Some Indoor Plants Release Harmful Gases

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The potted indoor plant next to your desk at home or at work could be less green than you thought. According to researchers at the University of Georgia’s Department of Horticulture, some potted plants emit harmful gases called volatile organic compounds (VOCs) that have the ability to make you ill.

According to the Environmental Protection Agency, volatile organic compounds are released as gases from certain solids or liquids that are commonly found in homes, offices, and other buildings. Examples of materials that can contain harmful gases include paints, cleaning products, particleboard, plywood, draperies, pesticides, copiers and printers, glues, adhesives, permanent markers, photographic materials, and lacquers. Concentrations of many VOCs are up to ten times higher indoors than outdoors.

In 1989, a report was released by the National Aeronautics and Space Administration (NASA) in which researchers stated that certain indoor plants were effective at removing harmful gases from the air. They arrived at this conclusion by placing various plants inside a sealed chamber, injecting the chamber with gases such as formaldehyde, benzene, and carbon monoxide. They concluded that the leaves, roots, and soil bacteria of specific indoor plants are important in removing trace levels of toxic gases from the air. Some of the one dozen plants studied by NASA include the snake plant, peace lily, bamboo palm, English ivy, pot mum, and corn plant.

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The results of this study have been widely repeated and circulated for two decades, even though there have been more recent studies designed to mimic real-life situations, in which harmful gases such as formaldehyde are continuously released. In these studies, indoor plants were able to metabolize a much lesser amount of the gases than seen in the NASA studies.

In this latest study, rather than measure the amounts of gases metabolized by plants, the researchers evaluated the levels of volatile organic compounds that were released. They chose four popular indoor plants—peace lily, snake plant, weeping fig, and areca palm—and placed them in glass containers that were connected to charcoal filters and traps for the emitted gases. They registered a total of 23 VOCs from the peace lily, 16 from areca palm, 13 from weeping fig, and 12 from snake plant.

Some of the harmful gases were released from the pesticides and microorganisms living in the soil, as well as from the plastic pots that were holding the plants. More gases were released during the day than at night. The scientists concluded that “while ornamental plants are known to remove certain VOCs, they also emit a variety of VOCs, some of which are known to be biologically active.” For now, there are not enough data concerning how long these compounds last in the environment and the extent or degree of their impact on human health. One way to perhaps reduce the amount of harmful gases released by potted indoor plants is to use organic soils and clay containers.

SOURCES:
Wolverton BC et al. Interior Landscape Plants for Indoor Air Pollution Abatement, 1989 September NASA MS 39529-6000
Yang, DS et al. HortScience 2009; 44:396-400

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