As Boulder considers closing its municipal airport to address housing shortage, lead concerns also emerge

Boulder residents will likely vote this November on whether to decommission the Boulder Municipal Airport and develop the land for housing. Advocates aim to address this controversial issue by putting it directly before voters. 

The Airport Neighborhood Campaign, which is behind two measures — one to close the airport and another to turn the land into a mixed-use neighborhood with affordable housing — has gathered enough signatures to place them on the ballot. The measures now await final approval from the city council.

Up to this point, the airport closure conversation has largely focused on the housing potential at the site, while pilots, the Boulder Chamber, business owners and other airport users vie for its continued operation. Now, however, closure advocates are also highlighting potential health impacts from leaded aviation fuel used by the small, piston-engine aircraft at Boulder Municipal Airport.

Several studies over the last decade and a half have revealed the risk leaded aviation fuel poses to children near airports. In 2023, the U.S. Environmental Protection Agency determined that lead exposure from piston-engine planes can harm cognitive function, lowering IQ and academic performance, with no safe threshold identified. Commercial jet aircraft do not use leaded fuel, and the EPA, along with the Federal Aviation Administration, aims to eliminate leaded aviation fuels by 2030.

There has never been a dedicated scientific study on the effects of leaded aviation fuel on children’s blood lead levels in Boulder. But studies from other communities, particularly Santa Clara County, California — which has banned leaded gasoline and is seeking to close one of its two airports — are drawing local attention. 

Published in 2023, the peer-reviewed study of 14,000 blood samples from children near Reid-Hillview Airport in Santa Clara found that proximity to the airport correlated with higher blood lead levels. Children living within a half-mile faced the highest risk. Wind direction also played a role; those downwind had higher blood lead levels than those upwind. Researchers sampled blood throughout the year and compared it to airport traffic, finding that increased landings and takeoffs of lead-burning planes correlated with higher blood lead levels in nearby children. The findings validated earlier research.

“When the evidence begins to compile in this way, it does give one pause,” said Sammy Zahran, the study’s lead author and a professor in the Department of Epidemiology at the Colorado School of Public Health and the Department of Economics at Colorado State University. 

Zahran and his team identified where the children in the study lived and attended school. They found that even if two children lived the same distance from the airport, the child attending school closer to the airport had higher lead levels in their blood than the child attending a school farther away. This difference disappeared during the summer break. 

“This was the last bit that convinced me there was something truly wrong,” Zahran said.

The 2023 study was not Zahran’s first publication on the effects of leaded airline gas on children’s blood lead levels. A 2017 study analyzing 448 airports and more than a million children across Michigan came to similar conclusions.

Both airport studies were marked by tragic events that bolstered evidence. During the Michigan study, the 9/11 terrorist attacks caused a massive downturn in airplane traffic. Similarly, during the Santa Clara study, the Covid-19 pandemic led to a significant decline in air traffic. By continuing to sample children’s blood through these disturbances, Zahran and his team found that as air traffic decreased, the lead levels in nearby children’s blood also decreased.

For context, the increase in blood lead levels for children living near the Santa Clara airport was about half what researchers, including Zahran, found during the height of the Flint, Michigan water crisis. Yet the Flint crisis lasted 18 months.

“In the airport case, it’s an ongoing, continuous barrage,” Zahran said. 

Lead exposure is especially worrisome for children, as it can permanently lower their IQ. A recent study estimated that the burning of leaded gasoline for cars stole more than 800 million IQ points from Americans alive today. Leaded gas for cars was banned in 1996.

“You pick up kids [with lead exposure] later, much later, when they are writing their ACT and SAT tests for college admission, and not only do you see a persistence, but you see an amplification of the effect in time,” Zahran said. “It’s not only irreversible, but it seems to worsen.”

Dozens of homes are within a half-mile of the Boulder airport, including part of the Vista Village manufactured home community to the southwest and several homes in the neighborhood off 75th Street to the northeast. Some homes in the 75th Street neighborhood are within 500 feet of the runway. A private school is about a half-mile to the southeast of the runway. When asked if he would live near Boulder’s airport having completed his studies, Zahran said, “As a father, I would likely be among those expressing concern.”

A Colorado Department of Public Health and Environment study published in May concluded that lead emissions from aircraft using leaded gas have a small but statistically significant effect on the blood lead levels of children living near Colorado airports. The study, which used blood lead tests submitted between 2011 and 2020, included data from the Boulder Municipal Airport, though the results were averaged with those from 11 other airports. Researchers used existing lead test results to determine where the children lived, but the data is not public for privacy reasons. Zahran’s Santa Clara study is referenced throughout the paper.

Andrew McKenna, president of Journeys Aviation, a flight school and the fuel provider at Boulder Municipal Airport, opposes the airport closure efforts and remains unconvinced by the lead concerns. In his 40 years around airports, he said he has “fueled aircraft, had aviation fuel splash on my skin, breathed in the fumes and gotten fuel in my eyes and mouth.

“Despite all that, my tested blood lead levels are well below the threshold of concern.” 

