VOCs are Volatile Organic Compounds which are released into the air from certain solids and liquids. These organic chemicals are common ingredients found in many household products. Paints, varnishes, furnishings all contain organic solvents, as do many cleaning, disinfecting, degreasing and cosmetic products.

Some VOCs are more harmful than others. Factors like level of exposure and length of time will also affect the extent and nature of he health problems. Some immediate symptoms include eye and respiratory tract irritation, headaches, dizziness and visual disorders. Some VOCs are suspected of causing or are known to cause cancer in animals and humans.

This website provides an excellent overview of this topic.

http://epa.gov/iaq/voc.html