NSW recorded almost triple the number of days with poor air quality resulting from "exceptional events" last year compared with 2017, with authorities blaming dust storms and bushfires.

The Annual Air Quality Statement showed there were 51 such days in 2018, up from 18 a year earlier. The drought contributed to 25 days with air quality affected by dust storms - versus three in 2017 - while wildfires and hazard-reduction burning caused notable pollution on 26 days, up from four in 2017.

Almost one in every seven days last year saw air quality quality fall below national standards in parts of Sydney. Credit:Brook Mitchell

There were also 36 days with hazardous air quality. In Sydney, such days were mostly linked to smoke from prescribed burning, particularly between April and August, the government report said.

Overall, the state's air quality was "generally good" during 2018, with levels of nitrogen dioxide, sulfur dioxide and carbon monoxide "easily" meeting national standards.