The Government is advising people not to use their cars - the main source of the pollution - but yesterday rejected calls to issue warnings with the weather forecasts to draw public attention to the crisis.
The pollution - by ozone and nitrogen dioxide, the two gases increasingly linked with the asthma epidemic that affects one in every seven British children - is being aggravated by the heatwave. Sunlight forms ozone out of the pollutants emitted from car exhausts, and calm, still weather allows it to build up without being blown away by the winds.
As the crisis began to build up on Friday night, Robert Atkins, a junior environment minister, asked people to 'think carefully' about whether they needed to use their cars and not to leave engines running unnecessarily.
Yesterday, that warning appeared not to have been heeded by people heading for the coast to escape the sweltering weather. According to the AA, main routes were busy with holiday traffic all day, heading mostly to the south coast and the South- west. Among the more congested roads were the M5 through Avon, the A38 around Exeter and the M3 in Hampshire.
The Government also asked people not to overfill petrol tanks and to avoid using paints, varnishes and glues containing solvents - all of which can increase ozone formation. It also advised people suffering from asthma or chest disease not to take vigorous exercise.
But the 'summer smog' worsened yesterday. South-west and southern England, mid- and south Wales and the Midlands all suffered ozone levels exceeding World Health Organisation safety levels and high concentrations of nitrogen dioxide were measured in central London.
The pollution is forecast to get worse tomorrow.
The Department of the Environment last night described the crisis as the worst so far this year, and Fiona Weir, senior campaigner for Friends of the Earth, said that it looked like being the worst outbreak of summer smog so far this decade. But it is not as bad as the worst incident of all in recent years, a build-up of nitrogen dioxide in London in December 1991 which, as the Independent on Sunday reported last week, is thought to have killed 160 people over a weekend.
The Government is updating air pollution data hourly on Ceefax (page 404) and Teletext (page 187) and provides information and advice on a free helpline (0800 556677) but it last night rejected a call by Friends of the Earth for smog warnings to be broadcast with the weather forecasts.Reuse content