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California is famous for its picturesque sunsets, year-round mild weather, excellent surf, and largely progressive politics, including forward-thinking greenhouse emission policies. This week on Sea Change Radio, however, we learn about a less pleasant claim to fame for the golden state. Today we’re speaking with two scientists from Johns Hopkins University who are working to uncover the mysteries behind a dangerous greenhouse gas: sulfuryl fluoride. One such mystery is why so much of this harmful atmospheric compound originates from Southern California. Dylan Gaeta and Scot Miller walk us through changes in termite-eradication practices, how termites are not all alike, and what needs to happen in the nation’s most populous state and elsewhere to solve the problem.
Narrator | 00:02 – This is Sea Change Radio covering the shift to sustainability. I’m Alex Wise.
Dylan Gaeta | 00:20 – These sort of policies mandate emissions reductions of greenhouse gases across the board, but in all of these cases, sulfuryl fluoride isn’t included in that list of greenhouse gases that require emissions reductions. So in, in that sense, it’s sort of slipping through the cracks or under the radar, and are greenhouse gas emissions accounting.
Narrator | 00:40 – California is famous for its picturesque sunsets, year-round mild weather, excellent surf, and largely progressive politics, including forward-thinking greenhouse emission policies. This week on Sea Change Radio, however, we learn about a less pleasant claim to fame for the golden state. Today we’re speaking with two scientists from Johns Hopkins University who are working to uncover the mysteries behind a dangerous greenhouse gas: sulfuryl fluoride. One such mystery is why so much of this harmful atmospheric compound originates from Southern California. Dylan Gaeta and Scot Miller walk us through changes in termite-eradication practices, how termites are not all alike, and what needs to happen in the nation’s most populous state and elsewhere to solve the problem.
Alex Wise | 01:35 – I am joined now on Sea Change Radio by Dylan Gaeta and Scot Miller Dylan is a PhD candidate at Johns Hopkins School of Environmental Engineering, and Scot is an assistant professor there. Scot, Dylan – welcome to Sea Change Radio.
Dylan Gaeta | 01:57 – Yeah, thank you for having us. Yeah, thanks. It’s great to be here.
Alex Wise | 02:01 – So, Dylan, you are the lead on this study that is just getting published entitled, California Dominates US Emissions of the Pesticide and Potent Greenhouse Gas, sulfuryl fluoride. Explain the genesis of your research and why people should be aware of this.
Dylan Gaeta | 02:23 – I hadn’t heard of sulfuryl fluoride until I, until I came to Hopkins and started my PhD here. And this was around 2020 and I started working with Scot. And so Scot had been in contact with a colleague from the NOAA Global Monitoring Laboratories, who was sort of at the end of his career and had started looking at this gas around 2015. NOAA started, no, no, global Monitoring Laboratory started making these measurements and sort of pass it on to Scot as to say like, well, I’m out of time to, to look at this myself, but maybe this would be a good, um, topic to look into further. And so, so I, um, we started digging into where the SC is emitted in the world and like what, what, what it’s used for, um, how it’s been accumulating in the global atmosphere. Um, and when we started looking at those measurements, we sort of found, um, a sort of striking lack of information about the global distribution of this gas and where it’s being used and what it’s being used for and where, how much is being emitted in different parts of the world. And so what we did in our research study is that we, we used atmospheric measurements that were collected by our colleagues over at the, the NOAA Global Monitoring Laboratory. And we started and we used those atmospheric measurements to, to sort of back trace where the emissions of this gas were coming from. Um, and when we did that, we found that a pretty striking majority of the, of the US emissions of this gas were coming from the state of California. And we didn’t see a whole lot of evidence for emissions of this gas happening outside of California, which is sort of unusual for, for most greenhouse gases where you can imagine they’re a little bit more, the emission sources are spread a little bit more evenly throughout where people live. But in this case, we, we saw big hotspot over California and especially southern California.
Scot Miller | 03:58 – I’ll jump in and add something as well. I grew up in the state of North Dakota, which is, you know, a cold frozen state that doesn’t have too many termites running around. And I moved out to California in year 2015 about the same time that NOAA was starting to collect these measurements of sulfuryl fluoride. And when I lived out there, I had about a seven-mile commute on a bicycle to get to work every day. And I would, you know, bike through these residential neighborhoods in the San Francisco area Bay area and see what looked like giant circus tents over the top of houses. And, and being from North Dakota, I had never seen that before. And I, housemate at the time happened to be from Sacramento, and I was talking to her and she said, “Oh, you haven’t seen that before. You don’t know what that is?” And I said, “Well, no, I don’t.” She said, “You know, that’s, that’s termite fumigation.” And it’s, it’s a pretty common thing that you see around the state of California. And you, we just don’t have that back in the state of North Dakota. And so I was talking to our colleague, uh, Ben Miller at NOAA, and you know, he mentioned about how he had started, uh, observing this gas sulfuryl fluoride, um, that’s u the primary gas that’s used for termite fumigation. And I thought, “Huh, well, it’s interesting to take a look at it because it’s, it’s something we definitely see here in the state of California” – see the use of this gas in California, but that I hadn’t ever seen before I moved here. And then lo and behold, when we, you know, dug in and look at emissions patterns and tried to estimate where these emissions were coming from, all the data that we have seems to be pointing like you might guess at California.
