RG-8 Regulatory Guidance:
Contaminants in Feed (formerly RG-1, Chapter 7)

Section 2: Action Levels for Dioxins, Furans, Dioxin-like polychlorinated biphenyls (PCBs) and Total PCBs in Livestock Feed

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The CFIA regularly monitors livestock feed for environmental contaminants which have the potential to impact the safety of the food chain and the health of animals. Beginning in 1998, different types of livestock feeds and feed ingredients were surveyed to determine the levels of dioxins, furans, and PCBs. It has been estimated that food is the major source of human exposure to dioxins, furans, and PCBs, with 90 per cent being contributed by foods of animal origin (Fürst, Beck, and Theelen, 1992). Estimates also indicate that 80 per cent of these contaminants found in animal products originate from livestock feeds. Based on initial survey results and a review of the scientific literature, fish meals, fish oils, fish feeds, and mineral ingredients were considered to be potential sources of these contaminants and, as such, have been targeted for regular monitoring as part of the "Dioxin, Furan, and PCB Monitoring Program". The sampling results have been compiled to assess the background levels of dioxins, furans, and PCBs.

Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), which are often referred to simply as "dioxins", are formed during the manufacture of chlorinated hydrocarbons, and so may be present as contaminants in PCBs, organochlorine pesticides, and phenoxyacid herbicides. Bleaching processes using elemental chlorine can also lead to the formation of dioxins. In addition, they are produced when organic matter is burned in the presence of chlorine, and are therefore found in fly ash from incinerators and produced naturally in forest fires. PCDDs and PCDFs are highly persistent in the environment, and are considered ubiquitous environmental contaminants. They can be found at very low levels in all living organisms and are able to bioaccumulate in food chains due to their lipophilic characteristics.

Depending on the degree of chlorination (1 - 8 chlorine atoms) and the substitution pattern, one can distinguish between 75 PCDDs and 135 PCDFs, called "congeners". The toxicity of dioxin congeners varies considerably. Of the 210 congeners, only 17 are of toxicological concern, and the analysis for "Total Dioxins" conducted by the CFIA is based on the combined concentration of these 17 dioxin and furan congeners. Exposure levels or residues are expressed in toxic equivalents (TEQ) of the most toxic congener, 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD), which allows the comparison of analytical results.

The International Agency for Research on Cancer (IARC) has classified 2,3,7,8-TCDD as a Group 1 carcinogen, which indicates that it is carcinogenic to humans. Effects seen in experimental animals include endometriosis, developmental effects at the behavioural level, reproductive effects, and toxicity to the immune system. The biochemical and toxicological effects following dioxin exposure are dependent on the tissue level, not the dose, and are therefore the same regardless of whether the intake is a large dose over a short period or a small dose over a long period.

PCBs are also considered to be persistent pollutants. PCBs differ from PCDDs and PCDFs in that they were intentionally manufactured for use in transformers, insulators, capacitors, etc., while dioxins and furans are produced unintentionally as unwanted by-products. PCBs consist of 209 different congeners and the analysis for "Total PCBs" conducted by the CFIA is based on the combined concentration of 72 of the 209 individual PCB congeners. Some of the 209 congeners, because of their chemical structure and biological activity, are considered to be "dioxin-like".

Twelve to 14 of the most toxic dioxin-like PCBs can also be expressed in toxic equivalents (TEQ). In 1977, the manufacture and import of PCBs was banned in North America, and the PCBs still used in electrical applications are currently being phased out.

Note: From this point in the section, the term "dioxins" will refer to dioxins (PCDDs), furans (PCDFs) and dioxin-like PCBs. The CFIA calculates total dioxins, including dioxin-like PCBs, using the international standardized reporting method of WHO-TEQ (World Health Organization - Toxic Equivalency) with the appropriate 1998 WHO Toxic Equivalency Factors (Van den Berg et al., 1998). This method includes seven dioxin congeners, 10 furan congeners and 12 dioxin-like PCBs. All of the data and action levels (except for total PCBs) in the remainder of this section are expressed using the WHO-TEQ terminology.

