Formaldehyde Removal by Plants

Dr Bill Wolverton, NASA Research, 1989

In 1990 the Plants For Clean Air Council and Wolverton Environmental Services, Inc. began to co-sponsor research that continues to expand upon the earlier NASA research (1989). Fifty houseplants were tested for their ability to remove various toxic gases from sealed test-chambers. Because formaldehyde is the most commonly found toxin in indoor air, the ability to remove this substance from the air was used as the standard for rating these plants. Formaldehyde has provoked more public, regulatory and scientific controversy during the past 15 years than any other substance. Numerous sources of formaldehyde are present in the buildings we inhabit. It is found in various resins and is used to treat many consumer products, including refuse sacks, paper towels, facial tissues, fabrics, permanent-press clothing, carpet-backing, flooring-coverings and adhesives. Formaldehyde is released by gas cookers and is found in tobacco smoke. It is also used in building materials such as plywood, chipboard and panelling. Both plywood and chipboard are used extensively in the manufacture of domestic and office furniture and fittings.

Numerous adverse health problems have been ascribed to formaldehyde exposure, ranging from well-documented effects such as eye, nose and throat irritation, to more controversial claims including asthma, cancer, chronic respiratory diseases and neuropsychological problems. Although evidence of cancer formation is unequivocal, the extrapolation of these results to humans has been controversial.

One concern voiced by those sceptical of these findings centres around the belief that if plants continually absorb toxins from the air, once absorption capacity is reached, the plant will die and release all of the toxins back into the air. To address these concerns, the ability of the Lady Palm (Rhapis excelsa) to remove formaldehyde released from sections of panelling was tested. Two chambers were used in these experiments. The first chamber held a Lady Palm and two sections of panelling made from urea-formaldehyde resins. The second (control) chamber held only two sections of panelling and
a beaker of water, to help equalise the humidity levels in the two chambers. Plant transpiration naturally increased the humidity in
the first chamber.

The Lady Palm not only removed formaldehyde fumes, but its removal rate improved with exposure time. Interestingly there was no apparent damage to the plant.This phenomenon indicates that plants play a major role in delivering airborne toxins to microbes living around their roots, which can then break down the toxin. The adaptation of microbes to this task is the key to houseplants becoming better fighters against air pollution.