On the mainstream issue of cancer prevention, Samuel Epstein has published three books, The Politics of Cancer, The Politics of Cancer Revisited and the Cancer-Gate: How to Win the Losing Cancer War. There are three other areas where Epstein discusses policy and its relation to legislation: the Precautionary Principle; Pollution Prevention and Toxics Use Reduction (TUR); and references to Canada. Many formulations of the Precautionary Principle, for example, the one in the Rio Declaration 1992, stress that action on the environment should not be contingent on full scientific certainty. With the virtual abandonment of substitution, REACH now looks much more like a notification system dealing with disclosure of information rather than an authorization system, placing restrictions on the introduction of chemicals into the market. Substitution at the chemical user level is also one of the long-standing techniques of TUR, though Epstein considers it a recent addition to the Mass.