The sources of potential air emissions associated with hydraulic fracturing are temporary in nature. Fracking operations utilize large amounts of horsepower, normally provided almost exclusively by diesel engines. There are federal, state, local and tribal requirements regarding air emissions that apply to oil and gas operations.
...the measured and estimated air pollution levels did not reach levels that have been observed to cause adverse health effects.
Federal regulations that have a direct impact on controlling emissions from fracturing operations include the Standards of Performance for Stationary Compression Ignition and Spark Ignition Internal Combustion Engines (NSPS) and Reciprocating Internal Combustion Engine (RICE) NESHAP rules, which regulate new, reconstructed and existing stationary engines. In general, these rules apply to most internal combustion engines regardless of horsepower rating, location or fuel.
The EPA typically delegates implementation of air regulations to state and tribal agencies. This delegation of authority can include rule implementation, permitting, reporting and compliance. Any state with delegation of authority can pass more restrictive rules, but they are prohibited from passing a rule that is less stringent than the federal rule.
As with water protection maintaining air quality is not something that just happens, engines must be tuned up, seals must be checked. But with proper safeguards in place fracking operations pose no threat to local air quality.