Policymakers are beginning to address an asphyxiating problem

AFTER the sun sets, Seoulites can glance at the illuminated N Seoul Tower atop one of the peaks surrounding the city to check the quality of the air they are inhaling. The tower has a palette of four colours: if blue or green, go for that jog. But if it glows yellow or red, beware not only of high levels of coarse soot, but also unhealthy concentrations of fine dust that can cause grave damage to the lungs.

South Korea began publishing nationwide readings on PM2.5, as the dust is known, only last year. It stood at 27 micrograms per cubic metre on average—half the level in nearby China, but over two-and-a-half times higher than the World Health Organisation’s recommended limit, and well above the levels in other rich Asian countries. Seoul is far sootier than Tokyo (see chart). And these readings may be optimistic: an adviser says the government regularly discards high readings as “anomalies”. South Korea ranks 173rd out of 180 countries in an index of air quality from Yale University (China came in next-to-last). Its problems with pollution are likely to grow: the OECD, a group mostly of rich countries, projects that on the current trajectory the number of premature deaths each year due to dirty air will triple by 2060 to 1,100 for every million inhabitants.