Vapes on black market may contain toxic chemicals, pesticides, harmful flavorings Chemicals in e cigarettes mix together to form new, unexpectedly toxic compounds EurekAlert! Harmful Chemicals in Vapes and E Liquids You Should Avoid SMOKO E Cigarettes Vape juice contains a long list of chemicals, many of which aren't even listed on the packaging. Testing has also shown that vapes labelled "nicotine free" can have high nicotine levels. Do you know what you're vaping? Propylene glycol (PG) and vegetable glycerin (VG) are the main liquids in vapes. When heated, these chemicals turn toxic and aren't safe to breathe.