It is important that all of the issues influencing the perception of risk, as well as the technical assessment itself, are properly understood by all risk assessors so that the communication of risks can be effectively achieved.
People with different social, economic and cultural backgrounds living in different places will perceive risks in different ways which reflect their own particular knowledge and their environment. When risk assessment is carried out by an expert it may be (or may be seen to be) biased or motivated by their own values/selfinterest. The general public's understanding of the technical issues associated with contamination is often poor or incomplete, which often leads to the 'expert' then having a low opinion of the validity of public concerns. These factors can then combine to drive the public to distrust the technical arguments being presented and to oppose the plans for development.
The influence of the media in the public perception of risk is also strong, with the amount and type of coverage given to an issue influencing judgements about risk. Objectors to particular projects can also use potential hazards associated with contaminated land and their associated risks in order to oppose development.
Such groups of people often have a vested interest, summarised as 'not in my backyard'.
Well publicised examples of developments undertaken on contaminated sites without appropriate remedial design exacerbates the public's perception of high risks associated with such projects. Retro-fitting of remedial or control measures into new buildings is both difficult and costly in comparison to installing appropriate measures during development, and also introduces additional problems such as disruption to people's lives and homes, stigma and blight.
Public trust in both the makers of policy, and officers of companies/regulatory bodies is thus very important in the communication of risk. It is also important to understand that it is much easier to lose someone's trust than to build it. Once trust is lost it is very difficult to regain. The competence and credibility of the person putting the argument across is often dependent on their track record which in turn determines the level of trust they receive.