Safety Assessment versus Risk Assessment
Depending on the health effect, an environmental health risk assessment can be a safety assessment or a risk assessment. When the health effect is one that does not cause cancer but something like heart disease or asthma, then EHRA essentially defaults to a safety assessment. In that form of assessment, EHRA exercise results in characterising a level of risk and a level of maximum allowable exposure so that no additional disease over and above a certain baseline results. The assessor accepts a certain level of exposure. On the other hand, when the health effect is one of cancer, then no theoretical upper limit of accepted level of exposure is possible, as cancer is a multi-step disease. At some point during the development of cancer, a molecular mechanism triggers the cancerous process and as this happens at molecular levels, therefore a theoretical low acceptable limit is impossible to define. Therefore in cancer, we usually do not define a threshold level but instead we define a level of exposure where certain amount of excess cancer cases accrue.
Steps of EHRA
EHRA consist of four steps: hazard identification, dose response assessment, exposure assessment and risk characterisation (Figure 1) Figure 1. EHRA four step process