Alex Wise | 05:33 – Dylan, maybe you can explain how you were able to investigate and isolate this gas in your study and walk us through your research method a little bit, if you can.
Dylan Gaeta | 05:44 – It wasn’t until about 2009 when sulfuryl fluoride was actually identified as a long-lived greenhouse gas. So I think prior to 2009, most people had thought about this topic, had sort of assumed that sulfuryl fluoride only persists in the atmosphere for a short amount of time. And so since it’s short, since it was presumed to be so short-lived, um, its global warming effect was, was thought to be pretty small. Um, but one of our colleagues, Jens Mühle, who’s a co-author on the study, published a paper in 2009 showing that it actually sulfuryl fluoride in the atmosphere has breaks down really slowly. So it reacts really slowly with all the gases in our atmosphere that we, that we had previously thought might, might scrub this from the atmosphere. And it turns out to be the ocean that that takes up most of this gas. And that that process of the ocean taking up sulfuryl fluoride happens really slowly and sort of in the app with the absence of an efficient removal mechanism from the atmosphere. It, um, the, the, the gas persists after being emitted for something like 40 years in the atmosphere. And over that 40-year lifetime, since the gas is a greenhouse gas, um, it has the ability to trap heat and send it back down to earth over a much longer time period. And so because of that, it has a larger global warming potential than what we originally thought when we started using the gas.
Alex Wise | 07:02 – So is it the gas itself which is surprisingly harmful, or is it the fact that it’s in much larger quantities than previously thought?
Dylan Gaeta | 07:13 – So, so it was the lifetime that, that, that sort of, um, was the surprise. So, so, um, scientists from a gauge, the advanced global atmospheric gases experiment had been measuring sulfur flight in our, in our global atmosphere at different places at, um, places around the world, um, since I think it was around 2004 or 2003 was the first time this was measured in the air. Um, and then the scientists also went back and took measurements of archived flask samples, air flask samples that had been stored all the way back to 1978 and had found sulfuryl fluoride levels and those flasks as well, but saw this increasing trend where over the span of about 50 years from the late seventies to today, we saw, we’ve seen about a tenfold increase in our, in the, in our atmosphere. So now current concentrations are, are around something like three parts per trillion. So three out of every trillion air molecules in our atmosphere are solu fluoride.
Alex Wise | 08:08 – Now, is there a direct correlation between sulfuryl fluoride emissions and termite control? Can we, can we pinpoint that specific practice as the red flag, so to speak? Or is it, was that just, another log on the fire?
Dylan Gaeta | 08:37 – So just to back up this, this sulfur flight is also like an entirely anthropogenically produced compound. So there’s no not, there’s no significant natural sources of the cast.
Alex Wise | 08:54 – Maybe walk us through the history of how long has it been in, in production and how has the EPA classified it up till now?
Dylan Gaeta | 09:04 – Yeah. So, so the gas was first starting to be produced by Dow Chemical, and I believe this was like the late fifties. Um, but starting off the, the quantities that were produced were relatively small because we had other replacement FME, we had other alternative FME against that were used for fumigating termites and other bugs and pests that we were worried about, um, both within structures and also like agricultural. But I guess it was around the late eighties, early nineties when, when scientists started to identify, um, methyl bromide as one of, one of the major contributors to the ozone depletion. And so under the Montreal protocol, countries around the world signed an agreement to phase out the use of methyl bromide. Um, and so in the United States that that deadline to phase out methyl bromide was around 2005. And so as methyl bromide was phased out, um, people started to look for alternative fum against, and sulfuryl fluoride sort of came onto the scene as, as the preferred effective replacement for methyl bromide. So it doesn’t deplete the ozone layer, which is really what we were looking for at the time was a, was a fumigant gas that doesn’t deplete the ozone layer. Um, so we started using sulfuryl fluoride and then sort of later found out that it’s actually a pretty potent greenhouse gas. Um, so it doesn’t have the same ozone depleting effects, which is great, but it does have a contribution to planetary heating as well.
