Use of Boric Acid and Borax in Food
Boric acid (H
3) and borax (Na
2O) are both boron-containing compounds which are widely used in a wide range of consumer products such as glass and fire retardants. They have also been used in food preparations to give food a better texture and prolong its shelf life.
Food surveillance findings in the past have revealed that boric acid had been added to food including rice dumplings and root starch jelly as a preservative.
Safety of Boric Acid and Borax
- At low concentrations, borax can be converted to boric acid in body prior to absorption.
- Boric acid can produce toxic symptoms including vomiting, diarrhoea and abdominal pain in humans upon excessive intake. Animal studies indicate that ingestion of large amount of boric acid may cause adverse reproductive and developmental effects. Testicular lesions and sterility have been observed in experimental animals. For developmental toxicities, decreased fetal body weight as well as malformations of the eyes, the central nervous system, the cardiovascular system and the skeleton have been observed in animal studies. However, there is no evidence that boric acid is genotoxic (toxic to genes) or cancer causing.
- The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has evaluated the safety of boric acid and borax. It was concluded that these compounds considered not suitable for use as food additive.
- Boric acid and borax are not permitted preservatives under the Preservatives in Food Regulation of the Public Health and Municipal Services Ordinance, Cap.132.
- The sale of food containing boric acid or borax as a preservative is in contravention of Section 3 of the Preservatives in Food Regulation, Cap.132BD. The maximum penalty for contravening this Regulation is $50,000 and imprisonment for 6 months.
Advice to the Public
- Obtain food supplies from reliable sources.
- Maintain a balanced diet.
Advice to the Trade
- Do not use boric acid or borax in food.
Risk Assessment Section
Centre for Food Safety