At one point during Covid, I tried (not very hard at all) to float a conspiracy that the vaccine was in fact not the poison, but the antidote. That Covid was deliberately designed by governments to filter the 'independent thinkers' (who won't take the vaccine) from the sheep (those who do take the vaccine). So by not taking the vaccine, you were giving the governments what they wanted.

This was because the conspiracy that governments were killing the loyal sheep with the vaccine, therefore only leaving the 'independent thinkers' behind, made absolutely no sense at all to me.

In this case:

"While we would expect children's lungs to grow year on year, our results indicate that the London children's lung growth had accelerated during the four years to 'catch up' with the control group in Luton to reach similar levels of lung capacity," researchers say.

"I was absolutely stunned when I first saw the results," Prof Chris Griffiths, a senior author on the study, at Queen Mary University of London, told the BBC.

"The speed of catch up in lung capacity in the London group was surprising and impressive."

"Levels in the raw 2S scooter exhaust were as high as 300,000 μg m−3 or 146 p.p.m.(v) from idling. The EU annual mean limit for the protection of human health is 5 μg m−3 (ref. 13), while the US National Institute for Occupational Safety and Health recommends that workers wear special breathing equipment when exposed to benzene at levels exceeding 1 p.p.m. for 15 min. Waiting in traffic behind a 2S scooter, for example, at junctions and while the scooter is idling, may therefore be highly deleterious to health." [0]: http://dx.doi.org/10.1038/ncomms4749

But cities are full of shitty mopeds and old Vespas, for no benefit but cultural cosplay reasons.

We don't all live in the city.

In some areas of London the ULEZ has been so successful that the measured NOx is now coming mostly from gas boilers used for heating, probably mostly old large commerical units.

So shifting from gas boilers to heat pumps and from gas ovens and stoves to electric/indusction is also beneficial.

So yeah.

That said not clear to me about PM2.5 is I've never seen anything legit seeming that tries to characterize the harm based on the type/source. Though it seems agreed diesel is especially bad.

I assume you mean that the increased air-exchange (purified or not) helps CO2 that originates inside the house to leave promptly? (Equalizing it with the outdoors.)

Literally "keeping CO2 out" is a much trickier and more-expensive proposition.