Carbon monoxide in cities could actually be drugging residents into placidity, according to Israeli scientists.
Professor Itzhak Schnell of Tel Aviv University says his research indicates that low levels of the poisonous gas can have a narcotic effect. And this, he says, helps citydwellers cope with other urban stresses, such as noise levels.
The discovery was made as part of a wider project designed to study the impact of environmental stressors on the human body. Most environmental observation stations are to be found outside city centers, and Professor Schnell and his fellow researchers wanted to measure how people living in an urban environment confronted stressors in their daily lives.
They asked 36 healthy individuals between the ages of 20 to 40 to spend two days in Tel Aviv, Israel's busiest city. These peopele traveled various routes to sites such as busy streets, restaurants, malls and markets, by public and private transportation or by foot.
Meanwhile, researchers monitored the impact of heat and cold, noise pollution, carbon monoxide levels, and social load, or the impact of crowds.
The participants reported to what extent their experiences were stressful, and this was compared with sensor data that measured heart rate and pollutant levels. Noise pollution emerged as the biggest source of stress.
But the most surprising findings related to the levels of CO that the participants inhaled during their time in the city. Not only were these much lower than predicted — around 1-15 parts per million every half hour — but the gas appeared to have a narcotic effect on the participants, counteracting the stress caused by noise and crowd density.
This, says Professor Schnell, shows that living in a major city might not be as bad for the health as previously thought. Though participants exhibited rising stress levels throughout the day, CO had a mitigating influence - and extended exposure to the chemical had no lasting effects, he says.