Concepts of Probabilistic Risk Analysis and Applicability for "Day-to-Day" Laser Safety Evaluations

In recent years, more and more emphasis was placed on considering probabilistic risk analysis (PRA) to be performed by the user as basis for deciding on appropriate user control measures. The concept of PRA in terms of probability for exposure to a certain level of exposure for a certain exposure duration, probability that that exposure level leads to an injury of the eye or the skin and finally the severity of the injury is reviewed. The authors discourage attempts to adopt this concept for day-to-day laser safety evaluations in respect to quantifying the probability than an injury occurs as a function of how much the exposure level is above the MPE and to characterize the corresponding severity of an injury. For anything but very sophisticated treatments of high profile issues, any ocular exposure above the MPE should be considered as severe enough to prompt control measures, unless the probability for the exposure to occur as such is negligible. It is argued that rather than suggesting the user to perform involved quantitative risk analysis, the concepts of PRA lend themselves as tools for standards committees and their development of guidelines for controls measures. Some level of risk analysis should still be performed by the user in order to adopt the "default" control measures (as defined by standards committees) to the specifics of the laser applications under consideration. However, this user performed risk analysis can be greatly simplified and in most cases quantitative approaches are not only unnecessarily involved but might also be inappropriate.