The recent Volkswagen (VW) diesel car scandal ("Volkswagen accused of dodging emission rules"; Sept 20) is a wake-up call for the authorities to review how clean diesel engines really are.
Diesel car manufacturers claim that their cars emit less carbon dioxide. However, it is the nitrogen oxide (NOx) emission that is cause for concern and a main contributor to filthy air.
Tough anti-pollution standards are crucial for cleaning up our air.
It has been shown that filthy air is a major health hazard and related to many premature deaths.
As the VW scandal has shown, there can be a wide discrepancy between NOx emissions from a manufacturer's certification and the actual NOx emissions in real-world situations.
The authorities should not accept the manufacturers' claims without conducting their own tests.
It is time to tighten regulations on emissions and ensure that there are effective measures to rid our roads of polluting vehicles.
Phang Fook Ghay