Do a web search on air purification by plants and you’ll find hundreds of articles on the subject. There are some unreliable sources such as home decor magazines and trendy blogs, but also more serious media (such as the Laidback Gardener blog!) that have written about the subject. They often give lists of the best air filtering plants. I got caught up in this myself. I never really asked myself whether or not plants purify the air because it just seemed so obviously true! Today, I must unfortunately announce to you that it is not actually the case, at least not as much as we thought.
Ground Control to NASA? What Seems to Be the Problem?
It all started with a NASA study published in 1989, in collaboration with Associated Landscape Contractors of America: Interior Landscape Plants for Indoor Air Pollution Abatement. These compounds are released from many products and materials found in our homes, such as paint and certain cosmetics. NASA astronauts, working in a restricted environment, could be exposed to these VOCs, hence this study.
What the study shows is that some plants have the ability to clean the air of VOCs. After the study was released, the media spread the good news: plants filter air! So what’s the problem, man?
To start with, the study was conducted with plants placed in Plexiglas cubes of approximately 15 and 30 cubic feet (0.4 and 0.8 m3). A small room of 8’x8’x8′ (2.5m x 2.5m x 2.5m) has a volume of 512 cubic feet (15.625m3). With these figures, one would need between 17 and 34 houseplants to purify the air. But an apartment or a house is not a Plexiglas cube and therefore these figures don’t even apply. To date, I’m not aware of any study that looks at the filtering effect of plants in the context of a normal residence. (I see some of you are still thinking about how to get 40 plants into your bedroom.)
Another part of the study showed that roots and soil microorganisms were the most effective in filtering VOCs. The air was forced through activated charcoal in which plants were growing. Again, this has nothing to do with the homes you and I live in! And, let’s not forget that only a few pollutants were tested in the NASA study. What about the others?
How Does It Work?
Now I’m aware that my houseplants won’t replace an air purification system, but I’m still curious as to how plants transform these compounds. Well, they can absorb VOCs through their leaves and transport them to their roots where microorganisms break them down and convert them into sugars, oxygen and even plant matter!
Real Benefits of Houseplants
But don’t get rid of all your houseplants just yet! They still have well-documented benefits for humans. For example, working with plants reduces stress levels and can relieve people suffering from depression and anxiety. Their mere presence in our environment can improve our attention span. In addition, one study showed that the presence of plants could help us heal faster after surgery. Other studies have found that plants increase productivity and creativity in the workplace.
Which Plants to Choose?
Although NASA has compiled a list of plants that effectively purify the air, all plants have this ability. The best plants for our health are those that are healthy themselves. Choose plants that will grow well in your home. Here’s a list of plants that can’t be killed if you’re not sure you have a green thumb.
So what do we do with all this pollution? Purifiers or air exchangers do their job well, but the easiest way is to open a window from time to time!