2025 Talented 12: Shira Joudan

Trifluoroacetic acid is a contaminant that likes to move around. Scientists have found the chemical, known as TFA, in the deep ocean, in the Arctic, in plants, and in our blood. TFA also doesn’t biodegrade, so it persists in the environment. But unlike many other persistent pollutants, TFA has few direct sources. Most comes from reactions involving other contaminants. Shira Joudan identifies and studies these reactions to find out exactly where TFA is coming from.

Joudan is interested in how contaminants get where they are “and how we can understand chemical reactions to better understand their fate,” she says. This information can help scientists estimate our exposure to contaminants, guide policymakers as they design regulations, and teach chemists how to build molecules that don’t break down into something problematic.

Currently, scientists have limited data on TFA’s toxicity in humans and other organisms. But TFA is the most abundant per- and polyfluoroalkyl substance (PFAS) found in the environment—although not everyone groups TFA with PFAS—and its levels are growing. Levels of TFA in different environments are as much as 10 times as high as levels measured a few decades ago.

Joudan thinks that persistent chemicals like TFA are worth studying because, as they stick around, they can reach concentrations that might be toxic.

Policymakers in the US and elsewhere haven’t yet tried to regulate TFA, in part because of a prevailing narrative that there are large natural sources of it, Joudan says. As a postdoctoral researcher at York University in Ontario, Joudan published, with her adviser Cora Young, a review that challenged this narrative.

Data supporting natural sources of TFA include measurements of the chemical in preindustrial samples. In the review, Joudan evaluated these studies’ methodologies. TFA is a tricky compound to pin down because it is volatile, she says, so it is easy for sources in the laboratory, including other samples, to contaminate what researchers are studying. Joudan concluded that many of the studies of preindustrial samples were not rigorous enough to definitively measure TFA levels in the old samples.

The review has already attracted the attention of international groups that regulate or monitor TFA and other pollutants. For example, the World Meteorological Organization cited the review in a report that discusses the formation of TFA. The review paper “has changed the tone of some of the discussions about whether this molecule can be regulated,” Young says.

Young thinks that Joudan’s strong analytical knowledge and science communication skills were key to the success of the review. Joudan “is able to take these messages and distill them in a way that that people really respond to, much more than other scientists I’ve met in my life,” Young says.

Now Joudan leads a research group at the University of Alberta and continues to investigate TFA’s sources in the environment. Earlier this year, she published a paper studying how the antidepressant fluoxetine (Prozac) can break down to TFA. Wastewater treatment plants don’t always remove pharmaceuticals like fluoxetine, so the chemicals can escape into the environment through the treated waste.

Researchers have known that fluoxetine can transform into TFA photochemically, and they have suspected that other pharmaceuticals and agrochemicals with aryl trifluoromethyl groups could as well. Joudan was interested in understanding the conditions and mechanisms behind these transformations. Her lab studied what happens to 4-(trifluoromethyl)phenol, a known breakdown product of fluoxetine, under ultraviolet light. The researchers found that it forms more TFA in acidic conditions and more fluorine in basic ones.

By leading to a better understanding of which molecules are prone to forming TFA and under what conditions, Joudan’s research could someday help regulators draw up effective policies to limit TFA release into the environment. Also, Young says, “if we know the structural conditions that lead to the formation of TFA and the structural conditions that do not,” then chemists can learn to avoid making molecules that yield the contaminant.

Joudan plans to continue studying molecules that might form TFA. “There are many, many chemicals in the environment, and only a small number produce harmful effects,” she says. “Making sure we are prioritizing research efforts to identify those, and then understand their presence and behaviors, is probably the biggest challenge” in the field.