Summer smog 'killing thousands'

Industrial emissions are blamed as a contributing factor

Summer smog causes the deaths of more than 3,000 people each year, the Liberal Democrats have warned.

However, the government says the number of deaths caused by smog cannot be determined and claims the problem has lessened in the past 20 years.

Summer smog is the noxious air produced when sunlight reacts with pollutants released into the lower atmosphere.

Lib Dem environment spokesman Chris Huhne said traffic levels should be cut on hot, windless days.

Athens example

Mr Huhne said the problem needed tackling urgently.

"We need to make a much greater effort to reduce car emissions when we have particularly bad weather conditions for the summer smogs.

"I think we have to be alert, local authorities have to be alert, to the need on occasion to really cut vehicle exhaust and cut traffic flows."

Mr Huhne said the UK could learn from the example set by local authorities in Los Angeles and Athens where "quick action" is taken to limit traffic on windless days.

The party produced figures which, it said, showed that ground-level ozone had risen from 49 micrograms per cubic metre in 1997 to 59 micrograms per cubic metre last year.

Harmful ozone

Over the same period, the party said, there were 24,000 premature deaths due to the pollutant, and it warned that many more could die unless action was taken.

The Lib Dems have proposed taxing "the most fuel-inefficient cars releasing the most pollutants", at a rate of £2,000 a year.

Cars are responsible for nitrogen oxides and hydrocarbons, while industrial processes are also blamed for a range of volatile compounds.

The photochemical reactions involving these "precursors", as they are known, will create harmful ozone which can affect people's airways.

Even normally fit and health people may experience a shortness of breath, some coughing, chest tightness, or just irritation of the nose and throat.

Summer smog can also contain high levels of breathable dust, often referred to as particulate matter.