Well, at least that's the conclusion I make from looking at the sepa.gov official website here which monitors (certain) pollutant levels. Last Sunday a new scheme for car reduction was introduced pre-games which allows cars to go on the roads only on odd or even days, depending on the number plates. Since then, although the traffic has noticeably decreased, the pollution levels have been steadily rising. I created the following from the data on the above linked site (apologies for the mistake in the figure, API index should simply say API).
1 = API 0-50 = excellent (old) => good (new)
2 = API 51-100 = good => moderate
3A = API 101-150 = slightly polluted => unhealthy for sensitive groups
3B = API 151-200 = light polluted => unhealthy
4A = API 201-250 = moderate polluted => very unhealthy
4B = API 251-300 = moderate-heavy polluted => hazardous
And given that I've seen the levels get to 500 on very very bad days, 100 doesn't look too chokingly horrible, though I understand that it is outside the guidelines set by the Olympic committee. With less than two weeks to go, I'm not sure what more they can do...