Planting Healthier Indoor Air

Poor indoor air quality has been linked to health problems, especially in children. Asthma has reached epidemic proportions among multiple age groups and is considered the most common chronic disease in urban-dwelling children. The American Academy of Allergy, Asthma and Immunology Indoor Allergen Committee suggested in a 2010 report that allergists consider indoor air filtration to be part of a comprehensive strategy to improve respiratory health. 2 Air cleaners with HEPA filters have been shown to improve symptoms of asthma. 2 However, filtration systems and air purifiers do not reduce levels of all indoor air pollutants, and some types can actually aggravate the problem. For example, one study showed that some air purifiers raise indoor concentrations of ozone above safety levels established by the U.S. Environmental Protection Agency. 3 A more benign addition to air filtration could be the use of houseplants. In addition to basic photosynthesis that removes carbon dioxide and returns oxygen to the air, plants can remove toxicants from air, soil, and water in at least two ways. First, they can metabolize some toxic chemicals, releasing harmless by-products, and second, they can incorporate toxicants such as heavy metals into plant tissues, thus sequestering them. Data on plant-mediated indoor air quality come from experiments conducted by the U.S. National Aeronautics and Space Administration (NASA). As NASA researchers explored the possibilities of long-term space habitation, it became evident that the air in a tightly sealed space capsule would quickly become contaminated with volatile organic compounds (VOCs) and other chemicals released by the materials used to manufacture the capsule interior. 4 This is similar to the situation in newly constructed energy-efficient dwellings. If energy-efficient construction is not carefully designed to maintain indoor–outdoor air exchange, one unintended consequence can be increased concentrations of pollutants indoors. For example, in a study recently published in the American Journal of Public Health, Gary Adamkiewicz and colleagues used a simulation model to demonstrate that in homes with low air exchange rates and multiple sources of air pollution, up to 90% of exposure to fine particulate matter came from indoor sources. 5 Besides particles and VOCs, indoor air and dust can also contain brominated flame retardants, pesticides, toxic metals, and other pollutants. 6 For more than 30 years, B.C. " Bill " Wolverton, a retired civilian scientist for NASA, investigated the use of plants as air-and water-purifying systems for enclosed environments in space missions. Through his …