I was wondering what the base case for the public health report was? I'm not a health expert so I was hoping that someone could inform me of their report assumptions.
What alternative assumption did they use for long-term growth in travel modes? There will be growth in travel to these destinations so did they consider the impact to Toronto from increased traffic, diesel trains, secondary impacts due to wind currents from Pearson, etc. I know they are focused on Toronto and I was wondering if they considered all the impact to Toronto (let's ignore impacts to other cities for now). I agree that the direct pollution including noise pollution is less impactful on a lower density airport near Pearson but I wonder if they considered that almost every person that was going to fly out of the Island is now going to be driving or will be on a train going through the same neighbourhood. And I think there is more density around the tracks/Lakeshore/Gardiner/427 vs beside the Island.
A lot of that is beyond the scope of the project and for good reason, it is not that significant given how localised a lot of the environmental impacts of these developments are (dose makes the poison, and in this case it's all about proximity). Also, induced demand is a thing for airplanes just as it is for other modes of transportation, so the cheaper and more accessible you make flying the more people will opt to do so. You cannot make the assumption that the same number of people will fly either way.
In any case... in the medium term GO rail and the Pearson Rail Link should be electrified, which means that the amount of emissions released into the neighbourhood from people travelling to the airport by rail will be minimal. People who were going to walk or take transit to the island airport will be within walking distance of an electric rail connection to Pearson, so no extra cars on that equation.
People from the rest of the city heading to Pearson in cars will be heading to an airport in a very low-density area mostly through other low-density areas rather than through Toronto's most populated neighbourhoods.
Overall the impacts of transporting people from downtown to other airports would be very small, and can be improved and be made sustainable and less polluting much more easily than it would be to try and make the island airport operations more sustainable and compatible with its surroundings.
Now, if you look at the levels of pollution arising from highways in Toronto, especially in Etobicoke, you'll see it is absolutely disastrous. That is why a less centralised electrified rail system and improved public transportation network is essential for this city's future health (if we want to keep building residential areas next to our highways, that is). Expanding the island airport would do next to nothing to ameliorate the impacts of our highway network, instead making matters worse in what is already one of the densest and most polluted areas in the city. Ironically, the greatest support for maintaining the status quo and/or expanding highways comes from the suburban neighbourhoods that are hit the hardest with their pollution.
In many ways Pearson itself is a lost battle because of the sheer amount of cargo that goes through that airport (one of the reasons why it's a huge employment centre). Busy airports and highway systems simply require large buffer zones around them unless we want to deal with huge amounts of negative externalities. Pearson actually has a huge buffer and it works quite well, contrary to what the false equivalences posited by many posters here ("look there's a house there!!!11!") would indicate.
All the areas in orange or red do not meet minimum air quality standards:
When you look at maps showing population and employment density such as this (which may have been made by a fellow UTer?):
You see that the area around Pearson and some of the large highway interchanges (where pollution levels are highest) have been rightly kept as some of the lowest density areas in the region, which is consistent with the most basic notions of risk management.
Expanding an airport next to the most populous part of the city is the opposite of what any risk management expert would suggest (as evidenced by the fact that all experts on the subject are against the expansion).
