TBS/ AFDC 27 ( 6605 ) P3         
                                         
 
 
   
 DRAFT TANZANIA STANDARD  
 
Code of practice for the prevention and reduction of dioxins, 
dioxin -like  and non -dioxin-like Polychlorinated biphenyls in food 
and feed  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS                                                                                                                     TBS/AFDC 27 (6605) P 3         
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 0 FOREWORD  
Dioxins are a group o f persistent chemicals which are not produced intentionally but are formed during combustion  
(burning) processes and as by -products of industrial processes. PCBs, or polychlorinated biphenyls, are similar  
chemically to the dioxins. They have been used in t ransformers, building materials,  lubricants, coatings, plasticiz ers 
and inks, although their use has now largely been phased out. Both the dioxins and the PCBs are highly resistant to  
breakdown processes, and consequently persist in the environment, follow ed by uptake into the food chain, mainly 
foodstuffs of  animal origin with a high fat content, since these contaminants accumulate in fatty tissues. Foodstuffs in 
which dioxins can occur include meat, fish, eggs and milk.  
 
Dioxins and PCBs are toxic chemica ls that can provoke serious health effects such as cancer, hormone disruption,  
reduced ability to reproduce, skin toxicity and immune system disorders, when exposure to them continues over an  
extended period (a number of years). Short periods of exposure a re not considered to have adverse effects on  
health, unless the levels are very high. Because of their potentially serious health effects and their persistence in  the 
environment, it is essential to minimize  their release into the environment, including th e establishment of  emission 
limits for dioxins to air, prohibition of the use of PCBs, and safe collection, storage and environmentally  compatible 
disposal or destruction of dioxin and PCB -contaminated devices and products.  
This code of practice is therefo re aiming to guide  regulators, farmers, feed and food manufacturers as well as 
consumers to prevent or reduce dioxin and PCB s contamination in foods and feeds.  
 
In the preparation of this code of practice, assistance was drawn  from;  - CXC 62 -2006 code of p ractice for the 
prevention and reduction of dioxins, dioxin -like PCBs and non -dioxin -like PCBs in food and feed.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 1 SCOPE  
This code of practice recommends on measures based on Good Agricultural Practices, Good Manufacturing  
Practices, Good Storage Practices, Good Animal Feeding Practices, and Good Laboratory Practices for regulators, 
farmers, feed and food manufacturers as well as consumers  to prevent or reduce dioxin and PCB contamination in 
foods and feeds. This code appli es to the production and use of all materials intended  for feed (including grazing or 
free-range feeding, forage crop production and aquaculture) and food at all levels whether produced industrially, on 
farms or in households . 
 
This code of practice repres ents a standard of good practice for the prevention and reduction of Dioxins, Dioxin -like 
PCBs and non -Dioxin -like PCBs in food and feed . Compliance with this code  does not confer immunity from relevant 
statutory and legal requirements.  
 
 2 TERMS AND DEFIN ITIONS  
For the purposes of this document, the following terms and definitions apply ; 
  
2.1 anticaking agent  
substance that reduces the tendency of particles of a feed or food to stick  
 
2.2 binder  
substance that increases the tendency of individual particle s of a feed or food to stick  
 
2.3 Congener  
one of two or more compounds of similar chemical structures with respect to classification  
 
2.4 dioxins (PCDD/PCDF)  
include 7 polychlorinated dibenzo -p-dioxins (PCDDs) and 10 dibenzofurans (PCDFs) with similar tox icological 
properties and belong to a group of lipophilic and persistent organic substances. Depending on the degree of 
chlorination (1 –8 chlorine atoms) and the substitution patterns, 75 different PCDDs  and 135 different PCDFs 
(“congeners”), can be distin guished  
 
2.5 dioxin -like PCBs (DL -PCBs)  
include 12 non -ortho and mono -ortho substituted polychlorinated biphenyls (PCBs) showing toxicological properties 
(dioxin -like activity) that are similar to dioxins  
 
2.6 feed 
any single or multiple materials, whether  processed, semi -processed or raw which is intended to be fed directly to 
food producing animals  
 
2.7 food  
any substance, whether processed, semi -processed or raw which is intended for direct human consumption, and 
includes drink, chewing gum and any subst ance which has been used in the manufacture, preparation or treatment 
of “food” but does not include cosmetics, tobacco, medicinal products, narcotic or psychotropic substances, residues 
and contaminants  
 
2.8 feed or food ingredient  
component or constituen t of any combination or mixture making up a feed or food, whether or not it has a nutritional 
value in the diet, including additives. Ingredients are of plant, animal or aquatic origin, or may originate from other 
organic or inorganic substances.  
  
