Breathing in polluted air makes us more likely to commit crimes and cheat, new research shows.
Scientists suggest this is because exposure to pollution makes us more anxious, which is known to trigger unethical behaviour.
Nearly 40 million people in the UK live in highly polluted areas, while this number is as high as 142 million in the United States, and the researchers suggest air pollutants may drive up crime rates in these regions.
Researchers at Columbia Business School in New York examined air pollution and crime data for 9,360 American cities collected over a nine-year period.
Air pollution data included information about six major pollutants and the crime data accounted for seven types of major offence, including murder and robbery.
The major pollutants were particulate matter, carbon monoxide, nitrogen dioxide, sulfur dioxide, ground-level ozone and lead.
The study showed cities with higher levels of pollution tended to have higher levels of crime.
This was even true after accounting for other potential factors, including total population, number of law enforcement employees, race distribution and poverty and unemployment rates.
Lead author of the study Dr Jackson Lu said: ‘This research reveals that air pollution may have potential ethical costs that go beyond its well-known toll on health and the environment.
‘This is important because air pollution is a serious global issue that affects billions of people – even in the United States, about 142 million people still reside in counties with dangerously polluted air.’
After the first series of experiments, the scientists set out to find a direct link between pollution and behaviour by asking people to ‘imagine’ air pollution.
In one, 256 participants saw a photo featuring either a polluted scene or a clean scene and imagined living there and how they would feel as they walked around and breathed the air.
On a supposedly unrelated task, they saw a set of cue words – such as sore, shoulder, sweat – and had to identify another word linked with each cue word, e.g., cold and each correct answer earned them $0.50.
Due to an intentional computer ‘glitch’, the correct answer popped up if participants hovered their mouse over the answer box, which the researchers asked them not to do.
The researchers then secretly recorded how many times the participants peeked at the answer.
Results showed participants who thought about living in a polluted area cheated more often than those who thought about living in a clean area.
In two additional experiments, participants saw photos of either polluted or clean scenes taken in the exact same locations in Beijing.
They then wrote about what it would be like to live there, before independent coders rated the essays according to how much anxiety participants expressed.
In one experiment conducted with American university students, researchers measured how often participants cheated in reporting the outcome of a die roll.
In another with adults in India, they measured participants’ willingness to use unethical negotiation strategies.
Participants who wrote about living in a polluted location engaged in more unethical behaviour than those who wrote about living in a clean location.
They also expressed more anxiety in their writing.
Mr Lu, a PhD candidate, added: ‘Our findings suggest that air pollution not only corrupts people’s health, but also can contaminate their morality.’
The study was published in the journal Psychological Science.