The word “unleaded” is ubiquitous at gas stations across the nation, thanks to the successful campaign to purge gasoline of toxic lead by the mid-1990s. Unfortunately, aviation fuel hasn’t received the same attention.

Avgas, as aviation fuel is commonly known, is the single largest source of lead emissions in the nation. There is no safe threshold for lead exposure. The EPA estimates that 16 million people live and 3 million children attend school near the 22,000 airports where avgas may be in use.

In 2006, Friends of the Earth petitioned the EPA, requesting that the agency make a determination that lead in avgas contributes to air pollution that may threaten human health and welfare. After six years of inaction, Earthjustice filed suit in 2012 to force the agency to deal with this public health problem. In 2014, the groups again petitioned EPA to declare that lead in aviation fuel is a danger to the public.