Volunteers across all of Minnesota’s 87 counties have been busy carefully plucking pine needles from coniferous trees in their neighborhoods and collecting them in plastic bags. Why? They’re gathering clues about how PFAS move through the air so the Minnesota Pollution Control Agency (MPCA) can better understand how to protect Minnesotans from PFAS pollution.
PFAS, which stands for per- and polyfluoroalkyl substances, are a group of thousands of human-made chemicals that do not break down over time. PFAS are extremely difficult to destroy, and because they do not break down easily, they can accumulate in the environment and in people, causing negative health impacts like cancer, liver disease, immune system disruption, and other health problems.
While agency scientists have widely studied the presence of PFAS in solid waste, soil, water, consumer products, and even fish, one significant gap remains in the research: how many PFAS are in the air around us.
PFAS can enter the air in several ways, including waste incineration, landfill leachate evaporation, emissions from producing products with PFAS, and using and disposing of those products. Summer Streets, a research scientist in the MPCA’s water quality unit, suggested collecting pine needles as a cost-effective and accessible way to gather data on PFAS in the air.
“Overall, we’re trying to understand PFAS in ambient—not from a direct source— air deposition, which will help us better understand PFAS movement through our environment and increase our understanding of exposure routes,” Streets said.
Air monitoring equipment can detect PFAS in the air, but it has limitations. It requires a fenced-in area with electricity, trained staff to operate the monitoring equipment, and expensive analysis only available at a few laboratories. Pine needles, on the other hand, become a natural and much less expensive way to gather data.
Pine needles are excellent PFAS “air samplers” because their waxy coating holds onto PFAS from the air. In fact, they have been used to effectively assess a variety of organic contaminants in the air in the past, including PFAS.
This will be the first time the MPCA will get statewide data on PFAS air deposition. Volunteers have been hard at work collecting pine needles across the state since August, wrapping up their collection this fall. Now their needles will be sent to the lab for analysis. For this project, MPCA scientists will look for 75 of the thousands of different PFAS that exist.
A team of volunteers
While this project is funded by the Environmental and Natural Resources Trust Fund, it also relies on help from 187 volunteers across the state, 87% of whom already volunteer with the MPCA as volunteer water monitors.
“Collecting samples from every county in Minnesota is a huge task,” said Waverly Reibel, the volunteer water monitoring program coordinator for the MPCA. “We wouldn’t be able to do this without our amazing network of volunteers.”
One volunteer, Lindsey Albright, who works for the Dakota County Soil and Water Conservation District, volunteered because she saw an opportunity to do her part and help her community.
“I like that I can collect a little bit of data and help be a part of a larger project,” Albright said.
Albright feels that PFAS has become a growing concern for other Minnesotans and knows that PFAS isn’t some far-off threat.
“It’s right here within our neighborhoods,” Albright said. “We’re [collecting] at the neighborhood park that my kids come and play at.”
The actual collection process is simple. Volunteers pull needles from any coniferous tree in their county. The tree doesn’t have to be pine; species of fir, hemlock, tamarack, or cedar all have needles that are useful in detecting PFAS.
“Anything with needles and cones will do,” Streets said.
Because PFAS are so common, volunteers take precautions like donning PFAS-free gloves, wearing old clothing that hasn’t been treated to be water or stainproof, and avoiding bug sprays or sunscreens that contain PFAS to prevent contamination.
Volunteers include other data like their county name, GPS coordinates, sample date, description of the area where the needles were collected, and weather conditions at the time of sampling. Collectively, the volunteers will gather more than 200 samples.
MPCA scientists will send the samples off to the lab to analyze the needles collected at the tips of branches where the newest growth takes place. This way, the scientists can get a snapshot in time of what PFAS deposition has happened in the last year or so.
The benefits of pine needles
Compared to other air monitoring equipment, pine needle collection is relatively inexpensive and can be done by the MPCA’s volunteer network. Conifer needles also have the advantage of being found throughout Minnesota, which means the MPCA can gather information about PFAS in many different places, even in very remote areas. Overall, the new data will help the MPCA gather clues about the presence of PFAS in Minnesota and map out where those hot spots exist.
“It can help us identify areas where PFAS might be higher for some reason,” Streets said. “For example, if there is a nearby source area, that can give us clues and then we can use [that] to do more investigation or perhaps remediation.”
Next steps
Though volunteers are just starting to send off their samples, the project will continue through 2028, and it may be a while before all the data is processed. Streets estimated that data will be available to the public by 2027.
This type of work doesn’t always move quickly. Careful analysis and quality control measures are essential to get the most accurate information.
Another element of the project includes a historical analysis of pine needle samples taken from the University of Minnesota Bell Museum’s herbarium—a collection of dried and labeled plant specimens often used for research.
Streets plans on selecting up to 35 archived pine needle samples collected from Washington, Ramsey, and Dakota counties. Some of the samples date back to the late 1800s and early 1900s, prior to the invention of PFAS. The project will examine needles from the 1940s—when PFAS was first produced by manufacturers—up until 2020. This analysis will provide data about when PFAS first showed up in our environment and may also show shifts in which PFAS were produced over the years.
Results from this study will support the PFAS Monitoring Plan and provide a snapshot in time of how PFAS show up in our ambient air. Having this data will provide MPCA with a better understanding of PFAS presence and movement in Minnesota, helping the state find new ways to address PFAS.