The Environmental Protection Agency contends that such steps as using energy efficient ventilation and vapor barriers are more effective in controlling indoor pollution than houseplants. Some of our favorite houseplants, however, do help mitigate pollutants, some quite efficiently. Just don't count on them to do the job by themselves.
NASA Experiments
The basis for the claim that houseplants can help make the indoors healthier is a series of experiments completed in the 1980s by NASA and the Associated Landscape Contractors of America. The first experiments tested bamboo palm, Chinese evergreen, English ivy, Mother-in-Law's tongue sansevaria, ficus benjamina, peace lily, Gerbera daisy and pot chrysanthemum. Four types of dracaena; Janet Craig, marginata, massengea and Warnecki rounded out the group. Researchers tested plants with volatile chemicals including benzene, trichloroethylene and formaldehyde, all common indoor pollutants. The preliminary report of the group concluded that pollutants were mitigated not only by the plants' respiratory process but also by the nutrient-gathering processes of their roots.
More Experiments
The NASA experiments were conducted to address problems with air quality inside Skylab, a closed environment where scientists identified 107 airborne volatile organic compounds. Many of these compounds appear in well-insulated modern homes and come from similar sources; resins, plastics and synthetics used in fabricating structures and furnishings. Additional plants tested and found effective in removing pollutants included aloe vera, dwarf banana, spider plants, bamboo palms, snake plant sanseveria and three philodendrons; heartleaf, selloum and elephant ear. Again, both plants and roots consumed pollutants. Plants whose leaves and roots grew fastest were found to be most efficient at removing pollutants.
Follow-Up
B.C. Wolverton, the lead investigator in the 1980s studies, continued his inquiries at his firm, Wolverton Environmental Services, after concluding his work for NASA. His studies have pinpointed some plants that are especially efficient at recycling certain volatile compounds. In an article for the Journal of the Mississippi Academy of Sciences, Wolverton reported that Boston ferns and lady palms excel in removal of formaldehyde, xulene and ammonia. He also concluded that low-light tropical plants tend to grow the types of plant leaves and generate the soil organisms that are most efficient in processing volatile-compound pollutants. In a second article for journal, Wolverton outlined results for air and wastewater purification in a test home. In addition to plants used in previous experiments, the following plants functioned effectively; areca palm, corn plant, dieffenbachia, arrowhead vine, croton and umbrella grass. Wolverton has also reported success with orchids, bromeliads, azaleas and poinsettias.
References
- NASA:Foliage Plants for Improving Air Quality
- University of Minnesota Extension: Houseplants Help Clean Air
- EPA:The Inside Story: A Guide to Indoor Air Quality
- JMAS: Plants and Soil Microorganisms: Removal of Formaldehyde, Xulene and Ammonia from the Indoor Environment
- JMAS: Interior Plants Their Influence on Airborne Microbes Inside Energy-Efficient Buildongs
