Other large cities, such as New York, Los Angeles and Berlin, have a much lower level of pollutants in the air than Hong Kong. Pollution levels here are more on a par with cities such as Bangkok and Jakarta, yet the level of social and economic development in Hong Kong is well ahead of these cities.

The most pressing need is to look at reducing the effect of the pollutants on young children.

'Nobody should be smoking in a home where a child lives, not even on a balcony. A neighbour's smoke can even affect a child. Even if you can't smell the smoke you can breathe it. It's the tiny particles in the air that have the effect,' he says.

To combat the effects of pollution, Professor Hedley suggests adopting a healthy diet. 'Eat leafy green vegetables and citrus fruits and avoid fatty foods that alter the metabolism.'

Youngsters need to get exercise, but doing exercise in a polluted environment can mean that the bad effects outweigh the good. 'Keep an eye on pollutant levels and don't do high levels of outdoor activity on high pollution days,' he says.

There is hope in the air for the future, as government regulations in Hong Kong and across the border have led to a reduction in the level of airborne pollutants in the city.

Last year the average annual concentration of sulphur dioxide and respirable suspended particulates (the nasty stuff) in the region decreased by 19 per cent and 11 per cent respectively as compared to the levels in 2007.

A report by the Hong Kong government attributed these reductions to the implementation of enhanced emission reduction measures (for example the completion and installation of desulphurization systems at thermal power plants) and strengthening controls on vehicle source emissions.