2-methyl-p-phenylenediamine

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Substance :

Persistence : Not P and not vP: The substance will exist primarily in the water compartment based on the test substance properties. The substance is not expected to hydrolyse or biodegrade readily based on QSAR and aqueous screening tests. Therefore, the substance is potentially persistent based on the biodegradation criteria. However, in water rapid abiotic decomposition of the substance occurs in river water (halflife is 12 hours at 12°C and 3.63 hours at 25°C). Rapid abiotic degradation in water is confirmed through aquatic toxicity testing in which it was observed a decrease of the measured test item concentrations.

Bioaccumulation: Not B and not vB: The measured log Kow is -0.321.

Toxicity: T: The test item is proposed to be classified as STOT Rep. Exp. 2. according to Regulation EC No 1272/2008 criteria.

Degradation products: Even if from the structure of the test item, hydrolysis is not to be expected, disappearance of 2,5-diaminotoluene was observed in a study conducted following OECD 111 guideline and GLP in sterile natural water at two different temperatures in the dark. The disappearance could be related to auto-oxidation processes. A few studies were conducted to elucidate the oxidative transformation of PTD. Most of the detected products are intermediates whose life times are highly variable and regulated by factors widely unknown. The semitoluquinone diimine radical cation (STQDIRC) is firstly formed. The radical has a lifetime of a few hours at neutral pH, but it reacts much faster at low and high pH. Subsequently, the toluquinone diimine (TQDI) is formed which attacks a PTD molecule to yield a dimeric product, not further characterized yet. Trimeric products including a Bandrowski Base (BB)-like structure originate from the reaction of dimeric intermediates with STQDIRC or TQDI. At environmentally relevant pH, it can be expected that the toluquinone diimine (TQDI) is formed which attacks a PTD molecule to yield a trimeric product. Toluquinone diimine and PTD-Bandrowski Base like structure were assessed as degradation products.

Persistence : P (and vP): As a conservative approach, the degradation products are considered to be persistent, based on QSARs results.

Bioaccumulation: Toluquinone diimine and PTD-Bandrowski Base like substance were not considered as B/vB based on QSARs, reliable predictions (LogP<4.5).

Toxicity: From acute ecotoxicity tests performed on aged 2,5-diaminotoluene solutions (thus containing degradation products), it was demonstrated that the formed degradation products were less toxic than the parent compound. No long term tests are available on degradation products.