Robert Boutelle and his wife had only lived in their new home for two months before they learned an alarming fact that led them to put their plan of starting a family on hold.
When they moved into their home in April 2021, they knew it was within miles of Rocky Mountain Metropolitan Airport—a busy, public-use airport located between Boulder and Denver that’s popular among hobby pilots, business travelers and pilots-in-training. What they didn’t know is that many of the planes flying directly above their home are fueled by leaded gas.
“My jaw just sort of dropped,” said Boutelle, who has a doctorate degree in chemistry from the University of California, Los Angeles.
Aviation fuel, also commonly called “avgas,” is the only transportation fuel in the U.S. to contain lead, the metal that acts as a neurotoxin and has been tied to lowered IQ, learning disabilities and behavioral problems in children. Although leaded automobile gas was phased out in the 1990s—which resulted in a 98% decrease in lead levels in the air—a carve-out allowed leaded aviation fuel to remain. Today, leaded aviation fuel is one of the largest remaining sources of airborne lead, accounting for 70% of it as of 2017, according to the U.S. Environmental Protection Agency (EPA).
“Most people actually don’t realize that piston-engine aircraft are still burning leaded fuels. This is like the last frontier,” said Christopher Keyes, PhD, a data scientist with the Fort Collins-based Mountain Data Group, a consulting firm that often conducts research for government agencies. Keyes co-authored a study published in January 2023 that found that as flight traffic and avgas sales rose at the Reid-Hillview airport in East San Jose, Calif., so did the lead levels in nearby children’s blood.
According to the study, around half a million pounds of lead is emitted into the environment each year by leaded-fueled aircraft, with approximately four million people—including 600 K-12 schools—living or learning less than half a mile from an airport.
While the dangerous health impacts of lead have been known for decades, the phase-out of avgas has been slow. But the federal government is inching closer to banning it. Last year, following years of community activism, the EPA released a draft endangerment finding declaring that leaded aviation fuels “may reasonably be anticipated to endanger public health and welfare.” And the Federal Aviation Administration (FAA), which funds and sets regulations for aircraft and airports around the country, also announced last year its plans to phase out the fuel by 2030.
Residents living near airports have formed neighborhood advocacy groups, often affiliated with the National Quiet Skies Coalition—which has chapters in Arapahoe, Boulder and Jefferson counties—to push local governments to phase out the fuel faster; cap flight operations to limit noise and pollution; change flight paths to avoid dusting schools and residential areas with lead; and conduct more public outreach to inform residents surrounding airports of the potential risks.
Much of the community activism in Colorado has centered on Rocky Mountain Metropolitan Airport and Centennial Airport, both of which are located in the Denver suburbs and have seen stark increases in flight operations over the last five years. Both airports are also in the top 100 lead-emitting airports in the country, according to the 2017 EPA National Emissions Inventory. Other high lead-emitting airports in the state include Greeley-Weld County Airport; Pueblo Memorial Airport; and Northern Colorado Regional Airport in Fort Collins.
“We have a moral obligation as a society to do something about this,” said Bri Lehman, a Lafayette resident living near Rocky Mountain Metropolitan Airport and a member of the advocacy group Save Our Skies Alliance. “People are being hurt and people are being poisoned. We can’t just look the other way.”
The Colorado Department of Public Health and Environment (CDPHE) is conducting an analysis to see whether living within five miles of an airport is associated with elevated levels of lead in children’s blood. But the assessment is based on blood samples collected from 2011 to 2020, and the data is limited. For example, some areas of the state have testing rates too low to assess accurately.
“There will be some limitations to this study,” warned Kristy Richardson, PhD, Colorado’s state toxicologist who leads the Colorado Childhood Lead Poisoning Prevention Program at CDPHE. “It’s not going to be able to tell us whether the blood levels that we see [near] these airports is caused by the airport or the aircraft activity. It will only tell us a relationship.”
Here are some helpful things to know about the use of leaded aviation fuel in Colorado:
Why is leaded fuel still used in some planes?
Leaded fuel was banned by the EPA for cars in 1996, but a carve-out allowed 100 octane low-lead fuel to remain in use for approximately 230,000 small piston-engine aircraft, which carry between one and six passengers.
It has remained in use in part for safety reasons, but also political ones. In terms of safety, the lead in the fuel boosts octane levels, which reduces the likelihood of engine damage or, in rare cases, engine failure. Alternative fuels have been developed and proposed over the last decade to ASTM International, the standards organization tasked with finding an alternative. But the new formulas have been repeatedly rejected because major oil companies lobbied for their small-but-profitable avgas market to remain.
U.S. lawmakers are currently deliberating what to do about avgas. A version of a pending bill requires airports to keep selling leaded fuel indefinitely. Another version mandates the sale of leaded fuel through 2030, or until a replacement is “widely available.”
Are there any fuel alternatives? Are they offered in Colorado?
In September 2022, the FAA formally approved a 100-octane unleaded avgas. Additionally, there is a 94-octane unleaded fuel by Swift Fuels that has been approved for some piston-engine aircraft. Other fuels are also in development.
At least one airport in Colorado, the Centennial Airport in Englewood, has started offering the new fuel. But the use isn’t mandatory, only encouraged.
