The rebuilding and development of Kathmandu's infrastructure after last year's earthquake in Nepal offer a unique opportunity to improve the city's air quality. According to one ranking, Kathmandu is currently Asia's most polluted city (see go.nature.com/csbt1c).

Kathmandu's air pollution is increasing uncontrollably owing to a lack of environmental legislation in the face of haphazard expansion. The number of vehicles has tripled over the past ten years, and toxic particulates are now “far above” World Health Organization guidelines (A. Gurung and M. L. Bell J. Expo. Sci. Environ. Epidemiol. 22, 235–242; 2012). Unregulated industrial activity, dust from the congested road system and open burning of solid waste all add to the pollution. Moreover, Kathmandu lies in a valley, the topography of which causes temperature inversions that trap this polluted air — making it barely breathable on occasions.

I urge the government to extend its clean-up and restoration beyond buildings, temples and monuments and to draw up stringent environmental regulations. The valley's 3 million inhabitants matter, as well as its tourists.