The final List of Endpoints presented below is taken from the EFSA Conclusion on 6-benzyladenine (EFSA Journal 2010;8(10):1716).
Absorption, distribution, excretion and metabolism (toxicokinetics) (Annex IIA, point 5.1)
Distribution ‡ Rats
Highest concentration was found in stomach wall.
Greater levels than that associated with whole blood were intestine wall, liver kidneys, lungs and ovaries.
Potential for accumulation ‡ No potential for accumulation
Rate and extent of excretion ‡ 80-95% within 24 h mainly via urine (60%)
Metabolism in animals ‡ The major component found in urine was hippuric acid;
the monohydroxylated metabolite of 6BA was also present as a major component in urine.
Other minor components identified in urine were the hydrated adduct of monohydroxylated 6BA,
dihydroxylated 6BA, and the glucuronide conjugates of both the mono and dihydroxylated 6BA.
Parent 6BA was also detected in urine, but was very close to the limit of quantification.
The major identified components in the faecal extracts were hippuric acid and isomers of both mono and dihydroxylated 6BA.
The major identified component in bile was the glutathione conjugate of monohydroxylated 6BA.
Toxicologically relevant compounds ‡ (animals and plants)
6-Benzyladenine
Toxicologically relevant compounds ‡ (environment)
6-Benzyladenine
Acute toxicity (Annex IIA, point 5.2)
Rat LD50 oral ‡ 2094 and 814 mg/kg bw in males and females
respectively and 1584 mg/kg bw (combined) R22
Rat LD50 dermal ‡ >2000 mg/kg bw in both sexes
Rat LC50 inhalation ‡ >5.0 mg/L in both sexes
Skin irritation ‡ Non-irritant
Eye irritation ‡ Non-irritant
Skin sensitisation ‡ Not sensitizing
Short term toxicity (Annex IIA, point 5.3)
Target / critical effect ‡ Rat:
Lower body weight, lower blood glucose level, kidney changes: dilated renal pelvises, mineralised semifluid material within the pelvises and secondary
inflammation.
Limited information on other species (mice and dogs)
Relevant oral NOAEL ‡ 13-week rat: 41 mg/kg bw/day (F)
Relevant dermal NOAEL ‡ No data/ not required
Relevant inhalation NOAEL ‡ No data/ not required
Genotoxicity ‡ (Annex IIA, point 5.4)
No genotoxic potential.
Long term toxicity and carcinogenicity (Annex IIA, point 5.5)
Target/critical effect ‡ No valid data, not required because of the representative uses
Relevant NOAEL ‡ Not available
Carcinogenicity ‡ No valid data/ not required because of the
representative uses.
Reproductive toxicity (Annex IIA, point 5.6) Reproduction toxicity
Reproduction target / critical effect ‡ Rat:
Lower body weight and food consumption (F0 and F1 parents).
Lower weight gain in pup and delay in sexual maturation
Relevant parental NOAEL ‡ M/F: 30/45 mg/kg bw/day
Relevant reproductive NOAEL ‡ M/F: > 115/170 mg/kg bw /day Relevant offspring NOAEL ‡ M/F: 30/45 mg/kg bw /day Developmental toxicity
Developmental target / critical effect ‡ Rat:
Lower body weight and food consumption in dams.
Lower body weight in foetuses, increased incidence of hydrocephalus and skeletal effects.
Rabbit
Lower mean foetal body weights.
R63
Relevant maternal NOAEL ‡ Rat: 50 mg/kg bw/day
Rabbit <10 mg/kg bw/day Relevant developmental NOAEL ‡ Rat: 50 mg/kg bw/day
Rabbit 20 mg/kg bw/day
Neurotoxicity (Annex IIA, point 5.7)
Acute neurotoxicity ‡ No data/ not required
Repeated neurotoxicity ‡ No data/ not required
Delayed neurotoxicity ‡ No data/ not required
Other toxicological studies (Annex IIA, point 5.8)
Mechanism studies ‡ No data/ not required
Studies performed on metabolites or impurities ‡ No data/ not required
Medical data ‡ (Annex IIA, point 5.9)
No evidence of toxicological concern from medical surveillance of manufacturing plant personnel
Summary (Annex IIA, point 5.10) Value Study Safety factor
ADI ‡ Not allocate, not
necessary o o
AOEL ‡ 0.03 mg/kg bw/day Developmental
toxicity study in rabbit
300*
ARfD ‡ Not allocate, not
necessaryo
* an additional safety factor of 3 to account for the LOAEL;
o During the preparation of the EFSA conclusion, a data gap was identified by the residue experts for further quantitative evidence that 6-benzyladenine is a naturally occurring compound, hence the consumer risk assessment could not be finalised. It is noted that the setting of ADI and ARfD might be needed once the clarification on the natural occurrence of 6-benzyladenine is provided;
o o The Review Report for the active substance 6-benzyladenine, in contrast to the EFSA Conclusion, contained an ADI for 6-benzyladenine (0.01 mg/kg bw/day).
