Water pollution monitoring. Scientist collects a sample of water from a discharge pipe, in this case during research into mercury contamination. Mercury is a toxic metal which forms water-soluble salts. If mercury is consumed over a period of time it can cause irreversible damage to the brain, liver, and kidney. This pipe was found to be discharging up to 1.09 milligrams of mercury per litre of water; these levels are up to 1 million times higher than those found in unpolluted water. Photograph of Dr David Santillo, a Greenpeace researcher, at a pipe from the Chemplast Sanmar PVC complex at Mettur Dam in Tamil Nadu, India.