CFS announces risk assessment results on dietary exposure to non-dioxin-like polychlorinated biphenyls

The Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department announced today (June 11) the results of a recently completed risk assessment study on dietary exposure of the Hong Kong adult population to non-dioxin-like polychlorinated biphenyls (NDL-PCBs), which showed that it is unlikely for the local population to experience undesirable health effects of NDL-PCBs.

A spokesman for the CFS said, "NDL-PCBs are a group of 197 organic pollutants with similar basic structure, which are persistent in the environment and tend to accumulate in the food chain. Since NDL-PCBs are lipophilic, fatty foods of animal origin such as fish, seafood, meat, eggs and dairy products usually contain a higher level of NDL-PCBs. Concerns over NDL-PCBs are mainly due to their toxic effects on a number of systems, including endocrine and immune systems, the developing nervous system and their cancer-causing potential."

He pointed out that international health-based guidance values had not been developed for NDL-PCBs. The European Food Safety Authority considers the sum of six indicator NDL-PCBs as a suitable representative for all NDL-PCBs in food and some European countries have developed a guidance value of 10 nanograms per kilogram of bodyweight per day (ng/kg bw/day) for the sum of the six indicator NDL-PCBs. The study adopted this guidance value in assessing the health risk posed by NDL-PCBs on the local adult population.

The spokesman said, "A total of 284 composite food samples were tested for the six indicator NDL-PCBs to estimate the dietary exposure to NDL-PCBs of the Hong Kong adult population. Fifty-nine (21 per cent) of them were detected with at least one indicator PCB congener, among which, the majority (50 samples) belonged to the food group "fish and seafood and their products" which was also found to contain a higher level of the sum of the six indicator NDL-PCBs (mean: 0.89μg/kg (lower bound) - 0.93μg/kg (upper bound))."

As regards dietary exposure to NDL-PCBs in the local adult population, the spokesman noted that the lower bound and upper bound exposure estimates of the sum of the six NDL-PCBs for the average population were found to be 0.68 and 1.38 ng/kg bw/day (i.e. 6.8 per cent and 13.8 per cent of the health-based guidance values) respectively. For high consumers, the lower bound and upper bound exposure estimates were found to be 3.08 and 3.84 ng/kg bw/day (i.e. 30.8 per cent and 38.4 per cent of the health-based guidance values) respectively.

The study also found that the main dietary source of NDL-PCBs was "fish and seafood and their products" which contributed to 84.3 per cent of the total exposure. About half of the total exposure was contributed by four fish species, namely salmon (19.9 per cent), mandarin fish (14.7 per cent), pomfret fish (8.5 per cent) and yellow croaker (7.5 per cent).

The spokesman said, "The study results showed that the dietary exposures to the sum of the six indicator NDL-PCBs of the average and high consumers of the local population were below the health-based guidance values. Hence, it was unlikely for the local population to experience undesirable health effects of NDL-PCBs.

"The findings of the study did not provide sufficient justification to warrant changes to the basic dietary advice on healthy eating. The public is advised to maintain a balanced and varied diet which includes a wide variety of fruit and vegetables so as to avoid excessive exposure to any contaminants from a small range of food items. Although the study found that 'fish and seafood and their products' contained higher levels of NDL-PCBs, they are still low comparing with findings of overseas studies. As fish contains many essential nutrients, such as omega-3 fatty acids and high quality proteins, moderate consumption of a variety of fish is recommended," he said.

In addition, the spokesman said that prevention and reduction of human exposure to the chemicals concerned should be done through source-directed measures. International efforts in the elimination of PCBs and their subsequent contamination of food are essential to reduce the dietary exposure to PCBs of the population.

The full report on the study is available on the CFS' webpage at www.cfs.gov.hk.

Ends/Thursday, June 11, 2015