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Abstract

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

This article describes the results of a survey conducted in 2003 on methods used by different member countries within the Organization for Economic Cooperation and Development (OECD) to evaluate persistent and bioaccumulative pesticides. The objectives were to establish the differences in taking persistence (P) and bioaccumulation (B) into account in the decision-making process and to establish the influence of the assessors' subjectivity to data interpretation and data selection. Fifteen countries participated in the survey, which generated a vast amount of information on decision making, risk assessment, risk classification, and data treatment. Survey results indicated clear differences in approaches to the use of P, B, and toxicity (T) information in scientific risk assessment. Using the same data for 2 different pesticides, several OECD member countries responded differently in classifying both substances as P, B, and T. Differences in regulatory decision-making were also apparent because, based on identical classifications, several OECD member countries adopted different decisions on pesticide registration; recommendations were based, with respect to technical guidance, on data handling, training of assessors, and handling of uncertainty in risk assessment.


FORMULATIONS

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY
  • 1.
    250 emulsifying concentrate (EC), substance A (250 g/L)
  • 2.
    10 water-dispersible granulate (WG), substance A (10 %)

 

Table  .  
Intended usenr. form.aDosageDose a.s.a g/haFreq.aInterval (days)Time of application
  1. a nr. form. = formulation code; a.s. = active substance; freq. = frequency of application.

Sugar beet (leaf spot)10.4 l/ha1001–94–30As soon as damage to the crop is observed. Repeat when necessary
Summer and winter wheat (leaf spot)10.5 l/ha1251 As soon as damage to the crop is observed.
Apples and pears (scab)20.0375% (37.5 g per 100 L water)38–561–54–30March–May. As soon as damage to the crop is observed, until a maximum of 96 h after a scab infection occurs (1,000–1,500 L water/ha).
Table  . Physical and chemical propertiesa
  1. a pKa = dissociation constant; NA = not applicable.

Vapor pressure8 × 10−3Pa20°C
Log Kow5.2pH 7, 20°C
Solubility in water87 μg/LpH 7, 20°C
pKaNA
Molecular weight400g·mol−1

BIOACCUMULATION

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

For Lepomis macrochirus, the bioconcentration factors (BCF) wet weight of the whole organism (ww/wo) of substance A is 5,500 L/kg. The half-life for clearance was 5–8 d. No further elimination after 10 d.

For Anguilla anguilla, the BCF ww/wo of substance A is 4,000 L/kg (in presence of sediment 2% organic carbon [o.c.]).

For Mytilus edulis, the BCF ww/wo of substance A is 10,000 L/kg.

SOIL DEGRADATION

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY
Table  . Laboratory studiesab
  1. a T = temperature; pF = water suction; o.m. = organic matter; DT50 = half-life time for degradation.

  2. b Bound residues were found at a maximum of 28% after 180 d and 25% after 281 d (at the end). CO2 reached maximum 12% after 100 d and maximum 23% after 281 d (end) incubation.

Soil typeIncubationpHT (°C)pF% omDosage (mg/kg)DT50 (d)
Sandy loamAnaerobic8.5253.01.59.7805
LoamAnaerobic6.525 3.610950
LoamAnaerobic6.820 4.210820
loamy sandAerobic5203.040.1240
Silty loamAerobic7.2203.01.50.1229
Silty loamAerobic7.2203.01.51.0368
Silty loamAerobic7.2103.01.51.0554
Silty loamAerobic7.2303.01.51.0297
Silty loamAerobic7.2204.01.51.0430
Sandy loamAerobic8.5253.01.59.7595
LoamAerobic6.5253.03.710620
LoamAerobic6.8203.04.210670

Field studies

Metabolite mA—This metabolite was formed at a maximum of 8% of the applied radioactivity after 182 d in the 0- to 10-cm soil layer. After 369 d, only 4% remained.

Metabolite mB—This metabolite was formed in a field lysimeter study at a maximum of 11% of the applied radioactivity 182 d after application. After 369 d, 8% remained.

