Finding any of these substances may lead you to not go through with purchasing a particular property. Or, you may continue to go through with the deal and perform a clean up at the expense of the seller. Lenders require these assessments be done but if you are about to purchase a property with cash, you should invest in an environmental assessment, have a look at http://www.argyllenvironmental.co.uk/contaminated-land-consultants for further information.
The first state is called Phase 1. This is where an environmental assessment company will perform a visual inspection. The second phase is Phase II. This may or may not be needed depending on the results of the historic inspection in Phase I.