Acceptable analytical methods generally include a clean-up/extraction system (liquid-liquid extraction or Soxhlet extraction) and the use of gas chromatography with high resolution mass spectometry. This is the method used by the CFIA laboratory for the analysis of samples. The XDS-CALUX® EPA method #4435 has been reviewed and is an acceptable screening method for minerals. If other methods of analysis are used, the methods must first be reviewed by the CFIA laboratory to determine if the results are acceptable.

Based on the data obtained from sampling as part of the Monitoring Program, action levels have been set for total dioxins in: fish meals; fish oils; fish feeds; and minerals, mineral complexes, macropremixes, and anti-caking agents (see Table 3). Also, based on sampling results, the CFIA has reassessed its Action Level for Total PCBs in marine oilsTable note 3 used as a livestock feed ingredient (see Table 4). 

These action levels are considered interim levels. In the future, these action levels may be lowered, in an effort to continually reduce unnecessary sources of contaminants in foods of animal origin. This approach is consistent with the CFIA's policy of identifying and eliminating sources of contaminants in the food chain.

Feed manufacturers are reminded of their responsibility to produce feeds which are safe for all classes of livestock and to prevent the introduction of contaminants into the food chain via food of animal origin.

Table 3. Summary of Action Levels for Total Dioxins, Furans, and Dioxin-like PCBs (ng WHO-TEQ/kg) for Different Livestock Feed Ingredients.
Livestock Feed Ingredient Action Level
(ng WHO-TEQ/kg)
Fish Meal 3
Fish Oil 16
Fish Feed 6
Minerals, Mineral Complexes, Macropremixes,
and Anti-caking Agents
1.5
Vegetable Oils

For example:

  • Vegetable (palm) oil
  • Hydrogenated vegetable (palm) oil

By-products of Vegetable Oil Manufacturing

For example:

  • Calcium salts of fatty acids
  • Fractionated palm fatty acid distillates
  • Hydrogenated palm fatty acid distillates
  • Palm palmitic acid (C16:0)
0.75 (dioxins and furans only)
1.5
Table 4. Action Level for Total PCBs (mg/kg) for marine oils.
Livestock Feed Ingredient Action Level
(mg/kg)
Marine Oils 0.3

Table notes

Table note 3

For the purposes of this section, marine oils are defined as oils from approved marine sources (e.g. fish oil, mollusc oil), listed in Schedules IV and V of the Feeds Regulations.

Return to table note 3 referrer

References

Fürst, P, Beck, H., and Theelen, R.M.C. Assessment of human intake of PCDDs and PCDFs from different environmental sources. Toxic Substances Journal, 12:133-150, 1992.

Van den Berg et al., Review: Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives, 106:775-792, 1998.

Fact Sheet - CFIA Advises Not to Use Chemically-Treated Wood Near Livestock Feed and Animals

The Canadian Food Inspection Agency (CFIA) is advising livestock producers across Canada not to use chemically-treated wood structures near livestock feed or food-producing animals because they can transfer potentially harmful levels of chemicals into animal products, such as meat, milk and eggs.

As part of the CFIA's residue monitoring program, dioxin levels higher than background were detected in raw milk from two British Columbia dairy operations. The dioxin was found at levels that are not considered an immediate health risk by Health Canada. The levels found did, however, trigger follow-up action to identify and eliminate the source of contamination, in line with Canada's approach to managing dioxin in the food supply. Dioxins are released into the environment through natural and industrial processes and are commonly found in low levels throughout the food chain around the world.

The investigation indicated that chemically-treated wood used in some silage bunkers (animal feed containers) may, in large part, be the source of the dioxin detected. Exposure to wood treated with chemicals, such as pentachlorophenol (PCP), has been shown to result in higher than background levels of dioxins in livestock feed, which can then transfer into animal products. Further follow-up after precautionary measures were implemented indicated lowered levels of dioxin.

Producers should ensure that livestock feed is not stored where it can come into direct contact with chemically-treated wood structures. Animals should also not be allowed to come into contact with chemically-treated wood, including sawdust or shavings that could be used for bedding. At a minimum, bunker silos containing this wood should be lined with a plastic tarp and untreated lumber. Gloves should be worn when handling any treated wood and scraps must be disposed of in accordance with provincial/territorial and municipal regulations.

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