That diesel cars are somehow more environmentally friendly than petrol cars is a myth that keeps popping up in the public debate ("Review road tax for greener diesel cars" by Mr Chua Cheng Seek; Monday).

Petrol is bad, but diesel is worse. Diesel cars produce excessive levels of mono-nitrogen oxide gases such as nitrogen dioxide, as well as small particulate matter.

Even statements from manufacturers, that carbon dioxide levels are lower in diesel cars, are now being questioned, given that real-world driving conditions are different from laboratory testing.

Diesel engines are especially unsuitable for low-speed driving and idling, such as city driving.

While they are clean when new, they wear out quickly and become even more polluting when older.

The French capital Paris is planning to ban all diesel cars from the city permanently by 2020, and London might follow suit.

The perfect stop-and-go city car has already been invented, it is the small, petrol-electric hybrid car, and all city residents should buy one if they need a car at all.

This should be based on public consumer demand, and ideally, should not involve government intervention at all.

We can blame Indonesia for the haze blanketing the region, but we also contribute to air pollution.

Our tropical rains keep the air clear most of the time, but on a few days this month, when PSI readings were in the three-digit range, I could not help but notice how much car, van and truck exhaust fumes contributed to the haze.

According to the World Health Organisation, air pollution kills seven million people worldwide every year.

In Singapore, we can do our bit by starting to tax diesel fuel the way we tax petrol (currently 56 cents a litre for intermediate grade). It would be a small but significant step towards a better, cleaner city for all.

Morten Strange