Dermal absorption ‡ (Annex IIIA, point 7.3)
MAXCEL formulation (SL, 20 g/L 6-benzyladenine) Concentrate:13 % Spray dilutions:7 %
In vivo dermal absorption study in rats.
Classification and proposed labelling with regard to toxicological data (Annex IIA, point 10)
RMS/peer review proposal Substance classified (6-Benzyladenine) Xn; (Harmful)
R22: Harmful if swallowed
Repr. Cat3; R63: Possible risk of harm to the unborn child
Data requirements active substance
No additional data requirements are identified.
4.1 Toxicity of the formulated product (IIIA 7.1)
The formulation MaxCel does not need to be classified on the basis of its acute oral (LD50 rat >5000 mg/kg bw), dermal (LD50 rat >5000 mg/kg bw) and inhalation toxicology (LC50 rat >4.99 mg/L (4 hr)).
The formulation MaxCel is considered not irritating to skin and eyes.
The formulation MaxCel does not have sensitising properties in a Maximisation test.
4.1.1 Data requirements formulated product No additional data requirements are identified.
4.2 Dermal absorption (IIIA 7.3)
The applicant provided an in vivo dermal absorption study (rat skin) and an in vitro dermal absorption study (human and rat skin). The in vivo dermal absorption study is already agreed at EU level (see List of Endpoints). The dermal absorption values in the List of Endpoints for MAXCEL formulation (SL, 20 g/L 6-BA) are:
- Absorption from undiluted concentrate: 13% (tested concentrate: 17.6 g/L);
- Absorption from diluted spray solution: 7% (tested spray dilution: 0.16 g/L).
In the in vitro study provided by the applicant a concentrate concentration of 1.9% w/w (19 g/kg) and spray dilutions of 0.2 g/L and 0.01 g/L were tested. The in vitro study shows that rat skin is more permeable compared to human skin. The applicant performed a triple pack approach to refine the dermal absorption values in the List of Endpoints.
The concentrations tested in the in vivo study and the in vitro study are not similar. However, as the concentrations are comparable it is considered acceptable to perform a triple pack approach.
The results of the in vitro study show that the ratio between human and rat skin is 1:4.5, 1:4.7 and 1:5.3 for the high, intermediate and low dose, respectively. In the Table below the in vivo rat dermal absorption values are corrected using the ratios between human and rat skin for a prediction of the in vivo human dermal absorption values.
High dose (1.9% w/w)
Intermediate dose (0.16-0.20 g a.s./L)
Low dose (0.01 g a.s./L) In vivo rat dermal absorption
value (%)
13 (12.7) 7 (7.46) n.t.
In vitro human/rat skin ratio 1:4.5 1:4.7 1:5.3
Predicted in vivo human dermal absorption value (%)
2.8 1.6 -
n.t.: not tested.
The predicted in vivo absorption based on the triple pack approach is 2.8% for the high dose and 1.6% for the intermediate dose. For the low dose no triple pack approach can be performed as the low dose was not tested in vivo. The highest intended spray dilution described on the GAP results in a spray concentration of 0.075 g a.s./L. The low dose in the in vitro study is considered a representative spray concentration for the highest intended spray dilution described on the GAP.
The in vitro study shows for both the human and rat skin that the potentially absorbed dose is comparable for the high, intermediate and low dose, i.e., 7.37%, 8.01% and 6.70% for human skin respectively and 33.40%, 37.49% and 35.46% for rat skin respectively. Furthermore, the in vitro study shows that the ratio between human and rat skin is comparable for the high, intermediate and low dose (even somewhat higher for the low dose). Therefore, it is considered acceptable to use the predicted human in vivo dermal absorption value of the intermediate dose in the risk assessment for MaxCel for the spray dilution.
According to the EFSA guidance on dermal absorption (EFSA Journal 2012;10(4):2665), dermal absorption values between 1% and 9% should be rounded to one significant figure. In conclusion, in the risk assessment of MaxCel a dermal absorption value of 3% is used for the concentrate and a dermal absorption value of 2% is used for the spray dilution.
