Study makes link between blood lead and the gasoline used to fuel small planes
People who live near airports serving small planes are exposed to lead from aviation fuel. A new study now links an airport’s proximity to slightly elevated blood-lead levels in children from area homes.
Small planes (known in the trade as general aviation) tend to run on gasoline, most of which contains lead as an octane booster. These aircraft — used as taxis, personal aircraft and training vehicles — fly out of nearly 20,000 U.S. airports. And as other sources of lead have fallen, the relative share that aviation gas, or avgas, contributes has been rising.
Indeed, the Environmental Protection Agency, estimates: “Emissions of lead from piston-engine aircraft using leaded avgas comprise approximately half of the national inventory of lead emitted to air” — making it the largest contributor to airborne lead in the United States.
But high as that sounded, researchers still couldn’t evaluate the fuel’s health significance. People wanted to know: In terms of lead poisoning, ‘is this an important source,’” observes Bruce Lanphear of Simon Fraser University in Vancouver, British Columbia, who was not involved with the new study. “We simply lacked data to answer that,” the toxicologist says.
The new study’s attempt to tie proximity to regional airports with lead levels in kids “certainly makes it a noteworthy paper,” he now concludes.
Environmental health scientists and statisticians at Duke University’s Nicholas School of the Environment in Durham, N.C., used state records to identify children who had been tested for blood-lead levels, and mapped their residences in relation to regional airports in several counties. Then the researchers correlated lead concentrations in those kids with the distance of their homes from those airports.
Children 7 and under who lived within 1,000 meters (six-tenths of mile) of an airport — and especially within 500 meters — had higher lead levels, generally, than youngsters living beyond that distance. This association remained “robust” even after adjusting for a host of other factors that might affect the likelihood a child would be exposed to lead, such as living in an older home (which might have lead-based paint), observes study leader Marie Lynn Miranda.
In a paper published online July 13 in Environmental Health Perspectives, she and her colleagues find that the likely contribution of aviation gasoline to a child’s blood-lead burden is small — in the range of 2 to 4 percent (depending on whether they lived within 1,000 meters of an airport versus half that distance).
That may not sound like much, Miranda acknowledges, but every little bit matters. Her own studies have linked end-of-the-year test grades with increasing levels of lead in a child’s blood. In fourth graders, lower scores could be correlated with blood concentrations as low as 2 micrograms per deciliter, she found — just a fraction of the 10 µg/dl value viewed as a federal “action level”.
The Duke team’s new analysis did not stratify children in terms of where their homes were in relation to prevailing winds or predominant take-off and –landing paths. So, Miranda says, her team’s quantitative estimates will likely underestimate the contributions of avgas emissions to lead levels in some youngsters.
And Lanphear anticipates that toddlers, who tend to put things into their mouths a lot, may have an exaggerated early exposure to the lead in dust. Instead of seeing a 4 percent contribution of avgas fallout to their blood lead values, he said, you might see a 10 percent increase.
Finally, Lanphear adds, children aren't the only potentially at-risk population. Several studies have shown "that even extraordinarily low blood lead levels in adults are associated with an increasd risk of death from heart attacks and strokes." The mechanism: lead's ability to boost blood pressure, he says.
There are alternative leadfree or certainly reduced-lead fuels for small planes, Miranda points out. And it’s in that context, she says, that she’d argue her team's new findings “are highly policy relevant.”
Five years ago an environmental group, Friends of the Earth, petitioned EPA to issue a finding under the Clean Air Act that “lead emissions from general aviation aircraft endanger public health and welfare.” If such a finding were issued, then the group wanted EPA to issue a proposed lead-emissions standard for small planes.
A little more than a year ago, EPA published an "advance notice of proposed rulemaking" that summarized pertinent data scientists might use in evaluating whether leaded avgas poses a health threat.
Three months later, five industry groups representing general aviation aircraft owners, operators and manufacturers sent a letter to the director of EPA’s Office of Transportation and Air Quality, Margo Oge. In it, they asked whether there was any truth to the rumor that EPA would ban leaded avgas by 2017.
“There is concern,” the letter said, “that current and future EPA actions will be taken that could potentially jeopardize the safety of the operation of piston aircraft” — planes designed to run on high-octane fuel. Moreover, the letter observed, “there is a strong and growing perception that EPA actions will lead to the grounding of portions of the existing fleet that require high octane avgas.”
Oge responded within five days noting that her agency’s 40-page notice of proposed rulemaking was only a means to ferret out additional data that might be useful in determining whether lead-emissions standards for small planes might be warranted. She also emphasized “EPA has not established or proposed any date by which lead emissions from aircraft operating on leaded avgas would need to be reduced. In fact EPA does not have authority to control aviation fuels.” (That’s the Federal Aviation Administration’s bailiwick.)
What EPA can do is restrict emissions from a vehicle that could endanger health, Oge pointed out; after that, manufacturers and operators could choose how to comply.
Since then, EPA has remained quiet on the status of its deliberations.
Agency for Toxic Substances and Disease Registry. Lead toxicity: What are the U.S. standards for lead levels? [Go to]
M.L. Miranda, et al. The relationship between early childhood blood lead levels and performance on end-of-grade tests. Environmental Health Perspectives, Vol. 115, August 2007, p. 1242. doi:10.1289/ehp.9994 [Go to]
M.L. Miranda, et al. Environmental contributors to the achievement gap, NeuroToxicology, Vol. 30, November 2009, p. 1019. doi:10.1016/j.neuro.2009.07.012
M.L. Miranda, R. Anthopolos and D. Hastings. A geospatial analysis of the efffects of aviation gasoline on childhood blood lead levels. Environmental Health Perspectives, in press, posted online July 13, 2011. doi: 10.1289/ehp.1003231 Abstract: [Go to]
U.S. Environmental Protection Agency. Fact sheet for Advance Notice of Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline: Regulatory Announcement. [Go to]
U.S. Environmental Protection Agency. Fact sheet for Advance Notice of Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline: Regulatory Announcement. April 20, 2010. [Go to]
Friends of the Earth. Petition for rulemaking seeking the regulation of lead emissions from general aviation aircraft under § 231 of the Clean Air Act: Petition for rulemaking & collateral relief before the Administrator of the United States Environmental Protection Agency. Oct. 3, 2006. [Go to]
R. Hackman, et al. July 22, 2010 letter to Margo Oge Re: EPA-HQ-OAR-2007-0294 Advance Notice of Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline. [Go to]
M.T. Oge, U.S. EPA. July 27, 2010 letter to Robert Hackman of the Aircraft Owners and Pilots Association regarding the Advance Notice of Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline. [Go to]