“PM2.5” seems an odd and wonky term for the blogosphere to take up, but that is precisely what has happened in China in recent weeks. It refers to the smallest solid particles in the atmosphere—those less than 2.5 microns across. Such dust can get deep into people’s lungs; far deeper than that rated as PM10. Yet until recently China’s authorities have revealed measurements only for PM10. When people realised this, an online revolt broke out.

One of Japan's crippled nuclear reactors still has fatally high radiation levels and much less water to cool it than officials estimated, according to an internal examination that renews doubts about the plant's stability.