1.   Because of heavy government subsidies, the vehicles are cheaper to buy and run and produce fewer pollutants.

2.   Their supporters say they supply an environmentally clean and safe power source, producing no pollutants.

3.   Those pollutants are produced by coal-fired electric plants and automobiles.

4.   He said they sometimes involve converting coal to a gas or mixing it with limestone to produce less pollutants.

5.   While diesel fuel used in buses and trucks gets good mileage, it produces more pollutants than gasoline, the Nikkei said.