In March, the Arapahoe County Public Airport Board of Commissioners voted unanimously to encourage the use of the new fuel at the Centennial Airport by providing financial assistance to pilots and flight schools in order to obtain the verifications needed to use the new fuel. The airport is also offering subsidies to bring down the cost of the new fuel to be in line with the comparable leaded fuel.
But at Rocky Mountain Metropolitan Airport, the fuel won’t be available for years, said Paul Anslow, the airport director, in an email. Last year, 15% of the air traffic at Rocky Mountain and 10% at Centennial was generated by piston-engine aircraft, according to federal data.
Anslow declined an interview request, but in a written response said he supports the phase-out of leaded avgas at his airport as soon as it’s “practical across the whole aviation industry.” He added that the airport, with support from Jefferson County officials, plans to offer financial assistance for those that use the airport to get the required certifications to use unleaded fuel, and that he has applied for FAA grant funding to purchase new fuel tanks.
Can the flight paths be changed?
With unleaded fuel still years away, residents who live near Rocky Mountain Metropolitan Airport have pleaded with elected officials during public meetings to cap the number of flights or force pilots to seek alternative routes to avoid dusting schools and residential areas with lead. The airport is the third busiest in Colorado, with more than 400 aircraft, 50 businesses and four flight schools based on site. Flight operations increased by 45% between 2017 and 2022, according to federal data, with no signs of slowing down.
“I can count up to five piston engines from my backyard at any given time. And I have jet traffic constantly. It never stops,” said Charlene Willey, a Westminster resident of nearly 30 years who lives in the flight path of the airport.
Anslow said flight path decisions are out of his control.
“RMMA and Jefferson County [have] no authority over aircraft flight paths,” he wrote. “There are some procedures that could be established to encourage pilots to route over less populated areas if possible. However, operations within the vicinity of an airport are internationally standardized, and there is virtually no ability to alter the established traffic pattern in the direct vicinity of an airport.”
Who is most at risk of lead exposure? And how do I get my child tested?
While lead is naturally occurring in the environment, it is toxic to the human body. Children younger than 6 years old are most vulnerable to the effects of lead exposure since the metal is easily absorbed in their nervous system, according to the Centers for Disease Control and Prevention.
Research shows there is no safe level of lead. And even low levels of lead in the body can cause developmental delays, learning disabilities, behavioral issues and neurological damage—all of which can be permanent and disabling.
The CDC estimates that 500,000 children in the U.S. have elevated blood-lead levels compared to others. Children are at higher risk of exposure if they live near an airport, lead smelter, mine or battery-recycling plants.
Symptoms of lead poisoning are typically not visible. A blood lead test at your doctor’s office is the best way to determine if a child has been exposed to lead. Here is a questionnaire that can help you figure out whether your child should be tested.
What research has been done about the impacts that leaded fuel can have on nearby residents?
The Reid-Hillview airport study conducted in California has become somewhat of a rallying cry for communities across the country that are pushing to ban leaded avgas. The study, which was funded by Santa Clara County, found that as avgas fuel sales rose, so did blood-lead levels in children. It also found that the closer a child lived to the airport, the higher their blood-lead levels were. After the study was published, Santa Clara County banned the sale of leaded avgas at the airport, making it the first airport in the U.S. to do so.
Apart from the Reid-Hillview airport, it’s safe to assume that leaded fuels are available at all airports serving piston-engine aircraft, according to Keyes, the data scientist who co-authored the study. The researchers found that the blood-lead level in children living closest to the airport was about half as much as was seen during the height of the Flint water crisis.
“But the Flint water crisis occurred over 18 months,” Keyes said. “What we’re looking at is every day, 365 days a year, ongoing.”
What research is happening in Colorado?
CDPHE is using existing blood-lead data collected between 2011 and 2020 to conduct a high-level analysis into whether children 18 years or younger who live within five miles of a regional airport have higher blood-lead levels. Here is a map of all airports in Colorado. Richardson would not say if the Rocky Mountain or Centennial airports will be a part of the state’s assessment. Both airports individually have more piston-engine traffic than Denver International Airport.
“Because of insufficient samples, it is unlikely that all 80 airports will be included in the final analysis,” Richardson wrote in a follow-up email. “The analysis will estimate the average effect that living near a regional airport in Colorado has on children’s blood lead levels. It will not show exposure or risk from living near any specific airport. … Our study could lead to the need for more testing, and we already know we need more testing.”
Last year, a group of 35 doctors and nurses sent a letter to Jefferson County elected officials urging them to slow the operation growth at Rocky Mountain Metropolitan Airport until more research can be done, and encouraged CDPHE to increase blood-lead testing of children residing near airports.
Richardson said she’s hesitant to single out avgas as an area of concern, despite airports being a risk factor on the state’s assessments.
“There’s so much going on with lead and there are so many different sources that I think I’m always afraid that if we focus just on one, we lose the big picture, which is that reducing lead from all of those sources is really important to reduce the potential health risks,” she said.
Boutelle said he isn’t necessarily pushing for the state to conduct a study exactly like what was done at the Reid-Hillview airport in California. “We know they’re going to find lead,” Boutelle said. “That’s not going to solve anything.”
Instead, he’d like to see a coordinated public health campaign and more pressure put on airports like Rocky Mountain to offer unleaded avgas as fast as possible.
“Centennial has already offered and is incentivizing this unleaded fuel,” he added. “That’s a great first step. That is an amazing first step. And I really, really wish that would be offered in our community as well.”