Durable and decorative as they are, spider plants tend to be taken for granted. According to a team of Penn State scientists, though, the plants may be performing a vital service: removing ozone from indoor air. That may also be true of
Durable and decorative as they are, spider plants tend to be taken for granted. According to a team of Penn State scientists, though, the plants may be performing a vital service: removing ozone from indoor air. That may also be true of snake plants and golden pothos.
Ozone is a paradoxical gas. In the upper atmosphere, it helps shield the planet from harmful ultraviolet radiation; thinning ozone layers over the poles have been a major environmental concern. At ground level, ozone is a bad actor, a major component of smog. It's also a worrisome indoor pollutant in offices and homes, with copy machines, laser printers, ultraviolet lighting and some electrostatic air purification systems as known or suspected sources. Human health consequences include pulmonary edema, lesions on lung tissue and other respiratory disorders.
The Penn State group, headed by Heather L. Papinchak and E. Jay Holcomb, published their findings in a recent issue of the journal HortTechnology. They chose spider plant, snake plant and golden pothos as test subjects because they were cheap and readily available. The experimental plants were grown in a greenhouse with a charcoal-filtered air supply system that kept ozone levels at 5 parts per billion - comparable to the average ozone emissions from a photocopier. Placing the plants in sealed chambers, the scientists pumped in ozone until a concentration of 500 ppb was reached, then measured how long it took for ozone levels to return to baseline.
For all three houseplant species, the ozone concentration fell faster than in plantless control chambers. There was no significant difference among the three species in ozone-removal rates.
How does it work? Papinchak and her colleagues suggest that the plants take in ozone through the stomata - pores - in their leaves and detoxify it on a cellular level. They say it wasn't clear whether total leaf area was a factor. Most houseplants evolved in the understories of tropical forests; it's been speculated that their ability to photosynthesize under low-light conditions contributes to more efficient processing of atmospheric gases.
The ozone study was a follow-up to earlier research by former NASA scientist B.C. Wolverton, beginning in the 1980s. In helping design space habitats, Wolverton tested a larger variety of houseplants for their ability to clean up indoor pollutants like formaldehyde, xylene, toluene and ammonia. These have been prime suspects in "sick building syndrome" cases. Formaldehyde is given off by synthetic materials in particleboard, floor coverings and curtains. Wolverton also says some computer screens and printers emit xylene and toluene.
Unlike the Penn State group, Wolverton reported that not all houseplants were equally effective against all chemicals. In general, palms and ferns removed higher levels of pollutants in their test chambers. His top performers were Boston fern for formaldehyde, areca palm for xylene and lady palm for ammonia. Dracaenas, including the popular 'Janet Craig' cultivar, and ficus plants also scored high, a