Forever chemicals, the nickname for polyfluoroalkyl and perfluoroalkyl substances (PFAS) known for their durability, are a class of chemicals that sometimes appear in tap water but aren’t widely understood or subject to much federal regulation. What we do know is that these substances appear in items we encounter on a daily basis, such as dental floss, and have been linked to a number of health problems. Recent research suggests that these chemicals are becoming more common in tap water.
Cindy Hu, a data scientist at Mathematica, studies how humans are exposed to and affected by this class of emerging contaminants in drinking water. On this episode of On the Evidence, Cindy and I discuss the prevalence of these chemicals in our drinking water, as well as their health implications and ways to address them through public policy.
How did you personally become interested in water quality and contaminants in our water?
I grew up in China, where tap water is not potable. I have a vivid memory of a hot summer day, and I was thirsty. I just wanted to drink some water, but I had to wait for my parents to boil it and wait for it to cool down and then I could drink it. It was a painful process. When I first came to the United States, I was amazed by how people could drink from the tap. It’s a great source of hydration, and it impacts the lives of so many people, even though the individual impact is pretty small.
You just won an award for a data visualization about water quality. What does it do?
The website is called What is in My Water? It's a collaboration between me and two other researchers at Harvard University. About 80,000 chemicals are used in commerce and industry today, but only 96 of them are regulated in U.S. tap water.
There are great public data that have critical information about what kind of unregulated chemicals are in people’s drinking water, but the public has great difficulty accessing and making sense of those data.
One of our biggest goals is to create a one-stop resource for people to understand the current chemical occurrence in tap water, health implications of chemicals in tap water, and actions individuals can take to protect themselves and protect their families.
One of the categories of contaminants highlighted on the website is highly fluorinated compounds. You also focused on this group of contaminants in your research. Why?
A class of chemicals on the website is called highly fluorinated chemicals, otherwise known as PFAS. They were the focus of my doctoral dissertation research for the past six years because they are detectable in virtually all Americans. They are also associated with a wide suite of a diverse health effects, such as kidney cancer, high cholesterol, and immune suppression. They last forever. The chemical feature of this class of compounds is the carbon–fluorine backbone, which is the strongest chemical bond we know in organic chemistry.
However, there are so many important scientific questions we do not know about this class of chemicals, such as where do they come from? How do people get exposed to them? What are the health effects after people get exposed to them? Is there anything we can do to remove them from water, food, or air? And is there any treatment for exposure to PFAS?
In addition to the scientific questions, I'm also interested in management or policy questions related to this class of compounds. Two chemicals in this entire class of compounds were restricted in the early 2000s, but since their restriction, manufacturers have come up with substitutions that also belong to the bigger family of PFAS, and we do not know as much about the health impacts of exposure to these chemicals.
Where might people encounter these chemicals?
The chemical structures of these compound give them desirable industry properties, so they’re very useful. They allow air to pass through, but they stop water and oil from passing through. We put them on anything that we want to keep clean. We use them for Scotchgard on carpet and Teflon on non-stick frying pans. We also use it for firefighting foams because they can isolate oxygen from the burning fuels, and they can stop fire really effectively that way.
To what extent are policy makers or regulators taking action to protect people from drinking contaminated water?
I think we need to be very clear that U.S. drinking water quality overall is pretty strong, and it’s strong because there are a lot of laws and programs in place to safeguard them. For example, for regulated chemicals, each water utility is required to provide an annual consumer confidence report, and water utilities will basically run down all the 96 chemicals that are regulated and tell the consumers the regulation level and the actual level in their drinking water.
For the unregulated chemicals, the U.S. Environmental Protection Agency’s Unregulated Contaminant Monitoring Rule program collects data every two years for a priority list of unregulated chemicals. The EPA will organize labs to analyze them, and the regulators will take a look at the data and make a decision on whether the occurrence data are severe enough for the federal government to take actions on regulating them.
PFAS are included in the Unregulated Contaminant Monitoring Rule program, but as public attention rises around these chemicals, many states, such as New Jersey, Michigan, and New York, have taken action to consider or initiate regulating these chemicals in drinking water, and they have all proposed a maximum contaminant level that is lower than what the EPA suggests is safe or acceptable level for drinking water.
You’ve been studying PFAS for six years, and you continue to study water quality today. Where do you continue to see knowledge gaps in our understanding of contaminants in public water, and how are you trying to close those gaps?
One important gap in the field is a data gap. The U.S. has made a lot of progress in improving air quality for the past 40 years, and that is partially a result of having very good air quality monitoring data that has great coverage and updates every day. Everybody can look up on their phones what the air quality is every day in their city. The field of water pollution research is not quite there yet. A lot of the methods we use are still pretty traditional. Researchers go grab a sample and bring it back to the lab to analyze. This approach is labor intensive, has very low coverage, and has a long delay time.
One of my ongoing projects is to use machine-learning techniques and predictive modeling to try to predict which areas have higher risks of contaminated water so that we can target the sampling resources [at the high-risk areas] and prevent problems from happening in the first place.