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Food Safety

The never-ending dioxin crisis

The recent preemptive closure of 4,700 farms in Germany, mainly dedicated to poultry and swine, has reopened the debate over dioxin contamination. The discussion focuses on aspects as important as toxicity thresholds, how to reduce exposure levels or how to improve the oversight of production processes

XAVIER PUJOL GEBELLÍ| JANUARY 14TH, 2010

The use of Agent Orange in the Vietnam war produced some of the
most irrefutable evidence to date about the true impact of dioxins on
human health

The German government is in the midst of a crisis that recently forced it to preventatively close 4,700 farms after detecting dioxin contamination levels that exceeded, in some cases up to 77 times, the levels established as acceptable by the World Health Organization (WHO). It is not the first time that Germany has been affected by a crisis of this nature, nor is it the first time that the European Union faces a potentially toxic food contamination from dioxins.

Periodically, as evidenced by previous episodes in Belgium and Holland, a potential dioxin contamination means chicken, pig or cattle farms have to be closed as a precautionary measure and thousands of animals have to be slaughtered and incinerated to root out any possibility of the spreading of this toxic pollutant.

In the most acute cases of dioxin contamination, like the one in Germany, the cause is normally found in incidents related to the feeding of farm animals. Almost always, the feed is mixed with contaminated organic fats. And although these episodes cause a great impact, both socially and economically to consumers and producers, experts are much more concerned about the diffuse but probably more alarming long-term daily intake of dioxins.

Experts are more concerned with the daily intake of dioxins For as miniscule as these daily doses may be, they are still bioaccumulative compounds that are deposited in fatty tissues, from where they can unleash their toxic activity on the rest of the human body. Not surprisingly, according to WHO estimates, 90% of exposure to dioxins is through food, and 80% is from food of animal origin.

Dioxin and dioxins

Despite the usual alarm provoked by any pollution incident of this compound, the truth is that there is reasonable doubt about dioxins’ true impact on human health. It is known that acute exposure to high concentrations of dioxins may result in anything from neurological problems to severe skin conditions or even problems of a teratogenic nature. Under these conditions, dioxins may act as a potent carcinogen.

Nevertheless, researchers have only obtained evidence in humans during two specific episodes. The first occurred during the Vietnam War and the indiscriminate use of the defoliant known as Agent Orange by U.S. armed forces to clear the jungle. The second came in the infamous accident in Seveso, Italy, where an explosion at a factory saw the release of chlorine gas with high concentrations of dioxins.

Except for these two cases, the rest of the acute toxic effects of dioxins have been obtained by extrapolation from laboratory animals. The problem is that there is not just one type of dioxin, but several. Also, not all have the same degree of toxicity, and the same compound can be lethal in a guinea pig but not in a rodent

Dioxins’ true impact is unknown and not all have the same degree of toxicity The fact is that dioxins are a large family of compounds of varying and even null toxicity. The most toxic of all known forms is 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD). But there are 22 possible isomers of dibenzo-p-tetrachloro dioxins, and up to 75 possible congeners of dibenzo-p-dioxins (PCDD).

These are all artificial products. They are formed in thermal processes or through the destruction of organic compounds that incorporate chlorine in their composition. This is the case of some herbicides and fungicides or materials made from PBC (banned for over two decades) or PVC, still in use.

Among their emission sources stand out municipal and medical waste incinerators, paper mills that use chlorine as a bleaching and metal refineries. They are usually dispersed in the atmosphere after burning, a factor that explains their enormous ubiquity. But it is not uncommon to find them in residues of these or other processes, especially in oils, given their hydrophilic nature.

From farm to fork

The key question in the case of German farms scandal is how the dioxins reached the farms. And the answer is through contaminated feed presumably produced by the firm Harles & Jentzsch. Further back, the original source of contamination could be in the misuse of toxic waste from the production of biodiesel that were mixed with the animal fat used in the production of 150,000 tons of feed, whose distribution would have started 10 months ago.

The long exposure period is what caused the huge amount of preemptive closures. And although it is certain that at least some consumers had exceeded allowable dose levels of dioxins, so far no cases of affected humans have come to light. According to experts, we will have to wait a while to see if there are associated cases of human contamination.

THE VALUE OF TRACEABILITY
The European Union, through the European Food Safety Authority, established control mechanisms that track the course of a meal purchased at any retail outlet back to its primary origin. This tracking mechanism allows for the identification of everything from packaged pasta to eggs, meat or fish. Thanks to this system it was possible not only to identify the farms but also the company supplying the feed and to determine the origin of the contamination. The long time lapse from when the dioxins entered the food circuit until the alert was sounded, 10 months later, has prompted strong criticism from consumer organizations who accuse German authorities of trying to conceal the incident.

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