Chemicals in skin and hair products contribute to air pollution

Researchers are reporting that chemical emissions from personal care products are contributing to air pollution, according to a new study out of Boulder, Colorado. During rush hour, the magnitude of emissions from personal care products was found to be comparable to emissions from automobiles.

Study lead author Matthew Coggon is a CIRES scientist at the University of Colorado Boulder working in the NOAA Earth System Research Laboratory.

“We detected a pattern of emissions that coincides with human activity: people apply these products in the morning, leave their homes, and drive to work or school. So emissions spike during commuting hours,” said Coggon.

Decamethylcyclopentasiloxane (D5 Siloxane) belongs to a class of chemicals called volatile organic compounds (VOCs) which evaporate quickly. Once in the air, however, sunlight can trigger VOCs to react with nitrogen oxides and other compounds to form ozone and particulate matter.

The researchers measured levels of VOCs such as siloxane, which is commonly added to shampoo and lotion for a silky texture, as well as emissions of benzene and other chemicals emitted by vehicles. Measurements were conducted in 2015 and 2017 from the roof of NOAA’s Earth System Research Laboratory, and in 2016 from a mobile lab on the ground in Boulder.

“We were surveying the air, monitoring every species our instrument was sensitive to – about 150 compounds,” said Coggon. “We found a big peak in the data but we didn’t know what it was.”

Study co-author Patrick Veres suggested it may be siloxane. Because the siloxane emissions correlated with the benzene emissions from traffic, they expected to find it in vehicle exhaust.

When they established that siloxane was not present in vehicle exhaust, they discovered that the common denominator between benzene and siloxane was commuting. Both siloxane and benzene emissions peaked when people set out for their morning work commute, and then decreased during the day.

Because the skin care and hair products were not as potent at the end of the day, the evening peak of siloxane emissions was lower compared to the morning peak.

A recent study led by CIRES and NOAA’s Brian McDonald found that personal care products, household cleaners, paints, and pesticides produced around half of the VOC emissions in Los Angeles during the research period.

“This study provides further evidence that as transportation emissions of VOCs have declined, other sources of VOCs, including from personal care products, are emerging as important contributors to urban air pollution,” said McDonald.

“In this changing landscape, emissions from personal care products are becoming important,” said Coggon. “We all have a personal plume, from our cars and our personal care products. It’s likely that emissions from personal care product also affect the air quality in other cities besides Boulder and L.A. Our team wants to learn more about these understudied sources of pollution.”

The study is published in the journal Environmental Science and Technology.

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By Chrissy Sexton, Earth.com Staff Writer