Charles Perrow, Professor Emeritus of Sociology of Yale University, wrote “Normal Accidents: Living with High Risk Technologies.” He defines normal accidents as “the interaction of multiple failures that are not in a direct operational sequence” (p. 23). A good example is Three Mile Island. A failure in one component that was not detectable by control room operators led to a misinterpretation of the reason for loss of coolant that was reported by instruments in the control room. The operators’ response led to a partial meltdown of the reactive core and a release of radioactivity (equivalent to a chest x-ray) and flurry of anti-nuclear activity. Fortunately, from a public health perspective, the Three Mile Island accident was inconsequential. However, not all normal accidents will be. In discussing the Deepwater Horizon accident, Rutgers University Professor Lee Clarke provides this perspective:
Consider the idea that the disaster was a “low probability/high consequence” event. From the outside looking in, BP’s accident qualifies. The “high consequence” part is obvious. It was “low probability” because big blowouts are rare, so the event caught us all by surprise.
From the “inside,” though, it’s possible the disaster probabilities didn’t matter much. Perhaps there were good reasons to think the risk was worth taking. Maybe it was an “acceptable risk,” as we call it. If so, a large, uncontrollable blowout was just a matter of time.
How many of us in agriculture work with acceptable risks on a daily basis? (I hope the answer is obvious.) Retrofitting old tractors with roll-over protection systems is a tangible way to avoid certain risks that were previously “acceptable”. Yet, when it comes to biosecurity risks in agricultural production, we might do well to change our threshold for acceptable risk. We move livestock to remote pasture, into barns, to fairs, to sale, and to slaughter without giving much thought to the biosecurity of the conveyances or venues and the potential risks involved. If a pig infected with a highly contagious disease like foot-and-mouth disease were in a show barn adjacent to a cattle barn at a show out-of-state and animals returned home before visible signs were detected, we would soon find out what a high consequence normal accident is like.