http://uk-air.defra.gov.uk/forecasting/?day=1
Edinburgh forecasting 4ish = Moderate, slightly higher along the east coast. Given Edinburgh's current high-levels of atmospheric pollution on "arterial" routes, it could be even higher along these.
A number of papers / newsmedia have spread the misinformation by trying to portray that this is somehow "foreign" smog, "blowing in" from the continent. Actually it's the weather system that makes smog more likely to form that is moving in from the continent, the atmospheric pollution is all home grown, made-in Scotland and/or UK. And given that it's a northeasterly system, it's probably a load of cobblers that it's anything to do with the continent. But you know, nothing like the meeedya whipping up a bit of cheap continent-bashing sentiment. Either way, it's our own mess now we've got to breathe it.