HOW RISKS ARE IDENTIFIED AND ASSESSED

Risk analysis can usefully be applied to potential health and safety r isks from technology and pollution. We examine historical examples of how knowledge about risk is developed, discussing the capabilities as well as the limitations of analyses to identify potential risks, estab lish causes, and estimate the probability that harmful effects will oc cur. One speaks of ''risk'' because, in any particular instance, an ad verse outcome may or may not occur; causative factors skew the probabi lities of different outcomes. Accordingly, the detection and measureme nt of risk must be derived from samples of instances. Real-world obser vations of risk may be supplemented with controlled experiments, and r isks of interest must often be estimated indirectly through extrapolat ion from analogous circumstances. The ensuing uncertainty affects the clarity of ranking risks against one another and limits the usefulness of risk analysis alone as a means of resolving social conflicts about risk.