McKenna said that the Boulder airport not only relieves pressure on larger airports like DIA but also helps provide major airlines with pilots. As the military trains fewer pilots, airlines are relying on flight schools that use smaller airports like Boulder. “As you pass the flight deck boarding the airliner taking you on vacation to Hawaii, odds are the pilots trained at a small airport,” he said. 

McKenna said that while Journeys wants to bring an unleaded option to Boulder as soon as feasible, logistics and finances present significant barriers. 

For one, the unleaded fuels currently available often require separate fueling infrastructure from standard leaded fuel. “Boulder airport doesn’t have the extra dedicated fuel tanks available to offer these fuels,” McKenna said.

He added that to burn unleaded fuel in an airplane designed for leaded fuel, plane owners must purchase “supplemental type certificates” from the FAA to approve the use of the unleaded alternative. These certificates are costly, he said. 

“It would probably cost us several thousands of dollars to acquire all the necessary STCs for the entire fleet,” McKenna said. “In addition, the cost of these unleaded aviation fuels looks to be about $1.00 to $1.20 per gallon more expensive.” Adoption won’t happen anytime soon without financial incentives from the city or others to encourage aircraft operators to buy the STC and use unleaded fuels, he said.

McKenna noted that one unleaded alternative in production could be used by all planes currently burning leaded aviation fuel and wouldn’t need separate fueling infrastructure. But this alternative is facing issues with distribution and market acceptance.

Aisha Ozaslan, a communications manager with the city, said, “Boulder supports switching to unleaded fuel in the future.” She added that besides infrastructure challenges and availability of unleaded alternatives, the city lacks the FAA authority to remove leaded aviation fuel from Boulder’s airport. In Santa Clara, leaded gasoline is no longer sold at either airport in the county, according to county officials.  

Accelerating the statewide transition away from leaded fuel

Even if unleaded fuel were widely used in Boulder, airport closure advocates are concerned that planes from other airports could still fly in using leaded fuel, exposing Boulder’s children. “We can’t stop planes from coming in that are burning leaded aviation fuel, no matter what we choose to sell at our airport,” said Lauran Kaplan, who has led the effort to close the airport through ballot measures.

One solution is to accelerate the statewide transition away from leaded fuel, as a state bill passed this year aims to do. Sponsored by Rep. Kyle Brown of Louisville and Sen. Steve Fenberg of Boulder, the bill provides state income tax breaks for plane owners buying STCs, allowing some piston-engine aircraft to burn unleaded alternatives. It also funds infrastructure updates to enable the sale of unleaded aviation fuel and subsidize the cost differences. The bill approves grants for stations to charge electric aircraft once such aircraft are approved by the FAA.

The Boulder Municipal Airport isn’t the only airport in the area using leaded fuel. The Town of Superior and Boulder County are suing Jefferson County over its operations at Rocky Mountain Municipal Airport. Besides noise complaints, the plaintiffs cited lead concerns in their lawsuit.

“Boulder County brings this suit to protect a public right — air and soil free from lead contaminants and the quiet enjoyment of each resident’s property — to prevent future injury to its residents and the public at large,” the suit states.

Like in Boulder, no dedicated scientific study of blood levels in children has been conducted near Rocky Mountain. In 2023 and 2024, the Town of Superior conducted a series of air and surface lead studies by the airport. All showed lead levels within EPA standards. The air quality monitors in Superior were operational for a few hours each day over a couple of days.

Bruce Lanphear, a professor at Simon and Fraser University in Canada specializing in environmental neurotoxins and lead poisoning, said in a recent webinar hosted by Boulder airport closure advocates that such studies cannot adequately capture the effects of chronic exposure. 

“If I went and stood half a mile from the airport for one hour, or one day, or three days, and then you tested my blood, you’re not going to pick that up,” Lanphear said. “If I went and lived there, and certainly if my granddaughter went and lived there for six months or a year, you’re absolutely going to pick it up.”

Jeff Hartig, chief instructor pilot at Western Air Flight Academy operating out of Rocky Mountain, said that while Western Air would like to be better neighbors and burn unleaded fuel, the airport has yet to build the necessary infrastructure. There is talk this might change next year. 

“As soon as unleaded fuel is available, we will use it in as many aircraft as possible,” Hartig said. All but two of Western Air’s 25 planes have already received STCs and will be able to transition to unleaded fuel once it becomes available.

Centennial Airport, near Denver, is currently the only Colorado airport offering the sale of unleaded aviation gasoline for aircraft that typically burn leaded fuel, according to its website. The airport received a grant from the Brown-Fenberg bill to subsidize the cost difference. Hartig said Western Air’s sister school at Centennial now uses unleaded fuel whenever possible. 

“All but three of their 45 airplanes can burn unleaded fuel,” Hartig said.

Beyond the lead issue, Boulder airport closure advocates are paying attention to Santa Clara’s efforts to close Reid-Hillview Airport by 2031, the target set because Reid-Hillview last accepted an FAA grant in 2011.

When an airport accepts an FAA grant, it is usually required to stay open for 20 years or the lifecycle of the funded project. Boulder most recently accepted an FAA grant in 2021.