Not a lot of direct experience, but I was there for a few days in 1980
during the siege, and people said they could not fish or garden due to
toxic pollution from the aluminum plant a mile upriver. People were eating
wild game, which they felt at least had a chance to wander out of the area
and which therefore might not be as poisoned. (The muskrat tasted pretty
good, too.)
You might talk to John Mohawk or Akwesasne Notes staff.
Chris