Dipotassium 3,4,5,6-tetrabromophthalate

Short-term toxicity to fish

Administrative data

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

96 hours

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Justification for type of information:

EPA review document covering tetrabromophthalates; two fish studies presented
Substance in test was the anhydride, but this hydrolyses rapidly in water to the acid.
This is considered a valid substitute for read-across as the potassium salt will quickly dissociate; when diluted in solution, both the potassium salt and acid will combine with Calcium and Magnesium ions in natural water and form poorly soluble salts.

Cross-reference

Reason / purpose for cross-reference:

reference to other study

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

Performed by Lead Registrant in-house using calibrated equipment.
Information was generated to help support observations from environmental testing and to confirm suspected solublity under environmental and biological conditions.

Qualifier:

no guideline available

Principles of method if other than guideline:

The substance was disolved in two types of commercially available bottled water of known hardness, pH and analysis and concentrations up to 100 mg/l.
The substance was dissolved in molar HCl (ca pH1) at up to 100 mg/l
Precipitation of insoluble salts/acid was determined by use of a calibrated turbidity meter

GLP compliance:

no

Other quality assurance:

other: Use of calibrated instrumentation

Type of method:

flask method

Water solubility:

< 5 mg/L

Conc. based on:

other: estimation in considering presence of undisolved material

Loading of aqueous phase:

100 mg/L

Incubation duration:

ca. 1 h

Temp.:

20 °C

pH:

> 6.7 - < 7.4

Water solubility:

< 5 mg/L

Conc. based on:

other: estimation in considering presence of undisolved material

Loading of aqueous phase:

100 mg/L

Incubation duration:

ca. 1 h

Temp.:

20 °C

pH:

ca. 1

Details on results:

The measured pH for the mineral water was based on analysis provided by the suppliers.
The test substance did not impact on the pH.
The figure of 5 mg/l cited for solublity is based on report solublity for the acid form. Turbity was considered hardly detectable at < 10 mg/l

Conclusions:

The substance showed low solubiilty when diluted to below 100 mg/l in water typically used for ecotoxocity testing
The substance showed low solublity when diluted at pH 1 to mimic possible effects if ingested.
Acutal solubility was not possible to establish since it was in equilibrium

Executive summary:

Standard testing to EC A6 method demonstrated very high water solubility / miscibility with a slightly alkaline pH 9.9.

 

However, under dilute conditions in 'natural' water (as required for environmental toxicity testing), the substance proved to be poorly soluble with the apparent formation of calcium and other salts from the hardened test water. The apparent solubility decreased as concentrations were reduced. A solubility limit of ca 5 mg/l is reported in environmental toxicity testing for tetrabromophthalate salts.

 

It is likely that under these dilute conditions, the salt will exist in equilibrium and apparent solubility will depend greatly on actual hardness of the water and also the pH

 

Further work (Report, Dixon Chew, 19 March 2020) demonstrated precipitation under diluted conditions at pH 1 or in natural water (assessed by turbidity), thus confirming dissociation with formation of insoluble salts (natural water) and also formation of the poorly soluble acid form (pH 1, molar HCl). Although this work was non-quantitative in terms of determining actual solubility under these conditions, the observations demonstrated that the potassium salt will behave in the same way as the acid form under environmental and biological conditions.

 

These conclusions need to also be considered in the light of the well established observations that the anhydride quickly hydrates to the acid form under similar environmental conditions. Likewise, research has shown that the alkyl esters also hydrolyse to the acid form under environmental conditions. 

 

It must also be noted that the functionality of these substances is to provide the same propertied to different fabrics for fire retardant properties. The purpose of creating alkyl esters, or water soluble potassium salts is to allow use in different textile treatment media, but the functionality come from the C-O and C=O bonds of the phthalate to adhere to proteins and other charged groups in wool and other fibres. 

Data source

Reference

Reference Type:

review article or handbook

Title:

Tetrabromophthalic Anhydride [CASRN 632-79-1] Review of Toxicological Literature

Author:

National Institute of Environmental Health Sciences

Year:

1999

Bibliographic source:

National Institute of Environmental Health Sciences, USA

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

EPA OPPTS 850.1075 (Freshwater and Saltwater Fish Acute Toxicity Test)

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Tetrabromophthalic acid

Cas Number:

13810-83-8

Molecular formula:

C8H2Br4O4

IUPAC Name:

Tetrabromophthalic acid

Specific details on test material used for the study:

Substance in test was an alkyl ester, shown to react in light to quickly hydrolyse in water to the acid. The data relates to the acid form.
Bis(2-ethylhexyl) tetrabromophthalate, EC 247-426-5 hydrolysis shows rapid degradation to tetrabromophthalic acid ( Source: European Chemicals Agency, http://echa.europa.eu/)

This is considered a valid substitute for read-across as the potassium salt will quickly dissociate; when diluted in solution, both the potassium salt and acid will combine with Calcium and Magnesium ions in natural water and form poorly soluble salts.

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

no

Details on test solutions:

Tests to limit of solubility, ca 10 mg/l

Test organisms

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Study design

Test type:

static

Water media type:

freshwater

Total exposure duration:

96 h

Test conditions

Hardness:

Not specified in review document; claimed to be to guideline specification

Test temperature:

Not specified in review document; claimed to be to guideline specification

pH:

Not adjusted but not specified in review document; claimed to be to guideline specification

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Duration:

96 h

Dose descriptor:

LC0

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

The report solublity in water of the acid form (the anhydride converts to acid in water) is

Applicant's summary and conclusion

Validity criteria fulfilled:

not specified

Conclusions:

Substance in test was the anhydride, but this hydrolyses rapidly in water to the acid.
This is considered a valid substitute for read-across as the potassium salt will quickly dissociate; when diluted in solution, both the potassium salt and acid will combine with Calcium and Magnesium ions in natural water and form poorly soluble salts.