Heavy Metals from Coils
E-cigarette heating coils are typically made of nickel, chromium, and iron. When heated — especially in the presence of acidic e-liquids — these metals can be released as aerosolized particles. A 2024 study published in Nicotine and Tobacco Research found dramatic differences based on e-liquid pH:
| Metal | At pH 4 (acidic) | At pH 8 (alkaline) | Safety Threshold Exceeded? |
|---|---|---|---|
| Nickel (Ni) | 2,649 ppb | 28 ppb | Below threshold at both pH levels |
| Chromium (Cr) | 20 ppb | 3 ppb | Exceeded inhalation PDE at pH 4 |
| Lead (Pb) | 176 ppb | Non-detectable | Below threshold, but concerning at pH 4 |
A 2025 UC Davis study published in ACS Central Science found that some disposable e-cigarettes released toxic metal levels exceeding health-risk thresholds for cancer, neurological damage, and respiratory diseases. The highest daily lead emissions from one device were equivalent to smoking nearly 20 traditional cigarettes. The study also identified the illicit use of leaded bronze in non-heating device components in contact with e-liquid as a source of lead contamination.
Vitamin E Acetate and EVALI
Vitamin E acetate is not a recognized ingredient in legal, FDA-authorized nicotine e-liquids. It was identified as the key contaminant in the 2019 EVALI (e-cigarette or vaping product use-associated lung injury) outbreak. The CDC found that THC-containing e-cigarette or vaping products associated with EVALI often contained vitamin E acetate, which was used as a thickening agent in illicit THC cartridges. The CDC's 2019 MMWR report found that illicit THC-containing products submitted by 11 of 12 EVALI patients in Minnesota contained vitamin E acetate. The EVALI crisis was linked to contaminated, illicit THC vaping products — not to legal nicotine products sold through regulated channels.
Cross-Contamination Risks
Beyond vitamin E acetate, manufacturing contamination can occur through shared equipment, poorly controlled supply chains, and low-quality ingredients. The sucralose degradation issue (producing chloropropanols) is technically a cross-contamination of the heating process rather than the manufacturing process, but it illustrates how ingredients that are individually safe can produce dangerous byproducts when combined and heated.
