The amount of industrial pollution produced locally in Waterloo Region is falling gradually, and there are number of factors contributing to the decrease.

The closure of the former Budd/Kitchener Frame automotive parts plant on Homer Watson Boulevard meant a loss of jobs, but also environmental relief.

The plant used to be the region's third largest polluter, pumping out 356 tonnes of airborne pollutants, as recently as 2008.

Now new companies, with smaller environmental footprints, are changing the makeup of Waterloo Region.

But there are some who say we shouldn't get too excited.

Kitchener-Waterloo Green Party Candidate Cathy MacLellan says it's important to remember that the atmosphere has no borders.

"So somebody else is making that, what was made in that building is being made somewhere else," she says. "We may comfort ourselves in thinking, oh, we no longer have certain polluting industries here -- so it's not our problem. Well it's still a problem."

And that's a problem impacting cities across Canada, especially in places like Alberta, where oil and gas drives the economy.

It's a problem within Ontario too. For example, the Imperial Oil refinery in Sarnia released 22,464 tonnes of airborne pollutants in 2009. The numbers for the Dofasco steel mill in Hamilton are similar.

The province's coal-fired Nanticoke Generating Station near the shore of Lake Erie emitted 32,338 tonnes in 2009.

But the biggest polluter is Vale Inco's copper smelter in Sudbury, putting out 43,379 tonnes of pollution.

By comparison, the biggest polluter in Waterloo Region, Cambridge's Toyota plant, put out emissions that are less than two per cent of that figure.

It's important to note that the numbers are subject to a lot of variables.

Gerdau Ameristeel was fourth on CTV's list of the biggest polluters, but its emissions for 2009 were down significantly due to a labour dispute that idled the plant for months.

In a filing submitted to Environment Canada the company wrote, "The Reheat furnace was operated by management personnel on a reduced basis for the last half of the year. This has resulted in reduced emissions."

Meanwhile at the Safety-Kleen oil re-refinery in Breslau, capacity is on the rise, but net emissions are being reduced, even after a $26-million expansion was announced in October.

Dale MacIntyre, vice president of Canadian operations for Safety-Kleen says, "Our expansion is about a 25 per cent increase in capacity, but we expect our emissions to go up less than 25 per cent because of the energy efficiencies that we're building into it."

Environmentalists say new technology, and the motivation to use it, is the key to bring emissions numbers down, but those numbers need to be continually made public in order for public pressure to come into play.