Multicontaminant air pollution in Chinese cities

OBJECTIVE: To investigate multicontaminant air pollution in Chinese cities, to quantify the urban population affected and to explore the relationship between air pollution and urban population size. METHODS: ). Concentrations were considered as high, if they exceeded World Health Organization (WHO) guideline limits. FINDINGS: occurred on over 146 days in 145 cities, mainly in east China. Surprisingly, multicontaminant air pollution was less frequent in cities with populations over 10 million than in smaller cities. CONCLUSION: Multicontaminant air pollution was common in Chinese cities. A shift from single-contaminant to multicontaminant evaluations of the health effects of air pollution is needed. China should implement protective measures during future urbanization.