The Pacific Northwest has long been infamous for its chilling legacy of serial killers. From Ted Bundy to the Green River Killer, the 1970s and ‘80s saw a disturbing concentration of violent criminals in this region, earning it the grim moniker “America’s Killing Fields.” Now, a new book presents a compelling, if controversial, theory as to why.

Pulitzer Prize-winning author Caroline Fraser, raised in Seattle just miles from where Bundy committed his early crimes, investigates this question in her new release, Murderland: Crime and Bloodlust in the Time of Serial Killers (out June 9). At the heart of Fraser’s argument is the “lead-crime hypothesis”—the idea that exposure to toxic metals like lead, copper, and arsenic significantly altered brain development in children, increasing aggression and the risk of psychopathy.

Fraser draws from personal experience—recalling how Bundy’s 1974 killing spree at Lake Sammamish took place just six miles from her home—and from extensive research on industrial pollution in cities like Tacoma, Washington. There, ASARCO's smelter routinely blanketed neighborhoods with airborne lead and arsenic, leaving behind a legacy of environmental decay and, possibly, neurological damage.

“Between the leaded gasoline and smelting emissions, there was an incredible volume of neurotoxic exposure in the postwar years,” Fraser explains. “This wasn’t just dirty air—it was brain-altering.” Her book points to a stark correlation: as lead levels peaked, so too did violent crime; as lead was phased out in the 1990s, crime plummeted.

While earlier theories focused on factors like child abuse, fatherlessness, and mental illness, Fraser emphasizes that environmental toxicity is a largely overlooked variable. Studies cited in Murderland link lead exposure—particularly in boys—to frontal lobe damage, reduced impulse control, and heightened aggression. These traits, she suggests, may have laid the neurological groundwork for violent offenders like Gary Ridgway and Israel Keyes, who also grew up in the region’s toxic shadow.

Fraser doesn’t discount other influences. She acknowledges the rise of media sensationalism, the FBI’s growing (but often flawed) profiling efforts, and the cultural mythologizing of killers like Bundy—who, far from being a genius, she describes as a “pathetic loser” undeserving of the glamour often ascribed to him.

Importantly, Murderland challenges the romanticized image of serial killers as brilliant masterminds. “They’re not Hannibal Lecter,” Fraser says. “They’re broken people, often with severe cognitive and emotional impairments. The media built them up. The truth is far more tragic.”

As for why the numbers have dropped so drastically—669 serial killers in the U.S. in the 1990s, 371 in the 2000s, and just 117 in the 2010s—Fraser credits better prenatal care, greater awareness of mental health, improved parenting, and the phasing out of environmental toxins.

“We’ve made healthier humans,” she says. “Not because killers disappeared, but because we stopped growing them the same way.”

In Murderland, Fraser offers a sweeping, deeply researched, and highly personal examination of a chilling era in American history. Her central thesis—that America’s killer surge may have been, at least in part, airborne—is both disturbing and thought-provoking.