A newly published study in Nature Portfolio’s Communications Sustainability puts the lead from the airplanes debate in Hillsboro to rest. The peer-reviewed work provides definitive scientific data linking airborne lead deposition in Hillsboro neighborhoods directly to piston-engine aircraft operations at Hillsboro Airport (HIO).
The research, conducted by scientists from Portland State University and Oregon State University, moves the community discussion from anecdotal concern to hard physical evidence by identifying the specific isotopic “fingerprint” of leaded aviation fuel (avgas).
What the Study Found: Hard Numbers Near the Runways
Researchers used passive biomonitoring with epiphytic tree moss (Orthotrichum lyellii), paired with multi-collector mass spectrometry, to measure multi-year lead accumulation within a 2-kilometer radius of Hillsboro Airport. Here are the findings using pure science.
- Up to 50x Rural Baseline: Tree moss samples collected within 0.5 to 0.7 kilometers (roughly 1,600 to 2,300 feet) of the primary runway exhibited lead levels ranging from 7.08 to 21.6 mg/kg (ppm), with a median of 15.3 mg/kg. This is up to 46.7 times higher than rural northwest Oregon baseline levels (0.463 mg/kg) and nearly 7 times higher than the general Portland urban baseline (3.24 mg/kg).
- A Steep Geographic Gradient: Lead concentrations declined sharply with increasing distance from the airport. By roughly 1.4 km (under one mile) out, moss lead concentrations leveled off toward typical urban background levels (around 2.0 mg/kg).
- The Isotopic “Smoking Gun”: The study didn’t just measure total lead; it analyzed four stable lead isotopes ($^{204}\text{Pb}$, $^{206}\text{Pb}$, $^{207}\text{Pb}$, and $^{208}\text{Pb}$). The samples closest to the runway showed distinct, non-radiogenic isotope ratios ($^{206}\text{Pb}/^{207}\text{Pb} = 1.1387 – 1.1513$) that clearly separated modern tetraethyllead in aviation gas from historical automotive exhaust and legacy lead paint. The distinct avgas signature was traceable up to 1.2 km away.
- Schools and Daycares: Three samples were collected near local schools and childcare centers (0.88 km, 1.3 km, and 1.7 km from the airport). While their total concentrations fell into normal residential ranges (2.00 to 3.45 mg/kg), the site at 0.88 km showed measurable isotopic input from aviation fuel.
Understanding the Numbers: Do They Exceed Federal and EPA “Safe” Levels?
When reporting on environmental lead, comparing moss data to federal safety limits requires specific context. We want to be clear and not alarm folks unnecessarily, so we dug into the highest-level agency standards we have:
- Moss Concentrations vs. Soil/Air Standards: The study measured lead in tree moss tissue (expressed in mg/kg or ppm). Regulatory criteria from the EPA, such as the National Ambient Air Quality Standard for airborne lead (0.15 micrograms per cubic meter over a 3-month average) or federal residential soil clearance levels (400 parts per million, with newer guidance targeting 200 parts per million or lower for bare soil play areas), apply to air filter volumes and soil samples, not plant tissue.
- “No Known Safe Level”: As both the EPA and the CDC emphasize in the study’s background, there is no biologically safe threshold for lead in human blood. Even very low blood lead levels damage cognitive development, lower IQ, and contribute to behavioral issues in young children.
- The 2023 EPA Endangerment Finding: In October 2023, the EPA issued an endangerment finding under the Clean Air Act, concluding that lead emissions from piston-engine aircraft endanger public health. Nationwide, piston-engine aircraft account for roughly 70% of airborne lead emissions. In federal emissions inventories, Hillsboro Airport has regularly ranked among the top 10 to 20 largest airport lead emitters nationwide (logging approximately 550 kg of lead emitted annually during normal operational years).
KGW Released this story just before our story broke-
View this post on Instagram
Grounding the Risk: How Exposure Actually Occurs
The best information we can source, as well as the study itself, indicates that Lead emitted into the air eventually settles onto surfaces and binds to bare topsoil. The primary health risk is not from walking outside and inhaling a single plume; rather, it stems from cumulative ingestion over time.
