Pentapotassium triphosphate

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
See read-across justification report under Section 13 ‘Assessment Reports’.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
In accordance with REACH Annex XI, Section 1.5, of Regulation (EC) No. 1907/2006 (REACH) the standard testing regime may be adapted in cases where a grouping or read-across approach has been applied.

The similarities may be based on:
(1) a common functional group
(2) the common precursors and/or the likelihood of common breakdown products via physical or biological processes, which result in structurally similar chemicals; or
(3) a constant pattern in the changing of the potency of the properties across the category

1. Both substances are inorganic salts of a monovalent cation from Group 1A of the periodic table, and triphosphoric acid. Thus, they share the Na+ or K+ cation and P3O105- anion.
2. Both substances will ultimately dissociate into the common breakdown products of the Na+ or K+ cations and the P3O105- anion, resulting in further breakdown products of pyrophosphate and orthophosphate anions.
3. Sodium and potassium cations are ubiquitous in natural waters and are considered to possess similar toxicological and ecotoxicological profiles due in part to their similar behaviour and their existence as essential micronutrients. The triphosphate anion in both substances will breakdown in the environment via the processes of hydrolysis, biotic degradation and assimilation by organisms in the environment, resulting in the breakdown products of pyrophosphate and orthophosphate anions. Ultimately, pyrophosphate anions will also breakdown to orthophosphate. It is therefore considered to be scientifically unjustified to conduct further testing on pentapotassium triphosphate as the read across can be adequately justified.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across justification report under Section 13 ‘Assessment Reports’.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across justification report under Section 13 ‘Assessment Reports’.

4. DATA MATRIX
See read-across justification report under Section 13 ‘Assessment Reports’.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

other: TSCA guideline: 40 CFR 797.1930

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

not specified

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Source: Stock culture maintained at testing laboratory
- Age at study initiation: <24 h old

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

186 mg/L (as calcium carbonate)

Test temperature:

20 - 21 C

pH:

8.0 - 8.3

Dissolved oxygen:

8.3 - 9.7 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentration of 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Cylindrical glass exposure chambers (100mm diameter x 50 mm height). 250 ml fill volume.
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Well water located at test facility, passed through a mixed bed deionization resin and then reconstituted with sodium bicarbonate, calcium sulfate, magnesium sulfate and potassium chloride.
- Pesticides: Organochlorine & PCBs (< 0.006 µg/L); Organophosphate (< 0.088 µg/L)
- Alkalinity: 119 mg/L as calcium carbonate
- Conductivity (µmhos/cm): 370

OTHER TEST CONDITIONS
- Photoperiod: 16 h light and 8 hour dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Observed daily for immobilization (upon prodding) and any behavioural changes


TEST CONCENTRATIONS
- Range finding study conducted at a test concentration of 1000 mg/L (results used to determine the conditions for the definitive study)
-Definitive study conducted at a test concentration of 100 mg/L

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Reported statistics and error estimates:

Statistical analysis (t-test) of data indicated there was no significant (alpha = 0.05) difference between the number of daphnids immobilized in control and treatment exposures.

Table 1: Immobilization of Daphnia magna exposed to sodium tripolyphosphate in a 48 h static acute toxicity test

Nominal concentration (mg/L) of tripolyphosphate^a	Cumulative number of immobilized organisms and corresponding percent (parenthetic value)
	24 h	48 h
0 (control)	0 (0)	0 (0)
100	0 (0)	1 (3)

^aCalculated based on 100% purity of the test substance

Validity criteria fulfilled:

yes

Conclusions:

LC50 = >100 mg/L
After 48 hours the LC50 of sodium tripolyphosphate to (freshwater) Daphnia manga was found to be >100 mg/L.

Read across from pentasodium triphosphate to pentapotassium triphosphate is justified on the following basis:
Both substances are inorganic compounds containing a triphosphate anion and a group 1 alkali metal cation. Both sodium and potassium cations are ubiquitous in natural waters and are considered to possess similar toxicological and ecotoxicological profiles due in part to their similar behaviour and their existence as essential micronutrients. The triphosphate anion in both substances will breakdown in the environment via the processes of hydrolysis, biotic degradation and assimilation by organisms in the environment, resulting in the breakdown products of pyrophosphate and orthophosphate anions. Ultimately, pyrophosphate anions will also breakdown to orthophosphate.
It is therefore considered to be scientifically unjustified to conduct further testing on pentapotassium triphosphate as the read across can be adequately justified


Read-across is justified on the basis detailed in rationale for reliability above. This study is therefore considered to be of sufficient adequacy and reliability to be used as a key study for the derivation of the PNECaqua marine. No further testing is justified.

Description of key information

Six studies on aquatic invertebrates are available. Three of which are considered reliable. Although the study by Vaishnav et al (1991) only used one test concentration, results from this study gave the most conservative result and this is therefore considered the key study. 
Statistical analysis (t-test) of data indicated there was no significant (alpha = 0.05) difference between the number of daphnids immobilized in control and treatment exposures. The study was conducted on the analogous material pentasodium triphosphate (sodium tripolyphosphate).

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

100 mg/L

Additional information

The two studies performed by Pandard on the analogous substance sodium tripolpyhosphate (pentasodium triphosphate) exhibited precipitation in the test media throughout the duration of the test. This precipitation is deemed to have interfered with the test organisms and the results are therefore considered unreliable. These tests (Pandard) will not be considered beyond this section of the dossier and are only included for completeness.

Read across from pentasodium triphosphate to pentapotassium triphosphate is justified on the following basis:

Both substances are inorganic compounds containing a triphosphate anion and a group 1 alkali metal cation. Both sodium and potassium cations are ubiquitous in natural waters and are considered to possess similar toxicological and ecotoxicological profiles due in part to their similar behaviour and their existence as essential micronutrients. The triphosphate anion in both substances will breakdown in the environment via the processes of hydrolysis, biotic degradation and assimilation by organisms in the environment, resulting in the breakdown products of pyrophosphate and orthophosphate anions. Ultimately, pyrophosphate anions will also breakdown to orthophosphate.

It is therefore considered to be scientifically unjustified to conduct further testing on pentapotassium triphosphate as the read across can be adequately justified.