Complex Residue Definitions can trigger difficulties inRisk Assessment studies :the CS2 case
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DirectorDr. Popi Kanari
Despo Christodoulou ,Head ofPesticide Residues Lab
The case of CS2 : from Official Controls at the
State General Laboratory – Ministry of Health-Cyprus
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State General Laboratory
Number of analysed samples for Pesticide Residues for2010 adjusted on the number of population for each
member state59th Adv.Forum Meeting
EPRW 2016Limassol
23-27 of May 2016 ,CyprusNational Coordinator/Organiser
State General LaboratoryMinistry of Health
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SubscribeS e a rc h
The Pesticide Residues Laboratory of theState General Laboratory –Cyprus
The National Reference Laboratory (NRL)
being
• Cereals
• Fruits and Vegetables
• Products of animal Origin
• Single methods applied
also to Dithiocarbamates
as RD
(accredited by the Greek Accreditation body ESYD since 2002 according toEN / ISO / IEC 17025)
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Dithiocarbamates
Chemicals used as Fungicides
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Dithiocarbamates (dithiocarbamates expressed as CS2, including maneb,
mancozeb, metiram, propineb, thiram and ziram)
Official SRM method applied in routine analysis:
Chemical cleavage ,by hydrolysis ,of Dithiocarbamates into Carbon Disulphide,and then determining it by GC-FPD.
In case of positive samples (in particular in cases of violating samples) the following mustbe conidered
• ensure that the samples do not contain naturally S-Compounds which canproduce endogenous CS2
• Interferences are known from Natural Precursors eg from Brassica that canthemselves produce CS2 during Hydrolysis
• CS2 is used by itself (not as Dithiocarbamates )as a fumigant in cereals
• Samples treated with Dithiocarbamates will not only contain intactDithiocarbamates but may also have free CS2.
• Apart from the compounds within the definition of the RD, CS2 mightoriginate from other Dithiocarbamates
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Difficulties in evaluation of positive samplesin particular in cases of violating samples
Evaluation of the results is difficult since
• No MRLs for free CS2
• Very difficult to analyse the components of the RDindividually ( dithiocarbamates are very fragile, no officialmethods for all components)
• No MRLs for all individual components(Dithiocarbamates )
How to perform Risk Assessment?
• No Toxicological Data for CS2
• Available Toxicological Data for only some individualcomponents of the RD
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No Toxicological information for Carbon Disulphide
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How to perform a risk assessment in cases of
Dithiocarbamates expressed as CS2?
A real case example with spinach using the PRIMOmodel:with these values below no real concern
ADI ARfD % ARfD
mg/kg bw/day mg/kg bw/day Children Adults
Pesticide: CS2 Ziram
Amount mg/kg 1,2 2,4 0,006 0,08 67,8 26,8
Propineb
MRL mg/kg 0,05 2,3 0,007 0,1 52,0 20,6
Maneb
2,1 0,05 0,2 23,7 9,4
Mancozeb
2,14 0,05 0,6 8,1 3,2
Thiram
1,9 0,01 0,6 7,2 2,8
Metiram
2,1 0,03 0,16 29,7 11,7
Spinach
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How to perform a risk assessment in cases ofDithiocarbamates expressed as CS2?
Using the PRIMO MODEL
ADI ARfD % ARfD
mg/kg bw/day mg/kg bw/day Children Adults
Pesticide: CS2 Ziram
Amount mg/kg 7,6 15,3 0,006 0,08 276,3 149,6
Propineb
MRL mg/kg 1,0 14,5 0,007 0,1 209,5 113,4
Maneb
13,3 0,05 0,2 96,1 52,0
Mancozeb
13,56 0,05 0,6 32,7 17,7
Thiram
12,0 0,01 0,6 28,9 15,6
Metiram
13,6 0,03 0,16 122,8 66,5
Wheat
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A real case example with imported wheat ; With thesevalues below there is concern from possible 3
Dithiocarbamates
Evaluation of the Results of the Wheat sample
Where could CS2, in wheat , originate from ?
from Fumigant CS2 ?
from any of THE 6 DITHIOCARBAMATES and (others not included in thedefinition )or any Combination of them ?
From a combination possibly of the fumigant CS2 and any of theDITHIOCARBAMATES ?
So all these possibilities should be investigated so as to carry outRisk Assessment on CS2
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Evaluation and Risk Assessment studies: the CS2 case
Further Steps taken to shed light on the case and facilitate therisk assessment process
.analysis for the Dithiocarbamates expressed as CS2 wasRepeated
The sample was analysed with SRM method for thedetermination of ETU and PTU metabolites
ETU was detected/PTU not detectedAs this was a case of Scientific interest it was sent to EURL
Analysis at the EURL-SRM a)Results of Dithiocarbamates expressed as CS2were confirmed b) Analysis for free CS2 showed very low concentrations ofCS2 ……
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Metabolites that could give information on the origin ofthe CS2 AFTER CLEAVAGE
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Metabolites that could give information on the origin ofthe CS2 AFTER CLEAVAGE
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Evaluation of the Results of the Wheat sample
Summing up of evaluation of results for CS2 which has been measuredafter in situ Chemical cleavage of Dithiocarbamates in the Lab
Dithiocarbamates
Probinem ,Mancozeb,Maneb ,Thiram and Metineb
have as a metabolite ……… ……. ETU
Dithiocarbamate
Probinem
has a metabolite ………………………..PTU
Dithiocarbamate
Ziram has a metabolite …………………..CS2
ETU was detected/PTU not detected
So all these possibilities should be investigated so as to carry outRisk Assessment on CS2
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Risk Assessment studies: the CS2 case
One knows from which Dithiocarbamate or Combination of these themeasured CS2 originated from
the measured CS2 originated from the fumigant CS2 or a Combination ofthe fumigant CS2 with one or more Dithiocarbamates
This raises again difficulties as there are no toxicological data for CS2and no toxicological data for all Dithiocarbamates to carry out
Risk Assessment
Risk Assessment on the Wheat sample can only be carried out if
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Evaluation and Risk Assessment studies: the CS2 case
The Wheat case with CS2
So it could be a combination of the Fumigant CS2 and Dithiocarbamate/s(NEBAM,METIRAM,MANEB,MANCOZEB) OR a combination of them
It could not be from ZIRAM as ETU was detected and ZIRAM does nothave ETU as a Metabolite
It could be from other Dithiocarbamates outside the scope of thedefinition of RD of Dithiocarbamates
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The risk assessment for the Imported wheat wasinconclusiveTherefore it seems that:
• More work has to be done on risk assessmentfor complex RDs like Dithiocarbamates
• MRLs & Toxicological Data for CS2 are seriously needed• A Common approach on risk assessment
for Dithiocarbamates expressed as CS2 is also needed
Complicated Residue Definitions can triggerdifficulties in Risk Assessment studies: the CS2 case
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59th Adv.Forum Meeting