Unfortunately for you, so far there have been few (or none) proven health risks for bystanders, stemming from e-cigarettes. So you are closer to the argument of "can a coworker eat a smelly sandwich in my vicinity?" than to "is my coworker allowed to smoke next to me?".
Regardless I would approach the problem with the following steps:
- Talk with your coworkers.
Depending on your relationship with them, they may take notice of your concern. This can be tough especially if it turns into the case of "you v. the rest of the office". However, depending on your diplomatic skills and rapport with said coworkers this approach has a lot of benefits. In the worst case, things stay as they are and you might be persceived as "whining".
There are a million and one ways to approach this so I will not even try, but I'd spend most of my time doing this or just putting up with the vaping.
- Talk with your Managment.
Get somebody's support from higher up, could help you enforce a no vaping policy. Here the risk of fallout with your coworkers rises, but chances of success may be higher. This also depends on your "diplomatic prowess" and rapport.
Be advised the chance of alienating your coworkers increases here. It is best to use a combination approach, openly communicating with your coworkers that you are taking these steps. I personally would probably skip this step.
- Get a new Job
If the issue is so important to you, and attempts at bringing change to your worksplace have failed, its time to look for a different place. Remember since the health risks are probably minimal, I personally would try to bring about gradual change to the workplace culture using my jedi mind tricks and talking with my coworkers.
EDIT: There are other opinions which suggest even going to government to institute change through this. This would be appropriate if you feel that vaping is something that should be handled by law. In the case of smoking this has brought about drastic change. I would not suggest this. Even though one can't opt-in to inhaling other peoples vape; for me the risk is just too low to warrant this.