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Food Safety Focus (23rd Issue, June 2008) – Food Safety Platform

Persistent Organic Pollutants in Food – Food Safety Implication

Reported by Miss Joan YAU, Scientific Officer,
Risk Assessment Section, Centre for Food Safety

In the last issue, we presented an overview of Persistent Organic Pollutants (POPs), why POPs are present in food, as well as the international treaty, namely the Stockholm Convention, which was initially aimed at the restriction and elimination of a group of POPs, informally called the "dirty dozen". Among this "dirty dozen", DDT and dioxins are the best known and there have been reports that these two groups of substances might be of local concern. In this issue, we would examine these concerns and talk about the food safety aspect of POPs.

What are the Adverse Effects of POPs upon Excessive Dietary Exposure?

The adverse effects of POPs depend on various factors such as the nature of individual POP, the amount and the duration of exposure. Generally speaking, the main concern over POPs for the general population is their possible adverse effects, including their potential to cause cancer, upon long-term dietary exposure. Animal studies demonstrated that some may cause damage to internal organs and immune systems while some may affect reproduction and development. However, related human data upon dietary exposure is limited.

The International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) has evaluated the potential to cause cancer of the "dirty dozen" POPs. One of the dioxin congeners, namely TCDD, can cause cancers in humans. Fortunately, IARC considered that eight other groups of POPs can cause cancers in experimental animals, but are not likely to be cancer causing in humans; whereas three others have limited or inadequate evidence to cause cancers in animals.

How About the Levels of POPs in Food in Hong Kong?

POPs are everywhere in the environment and its presence in food, particularly those of animal origin that is rich in fat (i.e. fish, shellfish, milk, meat, poultry and their products), is inevitable. However, their generally low levels are unlikely to cause immediate health risks. The Centre for Food Safety (CFS) has included almost all POPs of the "dirty dozen" in its routine food surveillance programme.

On the other hand, the Food and Environmental Hygiene Department conducted two risk assessment studies on POPs, namely "Dietary Exposure to Dioxins of Secondary School Students" and "Dietary Exposure to DDT of Secondary School Students" in 2002 and 2006 respectively. The dietary exposures to these two POPs for average and high consumers of secondary school students fell below the respective safety reference values established by the expert groups under WHO. Adverse effects via dietary exposures are therefore unlikely. There is no cause for concern. CFS will continue its effort in conducting risk assessment studies, including the assessment of dietary exposures to the "dirty dozen" POPs, for the general population in Hong Kong .

How to Reduce the Dietary Exposure to POPs?

Environmental control is the primary measure to minimise total exposure to POPs. International organizations and national governments have put much effort in this aspect, e.g. the Codex Alimentarius Commission has developed code of practice for the prevention and reduction of dioxins contamination in food and feed. Nevertheless, as POPs tend to accumulate in animal fat, consumers can take the following to further reduce intake of POPs from the diet:

  1. Reduce the consumption of animal fat, e.g.
    • trim fat from meat and meat products;
    • avoid the use of animal fat for food preparation and cooking;
    • use cooking methods that allow the fats to drain away (e.g. steaming, baking.).
  2. Maintain a balanced diet so as to minimize excessive exposure to POPs from a small range of food items.