2.9 HAC CP 
Hazard Analysis Critical Control Point   
system that identifies, evaluates and controls hazards which are significant for food safety  
 
2.10 maximum levels  
legally binding maximum concentration of a substance in feed or food, established by a national or international 
authority  
 
2.11 minimum  limit of quantification (LOQ)  
lowest concentration at which the performance of a method or measurement system is acceptable for a specified 
use 
 
2.12 minerals                                                                                                                      TBS/AFDC 27 (6605) P 3         
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 inorganic compounds used in food and feed being required f or normal nutri tion or used as processing aids  
 
2.13 non dioxin -like PCBs (NDL -PCBs)  
includes the 197 PCB congeners other than the 12 non -ortho and mono -ortho substituted PCBs. The NDL -PCBs 
account for the majority of the total PCB contamination, the remai nder being DL -PCBs.   
 
2.14 PCBs  
polychlorinated biphenyls belonging to a group of chlorinated hydrocarbons, formed by direct chlorination of 
biphenyl. Depending on the number of chlorine atoms (1 – 10) and their position at the two rings, 209 different 
compounds (“congeners”) are theoretically possible. The 209 congeners of PCBs include the dioxin -like PCBs (12 
congeners) and the non -dioxin -like PCBs (197 congeners)  
  
2.15 Persistent organic pollutant (POP)  
chemical substance that persists in the environm ent, bio -accumulates through the food web, and poses a risk of 
causing adverse effects to human health and the environment  
  
2.16 trace elements  
chemical elements essential for plant, animal and/or human nutrition in small amounts  
 
3. RECOMMENDED PRACTICES  BASED ON GOOD AGRICULTURAL PRACTICES (GAPs), 
GOOD MANUFACTURING PRACTICES (GMPs), GOOD STORAGE PRACTICES (GSPs), 
GOOD ANIMAL FEEDING PRACTICES (GAFPs), AND GOOD LABORATORY PRACTICES 
(GLPs)  
 
3.1. Control measures within the food value chain  
3.1.1 Air, So il, Water  
3.1.1.1  To reduce dioxin and PCB contamination in the air, food regulator s should recommend to the regulator 
responsible for air pollution measures to restrict uncontrolled burning of wastes, including the burning of landfill sites 
or backyard b urning, and the use of PCP treated wood for domestic heaters.  
3.1.1.2  Control measures to prevent or reduce contamination of the environment by dioxins and PCBs are important. 
To reduce possible contamination of feed or food, agricultural land with unacce ptable dioxin and PCB contamination 
due to local emission, accidents, or illegal disposal of contaminated materials should be identified  by responsible 
regulators .  
3.1.1.3  Agricultural production on contaminated areas should be avoided or should be restri cted if a significant 
transfer  of dioxins and PCBs to feed or food produced on these areas is anticipated.  
 
3.1.1.4  The spreading of sewage sludge contaminated with dioxins and PCBs can lead to dioxins and PCBs 
adhering to vegetation which can increase li vestock exposure. Sewage sludge used in agriculture should be 
monitored, as necessary, for dioxins and PCBs and treated, as necessary.   
3.1.1.5  Livestock, and poultry exposed to contaminated soil may accumulate dioxins and PCBs by consumption of 
contamina ted soil or plants. These areas should be identified and access by certain food producing animals 
controlled. If necessary, the outdoor production in these areas should be restricted.  
3.1.1.6  Source -reduction measures may take many years to reduce contami nation levels in wild fish due to the long 
half-lives of dioxins and PCBs in the environment. To reduce exposure to dioxins and PCBs, highly contaminated 
areas (e.g. lakes, rivers or contaminated marine catching areas) and relevant fish species should be i dentified and 
fishing in these areas should be controlled and, if necessary, restricted.  
  
