Crime statistics around the world are often linked to more obvious external factors. War, poverty, economic injustice - these categories are easy to pinpoint and usually socio-economic factors play a role. But, a peculiar area that is being linked to crime rate is one not ordinarily seen as a contributing factor: air pollution.

Groundbreaking research was conducted in a report by Harvard University scientist, Evan Herrnstadt and University of California Davis scientist, Erich Muehlegger in 2015 which chronicled over 2 million crimes in the Chicago-area over a period of twelve years. Looking at data that detailed everything from type of crime to which areas crimes took place in, the scientists also studied meteorological records to see which way the wind blew on a particular day. Ultimately, they concluded that air pollutants, with their irritating effect on the lungs played a major role in impulse control. The correlation specifically found that data was conclusive with violent crime -- think murder, aggravated or rape assaults. Correlation however should not be confused with causation, but researchers are continuing to study trends to understand the full depth of air pollution in our day to day lives.

Lead Exposure

When we look back in recent history, those who study environmental changes on human behavior almost always zero in on a specific key time: when murder rates spiked. Two important times this was acutely observed were during the 1930’s and again between 1960-1970. In both points in time, lead exposure in the environment was particularly high. Homes built prior to the 1978 U.S. ban in which subsequent use of lead-based paint came to an abrupt halt when it was discovered its pollutants were a major health concern among children. There was also a vast majority support of providing unleaded gasoline in communities as an alternative to gasoline that contained lead, especially since an increased number of cars on the road helped to distribute lead via wafting wind. Lead poisoning has for years demonstrated behavioral and academic problems among children, often leading to learning disabilities. Impulsive behavior soon followed which became for researchers, a breeding ground for violent crime. Crime rates among exposed children peaked in their youth and decreased when these children became adults.

One of the ways to combat this pressing issue is to approach it from an economic perspective. Society shares the brunt of crime with itself. In 2007, criminal activity caused an estimated $15 billion in economic loss. Among other factors, costs were related to police protection, correction facilities, and judicial activity. Environmental advocates noted to counter this would mean investing in programs that instead are meant to curb crime. Because crime costs far outweigh crime prevention measures, many would happily provide support if it meant for a safer community for families.

Downwinds & Increased Temperatures

As Herrnstadt and Muehlegger zeroed in on areas that were especially vulnerable to violent crime rates, they turned their attention to the growing number of cars on the interstate and their release of toxins into the air. Neighborhoods surrounding the interstate experience an uptick when winds blew toward these neighborhoods. Like fitting puzzle pieces together, the conclusion was that these areas saw a 2.2 percent increase in homicides, rape, battery, and assaults because of increased particulates. The meteorological records used in the study confirmed their theory that downwind directly contributed to the crime increase. In contrast, upwind areas experienced less crime. It’s worth noting both scientists agreed that a number of factors such as unreported crimes or inaccuracies in crime reporting could shift their findings, yet the general basis remains.

Another more or less obvious observation to crime rates and pollution are increased temperatures. From a physiological perspective, a fairly simple and easy to understand theory is that on warm days, humans seek cool air by opening windows and doors, thus leaving property more vulnerable to crime. In a more concrete explanation, temperature has a direct effect to aggression. Imagine your comfort level in an exceptionally hot room versus a moderately warm or cool room. Heart rates and blood pressure rise, leading to an overall loss of control over rational thinking; irritability climbs and so does unreasonable behavior. Warm air is much more difficult to breathe than cool air (think back to those nights of humidifiers in order to get a good night’s rest). On hot nights, sleeping becomes difficult, playing on the already irritated state of mind. Historical data supports this argument, with serious crimes being reported far more during the summer months than most other times of the year.

Could a warming planet signify an increase in crime? From these findings, it seems it could. Crime data has suggested that heat waves, regardless of season, illustrated increased crime. When this is coupled with other external factors such as economic welfare, the correlation is all the more stunning. Cities like Los Angeles, Fresno, and Pittsburgh still harbor the worst air to breathe in the U.S. thanks in part to their smog-induced environments. Areas such as this are worth closer scrutiny to further determine if the research study conducted holds its weight.