Tuesday, February 28, 2012

Indoor Air Pollution: Can Houseplants Help Clean the Air?

The EPA has noted the growing body of scientific evidence showing that the air within our homes and other buildings can be much more seriously polluted than the outdoor air, even in the largest and most industrialized cities. Why would that be? Our homes contain many potential sources of pollutants; some of these sources release gases or particles continuously. For many people, the health risks from indoor air pollution may be greater that those from pollution encountered outdoors.

Some of the sources of indoor air pollution are the myriad products found inside our homes that emit volatile organic compounds (VOCs). These compounds can be a significant component of indoor air pollution. Concentrations of many VOCs are consistently higher indoors than outdoors (up to ten times higher). Some VOCs are known or suspected carcinogens.  Many more can cause a whole host of more immediate health problems

Here are just a few potential sources of VOCs that can contaminate the air in your home:

  • Cabinetry, flooring or furniture made of certain pressed wood products, including particle board, hardwood plywood paneling and medium density fiberboard (MDF) can emit formaldehyde, a known carcinogen (MDF is recognized as being the highest formaldehyde-emitting pressed wood product).
  •  Household cleaning and disinfecting products can contain pesticides and formaldehyde, among many other VOC-emitting ingredients.
  •  Pesticides--in addition to those found in disinfecting products, pesticides can be tracked or drift into your home from lawn and garden products. Paradichlorobenzene, a commonly used active ingredient in moth repellents, is a known carcinogen.
  •  Synthetic air fresheners can contain a host of toxic ingredients that can pollute indoor air, they can also contribute to formaldehyde generation through chemical reactions when sprayed inside.
  • Dry-cleaned clothing emits perchloroethylene, a known carcinogen.
  •  Automobile emissions from attached garages contain formaldehyde, benzene (an extremely toxic chemical and known carcinogen) and carbon monoxide.
  • Carpeting and carpeting materials including backing, underlay and adhesives emit many VOCs. 

The most effective way to improve indoor air quality is to control and remove the sources of pollution.  For example, you can reduce VOCs by choosing cleaner, greener cleaning products; avoiding the use of toxic pesticides and synthetic air fresheners; and avoiding exposure to emissions from newly dry-cleaned materials.

But what about the pollution from sources that it may not be feasible to remove or replace, such as flooring, furniture or carpet? Improving ventilation to increase the amount of outdoor air coming in is another way to lower the concentrations of indoor air pollutants in your home. For example, opening windows and doors when the weather permits, and using exhaust fans in the kitchen and bathrooms.

Another way to improve air quality is to clean the air of pollutants or toxins.  A lot has been written about the ability of plants to filter pollutants out of indoor air.  Most authors reference a study published by NASA in 1989 that found that certain houseplants were very effective at removing three different VOCs, including benzene and formaldehyde, from indoor air. However, the effectiveness of plants in filtering pollutants from the air is not universally accepted. For example, the EPA report above states that “there is currently no evidence . . . that a reasonable number of houseplants remove significant quantities of pollutants in homes.” One of the issues is establishing the number of plants that would be required to filter the air in a certain amount of space.

However, more recent studies suggest that certain plants are indeed very effective at cleaning VOCs from indoor air. This Wall Street Journal article discusses some of those studies, including a 2009 University of Georgia study that identified five “super ornamental” plants that showed high rates of VOC removal.  The five were:

  • ·      Purple waffle plant
  •      English ivy
  •      Asparagus fern
  •       Purple heart plant
  •      Variegated wax plant

In this 2009 TED talk an Indian environmental activist discusses how three houseplants (Areca Palm, Mother-in-law’s Tongue and Money Plant) were used in an office building in New Delhi to clean and filter the air.

Finally, I found a lot of useful information in the book How to Grow Fresh Air:  50 Houseplants That Purify Your Home or Office by the principle investigator of the NASA study. (Note: it is available from the Carnegie Library; you can request it online).

The author explains how plants clean the air and provides a directory of 50 plants that are effective for this purpose, including information on how to care for them. The plants are rated on how well they remove chemicals from the air.  Some of the most effective are:

    • Areca Palm                                 Boston Fern
    • Lady Palm                                  Peace Lily
    •  Bamboo Palm                             Weeping Fig
    • Rubber Plant                               Gerbera Daisy
    •  Janet Craig                                  Florist’s Mum
    • English Ivy                                 Kimberley Queen Fern
    •  Dwarf Date Palm                       Corn Plant
    • Ficus Alii

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