Frequently Asked Questions on dioxins in food
BfR FAQ, 10 January 2011
During in-house controls carried out by a compound feed manufacturer in the German region of Schleswig-Holstein, feed fats of plant origin were found to be contaminated with dioxins. Apparently, industrial fatty acids had been mixed in with feed fats of plant origin. Various poultry and pork fattening farms, laying hen farms as well as milk production farms received and fed feed with contaminated fats. The regional control authorities of the German Länder have analysed meat, egg and milk samples from the farms that were affected for their dioxin concentration. In some of these samples, the dioxin concentration in meat and eggs was found to exceed the maximum residue limit that is in force in the European Union.
Yet these do not constitute a direct health hazard for consumers. However, in light of preventive consumer protection, dioxin contamination should be minimised as much as possible. An exceedance of the maximum residue limits in foodstuffs is forbidden. The Federal Institute for Risk Assessment (BfR) has compiled questions and answers on dioxins, health risks and the maximum limits in food.
Questions
- What are dioxins?
- How are dioxins formed?
- Which effects do dioxins have on health?
- Through the consumption of which foods are consumers exposed to dioxins?
- What are WHO-PCDD/F-TEQ?
- What are the tolerable daily intakes in place for dioxins?
- Why do different foods have different legal maximum levels for dioxins?
- Why do the maximum levels for dioxins in fish apply to fresh weight while the maximum levels for other foods of animal origin apply to fat content?
- How high is dioxin intake in Germany?
- Why are products taken off the market?
- How can I know where the eggs I am eating come from?
- The maximum residue limit for dioxins in chicken eggs is set at 3 picograms WHO-PCDD/F-TEQ/g fat. Which health risks am I exposed to if I have recently been eating eggs that were more contaminated than they are allowed to be according to the EU maximum li
- Could the dioxin concentration of breast milk increase if breastfeeding women consumed foods contaminated with dioxins?
What are dioxins?
The chemical category of dioxins contains substances that are chemically similar including polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF). All of these substances share a characteristic structure of chlorine atoms bound to carbon rings. Overall, the category of dioxins consists of 200 compounds, composed differently and thus also of different toxicity.
How are dioxins formed?
Dioxins are not produced for certain purposes, but rather occur as by-products especially during combustion processes. They can also occur during forest fires and volcano eruptions. They always occur when organic carbon is burned when chlorine is present and temperatures are above 300 degrees Celsius. Dioxins bind to dust particles, and in this manner they spread throughout the environment.
Which effects do dioxins have on health?
Dioxins are very persistent compounds. They accumulate in fatty tissue and are virtually not metabolised. In animal testing, chronic effects of dioxins were observed to include adverse effects on reproductive function, the immune system, the nervous system and hormone balance. The liver and thyroid gland were identified as the most sensitive organs to dioxin exposure. Some dioxins are assumed to be able to increase the risk of cancer.
Acute poisoning through high doses of dioxins have only been described in human cases as a result of industrial accidents, the uptake of high concentrations at the workplace and as a result of deliberate poisoning. The most common effects are long-term skin dermatitis referred to as "chloracne". Changes in clinical chemical parameters (especially elevated concentrations of triglycerides, cholesterol and transaminase in blood) indicate liver damage and changes in lipid metabolism.
The currently detected dioxin concentration for pork and laying hens as well as eggs in some samples are above the maximum limits set by the European Union. All other food samples that have been analysed had dioxin concentrations below the corresponding maximum limits. However, those exceedances that were found will not result in any direct adverse health effects for consumers. Yet for reasons of consumer protection, dioxin contamination should be minimised as much as possible. In this regard, unnecessary and avoidable additional exposure is not acceptable.
For the assessment of consumer health risk, in addition to dioxin concentrations in foods, the commonly consumed amounts of a food must also be taken into account.
Through the consumption of which foods are consumers exposed to dioxins?
Because dioxins are present everywhere in the environment, their entry into the food chain cannot be avoided completely. Humans take in dioxins mostly through foods of animal origin: meat, fish, eggs and milk as well as products produced from these. Farm animals are exposed to dioxins mostly through soil particles, either directly through pecking or when soil particles stick to feed, and there is additional intake through feed. Dioxins accumulate in the fatty tissue of animals, which is why those foods mentioned above have higher concentrations than foods of plant origin.
What are WHO-PCDD/F-TEQ?
WHO-PCDD/F-TEQ are so-called toxic equivalents. These assign a rank to the 17 toxicologically most relevant dioxins and furans. The system of toxic equivalents accounts for the different degrees of toxicity of individual compounds. The toxicity of individual substances is thus depicted in relation to the compound with the greatest toxicity, the 2,3,7,8-TCDD, better known as “Seveso dioxin”. By multiplication with the respective toxic equivalency factor (TEF), the concentration of each compound as toxic equivalent is calculated. The sum of these then provides the total concentration of toxic equivalents (TEQ), which in relation to effect corresponds to the concentration of pure 2,3,7,8-TCDD
What are the tolerable daily intakes in place for dioxins?
The World Health Organization (WHO) has set the tolerable daily intake (TDI). This is the amount of dioxins that can be taken in daily over a lifetime without effects on the health of consumers.
In the year 2000, WHO derived a TDI in the range of 1 to 4 picograms WHO-PCDD/F-PCB-TEQ per kg body weight. One picogram corresponds to one trillionth (10-12) of a gram.
