The underlying risk assessment is based on the final List of Endpoints (LoEP) from the EFSA Conclusion (EFSA Journal 2010; 8(10):1716).
List of Endpoints Fate/behaviour
Route of degradation (aerobic) in soil (Annex IIA, point 7.1.1.1.1)
Mineralization after 100 days ‡ 67.81-86.61 % after 120 d, [14C-benzyl] and [14C-purine]
label mixed (n= 4)
Non-extractable residues after 100 days ‡ 11.98-20.96 % after 120 d, [14C-benzyl] and [14C-purine]
label mixed (n= 4) Metabolites requiring further consideration ‡
- name and/or code, % of applied (range and maximum)
None
Route of degradation in soil - Supplemental studies (Annex IIA, point 7.1.1.1.2) Anaerobic degradation ‡
Mineralization after 100 days Not required.
Non-extractable residues after 100 days Not required.
Metabolites that may require further consideration for risk assessment - name and/or code, % of applied (range and maximum)
Not required.
Soil photolysis ‡
Metabolites that may require further consideration Unidentified metabolite code ‘component 1a’, 5.1% at
for risk assessment - name and/or code, % of applied (range and maximum)
10 d; assumed degradation product of adenine, unlikely to be toxicologically relevant
Component 1b, 3.1% at 10 d, identified as adenine
Rate of degradation in soil (Annex IIA, point 7.1.1.2, Annex IIIA, point 9.1.1) Laboratory studies ‡
Parent Aerobic conditions
Soil type X1 pH
* Geometric mean based on the four values at 20°C.
Field studies ‡
Submitted by applicant although not required since lab DT50 is < 60 days. Study conducted on Korean soils with low moisture content (microbial activity not provided). Considered as indicative only by the RMS (France) in original DAR. Longest field DT50 (8 d) used in PECsoil calculations since it is more conservative than lab data.
Parent Aerobic conditions Soil type (indicate if
bare or cropped soil was used).
Arithmetic mean/median n/a
n/a not available.
pH dependence ‡
(yes / no) (if yes type of dependence)
No
Soil accumulation and plateau concentration ‡ Not required
Laboratory studies ‡
Anaerobic conditions – Not studied
X2 pH t. oC / % DT50 /DT90 (d) DT50 (d) St. Method of
1X This column is reserved for any other property that is considered to have a particular impact on the degradation rate.
MWHC 20C pF2/10kPa
(r2) calculation
- - - - - - -
Geometric mean/median - - - -
Soil adsorption/desorption (Annex IIA, point 7.1.2) Parent ‡
Soil Type OC % Soil pH Kd
(mL/g) Koc (mL/g)
Kf (mL/g)
Kfoc (mL/g)
1/n
SK961089, clay loam 4.8 7.5 21.62 451 0.7897
SK104691, silty clay loam 2.7 6.1 24.43 905 0.7615
SK179618, clay loam 3.8 5.5 10.73 282 0.7927
SK566696, loamy sand 0.8 4.2 15.56 1945 0.8178
Arithmetic mean/median 18.0/18.6 896/678 0.79/0.79
pH dependence, Yes or No No.
Mobility in soil (Annex IIA, point 7.1.3, Annex IIIA, point 9.1.2)
Column leaching ‡ Not required.
Aged residues leaching ‡ Not required.
Lysimeter/ field leaching studies ‡ Not required.
PEC (soil) (Annex IIIA, point 9.1.3)
Parent
Method of calculation
DT50 (d): 8 days Kinetics: SFO
Field or Lab: worst case from an indicative field study.
Application data Crop: maize and apples
Depth of soil layer: 5cm Soil bulk density: 1.5g/cm3
% plant interception: 25% for maize, 80% for apples Number of applications: 1
Interval (d): -
Application rate(s): 18 g as/ha for maize, 150 g as/ha for apples
Route and rate of degradation in water (Annex IIA, point 7.2.1)
Hydrolytic degradation of the active substance and metabolites > 10 % ‡
pH 5: Stable: no degradation at 50°C during 5 days
pH 7: Stable: no degradation at 50°C during 5 days pH 9: Stable: no degradation at 50°C during 5 days Photolytic degradation of active substance and
metabolites above 10 % ‡
Direct photolysis: Artificial light (Xenon arc lamp), cycle 12 hours light / 12 hours dark
pH 5: DT50 = 50.6 days (extrapolated) pH 7: DT50 = 19.2 days
pH 9: DT50 = 244 days (extrapolated) Indirect photolysis: no data. Not required.
