Safety of Sodium Bisulfite as a Food Additive

Sodium bisulfite (E 222) is a sulfite-class food additive authorized for use in the European Union. Its chemical formula is NaHSO₃, with a molecular weight of 104.06 g/mol, a CAS number of 7631-90-5, and an EINECS number of 231-548-0. It appears either as a clear, colorless-to-yellow solution or as a white-to-off-white crystalline powder. It is highly soluble in water (3000 g/L at 20°C) and sparingly soluble in ethanol. It is unstable in air; upon exposure, it gradually loses some sulfur dioxide and oxidizes into sulfates[1].

Functions of Food Additive E 222

Sodium bisulfite serves as a preservative, antioxidant, and color stabilizer in food protection. It is widely used in products such as wine, dried fruits, shrimp, pickled vegetables, soft drinks, and fruit products to prevent browning and microbial growth. It exerts its preservative, antioxidant, and color-stabilizing effects by releasing sulfur dioxide. Regulatory bodies, such as the FDA, restrict the use of sulfites (including sodium bisulfite) on fresh fruits and vegetables intended to be consumed raw.

Safety of Sodium Bisulfite

Studies indicate that sodium bisulfite has low oral toxicity as a food additive; the LD₅₀ in rats is approximately 1.16–1.54 g/kg body weight (bw), with primary symptoms including cyanosis and sedation. It shows no genotoxicity or reproductive and developmental toxicity. Although some *in vitro* studies indicated sister chromatid exchange (SCE) and gene mutations, results from more reliable studies were negative. While *in vitro* studies showed that high concentrations (>1 mM) of sodium bisulfite might impair neuronal axonal transport, expert panels consider the relevance of this finding to human exposure levels to be unclear. Long-term toxicity studies in rats established a No-Observed-Adverse-Effect Level (NOAEL) of 70 mg SO₂ equivalents/kg bw/day.

Expert panels have currently set the Acceptable Daily Intake (ADI) for sodium bisulfite at 0.7 mg SO₂ equivalents/kg bw/day. However, this is noted as a temporary ADI, subject to re-evaluation once the database is further refined. For individuals sensitive to sulfites, it may trigger severe allergic reactions, including anaphylactic shock or asthma attacks.

References

[1] ON FOOD ADDITIVES E P, ADDED TO FOOD (ANS) N S. Scientific Opinion on the re-evaluation of sulfur dioxide (E 220), sodium sulfite (E 221), sodium bisulfite (E 222), sodium metabisulfite (E 223), potassium metabisulfite (E 224), calcium sulfite (E 226), calcium bisulfite (E 227) and potassium bisulfite (E 228) as food additives[C]//14 4. 2016. DOI:10.2903/j.efsa.2016.4438.