As levels of particulate matter rise, so do vet admissions. We talk to the people doing the research.
In 2018, the Journal of Veterinary Internal Medicine published a study on the Association Between Indoor Air Pollution and Respiratory Disease in Companion Dogs and Cats. The hypothesis was logical.
The team proposed that where levels of fine particulate matter [PM2.5] were high inside a home, there would be an increased likelihood of the pets living there presenting with breathing problems. Data analysis supported the theory, although the work’s key conclusions were that cats seemed more likely to suffer than dogs, and the subject ‘warrants further attention’.
Five years ago, the Ministry of Science and Technology, Taiwan, funded another observational project. This time on indoor air pollution and pets with ‘naturally acquired’ lung or bronchial disease. Like the preceding investigation, and another 2022 pilot study of shelter dogs and air pollution in Trinidad, evidence suggests a link between atmospheric toxicity and respiratory issues in animals.
More recently, in November last year newspapers on the subcontinent, including the Times of India, stoked concerns that Delhi’s notorious air pollution problem – which spikes early winter due to the firework-heavy religious festival of Diwali – was detrimental to the quality of life and life expectancy of pets and strays alike. Animal welfare charity PETA warned of cardiovascular and respiratory issues, chronic and terminal diseases, eye infections and birth defects from prolonged exposure. Particularly among communities living on or near landfill.
Around the same time, Carnegie Mellon University’s Heinz College and the Grantham Research Institute on Climate Change at the Environment at London School of Economics made headlines much closer to home. According to their work, Britain could avoid 80,000 visits to the vet each year if the UK met World Health Organisation [WHO] safe limits on PM 2.5. This would save £15million in up-front treatment costs.
‘For every 1 µg m³ increase in PM2.5, you see roughly a 0.7% increase in veterinary admissions,’ Stephen Jarvis, Assistant Professor in Environmental Economics at the London School of Economics, and one of the study’s lead authors, tells Air Quality News. ‘A bigger picture would be: if you go from a low pollution day, say below 5 µg m³, meeting that WHO standard, to a polluted day, maybe 40-50, you’d see a 30% increase in vet admissions. So, a substantial increase,’.
Like his colleagues – Olivier Deschenes, Akshaya Jha, and Alan D. Radford – Jarvis never set out to look at air pollution’s impact on animals. Instead, he traces this work, loosely at least, back to a study of global policy fallout following the 2011 Fukushima nuclear power plant meltdown in Japan. The world’s worst radioactive incident since Chernobyl 25 years earlier, among other things it led to Germany speeding up decommissioning old reactors as fears of industrial safety rocketed. The grid quickly became more reliant on fossil fuels again, leading to an increase in associated pollutants.
Given the vast amount of research on the connection between air quality and medical problems in humans, it was possible to present evidence of the economic and public health impact of that decision. ‘It was against the backdrop of that literature myself and the co-authors began to have discussions and were surprised to find that, relative to human health, there was very little looking at the effects [of air pollution] on non-human animals.’
But with hospitalisations a key metric for human health impacts, a model for measurement was obvious – vet admissions. Using the Small Animal Veterinary Surveillance Network (Savsnet) at the University of Liverpool, it was possible to analyse appointments at 500 providers, 5% of all UK vets, which treated 3.8million cats and dogs through 7million individual appointments between January 2017 and September 2022.
‘We tried to do a bit of looking not just at the impact on total number of visits, but changes in the kinds of visit we might expect,’ says Jarvis. ‘It’s not as detailed as NHS data, but we did have some breakdown of the main presenting complaint.’
Conditions that seemed to flare up or develop when PM2.5 increased included cardiovascular problems, respiratory illness, and neurological issues. Existing illnesses were generally exacerbated. Mirroring human impacts, many of these complaints develop over long timeframes, meaning determining direct catalysts is a major challenge.
‘Unfortunately we don’t have any data on the kind of severity of the condition,’ Jha adds. ‘Maybe in the extreme we do – there’s knowledge of whether they’ve come in for euthanasia, that’s coded in the data set within the number of visits per type. There’s also a category for trauma, post-op, respiratory, and other-unwell, other-healthy, and vaccination. These are pretty broad categories and it’s only the primary noted [in our study]. There might be a collection of reasons they came to the vet.’
‘I’m not a biologist or a doctor, but my rough understanding is that the biological mechanisms by which air pollution impacts animal health are similar to the biological mechanisms by which human health is affected by air pollution,’ he continues, before explaining that behavioural variations present another area that needs to be explored. ‘We are finding some differentials for dogs and cats that might be intuitive to some – based on what we think about how much dogs are outside relative to cats… That kind of pattern, where air pollution manifests, is important.’
A split between dogs and cats is consistent with prior studies of air pollution and animals, but categorically identifying causality or even correlation at this point remains impossible. Nevertheless, the Heinz College and Grantham Research Institute work does point to some predictable rules. For example, the topline results suggest that, as with humans, older animals are more vulnerable. ‘That’s the case directionally,’ says Jha.
‘Hopefully what has come out of this study is the need to think about your own health as a pet owner, but also your pet’s health,’ he continues. ‘When you’re deciding when to take your pet for a walk, whether to keep them outside or bring them inside, taking air pollution into consideration.’
Simply put, when pollutants are concentrated enough to pose a threat to our pets and other animals, by extension they are also likely to be a risk to our own health. Which means any decision to adjust planned activities with or for your cat or dog because of air quality should also apply to you. And, like canaries in the coal mine, whose deaths alerted workers to the presence of deadly gases like carbon monoxide, animals may also be able to warn us of emerging environmental health risks before we register them.
That could involve presenting symptoms of toxic poisoning from cleaning products easily absorbed through daily grooming. Or responding to impurities in the air faster than we do because of hypersensitive senses of smell – for dogs, that’s up to 200 times more powerful than humans. All these areas demand more research. And even then, it may be the tip of a deeper iceberg. Pets are just one highly visible subsection of animals. So let’s say, what seems to be true for them will also be true for other non-humans. Now, what about high density livestock populations? Or the wild species we know are dying out, whose numbers have been plummeting in tandem with the spread of modern industry and its emissions?
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