Health & Wellbeing

Some indoor plants may be bad for your health

Some indoor plants may be bad for your health
A Snake Plant – found to emit 12 volatile organic compounds into the atmosphere (Photo: Martin Olsson)
A Snake Plant – found to emit 12 volatile organic compounds into the atmosphere (Photo: Martin Olsson)
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A Snake Plant – found to emit 12 volatile organic compounds into the atmosphere (Photo: Martin Olsson)
A Snake Plant – found to emit 12 volatile organic compounds into the atmosphere (Photo: Martin Olsson)

Houseplants are not only aesthetically pleasing giving a touch of color to otherwise drab offices or houses, they also combat indoor air pollution, particularly with their ability to remove volatile organic compounds (VOCs) from the air. These compounds are gases or vapors emitted by solids and liquids that may have adverse short- and long-term health effects on humans. But in addition to giving off oxygen and sucking out harmful VOCs, a new study has shown that some indoor plants actually release VOCs into the environment.

A research team at the University of Georgia’s Department of Horticulture conducted a study to identify and measure the amounts of VOCs emitted by four species of popular indoor potted plants and to note the source of VOCs and differences in emission rates between day and night. The four plants they chose were Peace Lily (Spathiphyllum wallisii Regel), Snake Plant (Sansevieria trifasciata Prain), Weeping Fig (Ficus benjamina L.), and Areca Palm (Chrysalidocarpus lutescens Wendl.).

Samples of each plant were placed in glass containers with inlet ports connected to charcoal filters to supply purified air and outlet ports connected to traps where volatile emissions were measured. The results were compared to empty containers to verify the absence of contaminants. A total of 23 volatile compounds were found in Peace Lily, 16 in Areca Palm, 13 in Weeping Fig, and 12 in Snake Plant. Some of the VOCs are ingredients in pesticides applied to several species during the production phase.

And it turns out the plants themselves aren’t the only ones responsible for the release of VOCs. Micro-organisms living in the soil were also to blame for releasing volatiles into the atmosphere along with the plastic pots containing the plants, which were the source of 11 of the VOCs – several of which are known to negatively affect humans.

The study also found that VOC emission rates were higher during the day than at night in all of the species, and all classes of emissions were higher in the day than in the night. This was expected as the rate of release is determined by the presence of light along with many other factors that affect synthesis.

The study concluded that, although ornamental plants are known to remove certain VOCs, they also emit a variety of VOCs, some of which are known to be harmful to humans and animals. However the researchers did go on to say that the longevity of these compounds hasn’t been adequately studied, so their impact on humans is unknown.

That plant sitting in the corner isn’t looking quite so attractive now, is it? But before you relegate any plants to the garbage consider this. If the plastic pots were found to be the source of 11 VOCs, you’ve got to thankful the plants at least remove some VOCs as well as emitting them – the same can’t be said for the mass of plastic that probably surrounds you right now. Maybe give that plant some water instead.

The study, Volatile Organic Compounds Emanating from Indoor Ornamental Plants, appears in the American Society for Horticultural Science journal HortScience.

I hate this study. It's absolute garbage. So the plants absorb VOCs but also emit them, which may or may not be harmful to humans. How harmful? What kind of harm? What is the net harm of having the plant vs not having the plant? These are all questions that should have been answered before publishing these results.
Harold B. De Jesús
Plantas Peligrosas para la salud humana: Lilas Chuchos Palmas Ficus, palo del frente a casa Alma
I agree with Stradric...Plants emit VOCs...OK...good information...but what does that mean? Did they do a study to see how many VOCs humans emit? Perhaps we polute our air more than the plants do... This study is nothing more than FUD. Ed
Never forget: 'you’ve got to thankful the plants at least remove some VOCs as well as emitting them'. Stupid study. Ever heard of Fick's law of diffusion? The experiment is probably just measuring residual VOCs that are everywhere in our environment, and were probably absorbed by the plant. Seal up the plant in a container with purified air for a year, and I bet it no longer releases VOCs.
Dylan Anderson-Berens
They need to do what is called a longitudinal study - I suspect much of the off-gasing is from those pesticides and will go away with time. You guys were right on about the net effect!
Ryan Shanks
While interesting, I don't like this article on the grounds that the title seems misleading, and the counter argument is saved for the last paragraph.
It also seems a bit unclear whether, for example, the snake plant itself emits 12 VOCs or 1, with the other 11 coming from the pot (in which case its not such a big deal as most people opt for a nicer stone pot that's hopefully cleaner).
I totally agree with Stradric about the study
This study doesn't even use a controlled experiment. Four plants are used, only: one of each species. Variations found in VOC emission could therefore be due to differences between the growing conditions of the plants before the researchers purchased them: it's entirely likely that the plants came from different growers, even though they were purchased at the same store. On that note, the authors say that pesticides used on the plant are thought to have an effect on the VOCs emitted; yet, they do not do tests on a large number of plants, from different growers, to determine whether the pesticides which they detect are anomalies or the norm.
Furthermore, THE AUTHORS STATE POSSIBLY BENEFICIAL EFFECTS FROM SOME of the VOCS. (This goes against everything I've ever heard of VOCs, but it is what they say.) Specifically, they say:
" Santalol, present in S. wallisii [Peace Lily], has been reported to have a relaxing and sedative effect in humans."
Linalool was also reported as emitted by the Peace Lily, and the authors say that "Linalool is known to have a sedative effect on autonomic nerve activity and mood and antifungal activity".
[Quotes taken from publication referenced in this webpage's article: "Volatile Organic Compounds Emanating from Indoor Ornamental Plants", by Yang, Son, and Kays. HORTSCIENCE 44(2):396–400. 2009. ]
Some of these reported effects sounds good (such as calming the nerves and mood), though some I'm not sure about (such as sedating antifungal activity: I'm not a medical expert, so I don't know whether that is good or bad).
To be certain, at least one of the emitted VOCs is stated to be potentially harmful (that is 2-Ethyl-1-hexanol, which is emitted by the plastic pot and is associated with "sick building syndrome" when present in certain concentrations).
Furthermore, consider that many of the VOCs - including the aforementioned potentially-harmful one - were found to be emitted by the PLASTIC POT. So, to avoid this, simply pot your plants in something less toxic than plastic.
On one final note, it is possible that plants' emissions of pesticide products may reduce over time. (These emissions were presumed, by the authors, to come from pesticides which were applied during the plants' production processes). If so, then old plants may not emit these anymore. I don't know how long it would take for the plants to stop emitting pesticide-related VOCs (if they ever do), but starting a new plant via a cutting from your parents' or friends' long-standing plants might be a good way to avoid the pesticides.
Thanks for reading.
Don't know if I can trust the reporting in this article. I know for a fact plants don't absorb VOCs (at least not at any significant rate). Anyone who reads the actual NASA report they consistently misrepresent would know that. So if the author is wrong about that, can I trust that they are accurate about plants GIVING OFF the VOCs into the air?