Risk factors and risk level assessment: Forty thousand emergencies over the past decade in China

During a public emergency, which possibly evolves into a major public crisis, it is critical to quickly identify the main risk factors and assess the levels of risk, in order to efficiently manage the risks. In this study, about 40 000 emergencies in China over the past decade are investigated. Then, the five different types of risk factors are identified of these emergencies using the 5W1H methodology, including risk time (When), risk location (Where), risk population (Who), risk psychology (Why) and risk element (What), which lead to a risk matrix that is suitable for China's national conditions. Based on this risk matrix, combined with expert knowledge, the Borda count and the analytic hierarchy process analysis, risk levels can be precisely assessed, solving 'how to provide a solution' (How), which provides decision-making guidance and facilitates prompt risk responses.