In reply to felt:
Woodburning stoves contribute to PM2.5 concentrations. Of that there is no doubt.
However, we need to drill down into the data a little bit. The headline figure is that 38% of PM2.5 comes from open fires and stoves burning coal and wood. But this is a mix of the very bad - open fires with a mixture of damp wood and coal smouldering away - to the very good - efficient closed stoves burning properly dried wood at high temp.
The document does not give any actual data on the impact of different fuels, beyond saying that coal is the worst and dry wood the best. But it does give figures for the methods of burning which show that a good stove releases about 11% of the emissions of an open fire and 13% of a poor stove.
From here we're into educated guesswork because we have no way of knowing if the 38% of all emissions are because lots of people are using good stoves and dry wood, or because a few people are using wet wood and coal on open fires.
On the type of appliance: a 2016 survey suggests that 40% of all domestic combustion was open fire (and 50% stoves, and presumably the remaining 10% pellet boilers, ranges, or other systems).
Source: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/833061/Summary_results_of_the_domestic_wood_use_survey_.pdf
On the fuel source: of all the people I know who have woodburners, some are fastidious about using properly dried wood. Some are less fastidious. Some use whatever they can get their hands on, up to and including damp pallets and painted wood. I'd say less than half use coal.
So I would suggest that, of the headline 38%, a vast majority of the PM2.5 contribution is coming from people using inappropriate fuels on inappropriate devices. If everyone switched to a modern stove burning clean dry wood, I would guess that figure is going to drop by more than a factor of ten.
Is that acceptable? I'd say sometimes. I don't think I would put even the cleanest woodburner in, if I lived in a city centre, and I even think I would support legislation preventing any more installations in heavily urban areas. Cities tend to be clustered around rivers and in bowls with surrounding countryside rising up, so air pollution gets caught in the bowl. OTOH I can't see much a of a problem with a good clean burning stove in less densely populated areas.
TL:DR What we need to do is get rid of all the open fires, and stop people burning crap.