Complex sentence: When the Air Pollution (Marketing, Sale and Distribution of Fuel) Regulations were enacted in 1990, this banned the sale of bituminous fuels in the Greater Dublin area as such this lead to an immediate reduction in smoke levels thus offering the potential for better health.
Split into simpler sentences: When the Air Pollution (Marketing, Sale and Distribution of Fuel) Regulations were enacted in 1990, this banned the sale of bituminous fuels in the Greater Dublin area. This led to an immediate reduction in smoke levels, thus offering the potential for better health.