Something in the Air May Create Serial Killers

Between the '70s and '90s, the Pacific Northwest wasn't just a foggy haven for flannel and coffee—it was ground zero for some of the most notorious serial killers in American history. One after another, the likes of Ted Bundy, the Hillside Strangler, and the Green River Killer emerged in the area around Seattle and Tacoma. But what caused such a sudden surge in violence? Pulitzer Prize-winning author Caroline Fraser, who was 7 years old and growing up just a few miles away during Bundy's murderous spree in 1974, thinks she knows what connects all of these killers: toxic lead in the air. In her new book, Murderland: Crime and Bloodlust in the Time of Serial Killers, she investigates the "lead-crime hypothesis," a theory that exposure to lead during childhood can result in increased criminal behavior later in life.

"Many studies connect lead exposure to a particular kind of frontal cortex damage that leads to heightened aggression," she tells Time. "This is observed largely in males." As a native of the region, she suspects one possible reason why this could have especially applied to the Pacific Northwest: a large smelter in the middle of Tacoma. "All the emissions were being spread over not just Tacoma, but the entire Pacific Northwest in this plume that was up to a thousand square miles," she says. Although she says it's "well accepted" that between 20% and 50% of the drastic rise in crime during the '80s and '90s can be attributed to lead, the violence in the region was an epidemic. "Crime was up in all of America, but it was up in Washington state by almost 30%—three times the national average."

Fraser admits that the lead-crime hypothesis is still relatively new, having first gained mainstream attention in the early 2010s, but she explains that the basis for the theory has been around for decades. "In the '50s and '60s, geochemist Clair Patterson proved that lead exposure had caused what he called 'a loss of mental acuity,'" she said. "[And] there's a clear association between the withdrawal of leaded gas in the '90s and the drop-off of crime." Still, she believes there's ample evidence to support the hypothesis. She tells Slate, "I can't prove, for example, that Ted Bundy committed his crimes because of lead exposure. But what I can do is show you how much lead exposure he got." (More serial killers stories.)