Nearly two decades of testing by the National Aeronautics and Space Administration (NASA) in the USA has shown that several common varieties of plants can absorb indoor air pollutants such as benzene, formaldehyde, and tricholoroethlene, according to an article in The Age (21/8/1991).

NASA's interest in the plants grew out of efforts to develop biological life-support systems in enclosed space habitats. It was found that the air inside Sky Lab 3 was contaminated with more than 100 chemicals, some of which are know to, or strongly suspected of, causing a variety of cancers and other adverse health effects.

Test inside sealed chambers revealed that Aloe Vera removed 90% of the formaldehyde in its chamber, Dracaena marginata reduced benzene concentrations by 80%, and Spathyphyllum (peace lily) cut trichloroethylene concentrations by 50%.

The chemicals are absorbed into plants through tiny pores on the underside of the leaves. As well, bacteria associated with the roots help to beak down contaminants. No one plant can reduce all contaminants, however, so a variety of plants is required to remove a range of chemicals. It is suggested that one or two plants per 10 square metres is usually sufficient to reduce indoor pollution. Air venting may also be required in severely affected rooms.

The following list indicated which plants can be used to reduce the air concentrations of three common indoor pollutants.

Formaldehyde
Sources: foam insulation, plywood, clothes, carpeting, furniture, paper goods, household cleaners.

Suitable plants: philodendron, spider plant, golden pothos, chrysanthemum, Sansvieria (snake plant).

Benzene
Sources: tobacco smoke, petrol, synthetic fibres, plastics, inks, oils, detergents, rubber.

Suitable plants: Hedera helix (English ivy), Dracaena marginata, chrysanthemum, gerbera, Spathyphyllum (peace lily).

Trichloroethylene
Sources: dry cleaning, inks, paints, varnishes, lacquers, adhesives.

Suitable plants: gerbera, chrysanthemum, Spathyphyllum (peace lily), Dracaena marginata.

Reprinted from Emerge, December 1991.

PS. NASA web page relating to this information can be found at http://www.zone10.com/wsdocs/tech/NASA/fyh.htm