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The Centre for Food Safety (CFS) released the first report under the First Hong Kong Total Diet Study (the Study) today (December 13). The Study covers over 130 specified substances and this first report studied dioxins and dioxin-like polychlorinated biphenyls (PCBs) in food.
According to the findings in the report, the population in Hong Kong will be unlikely to experience major undesirable health effects from dioxins and dioxin-like PCBs in its diet.
The Study aimed to estimate the dietary exposures of the general population and various population subgroups to a range of substances, including contaminants and nutrients, and thus assess any associated health risks. The total diet of the population is the focus of the Study.
A total of 150 food items were chosen for the Study according to the food consumption patterns of the Hong Kong population. They were used for testing the levels of over 130 substances, including pesticide residues, persistent organic pollutants, metallic contaminants, mycotoxins, macro nutrients and elements. By combining them with the food consumption data, the dietary exposures to those selected substances of the population were then estimated.
The CFS collected 1 800 samples between March 2010 and February this year. These samples, prepared in table-ready form, were combined into 600 composite samples for tests and analyses of various substances. Among them, 142 composite samples were used in the study of dioxins and dioxin-like PCBs.
"Dioxins" in this report refers to polychlorinated dibenzo-para-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), whereas "dioxin-like PCBs" refers to PCBs that exhibit toxicological properties similar to dioxins. Due to similarity in toxicity profiles and mechanisms of action, the two are generally regarded as the same group for assessment although they come from different sources.
A spokesman for CFS said, "Dioxins and dioxin-like PCBs are environmental contaminants persist in the environment and bioaccumulate in the food chain. Food of animal origin, such as meat, dairy products, eggs and fish is the main dietary source.
"Long term exposure to such contaminants would have toxic effects on the endocrine system, immune system and the developing nervous system, and would cause cancers," he said.
According to the safety reference value set by the Joint Food and Agriculture Organization /World Health Organization Expert Committee on Food Additives (JECFA) of the United Nations, the provisional tolerable monthly intake (PTMI) for dioxins and dioxin-like PCBs is 70 picogrammes (pg)/kg of body weight (bw) per month, expressed as toxic equivalent (TEQ).
Study findings showed that among the 142 composite samples covering 71 kinds of foods, about 66 per cent of the test results were detected with dioxins and dioxin-like PCBs.
Among all the food groups, "fish and seafood and their products" contained the highest level of the contaminants (mean: 0.440 pg TEQ/g), followed by "eggs and their products" (mean: 0.137 pg TEQ/g), "fats and oils" (mean: 0.094 pg TEQ/g) and "meat, poultry and game and their products" (mean: 0.091 pg TEQ/g).
The three food items with the highest levels of dioxins and dioxin-like PCBs belonged to the same food group "fish and seafood and their products". They were mandarin fish (mean: 1.056 pg TEQ/g), oyster (mean: 0.926 pg TEQ /g) and pomfret fish (mean: 0.885 pg TEQ/g).
Dietary exposures to these contaminants were 21.92 and 59.65 pg TEQ/ kg bw/month for average and high consumers of the population respectively, which amounted to 31.3 per cent and 85.2 per cent of the safety reference value (70 pg TEQ/kg bw/month). It is unlikely to pose a health risk to the general population.
The spokesman said, "Study results also showed that the main dietary source of dioxins and dioxin-like PCBs was fish and seafood and their products which contributed to 61.9 per cent of the total exposure, followed by meat, poultry and game and their products, which contributed to 20 per cent of the total exposure. The fatty part of food usually contains higher level of dioxins.
"Fish and fishery products, being an important source of dioxins and dioxin-like PCBs, accounted for 55.6 per cent of total exposure."
The spokesman advised members of the public to trim fat from meat and to consume low fat dairy products as well as maintain a balanced and varied diet which include a wide variety of fruits and vegetables. People should avoid consuming only a small range of food items. These measures would reduce the intake of dioxins and dioxin-like PCBs.
"Fish contains many essential nutrients, such as omega-3 fatty acids and high quality proteins. People should consume a variety of fish moderately and should not worry about the excessive exposure of dioxin, thus reducing fish consumption," he said.
The First Hong Kong Total Diet Study started in March last year and will be completed in 2014. The results of other substances will be released in phases and uploaded to the CFS' webpage at www.cfs.gov.hk.
Ends/Tuesday, December 13, 2011
Issued at HKT 11:03
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