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Low-dose carbon monoxide helps reduce stress in big cities
Last reviewed: 01.07.2025
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Carbon monoxide (CO) is a tasteless, colorless, odorless gas that is highly toxic to humans. The main source of CO is vehicle exhaust and generators. Scientists have already dubbed it a "silent killer" because excessive inhalation of this substance causes poisoning of the nervous system and heart.
Scientists led by Professor Itzhak Schnell of the Department of Environmental Studies at Tel Aviv University (Israel) have discovered that low levels of CO have a narcotic effect that helps cope with harmful environmental factors in the urban environment, namely, high noise levels.
The study was published in the journal Environmental Monitoring and Assessment.
The discovery was made in the context of a larger project to study the impact of environmental factors on the human body. Professor Schnell and his colleagues wanted to determine how people living in urban environments experience stress in their daily lives. They asked 36 healthy people aged 20 to 40 to spend two days in Tel Aviv. During this time, the scientists monitored the impact of four different environmental stressors: thermal stress (heat and cold), noise pollution, carbon monoxide levels, and social stress (crowd exposure).
Participants reported the amount of time they felt tense and uncomfortable, and this data was then compared with data recorded by sensors that measured heart rate and pollution levels. Noise pollution was found to be the most significant cause of stress.
The most surprising result of this study was in the analysis of the CO data. Not only were the concentrations of carbon monoxide much lower than the scientists had expected (approximately 1-15 parts per million every half hour), but the presence of the gas in small quantities appeared to have a narcotic effect on the participants, leading to a reduction in stress caused by noise and crowds.
In other words, the results of the study showed that although urbanization increases the level of stress that a person is exposed to during the day, CO effectively mitigates this impact. The next stage of the study is to identify the mechanisms of environmental influence on more vulnerable groups of the population, such as children, the elderly and people with respiratory diseases.
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