_The Dirt on Cleaning Products

Some of the same chemical reactions that occur in the atmosphere from smog and ozone are taking place in your house while you clean.

_Michael Waring

Waring is an associate professor and associate department head for undergraduate programs and director of the Architectural Engineering Program in the College of Engineering.

Many cleaning products and air fresheners leave behind a sweet or citrus-y fragrance, but don’t be fooled by that “clean” smell. Michael Waring’s research examines the byproducts these pleasant-smelling compounds are adding to the air while we use them to remove germs and odors.


Secondary organic aerosols are a by-product of ozone reactions with the chemicals in cleaners.

Secondary organic aerosols (SOAs) are microscopic particles created when ozone reacts with volatile organic gases such as limonene — the chemical name for the smell of orange — or its cousin pinene, which produces the smell of pine trees. Outdoors, this reaction happens all the time. It drives the formation of much of the atmospheric organic aerosol present in our environment. And in population-dense urban areas — where enough suspended particles can be amassed — it contributes to the formation of smog.

While a large amount of aerosols that exist in the Earth’s atmosphere are naturally occurring, much is produced as a result of industrialization and studies have linked exposure to outdoor aerosols generally to poor health outcomes.

Few researchers, however, have considered the formation of SOAs in our indoor environments.

“SOAs can come from ozone reactions with numerous sources, especially with compounds called terpenes that produce the scents we associate with cleaners, pine, lavender and oranges,” he says. “Limonene….is a very popular scent for cleaning products, so we’re taking a closer look at how it reacts indoors, where people are using it in high concentrations.”

Waring and his team used an air-testing chamber specifically designed to study the reactive behavior of air in an indoor environment. With it, they were able to simulate limonene being added to the environment in pulses — the way it would be introduced indoors when spraying a limonene-containing cleaning product.

“Our findings show a significant enough range of SOA formation to warrant more in-depth public health studies,” says Waring.

Waring recommends using unscented cleaners and opening windows while cleaning as ways to reduce indoor aerosol formation. Even though open windows bring in more ozone from outside, the reduction in the indoor limonene concentration and SOA formation strength more than make up for it.