WHEN is smog not smog? When it's sunlight reacting with "ground-level ozone".

If you live or work in Cwmbran and thought your chest problems during the heatwave were caused by smog, think again.

Torfaen council says that because you can see through whatever was causing the problems, it should be called low-lying ozone pollution. As the Argus reported yesterday, soaring temperatures across Wales led to an increase in air pollution.

At a government monitoring station in Cwmbran, air quality levels were breached every day last week by smog.

And we reported how a Cwmbran GP said he had been inundated by patients with chest complaints.

However, a spokesman for Torfaen council said it was incorrect to refer to the pollution as "smog", because visibility was not affected.

He also added that the station, based in a Cwmbran secondary school, was representative of the whole of South- East Wales, and not just Cwmbran or Torfaen.

Richard Marshall, a specialist environmental health officer at Torfaen council, who deals with pollution issues, said: "It's not really smog in the traditional use of the word. What we are looking at is photo-chemical reactions with the sunlight reacting with ground-level ozone.

"If we have prolonged spells of hot weather, then this sort of pollution will increase. Air quality breached targets last week, but when you average it out over a month or a year the problem is not severe.

"This sort of low-lying ozone pollution is one generated all over the country, and therefore one of the most difficult to deal with. It's not one that we can have any effect on at a local level, unlike other pollutants from traffic and industry."

Yesterday, Dr Greg Graham, of the North Road surgery, Croesyceiliog, called on the council to warn patients and GPs about the dangers of such pollution before it occurs.

A spokesman for Torfaen council said information will appear on its website (www.torfaen.gov.uk).