Introduction

1. There have been occasional reports on the abuse of formaldehyde as bleaching agents and preservatives in food in the Mainland.
   
   
2. Earlier on, an article in a local magazine reported that a number of food samples they have tested contained formaldehyde. The food items included dried mushrooms and dried bean curd which were brought from different retail shops in Hong Kong.
   
   
3. 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 for industrial use as a disinfectant, raw material in plastic manufacturing and embalming agent. It is a colourless gas at room temperature, highly 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 are dried bean curd, vermicelli and hydrated food such as tripe, chicken paws etc.
   
   
3. However, this chemical also occurs naturally in the environment and can be found naturally in small amounts in a wide range of raw food, including fruits and vegetables, meat, fish, crustacean, etc. High levels of formaldehyde up to 300ppm to 400ppm are found naturally in dried mushroom including shiitake.
   
   
4. The United States Environmental Protection Agency has set an Acceptable Daily Intake (ADI) of 0.2mg/kg body weight for this chemical. The ADI 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 an excessive amount of formaldehyde include systemic acidosis along with gastrointestinal bleeding. According to International Agency on Research on Cancer (IARC), formaldehyde can cause cancer in animals but there is limited evidence of carcinogenicity in humans.

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 (­¹ª«¤º¨¾»G¾¯³W¨Ò) 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. We have set an action level of 63ppm and 300ppm for formaldehyde in fresh and dried shiitake respectively, so that follow-up actions can be undertaken to investigate whether there is intentional use of formaldehyde as a preservative. A similar level was employed by some European countries.
   
   
3. The testing of formaldehyde in food is included in our food surveillance programme. In the past year, for those food products where formaldehyde is likely to be abused, only one sample of dried bean curd was found to contain formaldehyde and follow-up action has been taken.
   
   
4. As regards those food products in which formaldehyde can be present naturally, we have also taken 22 samples of dried mushrooms imported from the Mainland and Japan for laboratory testing. The results of analysis indicated that the amount of formaldehyde detected in these samples corresponded to the studies undertaken by other countries. Only one sample of dried mushroom from the Mainland was found to contain formaldehyde at 380ppm which exceeded the action level of 300ppm and required our follow-up action. According to the local dietary consumption pattern and the level of formaldehyde detected in mushroom, the average daily intake of this chemical from mushrooms for most people in Hong Kong is well below the acceptable daily intake (ADI) as recommended by the United States Environmental Protection Agency.
   
   

Advice to the Public

1. Patronize reliable and reputable food premises and food retailer, both in Hong Kong and abroad.
   
   
2. Observe whether the operators are observing good personal, food and environmental hygiene.
   
   
3. Formaldehyde is soluble in water. The public is advised to soak the incriminated food products e.g. mushroom in water and wash them thoroughly, and adequately cook them before consumption.
   
   
4. 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
April 2002