Quantum yield of direct phototransformation in
water at > 290 nm 6-benzyladenine:
pH 5: 0.00195 pH7: 0.7337 pH 9: 0.8899 Readily biodegradable ‡
(yes/no)
Yes
Degradation in water / sediment
Parent Distribution (max in water 96.6-97.9 % after 0 d. Max. sed 34.6-51.5 % after 6-13 d) Water /
PEC (surface water) and PEC sediment (Annex IIIA, point 9.2.3)
Parent
Parameters used in FOCUSsw step 1 and 2
Version control no. of FOCUS calculator: 1.1 Molecular weight (g/mol): 225.26
Water solubility (mg/L): 64.5
KOC (L/kg): 896 (mean value obtained on 4 soils) 1/n: 0.79
DT50 soil (d): 1.1 days (Lab geometric mean SFO) DT50 water/sediment system (d): 17.1
DT50 water (d): 17.1 DT50 sediment (d): 17.1
Crop interception (%): Maize, minimal crop cover;
Apples, full canopy
DT50 sediment: 1000 d (FOCUS default)
Application rate Crop: Maize and apples
Crop interception: 0 % Number of applications: 1 Interval (d): -
Application rate(s): 18 g as/ha for maize, 150 g as/ha for apples
Application window:
- Maize: March-May for southern Europe, June September for northern Europe
- Apples: 1 May – 31 May for northern Europe and 1 April – 1 May for southern Europe
PEC (ground water) (Annex IIIA, point 9.2.1)
PECgw was originally calculated (RMS France) based on a worst case Koc 20 L/kg, 1/n 0.9. A new adsorption/desorption study has been provided (Kfoc 896 L/kg, 1/n 0.79). However since acceptable concentrations in groundwater were originally achieved using a worst case default Koc, further groundwater calculations were not considered necessary and not performed by the Notifer.
Method of calculation and type of study (e.g.
modelling, field leaching, lysimeter )
For FOCUS gw modelling, values used –
Modelling using FOCUS model(s), with appropriate FOCUSgw scenarios, according to FOCUS guidance.
Model(s) used: PELMO 3.3.2
Scenarios (list of names): Châteaudun, Hamburg, Jokioinen, Kremsmünster, Okehampton, Piacenza, Porto, Sevilla, Thiva
Crop: Maize and apples
Geometric mean parent DT50lab 1.1 d (normalisation to pF2, 20 C with Q10 of 2.2).
KOC: 20 ml/g (worst case default), 1/n= 0.9.
Application rate Application rate: 13.5 g/ha for maize (25% interception), 30 g/ha for apples (80% interception).
No. of applications: 1
Time of application (month or season):
- maize: 30 days after emergence - apples: 4 months after emergence
Fate and behaviour in air (Annex IIA, point 7.2.2, Annex III, point 9.3)
Direct photolysis in air ‡ No data, not required Quantum yield of direct phototransformation No data. Not required.
Photochemical oxidative degradation in air ‡ DT50 of 28 minutes derived by the Atkinson model. OH concentration assumed = 1.5 106 cm3
Volatilisation ‡ No data, not required
Metabolites -
Residues requiring further assessment
Environmental occurring metabolite requiring further assessment by other disciplines (toxicology and ecotoxicology).
Soil: 6-benzyladenine
Surface Water: 6-benzyladenine Sediment: 6-benzyladenine Ground water: 6-benzyladenine Air: 6-benzyladenine
Monitoring data, if available (Annex IIA, point 7.4)
Soil (indicate location and type of study) No data, not required Surface water (indicate location and type of study) No data, not required Ground water (indicate location and type of study) No data, not required
Air (indicate location and type of study) No data, not required
Points pertinent to the classification and proposed labelling with regard to fate and behaviour data
-
Appendix A: Metabolite names, codes and other relevant information of the plant protection product MaxCel with active substance 6-benzyladine .
