The Researcher's Perspective Podcast Interview with Dr. Kristie Ebi Narrator: EHP presents The Researcher's Perspective. Ernie Hood: Welcome once again to The Researcher's Perspective, the podcast series from Environmental Health Perspectives. I'm your host, science writer Ernie Hood. On this episode of The Researcher's Perspective, we are honored to welcome Dr. Kristie Ebi to the program. Dr. Ebi is one of our leading authorities on the potential impacts of climate change on human health. She is an independent consultant and has served on numerous scientific panels, including the highly influential Intergovernmental Panel on Climate Change. In November 2008, Dr. Ebi and co-author Professor Glenn McGregor of the University of Auckland in New Zealand published an important review article in EHP entitled Climate Change, Tropospheric Ozone and Particulate Matter, and Health Impacts. That paper will be the topic of our discussion today. Dr. Ebi, welcome to The Researcher's Perspective. Dr. Ebi: Thank you. It's a pleasure to talk with you. Ernie Hood: In that November 2008 article in EHP, you reviewed dozens of studies modeling the potential impact of climate change on human health - could you briefly summarize for us what you found? Dr. Ebi: What we found is that holding the precursor emissions constant, that is, the emissions from plants and primarily from tailpipe emissions that lead to the formation of secondary pollutants, in this case primarily ozone, if you hold the emissions constant, as the temperatures continue to warm, because ozone is formed on clear, cloudless days, and the rate at which it is formed is temperature-dependent, therefore as temperatures go up one would expect, and indeed the model suggests that there would be more ozone. Ozone is a lung irritant, and the consequences therefore would be more illnesses, injuries and even in some cases some deaths due to higher ozone concentrations. Ernie Hood: Dr. Ebi, the studies you reviewed employed a wide range of scenarios and modeling methodologies. How were you able to step back from all of that and draw any conclusions? Dr. Ebi: The studies used a fairly small set of scenarios, and the scenarios are used to run the climate models. The scenarios tell us things like how many people there'll be in the world, where they're going to live, how wealthy they're going to be, what kind of technologies they're going to use. From those, one can then determine how many greenhouse gases will likely be emitted, which are put into the climate models to tell us how much temperature would change. And in fact these studies use a fairly limited set of scenarios to see what might happen with greenhouse gas emissions and then how the temperatures might change as a consequence. There are a whole range of models that were used, and it is difficult to step back and look across those, but in fact, to understand the body of literature, one has to do that and take into account that the models are different. The fact that the models are different is both strengths and weaknesses. It gives you variability in how the studies were conducted and the kinds of results that are reported out, but the strength is that similar results were reported across a whole range of modeling studies, suggesting that it's unlikely there's one particular bias across all the studies that would lead the results to be too high or too low. Ernie Hood: Tell us about the Standardized Reference Emission Scenarios, or SRESs. What are those, and how were they used in these types of projections? Dr. Ebi: As I mentioned, the SRES...the SRES are a set of scenarios that were developed by the Intergovernmental Panel on Climate Change for use by the impacts community, and there are four basic sets of scenarios within these. And really the bottom line is how many people will there be in the world, where do we think they're going to live, what kinds of lives are they going to live, how wealthy will they be, what kind of technologies will they use? If you assume you've got a fairly high growth, a high demographic change across the world, you've got lots of new people being added to the world, and we follow the kinds of emission pathways we've been following, which would lead to higher greenhouse gas emissions, that would lead to greater temperature change later in the century. If you assume that indeed there will be fewer people in the world and that there will be a greater emphasis on technology development so that people would use what we'd call green technologies, there'll be fewer emissions, fewer people emitting those emissions, and so one would see less temperature change later in the century. And there's variability around those, of course, but that's the basic idea behind the SRES scenarios. Ernie Hood: What is the outlook for potential increases in ozone levels as the planet gets warmer over the next century? And along the same line, what are the implications of those increases for adverse effects on human morbidity and mortality? Dr. Ebi: These studies all assume that you hold emissions constant because that is one of the sources of uncertainty in looking at these studies. And that means how well will we control emissions from power plants and tailpipes? And if we assume current levels of control-we don't change that over time-then as the temperatures warm, and if the degree of cloudiness remains the same, so we have the same number of clear, cloudless days, then ozone concentrations would be expected to increase. And as they increase, people who have a whole range of cardio-respiratory diseases, from asthmatics to people with cardiovascular disease, find that extra concentration of ozone in the atmosphere stressful. So it does lead to higher morbidity. It leads to more hospitalizations, and it leads to increased numbers of deaths. Ernie Hood: What about the projected situation with regard to particulate matter? I understand that the impact of climate change on particulate pollution and the potential impact associated on human health has actually been less studied than the ozone projections. Dr. Ebi: Particulate matter has been significantly less well-studied, and it's more complicated because certainly in northern regions, the US and Europe, what we've seen over the last century is a twenty percent increase in heavy precipitation events. We see the same number of rainy days; when it rains, it rains harder. When it rains harder, it tends to wash the particulates