Sir: Yesterday, I was travelling on the Park Road in Islamabad when I saw a bus that was emitting thick black smoke. I tried to overtake the bus but could not succeed. Ultimately, I decided to stop my bike and let the bus go to avoid the smoke pollution. The existing laws against smoky vehicles, which were formulated in the 60s, propose a maximum fine of Rs 200 on drivers of such vehicles. This amount is insufficient and worthless. It is the need of the hour that our legislatures should enact new laws to control this menace of polluting vehicles. About 15 years ago, New Delhi was a highly polluted city. The Indian government decided to ply CNG buses in this city instead of those being run on diesel. These CNG buses have made a lot of difference and the level of air pollution has significantly dropped. I propose that our government should impose a ban on diesel buses altogether not only in Rawalpindi/Islamabad but all over the country. If we can replace our metro diesel buses with CNG buses, it will be happy news. By taking these measures, we can help keep our country free of air pollution. Clean air without carbon soot, lead and particulate matter will reduce the risk of blood cancer and cardiovascular diseases among citizens. MUHAMMAD ASHTAR Islamabad