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Skip the Shampoo? Dirty Human Hair Neutralizes Ozone

But it's not all good—also produces formaldehyde and other irritants.

By Sarah Bates
Jun 26, 2008 5:00 AMNov 12, 2019 5:06 AM


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Don’t be too quick to judge the next time someone you know skips a shower—he or she may actually be clearing the air.

The dangerous pollutant ozone, it turns out, is destroyed by hair and body oils, an oddity revealed when researchers at Missouri University of Science and Technology compared washed and unwashed hair. Environmental engineer Glenn Morrison and physician Lakshmi Pandrangi found that dirty hair—generally awash in skin oil—consumed seven times more ozone on average than did clean hair. The explanation is strictly chemical: The oils covering our bodies contain double-bonded molecules, including triglycerides, fatty acids, and a substance called squalene, that latch onto the ozone (O3), neutralizing it before we breathe it in.

But what seems like a terrific natural defense system may have some drawbacks. The same reactions that reduce ozone also create by-products, including the respiratory irritants formaldehyde and 4-oxopentanal. Researchers have yet to determine how damaging those chemicals are in the small amounts produced.

While much has been done to learn about air pollution and the effects of smog, less is known about the importance of the “microenvironments” that surround our bodies. We spend about 90 percent of our time indoors, where chemical interactions between the air, human skin, and other things are not well known. Morrison says that even small changes, such as the use of hair products, can alter the air we breathe in critical ways. “Each home or office has its own unique smog event every day,” he says.

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