Air pollution and pet health

[Music] Welcome to Science Sessions, the podcast of the proceedings of the National Academy of Sciences, where we connect you with Academy members, researchers, and policymakers. Join us as we explore the stories behind the science. I'm Paul Gabrielson. Air pollution is known to have serious health effects on people, but people aren't the only ones breathing in bad air. Cats, dogs, and other pets that live their lives alongside humans are also exposed. In a recent PNAS study, Steven Jarvis of the London School of Economics and Colleagues, compared air quality with veterinary visits. They found that veterinary visits rose on days with poor air quality, suggesting another dimension to the costs of air pollution. Steven, how did you become interested in air quality effects on pets? There's a sort of academic reason and a more anecdotal one. There really is a growing set of academic research, really studying the impacts of environmental pollution, often on human health. But increasingly, there's a lot more people, including economists, who've become interested in impacts on animals and biodiversity. And some of my co-authors have actually done work before on air quality and human health. We kind of got wondering if some of these same effects we see in humans are also something that we might be able to study using the same sorts of methods, but in animals instead. From my own experience, I lived in California for a while during my graduate studies and lots of sort of bad wildfires during that time. And definitely I noticed for the first time those real symptoms from being exposed to particularly poor air quality. But my partner and I, we did also notice some symptoms in her cat, who would also seem to be having a difficult time during some of those really polluted days. That might have also helped spark off some of these ideas of maybe we can look at these things, not just in humans, but in animals as well. How similar is air pollution exposure for pets and for humans? It's actually going to be very similar to humans. I mean, these are companion animals. They spend a lot of time indoors in our homes, but also take them out for walks. They're living in human urban environments, in many cases. And also, than any other animal, they really are exposed to very much the same sorts of air quality that we are, whereas you can imagine lots of animals in wildlife might have very different exposures. So I think they're actually a sort of very special case where the exposures are very similar to humans. Tell us about your data set. What records did you examine and what were you looking for? In the human health literature, increasingly a lot of the research draws on large administrative data sets, where they get information on hospital admissions, GP practices. We use something very similar to what you would find for humans, but in the pet context. So we partner with some colleagues up at the University of Liverpool, some veterinary scientists, who essentially gather a bunch of information about vet consultations from participating practices around the UK. And so we got information on about seven million vet consultations spanning about five years. And the main sort of thing that we then do with that was essentially matching that up with what is the local air quality in your region on that specific day. And can we see some relationship between days when air quality is really bad and changes in the kind of vet admissions that we see at different practices? How were air quality and veterinary visits correlated? The real benefit of having this big data set, not just in terms of the number of vet consultations, but also being able to see these different places across the whole country and follow them over time, meant that we could essentially look at in a given region, if there's a sort of shock or a suddenly very polluted period, do we see abnormal rise in admissions for pets to veterinary practices around at the same time? And the short answer is yes, we did see that there was this correlation, this clear relationship between increased incidence of poor air quality. We were really focusing in on what's called fine particulate matter, very small little particles of dust or pollution that get deep into your lungs and can cause these physiological problems. That was the main pollution that we were tracking. And on days when that was pire, we could see this increase in veterinary admissions for both cats and dogs. Does the data suggest any outcomes associated with poor air quality? The main thing we were initially looking at was just aggregate vet visits for any particular reason, and we can see the effects show up in the call calls visits. We did have a little bit of information about the kind of main reason for the visit, but it was pretty coarse. It was encouraging in the sense that we didn't see increases in visits for things that we don't think should really be affected by air pollution. So this could be like vaccinations or like a trauma visit or something like that. So most of the increase was really coming in this broad category of other unwell, but I think what we'd love to know more about is what the underlying mechanisms were that were really driving those particular visits. Cats and dogs are mammals too, and they probably have the same sort of physiological responses that humans do. So I think in general we expect impacts on sort of cardiovascular, respiratory, neurological conditions and just the exacerbation of existing morbidities that animals might have. But that's a key area that we would love to look into more is getting some more detailed information about the specific reason for the visit, the kind of things that were prescribed or done. How could improving air quality help pet health? I think the short answer is quite a bit. As we see in people, it's also the case with animals, decreasing air pollution, would based on the kind of data that we have, mean reduced vet visits. You could view that as indicative of improved health for animals, but also reduced cost and stress for pet owners. It's expensive taking your pet into the vet. There's a lot of hassle and stress and time costs of doing it as well, beyond the just physical health and well-being of your pet. Decreasing air pollution in the UK as an example so that it meets the World Health Organization standard would probably reduce aggregate vet visits by about 0.7 to 2.5% relative to current levels. Which, you know, when you add that up based on the total number of visits we're talking like tens of thousands, hundreds of thousands of visits potentially per year. What are the takeaways from the study? One thing that it really does bring to mind is trying to be mindful of pollution levels, particularly what the conditions are outside. I think as more of us experience and become more educated about the harmful effects of air pollution, not just on people but also on animals. Being cognizant of how polluted it might be outside on a given day is probably an important thing to keep in mind. And maybe that can affect your decisions around whether you're going to go out for a run or take your dog out for a big walk on a day like that. Even when going outside and taking pets for walks. It's not just thinking about what my weather app tells me the pollution level is, but also, you know, where are you going? Are you walking along a very busy congested street during rush hour, whether it's going to be a lot of pollution versus being an area where that's not the case. Most of what I've just said is about outdoor air pollution. But if you think about humans, but also pets, we spend actually the vast majority of our time indoors for some pets. It might be exclusively indoors for an indoor cat. The other thing to keep an eye out for is air pollution exposure indoors as well. I've got some colleagues here at LSE that have been doing some really interesting work on indoor air pollution and showing that can be really substantial increases when you're doing certain activities at home like cooking or lighting candles or if you have a wood burning stove. And in those situations, even pretty simple actions can really help reduce exposure both for you and your kids, but also your animals opening a window, closing the kitchen door, running an app, you're a fire if you have one. Those are all things that people can keep in mind when they're thinking about dealing with air quality and health and the well-being of themselves and their pets. What are the caveats or limitations of the study? Definitely don't think this is the last word on this issue. There's more that we would love to know about the exact physiological mechanisms that are at work here. That's definitely a limitation of our work and an area where further research will be nice. The same on indoor air quality versus outdoors. A substantial majority of all the research, including on human health that's looking at air quality is really relying on outdoor measures from pollution monitors. And there's just much less data available on indoor air quality. Sometimes it can also be pretty tricky to disentangle the impacts of different kinds of pollutants. We focused on particulate matter, which is thought to be like the main and one of the biggest sources of health impacts. But in principle there are other pollutants, nitrous oxides, volatile organic compounds, things like that that can also impact health. So I think that's another limitation to flag as well. Thanks for tuning into science sessions. You can subscribe to science sessions on iTunes, Spotify, or wherever you get your podcasts. If you like this episode, please consider leaving a review and helping us spread the word.