Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Classification of Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts for effects in the environment:

 

The chemical Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts (CAS no. 67649-42-3) is used in as a corrosion inhibitor in lubricants. The aim was to assess whether the PBT criterion within Annex XIII was fulfilled for Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts. The PBT criterion was herein assessed based on experimental data in conjunction with standardized environmental fate models. Here follows a description of the PBT assessment.

 

 

Persistence assessment

The tested substance fulfils the P criterion within Annex XIII based on the assessment that here follows:

 

Biotic degradation

In a prediction done by SSS (2017) using OECD QSAR toolbox version 3.3 with log Kow as the primary descriptor, percentage biodegradability of test chemical Dialkyl(C1 -C14)dithio phosphoric acid, zinc salt(CAS No. 68649-42-3) was estimated. Test substance undergoes 18% degradation by BOD in 28 days. Thus, based on percentage degradation, the test chemical Dialkyl(C1-C14)dithiophosphoric acid, zinc salt was estimated to be not readily biodegradable in water.

 

In another prediction using the Estimation Programs Interface Suite (EPI suite, 2017), the biodegradation potential of the test compound Dialkyl(C1-C14)dithiophosphoric acid, zinc salt(CAS No. 68649-42-3) in the presence of mixed populations of environmental microorganisms was estimated. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that chemical Dialkyl(C1-C14)dithiophosphoric acid, zinc salt is expected to be not readily biodegradable.

 

Experimental results from the similar substances (CAS: 54261-67-5; 77-58-7 and 7173-51-5) also indicate that it is not readily biodegradable

 

Environmental fate

According to the fugacity model levels III, the most likely environmental fate for this test chemical is soil (i.e.estimated to 86.4%).Thehalf-life in soil (120 days in soil as estimated by EPI suite) indicates that the chemical is not persistent in soil.

 

If released in to the environment, 13.5% and 0.00412% of the chemical will partition into water and sediment according to the Mackay fugacity model level III in EPI suite version 4.1 (2017). However, the half-life (60 days in water and 541.6 days in sediment as estimated by EPI suite) indicates that the substance is persistent in both the compartments.

 

Although the half-life values indicate the chemical to be Very persistent (vP), since only predicted data is available for the substance, it has been concluded that Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts is persistent in nature.

 

 

Bioaccumulation assessment

The tested substance fulfils the B criterion within Annex XIII based on the assessment that here follows:

 

Theoctanol water partition coefficient of the test chemical is 14.87 which is more than the threshold of 4.5. If this chemical is released into the aquatic environment, there should be a moderate to high risk for the chemical to bioaccumulate in fish and food chains.

 

Although the octanol water partition coefficient value indicate the chemical to be Very bioaccumulative (vB), since only predicted data is available for the substance, it has been concluded that Phosphorodithioic acid, O,O-di-C1-14-alkyl esters, zinc salts is bioaccumulative infish and food chains.

 

 

 

Toxicity assessment

The tested substance does not fulfil the T criterion within Annex XIII based on the assessment that here follows:

 

Mammals

The tested chemical is regarded to be not classified for carcinogenicity, mutagenicity and reprotoxicity, Further, there is no evidence of chronic toxicity, as identified by the classifications STOT (repeated exposure), category 1(oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) or category 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume).

 

Aquatic organisms

As per Column 2 (Annex VIII) of the REACH regulation, a study does not need to be conducted if there are mitigating factors indicating that aquatic toxicity is unlikely to occur for instance if the substance is highly insoluble in water. The test substance was determined to be highly insoluble in water (solubility= 0.000000000005072 mg/L). The chemical was therefore not considered as hazardous to aquatic environments as per the criteria set out in Annex XIII.

 

Conclusion

Based on critical, independent and collective evaluation of information summarized herein, the tested compound fulfil the P and B criterion but does not fulfil the T criterion and has therefore not been classified as a PBT compound within Annex XIII.