As far back as 1989, when NASA scientist B.C. Wolverton produced a study on the topic, it has been understood that plants have the ability to remove harmful organic chemicals such as benzene, trichloroethylene, and formaldehyde from the air. “That’s the reason why humans are able to live on this planet, because plants have purified the air,” said Wolverton. “And we are using this ability of the plant in our pots” (via NASA). Much of this work happens below the surface of the soil; the study explains that plant roots and the microorganisms that live in the soil kill those harmful organic chemicals along with bacteria and viruses. Perhaps the most fascinating part is that plants can then turn those pollutants into healthy new cell tissue.
Even so, you’ll find conflicting information when you search for it. More recent studies have found that, while plants are beneficial, they are not always able to make a significant improvement in indoor air quality (via Breeze Technologies). Whether it’s the species of plant, the specific combination of chemicals and volatile organic compounds (VOC) in the air, or the light and moisture conditions within the home, results tend to be excessively varied. We must understand that though they help, they cannot be the sole cure. More effective solutions include better air circulation and ventilation and, where possible, removing whatever it is that is causing the low air quality in the first place.