China is imposing stricter regulations to control air quality for the first time in 14 years, with benefits for human health and for climate change.

Stricter rules will “motivate cities in China to continue their clean air action,” Ma Jun, founder of Beijing-based non-profit Institute of Public and Environmental Affairs, told Bloomberg News. “If we want to achieve this new standard it will be very difficult.”

New limits on concentrations for a range of air pollutants will begin phasing in this month. They are to be strengthened until 2031, when the new standards will be fully in force as of Jan. 1. The final rules will require that average annual concentrations of PM2.5—airborne particulates measuring 2.5 micrometres or less, measured as micrograms per cubic metre (µg/m³)—are limited to 25 µg in most locations, compared to the current limit of 35 µg.

Particulates this small can be inhaled deep into peoples’ lungs and enter the bloodstream. The new standards beginning in March will set an average limit at 30 µg, Bloomberg reports.

China’s last round of air quality regulations was launched in 2013 to address public outcry following several years of noxious winter smog events. The 2013 rules helped the country achieve the world’s fastest improvements in air quality, Bloomberg writes, with annual average PM2.5 concentration falling from 68 to 28 µg/m³ from 2013 to 2025.

However, even the new rules fall short of guidance issued by the World Health Organization in 2021, to limit annual air pollution to an average PM2.5 limit of 5 µg, with a 24-hour limit of 15 µg. Roughly 60% of Chinese cities’ air pollution levels currently exceed the planned new 25-µg standard, Bloomberg says.

China’s Ministry of Ecology and Environment has announced that although the new standards are aimed at improving peoples’ health, they also support the country’s decarbonization efforts, China Daily reports.

The air pollution regulations are separate from the country’s decarbonization targets, which measure emission as carbon dioxide equivalent. In 2018, veteran environmental journalist Paul Brown reported reported for the Climate News Network that China’s air quality was improving, and regulations had achieved a 20% reduction in air particulates in the three years prior. That “was also good for climate change,” Brown wrote, “because the same policies mean less fossil fuel is being burned and fewer greenhouse gases released.”