Lead
One of the basic elements (Pb), lead is a soft metal that has been used in plumbing systems for thousands of years. The word "plumbing" derives from the Latin word for lead, plumbum. Lead has a unique ability to resist pinhole leaks, while being soft enough to form into shapes that deliver water most efficiently. Its softness and malleability were for a long time highly desirable properties for manufacturing everything from pipe to paint. Lead is a neurotoxin that can accumulate in the body in soft tissues, as well as bone.