The aim of the study is to assess the strength of the world stock exchanges reaction to the SARS-CoV-2 coronavirus pandemic at the turn of 2019-2020. The risk and intensity of the decline in the values of the basic stock indices were analysed. The spreading pandemic within a few months covered all continents and had a signi cant impact on the socioeconomic situation of all countries. The study used methods of duration analysis. The time of the 20% drop in stock market indices was studied. This is a value that is taken as a sign of crisis. Kaplan-Meier's estimator was used to assess the probability of indices' value decrease. The risk of decline was determined by means of a logit model and the intensity of the decline was determined by means of an empirical hazard estimator and a Cox proportional hazard model. The intensity and risk of decline of stock indices varied from continent to continent. The intensity was highest in the fourth and eighth week after the peak and was highest on European exchanges and then American and Asian exchanges (including Australia). The risk of falling stock indices was highest in America, followed by Europe, Asia and Australia, and lowest in Africa. Half of the analysed indices recorded a 20-percent drop in value after 52 days (median duration). The study is a prelude to further analyses related to the crisis and the normalisation of the situation on world stock exchanges. It allows to learn about the impact of the pandemic on the economic situation and to detect differences between the continents. The methods from the survival analysis are used in the study to assess the impact of the pandemic on the intensity and risk of decline in stock exchange indices.

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Significance We illustrate the similarity and difference in particulate matter (PM) formation between Beijing and other world regions. The periodic cycle of PM events in Beijing is regulated by meteorological conditions. While the particle chemical compositions in Beijing are similar to those commonly measured worldwide, efficient nucleation and growth over an extended period in Beijing are distinctive from the aerosol formation typically observed in other global areas. Gaseous emissions of volatile organic compounds and nitrogen oxides from urban transportation and sulfur dioxide from regional industry are responsible for large secondary PM formation, while primary emissions and regional transport of PM are insignificant. Reductions in emissions of the aerosol precursor gases from transportation and industry are essential to mediate severe haze pollution in China.