For years, the fight over the future of Boulder Municipal Airport has centered on one big question: Should the city close it? The debate has mostly focused on the housing potential of the 179-acre site.
But another question is quietly taking shape, one that could determine what happens while the airport stays open: What about the lead?
Small piston-engine planes burn leaded aviation fuel at the city-owned airfield. Leaded gasoline was banned for cars nearly three decades ago. But aviation fuel for small aircraft still contains a lead compound that helps prevent engine knocking. The fuel powers most of Boulder’s airport activity, from flight schools and private pilots to gliders and research aircraft. Commercial jets already use unleaded fuel.
In 2023, the U.S. Environmental Protection Agency determined that lead emissions from piston-engine aircraft pose an “endangerment to public health,” citing studies linking even low levels of exposure to reduced IQ and cognitive function in children. No safe threshold has been identified. The EPA and the Federal Aviation Administration have pledged to eliminate leaded aviation fuels nationwide by 2030.
And now, under a Colorado state law passed last year, Boulder’s airport must offer unleaded aviation fuel by 2030, part of a growing push to eliminate one of the last major sources of airborne lead in Colorado. The law applies to airports in Boulder, Longmont, Erie, Centennial and Rocky Mountain Metropolitan Airport.
The city is now drafting a transition plan, due to the Colorado Department of Transportation by Jan. 1, outlining how it will make the switch. The plan will involve collaboration with the airport’s fuel provider and funding for new infrastructure, with details to be publicly available once the plan is submitted to the state.
“Boulder is currently working all angles to move towards a transition to unleaded fuel,” city spokesperson Aisha Ozaslan told Boulder Reporting Lab.
Ozaslan said the effort is also backed at the federal level by the EAGLE initiative — short for Eliminate Aviation Gasoline Lead Emissions — which calls for a nationwide transition to unleaded aviation fuel by 2030.
“At this point, we do not have additional details to share because we are still working through the process,” she said.
Meanwhile, the city’s Planning Board voted 5-1 last month to recommend that city council pursue a transition to unleaded fuels at Boulder’s airport as soon as possible.
The shift won’t be simple. Boulder will need a new fuel tank, a truck to dispense the fuel and pilots certified to modify their aircraft.
Elliot Dickerson, a glider pilot and board member of the Soaring Society of Boulder, said his group is ready. The gliding club uses motor planes to launch engine-less sailplanes, which then stay airborne using rising air. Their planes are already cleared for unleaded fuels. “We have long wanted to bring unleaded fuel to the airport,” he told Boulder Reporting Lab. He estimates that a new tank would cost around $50,000 and expects the expense to be covered by the Colorado Department of Transportation.
The state has earmarked about $1.5 million a year in grants to facilitate new infrastructure or cover the price gap for unleaded fuel — currently about $1.92 per gallon, according to Zach Gabehart, Centennial Airport’s environmental manager.
Centennial is the first and only airport in Colorado to sell unleaded fuel, which now accounts for roughly 20% of its sales. Some pilots, Gabehart said at a Boulder event in August called “Lead Overhead,” have reported overheating issues in summer and switched back to leaded fuel.
“At this time, it makes a complete transition impossible without a full drop-in fleet replacement,” Gabehart said. The average piston-engine aircraft is more than 40 years old.
Health concerns closer to home
Boulder has never conducted a dedicated study on lead exposure from its airport. But evidence from other communities has prompted concern.
A 2023 peer-reviewed study of 14,000 blood samples from children living near Reid-Hillview Airport in Santa Clara County, California, which has since banned leaded gasoline, found that children within a half-mile of the runway had higher blood lead levels than those farther away. Wind direction played a role: Children downwind of the airport had more exposure than those upwind.
The study’s lead author, Sammy Zahran, a professor of epidemiology at the Colorado School of Public Health and economics at Colorado State University, previously told Boulder Reporting Lab the findings were “unambiguous.”
“When the evidence begins to compile in this way,” Zahran said, “it does give one pause.”
His earlier research in Michigan showed the same pattern. Both studies gained clarity from moments when flight activity dropped — after 9/11 and during the Covid-19 pandemic — when nearby children’s blood lead levels declined.
The increase in blood lead levels near the Santa Clara airport was roughly half of what they found in Flint, Michigan, during its water crisis, Zahran said. But that crisis lasted 18 months. “In the airport case, it’s an ongoing, continuous barrage,” Zahran said.