Field studies on wheat and bare field in the United Kingdom showed that residues after application in the 3rd y, after repeated applications of 0.075 to 0.150 kg/ha, did not exceed residues found after application in the 1st y. 

Table  .  
Soil typeLocationCropDosage (kg a.s./ha)aDT50 (d)aDT90aRemarks
  1. a a.s. = active substance; DT50 = half-life time for degradation; DT90 = time to reach 90% degradation; EC = emulsifying concentrate.

LoamCanadaNo0.8 >1y250 EC
Sandy loamCanadaNo0.125139>1y250 EC
ClayEnglandNo0.375158>1y250 EC
ClayEnglandNo0.125182>1y250 EC
Sandy clayEnglandNo0.375186>1y250 EC
Sandy clayEnglandNo0.125 >1y250 EC
Silty loamSpainNo0.527124 dDisappears quickly in the 1st month, afterwards more slowly. DT50 based on 1st 3 months and DT90 based on 1st 6 months
Loamy sandSpainNo0.593124 didem
Silty loamSpainNo0.572<1yidem
Silty loamGermanyNo0.15331>1y250 EC
Loamy sandUSA CANo0.13113<1y?

DEGRADATION IN THE AQUATIC ENVIRONMENT

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

Hydrolysis

Substance A does not hydrolyze in water.

Ready biodegradability

Substance A is not readily biodegradable

Degradation in water–sediment systems

DT50 of substance A in 2 water–sediment systems is >800 d. Rapid dissipation from water phase: DT50 10 to 20 d.

FORMULATIONS

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY
Table  . 1. 500 EC, substance B (500 g/L)ab
ApplicationDosageDose a.i.FrequencyTime of application
  1. a a.i. = active ingredient.

  2. b The substance consists of 2 stereoisomers (R- and S). The R-isomers is documented in the efficacy dossier to be the active isomer.

Cereals 750 g/ha1Growth phase, from tillering to stem elongation
Table  . Physical and chemical propertiesa
  1. a pKa = dissociation constant; NA = not applicable.

Vapor pressure3.5 × 10−7 Pa20°C
Log Kow3.220°C
Solubility in water3.3 mg/L20°C
pKaNANA
Molecular weight300g·mol−1

BIOACCUMULATION

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

In Lepomis macrochirus, the BCF ww/wo of the R-isomer of substance B is 50 L/kg. DT50 for clearance is 0.5 d. For the S-isomer, the BCF ww/wo is 400 L/kg. DT50 for clearance is 5 d.

For Lepomis macrochirus, the BCF ww/wo of metabolite A of the R-isomer of substance B is 30 L/kg and of the S-isomer, the BCF ww/wo is 210 L/kg. The DT50 for clearance was 0.5 d for both isomers.

SOIL DEGRADATION

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY
Table  . Laboratory studiesa
Soil typeIncubationpHT (°C)pF% o.m.Dosage a.s. (mg/kg)DT50 S-isomer (d)DT50 R-isomer (d)
  1. a T = temperature; pF = water suction; o.m. = organic matter; DT50 = half-life time for degradation.

  2. b Route of degradation study.

Loamy sandbAerobic5.5202.23.60.119598
Loamy sandbAerobic5.5202.23.62.024077
Silty loamAerobic7.0203.01.40.1177110
Silty loamAerobic5.5203.00.42.020897
Sandy loamAerobic8.0252.5160.111074
Sandy loamAerobic8.0252.5162.012760
LoamAerobic6.9203.020.117075
LoamAerobic6.9203.022.018566
ClayAerobic6.029–314.513.05030

Metabolite R-isomer mA: This metabolite has 2 isomers (50:50%). After 100 d, 30% is formed and at the end 60% (at 180 d). mB: This metabolite is only found in a volatile trap at maximum 13% after 180 d. mC: After 100 d, 6% of this metabolite is found. At the end (after 180 d), 9%. This metabolite is a degradation product of metabolite mA only. Bound residues reached a maximum of 78% after 100 d, 55% after 180 d (at the end). CO2 reached 1% after 100 d, maximum 33% after 281 d (at the end) incubation. 

