In a talk for the California Historical Society, I discuss San Francisco’s hidden nature. Despite my best efforts to remain informative, funny, and surprising, things go off the rails and get slightly uncomfortable (you’ll know what I mean when you get there). From the gold rush to the bay itself to our delicious food, I uncover the hidden geological history responsible for it all.

In the mid-1980s, a small problem began to surface in a relatively obscure corner of the world. In 1994, just about a decade later, the World Health Organization published a statement that this little problem had developed into “the largest mass poisoning of a population in history.” On today’s show, we speak to the doctors, epidemiologists, and geologists who helped hunt down the origin of this tragic event. Join us as we venture through the human body and through geologic time to uncover the twists and turns and remarkable coincidences responsible for this ongoing epidemic.

This story was originally published in 2013 on the Generation Anthropocene podcast.