Many people have already noticed. If you look closely at the map with the number of hospital admissions, a few municipalities stand out. How is it possible that corona strikes faster in some regions than in other parts of the Netherlands?
For example, the share of hospital admissions in Amsterdam is relatively higher than in surrounding municipalities. But corona also seems to have struck a lot in a number of municipalities in East Brabant and North Limburg.
Is there an explanation for that? Many see a connection with air pollution. Where the air quality is poor, more people seem to get very sick from the corona virus.
Many pig and goat farmers
Some go a step further. They specifically point to air pollution caused by intensive livestock farming. Corona strikes hard in places where there are many pig and goat farmers. But is that comparison correct, or is it a coincidence? Let’s go deeper into that first.
First look at the map below. Indeed, it seems that in places with many livestock farms, more people need to be admitted to hospitals.
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So there is a connection. That does not necessarily mean that the air pollution in these places is really related to it.
Is it a sham relationship?
It could be a sham connection, called a cofounder in science, says professor of preventive medicine Onno van Schayk. “Like: I smoke cigars, I get yellow fingers, so yellow fingers cause lung cancer. The fact that there is a statistically proven connection does not mean that there is a causal connection, that the one factor is caused by the other. “
Suppose that many livestock people live in poor health around livestock farms or that many more elderly people live here, then there could be such a sham connection: these local residents are not necessarily sick by the dirty air, but because they already have a worse have health.
Nevertheless, there is increasing evidence that air pollution plays a role. “In general you can say: the connection has been established independently in several places in the world. In Italy, the US and the Netherlands. This makes it more likely that it has something to do with each other.”
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In a ‘impressive publication’ of the World Bank, which mainly concerns the Netherlands, according to the professor, they managed to correct ‘quite clearly’ for those sham factors.
For example, the density and health of the population was examined. Because if more people live in a certain place, they will have more contact with each other. Then that could be the explanation. “This was not the case in Italy and the Netherlands. Where the population density is the highest, most infections and hospital admissions are not necessarily determined by definition. So there also seem to be other issues at stake.”
Carnival
Can it be carnival? In the west of North Brabant, that was a likely explanation at the start of the epidemic, says the professor. “People who contracted the virus in Italy have been able to infect many people during Carnival. But as time went on, you see that especially infections on the east side of North Brabant have increased, much less than in the Randstad.” Moreover: in other cities in Brabant, carnival has been just as hard and there are fewer infections.
Carnival and population density do not seem to be the only explanations.
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“Are there any mechanisms that can explain the connection?” Van Schaijk wonders aloud. In other words, suppose it has to do with air pollution, does that make sense?
Virus and particulate matter
The professor gives the answer himself: “The Italians have investigated that the virus is also on particulate matter in the air. So they investigated whether the virus particles attach to particulate matter, and that appears to be the case. So viruses are probably found on particulate matter. The only question is whether it also contributes to the spread of the infection, because it may well be that the virus particles on particulate matter are no longer viable. They have not yet been able to determine that. “
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Q fever
It is not surprising that the accusing finger suddenly goes to livestock farms. Northeast Brabant, where the coronavirus has hit hardest, is also the region where Q fever broke out just over a decade ago. A link with this disease and the goat farms in this area has been shown: people get Q fever by breathing air in goat farms that contain the bacteria.
Whether the air quality around livestock farms does indeed influence the impact of the coronavirus is also being investigated by RIVM. “The extent to which there is a causal link is currently unknown,” Minister Schouten recently wrote to the House. “I asked RIVM to investigate the possibilities for research into the relationship between air quality, livestock farming and Covid-19.”
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Plausible explanation model
Another explanation: in many people who live in the areas where the air is polluted, the lungs are already affected, for example because there are more inflammations.
“Most likely, we know that the virus attaches to ACE-2 receptors. These are proteins that are in the lungs, for example. The virus uses these proteins as targets. These ACE-2 receptors may increase when exposed polluted air. People who smoke also have more of these receptors. “
The scientist calls this a ‘plausible explanation model’. “As the aforementioned associations are found in more places around the world and there are logical explanations, the more likely there is a causal relationship,” he says.
But much more research needs to be done first: by no means everything has been explained. “We see that in places where there is a lot of ammonia and particulate matter in the air, there are sometimes also fewer infections. Before we can say that intensive livestock farming in the east of North Brabant and North Limburg is a cause of Covid-9- infections, we will really need to do a lot more research.
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