Stop Trying to Make Air-Purifying Plants Happen

The benefits of indoor plants are well-researched and comprehensive, but popular culture is desperate to give us even more reasons to be plant people. At the top of the list is the tantalizing-but-misguided idea that greenery has an inherent power to make your home’s air cleaner and better to breathe.

If you’ve studied science in school, you probably know that plants benefit everyone’s well-being by converting carbon dioxide into the oxygen we breathe. But in the late 1980s, while studying ways to purify air in space stations, NASA  discovered that plants may not just provide a literal breath of fresh air for the human body — common indoor plants actually had the potential to purify that same air of the cancer-causing toxins formaldehyde and benzene.

Over the course of a few decades, as wellness culture rose to popularity, the now-infamous NASA study became the backbone of another trend; Plants aren’t just accessories to decorate the home or even improve your mental health, advertisers told us, they could also make your life better in a more tangible way by purifying your air. The NASA study spurred advertising and media to spread the gospel that plants could help you breathe, they could help you sleep, and best-case scenario, they could even help you live longer. 

Turns out, the need to resuscitate a dying trend played a big role in plants’ pivot to wellness essentials. Lisa White, director of lifestyle and interiors at WGSN and former editor of Bloom Magazine, says air-purifying plants first hit her radar around 2009 after she listened to a TED talk called “How to Grow Fresh Air.”

“The research was very compelling and the plant industry picked up on it,” White says. “They were particularly pleased that Sansevieria, which had become unpopular, was touted as beneficial to clean air.”

The plant industry continued promoting Sansevieria, colloquially called Mother-In-Law’s Tongue, as a wellness plant, which helped sales until the 1970s trend took hold and consumers wanted the plant simply for its aesthetics. But the plants-as-wellness trend remains, and it’s only become more popular during the pandemic. 

“People are hibernated in closed houses, sealed off from the outside world, and the idea of plants coming in and literally breathing a breath of fresh air into homes is a compelling one,” White says. WGSN recently released a data-based Trend Curve Report on Plant Parents that shows just how much the plant trend has boomed during the pandemic. Wellness is a key factor people are drawn to plants, but right now,  it’s about emotional wellness in particular — White says there’s been more than an 80 percent spike in “plants” and “happiness” tags on social media since 2018.

The emotional boost provided by plants is probably their most meaningful health property, according to Stuart Strand, research professor emeritus of civil and environmental engineering at the University of Washington. To learn how effectively houseplants could actually purify the air in a person’s home, Strand reviewed 20 published articles with data measuring the effects of different houseplants on the degradation of common air pollutants. The results, he found, were both inconsistent and inconclusive. 

All the studies he reviewed tested plants’ abilities to consume very high concentrations of pollutants — far more than you’d find in a typical home’s air. “That causes bacteria in the soil to act differently than they would in the home to consume these pollutants,” he says.

What, exactly, does that mean for all the plants you have at home? According to Robert Eitches, an allergist based in Los Angeles, pretty much every home has the NASA-studied toxins in the air to some degree; formaldehyde, for example, is commonly released from paint, drywall, particleboard, and plywood. And, in theory, plants could play a minuscule role in purifying the home environment of these harmful chemicals, but how that plays out in your home probably won’t have a drastic impact on your health. 

Strand agrees. If you measured these toxin-uptake rates at lower concentrations — which he says is difficult and expensive, part of why existing studies haven’t done it — you probably wouldn’t see any effect. “Plants are beautiful and an important part of psychological well-being, but I don’t think they do anything for the health of the home air,” he says. “None of the studies agree on which plants do this and how many you would need.”

Plants also won’t appreciably increase the oxygen in your house, either — Eitches says you’d need one plant per square foot in your home for a meaningful effect, which obviously isn’t practical.

If you’re not careful, plants can even disrupt your health. For example, if you overwater their soil; Eitches says that excess moisture in your home could attract dust mites, which are known to exacerbate asthma, allergies, and other respiratory conditions. You’d be better off with a HEPA air filter (ideally, an option with a carbon filter). “Plants are green and beautiful and make you smile, and an air filter won’t necessarily make you feel alive in that way, but it would clean the air far better,” he says.

All this begs the question: If the average house plant doesn’t actually clean your air, and caring for them improperly can actually make things worse, why are we so fixated on the idea that plants have some sort of cleansing property?

“We want to care for plants; doing so gives us hope and purpose right now,” White says. “But we also want to believe that plants care for us.”