From Animal Feed to People Food: The Belgian Dioxin Incident.

In January 1999, animal feedlots in Belgium were contaminated with polychlorinated biphenyls (PCBs) and dioxins including polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans. The dioxins, probably originating from oil left at a waste recycling center, entered the food supply via animal feed made with recycled animal fat. (In Belgium, waste fat from recycling centers is commonly mixed with fat from slaughterhouses to make animal feed.) Five hundred tons of the contaminated feed was distributed to farms, mostly poultry operations, throughout Belgium. In this issue, Nik van Larebeke and colleagues from four Flemish universities conclude that the incident may have doubled or tripled the PCB/dioxin body burden of some Belgians [EHP 109:265-273].

News of the incident broke in late May, sparking a public outcry and a scramble by government agencies to assess the human health damage. The Ministries of Public Health and Agriculture ordered testing of over 20,000 samples of beef, pork, poultry, eggs, milk, and fat-containing processed foods found on Belgian grocery shelves. The sampling, conducted between May and August 1999, analyzed the health impact of the contaminants on consumers and provided the materials for the current study.

Dioxins, a group of chemical compounds released by processes such as waste incineration and the burning of household fuel, have been linked to health effects ranging from skin disease to cancer. PCBs are mixtures of synthetic organic chemicals. Like dioxins, PCBs have been linked to cancer; they have also been associated with neurotoxicity, reproductive and developmental toxicity, immune suppression, liver damage, skin irritation, and endocrine disruption.

Van Larebeke and colleagues sorted the food samples into three categories: those traceable to farms that used contaminated feed, those traceable to farms that did not use contaminated feed, and those for which a link with the contamination incident could not be clearly established. The sampling effort by 23 labs measured dioxins with mass spectrometry and quantified PCBs using gas chromatographic techniques along with electron capture or mass spectrometry.

Compared with dioxin incidents elsewhere, the Belgian incident exposed more people but to much smaller amounts of dioxins. The analysis suggests that in terms of added cancer risk, the incident could result in 32-1,540 additional cancer deaths over the projected lifetime of the total Belgian population of 10 million, and PCB exposure could add between 22 and 6,545 cancer deaths. These ranges are based on applying two different risk estimates for lifetime exposure to the amount of contaminants in the incident exposure.

Depending on a person's diet and the chance occurrence of high levels of contamination, however, the effects could be much more serious. The potential impacts of three common dietary patterns typical of the average Belgian citizen were assessed. One pattern assumed the ingestion of 15 grams of heavily contaminated animal fat per day and resulted in a 75% increase in dioxin body burden. Another assumed the ingestion of three portions of heavily contaminated chicken meat per week and resulted in a 42% increase in dioxin body burden. A third common dietary pattern resulted in a 48% increase in dioxin body burden. Some people may have incurred even higher exposures because consumption of products such as milk and derived food items such as sauces and pastries were not factored in to the estimations.

The 1999 Belgian dioxin incident added further risk to background levels that were already high. The authors warn that significant numbers of Belgians who consumed contaminated products temporarily increased their intake of dioxins to a level up to 100 times greater than that recommended by the World Health Organization. Furthermore, conclude the authors, the long-term effects may be particularly hard to detect because of the high background levels. The researchers recommend further monitoring of exposed populations and stricter chemical and physical hygiene, including better screening of materials left at recycling centers.