Sodium Tetraborate (Borax)
Also known as: E285, borax, sodium borate, sodium tetraborate, disodium tetraborate
Borax/sodium tetraborate (E285) is banned for direct food use in the United States. The EU permits E285 only for sturgeon eggs (caviar) up to 4 g boric acid/kg as a tolerated derogation; EFSA's 2013 re-evaluation reduced the tolerable upper intake to ~10 mg boron/day for adults due to reproductive and developmental toxicity in animals.
What it is
Sodium tetraborate (borax, Na2B4O7), an inorganic boron salt. Used historically as a food preservative and antiseptic.
Preservative (historic); pH buffer; primarily industrial use today.
Why it's flagged
- Sodium borate / boron is restricted as a food preservative but used as a trace boron supplement (≤3 mg/day) in some multivitamins under DSHEA — different regulatory category.
- reproductive and developmental toxicity in animal studies
- nephrotoxicity at high doses
- illegal as food preservative in US and most of EU
What regulators actually say
"Scientific Opinion on the re-evaluation of boric acid (E 284) and sodium tetraborate (borax) (E 285) as food additives."
"Food Additive Status List ... entries marked PROHIBITED include boric acid as not permitted in foods."
Regulatory status
United States — FDA
Not permitted as a food additive in the US; FDA 'Poisonous Plants and Substances' considers borax illegal in foods
European Union — EFSA
EFSA established TWI for boron at 10 mg/day (2013); E285 only authorized for caviar at 4 g/kg in EU
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