In the late 1980s, a study by NASA and the Associated Landscape Contractors of America (ALCA) was conducted to find ways to purify the air for extended stays in orbiting space stations. The study resulted in excellent news for homeowners and office workers everywhere, because it concluded that common houseplants not only make indoor spaces more attractive, they also help to purify the air!
The common indoor plant may provide a natural way of helping combat “SICK BUILDING SYNDROME”. Those plants in your office or home NASA scientists have found them to be surprisingly useful in absorbing potentially harmful gases and cleaning the air inside modern buildings.
While it’s a well known fact that plants convert carbon dioxide into oxygen through photosynthesis, the NASA/ALCA study showed that many houseplants also remove harmful elements such as trichloroethylene, benzene, and formaldehyde from the air.
The advantage that houseplants have over other plants is that they are adapted to tropical areas where they grow beneath dense tropical canopies and must survive in areas of low light. These plants are thus ultra-efficient at capturing light, which also means that they must be very efficient in processing the gasses necessary for photosynthesis. Because of this fact, they have greater potential to absorb other gases, including potentially harmful ones.
In the study, NASA and ALCA tested primarily for three chemicals: formaldehyde, benzene, and trichloroethylene. Formaldehyde is used in many building materials including particle board and foam insulations. Additionally, many cleaning products contain this chemical. Benzene is a common solvent found in oils and paints. Trichloroethylene is used in paints, adhesives, inks, and varnishes.
NASA noted that some plants are better than others in treating certain chemicals. For example, English ivy, gerbera daisies, pot mums, peace lily, bamboo palm, and Mother-in-law’s Tongue were found to be the best plants for treating air contaminated with benzene. The peace lily, gerbera daisy, and bamboo palm were very effective in treating trichloroethylene. Additionally, NASA found that the bamboo palm, Mother-in-law’s tongue, dracaena warneckei, peace lily, dracaena marginata, golden pathos, and green spider plant worked well for filtering formaldehyde. After conducting the study, NASA and ALCA came up with a list of the most effective plants for treating indoor air pollution.
The recommended plants are listed below. Note that all the plants in the list are easily available from your local nursery.
- Oxycardium Philodendron, heartleaf philodendron, Philodendron scandens
- Elephant Ear Philodendron, Philodendron domesticum
- Massangeana, cornstalk dracaena, Dracaena fragrans
- English Ivy, Hedera helix
- Spider Plant, Chlorophytum comosum
- Janet Craig, Janet Craig dracaena, Dracaena deremensis
- Warneckii, Warneck dracaena, Dracaena deremensis
- Weeping Fig, Ficus benjamina
- Golden Pothos, Epipiremnum aureum
- Peace Lily, Mauna loa, Spathiphyllum
- Selloum Philodendron, Philodendron selloum
- Chinese Evergreen, Aglaonema modestum
- Bamboo or reed palm, Chamaedorea sefritzii
- Snake Plant, Sansevieria trifasciata
- Red-edged Dracaena, Dracaena marginata
For an average home of under 2,000 square feet, the study recommends using at least fifteen samples of a good variety of these common houseplants to help improve air quality. They also recommend that the plants be grown in six inch containers or larger.
Here is a list of resources for more information on this important study:
PDF files of the NASA studies related to plants and air quality:
List of NASA studies related to treating a variety of air and waterborne pollutants with plants:
Here is a list of the pollutants NASA tested for and the plants they found that worked the best for each one:
Trichloroethylene is primarily used in the metal degreasing and dry cleaning industries; also in printing inks, paints, lacquers, varnishes, adhesives. In 1975 the National Cancer Institute reported that an unusually high incidence of hepatocellular carcinomas was observed in mice given TCE by gastric intubation and now considers this chemical a potent liver carcinogen.
The NASA study found that the best plants for removing trichloroethylene are the Gerbera Daisy, Chrysanthemum, Peace lily, Warneckei, Dracaena marginata
Benzene is a very commonly used solvent and is also present in many common items including inks, oils, paints, dyes, plastics, rubber, dyes, detergents, gasoline, pharmaceutical, tobacco smoke, synthetic fibers. In addition it is used in the manufacture of explosives.
Benzene has long been known to irritate the skin and eyes. In addition, it has been shown to be mutagenic to bacterial cell culture and has shown embryotoxic activity and carcinogenicity in some tests. Evidence also exists that benzene may be a contributing factor in chromosomal aberrations and leukemia in humans. Repeated skin contact with benzene will cause drying, inflammation, blistering and dermatitis.