3.1.2 Feed  
3.1.2.1 General  
3.1.2.1.1.  The bulk of human dietary intake of dioxins and PCBs is due to the concentration of these substances in 
the lipid component of  animal derived foods (e.g., poultry, fish, eggs, meat and milk). In lactating animal’s dioxins 
and PCBs can be excreted in milk, and in laying hens they may concentrate in the fat content of the egg yolk. To 
reduce this transfer, control measures at the f eed and feed ingredients level should be considered. Measures to 
reduce dioxin and PCB levels in feed would have a rapid effect on their concentrations in food of animal origin 
originating from farm animals, including farmed fish. Such measures may include :  
 identification of possibly contaminated areas in the feed supply ecosystem,  
 identification of the origin of frequently contaminated feed or feed ingredients, and  
 monitoring the compliance of feed and feed ingredients with established maximum levels .                                                                                                                     TBS/AFDC 27 (6605) P 3         
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 3.1.2.1.2  Regulators should periodically sample and analyse suspect feed and feed ingredients using recognized 
national or international methods to verify dioxin and PCB levels. This information will determine actions, if needed, 
to minimize dioxin and PCB  levels and allow alternative feed and feed ingredients, if necessary.  
3.1.2.1.3  The purchaser and user should pay attention to and request guarantees from their supplier as regards  
 origin of feed and feed ingredients to ensure that producers and/or comp anies have certified production 
facilities, production processes and quality assurance programs (e.g.  GMP and  HACCP -like principles);  
 accompanying documents confirming compliance with maximum levels, if available, according to national 
requirements.  
 
3.1.2.2 Feed of animal origin  
3.1.2.2.1  Due to the position of their precursors in the food chain, animal derived feed has a higher risk for dioxin and 
PCB contamination compared to plant derived feed. Attention should be paid to avoid dioxins and PCBs from 
entering the food chain through the feeding of animal derived feed to food producing animals. Animal derived feed 
should be monitored, as necessary, for dioxins and PCBs. Feed of animal origin that exceeds maximum  levels  or 
contains elevated levels of diox ins or PCBs should not be fed to animals unless the fat has been removed.  
3.1.2.2.2  If intended for use in feed, fish -oil and other products derived from fish or animal fats should be monitored 
to the extent practicable for dioxins and PCBs. Animal feeds should be in compliance with  their established 
maximum  levels .  
3.1.2.3 Feed of plant origin  
3.1.2.3.1  If potential sources of dioxins and PCBs are anticipated in the vicinity of fields, attention should be paid to 
monitor these areas, as necessary.  
3.1.2.3.2  Cultivation sites irrigated with water or treated with sewage sludge or municipal compost that may contain 
elevated dioxin and PCB levels should be monitored, , for contamination  and take actions where necessary .  
 
3.1.2.3.3 Prior treatment of fields  with herbicides from the chlorinated phenoxyalkanoic acid type or chlorinated 
products like pentachlorophenol should be considered as a potential source for dioxin contamination. Dioxin levels in 
soil and forage plants from sites treated previously with d ioxin-contaminated herbicides should be regularly 
monitored to prevent the transfer of dioxins (and PCBs) to the food chain.  
3.1.2.3.4 Oilseeds and vegetable oil are not significantly contaminated with dioxins and PCBs. This also applies to 
other by -produ cts of oilseed processing (e.g. oilseed cakes) used as feed ingredients. However, certain vegetable 
and animal oil refining by -products (e.g. fatty acid distillates and deodistillates) and spent products used in oil refining 
(e.g. bleaching clays) may cont ain increased levels of dioxins and PCBs and should be analysed, as necessary, if 
used for feed.  
 
