The water flowing through the Niagara River over the falls is filtered before it is drinkable due to Lake Erie having contaminates leaked and drained into, from factories on the American side of the lake.

The water at Niagara Falls is generally considered clean in terms of ecological health, but it is not "pristine" or safe for direct consumption without treatment. The water originates from the upper Great Lakes, which have seen significant improvements in water quality over the last several decades due to strict environmental regulations like the Great Lakes Water Quality Agreement. However, the water still carries sediments, natural organic matter, and traces of urban runoff. The famous "foam" often seen at the bottom of the falls is not usually pollution; it is a natural byproduct of dissolved organic matter (like decaying plants) being vigorously agitated by the sheer force of the 167-foot drop, similar to how a blender creates foam. While the Niagara River supports a healthy fish population and is safe for recreational boating, it can contain "legacy pollutants" from the region's industrial past that have settled in the riverbed. For visitors in 2026, the water is perfectly safe to be sprayed by during a boat tour, but for drinking, the local municipal systems use advanced filtration and UV treatment to ensure it meets health standards.