Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

PBT assessment

PBT assessment: overall result

Reference

Reference 1

Name:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Type of composition:

legal entity composition of the substance

State / form:

liquid

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference 2

Name:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Type of composition:

boundary composition of the substance

State / form:

liquid

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

Reference substance:

Phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts, neutral and basic

PBT status:

the substance is not PBT / vPvB

Justification:

The PBT Assessment for the substance is based on the criteria set out in the “Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment” (ECHA, 2014).

 

Persistency
One experimental study is available investigating the biodegradability of the substance. The study was performed according to EU Method C.6 (similar to OECD 301D). After 27 d the substance was degraded to < 5% indicating that the substance is not readily biodegradable according to the OECD criteria. Thus, the substance is considered to be potentially P/vP based on the available data.

Bioaccumulation
In accordance with ECHA Guidance R.11 (ECHA, 2017) the substance is not considered to meet the screening criterion for B assessment in aquatic species. Monomeric or dimeric neutral forms together with the basic form are presented in phosphorodithioic acid, O,O-di-dodecyl-esters, zinc salts. The log Pow of the neutral forms is with 3.4 below the trigger value of 4.5. With a molecular weight > 3000 it is unlikely that the basic form of the substance is bioavailable. Therefore the log Pow for the neutral form is used as key value for the chemical safety assessment.

However, according to ECHA Guidance R.11 (ECHA, 2017) there is indication that accumulation in air breathing organisms might occur based on the calculated log Koa of 8.37 (calculated with KOAWIN v.1.10 using the Henry's law constant of 0.0266 Pa m³/mol and the Log Pow of 3.4 as input parameters) in combination with the log Pow > 2. These screening values (Kow and Koa) referred to in the ECHA Guidance R.11 are a function of the modelled organisms, food webs and environments used to obtain these values. To develop this partition coefficient combination it was clearly indicated in the guidance that biomagnification potential is only assumed for substances with high chemical absorption efficiency from the diet, no biotransformation after absorption and negligible active transport (in or out).

The evaluation of the toxicokinetic behavior indicates that due to a high molecular weight (>=996.9 <=3072-09) absorption is expected to be low. However relatively low effects were observed in the oral acute toxicity test toward rats treated with the source substance which indicated either low amount of test material was absorbed, and/or the test material has low inherent toxicity. Due to the high molecular weight a dermal adsorption is predicted to be very low. Based on the very low vapor pressure, the volatility is low and hence, the potential for absorption via inhalation is considered to be negligible. Overall a systematic bioavailability of the target and source substances in humans is considered possible but limited after oral uptake of the substance due to their high molecular weights, which is also supported by the available acute and repeated dose toxicity data.

However, there is evidence for biotransformation and active transport of the substance after uptake. The potential metabolites following enzymatic metabolism were predicted using the QSAR OECD toolbox (v4.1, OECD, 2017). The QSAR tool predicts which metabolites may result from enzymatic activity in the liver and in the skin, and by intestinal bacteria in the gastrointestinal tract. 8 hepatic and 2 dermal metabolites were predicted for the target substance, respectively. The results of the OECD Toolbox prediction substantiate the information on metabolism known from general literature (Lehninger, 1993). Primarily, the formation of mono esters with phosphorothioic acid and the formation of dodecanol by hydrolysis of the parent substance are the predicted metabolites which may occur in the liver. In the skin, hydrolysis of the terminal methyl group of the aliphatic side chain was predicted. Besides the predicted liver and skin metabolites, up to 102 metabolites for the target substance and 34 metabolites for the source substance were predicted to result from all kinds of microbiological metabolism for the test substance. Most of the metabolites were found to be a consequence of the degradation of the molecule. The formation of CO2 as metabolite is also predicted, which will be excreted via exhaled air. For further details on the toxicokinetic behavior please refer to the toxicokinetic statement in IUCLID section 7.1.

Reliable QSAR models (BCFBAF Program v3.01) incorporated in the EPI Suite v4.1 interphase, were additional used to calculate the bioconcentration factors (BCF) of the substance. A BCF value of 81.34 L/ Kg wet-wet was predicted by the regression based model (Meylan, 1997) while a BCF of 0.5958 Bio Half-life (days) was estimated by the Arnot and Gobas model (2003) taking biotransformation into account these results show a low bioaccumulation potential of the substance and support the toxicocinetics outcome concerning a high rate of biotransformation after uptake. In conclusion, the trigger values for biomagnification in air-breathing (terrestrial) organisms as stipulated in the ECHA Guidance R.11 are likely to overestimate the potential for biomagnification in the food chain.

Even though absorption via oral exposure cannot be completely excluded the described metabolic and excretion pathways are likely to minimize biomagnification in the food chain.

Based on the information above it can be concluded that the substance is considered to be not B/vB based on the available data.

Toxicity
Available data on aquatic long-term toxicity are clearly ≥ 0.01 mg/L (NOELR (72 h): 220 mg/L). Moreover, the test substance is not classified for toxicity according to the criteria in Annex XIII of Regulation (EC) No 1907/2006 based on Regulation (EC) No 1272/2008. Thus, the criteria set out in Annex XIII of Regulation (EC) No 1907/2006 are not met and the test substance is not considered to meet the T criterion.

In conclusion, the substance is not PBT/vPvB.