Houseplants have been around for many years. It has always been a very practical way of beautifying our home, office, or place of business.
But in recent years, millennials (aka ‘Generation Y’) and the ‘Gen Z’ generations have been more fascinated, to say the least, by bringing a copious amount of greenery to the comforts of their living spaces. The reason behind it is that people generally spend more time indoors these than we ever did in the history of mankind.
This ‘indoor generation’ naturally keeps looking for ways to breathe cleaner and healthier air indoors. One popular way they try is to grow houseplants inside their home or office. But do house plants improve air quality?
How Did Indoor Gardening Become So Popular?
We all know how refreshing it can be to be around greenery and flowers. So, we naturally gravitate toward natural parks, sit on benches under a shade tree, and some of us even use beautiful photos of nature on our screensaver!
In a statistic published in October 2020, it is revealed that a peak of 38 million households in the US participated in houseplant gardening from 2010 to 2019. The trend steadily grew as plant-lovers share their personal stories and experiences of home gardening on social media with their fellow growers.
According to Houseplant Resource Center, there are many reasons why modern-day Americans buy into this houseplant fascination.
First, people of today spend 93% of their daily lives indoors, whether they choose to do it for convenience or they are forced by circumstances to stay inside often. This preference to stay indoors more than they do their activities out in the sun earned this age group the name, the “indoor generation”.
To fulfill the need for a piece of nature, Americans choose to have indoor plants as a home addition. As most people nowadays live in small apartments and rented spaces without a yard,
indoor gardening seems to be the most practical solution.
Another reason why houseplants rapidly became an obsession is that it provides a sweet escape to the hectic life modern people have, socially and work-wise. Tending to plants forces them to slow down, disconnect from the internet, and focus on their own physical and mental wellness.
Speaking of wellness, one common benefit cited by indoor gardening sites to entice home-growers is the supposedly renowned ability of houseplants to purify the air. Another recurrent term that would pop up is ‘phytoremediation’: the remarkable power of plants to remove toxins from the environment. Is there truth to it or is it merely propaganda?
See what scientific sources have to say on the matter.
What Science Says About Phytoremediation
From the term “Phyto” or “of a plant; relating to plants,” combined with “remediation” meaning “the action of remedying something, in particular of reversing or stopping environmental damage,” phytoremediation is, in fact, very real.
This biological process is supported by many reputable studies and is being used as a proposition to clean the environment most cost-effectively.
There are four major phytoremediation strategies that specific plants perform: phytoextraction,
phytostabilization, rhizodegradation, and phytovolatilization.
Phytoextraction
There are certain types of plants called “tolerant plants” that can withstand either drought or lack of sufficient water, lack of shade, insect pests, or diseases. These plants are said to have the
ability to “extract” or “to take up contaminants from the soil and accumulate them in aboveground tissues which are periodically harvested, thereby removing them from the soil,” one European environment agency said.
In short, the toxins are drawn up from the soil where they cannot infiltrate the root nor disrupt the growth of the plant.
Phytostabilization
A different set of skills is shown by the plants through their phytostabilization process. The plant can immobilize or stabilize the contaminants found in the root to prevent them from moving or spreading around the soil.
Because of this plant’s ability, the damage that a toxin can do to the plant itself will be minimized and the chance of the pollutant transfer to humans or animals will be reduced.
Rhizodegradation
‘Rhizo’-sphere is the area of influence of the soil. In rhizodegradation, plants produce root exudates, such as enzymes, to speed up the process of degradation of organic contaminants by microbial communities in the rhizosphere.
The faster and more diverse these microbial communities are in decaying the toxins, the lesser contaminants could damage the plant and its consumers.
Phytovolatilization
Another kind of special set of plants can change the contaminants into volatile compounds that can be transported from the soil to aboveground which can be released into the atmosphere. Volatilization of plants pertains to vaporizing solid or liquid contaminants to air particles which are considered to be less harmful.
All in all, this phytoremediation process that some indoor gardening promoters use as a selling point is significantly limited to soil cleaning only. Countless researchers openly question how the installation of houseplants can also translate to indoor air cleaning.
There are conflicting views on whether growing plants indoors can improve indoor air quality or devastate it. Earlier studies suggest that raising flora inside a home or an office space could remove the toxins from the air such as volatile organic compounds (VOCs) and other chemicals that can cause cancer.
However, modern researchers have looked into the published studies about indoor plants’ benefits and declared them as overstated and even irrelevant. A recent examination of the effects of houseplants reveals an increase of excess moisture due to water leaks from pots, production of allergy-causing particles such as pollens, and hypersensitivity to fertilizers and pesticides administered to the houseplants.
So do houseplants really have an impact on your home’s indoor air quality? Let’s get into the details.
How’s Your Indoor Air Quality?
As might be expected, a good deal of people would want to take a bit of plant’s freshness and a good feeling inside their very own homes. But since most residences have air conditioning systems, a significant concern can be raised as to whether it is good to have houseplants in a regular home with modern installations.
One important aspect of healthy living at home and likely will impact whether you will grow houseplants indoors or not is the state of your indoor air quality.
