Naturally occurring radon gas hotspots in Toronto

Where, in Toronto, would one be at most risk of coming into contact with radon gas?

I know it's basically everywhere - but my bio teacher mentioned that the Don mills/Lawrence area has an especially high concentration.

There is no way of knowing if a environment has a high radon level without testing. Also it is a hit or miss thing. I have seen personally where a home can test extremely high and the neighbors test pretty low. Sure some spots will typically be higher then others. but you have to test to know for sure. Further more you are in contact with radon more often you think, unless you work in a skyscraper above the first few floors. If you are in a home or building that touches dirt in North America chances are that you are being exposed to radon. You are even exposed to Radon outside. I know in the U.S. the average indoor Radon concentration is 1.3pCi/L and outside is 0.4pCi/L-0.6pCi/L I Know your measuring system is different in Canada but the action level is still about the same when you convert them to the same unit for measure. In the US our recommended action level is 4pCi/L and Canada is 11 or 12, but the unit of measurement is different but equal about the same. I know this to be true because I am the best damn Radon Mitigator on planet earth and licensed to kill Radon and test!!!! :) I have personally fixed a home that measured 204.0pCi/L. If you do test I recommend a continuous radon monitor testing unit (CRM). Usually you have to hire a pro to get this done. Testing units are very expensive!! Another thing you could invest in would be a Safety Siren(google it). Its a CRM specifically for worried homeowners. They are $129.99 US dollars. Hope this helps. EVERYONE SHOULD TEST THERE HOME!!! DONT LISTEN TO DUMB A**ES THAT SAY ITS NO BIG DEAL, I TALK TO PEOPLE ALL THE TIME THAT HAVE HAD LOVED ONES LOST TO RADON (INCLUDING THERE PETS). DON'T LET PEOPLES IGNORANCE KILL A FAMILY MEMBER OF YOURS!!!!