The evolution of organisms that methylate toxins in our environment is problematic. When raw sewage and metal toxins are both present in the environment, microorganisms that normally would nourish us develop ways of getting rid of the metal and other toxins. One way is the methylate them, making them more volatile so that they out-gas into the atmosphere. However, when these organisms then reinfect our alimentary tracts, they start out-gassing these hard to remove, fat-soluble toxins into our fat.
The best way of preventing these types of disasters is to not put toxins and raw sewage into our waste systems and environment. Everyone can play a part in this every day by simply not purchasing the more toxic products and packaging, and not polluting.