In 2001, the Scientific Committee on Food (SCF) of the European Union (EU) derived a tolerable weekly intake (TWI) of 14 picograms WHO-PCDD/F-PCB-TEQ per kg body weight.
Why do different foods have different legal maximum levels for dioxins?
Maximum limits are laid down for select foods in the EU. These specifications are essentially based on unavoidable environmental dioxin contamination of foods, so-called background presence.
The maximum limits are listed in the Annex, Section 5 of Regulation (EC) No 1881/2006, which lists the maximum levels set for certain contaminants in foodstuffs. Accordingly, the maximum limit for chicken eggs and egg products is set at 3.0 picograms WHO-PCDD/F-TEQ (sum of dioxins) per gram of fat; for meat and meat products of poultry it is set at 2.0 picograms WHO-PCDD/F-TEQ per gram of fat.
Why do the maximum levels for dioxins in fish apply to fresh weight while the maximum levels for other foods of animal origin apply to fat content?
The maximum levels for dioxins in foods apply to the fat content of foods because dioxins accumulate in the fatty tissue of the meat of the animals from which the foods are produced.
Fish and fish products are an exception to this. Because fish varies greatly in fat content, fresh weight is the preferred reference value for better comparability. The maximum levels for fish also apply to fresh weight.
How high is dioxin intake in Germany?
According to the results of analyses from 2000 to 2003, the daily intake of dioxins and PCBs (as WHO-PCDD/F-PCB-TEQ) through foodstuff in Germany on average amounted to about 2 picograms WHO-PCDD/F-PCB-TEQ per kg body weight and day. Because the environmental burden with dioxins has declined further since then, the current daily amount taken in through food is assumed to be 1-2 picograms WHO-PCDD/F-PCB-TEQ per kg body weight. The reduction in dioxin intake is also reflected in the declining dioxin concentration of breast milk.
Why are products taken off the market?
Foodstuffs that have concentrations of dioxin equivalents that exceed the maximum residue limits set in the EU cannot be sold on the market.
How can I know where the eggs I am eating come from?
Each farm that produces eggs has an individual identification number. This number is part of the so-called producer code which is stamped onto each egg. Exempt are eggs that are sold directly on the farm of the producer or from door to door. The producer code consists of a combination of numbers and letters that clearly indicate from which farm each egg originates.
The maximum residue limit for dioxins in chicken eggs is set at 3 picograms WHO-PCDD/F-TEQ/g fat. Which health risks am I exposed to if I have recently been eating eggs that were more contaminated than they are allowed to be according to the EU maximum li
The long-term intake of smaller amounts of dioxins through food is unavoidable for all of us because these compounds are present everywhere in the environment. Because dioxins are not easily metabolised in the human body, the concentration of dioxins in body fat increases during the course of a lifetime. But adverse health effects are only expected if these concentrations reach a critical amount.
At present, the dioxin level of adults is about 10 picograms WHO-PCDD/F-TEQ per gram of body fat. This means that at a total body fat of 15 kilograms (assumed body weight of 60 kilograms, percentage of body fat of 25 %) the total amount of dioxin in the body is 150,000 picograms. The daily, largely unavoidable intake of dioxins through all foods currently amounts to about 42 picograms. The daily consumption of 2 contaminated eggs with an assumed dioxin concentration of 12 picograms WHO-PCDD/F-TEQ per gram of egg fat (4 times that of the EU maximum limit, corresponds to the highest level found in the current dioxin case) results an additional daily intake of ca. 168 picograms WHO-PCDD/F-TEQ. If someone were to consume 2 of these eggs daily for one month, this would result in the additional intake of ca. 5,000 picograms. This would meant that the total amount of dioxin in the body would increase to about 155,000 picograms WHO-PCDD/F-TEQ; the concentration of body fat of a young adult would increase from 10 to about 43 picograms per gram of body fat.
The consumption of contaminated eggs at this scale would therefore only have a minor impact on the existing dioxin body burden. Only substantially higher concentrations in eggs or other foods of animal origin and substantially longer periods of consumption could lead to considerably greater body burden. Yet at the present state of knowledge, this can be ruled out.
As a result, the potential consumption of contaminated eggs over the past months is not expected to result in a considerable increase in dioxin burden nor in any thereby caused adverse health effects. 20 years ago, the general exposure to dioxins was substantially higher: It amounted to about 30 picograms WHO-PCDD/F-TEQ per gram of body fat in young adults. There are no indications to suggest that dioxin exposure back then had any adverse health effects.
Could the dioxin concentration of breast milk increase if breastfeeding women consumed foods contaminated with dioxins?
Dioxins taken in through food are stored in the body fat of humans and can be measured in women’s breast milk. As the intake of dioxins through foods has decreased, since the late 1980s the dioxin concentrations that are detected in breast milk in Germany continually decline. While between 1986 and 1990 the average dioxin concentration was still 36 picograms WHO-PCDD/F-TEQ per gram of milk fat, in 2009 the mean concentration was 6.3 and the 95th percentile was 10 picograms WHO-PCDD/F-TEQ per gram of milk fat. This constitutes a decline of more than 80 %.
In the present case, the consumption of eggs that exceed the legal maximum levels for dioxins would lead to an insignificant increase in a breastfeeding woman’s total dioxin body burden and thus in the dioxin concentration of her breast milk (cp. example calculation in the previous question). Breastfeeding women thus do not have to worry about their child and should continue to breastfeed as they had previously planned.
