With respect to air pollution, mass demonstrations protesting unhealthful conditions were held in cities such as Yerevan in the Armenian SSR. Official reports confirmed that more than 100 of the largest Soviet cities registered air quality indexes ten times worse than permissible levels. In one of the most publicized cases, the inhabitants of Kirishi, a city not far from Leningrad, succeeded in closing a chemical plant whose toxic emissions were found to be harming—and in some cases killing—the city's residents. Finally, separate, highly publicized cases of man-made disasters, the most prominent of which was the Chernobyl' nuclear power plant accident in 1986, highlighted the fragility of the main production -nature relationship in the Soviet Union and forced a reconsideration of traditional attitudes and policies toward industrialization and development.