Houseplants can brighten up a room and make it more inviting, but can they actually "clean" the air? As you'll see, the real story behind the connection between plants and air pollution is complicated.
Most of the online speculation around this connection mentions a 1989 NASA1 study conducted to research ways to clean air in space stations. This NASA study showed that plants did clean the air in a closed, limited environment or chamber. Other studies have confirmed2 that plants can remove harmful gases, such as formaldehyde, called volatile organic compounds, or VOCs, which have a long history of health impacts. So why don't we all use more green plants to remove pollution?
The problem is that our indoor environments are not like space stations. What works in a chamber study does not necessarily translate into real life settings.
One difference results from trying to scale-up from a test chamber to real life. The sample sizes used in testing, such as in the NASA study, are often very small so their findings don't translate well into real-world experiences. As a reviewer from the U.S. Environmental Protection Agency explained in a 1992 memo3 on the NASA study, "to achieve the same pollutant removal rate reached in the NASA chamber study" would require having "680 plants in a typical house." The memo also went on to say that it was "hardly surprising that the attempt to validate the test chamber results by Associated Landscape Contractors of America did not provide measurable success."
Different plant species, types of soil, lighting, temperature and size can all vary the impact of plants on air pollution. For example, the sunlight or temperature in a room can make some plants absorb more or less pollution.
What is more, plants may even contribute to unhealthy air conditions. Some plants may release VOCs into the air.4 The soil may have bacteria, pesticides or other contaminants.
While plants can be beneficial, the evidence does not show that they are an effective tool to reduce air pollution. A 2014 review of the research in scores of studies5 found mixed evidence in real-world studies for improved air quality indoors. The use of plants to clean the air in complex places like homes and offices needs much more study.
The bottom line? Don't expect your fern to solve any indoor air problems you have. Scientists continue to study the connection between plants and air pollution, and sometimes plants are effective at reducing air pollution in laboratories. But even if they help, adding plants would not be the best solution for cleaning up indoor air.
Houseplants may or may not really help reduce indoor air pollution — the jury is still out. But even at their best, they won't substitute for keeping pollution out of the air in the first place.
1Wolverton BC, Douglas WL, Bounds K. 1989. A study of interior landscape plants for indoor air pollution abatement U.S. National Aeronautics and Space Administration.
2Cruz MD, Christensen JH, Thomensen JD, and Müller R. 2014. Can ornamental potted plants remove volatile organic compounds from indoor air? — a review. Environ Sci Pollut Res. 21:13909–13928DOI 10.1007/s11356-014-3240-x
3Girman, J R. 1992. Comments on the Use of Plants as a Means to Control Indoor Air Pollution. U.S. Environmental Protection Agency.