'How bad' is hard to argue as it varies from day to day. But regularly in recent times it's been in the news for having awful levels, especially concerning to the athletes and spectators in the 2008 Olympics.
In summer it can be worse as the hot sun aggravates the situation. Others like you with similar concerns have asked the same questions and found some scary responses.
When it comes down to it, the best you can do in smoggy conditions is to stay indoors (most common advice), wear a mask if you really are worried (one that handles the smallest particles - ask your doctor for where to get one), and bring your medicine, just in case.
If you must go outside (sounds like you're not), do it in the early morning when things aren't as bad.
There are several sites with suggestions on how to handle it, but hopefully indoors with air-conditioning and filters you should be partially shielded from the pollutants.
But when health is concerned, above all a doctor is the best to ask. They've been educated / research about these very situations, and will have the best advice to give.