Sulfur Dioxide vs Formaldehyde (free): which is worse?
Quick answer: Formaldehyde (free) carries the heavier risk profile. Sulfur Dioxide is — in the EU and — in the US; Formaldehyde (free) is banned in the EU and allowed in the US.
| Property | Sulfur Dioxide | Formaldehyde (free) |
|---|---|---|
| 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 | additive | cmr |
| Where it hides | — | nail hardener, keratin treatment, eyelash glue |
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.
What is Formaldehyde (free)?
Formaldehyde (free) is free formaldehyde used directly as a preservative and in salon hair treatments.
Documented risks
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.
Formaldehyde (free): A known human carcinogen (IARC Group 1). Banned from direct use in EU cosmetics; allowed in US products with limited oversight.
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