By:   Julie Bawden-Davis

The air inside your home can contain a dangerous cocktail of harmful chemicals. Although many of these chemicals appear in miniscule amounts, when hundreds of them mix, they can form a "pea soup concoction that can create a variety of health problems, including respiratory disorders such as asthma," says Bill Wolverton, an environmental scientist and author of How to Grow Fresh Air.

That's a scary thought. We all want to provide a healthy environment for our loved ones, but short of leaving the doors and windows open all day, or buying an industrial filtration system, what can we do?

The answer, according to Wolverton, may be the low-tech houseplant.

For almost 20 years, Wolverton worked for NASA developing technology that would allow humans to live in a closed environment on the moon or Mars. Through this pioneering research, he says, he discovered that houseplants are the quickest and most effective filters of common, dangerous air pollutants such as formaldehyde, benzene, xylene and ammonia. "We've found that plants literally suck these chemicals out of the air," says Wolverton.

Plants clean indoor air in two ways, he says. They absorb pollutants into their leaves and transmit the toxins to their roots. There the toxins are transformed into a food source for the plant. Plants also emit water vapors that create a pumping action that pulls dirty air down around the plant's roots, where it is also converted into food for the plant.

The air-cleaning ability of houseplants is especially needed in office buildings, where workers commonly suffer from "sick building syndrome", thanks to toxic fumes emitted by office machinery, furniture and other sources.

"The closer the plant is to you, the better," says Wolverton. "Even in large open rooms, a plant within your personal breathing zone really improves the air you breathe." In his book, Wolverton identifies the top 50 plants for cleaning air and rates them on their ability to remove chemical vapors, transpiration rate, difficulty of cultivation and resistance to pests.

Though some plants are better at filtering air and transpiring than others, Wolverton says, all help clean the air. "If your favorite plant is lower on the list," he says, "then just put more of them in your house and office."

Top 10 Plants To Fight Indoor Air Pollution

Arrowhead vine (Syngonium podophyllum): This is an easy-to-grow plant with green-white or green-silver leaves that are long and arrow-shaped when young.

Provide with low to bright light and keep evenly moist. Mist frequently and keep pruned to avoid legginess. It rarely has pests, but watch for spider mites. Feed monthly with a well-balanced fertilizer.

Bamboo palm (Chamaedorea Seifrizii): This bamboolike palm gives a tropical look to your home. Eventually reaching six feet, it is easy to grow and tolerates low to bright light conditions. When transplanting, use a cactus mix, because this plant needs a well-draining soil.

Allow soil to approach dryness between waterings. Fertilize with a well-balanced fertilizer every two to three months and watch for mealybugs, scale and mites. If these pests do appear, treat plant with horticultural oil. Mix the oil with water according to package directions and spray on tops and bottoms of leaves.

Boston fern: This plant's stiff fronds arch out and then droop, making it an excellent hanging plant. Give it medium to bright light at the top, or no new growth will appear.

Keep plant constantly moist, but not soggy, and feed every watering with fertilizer at 1/4 strength. Mist regularly and remove yellow fronds when they appear.

Draceana 'Janet Craig': This is one of the best plants for removing trichloroethylene, which comes from such substances as solvents, varnishes and glues. It can reach 10 feet tall and makes a dramatic statement in the home with its long dark-green leaves.

Provide bright to medium light and water when the top inch of soil is dry. Feed every two to three months with a well-balanced fertilizer.

English ivy (Hedera Helix): This plant is not easy to grow indoors but is often used for topiaries. Although it tolerates low to bright light, it is susceptible to insects, especially spider mites and thrips.

To prevent such infestations, provide the plant with good air circulation and inspect the underside of leaves weekly for pests. Mist regularly, especially when the air is very dry. Fertilize monthly with a half- strength solution and water when the plant is approaching dryness.

Ficus alii (Ficus macleilandii 'Alii'): With its slender green leaves and upright treelike growth habit, this plant brings the outdoors inside. It is virtually pest free and will tolerate medium to bright light.