THE NORTH of China choked on a deadly fog this week. The good news is that China’s government has a new plan to address the country’s air pollution, and increasing unease among the nation’s new middle class is placing some pressure on the regime to make good on its commitments. Yet orchestrating a quick and significant reduction in air pollution would challenge any government, and China’s has a mixed record of enforcing environmental standards.

At stake is the health and livelihood of hundreds of millions of people. Toxic air pollution got so bad this week in the metropolis of Harbin, which boasts a population of more than 10 million, that buses were getting lost in the dull haze, cars were using their fog lights and airports were closed. The government is considering heavy restrictions on travel and industrial activity. Even when the pollution isn’t so spectacularly bad, air purifiers have become a must-have home appliance and a common subject of small talk among those who can afford them.

A recent study in the Proceedings of the National Academy of Sciences noted that, between 1981 and 2001, particulate pollution in China was five times worse than what the United States experienced before Congress passed the 1970 Clean Air Act, and that was before China’s rapid economic expansion over the past dozen years. The analysis concluded that dirty air shortens people’s lives by an average of 5.5 years in polluted northern China compared with the cleaner south.

Part of the issue is that pockets of high pressure around northern China prevented the air from clearing. But the real problem is large-scale coal burning. The country has abundant amounts of the sooty fuel, and it is responsible for about half of the world’s annual coal consumption. Apart from spewing massive amounts of climate-change-inducing greenhouse emissions, burning coal releases particulate matter into the air, from which it enters people’s lungs and bloodstreams.

The poor planning and corruption of an unaccountable political leadership, insulated from public pressure and common sense, in large part created this choking industrial hell; they have encouraged coal-fired power generation and coal burning in homes for years, flouting environmental concerns. But last month the regime announced that it would attempt to limit coal use to 65 percent of energy consumption by 2017. Last year coal produced 67 percent of the country’s energy. The government also unveiled reduction targets for various types of particulate matter and restrictions on auto pollution.

Authorities are right to focus on reducing coal consumption, which will have to drop much more in the long term. But doing that well will be a challenge. The government’s plan to power Beijing with synthetic natural gas, derived from coal, could reduce ambient air pollution, but it would also produce a lot more carbon dioxide emissions and gobble up fresh water in areas of the country that can hardly spare it, a World Resources Institute analysis found. And the whole program requires that state authorities enforce it. China already has pollution standards that often haven’t been respected. This time around, will local officials stick to official policy when it might curtail economic growth or limit the opportunity for corruption?

The well-being of northern China depends on the answer.