The largest known source of lead emissions is leaded aviation fuel, most commonly used for small aircraft at small, regional airports.
A new study from Oregon State University has found that this fuel leads to more lead pollution in surrounding urban areas and neighborhoods, which can affect human health through poor air quality and soil contamination. The study looked at air quality surrounding regional airports near Hillsboro and Troutdale, two of the top three lead emitters in Oregon.
Alyssa Shiel, an associate professor in the College of Earth, Ocean and Atmospheric Sciences at OSU, has been studying lead and heavy metal contaminants for nearly a decade. She joins us to share her findings and what concerns they raise.
Note: The following transcript was transcribed using AI and validated for accuracy, readability and formatting by an OPB volunteer.
Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. We start today with a new study that looked into airborne lead pollution. Lead was taken out of motor vehicle gasoline decades ago, but it is still used in aviation fuel for some airplanes. That is why regional airports in Hillsboro and Troutdale are two of the top three lead emitters in Oregon. But a new study from Oregon State University found that this lead is not staying at the airports. It was found in neighborhoods three-quarters of a mile away.
Alyssa Shiel is an associate professor in the College of Earth, Ocean and Atmospheric Sciences at OSU. She joins us now. Welcome back to the show.
Alyssa Shiel: Thank you, Dave. It’s good to talk with you.
Miller: You’ve been researching heavy metal contamination for nearly a decade. What made you want to look into this in the first place?
Shiel: I got into looking at heavy metal contamination actually as an undergrad researcher at the University of Arizona. And some of my projects there were focused on lead that people would consume in herbal remedies or even candies. I kind of moved away into studying other metals in graduate school and other parts of my career, but I keep coming back to lead because it really is so toxic. And despite having a long history about knowing about problems with lead, it’s still a big problem in public health that I really think should be a priority to address.
Miller: What does lead do to a human body?
Shiel: Lead damages almost every part of the body. And in the case of lead, there’s no amount that is known to be safe. When we’re thinking about adults, chronic exposure is primarily driving cardiovascular risks: thinking about high blood pressure and heart disease. In young children, who absorb lead much faster, we see permanent damage to their developing brains. That’s going to include lower IQ and behavioral changes. So we’re really talking about some big stuff here.
Miller: Your latest research was based near the Hillsboro and Troutdale airports. What are these airports used for?
Shiel: So these are smaller regional airports. This is in contrast to the biggest airport in the state, Portland International Airport, which is mainly commercial jets we fly in around the country. These small regional airports are supporting a lot of smaller aircrafts, including piston-driven planes and helicopters. And those are the aircraft that use this leaded aviation fuel. Large jets are using jet fuel, there’s no lead added to that fuel. But these smaller piston-driven aircraft are using this leaded fuel. And when I think of that, I’m thinking of flight schools, personal or business travel, recreational flying, maybe some aerial surveys or agricultural applications, but you’re thinking small planes for like two to six passengers or helicopters for two to three people. This is smaller traffic that’s going to happen at lower altitudes.
Miller: I have to admit, I thought we were just done with leaded fuel completely. In your conversations with friends or family, or maybe even colleagues, how many people were as ignorant about this basic fact that leaded fuel is still being used for this whole category of aviation? How many people are as ignorant as I was?
Shiel: Dave, I think most people don’t know. I think if you start talking to community members near some of these airports, you’ll see higher numbers of people that are aware. But I think most people don’t know. It really is kind of shocking because this is the single largest remaining source of airborne lead pollution in the U.S. And we had such a great public health victory phasing out leaded gasoline use in vehicles at the end of the 20th century. That’s been huge, we’ve seen huge gains from that.
Miller: And changes in lead paint as well, although we’re not talking there about airborne, but in terms of a societal shift.
Shiel: Exactly. But removing those sources, we’re starting to see what else is underneath. Some of these other sources are more visible, and I really would like to see us tackling those. That’s why I’ve made them a priority in my research.
Miller: So what did you find when you looked at areas near these airports?
Shiel: In this study, we were using moss collected from trees near Hillsboro and Troutdale airports, and we were able to trace airborne lead pollution directly to the leaded aviation fuel that they were using. We do that with a technique called isotopic fingerprinting. That’s where you can actually take the unique chemical fingerprint of lead from one source, and “fingerprint” it, match it to what you see in moss samples.
Miller: Meaning, it’s possible for you then to know that if the moss has absorbed lead, you can rule out that it came from other sources of lead besides this aviation fuel?
Shiel: Yeah, that’s right. We sampled moss from different distances from these airports, so we do see a gradient. We see the highest lead near these airports, and that’s where we see that chemical fingerprint for this aviation fuel the strongest. And then as you go away from the airport, you get further away into the urban background, we see other urban sources. They have distinct chemical fingerprints, so we can separate that out.
Miller: Just how high was the concentration of lead that you found close to airports?