The public used to be primarily concerned with how clean the outdoor air is. Government institutions such as the US Environmental Protection Agency or EPA monitor the toxicity levels of outside air caused by automobile combustions, burning of coal, natural gas, oil, and biomass, emissions from heating and conditioning devices, and other pollutants.
The scrutiny of outdoor air pollution is warranted as the World Health Organization (WHO) reported the harmful health effects of breathing polluted air, especially to children. These include, but are not limited to increased acute respiratory morbidity manifested as pneumonia and asthma, decreased lung function, and in worst cases, death.
However, a new threat to Americans breathing health suddenly came to light. Indoor air pollution has been discovered to also be damaging the well-being of residents and office workers, the effects of which are experienced immediately after exposure or even years later.
The EPA, which intently watches the rate of indoor air pollution in the country and its effects, ranked indoor air pollution as one of the Top 5 environmental risks to public health. It also listed the following as the immediate reactions to toxins inside the house: “irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue.”
As for health problems that can only be observed after months or years of exposure to indoor air toxins, the EPA noted respiratory diseases, heart diseases, and cancer.
Those with preexisting medical conditions, the elderly, and children have the highest risk factors for these ailments, both immediate and delayed onset.
What could endanger your indoor air quality? The National Environmental Education Foundation (NEEF) enumerated the most common pollutants found right in the comfort of our homes including lead, dust mites, mold, radon, pests, carbon monoxide, pet dander, and second-hand smoke.
Some other indoor toxins are produced by innocently-looking items that we probably use every day for cleaning, repair, and maintenance around the house. Hairsprays, deodorants, oven cleaners, paints, pesticides, laundry aids, floor and furniture polishes, glue, and air fresheners contain some of these harmful pollutants.
Now that more and more people are staying indoors—either by choice or necessity—indoor air quality is, without a doubt, one key factor that homeowners should watch out for.
Since we cannot get rid of absolutely everything that could potentially contaminate the air inside our home, we strive to look for ways to purify the air instead. Are houseplants the solution?
Do Houseplants Improve Air Quality?
The most basic aid a houseplant provides, yet the most powerful is its ability to consume carbon dioxide to produce food and release oxygen as its byproduct. Your science teacher might have called this situation a “symbiotic relationship” between plants and humans and animals, where both parties benefit.
The less carbon dioxide in the air plus more oxygen makes breathing indoors a lot easier and healthier.
But that’s not all houseplants do.
If you happen to search for the benefits of raising indoor plants for your breathing air, you will find important research funded by none other than the National Aeronautics and Space Administration or NASA, written by B.C. “Bill” Wolverton.
Wolverton is an environmental scientist whose work has been sponsored by NASA to investigate the natural ability of Earth’s environment to cleanse itself from the pollutants left by biological warfare centers.
In 1989, Wolverton published a report stating that plants could improve indoor air quality. He poignantly said, “If a man is to move into closed environments, on Earth or in space, he must take along nature’s life support system.” Plants.
His discovery catapulted several more technical studies and a popular book entitled How to Grow Fresh Air: 50 Houseplants that Purify Your Home or Office. Wolverton explained in layman’s terms how plant life produces water vapor that produces a “pumping action” to pull polluted air down to its roots. The toxins are then converted into food for the house plant.
Different kinds of plants were shown to remove varying toxins from the indoor air according to NASA research. These include volatile organic compounds (VOCs) such as benzene, trichloroethylene (TCE), formaldehyde, and toluene.
These VOCs are known for being irritants and in higher levels of exposure, cancer-causing.
The International Association of Certified Home Inspectors or InterNACHI is one of the many unbiased institutions that used NASA’s research by Wolverton as the backbone of their recommendation to start growing houseplants.
The organization also published the study’s implication in one of their articles which says, “in a 1,800-square-foot house, occupants should incorporate 15 to 18 houseplants in 6- to 8-inch diameter containers to improve air quality. The larger and more vigorously they grow, the better.”
So looks like NASA is on to something. But, is that all?
What Do You Risk with Indoor Plants?
For many years, this body of research backed up by NASA about the immense advantage of plants indoors has been respected and trusted.
But recent studies disputed Wolverton’s claim such as that of Bryan Cummings & Michael Waring through their paper published in 2019 by the Journal of Exposure Science & Environmental Epidemiology. In essence, the newer sets of research suggest that the benefits of houseplants are “vastly overstated,” according to Drexel University.
The proponents of modern studies are debating the validity of the experiments done by NASA that have become the foundation of their conclusions about houseplants’ advantages.
“Potted plants have demonstrated abilities to remove airborne volatile organic compounds (VOC) in small, sealed chambers over timescales of many hours or days…These potted plant chamber studies reported outcomes using various metrics, often not directly applicable to contextualizing plants’ impacts on indoor VOC loads,” the paper boldly stated.
Other sources also brought up the possibility that plants could even put indoor air quality at risk instead of improving it. How so?
Moisture Level Increase. “Plants release roughly 97% of the water they take in,” one source said, as part of photosynthesis. Additionally, some homeowners may tend to overwater their plants, either due to a lack of experience in indoor gardening or by trying to make up for days they forgot to water the plants.
