Indoor Plants May Not Cure Sick Building Syndrome

PERTH, Australia, January 13, 2000 (ENS) - They may look beautiful but forget about buying a few indoor plants to improve the quality of the air in your home or office, says environmental scientist Peter Dingle of Murdoch University in Western Australia.

A variety of organic molecules known as volatile organic compounds (VOCs) have been found in office air and linked to sick building syndrome, a range of symptoms that leaves people feeling tired, irritable and unwell but with no specific illness.

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Corn plant imparts a touch of green to a New York City office. (Photo courtesy Earthborn Indoor Gardeners)
Furniture, carpeting, and cleaning products can contain dangerous chemicals like formaldehyde, polyethylene, and benzene, that can emit gases into the air. For example, formaldehyde is found in particleboard, some plywood, adhesives, fabrics, and some furniture.

Formaldehyde is a toxic chemical that can irritate the eyes, skin and throat. It is thought to cause nausea, dizziness and lethargy at levels as low as 50 parts per billion (ppb). It may also aggravate asthma and hay fever and is a potential carcinogen.

Aside from obvious moves such as improving ventilation and removing sources of VOCs, potted plants have been suggested as a potential solution to the problem - although evidence that they remove pollutants is sparse. "Everybody believes plants are the answer to sick buildings and indoor air pollution," says Dingle. "It's one of the great urban myths."

To test whether this particular myth has any basis in fact, Dingle and his colleagues examined the effects of plants on levels of formaldehyde.

Dingle and his colleagues measured formaldehyde levels in offices where the occupants had complained of poor air quality. They studyied 18 office buildings in Perth and 20 temporary buildings on the Murdoch University campus.

These structures are typically built using major sources of formaldehyde - pressed wood products such as plywood and some types of foam insulation.

Average levels of formaldehyde ranged from 10 ppb to 78 ppb in the office buildings. But concentrations in the temporary university buildings ranged from 420 ppb to 2,110 ppb - far in excess of the World Health Organization's safety standard of 82 ppb.

Dingle then set up five experimental cabins each with a floor space of eight square metres (86 square feet). Into each cabin, he placed five plants every two days until there were 20 plants in each cabin.

With up to 10 plants in a cabin, formaldehyde concentrations remained unchanged.

With 20 plants, average levels of formaldehyde were only reduced from 856 ppb to 761 ppb. If potted plants do help treat sick building syndrome, Dingle concludes, the effect is psychological. "They really make a place more comfortable and beautiful, but they do not clean the air of pollutants to any significant degree."

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Spider plants in the middle row blend into an indoor landscape. (Photo courtesy Michigan State University)
Jeff Llewellyn, an expert on indoor air quality with Britain's Building Research Establishment in Watford, says that the importance of such psychological factors shouldn't be underestimated. He also points out that the ability of plants to remove other pollutants has not been adequately studied, "Formaldehyde is but one pollutant," Llewellyn said.

Indoor plants are apparently useful in removing some pollutants. Research in the United States at the National Aeronautics and Space Administration's National Space Technology Laboratories in Mississippi has demonstrated the ability of common houseplants such as spider plants (Chlorophytum elatum var.vittatum) and golden pothos (Scindapeus aureus) to remove such indoor air pollutants. B.C. Wolverton, Ph.D., a NASA researcher, presented a report in 1985 that found formaldehyde and carbon monoxide were removed by spider plants and golden pothos from closed chambers.

Pollutant source removal or modification is an effective approach to resolving an indoor air quality problem when sources are known and control is possible. Routine maintenance of heating, ventilation and air conditioning systems such as periodic cleaning or replacement of filters is important.

Replacement of water stained ceiling tile and carpeting; institution of smoking restrictions; venting contaminant source emissions to the outdoors; storage and use of paints, adhesives, solvents, and pesticides in well ventilated areas, and use of these pollutant sources when no one is in the building are all recommended.

It is also important to allow time for building materials in new or remodeled areas to give off pollutants before the building is occupied.

Increasing ventilation rates and air distribution often can be a cost effective means of reducing indoor pollutant levels.

{The New Scientist contirubted to this report.}