Vapor Intrusion - The Intrusive Vapors in the Ground | Intrusion of Vapors

The accumulation of these compounds in a home due to vapor intrusion presents several potential hazards. Short term exposure to high levels of contaminants can cause health problems, breathing difficulties and even pose a safety hazard in the case of explosive compounds. High levels of pollutants can also produce foul odors in the home, which are most noticeable on the lower floor or in the basement. Long term exposure to low levels of contamination from vapor intrusion is believed to potentially cause chronic health conditions. Accumulation of airborne pollutants due to vapor intrusion requires swift and effective treatment to ensure the highest air quality indoors.

http://radonweek.wordpress.com/2012/02/10/vapor-intrusion/