Air quality in Beijing improved in 2015 despite several “red alert” warnings issued by the government for dangerous smog conditions, officials said Monday.

The Beijing Environmental Protection Bureau reported that the concentration of particulate matter—a mixture of pollutants that harm human health—in the city declined by more than 6% between 2014 and 2015, according to a China Daily report. Air quality exceeded the national standard more than half the year and the improvement exceeded their target of reducing pollution by 5%, officials said.

The news comes as China continues to face internal pressure to reduce smog and make cities more livable. The concentration of particulate matter still remains at more than eight times the level deemed acceptable for human health by the World Health Organization. Recent research has shown that smog in China contributes to more than 1.5 million premature deaths each year.

A warning system launched in the city two years ago takes cars off the road and mandates the closing of factories to stem the most dangerous smog conditions. Changing weather patterns may have also contributed to last year’s improvement.

Read More: China Shows It’s Getting Serious About Climate Change

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Write to Justin Worland at justin.worland@time.com.