Good day to all our visitors! Today I want to discuss a very hot topic. During the last days, the internet is full of publications unequivocally stating that indoor plants not just do not clean the air in the room, but can even be very dangerous for the inhabitants. Moreover, it is claimed that opening the window for several minutes may be more effective for the air refreshment than an indoor plant. These publications refer the article by Cummings B.E.and Waring M.S. Potted plants do not improve indoor air quality: a review and analysis of recorded VOC removal performance. J Expo Sci Environ Epidemiol. November 6, 2019 doi: 10.1038 / s41370-019-0175-9.
This conclusion is very surprising and even shocking. Sure, we are taught from childhood that the room should be well ventilated. However, the reality of today’s cities is that the concentration of harmful substances in the air can be tens of times higher than acceptable, making us refuse such a simple and cheap way to clean the indoor air as a window opening. Therefore, automatic air purifiers and air fresheners are becoming an increasingly desirable tool. But even so, the indoor plants have always been considered highly effective air “cleaners”. Here are some examples:
- Chlorophytum cleans volatile sulfur compounds, benzene, formaldehydes; and also has a bactericidal effect.
- Ficus Benjamina cleans formaldehyde, trichlorethylene and benzene; and also emit phytoncides (to neutralize microorganisms);
- Spathiphyllum cleans volatile ammonia, benzene, formaldehyde and trichloroethylene;
- Nephrolépis cleans xylene, moreover, it is believed that Nephrolépis actively absorbs screen radiation.
- Dracaena Marginata has the ability to moisturize the air and reduces the content of formaldehyde and trichloroethylene,
Of course, I can continue the list. Therefore, the work of Cummings and Waring is shocking. Please explain!
Leonid Livshits: Inhabitants of developed countries spend up to 90% of their time indoors; therefore, the air quality in this condition is critical for human life. Many volatile chemically and biologically harmful particles accumulate in the air which we breathe. Some of them are originated from outdoors; some is associated with building materials and furniture; and some are the products of human activities. An increased concentration of such particles can be a direct threat for our health.
Indoor potted plants were considered till day as an effective option for cleaning the air from chemical and biologically active substances. In their turn, Cummings and Waring analyzed 12 published studies and 196 experimental results which mostly support this hypothesis. However, Cummings and Waring doubt most of these results, arguing that the experiments in these investigations were set up incorrectly. As an example, the authors criticize the famous NASA report by Wolverton BC, Johnson A, Bounds K. Interior landscape plants for indoor air pollution abatement. 1989. Report No .: NASA-TM-101766 (https://ntrs.nasa.gov/search.jsp?R=19930073077), suggesting that the positive effect was obtained solely due to the unrealistically small workspace in which experiment was performed.
In addition, Cummings and Waring showed the calculations of plant biomass to room size balance, proving the quantitative inefficiency of using the potted plants in indoor air cleaning. The authors cite the article of Levin (Can house plants solve IAQ problems? Indoor Air Bull. 1992; 2: 1–7), which proves that 680 indoor plants will be required to clean ~ 140 m2 apartment, that is logically impossible.
Now let me present several “weak” points of Cummings and Waring’s study.
First, the article of Cummings and Waring discussed the potted indoor plants. In view of the current trend to use so-called home green walls (vertically located plants that achieve a high leaf area density per unit area) and the botanical biofilter systems for an efficiently air refreshing by its active passing through the plant growing medium, Cummings and Waring conclusions are mostly out of date. By the way, most internet publications do not mention the exact subject of the discussion (potted plants), thus generalizing the conclusion about inefficiency (and even harm) for all indoor plants.
Second, Cummings and Waring compare the effect of plant activity with ventilation, without specifying how clean the air is outside. Unfortunately, in modern industrial cities, the formula “open the window and get a portion of fresh, unpolluted air” is far to be real.
Third, Cummings and Waring chose to analyze only research works which basically support their hypothesis. For example, they do not relate a large study of Australian colleagues published in 2018 (Pettit T et al. Towards practical indoor air phytoremediation: A review. Chemosphere. 2018; 208: 960-974). Pettit et al. describe the phytopurification of indoor air as a very effective method and cite numerous studies confirming this conclusion.
I will express my personal opinion: it is very scary and sad, but due to the difficult environmental situation in industrial cities, it is much more efficient and useful to use home plants as “cleaners” of chemical and biological pollution than to open the window and enjoy the fresh air. In other words, people, who for any reason need to spend more time indoors with potted plants, are more protected from the volatile killing molecules than people who prefer or need to be outdoors. Therefore, the statement of the media that the indoor plants are ineffective, is simply dangerous! By the way, we have not talked about the positive psychological effect associated with a home garden…
And, finally, a few words about the garden. As an unhappy conclusion, I want to cite Gerald Durrell, a famous British naturalist, humanist and author:
We have inherited an incredibly beautiful and complex garden, but the trouble is that we have been appallingly bad gardeners. We have not bothered to acquaint ourselves with the simplest principles of gardening. By neglecting our garden, we are storing up for ourselves on the not very distant future a world catastrophic as bad as any atomic war, and we are doing it with all the bland complacency of an idiot child chopping up a Rembrandt with a pair of scissors… We now stand so aloof from nature that we think we are God. This has always been a dangerous supposition…
Featured image by Magda Ehlers from Pexels.