1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

Endpoint summary

Description of key information

Pencycuron is considered not to be readily biodegradable as 42.5 % of pencycuron was degraded during 28 days in a test solution inoculated with domestic sewage plant effluent. 

The half life in freshwater (and in sediment) is based on the total system value from two water/sediment systems of 139 days and 82.6 days at 22°C for Ijzendoom and Lienden. When converted to 12°C these values are 354 and 210 days (average value of 282 days).

The soil half life (based on eight soils) is a median value of 192 days. The normalised modelling DT50 values for the eight soils were converted to 12°C to give the following DT50 values (in days at 12°C), 295 (Nisse), 329 (Howe), 251 (Hofchen), 372 (Laacherhof), 114 (Laacherhof AXXa), 134 (Dollendorf II), 90 (Laacherhof AIIIa) and 133 (Hoffchen). 

All DT50 values were calculated following FOCUS guidance.

 

Test Type	Result	Assessment	Reference
Ready biodegradation IBAMA/ Oxygen consumption	Not readily bioodegradable (42.5% after 28 days)	Key study	Unspecified (1998)
OECD 308 Water/sediment study	Mineralisation to CO2 measured as 11.5 - 21.7 % AR in the aerobic water sediment study	Supporting study	Scholz and Freymiller (1986)
Aerobic soil degradation study to SETAC 1995 using 4 soils	Normalised SFO DT50 values of pencycuron for modelling  were 118-175 days (at 20°C). Non-SFO modelling gave persistence DT50 values of pencycuron in 4 soils of 99.1-188 days (at 20°C).	Supporting study, the DT50 values were recalculated in the DAR	Hellpointner (1998)
Aerobic soil degradation study to BBA guidelines.	No reliable DT50 was obtained for pencycuron. The report was finalised in 2003, whilst the experimental phase was conducted in 1993.	Acceptable study- but no DT50 obtained for pencycuron	Hellpointner  (2003a)
Aerobic soil degradation study to SETAC and BBA guidelines.	No reliable DT50 was obtained for pencycuron.	Acceptable study- but no DT50 obtained for pencycuron	Hellpointner (1998)
Aerobic soil degradation study following OECD 307 (2002) and SETAC guidelines using 4 soils and  2 radiolabels.	Normalised SFO DT50 values of pencycuron for modelling obtained were 42.5-63.3 days (at 20°C). Non-SFO modelling gave persistence DT50 values of pencycuron in 4 soils of 36.4-60.1 days (at 20°C).	Key study using 4 soils and 2 radiolabels	Heinemann (2008b)
Kinetic assessment of aerobic laboratory soil degradation carried out in line with Focus guidelines	DT50 (days): Pencycuron: Geometric mean: 89.2. Median: 90.7 (both at 20°C);  Values were recalculated in the DAR	Key study	Hammel (2009)
Field dissipation study carried out to BBA Guidelines at 4 sites in Germany.	Persistence DT50 endpoints of 35.9 to 68.2 days	Valid field study in DAR	Pogany (1986)
Field dissipation study carried out in France and Italy.	Persistence DT50 endpoints of 31.7 to 43.7 days	Valid field study in DAR	Sommer (2000)
Field dissipation study at sites in Germany (2), France and GB.	Persistence DT50 endpoints of 10.6 to 64.9 days	Valid field study in DAR	Sommer D and Schramel O (2000)
Modelling results from field studies	Modelling geomean of 35.9 days (and median of 38.3 days) obtained from n=10 normalised data	Valid kinetic assessment of field studies	Hammel & Kahl (2009)
Anaerobic water/sediment study to EPA guidelines	DT50 of 211.5 days at 20°C. Not considered relevant for EU submission.	Not required for EU submission	Hellpointner (2003)
Aerobic water/sediment study guidelines were not specified	No result, the sediment % in the study was above recommendations (at 27%)	Not accepted in the DAR (too much sediment at 27%)	Leslie and Close (1985)
Aerobic water/sediment study guidelines were not specified	The  geomean DT50 value of Pencycuron in the total water/sediment system was 107.2  days (at 22°C).	Key study	Scholz and Freymiller (1986)
Kinetic assesment of water/sediment degradation carried out in line with Focus guidelines.	Total system DT50 values 82.6 and 139 days were calculated at 22°C.	Key study	Hammel & Kahl  (2009)

Persistency Assessment

As pencycuron is not readily biodegradable (42.5% degradation in an IBAMA oxygen consumption study) persistence (P) cannot automatically be discounted.

An OECD 309 study is not available, thus, the assessment of persistence (P/vP) for the freshwater and sediment compartments is made based on the key OECD 308 aerobic water/sediment study.

The DT₅₀ values quoted in the study (taken from the crop protection dossier and DAR) do not take the non-extractable residues (NER) values of 23.9 to 29.5 % AR at the study end into account, so cannot be directly compared to the P and vP criteria. Following the ECHA guidance R.11 (ECHA, 2017) and assuming that NER is unreacted parent compound will increase any DT₅₀ value already calculated for parent compound.

However, the FOCUS calculated DT₅₀ values for the total system are already 82.6 and 139 days at 22^oC. If the mean of these two values is converted to 12^oC this gives a DT₅₀ value of 282 days.

This value is greater than the P-trigger of > 40 days or the vP-trigger of > 60 days in freshwater and above the trigger values > 120 days (P) or > 180 days (vP) for freshwater sediment (before NER is taken into consideration). So pencycuron must be considered as vP in water/sediment systems.

Persistence DT₅₀ values in soil are available from the DAR for pencycuron and metabolites- but these values do not take NER into account. From the two laboratory studies a modelling DT₅₀ value of 90.7 (median value) at 20^oC is calculated for pencycuron. Conversion of this value to 12^oC gives a value of 192 days which is already above the trigger values > 120 days (P) or > 180 days (vP) for soil (before NER is taken into consideration).

The soil metabolites pencycuron-PB-amine and pencycuron-ketone have DT₅₀ values at 20^oC of 38.6 and 87.4 days, (81.9 and 186 days, respectively, at 12^oC) also tiggering vP.

Pencycuron must be considered as P and vP in accordance with the criteria set out in REACH Annex XIII.