Something in the water
CU Boulder students explain the CCL5
When my wife and I bought our house a few years ago, the neighbors told us, “I think there’s something in the water.”
Two previous couples had owned the house, each for a two year stint, gotten pregnant, then moved away. They saw another young couple move in—with no kids—and thought it pertinent to warn us. Well sure enough, we had our first child about 9 months later.
Of course, nobody ever thought there was actually something in the water, we were just predictable buyers. Another young couple at the same life stage, attracted to the same little farm house aesthetic. But isn’t that turn of speech interesting? We see a pattern and, humorously, we blame it on the water. Maybe that reveals something deeply suspicious and skeptical in our shared consciousness, like the character Bobbie Markowe’s paranoia in The Stepford Wives: “I think there’s something in the water turning us into house-fraus!” The phrase quickly veers into horror, too, conjuring ideas of mind-control and great white sharks coming from the deep. But, boringly, I prefer to think that our reliance on the phrase actually tells of a shared understanding of the importance of water quality to our collective well-being.
The earliest instance of the phrase I could find dates to 1855 in a collection of reports entitled Food and its Adulterations: Comprising the Reports of the Analytical Sanitary Commission of “The Lancet” by Arthur Hill Hassall, M.D. This was a time when the scientific community still did not fully understand germ theory and physicians were struggling to explain how diseases spread through the population. Cholera was a dreaded killer in 1850s Europe (and still is today in many places). But the possibility that it was spread through the water was still a new idea. “It is well known that cholera raged with frightful and destructive violence in … mining towns and villages in South Wales,” reads the report. “And in all these places I heard the opinion expressed by many of the population that it was something in the water.” (The creepy suspicion around the water supply in The Stepford Wives was simply the day-to-day reality in the 19th century).
In any case, our adoption of epidemiological language to explain curious patterns or quirks shows, I think, that people have an embedded understanding of risk associated with drinking water. Our regulatory framework, too, reflects what we intuitively know. Something called the Unregulated Contaminant Monitoring Rule (UCMR), established by an amendment to the Safe Drinking Water Act in 1996, is essentially the federal government’s acknowledgement that “there’s something in the water.” There are more possibilities than we can control and we know it. But! We can at least monitor what’s there. The UCMR does this by establishing the Contaminant Candidate List or CCL, which is a formal list published by the EPA every five years with chemical and microbial contaminants that are currently unregulated, but are “known or anticipated to occur in public water systems.” The EPA is currently monitoring for 30 contaminants out of the 66 listed in the fifth iteration of the CCL, referred to as the CCL5.
In my class on water quality and health this semester, my students were a little unnerved to learn about the UCMR and CCL. When you pull back the curtain and realize there’s a long running list of potentially harmful things that could be in our water but we don’t know much about, it takes some rethinking. I don’t mean to fearmonger, nor cast distrust on the system (my questionable choice of cover photo for this post aside). As I wrote about in my last post, that’s just counterproductive. But the point is, there are unknowns. And facing up to them is a little uncomfortable at first.
So, I asked the students in my class to choose a contaminant (other than PFAS) that interested them from the CCL5 and demystify it by writing a short blog post about it. I wanted them to dig into the science of these obscure contaminants in our drinking water supplies. What are they? Where do they come from? What does the research indicate about the risk posed? Why the heck are they on this list? Understanding the science is the antidote to trading in fear.
Below are a few excerpts from the best posts. The students grappled with issues of risk, uncertainty, policy, and regulation. They didn’t shy away from taboo topics and thoughtfully explored the equity issues surrounding different contaminants. In short, I was proud of them. They made me laugh, think, and learn some new things. I share these here (with their permission) in hopes they do the same for you.
