Houseplants Zap Indoor Ozone

New study of houseplants and ozone finds they remove lung-damaging chemicals from your air.

September 9, 2009

A clipping or seedling from a neighbor could become a free air cleaner for your home.

RODALE NEWS, EMMAUS, PA—If you wan to keep your indoor air clean, houseplants are the way to go. Back in the 1980s, NASA scientists discovered that indoor houseplants were effective room air purifiers, removing an array of hazardous volatile organic compounds (VOCs), which are emitted from paints as they dry and from the glues in furniture, cabinetry, and flooring. According to a new study published in the American Society of Horticultural Science's journal HortTechnology, those same indoor houseplants eliminate another health hazard, indoor ozone, which can trigger chronic respiratory problems and skin irritation.


THE DETAILS: Snake plants, spider plants, and golden pothos were selected for the study of houseplants and ozone because of their ability to remove hazardous indoor air pollutants. The plants were placed in chambers, into which the researchers pumped ozone at concentrations of 200 parts per billion (ppb). Then they measured how long it took for the ozone concentrations to drop to less than 5 ppb in those chambers, as well as in a separate chamber that had no plants, and repeated the experiment three times over the course of two months. All the chambers with plants reached the 5 ppb mark faster than the empty chamber, but the golden pothos chamber reached it first, followed by the ones containing the snake plant and the spider plant.

WHAT IT MEANS: When most people think about ozone, they think about the stuff outside that fills the air on hot, humid, hazy summer days, and the U.S. Environmental Protection Agency notes that levels of 110 ppb are high enough to lead to a spike in respiratory-related visits to emergency rooms. But that outdoor ozone doesn't always stay outside. It gets blown indoors, where indoor ozone concentrations can be nearly 80 percent as high as the levels outdoors. Ozone is also generated indoors by electronic equipment; one study found that laser printers can emit 30 ppb of ozone as they're printing documents. And ozone can be formed inside your home when you use paints or finishes containing VOCs, which create ozone as they mix with oxygen and sunlight. Indoor ozone can account for as much as 60 percent of your daily ozone exposure, according to a 2006 study published in Environmental Health Perspectives.

Fill your home with houseplants, and ozone levels will drop. Be mindful of these few tips:

• Bigger is better. "The more leaf area you have, the more detoxification takes place," says Dennis R. Decoteau, PhD, professor of horticulture and plant ecosystem health at Pennsylvania State University and one of the study's authors. Their houseplants and ozone study didn't compare the mitigating effects of plants by size, but he says they used plants that were the size of the average houseplant and fit into pots roughly 9" in diameter.

• Go with your personal preference. Decoteau notes that although golden pothos worked the fastest at removing ozone, the differences between it and the other plants were fairly small. Any of the three types will cut the ozone in your home to below-hazardous levels.

• Don't pay for your plants. Rather than shell out money for a houseplant at a nursery (where it may have been sprayed with pesticides), ask friends for clippings of their houseplants. Our Nickel Pincher, Jean Nick, offers advice on transplanting houseplant clippings.

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