3.1.3 Feed and food processing  
3.1.3.1 Drying processes  
3.1.3.1.1  Certain processes for the artificial drying of feed and food (and feed or food ingredient s) and the heating of 
indoor growing facilities (e.g. greenhouses) require a flow of heated gases, either a flue gas -air mix (direct drying or 
heating) or heated air alone (indirect drying or heating). Accordingly, fuels not expected to generate dioxins an d 
dioxin -like compounds should be used. Feed, food and feed or food ingredients that are dried or subjected to heated 
air should be monitored as necessary to ensure that drying or heating processes do not result in elevated levels of 
dioxins and PCBs.  
3.1.3.1.2  The quality of commercial dried feed materials, in particular green fodder, and commercially dried foods 
depends on the selection of the raw material and the drying process. The purchaser should consider requiring a 
certificate from the manufacturer /supplier, confirming that the dried goods are produced applying Good 
Manufacturing Practice s, particularly in the choice of the fuel used for drying or heating and are in compliance with 
nationally -established  maximum levels.  
 
3.1.3.2 Smoking  
Depending on the technology used, smoking can be a critical processing step for increased dioxin content in foods, 
especially if the products show a very dark surface with particles of soot. Such processed products should be 
monitored for dioxins and PCBs, as necess ary, by the manufacturer  and regulators .  
 
3.1.3.3 Milling / Disposal of contaminated milling fractions  
Airborne external deposition of dioxins and PCBs on the surface of all parts of the grain plants as well as the 
adherent dust fraction from the standin g crop is widely removed during the milling process and before the final 
grinding process. If present, most particle -bound contamination is removed in the loading chute with the remaining 
dust. Further external dioxins and PCB contaminations are significan tly reduced during aspiration and sieving. 
Certain grain fractions, especially dust, chaff and mixed screenings  including brans , can have increased dioxin and                                                                                                                    TBS/AFDC 27 (6605) P 3         
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 PCB levels and should be monitored, as necessary. If there is evidence of elevated contamination,  such fractions 
should not be used in food or feed and should be treated as waste.  
 
3.1.3.4 Food preparation  
3.1.3.4.1  Food selection and preparation such as skinning, trimming the fat, in addition to the disposing of pan 
drippings and poaching/boiling l iquids) are practical approaches to reduce exposure to dioxins and PCBs.  
3.1.4 Substances added to feed and food  
3.1.4.1 Minerals and trace elements  
3.1.4.1.1  Some minerals and trace elements are obtained from natural sources. However, experience has sho wn 
that geogenic dioxins may be present in certain prehistoric sediments. Therefore, dioxin levels in minerals and trace 
elements added to feed or food should be monitored as necessary.  
3.1.4.1.2  Reclaimed mineral products or by -products from certain indu strial processes may contain elevated levels of 
dioxins and PCBs. The user of such feed ingredients should verify that dioxin and PCBs are within nationally 
established maximum l evels,  through certification by the manufacturer or supplier.  
 
3.1.4.1.3  Elevated levels of dioxins have been found in ball clay used as an anticaking agent in soybean meal in 
feed. Attention should be paid to minerals used as binders or anticaking agents (e.g. bentonite, montmorillonite, 
kaolinitic clay, diatomaceous earth) and ca rriers (e.g. calcium carbonate) used as feed ingredients. As assurance to 
the user that these substances do not contain minerals with elevated levels (e.g. exceeding nationally - established 
maximum levels,) of dioxins and PCBs, the distributor should provi de appropriate certification to the user of such 
feed ingredients.  
3.1.4.1.4  Feed of some food producing animals is supplemented with trace elements (e.g. copper or zinc). Minerals, 
including trace elements, which are by -products or co -products of industr ial metal production,  have been shown to 
contain elevated levels of dioxins. Such products should be monitored for dioxins and PCBs, as necessary.  
 
3.1.4.2 Ingredients  
Feed and food manufacturers should ensure that all ingredients in feed and food comply  with nationally established 
maximum  levels of dioxins and PCBs.  
 
