Haze and more Spring Festival firework celebrations pushed Shanghai air pollution levels to new highs early on Thursday, despite “good” air being recorded throughout most of the previous day. The level of PM2.5 – air particles small enough to directly enter the lungs – fluctuated between 70 and 100 micrograms per cubic metre on Wednesday but rose to 651 at 1am the next morning, according to the Shanghai US Consulate’s air quality monitor – a level beyond register on the index which only goes up to 500. Pollution levels subsided to a "moderate" level of 90 at 10am. The World Health Organisation recommends average 24-hour exposures of less than 25 micrograms per cubic metre. Following the eve of Spring Festival fireworks on Sunday, the city’s PM2.5 levels doubled to 523 after the celebratory firecrackers deluged the city in particles and dust.