Sunday, September 6, 2009

Plants + VOCs

A recent, somewhat hyperbolic title from Treehugger, "Bad Green: Some Indoor Plants Release Volatile Organic Compounds" provides a snippet from some recent research that mention, gasp, that plants, particularly indoor ones, release volatile organic compounds (VOCs). It's a strange conceptual notion indeed, as there has been much research and information on the ability of indoor plants to improve air quality - including removal of VOCs and reduction of sick-building syndrome. So should we chuck the plant on the desk, and more broadly stop any notion of incorporating plants into buildings in significant ways? Probably not.


:: Killer Peace Lily - image via Treehugger

Some explanation "But at least four popular varieties of house plants emit their own VOCs, according to the University of Georgia's Department of Horticulture. Scientists there studied plants in glass jars and found 23 VOCs in the Peace Lily, 16 in the Areca Palm, 13 in the Weeping Fig and 12 in the Snake Plant. Sources included pesticides used in production of the plants, micro-organisms living in the soil and the plastic pots the plants called home, researchers say. The emission rates were higher during the day than at night, and several of the VOCs detected are known to harm animals."

It's not necessarily big news that plants give off VOCs... as plants are organically based and release compounds that are volatile (i.e. they vaporize readily into the air) through the normal process of metabolism. In fact one of the more readily occurring VOCs in nature is methane, which is produced in large quantities in wetlands. While not necessarily toxic, it is a player in global warming, so we should probably indict this as well while we're at it.

The difference between naturally occurring VOCs and synthetics are . Also a review of the study results identified that the primary VOCs from indoor plants were terpenoids, which are a somewhat innocuous form that provides a number of uses - and are particularly descriptive in having strong aromas. For instance the smell of such items as cinnamon, cloves, ginger, and eucalyptus is caused by the terpenoids present in these plants. Without these our sensory world would be much more bleak.


:: terpenoids look scary in molecular form - image via Wikipedia

Conversely a number of VOCs we are commonly bombarded with indoors, particularly in new construction, are related to
paints, adhesives, solvents, cleaning agents, caulks, wood products, carpets and sealants, and their lovely sounding components of toluene, styrene, xylene and ethylbenzene. As it's easy to tell from a fresh walk down the halls of a new (even sometimes low-VOC green) building, as chemicals off-gas from these materials and invade our smell centers in negative ways, something foul is going on. And, as mentioned in the report, it is likely the major issues with VOCs and indoor plants come from off-gassing of worse compounds from the man-made plastic pots, and pesticides used in growing of the plants... as well as microorganisms in soils and growing media.

This is another compelling reason for a holistic transformation of the landscape and nursery industry to include the whole picture and not just assume that plants are good or bad. While this doesn't say that there isn't something to this idea of VOCs from plants (it's natural) - let's not jump to quick and overwrought conclusions about the perils of house plants without a bit of context and further exploration. I think the precautionary principal is fine, but to eliminate indoor vegetation without some more focused study on impacts is pretty poor form, particularly when many materials used in building and landscape construction are known to be bad, yet still are industry standard.

I'm willing to be that when the overall accounting is done, exterior plants and wetlands probably have a net benefit to our environment, and indoor plants will win out in the search for better indoor air quality. Just a hunch.

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