Environmental Risk Assessment/Environmental Hazard Assessment: Similarities and Differences

Risk assessment and hazard assessment are alternate paradigms for assessing the effects of chemicals and other hazards on the environment. Risk assessment is an old assessment tradition that grew out of actuarial statistics and is concerned with estimating the probability of undesired events. Hazard assessment was developed in the late 1970s as a means of performing assessments by iteratively (1) testing and measuring the properties of chemicals, (2) comparing toxicity test endpoints to estimated environmental concentrations, and then (3) deciding whether the chemical is clearly safe, clearly hazardous, or requires more testing. These two paradigms have much in common in that they attempt to apply environmental toxicology, environmental chemistry, and scientifically based logic to the regulation of chemicals. In this respect, they differ from the regulation of hazards by absolute prohibitions, political negotiations, adversarial proceedings, and technology-based standards. They differ in the following ways: (1) risk assessment, unlike hazard assessment, is explicitly probabilistic; (2) hazard assessment assumes that clear distinctions can be made between safe and unsafe, but risk assessments determine degrees of safety; (3) risk assessment explicitly allows for value judgements, but hazard assessment implies that decisions about acceptability are scientific; (4) risks, unlike hazards, are balanced against costs and benefits; (5) risk assessments have explicit endpoints, (6) hazard assessments model environmental concentrations, but risk assessments model exposure, (7) hazard assessment requires tiered testing, but risk assessments can be performed with available data; (8) procedural decisions in hazard assessments are based on the assessor's judgement, but risk assessments use formal decision criteria; and (9) risk assessment makes greater use of mathematical and statistical models.