Axiom is  a general purpose Computer Algebra system. It is useful for research and development of mathematical algorithms. It defines a strongly typed, mathematically correct type hierarchy. It has a programming language and a built-in compiler.
Polybutylene is simply a type of plumbing material that was manufactured between the late 70's and early 90's. It is thought that it was installed in over 6 million homes during that time period.
Lead (Pb) is a heavy metal that occurs in low levels in all soils. Natural concentrations of lead in. most soils range from 10 to 30 parts per million (ppm). (Lead concentration is commonly expressed. on a mass basis: a level of 1 part per million [ppm] corresponds to 1 milligram [mg] of lead in.