Legionella: A Danger in the Mist
Alice Godwin
Have you heard of Legionella? No, unfortunately, it’s not a new gelato flavor. Instead, it’s a bacteria lurking in water that can cause serious illness. Legionellosis, the disease it causes, comes in two forms: Legionnaires’ disease, a severe type of pneumonia, and Pontiac fever, a milder flu-like illness. People become infected by breathing in tiny water droplets contaminated with the bacteria, like mist from showers, hot tubs, or cooling towers. While Pontiac fever is usually mild, Legionnaires’ disease can be life-threatening, particularly for vulnerable populations … Each year, between 8,000 and 18,000 people in the U.S. are hospitalized with Legionnaires' disease according to the EPA … Legionella bacteria can thrive in water systems when certain conditions are present. Stagnant water allows biofilms, a slimy layer of bacteria and other microorganisms, to form, creating a perfect breeding ground … The Colorado Department of Public Health and Environment’s Waterborne Disease Epidemiologist stated, “From a public health standpoint, we don’t recognize any safe level of Legionella… The issue is, since Legionella isn’t currently regulated, it’s difficult to determine what levels are ‘safe’—we’re focused more on addressing high levels when they pose a clear health risk.” It is a difficult grey-area to navigate, as public health agencies are looking to respond to and monitor a bacteria that no one is required to test for.
BPA in Water: Should You Be Concerned?
Peter Bernot
Walking down the isle of my local supermarket, I pass thousands of products wrapped in plastic. I have been trying to be more aware of my plastic consumption, as I know with microplastic research that it is not the best option for me or the planet. When I eventually reach the canned vegetables, I am happy to buy them because I think they are safer and plastic free. When I pick up a can of black beans, I notice a “BPA Free” tag in the right corner. “What is BPA?” I think, unaware of the major risks that lie in canned products and the world of BPA chemicals … Bisphenol A or BPA is a popular, massively produced chemical used in a wide range of products to produce polycarbonate plastics … BPA is currently not being monitored by the EPA but could be in the future if the evidence presents itself as a major concern … It is important to take a precautionary approach for [BPA’s] known hormone-disrupting effects. Even though the levels could be low in water in some areas, it is better to be safe. As discussed by [the professionals I interviewed], it would be beneficial to stop BPA from getting into people’s bodies through all potential manners. The best step, however, is reducing the production of them in the first place.
The Ugly Side of Beauty
Allie Meisler
It’s 2025 and everything is seemingly out to get us. The water we drink, the air we breathe, and even the makeup we put on our face, all of it comes with warnings, risks, and the ever-looming possibility of causing cancer. One of those lurking threats? N-Nitrosodiethylamine (NDEA), a disinfection byproduct (DBP) that isn’t just in your tap water but also in cosmetics, tobacco, and even some medications. The kicker? Despite its known health risks, it’s not even federally regulated in drinking water … Certain communities are more likely to be exposed to NDEA and other DBPs in their drinking water, particularly those relying on surface water sources like rivers and reservoirs. Rural areas, low-income communities, and places with aging water infrastructure may face higher risks, as their treatment facilities might struggle to balance effective disinfection with minimizing harmful byproducts. Additionally, resort towns or areas with seasonal water use can experience fluctuating water quality, leading to higher DBP levels when water sits in storage for long periods. Environmental justice concerns arise when underfunded or historically marginalized communities lack the resources to upgrade water treatment systems, monitor contaminants more frequently, or advocate for stronger regulations, leaving them disproportionately exposed to potential health risks.
The invisible toxin in your shampoo...and your water!
Azul Ocampo-Manzo
Imagine this: you step into a warm shower, wash your hair with your favorite shampoo, and let the soapy water wash down the drain. The scent is refreshing, the bubbles feel luxurious, and you’re left feeling clean. But what if I told you that hidden inside that bottle (and inside your water supply) is a chemical linked to cancer? A chemical that doesn’t even have to be listed on the label. Meet 1,4-Dioxane, a sneaky, colorless liquid that has found its way into our water, our homes, and our bodies. … 1,4-Dioxane isn’t something you can see, taste, or smell. However, it’s not deliberately added to products or water - it’s a byproduct, an uninvited guest created during the manufacturing of shampoos, soaps, detergents, and even some baby products … It travels down your drain, through wastewater treatment plants (which,unfortunately, aren’t designed to remove it), and straight into rivers and groundwater. And from there, it can end up in your drinking water. … The EPA classifies 1,4-Dioxane as a “likely human carcinogen,” meaning long-term exposure could increase the risk of cancer. The chemical is also linked to liver and kidney damage and can be absorbed through both ingestion and skin contact. Communities across the U.S. are already facing the consequences. Long Island, New York, for example. Testing in recent years revealed alarming levels of 1,4-Dioxane in the local water supply, leading to lawsuits and costly filtration upgrades. New York became the first state to set its own drinking water limit for 1,4-Dioxane at 1 part per billion, but no other states have followed suit.
