Pollution isn’t just about what’s coming out of our tailpipes. The products we keep under our sinks, in our bathrooms, and all around our homes could be just as detrimental to air quality, according to a new study led by a team of Boulder-based scientists.

The paper, released by the Cooperative Institute for Research in Environmental Sciences (CIRES)—a collaboration between the University of Colorado Boulder and National Oceanic and Atmospheric Administration (NOAA)—found that chemical products now likely contribute more to human-made sources of pollution than transportation in urban areas.

The study compared the emissions of volatile organic compounds (VOCs) from common household and industrial products with those from vehicle exhaust. VOCs are petroleum-based substances released both naturally by trees, grass, and from human-created sources like cars and consumer products. They’re found in a variety of items in our bathrooms and broom closets—from deodorant, shampoo, perfume, and cleaning materials, to printing inks, adhesives, paints, and pesticides. While many are used indoors, the particles easily migrate outside, where they combine with sunlight and other compounds in the air to form ground level ozone (a.k.a. smog) and small particulate matter, both known to seriously damage human health.

“On one hand, I think this is a good news story from the perspective of we knew in the past that transportation was a big source of air pollution, and we’ve made a lot of progress at controlling emissions from vehicles,” says Dr. Brian McDonald, a scientist at CIRES and the study’s lead author. “But as the transportation sector emissions for VOCs have come down a lot in the past four or five decades, other sources are becoming more and more important.”

While most people use a lot more gasoline than perfume, the study found that every gram of chemical product releases twice the VOCs as each gram of exhaust. Unlike vehicles, where catalytic converters—exhaust emissions control devices—help reduce the toxic pollutants released, VOCs from many chemical products head straight into the air. “There have been emission control systems in cars, whereas the VOCs in chemical products don’t have those controls.” McDonald says. “If you put paint on a wall, those VOCs are intended to evaporate, so a small amount of chemical product can have a large influence.”

Currently, there are no federal standards on VOCs from non-industrial, indoor chemical sources—meaning many of the products we use everyday are not subject to restrictions. While McDonald emphasizes that transportation is still a major factor for air quality, the research suggests that further regulations on household products may be necessary to combat dangerous pollution and protect human health. Globally, air pollution is the fifth leading health risk factor for death, as ground level ozone and respiratory irritants can lead to ailments such as lung cancer, heart problems, asthma, and stroke.

Denver is one of the worst U.S. cities for air pollution, so citizens can try to help reduce their contribution to the problem by being mindful of the products they’re using. “Try to use as little product as you need to get the task done,” McDonald says. Choosing fragrance-free products may also help curb VOC emissions. But just because you cut back on the cologne doesn’t mean you can quit carpooling to work.

“Transportation still remains an important source of urban air pollution,” McDonald says, “but clearly we need to be aware that there are other significant contributors.”