The current National Ambient Air Quality Standard (NAAQS) for lead is significantly more stringent than the previous standard. Current regulations are believed to affect five airports, which have numerous operations from piston engine aircraft that use leaded aviation gas (avgas). On December 23, 2009, the U.S. Environmental Protection Agency (EPA) proposed to revise the ambient monitoring requirements for measuring airborne lead. The proposed regulation changes the lead monitoring threshold and may affect up to 73 airports. This revised threshold will be the basis for State Air Quality agencies requiring source-oriented monitors be installed near any applicable source, and it may require airports to be treated as any other source of lead when determining whether source-oriented lead monitoring is needed. The inputs used to determine applicability were based on a number of assumptions and can be improved by obtaining airport-specific information. The EPA has limited quantitative data to evaluate on-airport or off-airport ambient lead concentrations associated with airports. If this proposed regulation is enacted, airports would need to document applicability or work with state agencies to monitor ambient lead concentration of the surrounding air. Airport owners and operators may face future regulatory and resource impacts to quantify or mitigate emissions. As such, research is needed to assist airports in quantifying lead emissions from leaded avgas that accounts for applicable variables.