If e-cigarettes are such bad depends on some factors.
- E-liquid type/vendor
- E-cigarette configuration
There have been some studies that e-cigarettes are not so harmless. And other studies that say the opposite. Some studies had questionable experiment configurations. Many doctors say that e-cigarettes are (over 90%) less harmful as normal cigarettes.
But there was a recent study that newer, higher watt powered e-cigarette generations produce more harmful formaldehyde
https://www.ncbi.nlm...les/PMC5377270/
Formaldehyde–hemiacetal was detected in the aerosols generated from some e-liquids using the newer e-cigarette devices at a battery power output of 11.7 W and above. The emission of these aldehydes from all e-cigarettes, especially higher levels of aldehydes from the newer-generation e-cigarette devices, indicates the risk of using e-cigarettes.
So i would say, if you use e-cigarettes, keep in below 11 watt and choose a good quality e-liquid that doesn't include harmful substances.