Pollution worldwide is the biggest trigger of heart attacks and other health problems, more than alcohol, anger or even drug use, so CTV set out to find the region's biggest polluters.

Surprisingly, the answer isn't easy to find, as polluters in Canada face very little public scrutiny.

But as Ontario faces more and more summer ‘smog days,' concern is growing. Over a four-year period smog days led to 2,000 hospitalizations and more than 600 deaths in Waterloo Region.

Toyota's sprawling plant on Maple Grove Road in Cambridge, which covers more than three million square feet and employs 5,000 people, produces three different Toyota and Lexus vehicles.

It also produces the most pollution in the region.

Records obtained by CTV show the Toyota plant released more than 800 tonnes of pollutants in 2009, and most of them were volatile organic compounds (VOCs).

While Toyota declined an on camera interview, a report provided by the company shows a 65 per cent drop in VOC emissions at the company's North American plants since 1998.

Dr. Anthony Miller works at the University of Toronto's Dalla Lana School of Public Health.

He says "It is a good idea to reduce pollution, because it does affect the lungs and there is some evidence it increases the risk of lung cancer."

The Safety-Kleen oil re-refinery comes in second on the list of polluters. The Breslau company takes used engine oil, cleans it, and then sells the product again.

In 2009 they contributed 583 tonnes of pollution to the atmosphere, mostly in the form of sulfur dioxide and nitrogen oxide, the leading cause of acid rain.

Dale MacIntyre, vice president of Canadian operations for Safety-Kleen calls the company "a well-kept secret."

He says "If the used oil doesn't end up here, going through our re-refining process, it ends up being burned as low-grade industrial fuel…Our studies have shown that by re-refining the oil back into a lubricant, we avoid about 300,000 metric tonnes per year of greenhouse gas emissions."

And it's those emissions that are the basis for the CTV ranking, which uses data collected by Environment Canada as part of the National Pollutant Release Inventory.

Third on the list is the Toromont Energy Waterloo Power Plant, which sits on the grounds of the regional landfill on Erbsville Road in Waterloo. It gathers methane from the dump and burns it for energy, creating 310 tonnes of pollution.

The top ten polluters in Waterloo Region also include:

 Company Pollutants released in 2009 (tonnes)
1. Toyota Cambridge  803
2. Safety-Kleen  583
3. Toromont Energy  310
4. Gerdau Ameristeel  277
5. Canadian General Tower  222
6. Barrday  153
7. Weston Bakeries  128
8. Chemtura  117
9. Babcock & Wilcox  108
10. Plasti-Fab  103

Source: Environment Canada

Kitchener-Waterloo Green Party candidate Cathy MacLellan says "Often I think reporting fails to express the urgency of it. I mean we're in a crisis mode here. We're like the frog in the water, and the water's warming, the frog has no idea."

The companies ranked third, fourth and fifth did not return calls from CTV for comment.

Coming up in part two: How do emissions in Waterloo Region compare to other areas, and are they getting better or worse?