(Music Break | 10:39
Alex Wise | 11:34 – This is Alex Wise on Sea Change Radio, and I’m speaking to Dylan Gaeta and Scot Miller of Johns Hopkins. So Scot, maybe you can put into context what Dylan was just telling us about the history of sulfuryl fluoride.
Scot Miller | 11:48 – Yeah, so the gas that was previously used was called methyl bromide. And you know, one thing Dylan highlighted is that the, the old gas that we used to use methyl bromide was an ozone depleting substance, but not only did it deplete the ozone layer, but also had some pretty terrible health impacts as well. Um, it’s a known carcinogen, it causes cancer, um, and was shown to cause um, developmental and neurological delays in children. And so this gas is certainly something that we do not want to be using anymore methyl bromide. And so as bad as sulfuryl fluoride is as a potent greenhouse gas, it does replace a chemical that was far, far worse for the environment, both for the ozone layer and for people’s health.
Alex Wise | 12:32 – So give us an idea of how much your study is projecting that sulfuryl fluoride contributes to greenhouse gas emissions and what the curbing of this and regulation of this gas could do to improve the situation, Dylan.
Dylan Gaeta | 12:51 – There, there’s been some work through the IPCC or the, the intergovernmental panel on climate change that that’s characterized sulfuryl fluoride levels in the atmosphere. And I think the IPCC reports have, I think, done a good job of sort of putting the impact of sulfuryl fluoride in context with all the other greenhouse gases in our atmosphere. In terms of policy around sulfuryl fluoride, it’s an interesting case because unlike most of the other greenhouse gases that are included under the accounting protocols, either like it for national greenhouse gas inventories or state level greenhouse gas inventories, sulfuryl fluoride is not included in any of them. So if you think of sort of like landmark climate change legislation, like, like under the United Nations or, um, in California, there’s the, the California Global Warming Solutions Act of 2006. These sort of policies mandate emissions reductions of greenhouse gases across the board, but in all of these cases, sulfuryl fluoride isn’t included in that list of greenhouse gases that require emissions reductions. So in, in that sense, it’s sort of slipping through the cracks or under the radar in our greenhouse gas emissions accounting.
AW | 13:55 – Let’s focus on California a little bit more. You mentioned California’s regulations. You write that California’s the only state that keeps a public record of statewide sulfuryl fluoride use, but California also seems to be the biggest problem spot for its emission. How did you hit upon California as being this bright spot in the map? And give us an idea of how bright it is and how California is an anomaly from the other states of, in the US for example.
Dylan Gaeta | 14:29 – Yeah, so those findings largely came from the atmospheric measurements that we were working with. And so these measurements come from the NOAA Global Greenhouse Gas Reference Network, which is, um, you can think of as a collection of tall tower sites, so like tall, um, radio towers that have air flask samples collected at the top of them, so like high up in the atmosphere. And also there’s been a variety of aircraft campaigns that also collect aircraft or collect air flask samples. Um, and all of these, these air flask measurements are collected by the No Global Monitoring laboratory and then brought back to Boulder, Colorado, where all of these air flasks and the contents of these air flasks are measured on a, on a high precision instrument that tells us how much of all the gases in, in the air are in these air flasks. And so we have the, we have this picture of, um, sulfuryl fluoride levels at different tower sites and different aircraft, um, sample sites all over the, all over North America. And when we look at those measurements, we sort of see sort of like a two-sided story where the measurements that are collected in California see these really large enhancements or big spikes and the amount of sulfuryl fluoride in the air. And then if you look at the, the, the atmospheric measurements that were taken outside of California, we see re we really don’t see much evidence of sulfuryl fluoride emissions happening nearby. So, you know, if you’re, if you’re looking at tower sites in, um, North Dakota for example, you measure just about the same as you would over at the Pacific Ocean. But, um, if you look at the atmospheric measurements of sulfuryl fluoride that were collected in California, for example, there’s, um, tower sites in the Los Angeles basin and also up on Mount Wilson, um, which is right up in Pasadena, right above, um, Cal, uh, Los Angeles. You see, you see really large enhancements of sulfuryl fluoride, which indicates that there, there are emissions happening nearby.
Alex Wise | 16:25 – So Scot, when someone hears the, the story of sulfuryl fluoride and its replacement of methyl bromide in the pesticide supply chain to a policymaker, it could sound like a, a frustrating game of whack-a-mole. You know, you think you have something like methyl bromide done away with and you found this alternative that doesn’t cause problems to the ozone, but sure enough, it’s also a, a dangerous greenhouse gas. How do you hope that policymakers approach a finding like this, and what does it mean for studying other greenhouse gases?
