(2RS,3RS)-3-(2-chlorophenyl)-2-(4-fluorophenyl)-[(1H-1,2,4-triazol-1-yl)methyl]oxirane

PBT assessment

PBT assessment: overall result

PBT status:

the substance is PBT / vPvB

Justification:

PBT / vPvB – Assessment of epoxiconazole:

Epoxiconazole meets the criteria for classification as persistance (P) or very persistance (vP). The substance is concluded to be not readily biodegradable (according to OECD criteria, see IUCLID Ch. 5.2.1). Additionally, experimental data on the degradation properties of epoxiconazole are available for three environmental compartments (water, soil, sediment).

The substance has a very high experimental Koc value varying in the range from 945 to 2451 L/kg (@pH 5.9 – 7.3, see IUCLID Ch. 5.4.1). Moreover, in an aerobic water/sediment study under dark conditions (OECD 308, Schnoeder, 2003, see IUCLID Ch. 5.2.2) epoxiconazole was observed to quickly partition from the water phase to the sediment phase as expected due to the high Koc value. Therefore, the sediment and soil are determined to be the major degradation compartments for epoxiconazole. The geometric mean degradation half-life (trigger endpoint) of epoxiconazole in the aerobic water/sediment system was found to be 111.0 days (OECD 308, re-calculated with HS kinetic model, Pape, 2016). The DegT50 in the whole water/sediment system is appropriate for an initial assessment of persistence of epoxiconazole in sediment. Considering the geometric mean DegT50 of 111.0 days epoxiconazole does not fulfil either the P or the vP criterion for sediment.

Regarding the compartment soil, the aerobic half-life DegT50 was calculated to be 390.1 days for the clay loam soil and 173.2 days for the sand soil (re-calculated with SFO kinetic model at 20 °C, Voss, 2016, see IUCLID Ch. 5.2.3). The anaerobic half-life DegT50 was calculated to be 187.8 days for the loamy sand soil (re-calculated with DFOP model at 20 °C, Sachers, 2016, see IUCLID Ch. 5.2.3). Considering the geometric mean DegT50 of 233 days epoxiconazole fulfils the criteria for both P and vP in soil.

However, ECHA Guidance on information requirements and chemical safety assessment (v3.0, June 2017), Chapter R.11.4.1 says that “for the purpose of quantitative risk assessment and for adsorptive substances, a simulation test in soil (OECD TG 307) could be more relevant than a simulation test in sediment (OECD TG 308)”.

Therefore, based on the available experimental readily biodegradation data and the degradation kinetic data for the compartment soil and considering the high Koc value of epoxiconazole, it can be concluded that epoxiconazole meets the criteria for classification as persistance (P) or very persistance (vP).

However, the substance is not B/vB based on the available log Kow value of 3.3. (BASF SE, OECD 107, pH 7, 2008). Additionally, experimental data are available for epoxiconazole. A GLP study conducted according to the EPA OPP 165-4 (Laboratory Studies of Pesticide Accumulation in Fish) was performed with O. mykiss as a test organism. Bioconcentration factors were: 70 and 59 L/kg for both dose levels (in whole fish, Baranowski, 1990).

The substance fulfills the criterion for "T" since the lowest available chronic value is < 0.01 mg/L.

 

PBT / vPvB – Assessment for metabolites of epoxiconazole:

ECHA Guidance on information requirements and chemical safety assessment (v3.0, June 2017), Chapter R.11.4.1 specifies that “a PBT/vPvB assessment is required for all transformation products detected at ≥ 10% of the applied radioactivity in the total water-sediment system at any sampling time. Transformation products for which concentrations are continuously increasing during the study should also be considered for identification, even if their concentrations do not exceed the limits given above, as this may indicate persistence”.

One metabolite was identified for the parent compound as relevant degradation products under anaerobic and anaerobic test conditions in terms of PBT/vPvB assessment

Within the sediment, epoxiconazole is metabolized to BF 480 entriazole to a high extent and the metabolite reached more than 30% of the applied radioactivity (Schnoeder, rep. no.: 1001015, OECD 308 (draft), 2003) This result is in agreement with the results from the anaerobic soil metabolism study, where the metabolite was also detected in significant amounts (BASF AG, rep. no.: 58246, 2003).

Additionally, the metabolite 1,2,4-triazole could be identified by chromatographic comparison and accounted for 6.6% TAR in a study conducted according to EPA 163-1 (Leaching test) with epoxiconazole (BASF AG, rep. no.: 1991/10286, 1991). Although 1,2,4-triazole was identified only as a minor metabolite during aerobic soil metabolism of epoxiconazole, this metabolite is also considered as a relevant degradation product in terms of the PBT / vPvB Assessment of epoxiconazole.

 

Persistence (“P/vP”):

The degradation kinetics of the metabolite BF 480 entriazole was re-evaluated based on the latest guidance document of the FOCUS workgroup on degradation kinetics in aerobic conditions of water/sediment test system and anaerobic conditions in soil. Considering anaerobic degradation test conditions in soil, no reliable degradation endpoints for the metabolite BF 480-entriazole could be derived as no acceptable fit was obtained.

In both water/sediment test systems, BF 480-entriazole was observed in relevant amounts in the sediment phase only. In system Swiss Lake, no adequate number of data points was available for the dissipation phase. For the system Millstream Pond, reliable trigger and modeling endpoints were derived. The results are summarized in the Table below.

Table 1. Summary of trigger endpoints (DT50, d) for metabolite BF 480-entriazole.

	Sediment phase, SFO kinetic model
	Trigger endpoints	Modeling Endpoints
Swiss Lake	n.d.	n.d.
Millstream Pond	46.6	46.6

n.d. not acceptable fit was obtained

The trigger and the corresponding modelling DegT50 were 46.6 days.

The metabolite 1,2,4-triazole degraded in laboratory soil experiments with single first order DT50 of 6-12 days (20ºC and 40% MWHC, 3 different soils). The geometric mean of the values normalised to 20ºC and pF2 soil moisture content resulted in a first order DT50 of 8 days.

Therefore, it can be concluded that both relevant degradation products of epoxiconazole are not fulfilling the criteria for persistence (P/vP) in sediment according to REACH Annex XIII.

Bioaccumulation (“B/vB”):

No experimental data are available for both substances. Therefore, the estimation model KOWWIN v1.68 (EPI Suite v4.11) predicted the log Kow being 4.9 for BF 480 -entriazole and -0.76 for 1,2,4 -triazole (for details see ‘Attached document/report’ in IUCLID, Ch. 13.2).

Based on the estimation data available for the modelled metabolites:

1. BF 480 -entriazole is considered in a worst-case as potentially bioaccumulate (potentially “B”) and potentially very bioaccumulate (potentially “vB”), in absence of any other data as the screening-criteria for persistence are fulfilled. “B” and “vB”.

2. The relevant metabolite 1,2,4 -triazole is not considered as ‘’B’’ or ‘’vB’’, according to screening criterion for bioaccumulation (B/vB). 

Toxicity (“T”):

As the predicted degradation products are not likely to fulfill at the same time both the P/vP and B/vB criteria, no information was collected on their toxicity properties.

Overall conclusion:

1.  Sufficient data are available to assess the PBT/vPvB properties of the substance.

2.  Two potentially relevant degradation products were identified in aerobic water/sediment and anaerobic soil conditions:

2a. Based on available experimental and estimated data. it can be considered that relevant degradation products present do neither fulfill the PBT criteria (not PBT) nor the vPvB criteria (not vPvB).

2b. However, the predicted relevant metabolite BF 480 -entriazole should be considered as potentially B/vB from a precautionary point of view.