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PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

Persistence (P, vP)


Biodegradation in water: screening test


In a study conducted according to OECD 301B, under GLP conditions, the test material attained 26% degradation after 28 days and therefore is not readily biodegradable.


Biodegradation in water and sediment


In an OECD 308 study, conducted according to GLP, the test material dissipated rapidly from the water of both aquatic sediment systems, with DT50 values of 2.6 days (Calwich Abbey Lake) and 10.4 days (Emperor Lake).  The DT50 value in the sediment phase of Calwich Abbey Lake was 811 days, based on two sampling intervals.  The DT50 value for the decline in the sediment phase of Emperor Lake could not be calculated, as the test material (as % applied parent) continued to increase until the last sampling interval.  Decline in the overall aquatic sediment system was slow and corresponded to DT50 values of 657 days (Calwich Abbey Lake) and 636 days (Emperor Lake).


Due to the low solubility of the test material and rapid partitioning from the aqueous phase to the sediment, aerobic mineralisation in surface water – simulation biodegradation testing according to OECD Testing Guideline No. 309 is considered technically not feasible.  


Biodegradation in soil


In an OECD 307 study, conducted according to GLP, the mean distribution and recovery of radioactivity ranged from 99.7 to 106.2% AR in Cuckney soil, 93.9 to 103.4% AR in Drayton soil, 97.6 to 107.2% AR in Elmton soil, and 95.2 to 106.2% AR in Calke soil.  Low levels of radioactivity were detected in the bound residues (mean values =10.6% applied radioactivity) and mean mineralization of the test item to CO2 was less than or equal to 0.9% applied radioactivity.  There was little or no evidence for degradation of test material in soil at 12 +/- 2 deg C and pF2, under aerobic conditions, and kinetic analysis of the data was therefore considered inappropriate.


Bioaccumulation (B, vB)


No experimental study on bioaccumulation is available on the registered substance. According REACH Annex IX column 2, the Bioaccumulation not need to be performed if the substance  has a low potential for bioaccumulation (for instance a log Kow ≤ 3) and/or a low potential to cross biological membranes.  In a study conducted according to TG OECD 117 (HPLC method) and GLP, the partition coefficient is log Pow greater than 6.5. Therefore considering the properties of the registered substance, it is not possible to waive the bioaccumulation study.


Based upon a weight of evidence approach considering the complex composition of the UVCB, the BCF has been predicted to be 381.4 L/kg wet-wt calculated on the worst case constituent (having the highest lipophilic potential - log Kow, predicted among the UBVC's constituents). Considering that the applicability domain of the QSAR is not fulfilled, a bioacumulation test on fish has been proposed according the TG OECD 305-III (for more details, please see the bioaccumulation Endpoint Study Record).


Toxic (T)


Aquatic chronic toxicity according to GLP and TG OECD 201, 211 and 210 demonstrate that no effects were observed up to NOEL > 100 mg/L (WAF) on three trophic levels (algae, daphnia and fish). Therefore, the registered substance does not meets the criteria for toxicity for freshwater or marine organisms (NOEC > 0,01 mg/L) according REACH annex XIII. 


In an OECD 471 study, the test material is non-mutagenic (negative) to Salmonella typhimurium and Escherichia coli bacterial strains.  In an OECD 471 study, OECD 473, and OECD 476 the structurally similar read across substance is non-mutagenic to Salmonella typhimurium bacterial cells, is non-clastogenic to human lymphocytes, is non-mutagenic to rat lymphocytes, and is non-mutagenic to mouse lymphoma.


Based on the results of an OECD 414, the maternal and embryo-fetal No-Observed-Adverse-Effect-Level (NOAEL) of the test item were considered to be 330 mg/kg/day.  The maternal NOAEL was considered to be 330 mg/kg/day based on the mortality and low body weight gains in rats receiving 1000 mg/kg/day; and the embryo-fetal NOAEL, although no effect on embryo-development was established, was considered to be 330 mg/kg/day - being dependent on maternal toxicity.


In a read-across study with a structurally similar substance, the 90 day repeated dose toxicity (oral route) NOAEL in rats is greater than or equal to 1,000 mg/kg bw/d.