3,3',3'',5,5',5''-hexa-tert-butyl-α,α',α''-(mesitylene-2,4,6-triyl)tri-p-cresol

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

The substance is not readily biodegradable achieving 6% in 28 days. Due to high water insolubility (<0.00809 mg/L), it is not possible to assess the potential for hydrolysis by testing. The substance is, however a stable organic molecule and is therefore, considered by assessment of structure and experience in use to not hydrolyse in the environment.

The substance is considered to be very persistent in the environment were exposure to occur based on the known lack of biodegradability.

The bioconcentration factor (BCF) has been calculated as 3.162 L/kg wet-wt. using QSAR estimation based upon the SMILES code of the molecular structure Arnot-Gobas BCF & BAF Methods by structural fragmentation of the EPI Suite v4.1.

 

The partition coefficient of the substance has been calculated using QSAR estimation based upon the SMILES code of the molecular structure US EPA KOWWIN v1.68 of the EPI Suite v4.1. Based upon structural fragmentation drawn from a database of >40,000 substance, the log Pow is estimated to be 17.17. The extremely high log Pow is likely to be due in part to the hydrophobic nature of the molecule.

The potential bioaccumulation factor has also been assessed by QSAR using three models, EPI Suite, Catalogic and T. E. S. T. These data all predict BCF values that are non bioaccumlative.

Furthermore, assessment of the Toxicokinetic activity of the substance conducted with a radioisotope demonstrates that 28% was located in the GI tract with the total remaining mass balance (71%) excreted in faeces.

Finally the molecular weight and structural steric hindrances of the molecule would significantly restrict the ability of the substance to pass through cell membranes.

Based on these data the substance is considered to be non-bioaccumulating.

Eco-toxicity studies:

Due to the substance being highly insoluble in water exposure to three aquatic species (algae, daphnia and fish) have been investigated at nominal concentrations. The toxicological examination on daphnia and algae provided an EC50 >100 mg/L and the results on a close structural analogue on fish produced an LC50 >100 mg/L.

Mammalian toxicity studies:

The substance has been assessed for genetic toxicity by four in vitro assays, two performed on a close structural analogue, with and without metabolic activation, all studies demonstrated a lack of mutagenic response.

The Prenatal Developmental Toxicity, on a close structural analogue, produced a NOAEL >1000 mg/kg bw/day.

The three generation reproduction study resulted in a NOAEL >5000 ppm.

The data from the 2 year feeding study achieved a NOEL 10,000 ppm. 

Considering the toxicological information the substance is not toxic.

The substance may pose a persistence (P) hazard but as the results produced no bioaccumulation (B) or toxicity (T) properties the substance cannot be considered as a PBT/vPvBT.

Likely routes of exposure:

The substance is a powder of a particle size that is not breathable and is generally used in closed conditions.

 

The likely route of exposure to workers would be by dermal exposure.