Scot Miller | 17:08 – You know, in terms of policy recommendations, I make the argument that it’s just really important for us to understand what our greenhouse gas emissions are. Um, and you know, that sounds like a really simple question in some ways. You know, like every time you get in your car and you turn on the car and drive down the street, you’re emitting greenhouse gases. Or when we flip the light switch on, a lot of our electricity comes from, um, you know, fossil fuels that are emitting greenhouse gases, but then there are a lot of gases or some gases like sulfuryl fluoride that are much more challenging to track, right? So one thing we talked about before is that the state of California keeps track of how much sulfuryl fluoride is being used, but other states don’t necessarily keep track of of that kind of information. You know, I think if we have a better idea of the big picture of what different types of emissions are, then different political entities, whether it be the state of California or whether it be the federal government in the US can have a more accurate picture and come up with a more informed strategy as to how to reduce emissions going forward.
Alex Wise | 18:12 – And Dylan, have you and your colleagues drawn any conclusions about whether California is producing more sulfuryl fluoride or is it just measuring more sulfuryl fluoride when Scot was referring to North Dakota not having a lot of termites versus the problems that persist in California? I, is it purely just a termite issue or is it more that there’s technology in place to measure it?
Dylan Gaeta | 18:40 – Yeah, so the atmospheric measurements that we worked with have, you know, there are measurements taken all over North America and um, in most of those sites we don’t see any, or we see very infrequent or very few evidence. We, we see very little evidence of those emissions happening. Um, so part part of the reason that, that we have such clarity about what’s happening in California is that we have sort of a higher density of measurements available in California. So I think there, I want to say there’s maybe like five or six measurement sites that are greenhouse gas monitoring sites in California, whereas some other states don’t have any within that state. So, um, I think a state that also point to is the state of Florida. So part of the NOAA Global Monitoring Laboratories Greenhouse Gas Monitoring Network, um, doesn’t include a station in Florida, partly because these, um, these monitoring sites are really expensive and, and, and take a lot of human power to operate. And so it’s, um, you know, these are expense, like collecting these measurements is sort of like an expensive and time intensive operation that, that we just don’t have the resources to put these, these sensors or these measurement, um, capabilities all over the place with does high density as we would like to, but we see the atmospheric side of what’s happening in a lot of the country and we don’t see evidence for emissions happening at the, in those regions.
Alex Wise | 20:01 So, Scot, why California? What is your guess into why California stands out in terms of being an emitter of this gas?
Scot Miller | 20:10 – Yeah, so this gas is mostly used as a, a pesticide for fumigation. And the biggest thing that it’s used for typically is for fumigating against termites. And you know, obviously there are a lot of areas in the United States that simply just don’t have termites. Like from the far frigid north of North Dakota where I grew up, um, there aren’t a lot of termites there. And so, um, you know, fumigation isn’t really an issue or a problem. Um, but then as you get further south, obviously you see termites in places like Maryland, you know, where Dylan and I both live and in California. But California really has this unique problem. Um, the state has a particular species of termite that lives there called the Western dry wood termite. And this termite is unique relative to some other termite species that we see in the United States because it actually lives inside of buildings or structures like it might form colonies within the rafters of your house or within your office building, for example. Whereas a lot of the termites that we see over here on the east coast of the US are subterranean termites. And so those termites typically form nests in the ground. And so the way that you treat a termite in Maryland is often very different from the way that you treat a termite in California. Um, in Maryland you can put out, you know, bait traps where the termites will grab the bait and then take it back to their, you know, colonies in the ground. Whereas in California, you know, if these colonies are really up in the rafters of your house, the only way to get rid of them is to put a big tent around it and fi get it with sulfuryl fluoride. And so I think that kind of helps explain why, you know, you see all these circus tents in the state of California and all this sulfuryl fluoride use. Um, but why you don’t necessarily see things like this happening
(Music Break) | 22:38
Alex Wise | 23:05 – This is Alex Wise on Sea Change Radio, and I’m speaking to Dylan Gaeta and Scot Miller of Johns Hopkins. If we can take a step back and give layman an idea into how many greenhouse gases have been isolated by the scientific community and how scientists are slowly but surely trying to do studies like this for each and every one of these gases. What kind of scale are we talking about? We always hear about methane and carbon dioxide and nitrous oxide, et cetera, but I’m sure there’s a lot more that I’m not aware of. How, how does, are, are there still ones that are being discovered on an annual basis or is this, is there a finite number of greenhouse gases and we just have to dive deep into each one of them?
