According to FBI crime statistics, between 1961 and 1991, the rate of violent crime in the United States rose by nearly fourfold. But between 1991 and 2013, the crime rate dropped by more than half, to the lowest level since 1970.
Why? Was it “tough on crime” policing strategies? The rise of mass incarceration? The economy? Something else?
This was a key question for HIP’s Heath Impact Assessment on dignified and just policing, currently being conducted with several community organizations in Santa Ana, Calif. How do law enforcement strategies such as injunctions against gang activity impact health, including the rate of violent crime?
In “The Crimes of Lead,” published last year in Chemical & Engineering News, Lauren K. Wolf cites an abundance of peer-reviewed literature arguing that exposure to lead may be the key to the rapid fluctuation in crime rates over the last four-plus decades. In the 1970s, landmark environmental policies reduced children’s exposure to lead, which has been shown to cause brain damage that can lead to increased levels of aggression and violence:
Cars burning leaded gasoline spewed the heavy metal into the air until 1973, when the Environmental Protection Agency mandated the fuel’s gradual phaseout. Lead-based paint was banned from newly built homes in 1978. Because of these actions, children born in the mid- to late-1970s grew up with less lead in their bodies than children born earlier. As a result, economists argue, kids born in the ’70s reached adulthood in the ’90s with healthier brains and less of a penchant for violence.
Lead poisoning has also been blamed for the fall of the Roman Empire, notably by sociologist Seabury Colum Gilfillan, who first advanced his theory in the mid-1960s. (Gilfillan’s contemporary, geochemist Clair Cameron Patterson, agreed and was a key figure in the campaign to remove lead from gasoline in the U.S.) However, other academics have disputed this single-cause theory of Rome’s collapse. In fact, recent research suggests that the increase of lead levels in water because of lead-bearing pipes in Roman aqueducts was unlikely to have been truly harmful.
Critics of the lead poisoning theory point out that there were numerous political, social and economic forces that are just as likely to have contributed to Rome’s demise. To state the obvious, the collapse of a civilization is a complex matter.
And so is crime. Social factors play a role in crime rates: poverty, disinvestment in communities of color, systemized and institutionalized racism and discrimination, and other economic forces.
To me, the thought that a molecule could topple a civilization, or that its removal could revitalize it, seemed like too simple an explanation to be true. In public health, we’re used to the truth being complicated and sometimes not entirely knowable.
But as Wolf shows, the correlation between lead exposure and crime bears out even when adjusting for demographic and social factors, when looking at the phenomenon at the state, city and even neighborhood level, and in various countries. It holds up even in locations where the relationship between lead exposure and crime doesn’t follow the clear “inverted U” curve of the data from the U.S. In the end, the lead exposure theory for the rise and fall of violent crime in the U.S. seems entirely plausible, in fact probable.
It’s encouraging to see that simple policies to reduce lead contamination may have prevented millions of violent crimes. If that isn’t a positive health impact of a policy change, what is? And the data simply do not support the claim that the bulk of the reduction in crime was due to policing strategies or incarceration.
I still have questions. The crime rate per capita was still much lower in the 1960s than it is today, despite lower levels of lead exposure now than ever before. And since 2002, lead exposure no longer correlates so strictly with U.S. crime rates.
What are the current underlying causes of violent crime in our communities? How can policies continue to address the issue and accelerate the decline? As communities – and as researchers working with and within communities – we can proactively address these issues. No longer must we look back at the decline of Rome or the crime wave of the 1980s and 1990s and simply wonder what happened.