Heat brings smog danger

The record heatwave is pushing air pollution in London to dangerous levels, scientists warn today.

A thick smog has already submerged much of the City as the combination of soaring temperatures and a lack of wind traps harmful ozone gas at ground level.

The term smog dates back to 1905 and was coined to describe the cocktail of pollution from industry and burning fossil fuels in major cities.

It is the combination of gases mixed with water vapour and dust which hangs heavier than air and forms when heat and sunlight react with particles in the air from burning fuels.

It is strongly linked to heavy traffic and high temperatures - stagnating in calm winds to blanket the ground.

The most harmful components of smog are ground-level ozone and fine airborne particles from exhaust fumes.

Many Londoners are reporting breathing problems and doctors have warned asthma sufferers not to exercise outside, especially in the afternoon when ozone levels are predicted to soar.

Scientists say 12 areas of the capital have high levels of pollution, and experts predict many Londoners will start to suffer asthma and other respiratory diseases as the hot weather stretches into next week.

The searing weather makes normal pollution levels worse because the hot air enveloping London at night stops the ozone from dispersing.

Central London's record-setting 35.5C (95.9F) was the highest temperature yesterday, but the ozone problems are even worse in suburban areas like Kingston, Richmond, Croydon, Greenwich, Bromley and Sevenoaks.

This is because in central London nitrogen oxide pollution from cars destroys ozone. But further out of town, where car emissions are lower, the ozone is able to build up.

Timothy Baker, a senior air quality analyst, today said the quantity of ozone in the atmosphere would mean dangerously high levels of pollution if the heat-wave continues. He added: "Ozone is usually generated during the day and disperses at night. But at the moment that is not happening, so each day we are having a greater buildup of ozone.

"If this hot, sunny, still weather continues as predicted then pollution will reach a continuous high."

Scientists have recorded higher ozone levels in the past, but they say London is now in one of the longest periods of prolonged high-ozone pollution ever seen.

Smog poses a serious threat to our respiratory system. Illnesses that can be triggered or worsened by high levels of smog include:

Asthma sufferers are particularly at risk from the current air quality and are being advised to take extra care when outside. Increased levels of particulates are also hazardous for anyone suffering from respiratory problems and can even cause premature death.

Professor Martyn Partridge from the National Asthma Campaign said: "Over 80 per cent of people with asthma find air pollution makes their asthma symptoms worse. This is of particular concern during the summer months when ground-level ozone increases."

Smog is currently reducing the amount of sunlight hitting the earth's surface by 10 to 15 per cent. It is now most prevalent in southern and central Asia where forest fires, emissions from cookers, the burning of agricultural waste, increases in the use of fossil fuels in vehicles, old-fashioned, dirty diesel engines, and ancient power stations all create a toxic blanket of chemicals.

But scientists predict that smog will choke the northern hemisphere by 2100. The doomsday scenario would see pollution levels in the air triple, destroying vegetation, speeding global warming and making breathing illnesses soar.