Acute inhalation of high levels of benzene has been reported to cause dizziness, weakness, euphoria, headache, nausea, blurred vision, respiratory diseases, tremors, irregular heartbeat, liver and kidney damage, paralysis and unconsciousness. In animal tests inhalation of benzene led to cataract formation and diseases of the blood and lymphatic systems. Chronic exposure to even relatively low levels causes headaches, loss of appetite, drowsiness, nervousness, psychological disturbances and diseases of the blood system, including anemia and bone marrow diseases.
The best plants for removing benzene were determined to be English Ivy, Dracaena marginata, Janet Craig, Warneckei, Chrysanthemum, Gerbera Daisy, Peace lily
Formaldehyde is a ubiquitous chemical found in virtually all indoor environments. The major sources which have been reported and publicized include urea-formaldehyde foam insulation (UFFI) and particle board or pressed wood products used in manufacturing of the office furniture bought today. It is used in consumer paper products which have been treated with UF resins, including grocery bags, waxed papers, facial tissues and paper towels. Many common household cleaning agents contain formaldehyde. UF resins are used as stiffeners, wrinkle resisters, water repellents, fire retardants and adhesive binders in floor coverings, carpet backings and permanent-press clothes. Other sources of formaldehyde include heating and cooking fuels like natural gas, kerosene, and cigarette smoke.
Formaldehyde irritates the mucous membranes of the eyes, nose and throat. It is also a highly reactive chemical which combines with protein and can cause allergic contact dermatitis. The most widely reported symptoms from exposure to high levels of this chemical include irritation of the eyes and headaches. Until recently, the most serious of the diseases attributed to formaldehyde exposure was asthma. However, the Environmental Protection Agency (EPA) has recently conducted research which has caused formaldehyde to be strongly suspected of causing a rare type of throat cancer in long-term occupants of mobile homes, where particle board and other sources of formaldehyde are used extensively.
When it comes to removing formaldehyde, the best plant choices are Azalea, Philodendron, Spider plant, Golden Pothos, Bamboo palm, Corn plant, Chrysanthemum, Mother-in-law`s tongue.
Many people feel that the use of houseplants is not needed if they are using an air purifier. However, research has shown that even if you use a HEPA air filter or an ionic air purifier, there is a lot of difference that can still be made by many common house plants, which act as a living air purifier. With the exception of an activated carbon filter, common indoor air filters, such as HEPA or ionizers, will totally miss the toxic household gases, such as carbon monoxide, formaldehyde, and volatile organic gases (VOG).
According to NASA, one plant should be used for every 100 to 120 square feet of office or living space and the plants should be in at least six inch containers with nothing covering the potting soil. In addition to removing pollutants in your home or office, plants also make for a more pleasant place to live and work – where people feel better, perform better, and enjoy life more. Here are some of the other benefits from having indoor plants:
Plants are a Source of Oxygen – Plants take in carbon dioxide and produce oxygen through the process known as photosynthesis. The more plants you have, the more oxygen you will receive.
Plants Make You Happy – House plants make people feel calmer and more optimistic, says Bruno Cortis, M.D., a Chicago cardiologist. Interestingly, he says that studies have shown that hospital patients who face a window with a garden view recovered more quickly than those who had to look at a wall.
Plants Fight Fatigue and Colds – According to a University of Agriculture in Norway study, indoor plants can reduce fatigue, coughs, sore throats and other cold-related illnesses by more than 30 percent, partially by increasing humidity levels and decreasing dust.
Plants at the Office – Major corporations and work environments are beginning to catch on that adding plants indoors does wonders for employee health and morale. According to one study published in Rehabilitation Literature, a manufacturing company integrated plants into its office so that no employee would be more than 45 feet from greenery. The result? Company administrators said they noticed enhanced creativity and increased productivity in employees. One popular plant to use in offices is the Dragon Tree plant. Besides being one of the most effective in removing harmful impurities from the air, it`s exotic looks adds character to any room.
It is important to note though that not all plants are good as indoor air cleaners and that some plants are poisonous and should be handled with care, or not at all if you have small children. Some examples of toxic plants include: Nightshade, Creeping Charlie, Foxglove, Oleander, Sago Plant, Privet, Rhododendron, Umbrella Plant, Ivy, Ripple ivy, Sweet Pea, Vinca, Spider Mum, and Poinsettia. Consumers looking for houseplants that purify air should probably steer away from the above named plants if they have young children and indoor pets, as these plants can sometimes be fatal if consumed.
NASA research has consistently shown that living, green and flowering plants can remove several toxic chemicals from the air in building interiors. You can use plants in your home or office to improve the quality of the air to make it a more pleasant place to live and work – where people feel better, perform better, any enjoy life more.