3.1.5 Harvesting, transport  and storage of feed and food  
3.1.5.1  Measures  to control the risks to c ontamination with dioxins and PCBs during the harvest and storage of feed 
and food  should  be established.     
3.1.5.2  After flooding, crops harvested for feed and food should be monitored for dioxins and PCBs, if there is 
evidence of dioxin and/or PCB contamination in the flood water.  
3.1.5.3  To avoid cross -contamination, the transport of feed  and food should only be performed in vehicles (including 
ships) and in containers that are free of dioxins and PCBs. Storage containers for feed and food should be painted 
only with dioxin and PCB -free paint. The vehicles transporting feeds and foods shou ld not transport the dioxins and 
PCBs rich products at the same time e.g. Gasoline.  
3.1.5.4  Storage sites for feed or food should be free from dioxins and PCB contamination  (i.e do not keep gasoline 
and feeds and foods in one store) . Surfaces (e.g. walls, floors) treated with tar -based paints may result in transfer of 
dioxins and PCBs to food and feed. Surfaces that come in contact with smoke and soot from fires always bear a risk 
of contamination with dioxins and PCBs. These sites should be monitored as ne cessary for contamination before 
use for storage of feed and food.  
 
3.1.5.5 Avoid using wood shaving during transport of frozen fish to prevent contamination by dioxin and PCBs . 
 
3.1.6 Special considerations  of animal keeping (Housing)  
3.1.6.1  Food produ cing animals may be exposed to dioxins and PCBs found in certain treated wood used in 
buildings, farm equipment and bedding material. To reduce exposure, animal contact with treated wood containing 
dioxins and PCBs should be minimized. In addition, sawdust  from treated wood containing dioxins and PCBs should 
not be used as bedding material.  
3.1.6.2  Due to the potential for soil contamination, eggs from free living or free -range hens (e.g. organic farming) 
may have higher levels of dioxins and PCBs compared  to eggs from caged hens and should be monitored, as 
necessary.  
3.1.6.3  Attention should be paid to older buildings as they may have building materials and varnishes that may 
contain dioxins and PCBs. If they have caught fire, measures should be taken to avoid contamination of the feed and 
feed value chain by dioxins and PCBs.                                                                                                                     TBS/AFDC 27 (6605) P 3         
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 3.1.6.5  Pentachlorophenol -treated wood in animal facilities has been associated with elevated levels of dioxins in 
beef. Wood (e.g. railroad ties, utility poles) treated with chemic als such as pentachlorophenol or other unsuitable 
substances should not be used as fence posts for enclosures of free -range animals.  Hay racks should not be 
constructed from such treated wood. The preservation of wood with waste oils should also be avoide d.  
 
3.1.7 Monitoring  
3.1.7.1  Farmers and industrial feed and food manufacturers have the primary responsibility for feed and food safety. 
Testing could be conducted within the framework of a food safety program (e.g. Good Manufacturing Practices, On -
Farm  Safety programmes, Hazard Analysis and Critical Control Point programs, etc.)  Regulators  should enforce the 
primary responsibility of farmers, feed and food manufacturers , distributors and retailers  for feed and food safety 
through the operation of surve illance and control systems at appropriate points along  food or feed value  chain . In 
addition, regulators  should establish their own monitoring programs.  
3.1.7.2  Monitoring programs dealing with contaminations originating from the environment, accidents o r illegal 
disposals should be organized by operators in the feed and food chain and by regulators  in order to obtain additional 
information on food and feed contamination. Products or ingredients at risk or found with elevated concentrations 
should be moni tored more intensively. For example, monitoring programs may include major fish species used in 
food or feed that have been shown to contain elevated levels of dioxins and PCBs.  
 
3.1.8 Sampling, analytical methods, data reporting and laboratories  
 
3.1.8. 2 Methods  for the analysis of dioxin and DL -PCBs could be gas chromatography coupled to high -resolution 
mass spectrometry (GC -HRMS ) or gas  chromatography coupled to tandem mass spectrometry (GC -MS/MS) . and 
bioassay techniques  
3.1.8.3  Gas chromatography (G C) coupled to Electron Capture Detection (ECD) and mass spectrometers (including 
ion trap, low -resolution (LRMS), high -resolution (HRMS) and tandem mass (MS/MS) spectrometers) are used in the 
analysis of NDL -PCBs. The analysis of NDL -PCBs generally does no t require as extensive a clean -up procedure as 
the DL -PCBs or dioxins. For screening purposes, GC -ECD is often used. GC/MS may also be used for screening 
purposes.  
 
