New Research on Pollutant Removal by Indoor Plants By Paula Szilard In research published in the August 2009 issue of HortScience, researchers at the University of Georgia screened indoor plants for their pollutant removal efficiency. They tested 28 plants frequently encountered in interiorscapes for how well they removed the volatile organic compounds (VOC’s) benzene, toluene, octane, trichlorethylene and a-pinene. These are all pollutants that are commonly found in petroleum based indoor coatings, cleaning solutions, plastic, tobacco smoke, exterior exhaust fumes leaking into buildings, paint, adhesives and building materials. At high concentrations they are actually harmful to plants. Researchers conducted the study by unpotting the plants, rinsing off the potting mix and placing them in covered glass containers. They then piped in measured quantities of the pollutants and tested to determine how much of each had been removed at three and six hour intervals. Similar glass containers containing the potting mix and the pots only served as controls. The computations of removal efficiency of individual species were based on the amount of leaf area of the plants tested, therefore it stands to reason that a large plant with a lesser removal efficiency might still remove more pollutants than a small plant with a higher removal efficiency, simply because it has a lot more leaf area. Likewise, a lot of plants with poor removal efficiency might prove better than a few plants with high removal efficiency. The results of the study were somewhat surprising. Of the 28 plants tested, Hemigraphis alternata, (a tropical ground cover with dark purple crinkly leaves sometimes known as red-flame ivy), Hedera helix (ivy), Hoya carnosa (the most commonly available hoya), Asparagus densiflorus (sometimes known as Asparagus meyersi, with shorter densely leaved, plume-like shoots) were the most efficient in removing all of these pollutants. Tradescantia pallida (Setcreasea pallida), another tropical groundcover with narrow purple leaves also known as purple heart showed superior removal of four of these five pollutants—benzene, toluene, trichloroethylene (TCE) and a-pinene. Fittonia argyroneura (nerve plant) was effective in removing benzene, toluene and trichloroethylene. Ficus benjamina removed octane and a-pinene and Polyscias fruticosa ( Panax) removed octane only. There were no patterns of VOC removal based on taxonomic categories, however, the aroids (Araceae) generally did poorly, while the aralias (Araliaceae) generally performed better. The researchers suggest that for maximum removal of indoor pollutants, multiple plant species are required. Most of us spend the majority of our time indoors, but unfortunately, indoor air is 12 times as polluted as outdoor air. Also, as we succeed in building ever more energy-efficient buildings, the problem can only get worse. We need a large number of plants to create healthful living, working, and learning environments and we need to test more indoor plants for how well they remove additional pollutants. Tradescantia pallida and flower The researchers placed the plants into the following categories depending their overall pollutant removal efficiency: Superior Removal Efficiency: Hemigraphis alternata Hedera helix (ivy) Tradescantia pallida (purple heart) Asparagus densiflorus Hoya carnosa Intermediate Removal Efficiency Ficus benjamina Polyscias fruticosa (Panax) Fittonia argyroneura (nerve plant) Sansevieria trifasciata Guzmania sp. (a bromeliad) Anthurium andreanum Schefflera elegantissima (syn., Dizygotheca elegentissima) Poor Removal Efficiency Peperomia clusifolia Chlorophytum comosum (spider plant) Howea belmoreana (a type of Kentia palm) Spathophyllum wallisii (peace lily) Schefflera arboricola Codiaeum variegatum (croton) Calathea roseopicta Aspidistra elatior (cast iron plant) Maranta leuconeura Dracaena fragrans Ficus elastica (rubber plant) Dieffenbachia seguine (Dieffenbachia amoena) Philodendron scandens ssp. Oxycardium Syngonium podophyllum Epipremmum aureum ( Pothos) Pelargonium graveolens (a type of mint-scented geranium) Best Plants for Removing Individual Pollutants (in descnding order of effectiveness): Benzene: Hemigraphis alternata, Tradescantia pallida, Hedera helix, Fittonia argyroneura, Asparagus densiflorus, and Hoya carnosa Toluene: Hemigraphis alternata, Tradescantia pallida, Hedera helix, Asparagus densiflorus, Hoya carnosa, Fittonia argyroneura and Ficus Benjamina (These plants were more effective at removing toluene than benzene.) Octane: Hemigraphis alternata, Hedera helix, Ficus benjamina, Hoya carnosa, Asparagus densiflorus, Polyscias fruticosa Trichloroethylene(TCE): Hemigraphis alternata, Hedera helix, Tradescantia pallida, Asparagus densiflorus, Fittonia argyroneura, Hoya carnosa, Chlorophytum comosum (This plant had an intermediate TCE removal efficiency). a-Pinene: Hedera helix, Hemigraphis alternata, Asparagus densiflorus, Tradescantia pallida, Ficus bejamina, Hoya carnosa, Polyscias fruticosa Source: Yang, D. S. et al. “Screening of Indoor Plants for Volatile Organic Pollutant Removal Efficiency.” HortScience 44(5): 1377-1381. 2009.

