Hmmm... I'm glad my commute is away from dense traffic for 90%... and then most traffic is petrol not diesel. On the rare occasion that there are fumes I tend to breathe slower due to the suffocating stink.
The other factor not considered is cyclists are slower than traffic (except buses) so would perhaps cycle in pockets of reduced pollution, while motorists in heavy traffic would be in it all the time, so may end up worse??
I think tests like these are worthless for predicting actual effects in real traffic conditions unless they take air samples along the route at cycling speeds.