 Cadmium in Food
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
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