What If the Causes of Violent Crime Are Blowing in the Wind?

Serious crimes are more likely to occur in neighborhoods downwind of air pollution, according to a new study.
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Heat waves emanate from the exhaust pipe of a city transit bus as it passes an American flag hung on the Los Angeles County Hall of Justice in Los Angeles, California. (Photo: David McNew/Getty Images)

Heat waves emanate from the exhaust pipe of a city transit bus as it passes an American flag hung on the Los Angeles County Hall of Justice in Los Angeles, California. (Photo: David McNew/Getty Images)

The key to predicting where violent crime occurs may be to see which way the wind blows.

Neighborhoods downwind from tailpipe exhaust or industrial activity are more likely to experience higher rates of violent crime like homicide, rape, or assault, argue a team of researchers from the Harvard University Center for the Environment and the University of California–Davis in a new study published by the National Bureau of Economic Research.

Using data from more than two million serious crimes reported to the Chicago Police Department between 2001 and 2012, the researchers compared crimes on opposite sides of five major interstates throughout the city, taking note of which way the wind was blowing at the time of the delinquency. For each crime, they also noted temperature, precipitation, wind speed, and wind direction using the National Climatic Data Center, and measured ambient pollution levels using data from the Environmental Protection Agency.

While property crimes—burglary, larceny, arson, and grand theft auto—seemed unaffected by pollution, violent crimes—homicide, rape, robbery, assault, battery—were 2.2 percent higher in neighborhoods downwind of any air pollution.

Violent crimes were 2.2 percent higher in neighborhoods downwind of any air pollution.

The researchers claim their work provides the "first quasi-experimental evidence that air pollution causally affects violent criminal activity." The external costs of air pollution may be much higher than previously thought, they note, suggesting that the costs of pollution-related crime may reach as high as $100-200 million each year. If the relationship between violence and pollution is a causal one, as the study suggests, their findings offer a powerful incentive to clean up air pollution throughout major cities nationwide.

The researchers found that crime was often driven by the presence of nitrous oxides, a group of chemical compounds and air pollutants emitted primarily by cars, industrial power plant boilers, iron and steel mills, and petroleum refineries. When particulate matter containing pollutants like ozone reaches the brain, these pollutants can interact with the body's brain chemistry directly by reacting with the body to create toxins that affect the central nervous system. Psychologically speaking, air pollution can also trigger pain and discomfort, which can in turn lead to aggressive behavior.

This isn't the first study to link pollution with crime:

  • Violent criminals may have been exposed to heavy amounts of lead as children, and could in turn have higher levels of lead in their blood, according to a 2007 working paper published by the National Bureau of Economic Research. Childhood lead exposure is often associated with behavioral and cognitive traits linked to criminal tendencies, like low IQ; brain damage; ADHD; and aggressive, hyperactive, and impulsive behaviors. Lead exposure can also cause irreversible effects on the central nervous system and developing brain. Before lead was removed from gasoline in the late 1970s thanks to the Clean Air Act, gasoline was responsible for most of the lead found in the air, dust, and dirt around cities. Children who were born or who grew up in the '70s and '80s with unleaded gasoline, however, are responsible for a 56 percent drop in violent crime between 1992 and 2002. According to the study, crime rates should continue to fall by 2020, the year in which all adults in their 20s and 30s will have grown up without any exposure to lead in gasoline at all.
  • In the inner city, access to nature's spoils may be the best way to reduce crime. According to a new study published in BioScience, urban neighborhoods in closer proximity to nature feel more cohesive as a community. Being able to view some sort of natural landscape from the comforts of the home, the quality of the natural landscape within a city, and the amount of time spent in nature all create the perceptions of a more united neighborhood. When residents feel more tight-knit as a whole, the study states, they become less likely to engage in criminal behavior.
  • Sufferers of chronic psychosocial stress—a sense of continual distress resulting from repeated exposure to a social stressor like poverty or abuse—may be more vulnerable to environmental chemicals. According to a 2014 study of social stressors and air pollution from neighborhoods across New York City, the tolls of psychosocial stress—including its wear and tear on the body's immune, endocrine, and metabolic systems—render the body more sensitive to pollutants like lead.
  • High ozone levels—an indication of smog—correlates with increased rates of family disturbances, according to a 1985 study of air pollution, weather, and violent crime published in the Journal of Personality and Social Psychology. The most violent altercations, according to the study, occurred on warmer days versus cooler ones. When studying air pollution, the social and psychological costs of violent crime also should be taken into account, the study's authors argue.
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