What's in the Water? Lesson 5: The Health Effects of PFAS
Lesson 5 of the "What's in the Water?" PFAS Contamination Unit" addresses the crucial question of what we know about how PFAS impacts our health, and how that information can (or cannot) be used in the regulatory process via the U.S. EPA. Students explore abstracts from primary literature, and practice crafting PECO statements that could be used to effectively aggregate results across multiple studies. They compare and contrast animal studies (which can establish more reliable causal relationships between exposures and outcomes, but only for those animals) and human studies (which are, by ethical necessity, correlational only), and consider how those studies relate to the EPA's environmental public health paradigm (which requires many different linkages to be well-established).
This activity has been used in an introductory-level university course in environmental science that enrolls both majors and non-majors, as well as a summer intensive science course for high school students, both in North Carolina where the unit is set. It could easily be adapted to other locations where PFAS contamination is present, as well as to geology or biology courses.
Skills and concepts that students must have mastered
Students should be familiar with the concepts of independent and dependent variables in experimental research. If possible, it would be helpful to review the difference between correlation and causation, as well.
How the activity is situated in the course
This is the fifth instructional lesson of the "What's in the Water?" PFAS Contamination Unit". Prior to this lesson, students will have been introduced to the unit-long community-engaged project, met the community partners to understand the local PFAS contamination situation and the community partner's needs, and completed the Benchmarking Activity to take stock of their prior knowledge of water and water contamination. In Lesson 1 they learned about the natural and urban water cycles, focusing on PFAS contamination and how it cycles through the environment. In Lesson 2, students compared and contrasted emerging and established contaminants, and learned about the PFAS family of chemicals and their history. Lesson 3 took students through an analysis of remediation options for the local water contamination crisis. In Lesson 4, students read about and analyzed data visualizations related to environmental justice in the U.S., including issues of access and cost. In this lesson, students investigate human and animal studies of PFAS chemicals and their impacts on various health outcomes, and put that research in the context of the EPA's Environmental public health paradigm.
Content/concepts goals for this activity
- Students will explore the state of scientific knowledge of PFAS health impacts on humans and animals.
- Students will consider the role of human vs. animal studies in establishing the linkage between contaminant exposure and public health.
Higher order thinking skills goals for this activity
- Students will explain why definitively linking a particular chemical exposure with a particular health outcome is challenging for scientists.
Other skills goals for this activity
- Students will practice reading and deciphering primary literature.
- Students will practice synthesizing knowledge across multiple studies using PECO statements.
Description and Teaching Materials
In this lesson, students begin to address the critical question, "what is the impact of PFAS on human health?" They review abstracts from the current scientific literature, compare and contrast what is known from human vs. animal studies (and why), and evaluate that knowledge for its ability to address the EPA's environmental public health paradigm to understand why regulation of emerging contaminants like PFAS has been challenging to advance. Guiding questions for the lesson include
- What is known about the health impacts of PFAS as emerging contaminants? From human studies? From animal studies?
- What is known about the health impacts of PFAS on wildlife, and what are the implications of those impacts?
This homework assignment introduces students to the idea that multiple studies are often needed to draw conclusions about the relationship between an environmental contaminant and a health outcome. The assignment explains the PECO framework (Population–Exposure–Comparator–Outcomes) as a framework for selecting and synthesizing multiple studies in a literature review (Morgan et al., 2018). Students practice crafting a PECO statement related to the PFAS family of chemicals and, using their abstract, select studies listed in the PFAS Systematic Evidence Map (link in the resources section below) that would fit within their review. This is no easy task, and we recommend allocating the first 15 minutes of class to asking a few students to share their PECO statements and the studies that fit them (if possible, review the students' submissions before class and choose a few effective ones to highlight).
Opening Activity and Discussion
Share with students an update from your local concerned citizen: There has been a lot of buzz about PFAS around town. People are sharing stories about how the water tastes or smells, and telling their neighbors about their son/aunt/grandparent who was recently diagnosed with a disease. Some members of the community pass around articles about potential health impacts of PFAS exposure. Could PFAS in the drinking water be to blame for the illnesses that are popping up in Pittsboro? At what point can we declare that an environmental pollutant causes health effects?
Show a clip from the video, A Town FIghts Back: The Toms River Story, and/or ask students to skim through one of the articles provided below (also linked in the Background section).
● Popular Press articles: Slate Magazine and NY Times
● Peer-Reviewed article: Sharpe & Irvine, 2004
Discuss the challenges involved in determining clear connections between environmental hazards and human health. To tie this discussion back into the homework, ask, "How might having a clear and defined PECO, like we did for homework, help researchers close in on the answer to our question?"
Mini-Lecture: Environmental Public Health Paradigm
In the 1970's public attention increasingly focused on environmental issues and studies linking environmental triggers and human health impacts (e.g smoking and cancer, coal dust and COPD, etc.). The EPA was born during this time in order to consolidate the federal government's environment-related duties. As part of its "Report on the Environment", the EPA investigates exposures to contaminants and their potential impacts on human health.
Show students the environmental public health paradigm (https://www.epa.gov/report-environment/human-exposure-and-health) to illustrate the factors that may be involved in the development of disease as a result of exposure. In order for a link to be made, all 6 blocks must be clearly established and understood. Of course, real-life examples are complex and non-linear. For example, we know that
- other factors (like lifestyle, genetics, and pre-existing conditions) can also lead to disease, and it may not be possible to control or ignore those potential impacts on human health.
