Groups of doctors and environmentalists are calling on the Ontario government to stop exporting power generated by the province's coal-fired plants.

Jack Gibbons, of the Ontario Clean Air Coalition, said Ontario exported 20 per cent of its power in 2006 and made a profit of $100 million.

Speaking at a news conference in Toronto on Monday, he said that cash isn't worth the toll coal-fired plants are taking on people's health.

Franz Hartmann, of the Toronto Environmental Alliance, said the province could reduce its coal production without affecting how long Ontarians could keep their lights on and run their air conditioners.

It can't happen fast enough for Hilary de Veber, a Toronto pediatrician who regularly sees children with breathing difficulties.

"Smog kills," said de Veber, a spokeswoman for the Canadian Association of Physicians for the Environment.

"When it is not killing people, it is reducing the health of all Ontarians through its many adverse health effects."

But Steve Erwin, a spokesman for Energy Minister Dwight Duncan, said the sources are mixed for the power that Ontario exports. Very little of it likely comes from coal, he said, because that power generation is only used on days when demand is at its peak.

He said if Ontario reduced the amount of power it exports, it would just mean the United States would step up production at their coal plants sending more dirty air across the border.

Premier Dalton McGuinty and his Liberals have drafted a regulation that would see the province's four coal-fired plants close by 2014. Erwin said that phaseout is going on now.