References :

The exposure of cyclists, car drivers and pedestrians to traffic-related air polltants.
Van Wijnen JH, Verhoeff AP, Jans HWA, Van Bruggen M
Int Arch Occup Environ Health (1995) 67 : 187-193


Differences in cyclists and car drivers exposure to air pollution from traffic in the city of
Copenhagen. Rank J, Folke J Jespersen PH
The Science of the Environment (2002) 279: 131-136

Hi,
I have just called the Velib service to check this info ; it's important to me as the owner of a short-term rental business in Paris (most of our clients are tourists).
The Velib hotline informs me that you MUST have a card with a chip on it (like all French cards) and that most tourists therefore cannot use the system. There is no way of getting short (week-long) subscriptions online.
That said, they assure me that they are working on a system...
Cheers,
Alex Wagner

Yes, this old post turned out to be incorrect. It is not a good idea to dig up ANYTHING from 3 years ago on a forum.

However, MOST tourists can use the system, because most tourists are French and European.