Potassium salts of [hexane-1,6-diylbis[nitrilobis(methylene)]]tetrakisphosphonic acid (4-7 K:1)

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-03-28 to 2002-04-25

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to a test protocol that is comparable to the appropriate OECD test guideline, and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

other: Test Method Relating to New Chemical Substances (1974, amended 1998)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 305 (Bioconcentration: Flow-through Fish Test)

GLP compliance:

yes

Details on sampling:

- Sampling intervals/frequency for test organisms: 4, 7, 14, 21, and 28 days

- Sampling intervals/frequency for test medium samples:0, 4, 7, 14, 21, and 28 days

- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods):
- Four fish were taken from each concentration level and analysed two by two. Two fish are weighed, cut into pieces, and homogenised to a slurry. 15ml Acetonitrile, 5ml purified water and 0.2 ml of triethylamine were added to 1g of slurry. The solution was homogenised, centrifuged and the top layer collected and diluted to 50ml and then further diluted 20-fold with purified water. The solution was analysed by HPLC.
- The test media at high concentration was diluted ten-fold with purified water, then analysed by HPLC. The test media at low concentration was directly analysed by HPLC.

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Test substance dissolved in 2000ml purified water (High concentration level feed: 40000mg/l, low concentration feed: 4000mg/l). Each of feed solutions was supplied to a mixing glass tube by a metering pump, and diluted to their respective nominal concentrations by mixing with dilutionwater delivered by another type of metering pump, then poured into each test chamber.

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM
- Common name: Carp

- Source: Sankyo Suisan Co., 1-1, Ichigayatamachi, Shinjuku-ku, Tokyo, Japan, Lot #: 01-K-1112

- Age at study initiation (mean and range, SD): Less than a year after hatching

- Length at study initiation (length definition, mean, range and SD): 8±4 cm

- Weight at study initiation (mean and range, SD): About 5 g

- Health status: Preacclimation: When the lot of fish was received, visual observation was made and abnormal fish were removed. The remaining fish were then reared in an aquarium with water flowing through. During the acclimation period, fish were kept without receiving medicine in the aquarium.

- Description of housing/holding area: aquarium

- Feeding during test: 200ml/day

ACCLIMATION

- Acclimation period: ≥2 weeks

- Type and amount of food: Babygold® from Kyorin, The food was given in an amount of 2% of the fish weight.

- Health during acclimation (any mortality observed): Mortality during the 1 week before testing: (5%

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

28 d

Test temperature:

24±2°C

pH:

6.0-8.5

Dissolved oxygen:

260% of the saturation (25 mg/L at 240C)

Details on test conditions:

TEST MEDIUM / WATER PARAMETERS

- Intervals of test medium replacement: feed solutions were renewed after about 8 days.

OTHER TEST CONDITIONS

- Light intensity: About 16 hr/day (Hf fluorescent lamp with wavelengths of 400-700 nm)

Type:

BCF

Value:

< 10 dimensionless

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:High concentration level (18.8mg/L)

Type:

BCF

Value:

< 94 dimensionless

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:Low concentration level (2.03mg/l)

Details on results:

- Mortality of test organisms: <10%

- Behavioural abnormalities: There was no abnormality in shape of the body or in swimming and feeding behaviour during the period of the test.

Table 1: Concentration of the test substance in the test fish and bioconcentration factor (BCF) - High concentration level

Exposure period		Fish weight (g)		Peak Area (mAbs.sec)		Conc. In final solution (mg/l)	Conc. In fish body (µg/g)	Mean conc. In water (mg/l)	BCF
Day	No.	1	2	Sample	std
4	1	4.64	8.79	<1500	19910	<0.151	<166	18.8	<9
4	2	6.94	4.84	<1500	19910	<0.151	<166	18.8	<9
7	1	4.70	6.44	<1500	19834	<0.151	<167	19.0	<9
7	2	7.49	7.41	<1500	19834	<0.151	<167	19.0	<9
14	1	6.27	5.61	<1500	17767	<0.169	<186	18.9	<10
14	2	6.82	6.40	<1500	17767	<0.169	<186	18.9	<10
21	1	5.59	6.27	<1500	17767	<0.169	<186	18.7	<10
21	2	8.74	5.87	<1500	17767	<0.169	<186	18.7	<10
28	1	6.44	5.56	<1500	17767	<0.169	<186	18.8	<10
28	2	6.46	6.75	<1500	17767	<0.169	<186	18.8	<10

Table 2: Concentration of the test substance in the test fish and bioconcentration factor (BCF) - Low concentration level

Exposure period		Fish weight (g)		Peak Area (mAbs.sec)		Conc. In final solution (mg/l)	Conc. In fish body (µg/g)	Mean conc. In water (mg/l)	BCF
Day	No.	1	2	Sample	std
4	1	9.89	4.26	<1500	19910	<0.151	<166	2.06	<81
4	2	8.16	5.76	<1500	19910	<0.151	<166	2.06	<81
7	1	10.47	5.19	<1500	19834	<0.151	<167	2.01	<83
7	2	9.18	6.50	<1500	19834	<0.151	<167	2.01	<83
14	1	10.66	4.45	<1500	17767	<0.169	<186	2.00	<93
14	2	6.00	6.56	<1500	17767	<0.169	<186	2.00	<93
21	1	4.47	7.21	<1500	17767	<0.169	<186	1.99	<94
21	2	5.84	6.35	<1500	17767	<0.169	<186	1.99	<94
28	1	7.55	5.46	<1500	17767	<0.169	<186	2.03	<92
28	2	6.40	5.00	<1500	17767	<0.169	<186	2.03	<92

Validity criteria fulfilled:

yes

Conclusions:

Bioconcentration factors of <10 (Concentration level 18.8mg/l) and <94 (concentration level 2.03 mg/l) were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

No study of bioaccumulation conducted with HMDTMP(4-7K) is available. Given the very low measured value of log Kow (-4), bioaccumulation is expected to be very low. A reliable study of bioaccumulation of an analogous substance, DTPMP-7Na in carp, indicates a bioconcentration factor in the exposure phase of <10 (Concentration level 18.8mg/l) and <94 (concentration level 2.03 mg/l).No active uptake mechanisms (i.e. mediated by enzymes) can occur for phosphonates.

Key value for chemical safety assessment

BCF (aquatic species):

94 dimensionless

Additional information

The registration endpoint is fulfilled by read-across from a structurally analogous substance, DTPMP(5 -7Na), which is part of the DTPMP category.

 

HMDTMP acid (CAS 23605-74-5) has two aminobismethylphosphonate groups, connected by a hexyl chain. DTPMP acid (CAS 15827-60-8) has three amine centres (five methylphosphonate groups), connected by ethyl chains.

 

As well as being structural analogues, both phosphonates have consistent chemical properties including high MW (492 and 573 respectively), very low log Kow(≤-3 for both substances) and are highly soluble in water. The substances generally possess similar physico-chemical properties and are not readily biodegradable.

 

The sodium and potassium counterions of these phosphonates are not significant in respect of the properties under consideration and have been assessed in depth in the public literature. Additionally, the counterions are expected to dissociate when in contact with water, including atmospheric moisture.

 

Therefore, for the purpose of this assessment, read-across is considered valid. Further information on the validity of read-across are presented in Annex 6 of the CSR and IUCLID Section 13.