A choice not very difficult to make

Beijing has been blessed with blue skies for most of the days the past few weeks.

Smoggy days have been the exception, rather than the rule, and one hopes it stays that way only with the scale tilting in favor of sky blue. The red alerts issued against hazardous smog by the Beijing authorities seem like a distant nightmare.

Almost nobody is talking about PM2.5 and PM10 or face masks. Particulate matter with a diameter smaller than 10 or 2.5 micrometers that can be inhaled and cause respiratory problems seem things of the past. And talk of installing air purifiers in schools and offices to clean the toxic air indoors has all but passed into distant memory.