out of the sky, basically. And trying to project from the climate model side what's going to happen with those heavy precipitation events is much more difficult than projecting what's going to happen with temperature. So people are trying to understand how they could model what would happen with particulate matter and thinking of ways that they can incorporate this change in raininess and what the consequences might be. There are a number of studies that should be coming out sometime soon. The Environmental Protection Agency has been funding some research looking at the atmospheric chemistry around this very issue, and certainly all of us are looking forward to seeing those results when they come out. Ernie Hood: You mention the EPA, and it's appropriate in that in the paper, you mention that the degree of regulatory control over ozone and particulate matter emissions is expected to increase in the coming years, which could actually affect the impact of climate change on those pollutants. Could you elaborate on that point? Dr. Ebi: There's two points in here. One is, as I said previously, you need the precursor emissions, and if the regulations control those, more of the precursor emissions to ozone, even if it's warmer, one would see less ozone. On the other hand, one of the sources of the precursor emissions are a whole range of plants, and as the temperatures get warmer, there is some concern that with additional plant growth maybe the plants will be emitting, and there has not been the work to understand how that balance might play out. We do know right now in the U.S. there's quite a number of areas that cannot reach the ozone standard. Certainly, ozone concentrations go up in many areas. Ernie Hood: Dr. Ebi, as you summarize your findings, you state that "there is high uncertainty about future projections." With that caveat in mind, what do you see as the main take-home message of this paper? Dr. Ebi: The message is, if we hold emissions constant, because that's a significant source of uncertainty, that all else being equal, climate change is likely to make - it will make it then more difficult for communities to try and reach their ozone standards. It will adversely affect people in the community. It will place a greater burden on healthcare. It will place a greater burden on the public health infrastructure. So it will be something that I think could potentially be important given all of the uncertainties about these kinds of projections, but certainly it is something that EPA is thinking about -how they could possibly handle - and cities need to think about what they would do, and what are the options for them to try and reduce precursor emissions to help protect the health and safety of their populations? Ernie Hood: In the article, you also write that "if improved model experiments continue to project higher ozone concentrations under a changing climate, rapid reductions of emissions from fossil-fuel burning are needed to protect the health of current and future generations." Is that really the bottom line here, Dr. Ebi? That we must act and act quickly to mitigate the potential future circumstances? Dr. Ebi: Certainly for this issue, we do definitely need to mitigate. Looking across all of the possible health outcomes that could be affected by climate change, we also need to adapt. We need to look at what kinds of things can be done to help people adjust to the changes. Do we need additional regulations in this case? Do we need to change our regulations? Do we need to think about, for example, when kids go outside? Do we want to make changes so that there is less exposure, perhaps, to ozone outside (although it does quickly come inside)? Are there ways that we can make adjustments now that would help people cope with higher ozone concentrations, at the same time reducing the precursor emissions so that less ozone would be formed in the first place? Ernie Hood: How can additional research shed further light on these important questions that you've been discussing? What is the best direction for the research to take at this point to provide us with the answers we most urgently need? Dr. Ebi: There's a broad range of research needs, as outlined in the article. There's lots of uncertainties. Right now, although there have been a number of studies projecting what could happen with ozone, they're in very limited geographic areas, and we do need to understand how ozone could change across a variety of geographic areas to provide more local-scale information for decision makers. We talked about particulate matter; there's lots of uncertainty about what might happen with particulate matter. Very few studies have taken a look at this. So more research needs to be done on how those could interact. There obviously needs to be research on, not only from the health perspective but from other sectors' perspective, of what are the options for reducing emissions that lead to ozone. I know there's a lot of technology development going on. There's other ways that we may be able to explore to reduce those emissions as quickly as we can, and that's all the way from the technology to getting people to do things like walking more, which would help from a whole range of health perspectives, not using their automobiles quite so much. And how do we communicate that - that the public needs to understand these potential risks, understand what kinds of actions that they and their governments need to take? How do we best communicate so that we can motivate the right kinds of changes? That's some of the research that's needed. Ernie Hood: So are you generally hopeful about the situation? Dr. Ebi: I am generally hopeful about the situation. There are lots of potentials for very severe consequences, and there's increasing attention being paid to this, and very, very smart and dedicated people working on the research, the communication and trying to find solutions. And I think the more that people engage and think about how to deal with climate change, the more possibilities we have of finding the solutions that will help us in the short and in the long term. Ernie Hood: Dr. Kristie Ebi, thank you so much for joining us on this edition of The Researcher's Perspective. Dr. Ebi: Thank you. Ernie Hood: And thank you for listening to The Researchers Perspective, the EHP podcast. Join us again next time as we explore another unique perspective in the environmental health sciences!