The smog-prone Tianjin Municipality recorded its best air quality after five years of fighting air pollution, local authorities said Wednesday.
Tianjin, which neighbors Beijing, enjoyed 209 "good air" days last year, 64 more than in 2013, while the number of heavy pollution days decreased from 49 in 2013 to 23.
The city's PM2.5 level in 2017 was 62 micrograms per cubic meter, the lowest in five years.
PM2.5 is a measure of the density of hazardous particulate in the air. The World Health Organization recommends an annual PM2.5 level of 10 micrograms per cubic meter.
Tianjin also recorded improvements in the density of other major pollutants such as PM10, sulfur dioxide and nitrogen dioxide, with sulfur dioxide down 72.9 percent compared with 2013.
In 2013, the city started implementing pollution control measures such as demolition of coal-fired boilers.