The Price of Perfection: 1,4-Dioxane’s Hidden Threat in Beauty and Water
Max Peery
As a self-proclaimed movie buff, I usually gravitate toward Oscar-worthy films,
particularly those that explore social conflict. One film that caught my attention this year was The Substance. In a desperate attempt to stay young and remain in the industry, she takes a mysterious substance—with unintended consequences. … The film vividly illustrates the toll beauty products and societal pressures can take on the body, with the protagonist becoming grotesquely deformed. This resonated with audiences because it made the often-overlooked impact of everyday products feel immediate and tangible. These products are usually slow-acting dangers with hidden risks, but the film makes their impact vividly clear … What does a film critiquing the beauty industry have to do with water quality? Enter 1,4-Dioxane—a chemical as invisible as the societal pressures The Substance exposes. Unlike the film’s grotesque transformations, 1,4-Dioxane lurks silently in beauty products, water systems, and, ultimately, our bodies. Colorless and highly soluble, it moves effortlessly from products to watersheds to human consumption. So why is this chemical an issue? Well, currently Dioxane is on the EPA’s CCL 5 list, which identifies high-concern contaminants. It has been found in 45 states with 39 of those putting up a health advisory affecting over 100 million Americans.
Is Thiamethoxam the “Next Big Thing” in Water Contaminants?
Emma Jauron
Thiamethoxam (TMX) belongs to a class of insecticides called neonicotinoids (neonics). … A research scientist at the University of Iowa told me, “The primary use of thiamethoxam is to kill sucking and chewing insects that feed on plant tissues. Neonics in general, and thiamethoxam in particular, are widely used as seed treatments. It’s difficult to buy seed corn which isn’t treated with at least one neonic.” Corn is not only food; it also produces a variety of products. Meaning there is a larger list of TMX users than one believes. The list would include farmers, seed-producing companies, ethanol users, livestock, meat eaters, industrial products consumers (starch, sweeteners, corn oil, and beverage and industrial alcohols), etc. Even though the top user of TMX is corn, many other plants have TMX seed coating. … An Iowa study compared the concentrations of neonics in well water by testing the farmers' urine. 100% of the urine and 6% of the well samples were positive for TMX … Farmers have the highest risk, but water treatment plants do not regulate TMX. If many farms are near the drinking water source, then every citizen is at risk of it entering their system.
Killing Weeds or Killing People? Diuron in Our Water (I know this is way too alarmist, but I liked the vibe)
Cooper Kern
Diuron is a powerful herbicide widely used to control weeds before they
sprout. Its ability to stop unwanted plant growth makes it a powerful tool
for farmers and landscapers alike, but the risks of this chemical, which is
prone to lingering in our environment for extended time periods, have been
linked to serious adverse health effects. The EPA considers diuron an
emergent contaminant, meaning it has been found in public drinking water and
is treated as a potential risk. As with many of the emerging contaminants
identified by the EPA, the dangers of diuron are still largely unknown … One user of diuron is Jackson Hole Mountain Resort, which employs it to mitigate the spread of noxious weeds. I spoke to the manager of the summer “mountain projects” team responsible for weed management. The most important thing I learned from him was that people using diuron and similar chemicals often have no idea about the potential negative health effects or environmental impact. From his perspective, he is required to get rid of weeds, and the best tool for the job is the one he will use … The real problem is that we don’t know how dangerous diuron is, and the people using it don’t know either.