Ontario’s air quality has been steadily improving since the turn of the century with less pollution — and some help from Mother Nature — cutting down the number of smog days, a report has found. The report, released Friday, found that three major pollutants — nitrogen dioxide, carbon monoxide and sulphur dioxide — were down between 40 and 64 per cent over nine years.

“Whether it’s hot years or cool years, we’re seeing the right trend,” said Environment Minister John Wilkinson, adding that 2009 brought just three smog advisories over five days.

That’s the lowest in the 39-year history of the report prepared by his ministry — but it should be noted that the summer of 2009 was cool and rainy.

Those conditions make it difficult for smog to form because rainfall cleans the air and a lack of heat means polluting chemicals are not being cooked into smog.

“We didn’t have a lot of hot days that summer so the weather also plays a part,” said Jack Gibbons of the Ontario Clean Air Alliance, a pollution watchdog group.

But he credited the improvement in overall air quality to the Liberal government’s phase-out of heavily polluting coal-fired electricity generating stations and federal regulations requiring cleaner diesel fuel and gasoline for cars and trucks.

The New Democrats said the Liberal government, which is heading into an election Oct. 6, should be careful about boasting too much on the low number of smog days in 2009 given the recession’s devastating impact on manufacturing.

“Almost every factory, especially the high electricity-consuming factories in this province, were shut down,” said MPP Peter Kormos (Welland). “It’s nothing to be proud about.”

Official statistics are not yet out for 2010 but even though last summer was hot, Ontario had just 12 smog advisories as of Sept. 1 — well below the 39 advisories in 2007 and a whopping 53 in 2005.

About half of Ontario’s smog blows in from the United States.

The province is planning to phase out coal-fired power plants by 2014. It closed four coal units last year with two more slated to be closed at the Nanticoke generating station next fall.

Coal use was up last summer, however, because the hot and dry weather reduced water levels at hydroelectric plants, making it harder to generate electricity.