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House Plants Can Help You Breathe Easier
Bill Wolverton, Ph.D.



It is well documented that most building materials, furnishings and other products in modern buildings are made of synthetic materials that give off hundreds of volatile organic chemicals into the air we breathe.  In fact, EPA ranks indoor air pollution among the top five threats to our health.  The challenge to architects and builders is how to provide healthy air within a building, yet maintain energy-efficiency.

 

 

House Plants and NASA

 

NASA was faced with a similar dilemma when formulating plans for long-term space habitation.  It is commonly understood that plants provide the earth with its supply of fresh, clean air.  Even small school children understand the role rain forests play in human survival.  NASA sought to mimic nature by using houseplants in Text Box: Top Ten Plants Areca Palm Lady Palm Bamboo Palm Rubber Plant Dracaena “Janet Craig” English Ivy Dwarf Date Palm Ficus Alii Boston Fern Peace Lily the indoor environment to act as the building’s lungs.  Thanks to NASA research findings, houseplants are a promising means to improving the air we breathe indoors.  After more than 25 years of further research by scientists in the U.S., Australia, Europe, Japan and Canada, the ability of houseplants to improve indoor air quality is no longer a matter of conjecture…but scientific fact.

 

“How To Grow Fresh Air” (Penguin, 1997) provides data in an easy, non-technical format and rates 50 houseplants for their (1) ability to remove chemicals; (2) ease of growth and maintenance; (3) resistance to insect infestation and (4) transpiration rates.  Based upon these criteria, the top ten rated plants are shown in the adjacent chart.

 

 

Amazing Filters

 

Text Box: Removal of Chemicals by the Peace Lily Chemical Micrograms Per Hour Acetone ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Methyl alcohol ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Ethyl alcohol ■ ■ ■ ■ ■ ■ ■ ■ ■ Benzene ■ ■ ■ ■ ■ ■ ■ Ammonia ■ ■ ■ ■ ■ Trichloroethylene ■ ■ ■ ■ Formaldehyde ■ ■ ■ Xylene ■ Plants were tested for their ability to remove various chemicals commonly found in the indoor environment.  The studies showed that plants differ in their ability to remove chemicals and that the more effective plants are ones with high transpiration rates, such as the palm family. 

 

As plants transpire (breathe), they set up convection currents that transport air, along with any airborne chemicals, to the root zone where root microbes biodegrade the pollutants into chemical structures that can be used as a source of food for the microbes and the plant. 

 

In other words, plants are biological air cleaning machines!  For example, the peace lily (Spathiphyllum sp.) is a common houseplant and is effective in removing chemicals as shown in this chart.

 

Studies have also shown that plants emit substances, including negative ions, from their leaves that reduce airborne molds and bacteria in the surrounding air.  Therefore, the more plants in a home or office the healthier the air should be.  At least two medium to large plants in each 100-200 ft2 room should help clean and refresh the air. 

 

Plants are often accused of being harbingers of molds and this is of concern to those with allergies or asthma.  Molds can grow on the surface of damp potting soil or on floor covering if plants are overwatered. 

 

To avoid mold growth, it is best to grow houseplants in hydroculture, a soil-free plant container using pebbles as a growth media. (See Photo)  If plants are grown in potting soil, then cover the soil surface with a layer of decorative gravel and be careful not to overwater.

 

 

New Research

 

In an effort to improve the air purifying powers of houseplants, new research has led to the development of plant-based air filters.  Plants are grown in a mixture of highly absorbent filtering media, such as activated carbon, and the air is moved more rapidly by a fan.  One filter can remove airborne chemicals at a rate equivalent to 200 houseplants.   

 

Small, portable units are currently marketed in Japan and, hopefully, will be available in the U.S. at some future date.  Whole building, modular units are in the scale-up design phase and should be available in the U.S. within the next year.  So, as these products become available fewer plants will be needed in each area.

 

Plants alone may not be the total solution when serious indoor air quality problems exist.  Proper source management (allowing building materials and furnishings to vent volatile fumes before installation), complete air distribution and preventive maintenance are all components of a healthy building.  However, we can all breathe easier knowing that the houseplants we enjoy for their beauty are also working hard to keep us healthy!

 

 

 

Bill Wolverton, Ph.D. is President of Wolverton Environmental Services, Inc. and author of the book “How To Grow Fresh Air – 50 Houseplants that Purify Your Home or Office.”   A retired NASA scientist, he has studied plants as a way of cleaning our environment for more than thirty years. For more information you can email him at wesinc1@hotmail.com

 

 

 

The Highest Level is the monthly e-mail newsletter of the Humber Parkerson Clinic and is designed to empower our patients and the general public to make informed decisions on issues of nutrition, lifestyle, and spinal care.  To receive The Highest Level each month, e-mail your request to HighestLevel@humberparkerson.com.

 

© Humber Parkerson Clinic 2006

 

 

September 2006 issue of The Highest Level

 

 

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