The increasing production of oil from shale rock formations has brought increased scrutiny on how this production effects the environment, including how it affects air quality.
Just as in other types of oil deposits, a by-product of the shale oil extraction is natural gas. One main concern for air quality is the amount of methane (a main ingredient in natural gas) that could leak into the atmosphere. If there is no infrastructure to transport the gas, it is flared at the well site in order to ensure that the gas is not released into the atmosphere. The amount of gas flared depends on the formation in which the well is drilled and the age of the well.
As you can imagine, nobody wants to waste gas and the industry is developing ways to utilize this resource for onsite power generation and other purposes.
EPA guidelines for air quality in the oil and gas industry:
A summary of shale oil and gas production, including air quality concerns from the Energy Information Administration: