'Super-smog' warning

Pollution from cars could combine with pollen to create a dangerous "super-smog" across London, experts warned today.

Scientists have discovered that the chemicals in exhaust fumes react with pollen and other particles in the air, turning them into irritants capable of triggering asthma and respiratory illnesses.

They claim that up to five per cent of the air we inhale could be affected. "There is evidence that allergies are on the increase, and this could help answer why," said Professor Ulrich Pöschl, who led the research.

His team found that a mixture of nitrogen dioxide and ozone, both producedby vehicles, is capable of making pollen, a known allergen, more potent.

They may also make even benign dust allergenic. The findings will be of great concern to parents. With almost one and a half million children living with asthma, Britain has one of the highest rates in Europe.

It is believed that London's air pollution has caused hundreds of premature deaths . Professor Pö s c h l ' s team from the Technical University of Munich collected samples of urban dust. Only 0.1 per cent of the proteins in the dust collected in open spaces had been nitrated by traffic smog, they found. But for birch pollen left at a busy road junction for a few days, that figure rose to 10 per cent.

The findings could help to develop drugs that stop nitrated proteins disrupting immune systems.