4.3 Available toxicological data relating to non-active substances (IIIA 7.4)
The available toxicological data relating to non-active substances will be taken into account in the classification and labelling of the formulated product.
4.4 Exposure/risk assessments 4.4.1 Operator exposure/risk
Calculation of the EU-AOEL / Tolerable Limit Value (TLV)
For 6-benzyladenine no TLV has been set. The AOEL will be used for the risk assessment.
Since the formulation is applied once during the cultivation season, a semi-chronic exposure duration is applicable for the operator (including contract workers). A semi-chronic AOEL is therefore derived.
6-Benzyladenine is included in Annex I of 91/414/EEC and subsequently approved under Regulation (EC) 1107/2009 and therefore the semi-chronic EU-AOEL of 0.03 mg/kg bw/d (= 2.10 mg/day for a person of 70 kg), based on the developmental toxicity study in rabbits, is applied (see List of Endpoints).
Exposure/risk
Exposure to 6-benzyladenine during mixing and loading and application of MaxCel is estimated with models. The exposure is estimated for the unprotected operator. In general, mixing and loading and application is performed by the same person. Therefore, for the total exposure, the respiratory and dermal exposure during mixing/loading and application have to be combined.
In the Table below the estimated internal exposure is compared with the systemic EU-AOEL.
Table T.1 Internal operator exposure to 6-benzyladenine and risk assessment for the use of MaxCel
Route Estimated internal
exposure a (mg/day)
Systemic EU-AOEL (mg/day)
% AOEL b
Mechanical upward spraying on apple and pear (uncovered, 11.25 L/ha) Mixing/
Loadingc
Respiratory < 0.01 2.10 <1
Dermal 0.81 2.10 39
Applicationc Respiratory 0.04 2.10 2
Dermal 1.15 2.10 55
Total 2.00 2.10 96
Manual upward spraying on apple and pear (uncovered, 11.25 L/ha) Mixing/
Loading
Respiratoryd < 0.01 2.10 <1
Dermalc 0.81 2.10 39
Applicatione Respiratory 0.27 2.10 13
Dermal 2.50 2.10 119
Total 3.59 2.10 171
a Internal exposure was calculated with:
biological availability via the dermal route: 3% (concentrate) and 2% (spray dilution) (see 4.2)
biological availability via the respiratory route: 100% (worst case)
b The risk-index is calculated by dividing the internal exposure by the systemic AOEL.
c External exposure is estimated with EUROPOEM.
d External exposure is estimated with the NL-model.
e External exposure is estimated with the German model (90th percentile).
Since the EU-AOEL is exceeded without the use of PPE for manual upward spraying, an assessment with the use of PPE has to be performed for manual upward spraying.
Table T.2 Internal operator exposure to 6-benzyladenine and risk assessment for the use of MaxCel Route Estimated internal
exposure a (mg/day) Manual upward spraying on apple and pear (uncovered, 11.25 L/ha)
Mixing/
a Internal exposure was calculated with:
a Internal exposure was calculated with:
biological availability via the dermal route: 3% (concentrate) and 2% (spray dilution) (see 4.2)
biological availability via the respiratory route: 100% (worst case)
b The risk-index is calculated by dividing the internal exposure by the systemic AOEL.
c External exposure is estimated with EUROPOEM.
d External exposure is estimated with the NL-model.
e External exposure is estimated with the German model (90th percentile).
f PPE: gloves and coverall during application.
4.4.2 Bystander exposure/risk
The exposure is estimated for the professional unprotected bystander. In Table T.3 the estimated internal exposure is compared with the systemic EU-AOEL.
Table T.3 Internal bystander exposure to 6-benzyladenine and risk assessment during application of MaxCel
Route Estimated internal
exposure a (mg/day)
Systemic EU-AOEL (mg/day)
% AOEL b
Bystander exposure during application in apple and pear
Respiratory 0.02 2.10 1
Dermal 0.05 2.10 2
Total 0.06 2.10 3
a External exposure was estimated with EUROPOEM II. Internal exposure was calculated with:
biological availability via the dermal route: 2% (see 4.2)
biological availability via the respiratory route: 100% (worst case)
b The risk-index is calculated by dividing the internal exposure by the systemic AOEL.
