| dc.description.abstract | Summary
The 22nd round of the Interlaboratory Comparison on POPs in Food was conducted in 2021 by the Norwegian Institute of Public Health (NIPH). The study included the determination of the 2,3,7,8-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), as well as dioxin-like non-ortho and mono-ortho chlorinated biphenyls (PCBs) in three different food items. Additionally, the participating laboratories could determine the concentrations of six indicator PCBs, polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in the same food samples.
A fourth matrix was also accessible to the participants, designated for the determination of the following poly- and perfluoroalkyl substances (PFASs): Perfluorooctanesulfonate (PFOS), perfluorohexanesulfonate (PFHxS), perfluorooctanoate (PFOA), perfluorononanoate (PFNA), perfluorodecanoate (PFDA) and perfluoroundecanoate (PFUnDA).
The objectives of this interlaboratory comparison study were
A. To offer a tool for quality assurance to the participating laboratories
B. To assess the between laboratory reproducibility
C. To assess the readiness of expert laboratories worldwide to determine levels of chlorinated and brominated persistent organic pollutants, as well as for PFASs, in regular foodstuffs.
With respect to PCDDs/PCDFs, non-ortho PCBs, mono-ortho PCBs, indicator PCBs, PBDEs and α-HBCD, the 2021-round of the study was performed on unfortified homogenates of Sheep meat, Herring and Fish oil. An unfortified homogenate of perch was offered for the determination of PFASs.
If desired, the laboratories could also determine the concentrations of PCDDs/PCDFs, nonortho PCBs, mono-ortho PCBs, indicator PCBs, PBDEs and α-HBCD in standard solutions from Cambridge Isotope Laboratories, provided by NIPH.
The test materials were sent to 62 laboratories worldwide in January and February, and results were returned from 60 of these.
Due to the ongoing corona-pandemic there has been some delays this year. A draft report would normally have been published in July, but due to the extended deadline for submitting results it was not made available on our webpage www.fhi.no/ILC until early October 2021, and the deadline for commenting on the published results was set to November 15th, 2021.
This report presents the reported results for all seventeen 2,3,7,8-substituted PCDDs/PCDFs, the four non-ortho substituted PCBs #77, 81, 126 and 169 and the eight mono-ortho substituted PCBs #105, 114, 118, 123, 156, 157, 167, 189 in the three food items on a fresh weight and lipid weight basis.
The results of eight PBDEs #28, 47, 99, 100, 153, 154, 183 and 209, six indicator PCBs #28, 52, 101, 138, 153 and 180, and total HBCDs as well as the α-, β- and γ-isomers are also presented.
The results of PFOS, PFHxS, PFOA, PFNA, PFDA and PFUnDA in a sample of Perch are also included.
The consensus concentration (assigned value) for each analyte in the four food samples was determined as follows: For the seventeen 2,3,7,8-substituted PCDDs/PCDFs, the four nonortho substituted PCBs and the eight mono-ortho substituted PCBs non-detected congeners were assigned a concentration corresponding to the reported detection limits. The median of all reported concentrations for each analyte was then calculated. All values above twice the median was removed from the calculation. The consensus median and consensus mean as well as standard deviation (SD) were calculated from the remaining data, and this second median was called consensus value.
For the PBDEs, the indicator PCBs and HBCDs the non-detects were removed from the data set. The median of all reported concentrations for each analyte was then calculated. All values above twice the median were removed from the calculation. The consensus median (consensus value) and consensus mean as well as standard deviation (SD) were calculated from the remaining data.
When calculating the results for PFASs in the sample of Perch, we adopted the same approach as we used for the indicator PCBs and PBDEs.
Toxic equivalents (TEQs) were calculated from the consensus medians of individual congeners using the toxic equivalency factors derived by WHO 2006 (from 2012: WHO2006TEQs as opposed to WHO1998TEQs as in the reports published before 2012).