Shiel: The highest concentration of lead we found within about a half a mile of the airport was about seven times other urban areas, or almost 50 times what we would see for lead in rural areas in this moss.
Miller: It’s been a little while since we talked with you about this moss piece. Can you remind us why you look at moss as a kind of proxy or marker for airborne lead pollution?
Shiel: Yeah, absolutely. Moss is a great indicator for air pollution. The moss that we’re using in this study is growing on street trees, so it’s off the ground, it’s in the tree canopy. And these moss act as little sponges for what’s in the air. They get their nutrients and the moisture they need from the air, but they kind of inadvertently take up pollutants, including lead. And unlike air monitors, which are very expensive to deploy – studies using air monitors usually have to rely on one or two to cover a whole area – we can collect moss over a big geographic area and get a much better picture of what’s really going on and how much lead levels vary, and really the footprints of the impact of these lead sources.
Miller: Does it matter how old the moss is? If moss has been slowly growing on some tree for a decade, is it likely to have absorbed more lead than a patch that has only been there for nine months?
Shiel: Yeah, there can be some differences there. We try to target moss that’s going to have been there around three to five years, so it is going to be integrating over that time period. We do some trimming in the lab before we make our chemical measurements to try to focus on the most recent lead, but there is some integration. But that’s actually one of the things we like about using moss as opposed to something like an air monitor, which serves its own purpose. Because it integrates, you’re not going to miss something. So if you put up an air monitor this week and you look at pollution coming from, for example, the airport, maybe there was lower traffic than normal, or maybe the wind direction was different than it normally is, and so you’re not going to fully capture that. Whereas the moss is going to integrate over a year or even years, so you get a better picture of what the long term impact is.
Miller: So to be clear, this study, it’s looking at a very helpful proxy for lead contamination in the air, this moss. But how direct is the correlation between the lead that’s in the air being absorbed by moss, and lead getting into people’s bodies? The other way to ask that question is, would you assume that people living or working within, say, a mile of these airports would have elevated levels of lead in their systems?
Shiel: Our moss study lets us know it’s in their environment and it’s getting into the air, it’s airborne. It doesn’t tell us how much people are being exposed to or what their exposure levels are. To get at that, you really need to look directly at blood lead levels in people. And there have been some studies that have done that near similar sized airports, and they do see this kind of similar, if maybe not even larger geographic footprint around the airports. In terms of people near Troutdale and Hillsboro, based on our findings, I would recommend that if they’re concerned, that they talk to their doctor about whether or not a blood lead level test is appropriate for them or someone in their family
Miller: What other advice would you give to people who live close to these airports, in addition to getting tested, for how to mitigate exposure, or how to live their lives or tell their kids what to do to minimize exposure?
Shiel: Well, we have a website we’ve put together for folks. It’s up at beav.es/aviation, and it has some recommendations and resources linked there. Some of the stuff that people can do may be stuff they’re already doing, even if they’re not aware of this issue, like keeping the lead out of your home. So if you’ve been outside, take off your shoes outside the door or at the door. When kids are coming inside after playing, washing their hands, or washing hands before eating, that’s going to minimize exposure. There are some small stuff like that that could actually make a big difference that people may even already be doing.
Miller: Those two examples seem like they’re about lead that’s gotten onto the surface of things, onto dirt or onto hands. But what about just airborne exposure? If the moss is in a sense breathing this in, can’t we do that as well?
Shiel: Yes. When we’re thinking about emissions from an airport, we would be concerned about two things. We’re concerned about airborne lead, like you’re saying, that could be inhaled or even ingested from the air. And then we’re also thinking about ingestion of potentially contaminated soil or dust. We’re thinking about both things. The size, the relative importance of the inhalation versus ingestion near these airports is not clear to me. I actually think they could both be pretty important, and it may be that, similar to other sources, for adults inhalation is more important and for children ingestion is more important. But I really think to answer that in a really clear way, more research is needed.
Miller: Finally, are there any efforts to get the lead out of the last vestiges of aviation fuel?
Shiel: In 2023, the Environmental Protection Agency issued an endangerment finding concluding that these emissions endanger public health. So this is going to result in new standards for the industry. The Federal Aviation Administration and federal government are already working to transition the entire U.S. fleet to unleaded fuel by 2030…
Miller: And that endangerment finding, that has survived the Trump administration?
Shiel: To date, I haven’t heard any changes. I’m hoping that research like this will help keep this a priority and that transition that’s planned by 2030. Because that means that they’ve got to up production of the alternatives and work on distribution. I’m hoping research like this will keep the pressure on to make sure that that transition happens on that timeline, if not sooner.
Miller: Alyssa, thanks very much.
Shiel: Yeah. Thank you, Dave.
Miller: Alyssa Shiel is an associate professor in the College of Earth, Ocean and Atmospheric Sciences at Oregon State University.
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