Non-professional bystanders and residents may be exposed via the dermal route to spray drift deposits or by inhalation of vapour drift within or directly adjacent to an application area (bystander), or in the vicinity of the application (resident). The internal bystander and resident exposure is calculated in addition to the internal bystander exposure and risk assessment calculated with EUROPOEM II above, which is intended to estimate the work-related bystander exposure. Two different methods are used: 1) the German model which calculates the total exposure for adults and
transfer; and 2) the UK method which calculates the total bystander exposure for adults, and separately the respiratory and dermal/oral route for resident children. In the Table below the estimated internal exposure values from these methods are compared with the systemic AEL.
Table T.4 Internal bystander and resident exposure to 6-benzyladenine and risk assessment for the application of MaxCel
Route Estimated internal
exposure a (mg/day)
Systemic AEL (mg/day)b
% AOEL c
Bystander exposure during application in representative uses according to the German model
Child Total 0.01 0.48 2
Adult Total 0.02 1.80 1
Resident exposure during application in all representative uses according to the German model
Child Total 0.01 0.48 2
Adult Total 0.02 1.80 1
Bystander exposure during application in representative uses according to the UK method
Adult Total 0.01 1.80 1
Resident exposure during application in representative uses according to the UK method
Child Respiratory 0.12 0.45 28
Dermal+Oral 0.01 0.45 2
a External exposure was estimated according to 1) the German guidance paper for exposure and risk assessment for bystanders and residents (Martin et al. 2008, J. Verbr. Lebensm. 3: 272-281), and 2) the UK method. Internal exposure was calculated with:
biological availability via the respiratory route: 100% (worst case)
biological availability via the dermal route: 2% (see 4.2)
biological availability via the oral route: 100% (see List of Endpoints)
b From the systemic AOEL of 0.03 mg/kg bw/day a specific AEL is derived assuming a body weight of 16.15 or 15 kg for children in the German model or UK method, respectively, and of 60 kg for adults.
c The risk-index is calculated by dividing the internal exposure by the systemic AEL.
4.4.3 Worker exposure/risk
Shortly after application it is possible to perform re-entry activities during which intensive contact with the treated crop will occur. Therefore, worker exposure is calculated. The exposure is estimated for the unprotected worker. In Table T.5 the estimated internal exposure is compared with the systemic EU-AOEL.
Table T.5 Internal worker exposure to 6-benzyladenine and risk assessment after application of MaxCel
Route Estimated internal
exposure a (mg/day)
Systemic EU-AOEL (mg/day)
% AOEL b
Re-entry activities in apple and pear
Respiratory -c 2.10 -c
Dermal 0.55 2.10 26
Total 0.55 2.10 26
a External exposure was estimated with EUROPOEM II. Internal exposure was calculated with:
biological availability via the dermal route: 3% (spray dilution) (see 4.2)
biological availability via the respiratory route: 100% (worst case)
b The risk-index is calculated by dividing the internal exposure by the systemic AOEL.
c No model is available to calculate the respiratory internal exposure. However, the respiratory internal exposure can be considered negligible in view of the fact that the uses concern field activities (outdoors) and no spraying of the product occurs during re-entry activities.
4.4.4 Re-entry
See 4.4.3 Worker exposure/risk.
Overall conclusion of the exposure/risk assessments of operator, bystander, and worker The product complies with the Uniform Principles.
Operator exposure
For the unprotected operator, adverse health effects after dermal exposure to 6-benzyladenine as a result of the application of MaxCel in apple and pear cannot be excluded. Correct use of personal protective equipment will reduce the dermal exposure and results in a sufficient reduction of the exposure to 6-benzyladenine for the application of MaxCel in apple and pear.
Bystander exposure
Based on the risk assessment, it can be concluded that no adverse health effects are expected for the unprotected bystander due to exposure to 6-benzyladenine during application of MaxCel in apple and pear.
Based on the risk assessment, it can be concluded that no adverse health effects are expected for the non-professional bystander and resident (children and adults close to the application or living next to a field treated) due to exposure to 6-benzyladenine during and after application of MaxCel in apple and pear.
Worker exposure
Based on the risk assessment, it can be concluded that no adverse health effects are expected for the unprotected worker after respiratory and dermal exposure during re-entry activities in apple and pear due to exposure to 6-benzyladenine after application of MaxCel.
4.5 Appropriate mammalian toxicology and operator exposure end-points relating to the product and approved uses
See List of Endpoints.
4.6 Data requirements
Based on this evaluation, no additional data requirements are identified.
4.7 Combination toxicology
MaxCel contains only one active substance and it is not described that it should be used in combination with other formulations.