Why Chinese pollution is such a tough problem

Alex is back, alive and well.  But he still has a raspy voice from sucking in all that air pollution.  Here is one reason why, as explained by Brad Plumer:

China's central government is well aware that its blackened rivers and sunless skies are a problem, not just because they're sparking riots and social unrest, but because out-of-control environmental degradation is imperiling the country's economic growth. Lately, Beijing has issued a slew of bold--at least on paper--environmental regulations. But the laws are doing little good because the central government can barely enforce them in its own provinces. This structural problem will remain the key to China's environmental dilemma, and, as countries attempt to push Beijing toward a cleaner future, they'll discover that the capital is the least of their troubles.

The central government has passed some fairly "green" laws but often to little avail:

Beijing is aware of this local lawlessness, but has had little success handling it. "China used to send in swat teams from the central government," says Barbara Finamore, who directs the Natural Resources Defense Council's (NRDC) China program. "I've seen these campaigns going on for twenty years-- they'll come in, shut down some factories, and, when they leave, they'll open up again."