This statement is false. It is often not possible for speciation to be predicated as speciation of species depends on its habitat and interaction with other organisms in the habitat as well as the ever-changing environmental factors. It is thus very hard to model possible speciation that could happen.
The toxic still ended up to the affected people because of bioaccumulation. This means that organisms who might have consumed the said mercury was consumed by some larger organisms. These larger organisms were eaten or consumed by human beings. The toxin, in other words, was just passed on to different species.