1. High levels of dioxins and PCP found in some batches of guar gum
Single Residue Methods
Community Reference Laboratories for Residues of Pesticides
The guar gum case: Contamination with PCP and dioxins and analytical challenges
Wahl K1), Malisch R1), Kotz A1), Hädrich J1), Anastassiades M2) and Sigalova I2)
1Community Reference Laboratory (CRL) for Dioxins and PCBs in Feed and Food, State Laboratory for Chemical and Veterinary Analysis (Chemisches und Veterinäruntersuchungsamt, CVUA), Bissierstr. 5, D Freiburg, Germany
2Community Reference Laboratory (CRL) for residues of pesticides (single residue methods), State Laboratory for Chemical and Veterinary Analysis (Chemisches und Veterinäruntersuchungsamt, CVUA), Schaflandstr. 3/2, D Fellbach, Germany
Summary
In July 2007, a serious contamination by dioxins and pentachlorophenol was found in guar gum originating from India. In connection with this guar gum incident, however, reliability of some results reported by several laboratories as part of the industries’ in-house quality control systems seemed questionable. Correlation factors between PCP and PCDD/F levels showed a considerable variation. In support of the EU Commission, the CRL for Dioxins and PCBs in Food and Feed in Freiburg, Germany, and the CRL for Residues of Pesticides (Single Residue Methods, SRM) in Stuttgart, Germany, analyzed 12 guar gum samples to check results reported by private laboratories. On the basis of the available comprehensive data and from results of CRL’s own analyses, correlation factors between PCP and dioxin levels were derived. From this study it can be concluded that guar gum containing levels of PCP below 0.01 mg/kg does not contain unacceptable levels of dioxins. For improvement of the reliability of methods applied for the determination of PCP and PCDD/F in guar gum, a joint proficiency test “Determination of Dioxins and PCP in Guar Gum” was organized by both CRLs in 2008.
High levels of dioxins and PCP found in some batches of guar gum
Report on 25 July 2007 through Rapid Alert System for Food and Feed (RASSF) of the European Commission: serious contamination by dioxins and pentachlorophenol in guar gum originating from India.
Very high contamination levels of dioxins and pentachlorophenol found in July 2007 in certain batches of guar gum: up to 480 pg WHO-PCDD/F-TEQ/g product and 4 mg PCP/kg gave reason for serious concern.
Follow up samples confirmed these high levels in certain batches; even higher levels were detected in few cases.
However, also uncontaminated guar gum was found.
Guar Gum
Edible thickening agent extracted from the guar bean.
India produces approximately 80 % of the world’s total production of guar beans.
Food grade guar gum powder authorized as food additive and used as a thickening, emulsifying, binding and gelling additive in a very wide range of foodstuffs.
Industrial grade of guar gum powder for non-food uses.
Reference points of action derived by Commission services for unacceptable levels of dioxins and pentachlorophenol in guar gum
PCP: Regulation (EC) No 396/2005 on maximum residue levels of pesticides in or on food and feed of plant and animal origin does not establish an MRL for PCP. However, according to a Commission Regulation amending Regulation 396/2005, coming into force on 2 September 2008, for pentachlorophenol the default MRL of 0.01 mg/kg (limit of quantification) would apply for all foods and feeds. Currently national MRLs for PCP exist of 0.01 mg/kg and 0.05 mg/kg.
PCDD/F: No maximum levels established for dioxins in guar gum by Commission Regulation (EC) 1881/2006. With reference to other food matrices, levels higher than 0.75 pg WHO- PCDD/F-TEQ /g product are to be considered as unacceptably contaminated with PCDD/F.
Discussion of results of 2008 proficiency test “Determination of Dioxins and PCP in Guar Gum”
2 samples of guar gum originating from India selected for PT:
Sample A: PCDD/F concentration in the range of threshold (0.75 pg WHO-PCDD/F-TEQ/kg product), PCP-level ~ 0.15 mg/kg
Sample B: considerably higher concentrations (about 2 orders of magnitude higher than sample A)
PCDD/F-results
The distribution of the z-scores for sample A and B is illustrated in the following graphs.
Comparison of PCDD/F and PCP results
Correlation between PCP and PCDD/F levels
155 data sets, derived from internal quality control of industry and analyses of official laboratories, were provided by the EU Commission.
Conversion factors (CF), calculated as ratio of concentration of dioxins in pg/g and of PCP in mg/kg, ranged from 0.9 to 2900 pg WHO-PCDD/F-TEQ/g (median between 6 and 28).
As correlation factors between PCP and PCDD/F levels varied widely (see figure down left), the reliability of some results seemed questionable.
Calculation of the WHO-PCDD/F-TEQ results using median CF and a PCP concentration of 0.01 mg/kg (maximum acceptable level) would result in a WHO-PCDD/F-TEQ level between 0.06 and 0.28 pg/g. Including a measurement uncertainty of 50 % for PCP, as usually applied for pesticides, the corresponding dioxin content would lead to a dioxin level of pg/g. In both cases the PCDD/F content would not exceed the level of 0.75 pg/g.
In addition, the corresponding concentrations of PCDD/F and PCP were compared at the particular level of interest (see figure down right). The graph shows the correlation between PCP and PCDD/F levels in the concentration range < 0.02 mg/kg PCP (dotted line). No sample with a PCP concentration below 0.01 mg/kg exceeded the maximum acceptable level for WHO-PCDD/F-TEQ of 0.75 pg/g (straight line).
(n = 54)
(n = 53)
Calculation of z-scores on basis of target standard deviation of 10 %:
About ⅓ of the z-scores outside ± 2 for both samples
Asymmetric distribution: considerably more values with z-score > 2 and 3, tendency to overestimation
About 75 % of reported values between z-score of - 3 and 3 (deviation of ± 30 %) for both samples
Similar distribution for WHO-PCDD/F-TEQ levels and z-scores for both samples
CRL method for PCP
(modified QuEChERS)
Analyses of guar gum samples by CRL for Dioxins and PCBs and CRL for Pesticides-Single Residue Methods
12 contaminated guar gum samples originating from India were obtained from a Swiss company.
Aim: Confirmation of results reported by private laboratories by the CRLs
PCP-results: CRL Stuttgart found much higher PCP concentrations in most cases (up to a factor of 30 higher)
PCDD/F-results: Levels below 50 pg WHO-PCDD/F-TEQ/g comparable, above with considerable deviations
Improvement of reliability of methods for determination of PCP and PCDD/F necessary
Organisation of a joint proficiency test “Determination of Dioxins and PCP in Guar Gum” in 2008 by CRLs for Dioxins and PCBs and for Pesticides-SRM
Distribution of results showed a wider range for PCP compared to the PCDD/F-results for both samples
Distribution comparable to PCDD/F for the laboratories using the method recommended by CRL Stuttgart
Median for results of CRL method comparable to median of all PCP-results
Conclusions
Guar gum (from this particular incident) containing a level of PCP below 0.01 mg/kg did not contain unacceptable levels of PCDD/Fs. Therefore, screening of guar gum samples for PCP allowed to exclude samples with elevated levels of PCDD/F.
Guar Gum PT 2008:
75 % of participating laboratories reported results within ± 3 z-scores of assigned value for WHO-PCDD/F-TEQ; similar distribution of sample A and B
For PCP further evaluation of available data necessary