Neighborhoods within three-quarters of a mile of Hillsboro Airport contain lead levels up to 50 times higher than rural background, according to a peer-reviewed study published Aug. 8 in Communications Sustainability, a Nature Portfolio journal.
Researchers from Oregon State University and Portland State University used moss samples to measure lead concentrations and trace their chemical origin near both Hillsboro Airport and Troutdale Airport. Isotopic analysis confirmed aviation gasoline as the dominant local source of the contamination.
The findings hit close to home.
The six sampling sites closest to Hillsboro Airport's most active runway, all within about half a mile, showed lead concentrations ranging from 7.08 to 21.6 milligrams per kilogram, with a median of 15.3 mg/kg. That median is up to about seven times higher than other urban sites in the study area.
The study also found that airport-derived lead extends into residential areas up to 1.2 kilometers, roughly three-quarters of a mile, from the runways.
Hillsboro ranked No. 10 nationally
Using 2017 EPA National Emissions Inventory data, the study reported that Hillsboro Airport ranked 10th among all U.S. airports for annual lead emissions, producing 550 kilograms of lead that year. Troutdale Airport ranked 88th, producing 251 kg. The researchers chose 2017 data to avoid distortions from pandemic-era reductions in air traffic.
Both airports sit adjacent to residential neighborhoods, schools, daycares and parks. Census data cited in the study shows population densities near the airports range from about 2,765 to 12,523 people per square mile.
Nationally, the EPA estimates approximately 16 million people, including 3 million children, live or attend school within 1 kilometer of airports where aircraft burn leaded fuel.
City Council already acted
The Hillsboro City Council voted unanimously on July 21 to adopt Resolution 2930, urging the Port of Portland to speed the transition to unleaded aviation fuel at Hillsboro Airport. Several residents testified at that hearing in support.
"For decades, residents of Hillsboro and surrounding communities have been relentlessly subjected to aviation lead emissions on a daily basis," David Barnes told the council at the July 21 Resolution 2930 hearing, urging officials to advocate for their constituents' health.
The city is also conducting lead testing at Brookwood Library, Hidden Creek Community Center and Tyson Recreational Center, all near the airport.
Federal limits on local action
The Port of Portland says it supports the transition to lead-free fuel and participates in the FAA's EAGLE initiative, which aims to eliminate leaded aviation gasoline by 2030. However, the Port states that federal law currently prohibits it from banning or restricting the sale of leaded avgas on its own.
The FAA released its Transition Plan to Unleaded Aviation Gasoline in July 2026.
The study's authors noted that even after unleaded alternatives are adopted, elevated lead levels will likely persist in local soils due to decades of accumulation.
The study was led by Alyssa Shiel, Lauren Stalford and Christina Murphy of OSU's College of Earth, Ocean and Atmospheric Sciences, along with Oluwaseyi Aderinboye and Dean Atkinson of PSU's Chemistry Department. The same OSU team previously used moss biomonitoring in research that informed class-action lawsuits against Bullseye Glass and Precision Castparts for air pollution in Portland.
Residents concerned about lead exposure can contact Washington County Public Health or the Oregon Health Authority for information on blood and soil testing.
