Congener patterns of polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls as a useful aid to source identification during a contamination incident in the food chain

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) are still considered among the most important groups of contaminants in the food chain. Self-control by food producers and official control by authorities are important activities that allow contaminant sources to be traced and promote further reduction in food and feed levels. Strict but feasible maximum levels were set by the EU Commission for food and feed to support this strategy, as well as action levels and thresholds. When products exceed these levels, it is important to trace the source of contamination and take measures to remove it. Congener patterns of PCDD/Fs and PCBs differ between sources and are important tools for source identification. Therefore, patterns associated with different sources and incidents relating to various feed matrices and certain agricultural chemicals were collated from published scientific papers, with additional ones available from some laboratories. The collection was evaluated for completeness by presentations at workshops and conferences. Primary sources appear to derive from 5 categories, i) by-products from production of organochlorine chemicals (e.g. PCBs, chlorophenols, chlorinated pesticides, polyvinyl chloride (PVC)), ii) the result of combustion of certain materials and accidental fires, iii) the use of inorganic chlorine, iv) recycling/production of certain minerals, and v) certain naturally occurring clays (ball clay, kaolinite). A decision tree was developed to assist in the identification of the source

Ensuring the reliability of brominated flame retardant data on food and feed occurrence through harmonised analytical criteria and proficiency testing

The volume of occurrence data on food and animal feed contaminants such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDDs) is slowly increasing as more laboratories develop analytical capability. This data allows an evaluation of current background levels in different countries and regions and is also useful for estimating the health risk through dietary exposure and as evidence for the formulation of future control strategies. Existing data varies in the number of analytes reported and the quality measures applied. In order to ensure reliability and comparability, guidance on analytical criteria such as precision and trueness, limits of quantitation, recovery, positive identification, etc. is provided. These parameters are based on several years of collective experience and allow validation and regular quality control of analysis of individual PBDE congeners and HBCDD stereoisomers. The criteria-based approach also allows laboratories the flexibility to use different analytical methodologies and techniques for generating data. The effectiveness of this approach has been demonstrated by a successful proficiency testing scheme that has been used for a number of years and has attracted an increasing number of participants. The majority of participating laboratories (> 80 %) have been able to demonstrate performance within the 95% confidence interval (│z-score│≤ 2) and a further 10 % of laboratories demonstrated performance with a z-score of (2 <│z-score│< 3). The combined support of these guidance criteria backed by successful proficiency testing will ensure the reliability and comparability of results, in particular, to refine risk assessments and to help the formulation of regulatory policy

WHO- and UNEP-Coordinated Exposure Studies 2000-2019: Findings of Chlorinated Naphthalenes

The concentrations of polychlorinated naphthalenes (PCN) were determined in 40 pooled human milk samples from 39 countries covering all five of the United Nations regional groups. The samples were collected in the 2016-2019 exposure studies on persistent organic pollutants coordinated by the United Nations Environment Programme (UNEP). The median concentration of the sum of 26 PCN was 55 pg/g lipid (range 27 pg/g to 170 pg/g). Human milk from European countries showed considerably higher levels than those found in milk from countries in the African, Asia-Pacific and Latin America/Caribbean regions. The most abundant congeners were the congener pairs PCN 52/60 and PCN 66/67 (inseparable by conventional chromatography) and to a lesser extent PCN 28/36, PCN 42, PCN 46, PCN 48, PCN 59 and PCN 69. Among other adverse biological effects, a critical response of many PCN congeners is dioxin-like toxicity. So, in addition to reporting concentrations of individual congeners, the toxic equivalents (TEQs) were also calculated in these samples, using two sets of relative effect potency (REP) values: a set that has been used in a number of human exposure studies and another set reported by Falandysz et al (2014). The median PCN-TEQ concentration in human milk was 0.07 pg PCN-TEQ/g lipid (range 0.03 pg/g to 0.23 pg/g), when calculated using the human biomonitoring study REPs, and 0.03 pg PCN-TEQ/g lipid (range 0.01 pg/g to 0.10 pg/g), when calculated with other suggested REPs. The vast majority, about 90%, of this TEQ can be attributed to the PCN 66/67 congener pair. Individual REPs for PCN 66 and 67 from in vivo studies are quite different, but a chromatographic separation of these two congeners is not possible under routine GC conditions. Different approaches to estimate the uncertainties showed that the value of the REPs used is more important than the analytical problem to separate PCN 66 and PCN 67. PCN-TEQ based on the two sets of REPs differ approximately by a factor of 2.2, whereas the congener-specific determination was estimated to result in approximately 30% lower concentrations in comparison to the standard method. The assessment of PCN 66 and PCN 67 in order to obtain confirmed TEF would be most important for calculations of the dioxin-like toxicity of PCN, followed by PCN 69. Minor contributions to PCN-TEQ concentrations in human milk come from PCN 52/60, PCN 64/68, PCN 70 and PCN 73. On average, the contribution of PCN-TEQ to the cumulative TEQ (overall sum of toxic equivalents of PCDD, PCDF and dioxin-like PCB WHO2005-TEQ) is between 1% and 2%, with a wider range of up to 5% for the 39 countries of this study. This is about an order of magnitude lower than the contribution of dioxin-like PCB to WHO2005-TEQ (median 27%). In line with the observed higher total PCN concentrations, European countries also showed considerably higher levels of PCN-TEQ than found in the other regions. PCN-TEQ calculated with REPs used in human biomonitoring studies add on average about 2% to the total TEQ of dioxin-like contaminants in Africa, the Asia-Pacific region and Latin American and Caribbean countries and about 4% in European countries. The corresponding contribution of PCN-TEQ calculated using the other set would be 1% in non-European countries and 2% in European countries