reduce anxiety

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Car Exhaust
Okay, this one shocked us—and, to be clear, we absolutely are not recommending this—but it may explain why urbanites aren't as crazy as they could be. Researchers at Tel Aviv University found that carbon monoxide (CO)—a tasteless, odorless (and toxic) gas present in car exhaust—has a slightly "narcotic effect." In city centers where CO levels were higher than average (but apparently not a health concern), people felt less stressed without knowing why; it even helped offset the stress of noise pollution. (But, and we can't underscore this enough, CO is a silent killer.)