I began my own chemical journey on an October morning at the Mount Sinai Hospital in New York City, where I gave urine and had blood drawn under the supervision of Leo Trasande. Trasande specializes in childhood exposures to mercury and other brain toxins. He had agreed to be one of several expert advisers on this project, which began as a Sinai phlebotomist extracted 14 vials of blood—so much that at vial 12 I felt woozy and went into a cold sweat. At vial 13 Trasande grabbed smelling salts, which hit my nostrils like a whiff of fire and allowed me to finish.

From New York my samples were shipped to Axys Analytical Services on Vancouver Island in Canada, one of a handful of state-of-the-art labs specializing in subtle chemical detection, analyzing everything from eagle eggs to human tissue for researchers and government agencies. A few weeks later, I followed my samples to Canada to see how Axys teased out the tiny loads of compounds inside me.

I watched the specimens go through multiple stages of processing, which slowly separated sets of target chemicals from the thousands of other compounds, natural and unnatural, in my blood and urine. The extracts then went into a high-tech clean room containing mass spectrometers, sleek, freezer-size devices that work by flinging the components of a sample through a vacuum, down a long tube. Along the way, a magnetic field deflects the molecules, with lighter molecules swerving the most. The exact amount of deflection indicates each molecule's size and identity.

A few weeks later, Axys sent me my results—a grid of numbers in parts per billion or trillion—and I set out to learn, as best I could, where those toxic traces came from.

Some of them date back to my time in the womb, when my mother downloaded part of her own chemical burden through the placenta and the umbilical cord. More came after I was born, in her breast milk.

Once weaned, I began collecting my own chemicals as I grew up in northeastern Kansas, a few miles outside Kansas City. There I spent countless hot, muggy summer days playing in a dump near the Kansas River. Situated on a high limestone bluff above the fast brown water lined by cottonwoods and railroad tracks, the dump was a mother lode of old bottles, broken machines, steering wheels, and other items only boys can fully appreciate.