A team of researchers from the University of Iowa and the University of Colorado Boulder recently explored that question in a review article published in Nature Reviews Chemistry. The paper examines volatile methyl siloxanes (VMSs), human-made chemicals commonly used in products such as shampoos, conditioners, deodorants, cosmetics, and industrial materials.

Because VMS compounds evaporate easily, many enter the atmosphere after use. Once airborne, they can travel long distances before breaking down, allowing scientists to detect them in remote areas far from the cities and industries where they originated.

“Globally, society produces over 300,000 man made chemicals,” said Charles Stanier, adjunct professor of chemical and biochemical engineering at UI and co-author of the paper. “Many of these are released into the environment and can be found in trace quantities in air, water, and soil using modern lab techniques.”

However, Stanier notes scientists struggle to predict how these chemicals move and transform in the environment, which can affect where they ultimately end up and how long they persist. Their health and ecological impacts are often even less clear.

Recent advances in laboratory studies, field measurements, analytical techniques, and computer modeling have helped scientists build a clearer picture of their behavior. However, the paper makes a case for updated assessment of VMS atmospheric chemistry and environmental behavior.

While the co-authors have contributed dozens of original works to the literature on the atmospheric chemistry of siloxanes, the paper summarizes the state of the science - their work and others - for the scientific, regulatory, and industrial communities interested in this topic.

“Our work on the atmospheric chemistry of siloxanes contributes one focused piece to the broader effort to understand persistent chemicals in the environment,” Stanier said.

The research team includes from the University of Iowa, Stanier and Saeideh Mohammadi (chemical and biochemical engineering/IIHR — Hydroscience and Engineering), Christopher Brunet (civil and environmental engineering/IIHR), and Jeewani Meepage, Josie Welker and Elizabeth Stone (chemistry). Contributors from the University of Colorado, Boulder include Eleanor Browne and Hanalei Lewine (chemistry).

In related research with many of the same collaborators, the Stone group — led by first author Meepage — reported the most accurate field measurements to date of oxidized siloxanes in New York City. The work confirms key atmospheric behaviors previously known only from models and reveals new chemical signatures within this family of compounds.

These findings were published in ACS ES&T Air this month.