Looking for a respected authority on the top air-purifying houseplants? Will NASA do? In 1986, the National Aeronautics and Space Administration (NASA), in conjunction with the Associated Landscape Contractors of America, determined that several common houseplants effectively removed the toxins most frequently associated with "sick building syndrome." The study--which focused on the toxins benzene, formaldehyde and trichloroethylene--concluded that a total of 15 to 18 of any of their recommended plants would purify the interior of an 1,800-square-foot house.
The Department of Health and Human Services considers benzene a serious cancer-causing agent. Linked specifically to leukemia, Hodgkin's disease and lymphoma, benzene turns up in many detergents, plastics and pesticides. The NASA study found only two flowering plants, the Gerbera daisy and the indoor pot Mum, to be effective benzene fighters. Both are considered short-lived house plants, however. Replace them every few months. Keep the daisies and mums out of direct sunlight. Water mums several times a week, but allow the daisies to dry out between watering sessions.
"Warneckii" dracaena, a member of the dramatically-foliaged Dracaena family, can grow as high as the ceiling if left unpruned. It will tolerate low light and low humidity, but to bring out the variegation on its swordlike leaves, expose it to strong lighting. Keep the soil moist but not over-watered, and fertilize every two weeks. Peace lily, a short plant which rarely flowers, needs high humidity, direct sunlight (although not a southern exposure) and average temperatures.
Bamboo palm--the classic house or office plant--requires little light or humidity. Feed monthly or bimonthly, and give it room to reach its ultimate height of eight or nine feet. English ivy, which should be kept away from children and pets, requires a support structure or plenty or room to trail from a hanging pot. Keep it only lightly watered, and give it in indirect sunlight or under fluorescents.
Mother-in-law's tongue gets that whimsical name from its extremely narrow, pointed and upright foliage. Also known as snake plant, the medium-height botanical should be fed and raised in a similar manner to African violets. It thrives on bright indirect sunlight but dislikes overwatering.
The dangers of formaldehyde--a frequent ingredient in wood paneling, plywood and particleboard---range from minor skin and respiratory irritation to severe lung injury and death. Fortunately, the easily grown spider plant ranks as one of formaldehyde's top foes. Most frequently used as a hanging plant, spider plant prefers humidity and average temperatures, but survives a fair amount of abuse. Turn the plant from time to time so that all of its legs have room to unfurl.
Another dangling botanical, pothos plant (also known as devil's ivy), grows either from a hanging basket or up a strong pole. Give it indirect sunlight and medium humidity. To grow "Janet Craig" or "Marginata" dracaena, follow the directions for "Warneckii" in the benzene section. Mother-in-law's tongue, another formaldehyde fighter, is also discussed in the benzene section.
According to the Colorado Department of Public Health and Environment, Trichloroethylene, or TCE, exists in several "removers" -- paint remover, rust remover, grease remover, spot remover and other heavy-duty cleaning liquids. The U.S. Environmental Protection Agency found that exposure to TCE can likely become a cancer risk. Other risks include damage to the immune and central nervous systems, and kidney and liver damage, and problems with fetal development.
The group of plants NASA found to be best at purifying this toxin -- Gerbera daisy, "Marginata" and "Janet Craig" dracaena, peace lily and bamboo palm -- are discussed in the benzene and formaldehyde sections.