The compounds shown below were found in one or more studies involving the metabolism and/or environmental fate of active substance benzyladine. The parent compound structure of 6-benzyladenine is shown first in this list and followed by degradation or related compounds.
Compound name
IUPAC name Structural formula
Structure Molecular
Weight [g/mol]
Observed in study (% of occurrence/
formation) 6-benzyladenine N6
-benzyladenine
C12H11N5
N N H CH2
N H
N N
225.26 Parent substance
6.1 Fate and behaviour in soil
6.1.1 Persistence in soil
Article 2.8 of the Plant Protection Products and Biocides Regulations (RGB) describes the
authorisation criterion persistence. If for the evaluation of the product a higher tier risk assessment is necessary, a standard is to be set according to the MPC-INS3 method. Currently this method equals the method described in the Technical Guidance Document (TGD). Additional guidance is presented in RIVM4-report 601782001/20075.
3 INS: international and national quality standards for substances in the Netherlands.
Preceding the harmonisation of the persistence assessment in The Netherlands with regulation 1107/EG, the EU approach for persistence assessment is followed.
For the current application this means the following:
6-benzyladenine
The following laboratory DT50 values measured at 20°C are available for the active substance 6-benzyladenine: 1.0 ; 1.0; 1.2 and 1.1 days (geometric mean 1.1 days). The geometric mean DT50-value of the a.s. can thus be established to be <90 days. Furthermore it can be excluded that after 100 days there will be more than 70% of the initial dose present as bound (non-extractable) residues together with the formation of less than 5% of the initial dose as CO2.
In this way, the standards for persistence as laid down in the RGB are met.
PECsoil
The concentration of the active substance 6-benzyladenine in soil is needed to assess the risk for soil organisms (earthworms, micro-organisms). The PECsoil is calculated for the upper 5 cm of soil using a soil bulk density of 1500 kg/m3.
As the logPow of the substance is < 3 (2.16), a PEC21days is not needed for the assessment of secondary poisoning of birds and mammals through the consumption of earthworms.
Field studies from Korea were submitted as part of the EU review although they are not required as the laboratory DT50 is <<60 days. Though there is no evidence for these soils being representative for European soils, the longest field DT50 (8 d) was used in PEC soil calculations since it is more conservative than the data obtained from laboratory studies conform the EU assessment.
The following input data are used for the calculation:
PEC soil:
Active substance 6-benzyladenine:
Maximum field DT50 for degradation in soil: 8 days Molecular mass: 225.26 g/mol
See Table M.1 for other input values and results.
Table M.1 PECsoil calculations for active substance 6-benzyladenine (tillage depth 5 cm)
Use Rate
[kg a.s./ha]
Freq. Interval [days]
Fraction intercepted * PIECsoil [mg a.s./kg]
(5 cm)
Apple 0.225 1/y - 0.70 0.090
Pear 0.200 1/y - 0.70 0.080
* interception values derived from Table 1.4 in Generic Guidance for Tier 1 FOCUS Ground Water Assessments. (FOCUS, 2011). The interception for both crops is based on the interception values for apples for the growth stage “foliage development”.
These exposure concentrations are examined against ecotoxicological threshold values in section 7.5.
the framework of 'International and national environmental quality standards for substances in the Netherlands' (INS). Revision 2007’. RIVM report 601782001.
6.1.2 Leaching to shallow groundwater
Article 2.9 of the Plant Protection Products and Biocides Regulations (RGB) describes the authorisation criterion leaching to groundwater.
The leaching potential of the active substance 6-benzyladenine is calculated in the first tier using Pearl 4.4.4 and the FOCUS Kremsmünster scenario. Input variables are the actual worst-case
application rate, the crop apples and an interception value appropriate to the crop stage. The date of yearly application is May 25th. No metabolites occurred above > 10 % of AR, > 5 % of AR at two consecutive sample points or had an increasing tendency.
The following input data are used for the calculation:
PEARL:
Active substance 6-benzyladenine:
Geometric mean DT50 for degradation in soil (20C): 1.1 days Arithmetic mean Kom (pH-independent): 519.7 L/kg
Arithmetic mean 1/n: 0.79
Saturated vapour pressure: 6 x 10-7 Pa (25°C) Solubility in water: 64.5 mg/L (20°C)
Molecular weight: 225.26 g/mol Plant uptake factor: 0.0
Q10: 2.58
Other parameters: standard settings of PEARL 4.4.4
The following concentrations are predicted for the a.s. 6-benzyladenine following the realistic worst case GAP, see Table M.2.
