Violence Is in the Air

Violence Is in the Air

A new study shows that the rate of violent crime increases with the level of smog.


Foul air isn’t just harming people’s health; it’s causing more people to harm one another. In a new study published in the Journal of Environmental Economics and Management, researchers at Colorado State and University of Minnesota found that the rate of violent crime increases with the level of pollution.

When it comes to air pollution, said Jude Bayham, one of the study’s co-authors, “We’ve known that there are negative health consequences,” but by looking at violence from a public health standpoint, “we’re trying to point out here is that this is something else that is a negative impact of bad air quality. So yes, we can tack it onto the list of social costs.”

The study tracked ozone pollution and PM2.5 (particulate matter up to 2.5 microns in diameter) in 397 counties in 35 states across the United States—covering about 92 million people—and showed that a spike of 10 micrograms per cubic meter of particulate matter is associated with a 1.4 percent increase in violent crime, mostly in the form of physical assault. A similar rise in violence was seen with elevated ozone levels.

The researchers do not suggest that air pollution is the determining factor for the rate of violent crime, but they draw connections that help make the case for holistic environmental policies. The fact that violent crime ticked down on days with better air quality demonstrates not only a direct link between air quality and violent behavior but also that even short-term fluctuations in ambient pollution can make a difference. Since even short-term air quality changes affect behavior, the study concludes that “policies that reduce pollution concentrations should reduce violent crime.”

This study builds on previous work that suggests a correlation between air pollution and violence. A 2015 National Bureau of Economic Research (NBER) study linked Chicago’s air quality and the prevalence of violent crime by tracking crime and pollution data over a 12-year period on several major interstates. For the local communities adjacent to the highways, the researchers compared crime statistics on the days the wind was blowing in their direction versus the days that it blew away from the residents. When pollution swept into the community, violent crime rose by 2.2 percentage points—even after controlling for economic background and other factors. The correlation was detected only for violent crimes (not property crimes, such as theft), reaffirming the link between pollution and aggression.

Erich Muehlegger, a co-author of the NBER paper, told The Nation that the primary harmful impact of air pollution is related to physical health problems like asthma and respiratory disease, but analyzing the relationship between social problems and pollution helps communities think “about the environmental impacts of pollution more broadly than simply, those things might make us sick if we’re exposed to them. But rather, this might affect our behavior, this might affect our cognition, in lots of ways that might spill over to lots of decisions that we make.”

Mapping pollution patterns over violence data can also bolster community-led environmental justice initiatives—such as a campaign to shut down a smog-belching oil refinery or waste incinerator next to a low-income neighborhood. The connection between cleaner air and improved social welfare parallels other emerging research, linking the expansion of neighborhood green space, such as parks, with improved public safety.

“The research on the adverse social impacts of air pollution really adds to the strength of the argument for reducing emissions quickly and substantially,” said Bill Magavern, the policy director for the Coalition for Clean Air. His organization has championed legislation that targets disadvantaged communities with investments in reducing greenhouse gas emissions, conversion to electric vehicles, and limiting diesel pollution exposure.

The physiological mechanisms by which environmental circumstances increase violence are not completely understood, but there are a few theories: First, air pollutants like ozone might have a direct neurological effect, leading to, for example, heightened aggression or impulsivity. Or perhaps poor air quality makes it hard to breathe, and the lack of oxygen impairs cognition. In addition, the physical irritation triggered by pollution can induce aggravation and anxiety. On a day-to-day basis, the cumulative damage of respiratory irritants could be a chronic source of frustration and oppression, the most extreme manifestation of which might be violent behavior. Similarly, intense heat is associated with higher violent crime—another grim side effect of global warming.

The research on the social effects of air pollution echoes previous studies on the behavioral impacts of air pollution on worker productivity. Research on workers on farms and in manufacturing and call-center workplaces indicates a clear link between air pollution at a work site and performance on the job. Conversely, researchers concluded, limiting air pollution through regulation could boost productivity; a reduction in the ozone standard by 10 parts per billion would save $700 million in labor costs in the farming sector, according to research by Columbia professor Matthew Neidell.

The stakes are even higher for communities tainted by lead poisoning, which has historically occurred through exposure to indoor lead paint or leaded gasoline. Studies on long-term lead exposure have shown that high childhood blood lead levels correlate with not just cognitive impairment and attention deficit-hyperactivity disorder, but also violent criminality in adulthood. A recent study by University of Minnesota researchers concluded that childhood lead exposure increased the risk of later becoming either a victim or perpetrator of gun violence. (Widespread evidence of long-term social harms of lead poisoning have spurred efforts to screen at-risk populations, remediate properties with lead-based paint, and mitigate lead contamination in drinking water.)

Although the study on county-level air pollution and crime did not parse the data specifically by racial or ethnic subgroups, environmental justice groups have highlighted the racial and socioeconomic disparities that intersect with dirty air. Black and Latinx children, for example, are disproportionately prone to asthma. In another study of Michigan schools, children’s exposure to air pollution in and around school buildings is associated with lower performance on standardized tests, and black, Latinx, and poor kids are disproportionately enrolled in the worst-polluted schools.

Lubna Ahmed of WE ACT for Environmental Justice argues that research that ties people’s day-to-day circumstances with changes in the environment can be empowering if it informs a community’s analysis of power and inequality in marginalized communities. When WE ACT campaigns against air pollution and toxic dumping in New York City’s poor communities of color, she said, the group is “shifting this narrative that ‘Oh, these are poor communities that can’t help themselves,’ [and instead] recognizing that these communities are in this position because of…the way that infrastructure was set.”

In distressed neighborhoods burdened by pollution, Ahmed added, it is vital for the public to realize that “this is structural racism. This is something that is very intentional much of time.”

Manuel Pastor, director of the Program for Environmental and Regional Equity at the University of Southern California, says that the studies linking pollution and violence are important, but that we need to move toward community action: “It’s great for one more study to come out, but I think it’s time for us to begin to develop the kinds of tools that will identify these problems before they occur.… It becomes a question of what’s the kind of community organizing and power shifting that needs to take place for these issues to come to the fore?”

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