Does air pollution really kill nearly 9 million people each year?

By Michael Le Page

Air pollution in Krakow, Poland is high above European Union limits
Air pollution in Krakow, Poland exceeds European Union limits

Artur Widak/NurPhoto/Getty

Does air pollution really kill nearly 800,000 people in Europe and 9 million worldwide each year? That’s the apparent conclusion of a study claiming that air pollution causes 800,000 “extra” deaths in Europe each year, which is double previous estimates.

However, the figures do not mean that 9 million people dropped dead solely because of air pollution. Rather, they are a way of representing the harm done by air pollution.

This is not to say that air pollution isn’t dangerous. In fact, this study suggests it is a bigger killer than smoking, which using the same method is estimated to cause 7 million extra deaths worldwide each year.

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“I think that’s the important message of this study,” says lead author Jos Lelieveld of the Max Planck Institute for Chemistry in Mainz, Germany. Air pollution has now joined the ranks of major risk factors such as high blood pressure, diabetes and obesity, he says.

Adding up the damage

It is important to understand where these numbers come from. Working out the damage done by air pollution is much harder than something like car accidents, for which we have firm figures, because it typically aggravates the effects of common disorders such as respiratory diseases.

Many teams around the world have been doing long-running studies that compare, say, people living in areas with different levels of particulate pollution to work out how it affects the risk of developing respiratory and cardiovascular diseases.

The latest results suggest air pollution is a far greater contributor to cardiovascular disease than previously thought. But telling people their “hazard ratios” for air pollution – the standard scientific measure – would mean nothing to them.

Instead, it is standard practice to translate risks into more meaningful measures. Lelieveld’s team combined the latest risk estimates with data on people’s exposure to air pollution in Europe to work out the number of extra early deaths in 2015. “790,000 people died who would have died later if there was no air pollution,” says Lelieveld.

Everyone dies

Of course, everyone dies sometime. Another way to express the same finding is that those 800,000 people lost 17 years of life on average, or that the average person in Europe loses two years of life due to air pollution.

“These are just different ways of spreading the total days lost among different groups,” says David Spiegelhalter of the Winton Centre for Risk and Evidence Communication in the UK. “It’s a confusing area.”

Yet another way to express the risk is that there are 120 extra deaths per every 100,000 people per year. Put that way, it might not sound too bad. But we don’t regard, say, the 3 people murdered in Europe per 100,000 per year as remotely acceptable.

Read more: Cutting through the smog: 5 ways to slash your pollution intake

The situation is not especially bad in the UK. Air pollution causes 100 excess deaths in the UK each year, compared with 140 in Italy, 150 in Germany and over 200 in eastern European countries such as Bulgaria, Croatia, Romania and Ukraine, according to the study.

The bigger picture is air pollution has been gradually falling over the decades in Europe due to tighter controls on vehicle emissions – though in some places a rise in wood burning is counteracting this trend.

So air pollution contributed to far more deaths in the past – we just didn’t know about it. Only now are studies like this revealing the full impact of air pollution. Ironically, this is partly because falling pollution levels mean we now have better data from less polluted areas, says Lelieveld.

Journal reference: European Heart Journal, DOI: 10.1093/eurheartj/ehz135

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