Watson Lecture: Francois Tissot Discusses the Return of a Long-Standing Environmental Threat After the Eaton Fire

What can past battles against lead pollution teach us about contamination after wildfires? On January 21, 2026, at 7:30 p.m., Francois Tissot, professor of geochemistry and Heritage Medical Research Institute Investigator, will explain how a historic fight against lead contamination guides his current research on toxic metals affecting his local community.

In a public talk called "Lead Contamination: An Old Foe Rises from the Ashes of the Eaton Fire," Tissot will revisit the work of Caltech geochemist Clair Patterson, whose research to determine the age of Earth unexpectedly positioned him to identify the widespread dangers of leaded gasoline and other toxic consumer products. This discovery would ultimately help spur the environmental movement and contribute to the Clean Air Act of 1970. Now, in the aftermath of the Eaton fire, Tissot and his group find themselves on an equally unexpected path as they study the presence of lead and other toxic metals released during the January 2025 fires and what those findings mean for surrounding communities.

"Someone who studied something as obscure as the age of the Earth then ended up making the biggest impact on environmental policy that we've had," Tissot says. "At a much smaller scale, I think that's the trajectory we're following––where we were doing cosmochemistry, and then we were able to use those tools to study the fire––there is a nice parallel between the two stories, which I find very humbling and I am trying to live up to."

Tissot grew up in a village in the southwest of France with a population of a few thousand people. He remembers a childhood of freedom in the open outdoors where he would ride his bicycle and explore. He had always been drawn to science and discovered a specific interest in isotope geochemistry during his time at École Nationale Supérieure de Géologie, where he earned his master's degree in engineering in 2009. That same year, he earned an additional master's degree in sanitary engineering from Luleå University of Technology in Sweden. He later completed his doctorate in geochemistry and cosmochemistry at the University of Chicago in 2015.

About the series

The Watson Lectures offer new opportunities each month to hear how Caltech researchers are tackling society's most pressing challenges and inventing the technologies of the future. Starting at 6 p.m., join a community of curiosity outside Beckman Auditorium to enjoy food, drinks, and music together before each lecture. Interactive displays related to the evening's topic will give audience members additional context and information. Guests are also encouraged to stay for post-talk coffee and tea as well as the chance to chat with attendees and researchers.

Watson Lectures are free and open to the public. Register online to attend.

A recording will be made available on our YouTube channel.

Recommended Reading:

Brush up on the topic before the lecture! Click on the titles below to purchase from our partner bookseller, Vroman's.

• Toxic Truth: A Scientist, a Doctor, and the Battle over Lead by Lydia Denworth
• Isotopes: A Very Short Introduction by Rob Ellam
• The Pyrocene: How We Created an Age of Fire, and What Happens Next by Stephen J. Pyne