March 19, 2024

Tracking Forever Chemicals (PFAS) with GIS Technology—featuring Katrina Schweikert

Written by: Meg Scribner


Humans are problem-solvers. Present us with a challenge, and we’ll do our best to solve it. That’s precisely what a team at the University of Maine is doing. This team, led by computer scientist Dr. Torsten Hahmann, is developing a solution to track nationwide per- and polyfluoroalkyl substance (PFAS) contamination. These chemicals, discovered in our farmlands and water sources, are a family of long-lasting chemicals defined by the carbon-fluorine bonds that make them resistant to fire, water, and oil. PFAS have also earned the nickname “forever chemicals” — a term that implies the bioaccumulative effects of PFAS in humans and the persistence of these chemicals in contaminating agriculture, water sources, and other environmental pathways.

The solution is the Safe Agricultural Products and Water Graph, often abbreviated to SAWGraph. When complete, this tool will draw meaningful connections between a web of geospatial data to detect and measure the sites and sources of PFAS contamination. Connection is key to this tool; the web of data it uses comes from sources across the United States. The SAWGraph will be leveraged by the U.S. National Science Foundation (NSF) and the Environmental Protection Agency (EPA) in their efforts to understand and mitigate the contamination.

In GEOTalks Ep. 2, we speak with Katrina Schweikert, a Ph.D. student and researcher working on this project. She illustrates the scope of the SAWGraph and defines what sets it apart as a state-of-the-art tool for tracking PFAS.

History of PFAS

PFAS are a family of chemicals that were invented in the 1930s. These chemicals didn’t become popular until the 1940s and 50s when they were recognized as an industrial marvel. Their range of uses in consumer, commercial, and industrial products solidified this status, and they became widely used. A 2021 article in the International Journal of Environmental Research and Public Health explains that “By replacing carbon-hydrogen bonds with carbon-fluorine bonds, scientists created one of the strongest compounds in organic chemistry; one that has proved to be resistant to heat, water, oil, and time” (Brennan et al. p.1). Closer to the turn of the century, research into the environmental and human health impact(s) of PFAS began.

Common PFAS Sources

Icon of fire extinguisher, cooking pan, detergent bottle, and pesticide container.
“PFAS had great properties that we liked in materials manufacturing like being water-resistant, water-repellent, oil-repellent, firefighting, etc. What we know now is that some subsets of the chemicals can cause increased risk of cancer, complications in pregnant women, decreased vaccine response in children, etc. There’s a lot of research going on to understand the health effects of different subfamilies of PFAS.” -Katrina Schweikert

Studies indicated that these chemicals have adverse, long-term effects on our environment and bioaccumulative effects in humans and other organisms. An emphatic global reaction to this research established the need to act against PFAS contamination. The efforts have been multifaceted, as demonstrated in this publication from Environmental Toxicology and Chemistry: “Strategies have been implemented to reduce emissions, production, and use of specific PFAS. Manufacturers have phased out production of certain PFAS and in some cases replaced them with new PFAS or chemical substitutes” (De Silva et al. p.2). The PFAS phase-outs and chemical alternatives proved to be a step forward.

However, the available data on PFAS contamination needs to be more cohesive and provide more insights for developing solutions. The NSF and EPA realized they needed a way to navigate the research efficiently.

The Safe Agricultural Products and Water Graph

The National Science Foundation awarded Dr. Hahmann’s team funding for SAWGraph — a project aimed at monitoring and understanding PFAS contamination. Katrina Schweikert, a Ph.D. student on Dr. Hahmann’s team, joins us on GEOTalks to share her insights on the project so far.

Visual of data ontology in SAWGraph
“We’re building a geospatial knowledge graph to integrate information about PFAS contamination in agricultural products and water. We look at contamination — in the environment, in our drinking water — and follow it through production chains and transportation chains to understand why this contamination is happening.” – Katrina Schweikert

In our conversation, we discuss SAWGraph’s unique data structure, including how the SAWGraph connects to the NSF’s Prototype Open Knowledge Network (Proto-OKN) program and draws information from the EPA’s CompTox Chemical Dashboard.We also highlight the spatial side of SAWGraph, which will help monitor and track sources of PFAS contamination. Katrina mentions that one of her responsibilities on the SAWGraph project includes using Global Mapper to visualize geospatial data before integrating it into the knowledge graph. The NSF wanted these visualizations available in SAWGraph, stating in the award abstract that it should have “Prototype user interfaces that support query and faceted search, along with offering interactive geo-visualizations and spatial analysis functions.” The NSF goes on to explain that they will use this functionality to efficiently evaluate the SAWGraph as the project continues. To learn more about the dynamic features of the SAWGraph and Proto-OKN, listen to the episode on Spotify, Apple Podcasts, and YouTube Music.

Computer scientists talking in a lab.
“The idea of the Open Knowledge Network is that we can integrate subsets of data and build an ontology on top of it, which builds in semantics and context around what the data is actually representing.” – Katrina Schweikert

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Brennan NM, Evans AT, Fritz MK, Peak SA, von Holst HE. “Trends in the Regulation of Per- and Polyfluoroalkyl Substances (PFAS): A Scoping Review.” Int J Environ Res Public Health. 2021 Oct 17;18(20):10900. doi: 10.3390/ijerph182010900. PMID: 34682663; PMCID: PMC8536021.

De Silva, Amila O., et al. “PFAS Exposure Pathways for Humans and Wildlife: A Synthesis of Current Knowledge and Key Gaps in Understanding.” Environmental Toxicology and Chemistry, vol. 40, no. 3, 29 Jan. 2021, pp. 631–657,

“Proto-OKN Theme 1: Safe Agricultural Products and Water Graph (SAWGraph): An OKN to Monitor and Trace PFAS and Other Contaminants in the Nation’s Food and Water Systems.” U.S. National Science Foundation, 15 Sept. 2023,


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