Z-scores for the PCDD/PCDF TEQs were calculated for each laboratory using ±20 % of the consensus TEQs as a value for target standard deviation (σ=0.2), on both fresh weight and lipid weight basis. Further, Z-scores were calculated for the non-ortho PCB TEQ, the monoortho PCB TEQs, the total TEQ, the sum of six indicator PCBs, the sum of eight PBDEs, total HBCD, and the three isomers of HBCD and for each single congener in all three matrices of Sheep meat, Herring and Fish oil (σ=0.2) (both on a fresh weight and a lipid weight basis). The z-scores for PFASs were calculated in the same way, but on fresh weight basis only.
The consensus values of the standard solutions were calculated as mentioned above with the exception of the removal of all values exceeding ±50 % of the median prior to the final calculation of the consensus median and mean. The consensus values for the lipid contents were calculated by first excluding results deviating more than two SD from the mean of all values, and then re-calculating the median, mean and SD.
The sample of Fish oil was the sample in this study with the highest total TEQ (8.2 pg TE/g fw, WHO2006TEFs). For this sample, Z-scores within ±1 were obtained by 85 % of the participating laboratories, and Z-scores within ±2 were achieved by 89 % of the participants (Z scores within ±1 and ±2, corresponds to a trueness of ±20 % and ±40 %, respectively). The Fish oil -sample was followed by the sample of Herring, with a consensus total TEQ of 0.68 pg TE/g fw (WHO2006TEFs). For this sample 89 % of the participants achieved Z-scores within ±1, and 91 % achieved Z-scores within ±2.
For the sample of Sheep meat, which on beforehand was assumed to be the sample with lowest level of contamination (total TEQ=0.0.020 pg TE/g, WHO2006TEFs, fresh weight), Zscores within ±1 were obtained by 42 % of the reporting participants on fresh weight basis, and Z-scores within ±2 was achieved by 60 % of the participants. This clearly mirrors the high number of non-detects reported for the PCDD/PCDFs, and the variation in the reported limits of detection reported by the participants.
The relative standard deviation (RSD) calculated for the total TEQ after removal of outliers was 8.2 and 6.7 % for the two samples that had the highest levels of contamination (Fish oil and Herring, respectively). For the lower contaminated Sheep meat-sample, the corresponding RSD was 16 %. Considering the levels of contamination in the three food samples in this study, it may be concluded that the abilities and performance of laboratories worldwide in determining dioxin-like compounds is generally good.
For the food samples, 39-48 laboratories reported results for the six indicator PCBs. The total consensus concentrations on fresh weight basis for six indicator PCBs were 121 pg/g (12 %) in Sheep meat, 4144 pg/g (8.2 %) in Herring and 50614 pg/g (11 %) in Fish oil, with total RSDs given in parentheses. 1
2-20 laboratories reported concentrations for all seven of the tetra- to hepta-PBDEs and 8-13 laboratories reported concentrations for PBDE-209. The consensus concentrations of the sum of the PBDEs with PBDE-209 excluded, were on fresh weight basis 3.5 (28 %), 430 (12 %) and 3966 (7.3 %) pg/g in Sheep meat, Herring and Fish oil, respectively, with total RSDs given in parentheses. The consensus concentrations for PBDE-209 were 9.7 (n=8, RSD=31 %), 27 (n=13, RSD=63 %) and 68 (n=9, not possible to calculate RSD due to many NDs) pg/g fresh weight in Sheep meat, Herring and Fish oil, respectively.
The consensus concentrations calculated for HBCDs are indicative, as only a few laboratories reported results (n=3-6).
15-16 laboratories reported results for the different PFASs in the sample of Perch. The sample was known to be contaminated with PFOS (consensus concentration 15100 pg/g fw). Eighty-eight percent of the participants obtained a Z-score ±2 for PFOS, and 69 % obtained Z-scores ≤1. For PFDA (consensus concentration 637 pg/g fw), 80 % of the participants obtained z-scores ≤1, and for PFUnDA (consensus concentration was 354 pg/g fw) 60 % obtained z-scores ≤1.
The consensus values for PFHxS, PFOA and PFNA are indicative due to few reported results (many NDs) | |
