Volatile Organic Compounds (VOCs)
http://www.parish-supply.com/volatile_organic_compounds.htm

TREE SELECTION COULD HAVE AN EFFECT ON AIR QUALITY
http://www.pollution.dk/voc.htm

Volatile Organic Compound http://www.cccfb.org/farms19.html

An organic compound, generally speaking, is a compound that contains carbon and hydrogen. Some examples of organic compounds are octane, butane, and sugar. Organic compounds that evaporate easily are called volatile organic compounds (VOCs).

When released into the atmosphere, VOCs contribute to ozone and smog formation. In
addition, VOCs can have direct adverse effects on human health. Volatile organic compounds in the atmosphere come from all combustible engines, industry, fuel spills, etc.
Certain other fumes, such as those released from industrial plants and print shops, also can contain significant amounts of VOCs.

Health effects of VOCs
In addition to contributing to ozone and smog formation, VOCs can have direct adverse effects on human health. Many VOCs have been classified as toxic and carcinogenic (cancer causing) and it is therefore unsafe to be exposed to these compounds in large quantities or over extended periods of time. Some health effects from overexposure to VOCs are dizziness, headaches, and nausea. Long-term exposure to certain VOCs, such as benzene, has also been shown to cause cancer, and eventually death.