Congratulations on quitting, both cigarettes and E-cigs.

Almost anything is better than smoking.
Nicotine is a VERY powerful stimulant. It is very rough on many of the bodies systems, especially hard on the Cardio-Vascular. So no, e-cigs are NOT safe...

Interestingly, a new study showed that working out in itself had a mild preventative anti-cancerous effect. I believe study was referenced in The First 20 Minutes: Surprising Science Reveals How We Can Exercise Better, Train Smarter, Live Longer
The First 20 Minutes: Surprising Science Reveals How We Can Exercise Better, Train Smarter, Live Longer: Gretchen Reynolds: 9780142196755: Amazon.com: Books

Something about deep breathing stimulating healing mechanisms...