Toronto has four treatment plants devoted to making water safe for people to drink; the one on the Islands is the smallest, but not much smaller than two of the others. They all draw their water from long intake pipes that extends past the bulk of the pollution from Toronto, a city which still sends sewage directly into its rivers and harbour.
Perhaps this plastic bottle of antifreeze that had merely floated across this quiet lagoon from the far side; perhaps it came from farther away. All I know is that I carried it more than a kilometre before I found a recycling bin to put it in. And of course there's no guarantee that it won't still manage to find its way back into our water again.