Whether this level of pollution is something we absolutely have to put up with is debatable. But that there is a trade off is certain, a point which isn't being grasped here:

An average car in inner London will be responsible for almost £8,000 in health costs during the course of its lifetime, researchers say.

Pollution produced by vans and cars costs almost £6 billion in damage to health annually in the UK, according to experts from Oxford and Bath universities.

They said that exposure to nitrogen oxides and fine particulate matter caused by vehicles – particularly those which run on diesel – is linked to about 40,000 premature deaths a year.

This translates into billions of pounds in associated costs for healthcare and “life years lost”, the study, released ahead of Clean Air Day on June 21, found.

This also leads to costs of £650 million in London alone.

Leave aside whether we think those cost estimations are correct or not - let's just assume they are. So, what else do we need to know?

What is the benefit which comes from these same activities? If we want to think about cars alone, then the ability to get around seems to be something that we humans rather like. That's why every society in which people have been able to afford a car they go and buy one.

Note that the insistence is not that those third party costs of the pollution are justified by that desire to be able to transport oneself. Only that it is the correct question to be asking - Yup, we've costs here, are they justified by the benefits?

Similarly with those £650,000,000 costs in London. The same 10 million people in that same area also produce some £ 378,424,000,000 in economic value each year. Or some 500 times those costs. Is that worth it?

No, we don't say we know the answer - we've an intuition that a bit of pollution is inevitable with 10 million people in the same river valley - but that is the correct question. Knowing the cost is useful, but only because it's part of the correct question, is it worth it?