Either way, if too much water is left on the bottom of the pots and the surrounding area, it could cause dampness in the air. High levels of humidity in turn could be a trigger to mold and mildew growth problems.
Potential Allergen Source. While having flowers indoors could be particularly beautiful, we must not forget that they actively produce pollen. Pollen could be mistaken by our immune system as a harmful enemy that needs to be eradicated quickly, causing sneezing, eyes watering, coughing, and other respiratory issues.
Fertilizer and Pesticide Hazards. To preserve the beauty and vigor of your houseplants, others might be tempted to implement fertilizer or pesticides to their indoor vegetation. EPA decisively said that “Pesticides are inherently toxic… 80 percent of most people’s exposure to pesticides occurs indoors and that measurable levels of up to a dozen pesticides have been found in the air inside homes.”
Are Houseplants’ Benefits Overstated?
When B.C. “Bill” Wolverton, NASA’s environmental scientist discovered the amazing ability of swamp plants to clean up the mixture of herbicides that US military forces used against Vietnam called Agent Orange, the space agency got excited and funded him to do more research.
Wolverton diverted his study this time to the air-cleansing ability of plants, especially when in 1973, NASA’s Skylab space station has been plagued by volatile organic compounds (VOCs) such as formaldehyde, benzene, and trichloroethylene that can trigger allergies and
other health problems.
Meanwhile, on planet Earth, people are also plagued by indoor toxins caused by synthetic materials as houses and buildings were purposely made to be airtight to conserve energy. So airtight that it is almost comparable to the environment in Skylab, some determined.
So when Wolverton released his paper entitled Interior Landscape Plants for Indoor Air Pollution
Abatement in September 1989, seemed to have miraculously solved the problems in our home planet and the space station.
The published research highlighted that a “promising approach to further reducing trace levels of air pollutants inside future space habitats is the use of higher plants and their associated soil microorganisms.”
Bryan Cummings and Michael Waring, authors of the research published in the Journal of Exposure Science & Environmental Epidemiology have a big problem with that claim. You can already tell from the title of their paper: Potted Plants Do Not Improve Indoor Air Quality: A Review and Analysis of Reported VOC Removal Efficiencies. To debunk the theory that a simple houseplant can purify the indoor air, they looked at 12 formerly published scientific experiments that tested 196 plants for ten years.
According to Waring and his associates, the setting of Wolverton’s experiment with plants are in small, sealed laboratories heavily polluted with VOCs. But in a real-life setting, plants cannot do a significant air cleaning in a normal home or office.
In an interview with Waring about their groundbreaking research, National Geographic released his statement, “Plants, though they do remove VOCs, remove them at such a slow rate that they can’t compete with the air exchange mechanisms already happening in buildings.”
In a separate discussion, this time with The Atlantic, Waring declared that in a 10 feet by 10 feet by 8 feet, “you would have to put 1,000 plants in that office to have the same air-cleaning capacity of just changing over the air once per hour, which is the typical air-exchange rate in an office ventilation system.”\
That would mean that you have to put 10 regular plants per square foot, or if you chose the most effective type of VOC-filtering plant, one plant per square foot would still be required.
If you are not prepared in turning your apartment into an urban jungle, you should think twice before buying that many plants to achieve its air purifying power.
Waring said that the best way to clean the air from harmful contaminants is to remove the source of the pollutants, increase ventilation, and use air filtering devices.
So, was NASA lying about the purifying power of plants? Not entirely.
The positive effects of houseplants on the beauty and mental wellness of occupants are still supported by legitimate research. Combining the use of indoor plants with other purifying devices or an increase in ventilation can help in improving your indoor air quality. Careful watering, a wise choice of flowers or plants to grow, and steering clear of harsh chemicals such as fertilizers and pesticides are also essential in raising indoor plants.
Should I Put House Plants Indoors?
The choice of having plants around your living space and workspace is entirely yours. After all, even without its air-purifying ability, greenery offers the best company while doing your daily chores.
Healthline lists at least 5 benefits of tending to houseplants in your mental and emotional wellness:
- Lowers levels of anxiety
- Increases attentiveness and memory
- Increases productivity
- Reduces stress levels and boosts mood
- Sparks creativity
A word of caution, though: having plenty of houseplants around may increase the level of humidity indoors, so be careful not to overwater the plants. You would not want excessive moisture inside your home as it is a perfect breeding environment for molds and mildews.
Also, be attentive to allergy-inducing plants or flowers especially if you have kids around or those with asthma. Avoid using harsh chemicals such as pesticides or fertilizers to enhance the growth of your beloved houseplants.
A Balanced View on Greenery
The ultimate goal is to have a reasonable view of the effects of indoor plants on the state of air quality inside our homes. While the level of its ability to remove harsh chemicals and toxins from the air is debatable, there are still legitimate benefits of raising houseplants indoors. If we take advantage of the use of air-purifying devices such as air purifiers with HEPA filters along with proper ventilation, we give our houseplants a fighting chance against indoor toxins.