A 2024 state analysis reached a similar conclusion: Lead emissions from aircraft had a small but statistically significant effect on children’s blood lead levels statewide. The study included data from Boulder’s airport, though results were aggregated across multiple facilities.
Dozens of homes sit within a half-mile of the Boulder airport, including the Vista Village manufactured home park and residences along 75th Street, some within 500 feet of the runway. A private school and Valmont Bike Park are also within a mile.
At the “Lead Overhead” event, community members, researchers and lawmakers, including Boulder County Commissioner Ashley Stolzmann and state Rep. Kyle Brown from Louisville, gathered to discuss the risks.
“There is no threshold or safe level,” Bruce Lanphear, a public health researcher who studies lead exposure, told attendees. “As a physician, I see only one conclusion: We must urgently eliminate lead from aviation fuel.”
Spatial analysis by CU Boulder Ph.D. candidate Justin Bai found that neighborhoods closest to the airport, including Vista Village and San Lazaro mobile home parks, are disproportionately Latino and low-income.
Waiting for clarity
Even as Boulder works toward compliance, the airport’s long-term future remains uncertain. Some residents and advocacy groups want it closed and the land redeveloped for housing. But federal grants accepted decades ago may require it to stay open indefinitely, and a coalition of pilots, business owners and the Boulder Chamber argues it should.
A U.S. District Court recently dismissed the city’s challenge to those terms, leaving the question unresolved. It remains unclear whether the city will appeal that decision. Boulder has stopped accepting federal airport grants while the legal fight plays out, a decision that could leave the facility facing a budget shortfall as soon as next year, according to city budget records.
Boulder officials say they’ll submit their lead transition plan by year’s end to remain eligible for state funding, which could also support future electric aviation infrastructure.
Commissioner Stolzmann, while at the August panel, said the community conversation shouldn’t stop there. She’s interested in supporting a citizen science project to test soil for lead near the airport.
“Our community does a lot of citizen science programs and they have been wildly successful about moving policy and finding information,” she said.
It’s about time, but 2030 is a long way away. One would think Boulder would lead the way (pun intended) on issues like this. As for the 5-1 Planning Board vote, why did Michael McIntyre vote against it?
Hi Jarko, the vote against was from Jorge Boone, and no reason was given at the planning board meeting, I believe. Thanks for reading.
Let’s just be very clear that this is not a total ban on leaded fuel by 2030. This is a transition plan that needs to take effect 5 years from now! Once again this will very likely be paid for by tax payers, not the actual pilots. At this point, there is no guarantee that leaded fuel will be banned by 2030 by Boulder, EPA, FAA, etc.
While the efforts at Centennial are a great step, they have so far not reduced the amount of leaded fuel sold at that airport.
It’s also worth pointing out that the cost of a single soil sample to test for lead is $210 at Colorado’s primary testing lab used by the public. That of course comes out of our pockets. So while a “Citizen Science” project is great there are no funds to help impacted residents with this important health related issue.
The FAA requires Boulder to supply unlimited amounts of leaded fuel to the airport. It’s past time we stopped polluting our own community.
I’d like to recommend one edit to an otherwise well-researched and balanced article. “The shift won’t be simple” should be “The shift will be simple.” A new tank? A different fuel truck? Certification? Sounds straightforward to me. This doesn’t feel like a heavy lift given the health risks we are asking people to bear for another 5 to 10 years. We are a smart and capable city – let’s not pretend this is too complicated or difficult. We could do this in six months if we had the political will.
This is good reporting. Thank you, Por and BRL.
Let’s be clear though – the federal EAGLE program only establishes a goal to transition to unleaded fuel by 2030, and the state’s new legislation provides funding incentives for local airports to offer unleaded fuel. The federal government still mandates that all airports offer leaded fuel, which is sold side by side with unleaded, until they say otherwise. As the article notes, the current cost difference is almost $2/gallon for unleaded, and many pilots will not choose unleaded even if it is subsidized by the taxpayer, for all the same reasons that many car drivers didn’t voluntarily switch to unleaded and we had to enact a complete ban on leaded gasoline.
There is no hard timeline or committment to ban leaded fuel at the federal, state, or local level. We have to keep pushing on this issue. The children living near our airport are suffering irreversible damage from breathing in microparticles of lead, and they don’t get a second chance to grow up lead-free. And it’s not just children – research is showing increased risk of heart attack and other health complications from lead upon people of all ages.
Folks who want to track Boulder airport issues and get alerts for activism opportunities can sign up for the ANC mailing list here: https://www.airportneighborhoodcampaign.org/sign_up_for_mailing_list