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Classification & Labelling & PBT assessment

PBT assessment

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PBT assessment: overall result

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

The PBT Assessment for NBPT (N-(n-Butyl)-thiophosphorictriamide) is based on the criteria set out in the "Guideline on information requirements and chemical safety assessment, Chapter R. 11: PBT Assessment" (ECHA 2008).

Persistence:

For NBPT a study on "ready degradability" according to EPA (OTS 796.3260 (Modified Sturm Test)) was conducted resulting in 9.51% degradation after 28 days based on CO2 evolution. As no further data is available, a final conclusion on the persistency of the substance cannot be reached. Thus, based on the screening data, the substance has to be considered to be persistent (P) or very persistent (vP).

Bioaccumulation:

NBPT has a log Kow of 0.444 (EU Method A.8). Thus, the test substance does not meet the screening criterion for bioaccumulation and is not considered to be bioaccumulative (B) or very bioaccumlative (vB).

Toxicity:

Long-term toxicity testing with algae (Pseudokirchneriella subcapitata) resulted in a NOEC of 75 mg/L for NBPT (OECD 201, EU Method C.3) and the test substance is not classified for environmental hazards according to Regulation (EC) No. 1272/2008 (2nd ATP) and Directive 67/548/EEC. However, according to Annex XIII of Regulation (EC) No 1907/2006, a substance is considered to fulfill the toxicity criterion (T), if the substance is classified as carcinogenic (category 1 or 2), mutagenic (category 1 or 2), or toxic for reproduction (category 1, 2 or 3), or if there is evidence of chronic toxicity, as identified by the classifications: T, R48, or Xn, R48 according to Directive 67/548/EEC. NBPT is classified as toxic for reproduction category 2 according to Regulation (EC) No 1907/2006 (Cat. 3 according to Directive 67/548/EEC) based on sperm motility evaluation and histopathology of epididymis and therefore meets the toxicity (T) criterion. Due to the results of the available genetic toxicity studies, NBPT is not considered to cause genetic damage. There is no data available for carcinogenicity and developmental toxicity. However, there is no evidence, that NBPT is carcinogenic by a direct genotoxic mechanism, as the results of all genetic toxicity studies were negative and there is no evidence for hyperplasia or preneoplastic lesions in the available subchronic study. In conclusion, NBPT is considered to be not toxic based on the available data for ecotoxicological endpoints but to be toxic based on the data for toxicological endpoints: toxicity to reproduction category 2 according to Regulation (EC) No 1907/2006 (Cat. 3 according to Directive 67/548/EEC). Therefore, the substance meets the toxicity criteria (T).