9 November 2011

Narcotic effects of carbon monoxide keep city dwellers happy

by Kate Melville

Low levels of the gas carbon monoxide have a narcotic effect on city dwellers, say Tel Aviv University researchers, leading them to suggest that the pollutant is, in small doses, a boon to the well-being of urbanites. Their study examining urban stress and pollutants has been published in the journal Environmental Monitoring and Assessment.

Carbon monoxide (CO) is a tasteless, colorless and odorless gas most commonly found in the exhaust fumes of vehicles. A favorite for suicides, the gas has been dubbed the "silent killer" because excessive inhalation poisons the nervous system and cardiovascular system.

But Tel Aviv University's Itzhak Schnell says that low levels of the poisonous gas can have a narcotic effect. His claims are based upon findings from a wider project designed to study the impact of environmental stressors on the human body. Specifically, Schnell and his co-researchers wanted to measure how people living in an urban environment dealt with common stressors in their daily lives.

For the study, healthy test subjects travelled various routes through Tel Aviv to sites such as busy streets, restaurants, malls and markets, by public and private transportation, or by foot. The researchers monitored the impact of four different environmental stressors: thermal load, noise pollution, carbon monoxide levels, and social load (the impact of crowds). Data was taken from sensors that measured heart rate and pollutant levels.

The most surprising finding of the study, says Schnell, was in looking at levels of CO that the participants inhaled during their time in the city. Not only were the levels much lower than the researchers predicted - approximately 1-15 parts per million every half hour - but the presence of the gas appeared to have a narcotic effect on the participants, counteracting the stress caused by noise and crowd density.

The results, say Schnell, indicate that living in a major city might not have as negative a health impact as previously believed. "Though participants exhibited rising stress levels throughout the day, CO had a mitigating influence and extended [low-level] exposure to the chemical had no lasting effects."

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Source: Tel Aviv University