Dr. B.C. Wolverton is an environmental consultant and retired NASA scientist. In his book, How To Grow Fresh Air, he describes the way houseplants, when used strategically, can filter toxins from the air in your home. "Our idea is to let plants be the lungs of a building, like the tropical rainforests are the lungs of the Earth," says Wolverton. His firm is developing greenhouse window boxes designed to pump filtered air into a room and has designed indoor ecology gardens in Tokyo, Japan.
High levels of synthetic chemicals can impact astronauts aboard space stations, so Wolverton initially began investigating plants as potential air purifiers in microgravity environments while at NASA. Since most houseplants evolved under the damp canopy of the rainforest, they developed an ability to suppress air-borne molds and microbes. Wolverton was able to demonstrate that these plants can also break apart the chemicals most commonly released by plastics and synthetic household products. Many volatile organic compounds in homes and schools have been linked to cancer, neurological disorders, and sick building syndrome.
Scientist Gerard Heyenga currently works on a similar project at NASA. He recommends selecting houseplants that are robust and easy to maintain. "Plants like ferns and ivy are good air filters," he says, "and they also show clear signs when they need to be watered."
Cheryle Yednak, a gardener in Santa Cruz, California, suggests the peace lily, a plant Wolverton says targets ethyl and methyl alcohol as well as acetone. "The peace lily fits most houses well because it can grow in a dark corner, and when exposed to bright, indirect light, it will bloom."
For those with gardening experience, Wolverton recommends plants from the palm and fern families. He found that the Boston fern targets formaldehyde -- a chemical used to preserve carpeting, upholstery fabrics, and the foam in mattresses and couch stuffing. A plant called the lady palm removes less formaldehyde but filters more ammonia than any other houseplant tested.
"Spider plants are also excellent," says Wolverton, "because they target benzene, the chemical released from house paint." To diminish the levels of benzene, he recommends opening a window to increase air circulation and then moving in several spider plants. For an average 12-foot-square room with standard levels of chemical toxins, he says two or three healthy plants will do the job.
"Plants need to be placed where you spend the most time breathing," says Wolverton. "On the nightstand next to the bed or perhaps on either side of your favorite chair." He says people will also benefit from placing plants around their desk at work, where air is often recirculated through dusty ventilation systems.
A Washington State University study found that houseplants reduce stress and help people relax. Plants also have been associated with increased employee productivity and hospital patients' ability to tolerate pain and physical discomfort.
Wolverton says plants are destined to become the indoor air technology of the future. He predicts that rooftop greenhouses will one day adorn apartment complexes and that indoor gardens will become a staple of the building industry. "Houseplants are so important," says Wolverton. "Not only do they target the invisible chemicals right under your nose, they also increase the overall quality of your life."
Later this year Wolverton's firm plans to market a patented UV lamp planter. The soil-free device uses pebbles, activated carbon, and zeolite to wick water to the plant. Wolverton says it has been shown to increase a plant's filtration capacity by nearly 100 times.