Exposure to air pollution, even imaginative, may lead to unethical behaviour such as crime and cheating, according to a study conducted on adults in India and the US.
The findings published in the journal Psychological Science suggest that this association may be due, at least in part, to increased anxiety.
"This research reveals that air pollution may have potential ethical costs that go beyond its well-known toll on health and the environment," said Jackson G Lu, behavioural scientist at Columbia Business School in the US.
"Our findings suggest that air pollution not only corrupts people's health, but also can contaminate their morality," said Lu.
Previous studies have indicated that exposure to air pollution elevates individuals' feelings of anxiety, which is known to correlate with a range of unethical behaviours.
In one study, the researchers examined air pollution and crime data for 9,360 US cities collected over a nine-year period.
The researchers found that cities with higher levels of air pollution also tended to have higher levels of crime.
In one of the experiments conducted with university students in the US, the researchers measured how often participants cheated in reporting the outcome of a die roll.
In the other experiment 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 did those who wrote about living in a clean location; they also expressed more anxiety in their writing, researchers said.
Since they could not randomly assign participants to physically experience different levels of air pollution, the researchers manipulated whether participants imagined experiencing air pollution.
In one experiment, 256 participants saw a photo featuring either a polluted scene or a clean scene. They imagined living in that location and reflected on how they would feel as they walked around and breathed the air.
On a supposedly unrelated task, they saw a set of cue words (eg sore, shoulder, sweat) and had to identify another word that was linked with each of the cue words (eg cold); each correct answer earned them USD 0.50.
Due to a supposed computer glitch, the correct answer popped up if the participants hovered their mouse over the answer box, which the researchers asked them not to do.
Unbeknownst to the participants, the researchers recorded how many times the participants peeked at the answer.
The results showed that participants who thought about living in a polluted area cheated more often than did those who thought about living in a clean area.
As the researchers hypothesised, anxiety level mediated the link between imagining exposure to air pollution and unethical behaviour.
Together, the archival and experimental findings suggest that exposure to air pollution, whether physical or mental, is linked with transgressive behaviour through increased levels of anxiety, researchers said.