“The correlation we found between exposure to air pollution and COVID-19 is not simply a result of disease cases being clustered in large cities where pollution may be higher. After all, many COVID-19 hotspots in the Netherlands were in relatively rural regions.”
We talked to one of the co-authors, Eric Strobl, a climate and environmental economics professor at the University of Bern, to hear more.
What’s new about this latest publication?
I think there are two aspects. The first is that the data used is just much better than, for instance, the study that was done in April by some Harvard University scientists in the United States. Our study is just much more localized and detailed. The Netherlands, in general, collect very good data, particularly at the regional level.
The second interesting thing is the context. In most developed countries, or even in most developing countries, a lot of the pollution is really found in big cities. Because the Netherlands is one of the biggest producers of livestock — in particular pigs and chicken, and these industries are very geographically concentrated — there’s a lot of the pollution in the rural areas; many of the hotspots are actually located there.
What do the results then tell us about the relationship between COVID-19 and air pollution?
That there's a strong association between living in an area with higher pollution, and the probability of testing positive, being hospitalized, or dying due to the SARS-CoV-2 virus, even after controlling for loads of different factors, might have played a role.
One of the things you always have to worry about pollution studies — whether it's with respect to coronavirus or just in general — is that it's usually in big cities where you have [high levels of] air pollution. And there are just so many other things going on in cities, if you want to look at just one factor [in relation to Covid]. There are questions about the role of ethnicity, maybe people in cities have poorer health in general, and we know there is more contact between people in urban centers. … It's just very difficult to disentangle any link.
Some critics said that the Carnival festivities in late February also could have been a factor in the higher rural death rates?
Yes. So we tried to take account of that by essentially identifying where the carnivals took place and calculating the distance to those carnivals under the assumption that people tend to go to carnivals live closer by. Even after we control for that, the link between air pollution and the number of cases really wasn't affected at all. So it's clearly not that much of an explanatory factor.
What are the particulate emissions in rural areas coming from?
In intensive livestock [industries] there is a lot of production of ammonia, [due to interactions of animal waste with soil and other pollutants] and ammonia is an important driver of PM2.5.
Given there is lots of livestock farming in the rest of Europe, could we find similar problems elsewhere?
One has to remember that the Netherlands has a really high population density, where their pig and chicken production is really geographically concentrated, as opposed to Germany, for example, where it's much less so. If anything, this really highlights the impact of [livestock] pollution on health in general - whereas most of the discussion is about emissions from cars. People don't really talk about the emissions that come from farming and livestock agriculture — and they're really high as well. There's almost no discussion in newspapers, among policymakers and even amongst academics in that regard. If you really wanted to reduce this part of the pollution, you'd have to reduce livestock production.
The WHO has not explicitly acknowledged the relationship between pollution and COVID-19 cases. How do you think think the global health sector — the UN, in particular — will be able to take findings like those in your study forward?
It really depends on how you read the results. The thing that we really looked at was how long-term exposure to air pollution correlates with serious illness. I guess from the WHO’s perspective, they're more interested in short-term responses to the Covid-19 emergency and how to respond to them. I think their role in trying to reduce long term pollution exposures is probably minor, apart from highlighting it as an issue.
Overall, I suspect there won't be a great response. If you look at the news coverage on the links between air pollution and coronavirus, it has mostly been within Europe. If the New York Times were to pick up the issue, or if the study had been about China, it might have been different. But even in the case of the US study — that's the one to really be the litmus test — I didn't see any response from the WHO.
Why do you think we won’t get much response from the WHO?
They seem to be working very mysteriously, especially with how they respond to many things. The problem is that they need to rely on funding from countries and are thus subject to potential pressure from these to respond in a particular way. In this regard, the WHO seems to lack transparency — in terms of how they react, or don't react.
Sometimes it's just very difficult because you have so many different interest groups kind of telling them to do this and that. I think one thing that the WHO really is lacking is a department that deals immediately with new studies or new findings, not just ours, because they're very slow in responding to these things, and clarifying their position. Yet at the same time, they would like to be seen as a source of information for all global health issues.
With that in mind, based on what you know so far, how do you think we should move forward?
If there is a second wave of Covid, or similar diseases emerge in the future, knowing where people are more likely to be infected means that you can potentially build hospitals and facilities, or have testing kits be made more available in those areas. Planning for that ahead would be a good idea.
Europe and the US were not really prepared for Covid. For example, funding for these sorts of outbreaks has declined for years in the US. Being prepared is really the key. In general, the angle of pollution should not be disregarded — including livestock sources. In terms of future disease outbreaks — and there are going to be more — and if they are transported via air, then one has to take into consideration whether reducing air pollution might help reduce our vulnerability not only Covid-19 but other new diseases.