Deodorant Can Generate Air Pollution That Rivals Urban Smog

Modern personal care products are formulated using a variety of ingredients to mask body odor, prevent perspiration, moisturize, hold our hair in place, and fill our noses with fresh, pleasant fragrances.

Literally hundreds of compounds are used to manage these tasks. Not only are some of the substances themselves concerning from a health perspective, but even the less problematic ones could still react with substances in our environment to generate new pollutants with largely unknown toxicity.

A study led by researchers from École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland has detailed the emissions from the use of a handful of popular personal care products and the reactions they undergo in a typical indoor environment.

More than 200 different kinds of volatile organic compound (VOC) were identified at concentrations of several parts per million.

Though the vast majority of compounds can be regarded as benign, especially at low concentrations, some of the more notable classes of chemical quickly reacted to form secondary organic aerosols, the consequences of which aren't so easily dismissed as safe.

"Some molecules 'nucleate' – in other words, they form new particles that can coagulate into larger ultrafine particles that can effectively deposit into our lungs," says EPFL engineer Dusan Licina.

"In my opinion, we still don't fully understand the health effects of these pollutants, but they may be more harmful than we think, especially because they are applied close to our breathing zone. This is an area where new toxicological studies are needed."

Many modern homes and offices will have at least one or two sources of the oxygen molecule ozone (O₃), which is commonly emitted by printers and photocopiers, and ironically air purifiers. Even in places free of ozone-producing equipment, many outdoor pollutants will react in sunlight to generate ozone, which can then drift indoors through windows and ventilation systems.

Though superficially similar to the oxygen our bodies rely on for respiration, ozone's third oxygen atom makes it relatively unstable, allowing it to react easily with volatile organic compounds, like monoterpenes.

To determine the full extent of potential pollutants created by reactions between ozone and the VOCs in personal care products, Licina and his team purchased samples of a deodorant body spray, hand lotion, roll-on deodorant, perfume, and dry shampoo hair spray and conducted two different types of experiment.

One set of tests simply evaluated the emissions from each item applied to an individual standing in a simulated indoor environment, or a tissue left in the room for an hour. The second set of tests introduced ozone at a rate of around 35 to 40 parts per billion and measured the results of any reactions with emissions from each personal care product.

A literal 'smog' of particulates was created in all cases except one – the roll-on deodorant. Concerningly, the growth rate of the particles was considerably higher than what studies typically report for outdoor air quality in urban or remote environments.

Given growing concerns over the influence fine particles in our air can have on our health over surprisingly short periods, knowing we could generate similar kinds of pollution every time we do our hair or spray on a nice perfume ought to ring some alarm bells.

"I know this is difficult to hear, but we're going to have to reduce our reliance on these products or, if possible, replace them with more natural alternatives that contain fragrant compounds with low chemical reactivity," says Licina.

This research was published in Environmental Science & Technology Letters.