Published on 01/14/09

Study identifies best air-purifying plants

By Sharon Dowdy
University of Georgia

Martha Stewart says houseplants add to a home’s décor. But they can also purify indoor air, say University of Georgia experts.

“This is an area that’s been largely ignored, and the health issues are potentially astronomical,” said Stanley Kays, a horticulturist with the UGA College of Agricultural and Environmental Sciences. “We spend as much as 90 percent of our time indoors breathing indoor air that often contains a diverse range of volatile organic compounds, many of which are toxic.”

House plants can absorb those VOCs. To determine the best air-purifying houseplants, Kays, CAES postdoctoral research associate D.S. Wang and CAES horticulturist Bodie Pennisi evaluated 32 plant species.

Best air-purifiers

Of the species tested, purple waffle plant (Hemigraphis alternata) best removed VOCs from the air. Other species with superior filtering abilities were English ivy, purple heart, foxtail fern and wax plant.

In the study, the plants were tested for their ability to remove benzene, toluene, octane, trichloroethylene and a-pinene, all considered toxic. Plant specimens were placed in sealed glass containers. The VOC levels within were monitored over a six-hour period.

Poor indoor air quality can trigger allergies and asthma and cause fatigue and headaches.

“More than 300 volatile organic compounds have been identified as indoor contaminants,” said Pennisi. “This doesn’t include dust and inorganic gases.”

Toxic compounds come from common sources

These compounds can come from carpet, wood panels, paint, people, pets and various other sources. Benzene and toluene come from newspapers, schoolbooks, electric shavers, portable CD players, liquid waxes and some adhesives.

VOCs also emanate from home electronic equipment, furniture, carpet and construction materials.

“Most of these compounds are readily absorbed into our bodies,” Pennisi said. “Bad indoor air can result in new house syndrome and sick building syndrome that can cause a diverse cross-section of ailments in those exposed.”

High levels found in homes tested

Before testing the plants, the researchers conducted tests for VOCs in three older, upper middle-class homes in Athens, Ga. Older homes are often more drafty than newer homes, which are built tighter to better insulate them.

“The results really shocked me,” Kays said. “All three homes had surprisingly high levels of organic compounds in their air. These were older homes. So if the levels are high there, then it’s probably widespread in newer homes.”

To reduce the VOC levels in your home, UGA researchers recommend adding a cross-section of plants, one per 100 square feet of living space. Using active charcoal filters in heating and air conditioning systems helps, too.

Sharon Dowdy is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.