Food Safety Focus (27th Issue, October 2008) – Incident in Focus
Melamine Tainted Milk and Milk Products
Reported by Ms Melva CHEN, Scientific Officer,
Risk Assessment Section, Centre for Food Safety
In September 2008, cases of kidney stones affecting infants who have consumed melamine-tainted infant formula were reported in the Mainland. Most of the cases in Gansu province were found to have consumed Sanlu infant formula for three to six months. Subsequently, the Mainland authority announced that a number of infant formulae made and sold in the Mainland were found to contain melamine, with the Sanlu brand having the highest level (up to 2 563 ppm). Sanlu infant formula was not available in Hong Kong . Nevertheless, follow-up actions undertaken by the Centre for Food Safety (CFS) found melamine in a number of milk and milk products available in Hong Kong . Many parents worried about the health of their children. This article provides more information on food safety relating to melamine.
Uses of Melamine
Melamine (also known as tripolycyanamide) is an industrial chemical used for the production of melamine resins, which are used in glues, paper, textiles as well as plastics including tableware, kitchen utensils, etc. Besides the potential adulteration of food, exposure to melamine for the general population has been considered to be low.
Melamine in Food
Melamine is neither a food ingredient nor a permitted food additive in any countries. It is not allowed to be added to food in any quantity. Melamine scrap was added to milk in the Mainland to cause a false increase in the measurement of protein in dairy products.
In 2007, melamine was found in pet food ingredient manufactured in China and exported to the United States . This led to the death of a large number of dogs and cats due to kidney failure.
In the present incident, melamine contamination has been found in a number of milk and milk products in China , Hong Kong and many countries around the world.
Health Effects of Melamine Consumption
Melamine can cause crystals formation in urinary tract. In severe cases, these small crystals can form kidney stones, blocking the small tubes in the kidney, stopping the production of urine, causing kidney failure and in some cases death. Melamine has been shown to have caused cancer in animals but there was inadequate evidence to show that melamine can cause cancer in human. Laboratory studies showed that melamine did not damage genetic materials in cells or cause malformation in foetus. Infants are particularly at risk of developing adverse health effects as a result of consuming melamine tainted milk because milk is their major food, and the amount of melamine intake per body weight is much higher than that of adults who consume a variety of foods. According to the epidemiological information obtained from the Mainland, over 99% of the victims were children aged 3 years or below. As at 14 October 2008 , seven children in Hong Kong were found to have kidney stones relating to the consumption of suspected melamine tainted milk/milk products. Three of them, however, mainly lived in the Mainland and had consumed milk/milk products that were purchased in the Mainland.
Affected children may experience symptoms of irritability for unknown reasons, blood in urine, little or no urine (in acute renal failure), stones in urine, high blood pressure, or pain over the kidney region.
Safe Intake Level
In 2007, the US Food and Drug Administration has derived a Tolerable Daily Intake (TDI) of 0.63 mg/kg bw/day for melamine. Based on the Mainland experience, infants and young children (0-3 years) may be more vulnerable to the effects of melamine, as such the TDI was lowered by the CFS to 0.32 mg/kg bw/day for this age group in assessing the risk.
Regulatory Control on Melamine
To protect public health, the Government took emergency action and amended the Harmful Substances in Food Regulation (Cap. 132AF). Under the Regulation, milk, any food intended to be consumed principally by children under the age of 36 months and any food intended to be consumed principally by pregnant or lactating women shall not contain melamine exceeding 1 mg/kg. For other food, melamine level shall not exceed 2.5 mg/kg. The amended regulation was gazetted and came into operation on 23 September 2008 , subject to negative vetting of the Legislative Council in October. The regulatory standards set by the Government are generally in line with those of overseas food safety authorities (including Australian and the European Union authorities) and adequate to protect public health.
- is not allowed to be added to food in any quantity;
- can cause crystals formation in urinary tract;
- -tainted products that exceed the legal limits should not be consumed.
Surveillance Action of CFS
The CFS has been testing various milk, milk products and other food products for melamine since September 2008. As at 14 October 2008 , more than 2 350 food samples such as beverages, baby foods, frozen confections, bakery products, etc, were examined. 29 of them failed to meet the standards set. The test results of all the food products sampled are posted on the CFS website.
Advice to Consumers
- Consumers are understandably concerned about the possible adverse health effects associated with the consumption of the affected products. Nevertheless, there is no cause for undue alarm.
- If food products have melamine levels exceeding the legal limits, consumers should not consume them.
- Adverse health effects are unlikely after usual consumption of foods meeting the legal limits.
- Children should seek medical advice if they have urinary symptoms including the development of urinary stone and with history of prolonged exposure to melamine contaminated dairy products.
Advice to Trade
- Should not sell food products that have been found to contain melamine or use them as ingredients;
- Should ensure that their food products comply with the legal standards for melamine and are fit human consumption.
Interested readers may visit the CFS web page on Melamine in Mainland's Milk Powder Incident for further information.