Research project NP/DD/27 (Research action NP)
Polyhalogenated aromatic hydrocarbons (PHAHs) have been identified world-wide in a variety of wildlife, domestic and human tissues as well as in food, water and soil samples. Belgium is one of the West-European countries with the highest environmental levels of dioxin-like substances. Some of the compounds belong to the most toxic manmade substances ever known. They are very resistant to biological and chemical degradation. Even if future emissions are reduced as planned, PHAHs still remain in the environment for many years. Due to their lipophylic character, they accumulate in the food chain and are a treat to human health. The major uptake route is the diet. Few data exist of the actual levels of these compounds in dietary fat. Few measurements are available. This is due to the complexity of the chemical analysis. The compounds always occur as complex mixtures. Chemical measurements of different dioxins, dibenzofuranes, biphenyls are possible but they are labour and time expensive. The successful introduction of limit values for dioxins in the diet is only possible if these levels can be adequately monitored.
The aim of this proposal is to provide a rapid and sensitive screening method for the identification of foods that contain high levels of toxicologically relevant dioxin-like compounds. Liver cells cultured in vitro may be suitable for this purpose. The cells emit a light signal that can be quantified if dioxin-like substances bind to the intracellular arylhydrocarbon (Ah) receptor. Binding to the receptor initiates cellular responses, some of these are associated with toxicity. The binding affinity to the receptor has been shown directly related with toxic potency. The most toxic dioxin congener (tetrachloro-p-dioxin = 2,3,7,8 TCDD) has the highest known binding affinity. The cellular responses of liver cells are sensitive, reproducible and can be quantified as has been shown after exposure to pure compounds. The cellular method will be optimised and miniaturised to allow routine-analyses. We will look into a method to expose the cells to PHAHs, which are present in milkproducts, in eggs, fish and meat. Fat extraction and further isolation of the compounds from the fatextract may be necessary to overcome possible interference between the light signal and the foodmatrix. The reproducibility and liability of the bioassay will be validated. Results from the bioassay will be compared with results obtained from chemical analysis, which have been performed in parallel on identical foodsubstances. The aim is to produce a standard procedure for routine measurement of potentially toxic PHAHs in food and to identify the test condition that guaranties the quality of the results. The bioassay should allow to screen rapidly a large number of food samples. This knowledge may contribute to the protection of human health. Positive samples will be identified and may be subsequently analysed chemically in order to identify the nature of the compounds that contribute to the toxic signal.
If the optimised protocol is available various samples of milk, eggs, fish and meat will be measured for their content of dioxin-like substances. The food substances may be selected from different geographical regions. Selection of the samples will be performed in collaboration with the federal ministry of Public Health and the ministry of Agriculture. The aim is to obtain representative data of the levels of dioxin-like substances in food and to fill the actual gaps of knowledge. This information may improve calculations of the daily dietary intake of toxic PHAHs and may possibly lead to the identification of pointsources. The information may provide a more solid base for risk assessment and the establishment of concentration limits for foodproducts. A validated and rapid screening method should allow adequate monitoring of the levels of PHAHs. This will stimulate and enable Belgium to fulfill its international obligations to reduce emissions of toxic PHAHs.
Een snelle in vitro biologische test voor controle van dioxine -achtige stoffen in voeding: eindverslag
Brussel: DWTC, 2001 (SP0819)
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Een snelle in vitro biologische test voor controle van dioxine -achtige stoffen in voeding: operanionele samenvatting
Brussel: DWTC, 2001 (SP0820)
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Een snelle in vitro biologische test voor controle van dioxine -achtige stoffen in voeding: executive summary
Brussels: OSTC, 2001 (SP0821)
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