These are the fumes you see and smell when pumping gas or opening a can of paint.  Volatile Organic Compounds (VOCs) are made from crude oil and include the BTEX group --  Benzene, Toluene, Ethylbenzene and Xylenes. 

Health Effects?

• Benzene - Anemia; decrease in blood platelets; increased risk of cancer
• Ethylbenzene - Liver or kidney problems
• Toluene - Nervous system, kidney, or liver problems
• Xylenes - Nervous system damage
• Contamination can occur in amounts as low as 5 parts per billion (5 red balls in a sea of 5,000,000,000)

How Did It Get There?

• Contamination of soil and groundwater at petroleum and natural gas production areas, gas stations and areas with underground and above-ground storage tanks
• Produced in large scale for industrial use as solvents and for manufacturing materials such as plastics and pesticides

What's From Gas Drilling?

• Used in oil-based drilling muds
• Potentially in fracking solution
• Component of diesel fuel (present in large quantities at drill sites)
• Often accompanies heavy industrial activity