Long-distance runner's sad lot: a bad air day

A marathon run in thick smog highlights in ironic relief the plague of air pollution that is choking Chinese cities.

I've always admired sports enthusiasts for their perseverance, but my envy stopped on Oct 19 when tens of thousands of them took to the streets for the annual Beijing marathon.

It was a smoggy day. The level of PM2.5, particulate matter with a diameter of 2.5 micrometer or less, reached an extremely hazardous level of 344 at 8 am when the race started. That was not the worst in recent weeks, with some days so choked with dirty air you could hardly see the buildings across the street, but the Sunday on which the marathon was run was obviously unsuitable for strenuous outdoor activity.