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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

Classification of Potassium hydrogen phthalate for effects in the environment:


Potassium hydrogen phthalate (CAS no. 877-24-7) is used in chemical synthesis and as a reagent for analysis. The aim of the PBT assessment was to evaluate whether this chemical fulfils the PBT criterion within Annex XIII. The PBT assessment were based on toxicological information in conjunction with standardized environmental fate- and bioaccumulation models. Here follows a description of the PBT assessment.



Persistence assessment

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


Biotic degradation

Biodegradation study was conducted for 30 days for evaluating the percentage biodegradability of test substance1,2-Benzenedicarboxylic acid, monopotassium salt. Glucose-glutamic acid mixture was used as a reference substance for the biodegradation study. The results are compared with the chemical oxygen demand (COD) of the test chemical, which measures its maximum oxygen combining power; the results are also compared with the BOD test performed on a standard glucose-glutamic acid reference solution used for BOD calibration.

Reference substance i.e.; glucose-glutamic acid mixture consumes 75 percent of its maximum oxygen requirement (COD) within 5 days and almost 100 percent in 30 days. Thus, based on this result, the reference substance is considered to be readily biodegradable. The percentage degradation of test substance was determined to be 92% by BOD parameter in 30 days. Thus, based on percentage degradation, test chemical1,2-Benzenedicarboxylic acid, monopotassium salt was considered to be readily biodegradable in nature.


Estimation Programs Interface Suite (EPI suite, 2017) was run to predict the biodegradation potential of the test compound 1,2-Benzenedicarboxylic acid, monopotassium salt (CAS no. 877 -24 -7) in the presence of mixed populations of environmental microorganisms. 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 1,2-Benzenedicarboxylic acid, monopotassium salt is expected to be readily biodegradable.


The data for the read across substances (CAS: 50-78-2 and 65-85-0) also indicates the substance to be 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 79.9%). In soil, Potassium hydrogen phthalate was expected to have moderate mobility based upon a Log KOC of 1.90. The half-life in soil (30 days estimated by EPI suite) indicates that the chemical is not persistent in soil and the exposure risk to soil dwelling animals is moderate to low.


If released in to the environment, 20 % of the chemical will partition into water, according to the Mackay fugacity model level III in EPI suite version 4.1 (2016). However, the half-life (15 days estimated by EPI suite) indicates that the exposure risk to aquatic animals is low.


Moreover, its persistent characteristic is only observed in the sediment compartment but Fugacity modelling shows that sediment is not an important environmental fate (less than 1% when estimated by EPI Suite version 4.1).


Hence it has been concluded that Potassium hydrogen phthalate is not persistent in nature


Bioaccumulation assessment

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


The BCF value is estimated as 3.162 L/kg wet wt. at 25ºC (EPI suite version 4.1, 2017) and the estimated octanol-water partition coefficient (Log Kow) is reported as -2.73. Hence, if this chemical is released into the aquatic environment, there should be a low risk for the chemical to bioaccumulate in fish and food chains.


Toxicity assessment

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



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

All of the available short-term eco-toxicity estimation for fish, invertebrates and algae for the substance indicates the LC50/EC50 value to be >100 mg/L. These value suggest that the substance is not likely to be hazardous to Aquatic organisms at environmentally relevant concentrations and cannot be classified as per the CLP regulation.

There are no available long-term toxicity evaluations for Potassium hydrogen phthalate. NOEC and LOEC values for the target substance in a 96 hour study on algae in salt water system are reported as 200 mg/L and 500-1000 mg/L respectively.

Further, NOEC values for the read-across substance Salicylic acid in a 72 hour study on algae is reported in the range 17 – 31 mg/L respectively.

By speculation, adverse effects at environmentally relevant concentrations in freshwater and saltwater species were not expected for Potassium hydrogen phthalate based on the data mentioned above.


Hence, classification for aquatic toxicity will not be applicable as per Annex XIII criteria for all of the tropic levels and the same is based on the above mentioned studies.



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