This is fairly simple The key is nothing burns when you vape so none of the deadly cancer causing carcinogens are inhaled. That’s not mentioning the thousands of chemicals in traditional cigarettes that are not present in vape.
Vape e-liquid has four pharma grade ingredients.
PG Propylene Glycol – found in asthma inhalers
VG Vegetable Glycerin – The mixture in cough mixture is sweet but no flavour
Nicotine – In the same class as caffeine as a stimulant
Food Flavours – Often taken from the sweet/confection industry