Table M.2 Leaching of active substance 6-benzyladenine as predicted by PEARL 4.4.4.
Use Rate substance [kg/ha]
Frequency Interval [days]
Fraction Intercepted *
PEC
groundwater [g/L]
spring
Apple 0.225 1 - 0.7 <0.001
Pear 0.200 1 - 0.7 <0.001
* interception values derived from Table 1.4 in Generic Guidance for Tier 1 FOCUS Ground Water Assessments. (FOCUS, 2011). The interception for both crops is based on the interception values for apples for the growth stage “foliage development”.
Results of Pearl 4.4.4 using the Kremsmünster scenario are examined against the standard of 0.01 µg/L. This is the standard of 0.1 µg/L with an additional safety factor of 10 for vulnerable
groundwater protection areas (NL-specific situation).
From Table M.2 it reads that the expected leaching based on the PEARL-model calculations for the active substance 6-benzyladenine are smaller than 0.01 µg/L for all proposed applications. Hence, the applications meet the standards for leaching as laid down in the RGB.
Monitoring data
Article 2.10b of the Plant Protection Products and Biocides Regulations (RGB) describes the use of the 90th percentile.
There are no data available regarding the presence of the substance 6-benzyladenine in groundwater.
Conclusions
The active substance 6-benzyladenine complies with the requirements laid down in the RGB concerning persistence in soil.
The proposed applications of the product MaxCelcomply with the requirements laid down in the RGB concerning leaching in soil.
6.2 Fate and behaviour in water
6.2.1 Rate and route of degradation in surface water
Article 2.10c of the Plant Protection Products and Biocides Regulations (RGB) prescribes the use of Dutch specific drift percentages.
The exposure concentrations of the active substance 6-benzyladenine in surface water have been estimated for the various proposed uses using calculations of surface water concentrations (in a ditch of 30 cm depth), which originate from spray drift during application of the active substance. The spray drift percentage depends on the use. No drift mitigating measures were proposed by the applicant. As the product is used for fruit thinning, use before May 1st is not relevant.
Concentrations in surface water are calculated using the model TOXSWA GUI v1.0. The following input data are used for the calculation:
TOXSWA:
Active substance 6-bezyladenine:
Geometric mean DT50 for degradation in water at 20C: 12.1 days DT50 for degradation in sediment at 20C: 1000 days (default).
Arithmetic mean Kom for suspended organic matter: 519.7 L/kg Arithmetic mean Kom for sediment: 519.7 L/kg
Arithmetic mean 1/n:0.79
Saturated vapour pressure: 6 x 10-7 Pa (25C) Solubility in water: 64.5 mg/L (20C)
Molecular weight: 225.26 g/mol
Q10: 2.58 (activation energy of 65400 J/mol) Other parameters: standard settings TOXSWA
When no separate degradation half-lives (DegT50 values) are available for the water and sediment compartment (accepted level P-II values), the system degradation half-life (DegT50-system, level P-I) is used as input for the degrading compartment and a default value of 1000 days is to be used for the compartment in which no degradation is assumed. This is in line with the recommendations in the FOCUS Guidance Document on Degradation Kinetics.
In Table M.3, the drift percentages and calculated surface water concentrations for the active substance 6-benzyladenine for each intended use are presented.
Table M.3 Overview of surface water concentrations for active substance 6-benzyladenine in the edge-of-field ditch following spring application
Use Rate a.s.
[kg/ha]
Freq. Inter-val
Drift [%]
PIEC [g/L]
PEC21 [g/L]
PEC28 [g/L]
Spring spring spring
Apple 0.225 1 - 7* 7.49 5.34 4.87
Pear 0.200 1 - 7* 6.66 4.74 4.32
* Drift percentage based on fruit crops with full leaves
The exposure concentrations in surface water are compared to the ecotoxicological threshold values in section 7.2.
