Formaldehyde in Food


  1. There have been occasional reports on the abuse of formaldehyde as bleaching agents and preservatives in food in the Mainland.
  2. Both the Mainland and HKSAR have legislative control on the use of permitted preservatives in food. Formaldehyde is not permitted for food use in either place.

Risk Assessment and Public Health Significance

  1. Formaldehyde is a chemical used mainly for the production of plastic materials as well as applied in cosmetics, fungicides, textiles and embalming fluids. It is a colourless gas at room temperature, readily soluble in water with a strong irritating smell.
  2. Formaldehyde is sometimes added inappropriately in food processing for its preservative and bleaching effects. The common incriminated food items are dried bean curd, vermicelli and hydrated food such as tripe, chicken paws, etc.
  3. However, this chemical also occurs naturally in the environment. As a metabolic intermediate, formaldehyde is present at low levels in most living organisms. It can be therefore found naturally in small amounts in a wide range of raw foods, including fruits and vegetables, meat, fish, crustacean, dairy products, etc. High levels of formaldehyde up to 300ppm to 400ppm are found naturally in dried mushrooms including shiitake.
  4. The World Health Organization (WHO) has established a Tolerable Daily Intake (TDI) of 0.15mg/kg body weight for this chemical. The TDI is the estimated amount of a substance that can be ingested daily (on body weight basis) over a lifetime without appreciable risk.
  5. Ingestion of a small amount of formaldehyde is unlikely to cause any acute effect. Acute toxicity after ingestion of large amount can cause severe abdominal pain, vomiting, coma, renal injury and possible death.
  6. The International Agency for Research on Cancer (IARC) has classified formaldehyde as carcinogenic to humans, based mainly on epidemiological evidence from occupational exposures in industrial workers. On the other hand, WHO in 2005 when setting its Drinking Water Guidelines considered that the weight of evidence indicates that formaldehyde is not carcinogenic upon ingestion.

Control Measures and Surveillance Findings

  1. Food for sale in the HKSAR must be fit for consumption as stipulated in the Public Health and Municipal Services Ordinance, Cap. 132. The use of prohibited preservatives such as formaldehyde contravenes the Preservatives in Food Regulations (食物內防腐劑規例) and is liable to a maximum fine of HK$50,000 and imprisonment for 6 months.
  2. For foods containing natural formaldehyde, there is no international consensus reference on their levels.
  3. The testing of formaldehyde in food is included in our food surveillance programme. Follow-up action will be undertaken when there was suspected abuse of formaldehyde in foods.

Advice to the Public

  1. Patronise reliable and reputable food premises and food retailer, both in Hong Kong and abroad.
  2. Formaldehyde is soluble in water. The public is advised to soak food products e.g. mushroom in water and wash them thoroughly, and adequately cook them before consumption.
  3. Take a balanced diet in order to reduce risks related to food intake.

Advice to the Trade

  1. Do not use formaldehyde in food.
  2. Obtain the supply of raw materials e.g. mushroom, vermicelli, hydrated food such as tripe, chicken paws, etc. from reliable sources.

Risk Assessment Section
January 2006