For several years, research really did suggest that houseplants might cleanse the air of certain pollutants. But now most scientists say that’s not right.
“It’s such an alluring and enticing idea,” Elliot Gall, a Portland State University professor, told me. “But the scientific literature shows that indoor houseplants—as would be typically implemented in a person’s home—do very little to clean the air.”
“My view is even harsher than that,” Michael Waring, an engineering professor at Drexel University, told me. “I do not think that houseplants clean the air.”
“A resounding ‘no,’” agreed Richard Corsi, a longtime air-pollution researcher, in an email. Houseplants do not clean the air “any more than an old pair of socks or baseball cap that I would hang on the wall.”
In the late 1980s, the NASA scientist Bill Wolverton investigated whether common houseplants could remove a certain type of air pollutant, called “volatile organic compounds,” or VOCs, from the air. VOCs are regularly released by common household products such as drywall, house paints, nail polish, shampoo, and almost anything with a scent. Their harmful effects can range from an itchy throat to nasopharyngeal cancer.
Unlike other types of air pollution, such as soot or particulate matter, VOCs can’t be filtered out of the air with a fine-grade filter. This means that they can build up in hermetically sealed environments … such as laboratories or spacecraft. The problem for NASA was obvious. So Wolverton, a former military scientist who began his career studying whether plants could break down Agent Orange, now examined whether houseplants could absorb VOCs.
His 1989 report announced a cheerful answer. Plants were “a promising, economical solution to indoor air pollution,” it declared. “If man is to move into closed environments, on Earth or in space, he must take along nature’s life support system.” The report—jointly funded by NASA and the Associated Landscape Contractors of America, a trade group—was picked up by the media. The idea gained even more currency in 1996, when Wolverton published How to Grow Fresh Air: 50 Houseplants That Purify Your Home or Office. (Wolverton did not respond to a request for comment.)
That study provides the scientific basis for almost all the plant-and-air-pollution content you see online. “I’ve seen it on so many pop internet sites—‘researchers from NASA’ is the common phrase you see,” Waring, the Drexel professor, said. He told me that there’s nothing especially wrong with Wolverton’s 1989 study. Its results “fall right in line with other stuff that’s been measured in the literature.”
Recently, Waring and his colleagues reanalyzed all 195 studies that have examined whether houseplants can filter the air. They found that some types of plants can remove higher amounts of VOCs than others. But once you factor in the effects of working in a large room, none of the plants are able to do much.
Waring told me to imagine a small office, 10 feet by 10 feet by eight feet. “You would have to put 1,000 plants in that office to have the same air-cleaning capacity of just changing over the air once per hour, which is the typical air-exchange rate in an office ventilation system,” he said. That’s 10 plants per square foot of floor space. Even if you chose the most effective type of VOC-filtering plant, you would still need one plant per square foot, Waring said.
Or as Waring (who owns 10 to 20 houseplants) recently put it in a presentation for the National Academies of Sciences, Engineering, and Medicine:
“Bringing plants in, bringing greenery in—it’s about having something near you that’s alive, that you’re caring for, that brings you joy and happiness,” she said. “And that affects your mood, whether or not it’s giving you more oxygen to breathe or something.”
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What Indoor Plants Clean the Air Best? None of Them. - The Atlantic: The science is clear: Indoor vegetation doesn’t significantly remove pollutants from the air.
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