Here are the basics on ozone, which has long been an issue for Colorado air quality. Jacy Marmaduke
We already know Fort Collins’ high ozone levels could contribute to health issues. But what about violent crime?
A new study led by Colorado State University researchers found a correlation between air pollution and the rate of violent crime, namely assault. The reasoning for the link isn’t yet understood, but the researchers said their findings suggest a policy reducing daily ozone levels and fine particle pollution by 10% could cut the costs of American crime by up to $1.4 billion a year.
The study is especially relevant for Fort Collins and Northern Colorado, where ozone levels have consistently failed to meet federal environmental standards.
“There’s emerging evidence that air pollution impacts cognitive behavior, labor productivity, and now we’re adding to that list with these implications for crime, which is another social cost,” said Jude Bayham, a CSU assistant professor of agricultural and resource economics who co-authored the study. “The implication is that the social costs might be higher than we previously thought.”
Bayham and his coauthors looked specifically at ozone, the smog-causing substance born when common pollutants react with sunlight, and fine particulate matter with a diameter of less than 2.5 micrometers — about 4% the diameter of a human hair. Fine particles can come from a range of sources, including vehicle emissions, fossil fuel burning and wildfires.
Researchers found a 10% bump in fine particulate matter was associated with a 0.14% increase in violent crimes per county per day. The same increase in ozone was associated with a 0.3% increase in violent crimes per county per day. Assaults almost single-handedly drove the increase connected to both types of pollution, according to the study, and the researchers found no link between air pollution and property crime. The effects on violent crime were immediate, meaning the study suggests air pollution has an effect on spontaneous acts of violence.
The other big takeaway: The correlation between air pollution and violent crime became obvious well below the federal standards for air pollution.
“We found the effect starts pretty immediately and goes up pretty quickly,” Bayham said.
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The effect of fine particles on violent crime shot up between zero and 15 micrograms per meter cubed — much lower than the EPA’s 24-hour limit of 35 micrograms per meter cubed — and leveled off after that. The effect of ozone on violent crime shot up between zero and 35 parts per billion and then started to decline. (That doesn’t mean that higher levels of ozone reduced violent crime, just that the effect of ozone on violent crime became less pronounced.)
The EPA’s 8-hour ozone standard is 70 parts per billion. The North Front Range, which includes Fort Collins, Greeley and the Denver metro area, is out of compliance with that standard as well as a more lax standard set in 2008 (75 ppb). The EPA judges ozone levels based on average concentrations across an 8-hour period, so the noncompliance means ozone monitoring stations in the region recorded 8-hour concentrations above 75 ppb at least four times in a year.
The CSU study involved analysis of three types of data spanning about 400 counties across the U.S.: daily air pollution data reported to the Environmental Protection Agency, daily crime data reported to the FBI and daily satellite imagery of wildfire smoke plumes mapped by the National Oceanic and Atmospheric Administration.
The researchers used an array of statistical methods to rule out confounding variables — factors that might have also contributed to a rise in crime. For example, hot weather is well known to contribute to aggression and drive up violent crime, and ozone concentrations tend to be higher on hot days. But the study found the relationship between air pollution and violent crime was present on top of the relationship between heat and violent crime.
Lower-income areas are also known to have higher levels of air pollution as well as higher crime rates. The researchers addressed that and other local impacts by zeroing in on the crime rate in each specific county on particular days of the week. So they wouldn’t compare Larimer County’s crime rate on Mondays in June to Denver County’s crime rate on Saturdays in December — they would compare Larimer County’s crime rate on a Monday in June to its crime rate on all the other Mondays in June.
As for why air pollution would incite violence, Bayham said that needs further study. There’s some evidence that short-term exposure to air pollution can elevate anxiety and aggression, but researchers still don’t understand exactly how. It’s possible that air pollution affects serotonin levels or other aspects of brain function.
“We’re documenting these correlations and associations, but we need to better understand the mechanisms,” Bayham said. “Those will suggest how people might engage in activities that might mitigate the risk.”
The study was published in the Journal of Environmental Economics and Management.
Bayham’s co-authors were:
- Jesse Burkhardt, agricultural and resource economics assistant professor at CSU
- Ander Wilson, statistics assistant professor at CSU
- Ellison Carter, civil and environmental engineering assistant professor at CSU
- Jesse D. Berman, environmental health sciences assistant professor at University of Minnesota
- Katelyn O’Dell, atmospheric sciences graduate assistant at CSU
- Bonne Ford, atmospheric sciences research scientist at CSU
- Emily V. Fischer atmospheric sciences associate professor at CSU
- Jeffrey R. Pierce, atmospheric sciences associate professor at CSU
Jacy Marmaduke covers government accountability for the Coloradoan. Follow her on Twitter @jacymarmaduke.
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