The City has been working hard to remove lead from the infrastructure, it may still be picked up from lead service pipes that connect your home to the water mains. Strict regulations are in place to control the amount of lead which occurs in potable water, and while massive investments have helped to reduce the levels of lead significantly, some pipework may still be problematic.
City of Toronto is responsible for the pipe that runs from the boundary of your property to the water main, but you are responsible for the section that runs from the boundary to your property.
Internal lead plumbing fittings may also be responsible for seeping this metal into your home.