Ottawa is set to proclaim a dramatic decline in key pollutants like heavy metals and sulphur as it seeks to burnish its environmental record in the face of criticism at home and in the United States.

In a report to be released on Friday, Environment Canada says emissions of mercury and lead were down 23 per cent and 21 per cent respectively in 2011 from the previous year, while sulphur oxides were 7 per cent lower and nitrogen oxide was down 6 per cent. The 2011 report does not cover carbon dioxide and other greenhouse gases, which Ottawa has committed to reduce by 17 per cent from 2005 levels by 2020.

U.S. Ambassador David Jacobson said this week that greater Canadian progress on reducing greenhouse-gas emissions would help sway American views on Alberta oil as the Obama administration reviews the proposed Keystone pipeline, which would bring a daily supply of 830,000 barrels of oil-sands bitumen to the refining hub on the Gulf Coast. U.S. environmentalists are converging on Washington this weekend to demand that President Barack Obama reject the Keystone project, declaring the decision to be a key indication of his commitment to address climate change.

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A week ago, the federal environmental commissioner warned that Canada's environmental policies are not keeping pace with resource development. Natural Resources Minister Joe Oliver has acknowledged that more must be done, particularly on oil-tanker safety off the British Columbia coast, and ensuring that energy companies face proper liability for their projects.

But the government is keen to proclaim some good news, and Friday's pollution report is an opportunity. The 2011 declines follow two decades of improvement. According to last year's inventory, Canadian emissions of sulphur oxide – a key component of acid rain – declined by 57 per cent between 1990 and 2010, while nitrogen oxide emissions decreased 18 per cent. Dioxins were down by 90 per cent, and lead and mercury decreased 83 per cent and 87 per cent respectively.

In contrast, Canada's greenhouse-gas emissions have soared since 1990, although they fell in recent years as the recession drove down industrial activity and Ontario closed coal-fired power plants.

In the House of Commons Thursday, Environment Minister Peter Kent defended Canada's record on climate change, insisting the country is on track to meet its commitment to reduce greenhouse gases by 17 per cent from 2005 levels by 2020 – the same target Mr. Obama adopted.

NDP environment critic Megan Leslie accused the Conservative government of "hurting our most important trading relationship" through failure to move more aggressively on climate change, especially regulations for the oil industry.

Mr. Kent said Ottawa will soon release its long-promised draft regulations covering the oil sands as part of its "sector-by-sector approach" that is slowly rolling out emissions regulations.

"We first treated and addressed the emissions from the transportation sector, the largest emitting sector in Canada," Mr. Kent told the House. "We then generated regulations for the coal-fired electricity sector. We are now well into, and very close to finalizing, regulations for the oil-and-gas sector. . . We have a plan. It is working."

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However, earlier in the week, Mr. Kent told The Globe and Mail that he was leery about releasing the draft regulations while the Obama administration is reviewing the Keystone pipeline proposal.

"I don't think it's necessary, and if it was done merely as leverage, it might be seen as inappropriate," he said.