- Different contaminants can cause/increase risk of the same disease
- Not every person who is exposed will experience adverse health outcomes
Small Group Activity
Students will now have an opportunity to work in their small group to work with their team to digest some of the health data in the Lesson 5 Data Packet (Sources 9 -11). Their goal is to determine if there is enough evidence to support the claim that contaminated drinking water could be leading to disease in Pittsboro. You might ask all groups to review all sources at a basic level, or (as reflected in the instructor slides) assign a particular source to a few groups, allowing them to do a deeper dive.
There are several limitations to this data set, and it may be with it to discuss those before, during, or after the activity. It may be helpful to assign groups one type of health data and/or ask them to select one or two from each category. During their analysis, they should reflect on the following questions:
- Are all the data sources equally useful? Why or why not? (critically evaluate how applicable the data is to the general human population and/or Pittsboro in particular)
- What confounding variable can you think of that could make drawing a conclusion difficult? (great time to practice Scientific Method/experimental design!)
- Based on what you know so far, are the concerns of the residents valid? Why or why not? What might be the next step for residents? Town leaders? (having each group compose one or more POV statements here could be useful to frame the class discussion)
Students should be able to draw some general conclusions about links between PFAS exposure and changes in specific health variables. This is a great time to talk about the difference between correlation and causation, and to talk about how variation in research studies makes it difficult to draw sound conclusions. It may be beneficial to tie in some points from the earlier conversation about proving cancer clusters.
Mini-Lecture: Impacts of PFAS on Wildlife (optional)
Depending on the time available and the depth at which you'd like to go, this would be a wonderful opportunity to step back a bit from Pittsboro and have a broader conversation about the impact of emerging contaminants like PFAS on wildlife. Content from the Background section may be helpful to frame your discussion. You could begin a class conversation with one or more of the following conversation starters:
- What is the value of researching the health impacts of PFAS and other water contaminants on wildlife (group could discuss both conservation and economic implications)
- In what ways might terrestrial and/or aquatic organisms be impacted differently than humans (discuss the various pathways of exposure - aquatic animals living in it will have much great exposure and much less control over the amount of exposure
- From a health standpoint, what considerations should be made for wild plants and animals that rely on the Haw River? Livestock? Pets?
- What information do we need to share with hunting and fishing enthusiasts in the area? Keep in mind that the Haw River empties into Jordan Lake, which is a major tourist attraction in the region.
Synthesis and reflection questions
The following questions and discussion posts may be helpful as you conclude the lesson. These might be used as discussion prompts, or you might ask students to select one and write briefly about it as an exit card.
- Does the information from today's lesson change your perspective on emerging contaminants in any way? How?
- Many will argue that without solid scientific evidence to prove exposure to PFAS leads to adverse health outcomes, there is no need to regulate these compounds. What are the arguments in favor of, and in opposition to, this sentiment?
- POV Statements: write a statement from the perspective of a Pittsboro resident based on what you know so far. You could write a reflection expressing your feelings about the water issue (what bothers you the most), your concerns about yourself and others in the community, or something else. In your opinion, what should happen next?
Lesson 5 Class Plan and Timeline (Microsoft Word 2007 (.docx) 8kB Jan26 22)
Lesson 5 Pre-Class Homework (Microsoft Word 2007 (.docx) 11kB Jan26 22)
Lesson 5 Instructor Slides (PowerPoint 2007 (.pptx) 433kB Jan26 22)
Lesson 5 Background Information for Instructors (Acrobat (PDF) 987kB Jan26 22)
Lesson 5 Data Packet (Acrobat (PDF) 1.7MB Jan26 22)
Teaching Notes and Tips
Students in our class struggled substantially with understanding PECO statements and how to select studies that fit them (or iteratively revise the PECO statement, if studies are not available). If possible, it would be helpful to introduce the concept at the end of the prior class and provide an example you have worked through yourself. Alternatively or additionally, asking students to tackle the homework in pairs might be a good way to make the difficulty more manageable.
As with all lessons in this unit, assessment within the lesson is formative. As individuals and groups share out, the instructor can gauge understanding and ask follow-up questions that foster more nuanced understanding of the strengths and limitations of animal and human PFAS studies. Using the synthesis and reflection questions at the end of the lecture slides as an exit card activity would give the instructor the opportunity to quickly review new and potential mis-understandings from the day. Ultimately, new or revised understandings from all lessons in the unit should be reflected by student answers to the Benchmarking Activity completed at the conclusion of the unit, which can be used for summative assessment purposes.
References and Resources
Additional sources and resources are included in the Background Information for Instructors packet.
Other materials in the "What's in the Water?" PFAS Contamination Unit":
- What's in the Water? Benchmarking Activity
- What's in the Water? Community Engagement Project
- What's in the Water? Lesson 1: Water Cycle and Watersheds
- What's in the Water? Lesson 2: Introduction to Emerging Contaminants
- What's in the Water? Lesson 3: The Economic Challenges of Clean Water
- What's in the Water? Lesson 4: Drinking Water & Environmental Justice
- What's in the Water? Lesson 6: Drinking Water Quality Regulation in the U.S.