'Lead Hypothesis': The city that was accused of being a 'factory' of murderers

The United States in the 1970s not only experienced a cultural boom, but also had to confront a phenomenon that has been the subject of study for decades: the proliferation of serial killers. (Read more: The incredible artifacts recovered from the Titanic: They're kept in a secret location.)

Throughout that period, names like Ted Bundy, Randy Woodfield, and Gary Ridgway made headlines for their heinous crimes. However, one often overlooked detail is that, in addition to the cases that made them famous, they are all linked to the city of Tacoma, Washington.

This area in the northwestern United States experienced a kind of "golden age" of mass murderers, which some experts associate with environmental conditions, particularly lead contamination.

Writer Caroline Fraser puts forward this theory in her book "Murderland," in which she points out that nearby smelters, which spewed plumes of pollutants into the air , including arsenic and cadmium, may have fueled this wave of terror. This postulate is better known as the "lead hypothesis."

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'More lead, more crime'

The argument argues that while there were factories of this type across the country at the time, the one in Tacoma was located right in the center of the city , so the dust it emitted fell into yards, onto the streets, and spread beyond. This layer, which left a metallic taste on the tongue, not only resulted in environmental consequences, but also social ones.

"In the 1950s and 1960s, geochemist Clair Patterson showed that lead exposure caused what he called 'loss of mental acuity.' But the effects of lead are wide-ranging; in addition to intelligence, it can affect personality. Many studies link lead exposure to a particular type of damage to the frontal cortex that leads to increased aggression," the expert explained in an interview with 'Time'.

But what do Bundy and the others have to do with Tacoma?

According to Fraser's research, Ted Bundy grew up in the shadow of the copper smelter in this northeastern area. Gary Ridgway and Israel Keyes also lived nearby.

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And, in fact, the list is much longer. Although they didn't actually reside in this area, murderers like Charles Manson and Richard Ramirez had contact with lead contamination. The former spent 10 years in a nearby prison, where lead seeped into the soil; while the latter grew up next to another smelter in El Paso, Texas.

"Certainly, by Ramirez's time [in the mid-1980s], people were asking, 'What the hell is going on here?' I'm surprised now that no one asked why. No one was looking at the overall pattern and asking, 'Are there more killers than before? Is there something about the Pacific Northwest?' The FBI was presenting itself as the experts, but it didn't explain the phenomenon. Serial killers have always been with us in some form, but certainly not in those numbers," she concluded.

The plant closed its doors for good in 1983 , and the last vestiges of the industry disappeared in 1993 when its chimney was demolished.

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