If you’re interested in know what the air quality looks like in Beijing China, the US Embassy there has a particulate matter monitor on its roof that tweets the level of fine particulate matter (PM2.5) every hour (see @BeijingAir). In case you’re not used to staring at PM2.5 values all the time, let me provide some context.
The US National Ambient Air Quality Standard for the 24-hour average PM2.5 level is 35 mcg/m^3. The twitter feed shows hourly values, so you can’t compare it directly to the US NAAQS (you’d have to take the average of 24 values), but the levels are nevertheless pretty high.
For example, here’s the hourly time series plot of one 24-hour period in March of 2010:
The red and blue lines show the average and maximum 24-hour value for Wake County, NC for the period 2000-2006 (I made this plot when I was giving a talk in Raleigh).
So, things could be worse here in the US, but remember that there’s no real evidence of a threshold for PM2.5, so even levels here are potentially harmful. But if you’re traveling to China anytime soon, might want to bring a respirator.