Formaldehyde (free) vs Sulfur Dioxide: which is worse?
Quick answer: Formaldehyde (free) carries the heavier risk profile. Formaldehyde (free) is banned in the EU and allowed in the US; Sulfur Dioxide is — in the EU and — in the US.
| Property | Formaldehyde (free) | Sulfur Dioxide |
|---|---|---|
| EU status | Banned | — |
| US status | Allowed | — |
| Risk level | high | — |
| Banned in | European Union | — |
| Restricted in | — | European Union (ADI 0.7 mg/kg body weight; mandatory 'contains sulfites' labeling in wine and food), United States (banned from fresh produce 1986; mandatory labeling above 10 ppm) |
| Category | cmr | additive |
| Where it hides | nail hardener, keratin treatment, eyelash glue | — |
What is Formaldehyde (free)?
Formaldehyde (free) is free formaldehyde used directly as a preservative and in salon hair treatments.
What is Sulfur Dioxide?
Sulfur dioxide (SO2) is a colorless gas used as a food preservative and antioxidant. It is the primary active form of the sulfite family of food additives. It is generated by burning sulfur or as a byproduct of certain chemical processes. In food use, it is released from various sulfite salts (E221-E228) and directly applied to some foods.
Documented risks
Formaldehyde (free): A known human carcinogen (IARC Group 1). Banned from direct use in EU cosmetics; allowed in US products with limited oversight.
Sulfur Dioxide: Same as sodium sulfite: sulfite-sensitive individuals (1% of population, 5% of asthmatics) can experience severe reactions. SO2 in wine has been identified as a contributor to wine-induced headache and asthmatic episodes. Occupational exposure to SO2 gas causes respiratory irritation, bronchospasm, and lung damage at higher concentrations — relevant to workers in winemaking and food processing but not typical dietary exposure levels.
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