The impact on the city’s air quality of people lighting fireworks in the city on Lunar New Year’s Eve and Sunday — the fourth night of the holiday, when people welcome the God of Fortune — was significantly lower than in previous years.

The air quality index (AQI) in Shanghai was above 100 all day Sunday due to pollutants blown into the city from northern China, the environmental monitoring center said.

It rose to a peak of 213 at 5pm, before falling to 113 at 11pm.

Over the following two hours, as people lit their fireworks and firecrackers, the index rose to 165, while the density of PM2.5 pollutants rose to about 120 micrograms per cubic meter from 80 earlier in the day.

Overnight, however, the air quality improved, and by 6am yesterday morning, the AQI stood at 62.

On Chinese New Year’s Eve, the AQI was 90 at 1am, while the PM2.5 density was 67 micrograms per cubic meter, up from 27 at 4pm the previous day. It dropped under 35 micrograms after 3am.

This year was the first since 2012, when the city government began publicizing figures, that the PM2.5 density was under 100 at midnight on New Year’s Eve. The improvement was most likely due to tighter controls on the sale of fireworks.

The number of licensed vendors was cut to 700 this year, while a cap of 150,000 boxes was placed on the number of fireworks that could be sold.

Out of environmental and safety concerns, the Shanghai government has in recent years introduced increasingly strict regulations on the sale of fireworks.

On Lunar New Year’s Day in 2013, the PM2.5 density soared to 523.7 micrograms per cubic meter at 2am, from just 81.4 at 8pm the previous evening. On the fourth night of the holiday, the measure rose to 279.7 shortly after midnight, from 85.8 earlier.

The city’s fire control bureau last year reduced the number of licensed fireworks stores to 1,314 from 1,600 the year before, and cut the number of boxes available for sale by about 30 percent to 300,000.

The PM2.5 density in the early hours of last year’s Lunar New Year peaked at 290 micrograms per cubic meter about 1am, while on the fourth night of the holiday the figure was 62.