even low levels of PFAS can lead to low fetal weight, impaired immune response, thyroid function abnormalities, obesity, increased lipid levels and liver function, and impaired vaccine response.

It may have some of the same effects on birds and animals.

"How much is too much for swallows? We really don't know yet," Etterson said of PFAS exposure.

"If we find high PFAS and reproductive problems at the air base and surroundings, we will also do due diligence to try to rule out any other potential causative agents, notably legacy contaminants that may also cause reproductive problems for birds, such as PCBs, dioxins and organochlorines," he said.

If researchers can rule out those additional potential causes, they will conduct a dosing study that will intentionally expose swallows to various levels of PFAS and see what happens.

"If we don't see any problems in the dosing study, that will suggest that any problems that are occurring may be caused by something other than PFAS exposure," Etterson said. "If we do observe problems in the dosed birds at similar concentrations to the field exposures, then that will be fairly strong corroborating evidence that the PFAS are a problem."

To see how widespread the PFAS problem might be among other living creatures, the study also is looking at chickadees and house wrens.

"We believe that avian exposure to PFAS occurs primarily through diet, though there is some evidence in the scientific literature that drinking water may also be a route of exposure," Etterson added.

It's hoped the birds and DNA analysis of their poop will help create "mathematical models of the movement of PFAS from water, soil and sediment into the insects, and ultimately into the birds."

PFAS are a large group of human-made chemicals that have been used in industry and consumer products worldwide since the 1940s. They are a class of nonstick, waterproof and stain-resistant compounds used in consumer products and industrial applications. Best known are PFOA (perfluorooctanoic acid), formerly used to make DuPont's Teflon, and PFOS, formerly in 3M's Scotchgard, but also used widely in aircraft firefighting foam and other industrial uses.

PFAS contamination may be in drinking water, food, indoor dust, some consumer products and workplaces. Most non-worker exposures occur through drinking contaminated water or eating food that contains PFAS.Although some types of PFAS are no longer used, some products may still contain PFAS:

PFAS are present at low levels in some food products and in the environment (air, water, soil etc.), so you probably can't prevent PFAS exposure altogether. However, if you live near known sources of PFAS contamination, you can take steps to reduce your risk of exposure:

Some scientific studies suggest that certain PFAS may affect different systems in the body. According to the Centers for Disease Control and Prevention, research involving humans suggests that high levels of certain PFAS may lead to the following:

The Wisconsin Department of Natural Resources found elevated levels of PFAS in smelt captured along the South Shore of Lake Superior and in 2021 issued an advisory for people to limit meals of smelt to one per month due to PFAS toxicity. The Minnesota Department of Health adopted the same advisory.

PFAS advisories have also been issued for trout in Miller Creek in Duluth and crappie, sunfish, walleye and pike in Wild Rice Lake Reservoir just north of Duluth.

In October 2018, the Michigan Department of Health and Human Services issued a "do not eat" advisory for deer taken within 5 miles of Wurtsmith Air Force Base, a site in eastern lower Michigan with soil and groundwater contaminated with PFAS.

The Wisconsin DNR and Department of Health Services issued a "do not eat" advisory for deer livers from any deer harvested within 5 miles of the JCI/Tyco Fire Technology Center in Marinette. Deer sampled in that area had high PFAS levels in their livers.

In Minnesota, the Minnesota DNR submitted deer shot by hunters to be tested for PFAS. The agency found PFAS in all the deer sampled, but not yet at levels high enough to issue a human health advisory.

This story was updated at 2 p.m. Saturday, June 3, 2023, to correct the spelling of Alex Lowery's name and update the number of compounds now considered part of the PFAS family of chemicals. It was originally published at 6 a.m. June 3, 2023.

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Duluth researchers check tree swallow eggs, chicks for 'forever chemical' toxicity