Week of 6/18/2006

Dear EarthTalk: Do houseplants really help to clean indoor air?

—Jackson Schlemmer, London, England

One positive result of the 1970s energy crisis was the development and widespread adoption of improved insulation materials to maintain indoor energy efficiency. Unfortunately, however, many of these materials have compromised indoor air quality due to their tendency to "off-gas" various airborne toxins, including formaldehyde, trichloroethylene (TCE), benzene and other volatile organic compounds (VOCs).

Much of the synthetic carpeting, upholstery and paint used indoors also contain sometimes noxious gases that get trapped inside air-tight homes and offices and which can build up gradually over time. And most synthetic air fresheners only make matters worse, adding even more harmful VOCs to the indoor air. With most people spending upwards of 90 percent of their time indoors, it may be no coincidence that cases of asthma and other respiratory diseases have been on the rise in recent years.

The unlikely hero in this scenario may in fact be the humble houseplant. In a landmark 1984 National Aeronautics and Space Administration (NASA) study, initially commissioned to find ways to clean air in space bases and vehicles, researcher Bill Wolverton found that some common houseplants actually cleaned polluted indoor air. He found that philodendrons and golden pothos excelled at stripping formaldehyde from the air, gerbera daisies and chrysanthemums wiped out excessive amounts of indoor benzene, and pot mums and peace lilies absorbed a toxic degreasing solvent known as TCE.

A later NASA study, also conducted by Wolverton, saw houseplants removing up to 87 percent of toxic indoor air within 24 hours. And a 1994 German study reported that one spider plant could cleanse a small room of formaldehyde in just six hours. Further, English ivy, bamboo palm and snake plants have been shown to be effective in removing cigarette smoke as well as noxious odors from carpeting and chemical-laden household cleaners.

Just how can a houseplant be so good at cleansing the air? The reason lies in its basic ability to absorb carbon dioxide from the air while releasing oxygen as part of the photosynthetic process. Houseplants are essentially doing indoors what other plants and trees ordinarily do outdoors.

To maximize the benefits of houseplants in cleaning indoor air, it is generally recommended to use one plant for every 100 square feet of indoor space. Besides those plants mentioned above, other good indoor air cleaners include palms, ferns, dracaenas, corn plants, weeping figs, dumb canes, orchids, arrowheads, dwarf bananas and Chinese evergreens.

For its part, the U.S. Environmental Protection Agency (EPA) recommends opening the windows and letting in some good old-fashioned fresh air as the best antidote to breathing in off-gassed airborne toxins in both homes and offices. But many modern buildings do not permit such exchanges between indoor and outdoor air, and it is in just these situations where houseplants can really make the difference.

CONTACT: Plant-Care.com; www.plant-care.com/indoor-plants-clean-air-1.html.


Dear EarthTalk: Why do modern bacteria "resist" antibiotics, confounding medical treatment?

—Hugo Mestres, Seattle, WA

Antibiotics have played a profoundly important role in staving off bacterial infections since Alexander Fleming first discovered them in 1927. But the effectiveness of these so-called miracle drugs has waned in recent years as some of the very bacteria they are meant to control have been mutating into new forms that don't respond to treatment. Many medical experts blame this phenomenon on both the misuse and overuse of antibiotics in recent years in both human medicine and in agriculture.

Doctors first noticed antibiotic resistance more than a decade ago when children with middle ear infections stopped responding to them. Penicillin as a treatment for strep has also become increasingly less effective. And a recently-discovered strain of staph bacteria does not respond to antibiotic treatments at all, leading medical analysts to worry that certain "super bugs" could emerge that are resistant to even the most potent drugs, rendering some infections incurable. The U.S. Centers for Disease Control and Prevention (CDC) calls antibiotic resistance one of its "top concerns" and "one of the world's most pressing health problems."

One large part of the problem, according to the CDC, is the tendency for people to take antibiotics to fight viruses, which they cannot do. Antibiotics fight bacteria, not viruses, and will not fight colds, flu, bronchitis, runny noses, or sore throats not due to strep. Nonetheless, says CDC, "more than 10 million courses of antibiotics are prescribed each year for viral conditions that do not benefit from antibiotics." To address this, a growing number of doctors, including Dr. Randel Cardott, an internist with Iowa's Genesis Convenient Care, are advocating a "wait-and-see" approach to prescribing antibiotics, especially in cases like middle ear infections that sometimes prove to be viral and not bacterial in origin. Cardott says that European physicians have taken this approach for years with no adverse effects.

Scaling back on antibiotics for human maladies won't address the whole problem. Farmers and ranchers use antibiotics heavily, too. In North America, industrial beef, pig and poultry farming is a big unsanitary business, and antibiotics are used extensively to ward off diseases and also for non-medical reasons, such as to promote growth. In fact, the Union of Concerned Scientists (UCS), a non-profit research and advocacy group, estimates that some 70 percent of all antibiotics are used as additives in the feed given to healthy pigs, poultry and cattle. These drugs leave the animals" bodies as waste and work their way into local water supplies, as well as right into the food chain. "Nonetheless," says UCS, "agribusiness and the pharmaceutical industry are fighting hard to thwart restrictions on the use of antibiotics in agriculture."

Keep Antibiotics Working, a non-profit dedicated to reducing antibiotics overuse in agriculture, advocates phasing out unnecessary antibiotics in healthy livestock and poultry. In lieu of Congressional action along these lines, the group is encouraging meat wholesalers and retailers to voluntarily stop buying or selling meat that has been produced using antibiotics for purposes other than treating sick animals. Consumers looking to avoid antibiotics in meat should seek out organic offerings at natural foods markets.

CONTACTS: UCS, www.ucsusa.org/food_and_environment/antibiotics_and_food/; Keep Antibiotics Working, www.keepantibioticsworking.com.