I am wondering if 30 ml/day is still safer than smoking... I suppose it is but it's a lot...
IMO, vaping ANY number of mL/day of eliquid...is
still definitely safer than smoking! Eliquids consist of VG, PG, flavorings, and many times...some nicotine. As of right now, I'm not aware of
any studies that have shown that chemicals in those ingredients have been found to be carcinogens or otherwise harmful.
However, there are literally
thousands of chemicals that exist in/are produced when tobacco in a cigarette is burned. Some of those chemicals
have been identified as carcinogens and/or the contributors to other types of harm to the human body.
If you haven't already read about it, you may want to read what the Royal College of Physicians found in their study on smoking versus vaping. There is also at least 1 on-going study being done on vaping here in the US, by Moffitt Cancer Center in Tampa, FL (a nationally recognized, high quality, institution). The possibility of vaping being classified as a legitimate NRT (ie. Nicorette, nasal spray, the patches, etc.) is a potential outcome of the study. I know this for a fact, because I'm a member of one of the study groups for it.
ETA: Forgot to respond to your OP.
I smoked 1-1.5 PAD for 42+ years, before quitting in Jan. 2014. Since then, I've been vaping 8-10mL/day of 60VG/40PG eliquids at 6-7mg nic. Doing that has so far resulted in: (1) Test results indicating that my previously diagnosed mild COPD is no longer evident any more, (2) My blood oxygen level has drastically improved, (3) My breathing has greatly improved, as my lungs now sound perfectly clear when checked by my doctor.