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Expanded lead monitoring limited at airports

EPA calls for study at 15 airports

An Environmental Protection Agency (EPA) rule approved by the agency Dec.14 calls for a yearlong study of lead levels at 15 airports.

The rule revises the monitoring requirements for lead emissions from a variety of sources to better assess if areas are complying with the National Ambient Air Quality Standards (NAAQS). For most lead emitters, such as quarries, manufacturing facilities, or power plants, it lowers the threshold of lead production that will require monitoring. But the EPA said it did not have enough information to determine if it should lower the threshold for airports and is requiring the study at specific sites to gather data on airports’ contributions to an area’s ambient lead levels. Sites required to have air quality monitors do not necessarily exceed the NAAQS for lead.

The 15 airports to be studied are estimated to produce less than 1 ton per year of lead emissions, the current threshold for monitoring, but more than 0.5 tons, the revised threshold for other sites. They were chosen because of factors, such as prevailing winds and number of runways where piston aircraft operate, that the EPA believes make them likely to have higher lead concentrations in certain areas.

The states—not airports—will be responsible for monitoring, and, if an area is not in compliance with the NAAQS, for coming up with a plan to reduce ambient lead. The monitoring requirements at these airports will have no impact on current operations. But the EPA recognized in its rule that the states may not enforce any standard for aircraft or aircraft engine emissions that is not identical to an EPA standard. The EPA has no lead emission standard for piston aircraft.

“EPA recognizes that, if ambient air near an airport was found to be exceeding the standard, and EPA were to take such discretionary action, there would be limits under federal law as to the measures a state could propose to adopt in a state implementation plan. EPA may take such limits into consideration in determining what steps to take following an exceedance of the standard,” the rule explains.

The General Aviation Avgas Coalition, which includes AOPA, is working to add a “very low-lead” (VLL) grade to the existing 100LL fuel specification that would have a maximum lead content 20 percent lower than 100LL. VLL would be a “drop in” fuel in that it would match all of the parameters of the existing fuel, including octane, and would not affect engine performance or any other aspect of aircraft operations. This could potentially be a tool for airports to use in addressing state implementation plans if they are found to be in non-attainment of the NAAQS.  

Separate from the issue of the NAAQS, the EPA published an advance notice of proposed rulemaking (ANPR) on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline in April that described considerations regarding possible engine emission standards for piston aircraft and requested comment on approaches for transitioning the fleet to unleaded avgas. The agency mentioned this step in its lead monitoring rule, adding that it is working with the industry and the FAA.

“The EPA and FAA are working with industry to evaluate alternatives to leaded avgas,” it said. “As part of this assessment, EPA and FAA are also considering safety, fuel supply, and economic impact issues including effects on small business.”

In its response to questions in the EPA’s ANPR, the GA Avgas Coalition urged the EPA to base its decisions related to GA’s use of avgas on sound, factual data. The study of certain airports’ ambient lead will increase the agency’s understanding of how much or how little lead airports contribute to the overall level in an area, providing data for one small piece of the puzzle.

Airports Selected for Monitoring Study

Airport County State

Merrill Field



Pryor Field Regional



Palo Alto Airport of Santa Clara County

Santa Clara



San Diego



Santa Clara


Gillespie Field

San Diego


San Carlos

San Mateo


Nantucket Memorial



Oakland County International





New York



New York

Stinson Municipal



Northwest Regional



Harvey Field



Auburn Municipal



AOPA ePublishing staff
AOPA ePublishing Staff editors are experienced pilots, flight instructors, and aircraft owners who have a passion for bringing you the latest news and AOPA announcements.
Topics: Advocacy

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