Carbon monoxide emissions in Malta dropped between 2001 and 2004 but increased again in subsequent years, the National Statistics Office said.

Statistics it issued to commemorate World Environment Day, being celebrated tomorrow, show that the drop may indicate a consumer preference for diesel over petrol.

Carbon monoxide emissions were linked to the combustion of petrol rather than diesel, since around 70 percent of the current vehicle stock consisted of petrol engine cars.

Diesel combustion emissions produced sulphur dioxide. These emissions were more related to the burning of fossil fuel oil at the power stations for the generation of electricity.

The NSO said that there was an upward trend in fuel oil consumption in the 17-year period under review. Use of coal for electricity generation ceased completely in 1995, to be replaced by the use of residual

fuel oil. Sulphur emissions decreased sharply in 2003, when low-sulphur fuel oil replaced the higher-sulphur content fossil fuel.

Sulphur emissions had fluctuated considerably since 1990 but the sulphur content of the residual fuel oil burnt at the power stations started to decline in 1998 reflecting the different levels of sulphur content in the various fuel oils used.