Table  . Laboratory studies on mA
Soil typeaIncubationpHT (°C)pF%omDosage (mg/kg)DT50 (d) isomers of mA
  1. a T = temperature; pF = water suction; o.m. = organic matter; DT50 = half-life time for degradation.

  2. b Route of degradation study.

       SR
Loamy sandbAerobic5.5202.23.60.19595
Loamy sandbAerobic5.5202.23.61.0120120
Sandy loamAerobic6.0252.52.51.06060
ClayAerobic6.029–314.511.02525
LoamAerobic6.9203.021.08585

Metabolite S isomer, mA: After 100 d, 10% is formed, and 30% at the end (after 180 d). This metabolite has 2 isomers (50:50%). DT50 of both isomers was determined in separate studies (see above). Fraction of other metabolites (unspecified) total <3%. Bound residue reached a maximum of 60% after 180 d; CO2 3% after 180 d.

Field studies

Metabolite mA—This metabolite was formed at a maximum of 25% of the applied radioactivity after 40 to 190 d in the 0- to 10-cm soil layer in the field. After 369 d (end), only 4% remained. 

Table  .  
Soil typeLocationCropDosage (kg a.s./ha)DT50 (d)DT90Remarks
  1. a a.s. = active substance; DT50 = half-life time for degradation; DT90 = time to reach 90% degradation.

LoamUSA CANo0.75501/2 yR-isomer
Sandy LoamUSA KSNo0.50601/2 yR-isomer
ClaySpainNo0.375601/2 yR-isomer
ClaySpainNo0.125401/2 yR-isomer
ClaySpainNo0.1251001yS-isomer
Sandy claySpainNo0.375801 yR-isomer
Sandy claySpainNo0.125901 yR-isomer
Sandy claySpain No0.1252002 yS-isomer
Silty loamUKNo0.5551/2 yR-isomer
Loamy sandUKNo0.5122 monthsR-isomer
Silty loamUKNo0.5981 yR-isomer
Silty loamFranceNo0.51001 yR-isomer
Loamy sandGermanyNo0.75701 yR-isomer
Loamy sandGermanyNo0.751902 yS-isomer

ADSORPTION

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

Kom values for substance B: 2,000; 13,500; 3,600; 2,550 dm3/kg. Kom values for metabolite A: 20, 12, 17, 25 dm3/kg. Values derived from Freundlich isotherms with 1/n between 0.8 and 1.0 and soil o.m. contents between 0.5 and 15% o.m.

In an aged leaching test, metabolite C was formed at 3% of r.a. applied after aging and was after leaching recovered for 3% of the applied radioactivity in the leachate.

DEGRADATION IN THE AQUATIC ENVIRONMENT

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

Hydrolysis

Substance B does not hydrolyze in water.

Ready biodegradability

Substance B is inherently biodegradable.

Degradation in water–sediment systems

In water–sediment systems (10% sediment), no difference in behavior was observed between the 2 isomers. Metabolite mA was found at 6% after 180 d (end) in the sediment; 11% in the water phase after 180 d. 

Table  .  
SubstanceSediment typeT (°C)pHo.m. (%)DT50 Water (d)DT50 sediment (d)DT50 system (d)
  1. a T = temperature; pF = water suction; o.m. = organic matter; DT50 = half-life time for degradation.

