Sulfur Dioxide vs Propylene Glycol: which is worse?
Quick answer: Sulfur Dioxide carries the heavier risk profile. Sulfur Dioxide is — in the EU and — in the US; Propylene Glycol is — in the EU and — in the US.
| Property | Sulfur Dioxide | Propylene Glycol |
|---|---|---|
| EU status | — | — |
| US status | — | — |
| Risk level | — | — |
| Banned in | — | — |
| 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) | European Union (not permitted as a direct food additive in most food applications; only permitted as a carrier solvent for specific additives at low levels) |
| Category | additive | additive |
| Where it hides | — | — |
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 Propylene Glycol?
Propylene glycol is a synthetic organic compound used as a humectant, solvent, and emulsifier in food, pharmaceuticals, cosmetics, and industrial applications. It is produced from propylene oxide (derived from petroleum). Its chemical formula is C3H8O2.
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.
Propylene Glycol: Propylene glycol is generally considered safe by the FDA and is metabolized by the liver to lactic acid and pyruvate (normal metabolites). However, at high doses — particularly from intravenous pharmaceutical formulations — propylene glycol can accumulate and cause lactic acidosis, kidney toxicity, and CNS effects. These effects are seen in critically ill patients receiving high-dose PG-containing intravenous medications, not from food consumption. In children and people with impaired liver or kidney function, PG accumulation may occur at lower doses than in healthy adults. Animal studies have found reproductive and developmental effects at high doses. EFSA's 2018 re-evaluation found no concerns at typical food use levels but noted the EU limits PG use as a direct food additive, using it only as a carrier solvent for permitted additives.
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