hy cleaning the air is like taking milk out of tea

https://www.theguardian.com/environment/2018/dec/20/pollutionwatch-why-cleaning-the-air-is-like-taking-milk-out-of-tea

Gary Fuller
Thu 20 Dec 2018 16.30 EST

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Ally Lewis, professor of atmospheric chemistry at York University, likened filtering outdoor air to “trying to air-condition a room with the roof off”. The volumes that we would need to filter are vast. For example, if you drive a typical diesel car made between 2010 and 2015 for a distance of 8km (about 5 miles), it will emit around 9g of nitrogen oxides. To remove this pollution from the atmosphere in central London you would have to scrub around 150,000 cubic metres of air – approximately the volume of St Paul’s Cathedral. It is much easier to stop the air being polluted in the first place.

• With thanks to Anna Font, King’s College London for checking the volume calculation.