Dylan Gaeta | 23:51 – Yeah, so I think we have a pretty good handle on what the composition or like what greenhouse gases there are in our atmosphere. And, and there have been some efforts both from, from NOAA and from different atmospheric monitoring groups or measurement groups that, um, have keep that keep track of and measure these, the composition of our atmosphere at different places on the surface of the earth. And I think we have good handles on, you know, what’s in our atmosphere in terms of long lived species, and it’s really the long lived species that, that are concerned when it comes to, to, um, being, uh, greenhouse gases. Um, but I think the, the part that we don’t have as, as good of a handle on as we would like is, is the emission sources of these gases. You know, the question of where and how much these gases are being emitted.
Alex Wise | 24:37 – Can you give us an idea of the number?
Dylan Gaeta | 24:39 – I wanna say there’s, there’s less than a hundred.
Alex Wise | 24:42 – Okay. So it, it’s a definite number. It’s not a ian task to try to isolate and study each and every one of these thoroughly.
Dylan Gaeta | 24:50 – Yeah, yeah. It’s, it’s not like we’re taking new measurements and finding new greenhouse gases every time we look at air samples. But, but rather it’s, it’s, we’ve seen some of these compounds still show up in measurements and we’ve, for a while I think Sulfuryl flight was one of those questions where we kind of kicked the can down the road for, for a few years over trying to understand where exactly it’s coming from. We’ve just have been more so, or not we personally, but, um, scientists have been more so concerned with just keeping track of how much is it’s growing in the atmosphere and how fast it’s growing. And so sort of like the, the, the part of our work that, that we focus on is to take those measurements of, of, of sulfuryl fluid in the atmosphere and use them to, to shine some light on like where the emissions are actually coming from. So like what the sources are. So if you think of like a bathtub analogy rather than like trying to measure how much is in the bathtub, we’re actually looking at, at the flow rate of water into the bathtub.
Alex Wise | 25:45 – So what’s the solution in your mind? Is it banning sulfuryl fluoride or are there ways to mitigate its effects?
Dylan Gaeta | 25:54 – Yeah, so I, I think there’s a few options on the table that, that California or the US or or the world as a whole could, could consider in terms of ways to mitigate our sulfuryl fluoride emissions. Um, and they don’t necessarily have to be a ban or a, or a restriction or a new phase out. Um, so one, one possibility that we mention in our, in our study, um, so this, this practice of, of structural fumigation where you cover a house with an airtight tent and then pump it full of sulfuryl fluoride, um, typically after that happens, after the fume again, has wiped out all the, all the termites, that tent is opened and vent straight to the atmosphere. And so, so that’s the problematic practice, um, is that instead of recapturing our sulur fluoride after use, it’s vented straight to the atmosphere. And so, so one solution that, that, that we, that we hint at, um, is, is the idea of recapturing that gas and, and destroying it before it can enter the atmosphere. So it, it’s a, it’s a step that could be added to the fumigation process. Um, it’s one that would likely add some cost and time to the fumigation process, but it would also save, um, it would save sulfur flood emissions from entering the atmosphere. And also with that in mind, also save on some greenhouse gas emissions.
Alex Wise | 27:10 – What are the best ways to keep track of it now that you’ve been getting your hands into the process of trying to measure this greenhouse gas Dylan?
Dylan Gaeta | 27:20 – Yeah, so I think sulfuryl fluoride is, now that it’s been identified as along with greenhouse gas, I think the, the important next step is to include sulfuryl fluoride emissions in greenhouse gas accounting protocols like in the state of California, at the US level and also nationally that, um, we can have a handle on like how much greenhouse gas, how much of this gas is being emitted by different entities. Um, because until we have that information, it it’s, it’s harder to design policies that re that reduce emissions.
Alex Wise | 27:49 – Scot Miller and Dylan Gaeta, thank you so much for being my guests on Sea Change Radio.
Scot Miller | 27:54 – Thanks again. It’s been, uh, great being here and it’s, it’s fun to chat about the science that we’re working on.
Dylan Gaeta | 27:59 – Yeah, thanks for having us. It’s, it’s been nice chatting.
Narrator | 28:16 – You’ve been listening to Sea Change Radio. Our intro music is by Sanford Lewis, and our outro music is by Alex Wise. Additional music by Fog Swamp, Jerry Garcia and David Grisman and Tupac. To read a transcript of this show, go to SeaChangeRadio.com Stream or download the show or subscribe to our podcast on our site or visit our archives to hear from Doris Kearns Goodwin, Gavin Newsom, Stewart Brand, and many others. And tune in to Sea Change Radio next week as we continue making connections for sustainability. For Sea Change Radio, I’m Alex Wise.