Because small children engage in frequent hand-to-mouth activity, the main pathways into the body are:
- Tracking contaminated outdoor dirt inside as household dust.
- Playing directly in bare, dry soil where dust can be kicked up or swallowed.
- Ingesting unwashed garden produce grown in contaminated soil.
Practical, Non-Alarmist Precautions for Hillsboro Residents
Public health authorities (including the Oregon Health Authority and OSU Extension Service) recommend simple, low-cost household practices that drastically reduce exposure risks while not upending daily routines:
- Adopt a “Shoes-Off” Policy at Home: Because the primary route of exposure is outdoor soil migrating indoors, leaving shoes at the entryway prevents lead-bearing particles from being tracked onto carpets and floors.
- Damp-Clean Indoor Surfaces: Use wet wipes, damp microfiber cloths, or wet mops on hard surfaces, window sills, and uncarpeted floors. Dry dusting or dusting tends to recirculate fine particles back into the breathing zone.
- Handwashing Routine: Ensure children wash their hands and faces thoroughly after playing outdoors, especially before snacks and meals.
- Keep Bare Soil Covered: If you live close to the airfield and have open patches of bare dirt in play areas, cover them with grass turf, bark chips, mulch, or gravel to prevent direct contact and wind-blown dust.
- Smart Gardening Practices:
- Wash all garden produce thoroughly before eating, peeling root vegetables where practical.
- For vegetable gardens near busy areas or within a mile of the airport, use raised garden beds filled with clean, imported compost and potting soil.
- Residents can submit soil samples to certified local labs or county extension testing clinics to check exact parts-per-million soil levels before planting directly in the ground.
- Routine Pediatric Screening: Families with toddlers or young children living within 1 km of the airport perimeter can request a routine blood lead test during regular pediatric well-child checkups.
Regulatory and Community Outlook
The findings arrive as federal and local entities manage the phase-out of leaded aviation fuel:
- The FAA’s EAGLE (Eliminate Aviation Gasoline Lead Emissions) initiative intends to eliminate leaded avgas nationwide by the end of 2030. Unleaded formulations (such as G100UL and Swift UL94) have received regulatory clearances, though supply-chain availability and widespread airport adoption remain gradual.
- At the local level, both the Port of Portland (which operates HIO) and the Hillsboro City Council have enacted transition plans and resolutions to accelerate the availability of on-site unleaded fuel infrastructure, balancing flight training demands with neighborhood environmental safety.
Fast Facts for Hillsboro Families: The Core Takeaway:
The study confirms that lead settles into soil near the airport, but exposure is preventable with basic dust and dirt control. The Primary Exposure Route: Outdoor dirt tracked inside that gets onto toddlers’ hands and toys.Top 3 Action Steps:Take shoes off at the door.Wash hands after playing outside.Grow home vegetables in raised garden beds.Peace of Mind: Ask your pediatrician for a routine blood lead screening at your child’s next checkup.
Please refer any questions you have to your Health professionals. The Oregon Health Authority and the City of Hillsboro are aware of this, and our City Council is pushing for leaded avgas to be phased out by 2030.
Read the full study and story right here: https://www.nature.com/articles/s44458-026-00130-x#Fig6
Concerned about the reporting of this lead study, I became alarmed when huge clouds of dust were being created by mowing and clearing of the open Hillsboro Airport property and if disturbed lead is being spread via air currents into the surrounding non-airport areas including the Brookwood Library and residential zones. After asking on Nextdoor what others thought, one reply by a very forward thinking individual included researched information about the consequences of digging in lead contaminated soil, etc. Another responder who is in the Meed Rd area also described concerns about the dust kicked up by site work for industrial and data center construction. This is a major escalation of the Lead issue and touches not only regulation of HIO operations but also the continuing construction being done north of Brookwood between Jackson School and Sewell. Is this Hillsboro’s Love Canal?