Substance BSilt loam205.65.81>180>180
Substance BSand206.70.73>180>180
Substance BLoamy sand207.01.52>180>180
Table  . Separate studies with mA were conducted.
SubstanceSediment typeT (°C)pHo.m. (%)DT50 Water (d)DT50 sediment (d)DT50 System (d)
  1. a T = temperature; pF = water suction; o.m. = organic matter; DT50 = half-life time for degradation.

mASilt loam205.55.760170100
mASand206.40.79015090
mALoamy sand206.91.570180110

APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

  1. Top of page
  2. Abstract
  3. EDITOR'S NOTE
  4. APPENDIX 1: DATA SHEET ON SUBSTANCE A
  5. FORMULATIONS
  6. BIOACCUMULATION
  7. SOIL DEGRADATION
  8. ADSORPTION
  9. DEGRADATION IN AIR
  10. DEGRADATION IN THE AQUATIC ENVIRONMENT
  11. APPENDIX 2 DATASHEET ON SUBSTANCE B
  12. FORMULATIONS
  13. BIOACCUMULATION
  14. SOIL DEGRADATION
  15. ADSORPTION
  16. DEGRADATION IN AIR
  17. DEGRADATION IN THE AQUATIC ENVIRONMENT
  18. APPENDIX 3: LIST OF QUESTIONS TO THE CASE STUDY

Conclusions drawn on the substances in case study 1 and 2, respectively.

  • What's your final conclusion on the Persistency of the substance?

  • What's your final conclusion on the Bioaccumulation potential of the substance?

  • Do the PB properties of the substance give reason to add further element(s) to your normal standard for assessment? If so, in what way?

  • Do the PB properties per se merit risk mitigation or other regulatory decisions like limiting areas of use, ban of product, etc.?

Assessment criteria

  • When does a substance or its metabolite(s) qualify for a risk assessment on persistency or bioaccumulation (PB)? For example: minimum total annual consumption, demonstrated absence of hazard, minimum formation rate per compartment, minimum application rate of product.

  • Do the PB assessment criteria apply to all enantiomers, fermentation products, and by-products of the active substance?

  • Are there different standards per PB criterion for different substances (e.g., active or not)?

  • Is accumulation in compartments because of repeated use over the years or in the region considered as a criterion?

On the use of guidance or protocols

  • What are the guidelines, protocols, or standard operating procedures (SOPs) used in the evaluation of submitted literature on PB?

  • What are the guidelines, protocols, or SOPs used in the product safety assessment on PB (environmental risk assessment)?

  • Standards: Is persistency part of the risk assessment?

  • What are the criteria (e.g., DT50) and standards relating (e.g., 180 d) to persistency?

  • Are the criteria on persistency for the different compartments (soil, water, sediment, groundwater, feed, air) the same?

  • Are lab results equivalent to (or superseded by) results obtained from field studies regarding

  • Formation of metabolites (identity, percentage)

  • Persistency?

  • If field results can outweigh lab results, are there specific criteria that have to be fulfilled (sufficient study replications, sampling strategy, detection limits etcetera)?

  • If a substance is considered to be persistent, what will be the next step in the risk assessment?

  • Standards: Are data on bioaccumulation used in the risk assessment?

  • What are the criteria used for bioaccumulation? BCFfat, BCFww/wo and/or other?

  • Are the criteria on bioaccumulation for the different compartments or functional groups (water, vertebrates) the same?

  • Is elimination/depuration taken into account? If so, how?

  • Are results based on radioactivity acceptable?

  • What property value or level of risk is acceptable? What value triggers further assessment or additional requirements?

  • If a substance is considered to be bioaccumulating, what will be the next step in the risk assessment?

  • Standards: Are data on biomagnification through the food chain used in the risk assessment?

  • What are the criteria used for biomagnification? BCFfat, BCFww/wo and/or other?

  • Are the criteria on biomagnification for the different compartments or functional groups (water, vertebrates) the same?

  • What property value or level of risk is acceptable? What value triggers further assessment or additional requirements?

  • If a substance is considered to be biomagnifying, what will be the next step in the risk assessment?

  • Do the standards on persistency also apply to inorganic compounds and inorganic metabolites?

  • Bound residues can potentially be a source of active compounds if the organic matter is degraded. Are there additional considerations to the criteria listed above for products that generate large amounts of bound residue (e.g., >70% of applied activity)?

  • Has completing the questionnaire made you revise the assessment of the PB criteria or even change conclusions on the substances? What aspects were the most challenging?