The South Korean capital, Seoul, is among the world’s most polluted cities, so it’s no surprise that air pollution was one of the key campaign issues for the newly elected president, Moon Jae-in.

That’s why, on his fifth day in power, Moon has announced that the country will temporarily shutter 10 coal power plants now and will shut them down completely within his five-year term. The move should bring respite from the choking air pollution, but it raises questions about South Korea’s energy security.

By 2060, air pollution may kill as many as 9 million people worldwide each year, according to an OECD report, and South Korea is expected to suffer the most deaths among the world’s richer countries. Koreans commonly complain that coal-crazy China was to blame for its pollution problem, as the smog drifted over the Yellow Sea. But its own coal power plants are partly too blame, too.

Nuclear power’s contribution to South Korea’s mix has fallen from 40% to 30% over the last 10 years, as plants have been decommissioned over safety issues. To make up for the fall, the contribution of coal has shot up to 40% (paywall). The country operates 53 coal-power plants, and plans to build another 20 in the next five years.

Coal is the dirtiest fossil fuel. New coal power plants are likely to be more efficient and produce less particulate pollution than old ones. But if South Korea wants a more robust solution to its air pollution problem, it will have to look to increase the contribution of low-carbon sources such as solar and wind from a paltry 8% of its energy mix. Currently, the country ranks the lowest for renewable energy use among the 35 members of the OECD, a club of mostly rich countries.