A recent report by the Lancet Commision on Pollution and Health led to some scary headlines in the news:

Pollution linked to one in six deaths

Global pollution kills 9m a year and threatens 'survival of human societies'

Pollution is killing millions of people a year and the world is reaching 'crisis point', experts warn

That last headline doesn't appear to be a subeditor's exaggeration as one expert commenting on the report report is quoted as saying:

Air pollution is reaching crisis point worldwide, and the UK is fairing worse than many countries in Western Europe and the US,” said Dr Penny Woods, chief executive of the British Lung Foundation

and one of the authors said:

We fear that with nine million deaths a year, we are pushing the envelope on the amount of pollution the Earth can carry.

The same author also argued that:

Landrigan said the scale of deaths from pollution had surprised the researchers and that two other “real shockers” stood out. First was how quickly modern pollution deaths were rising, while “traditional” pollution deaths – from contaminated water and wood cooking fires – were falling as development work bears fruit.

So the report appears to conclude that things are getting worse and this is true even in the developed world where "modern" sources of pollution are rising.

But there is some reason to express skepticism. David Spiegelhalter, commenting on an earlier report about air pollution in the UK, analysed the reliability of the estimated number of deaths in the UK (estimated at 40,000/yr from air pollution, which is consistent with the later numbers in the new report) and found that the error bars were very wide. In addition he reproduced the following chart:

Spiegelhalter chart from DEFRA stats

and commented:

So, now we know where at least one of the popular media statistics on air pollution comes from — is it true that there is a ‘crisis’ in air pollution in the UK?

Fine particulates and nitrogen oxides have been falling steadily for decades, and are about a quarter of what they were in 1970.

So the ‘crisis’ in the UK is not because pollution is getting worse, but because there is more known about the potential harms, particularly from nitrogen oxides. But the UK is not representative of the rest of the world: many rapidly growing cities have experienced dramatically rising pollution levels.

So we have newspaper headlines and some experts claiming we are approaching a crisis and another expert claiming things are getting better but they look worse because our knowledge is getting better.

So the question arises: are we facing a growing crisis (especially in the developed world)? Or, since "crisis" is ill defined, are the major sources of pollution in developed world cities getting worse or better?

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    "Crisis" is ill-defined. Do they make a specific claim we can tackle? (About air pollution, not pollution in general, and preferably one that distinguishes between greenhouse gases and air pollution that directly affects health.) – Oddthinking Oct 28 '17 at 1:28
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    And a claim that details the region. "Pollution, worldwide, is getting worse" and "Air pollution in the UK is getting better" aren't mutually exclusive. – Oddthinking Oct 28 '17 at 1:30
  • The expert quotes I used imply that pollution is getting worse in the Developed world. Pollution is worse in developing counties (and may or may not be getting better from major causes like wood-burning indoor stoves). The contentious part is developed world pollution. And while "crisis" is ill defined we should be able to show clear evidence of getting worse or better (only getting worse is compatible with "crisis"). – matt_black Oct 28 '17 at 10:05

There is heavy pollution in some cities in the developing world. Delhi and Beijing are famous examples, but there are many more, and more people are affected than ever before because of population growth and urbanisation.

But the opposite is true in cities in the developed world. The UK graph you show goes back to 1970. But the situation in London was much worse in the 1950s (the Great Smog of December 1952 is widely known though a short-term weather pattern made things much worse) and worse still back in 1900. Take this chart from Our World in Data showing particulates in London over the longer term; it also shows Delhi is recently at levels London saw before WWII

enter image description here

And it is not just London. Another famous example for pollution is Los Angeles. The following chart from EOS Earth & Space Science News - Urbanization and Air Pollution: Then and Now shows ozone and some other pollutants falling from the start of the graph in the 1960s, though often still above modern standards set more to drive further improvement than because there is a safe level of pollution

enter image description here

Similar improvements have happened in cities across the developed world. So in summary, many cities in the developing world face vary high level of air pollution but this could be addressed, at a cost, in the same way it has been in the developed world whose cities have substantially better air quality than they used to. There may still be room for further improvement in developed world cities, but it would be a stretch to say they face an air quality crisis

  • So London and LA are improving, but how do you conclude from that about the rest of the developed world and about other nations? – Oddthinking Oct 28 '17 at 5:17
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    Your last sentence doesn't follow on from the rest of the answer at all - it comes across as unsupported editorialising. – EnergyNumbers Oct 28 '17 at 8:25
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    @EnergyNumbers If the key pollutants are being reduced, it seems like a reasonable statement. Most crises don't result from things getting better. – matt_black Oct 28 '17 at 10:07
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    @EnergyNumbers But the report claims worsening "modern" pollution in the developed world is also a crisis. The data seems contradictory. Who is right? – matt_black Oct 28 '17 at 13:23
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    @EnergyNumbers I realise I'm a newbie on this site ;-) but the latest edits to the question (posted before your comment) clarify the point about the developed world not the globe. The report makes a lot of claims and I could make several questions, but in comments and edits I have clarified the issue with whether pollution is worsening in the developed world. – matt_black Oct 28 '17 at 15:21

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