3.1.9 Sampling  
Important aspects of sampling for dioxin and PCB analysis are collecting r epresentative samples, avoiding cross 
contamination and deterioration of samples and unambiguously identifying and tracing back samples. To avoid 
cross -contamination, samples should be put in containers or other receptacles that are not reactive and that h ave 
been chemically cleaned or certified to be free of contaminants. All relevant information on sampling, sample 
preparation and sample description (e.g. sampling period, geographic origin, fish species, fat content, size of fish) 
should be recorded.  
 
3.1.10 Analytical methods and data reporting  
3.1.10.1  Analytical methods should be applied only if they meet minimum allowable  limits  of quantification (LOQ) of 
the method of analysis should be in the range of one fifth of the established levels .  
3.1.10.2  Performance of a method of analysis should be demonstrated in the range of the level of interest, e.g. 0.5 x, 
1 x and 2 x level of maximum level with an acceptable coefficient of variation for repeated analysis. The difference 
between upper bound and lower  bound levels should not exceed 20% for feed and food with a dioxin concentration 
of about 1 pg WHO -PCDD/PCDF -TEQ/g fat. If needed, another calculation based on fresh weight or dry matter 
could be considered.  
 
3.1.10.3  Except for bioassay techniques, the results of total dioxin and DL -PCB levels in a given sample should be 
reported as lower bound, medium bound and upper bound concentration by multiplying each congener by their 
respective WHO TEF (toxic equivalent factor) and subsequently summing them up to  give the total concentration 
expressed as TEQ. The three different TEQ ??? (toxic equivalents)  values should be generated reflecting assignment 
of zero (lower bound), half the limit of quantification (medium bound), and limit of quantification (upper bound ) values 
to each non -quantified dioxin and DL -PCB congener. For the analysis of NDL -PCBs the analytical result should also 
be reported as lower -bound, medium bound and upper -bound and indicate clearly to what the analytical result refers 
to (sum of six ind icator PCBs, total PCBs, etc.)  
3.1.10.4  Depending on the sample type, the reported information may also include the lipid or dry matter content of 
the sample as well as the method used for lipid extraction and for the determination of dry matter. This rep ort should 
also include a specific description of the procedure used to determine the LOQ.  
3.1.10.5  A high throughput screening method of analysis with proven acceptable validation could be used to screen 
the samples with significant levels of dioxins and  PCBs. Screening methods should have less than 1% false -negative 
results in the relevant range of interest for a particular matrix. Use of 13C -labelled internal standards for dioxins or 
PCBs allows for specific control of possible losses of the analytes in  each sample. As such, false -negative results                                                                                                                    TBS/AFDC 27 (6605) P 3         
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 can be avoided thus preventing contaminated food or feed from being used or marketed. For confirmatory methods, 
use of these internal standards is mandatory. For screening methods without control of losses duri ng the analytical 
procedure, information on correction of losses of compounds and the possible variability of results should be given. 
Levels of dioxins and PCBs in positive samples (above the level of interest) should be determined by a confirmatory 
metho d.  
 
3.1.11 Laboratories  
3.1.11.1  Laboratories involved in the analysis of dioxins and PCBs using screening as well as confirmatory methods 
of analysis should be accredited by a recognized body operating in accordance with ISO/IEC Guide 58: as revised 
by ISO/IEC 17011 or have quality assurance programs that address all critical elements of accrediting agencies to 
ensure that they are applying analytical quality assurance. Accredited laboratories should follow the ISO/IEC/17025 
standard “General requirement s for the competence of testing and calibration laboratories” or other equivalent 
standards.  
3.1.11.2  Regular participation in interlaboratory studies or proficiency tests for the determination of dioxins and PCBs 
in the relevant feed and food matrices should be conducted according to ISO/IEC/17025 standard.  
 
4 QUALITY  MANAGEMENT AND EDUCATION  
Good Agricultural Practices, Good Manufacturing Practices, Good Storage Practices, and Good Animal Feeding 
Practices are valuable systems for further reduction of dioxin and PCB contamination in the food  value  chain. 
Farmers as well as feed and food manufacturers , distributors and retailers  should  implement and train their 
employee  on control measures to prevent contamination.  Good Laboratory Practices is a valuable  system to ensure 
high quality of the analytical outcome .