Monitoring data
Article 2.10b of the Plant Protection Products and Biocides Regulations (RGB) describes the use of the 90th percentile.
In April 2014, version 3.0 of the Pesticide Atlas was launched, which includes a statistical correlation analysis between concentrations, threshold exceedance and land use, which may indicate probable relationships. In this version also the correlation analysis of land use with the environmental quality standards (EQS) of the Water Framework Directive (WFD) is included.
Data from the Pesticide Atlas are used to evaluate potential exceedances of the authorisation threshold and environmental quality standards (MKN in Dutch, data source
http://www.rivm.nl/rvs/Normen). These environmental quality standards consist either of the harmonised WFD thresholds derived according to the Fraunhofer methodology6 (AA-EQS and MAC-EQS) or of an MPC value (which is usually derived on the basis of outdated guidance). When EQS values according to the Water Framework Directive are available, the MPC value is not used further in the analysis of monitoring data for the purpose of the registration.
For examination against the drinking water criterion, another database (VEWIN) is used, since the drinking water criterion is only examined at drinking water abstraction points. For the assessment of the proposed applications regarding the drinking water criterion, see next section.
6-benzyladenine
There are no data available in the Pesticide Atlas regarding the presence of the substance 6-benzyladenine in surface water.
Drinking water criterion
Article 2.10b of the Plant Protection Products and Biocides Regulations (RGB) describes the use of the 90th percentile.
It follows from the decision of the Court of Appeal on Trade and Industry of 19 August 2005 (Awb 04/37 (General Administrative Law Act)) that when considering an application, Ctgb should, on the basis of the scientific and technical knowledge and taking into account the data submitted with the
6 P.L.A. van Vlaardingen and E.M.J. Verbruggen, Guidance for the derivation of environmental risk limits within
application, also judge the application according to the drinking water criterion ‘surface water intended for drinking water production’.
The assessment methodology followed is developed by the WG implementation drinking water criterion and outlined in Alterra report 16357.
Substances are categorized as new substances on the Dutch market (less than 3 years authorisation) or existing substances on the Dutch market (authorised for more than 3 years).
- For new substances, a preregistration calculation is performed.
- For existing substances, the assessment is based on monitoring data of VEWIN (drinking water board).
o If for an existing substance based on monitoring data no problems are expected by VEWIN, Ctgb follows this VEWIN assessment.
o If for an existing substance based on monitoring data a potential problem is identified by VEWIN, Ctgb assesses whether the 90th percentile of the monitoring data meet the drinking water criterion at each individual drinking water abstraction point.
Active substance 6-benzyladenine has been on the Dutch market for > 3 years (authorised since 01-03-1996). This period is sufficiently large to consider the market share to be established. From the general scientific knowledge collected by Ctgb about the product and its active substance, Ctgb concludes that there are in this case no concrete indications for concern about the consequences of this product for surface water from which drinking water is produced, when used in compliance with the directions for use. Ctgb does under this approach expect no exceeding of the drinking water criterion. The standards for surface water destined for the production of drinking water as laid down in the RGB are met.
6.3 Fate and behaviour in air Route and rate of degradation in air
The vapour pressure of 6-benzyladenine is 6E-7 Pa at 25C. The Henry constant is 1.77E-6 at 25C.
The half-life in air is 28 minutes.
Since at present there is no framework to assess fate and behaviour in air of plant protection products, for the time being this aspect is not taken into consideration.
6.4 Appropriate fate and behaviour end-points relating to the product and approved uses See List of End-points.
6.5 Data requirements None.
Based on the current assessment, the following has to be stated in the GAP/legal instructions for use (WG):
None
7Adriaanse et al. (2008). Development of an assessment methodology to evaluate agricultural use ofplant protection products for drinking water production from surface waters - A proposal for the registration procedure in the Netherlands. Alterra-Report 1635
6.6 Overall conclusions fate and behaviour It can be concluded that:
1. the active substance 6-benzyladenine meets the standards for persistence in soil as laid down in the RGB.
2. all proposed applications of the active substance 6-benzyladenine meet the standards for leaching to the shallow groundwater as laid down in the RGB.
3. all proposed applications of the active substance 6-benzyladenine meet the standards for surface water destined for the production of drinking water as laid down in the RGB.