Thor Hushovd dropped the Olympics altogether. He hasn't said so explicitly, but I imagine the pollution was a factor. He was battling a chest cold towards the end of the TdF, and though he won a race in Norway just two days before the Olympic team left for Beijing, and had said beforehand that he considered that race a test of whether he was recovered enough to go, he nevertheless decided not to go "because he has to give priority to his health".