New Research on Pollutant Removal by Indoor Plants

Paula Szilard

In research published in the August 2009 issue of HortScience, researchers at the University of Georgia screened indoor plants for their pollutant removal efficiency. They tested 28 plants frequently encountered in interiorscapes for how well they removed the volatile organic compounds (VOC’s) benzene, toluene, octane, trichlorethylene and a-pinene. These are all pollutants that are commonly found in petroleum based indoor coatings, cleaning solutions, plastic, tobacco smoke, exterior exhaust fumes leaking into buildings, paint, adhesives and building materials. At high concentrations they are actually harmful to plants.

Researchers conducted the study by unpotting the plants, rinsing off the potting mix and placing them in covered glass containers. They then piped in measured quantities of the pollutants and tested to determine how much of each had been removed at three and six hour intervals. Similar glass containers containing the potting mix and the pots only served as controls. The computations of removal efficiency of individual species were based on the amount of leaf area of the plants tested, therefore it stands to reason that a large plant with a lesser removal efficiency might still remove more pollutants than a small plant with a higher removal efficiency, simply because it has a lot more leaf area. Likewise, a lot of plants with poor removal efficiency might prove better than a few plants with high removal efficiency.

The results of the study were somewhat surprising. Of the 28 plants tested, Hemigraphis alternata, (a tropical ground cover with dark purple crinkly leaves sometimes known as red-flame ivy), Hedera helix (ivy), Hoya carnosa (the most commonly available hoya), Asparagus densiflorus (sometimes known as Asparagus meyersi, with shorter densely leaved, plume-like shoots) were the most efficient in removing all of these pollutants. Tradescantia pallida (Setcreasea pallida), another tropical groundcover with narrow purple leaves also known as purple heart showed superior removal of four of these five pollutants—benzene, toluene, trichloroethylene (TCE) and a-pinene. Fittonia argyroneura (nerve plant) was effective in removing benzene, toluene and trichloroethylene. Ficus benjamina removed octane and a-pinene and Polyscias fruticosa ( Panax) removed octane only. There were no patterns of VOC removal based on taxonomic categories, however, the aroids (Araceae) generally did poorly, while the aralias (Araliaceae) generally performed better.

The researchers suggest that for maximum removal of indoor pollutants, multiple plant species are required. Most of us spend the majority of our time indoors, but unfortunately, indoor air is 12 times as polluted as outdoor air. Also, as we succeed in building ever more energy-efficient buildings, the problem can only get worse. We need a large number of plants to create healthful living, working, and learning environments and we need to test more indoor plants for how well they remove additional pollutants.

Tradescantia pallida and flower

The researchers placed the plants into the following categories depending their overall pollutant removal efficiency:

Superior Removal Efficiency:

Hemigraphis alternata

Hedera helix (ivy)

Tradescantia pallida (purple heart)

Asparagus densiflorus

Hoya carnosa

Intermediate Removal Efficiency

Ficus benjamina

Polyscias fruticosa (Panax)

Fittonia argyroneura (nerve plant)

Sansevieria trifasciata

Guzmania sp. (a bromeliad)

Anthurium andreanum

Schefflera elegantissima (syn., Dizygotheca elegentissima)

Poor Removal Efficiency

Peperomia clusifolia

Chlorophytum comosum (spider plant)

Howea belmoreana (a type of Kentia palm)

Spathophyllum wallisii (peace lily)

Schefflera arboricola

Codiaeum variegatum (croton)

Calathea roseopicta

Aspidistra elatior (cast iron plant)

Maranta leuconeura

Dracaena fragrans

Ficus elastica (rubber plant)

Dieffenbachia seguine (Dieffenbachia amoena)

Philodendron scandens ssp. Oxycardium

Syngonium podophyllum

Epipremmum aureum ( Pothos)

Pelargonium graveolens (a type of mint-scented geranium)

Best Plants for Removing Individual Pollutants (in descnding order of effectiveness):

Benzene: Hemigraphis alternata, Tradescantia pallida, Hedera helix, Fittonia argyroneura, Asparagus densiflorus, and Hoya carnosa

Toluene: Hemigraphis alternata, Tradescantia pallida, Hedera helix, Asparagus densiflorus, Hoya carnosa, Fittonia argyroneura and Ficus Benjamina (These plants were more effective at removing toluene than benzene.)

Octane: Hemigraphis alternata, Hedera helix, Ficus benjamina, Hoya carnosa, Asparagus densiflorus, Polyscias fruticosa

Trichloroethylene(TCE): Hemigraphis alternata, Hedera helix, Tradescantia pallida, Asparagus densiflorus, Fittonia argyroneura, Hoya carnosa, Chlorophytum comosum (This plant had an intermediate TCE removal efficiency).

a-Pinene: Hedera helix, Hemigraphis alternata, Asparagus densiflorus, Tradescantia pallida, Ficus bejamina, Hoya carnosa, Polyscias fruticosa

Source: Yang, D. S. et al. “Screening of Indoor Plants for Volatile Organic Pollutant Removal Efficiency.” HortScience 44(5): 1377-1381. 2009.