Introduction

1. Cadmium is a metallic element that occurs naturally in the Earth's crust. It can also be released to the environment by human activities. Cadmium has a number of industrial applications such as electroplating, pigment production, manufacture of plastic stabilisers and pigments, nickel-cadmium batteries and electronics, etc. Fertilisers produced from phosphate ores, industrial operations such as mining, mining refining are important sources of environmental contamination.

2. For non-smokers, food is the main source of cadmium intake for the general population. Plants, animals, fish and shellfish will take up cadmium when grown in contaminated environment (soil, air, water, fertilizers, feeding stuffs, etc). However for smokers, tobacco smoke is an important source of exposure to cadmium.

Toxicity of Cadmium

1. Animal studies show that an acute intoxication of cadmium may cause damage to the gastrointestinal tract as well as affecting functions of the liver, heart and kidney. However, acute toxicity of cadmium due to dietary exposure is very unlikely.

2. With chronic toxicity to cadmium, the kidney appears to be the sensitive organs. Adverse effects such as abnormal excretion of protein, glucose and amino acid in urine as a result of renal tubular dysfunction have been observed in humans.
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3. The Joint Food and Agriculture Organization / World Health Organization Expert Committee on Food Additives (JECFA) has evaluated the safety of cadmium and established a provisional tolerable weekly intake (PTWI) of 7£gg per kg body weight (bw) to it. PTWI is an estimate of the amount of a contaminant that can be ingested over a lifetime without appreciable risk. An intake above the PTWI does not automatically mean that health is at risk. Transient excursion above the PTWI would have no health consequences provided that the average intake over long period is not exceeded as the emphasis of PTWI is a lifetime exposure.

4. The International Agency for Research on Cancer (IARC) of the World Health Organization considered that there was sufficient evidence of carcinogenicity of cadmium and cadmium compounds in humans upon occupation exposure, and classified them as Group 1 agents. However, available evidence suggested that cadmium did not appear to have significant genotoxic and carcinogenic potential via the oral route.

Local Study

1. Food and Environmental Hygiene Department (FEHD) conducted a study on dietary exposure to heavy metals of secondary school students in 2002 and the results suggested that the overall dietary exposures to cadmium for both average and high consumers of secondary school students were 2.49£gg/kg bw/week and 5.71£gg/kg bw/week respectively. Both were well below the PTWI of 7£gg per kg bw established by JECFA. Major toxicological effects arising from dietary exposure of the secondary school students to cadmium are therefore not anticipated.

2. Results of the above study also suggested that the ¡§seafood other than fish¡¨ food group was the main contributor (33%) of dietary exposure to cadmium, followed by the ¡§cereal and cereal products¡¨ (27%) and ¡§vegetables¡¨ (17%) groups.

Regulatory Control

1. In Hong Kong, the Food Adulteration (Metallic Contamination) Regulations provide, amongst others, maximum permissible concentrations of cadmium in different food categories. The levels are set at not more than 0.1 parts per million (ppm) for vegetables and cereals, 2 ppm for fish, crab-meat, oysters, prawns and shrimps, and 0.2 ppm for meat of animal and poultry, respectively.

2. FEHD has been conducting routine surveillance for heavy metals including cadmium in foods collected from import, wholesale and retail levels. Any person who sells food containing cadmium above the legal limit will be prosecuted and upon conviction, is liable to a fine of $50,000 and imprisonment for 6 months. FEHD will continue to monitor the level of cadmium in food in Hong Kong.

Advice to the Trade

1. To observe good agricultural practices to minimise cadmium contamination in food crops, animals, poultry and fish.

2. To obtain food supplies from reliable sources.

3. To soak and wash well vegetables particularly leafy ones in clean water before they are further processed or consumed.

4. Before preparing food, wash hands thoroughly to prevent contamination to food.

Advice to the Public

1. To be vigilant in selecting your foods. Don't buy foods from dubious sources.

2. To soak and wash well vegetables particularly leafy ones in clean water before they are further processed or consumed.

3. Before preparing food, wash hands thoroughly to avoid contamination to food.

4. To take a balanced diet so as to avoid excessive exposure to contaminants from a small range of food items. Fruit and vegetables are important components of a healthy diet as they are good sources of dietary fibre, vitamins and minerals.


Risk Assessment Section
February 2006