[nitrilotris(methylene)]trisphosphonic acid, ammonium salt

Biodegradation in soil

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The study was well documented and meets generally accepted scientific principles, but was not conducted in compliance with GLP.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Soil CO2 evolution test. Degradation chamber consisted of modified 60 ml Buchner-type funnel. 20g soil in each of 12 funnels. Test substance added as aqueous solution to give 10µg/g.

GLP compliance:

no

Test type:

laboratory

Radiolabelling:

yes

Soil no.:

#1

Soil type:

other: Iowa Farm Soil

% Org. C:

3.31

pH:

5.6

Soil no.:

#2

Soil type:

other: Olivette Garden Soil

% Org. C:

3.03

pH:

7.65

Soil no.:

#3

Soil type:

other: St. Charles Ray-Silt Loam

% Org. C:

0.56

pH:

7.05

Soil no.:

#4

Soil type:

other: Meramec River Bank Soil

% Org. C:

0.7

pH:

7.7

Details on soil characteristics:

SOIL COLLECTION AND STORAGE

- Storage conditions: sealed polyethylene bags

- Soil preparation (e.g., 2 mm sieved; air dried etc.): 2 mm sieved

PROPERTIES OF THE SOILS (in addition to defined fields)
- Water content (gH2O/gsoil dwt): 0.20; 0.23; 0.14; 0.06

- Water-holding capacity (gH2O/gsoil dwt): 0.50; 0.45; 0.45; 0.39

Duration:

119 d

Initial conc.:

10 mg/kg soil d.w.

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Soil No.:

#1

% Degr.:

7.11

Parameter:

CO2 evolution

Sampling time:

119 d

Soil No.:

#2

% Degr.:

9.31

Parameter:

CO2 evolution

Sampling time:

119 d

Soil No.:

#3

% Degr.:

14.16

Parameter:

CO2 evolution

Sampling time:

119 d

Soil No.:

#4

% Degr.:

14.64

Parameter:

CO2 evolution

Sampling time:

119 d

Transformation products:

not measured

Details on results:

Sterilised (sodium azide) soil degradation: Olivette Garden Soil 0.82% 199d; St. Charles Ray-Silt Loam Soil 0.63% 199d.

Though degradation levels were low, breakdown in the soil environment does occur.

Conclusions:

Soil biodegradation of between 7 and 15% over 119 d in four soils was determined in a reliable study conducted according to generally accepted scientific principles.

Reference 2

Endpoint:

biodegradation in soil: simulation testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study well documented, meets generally accepted scientific principles, acceptable for assessment.

Principles of method if other than guideline:

Degradation units, each containing 20 g (dry-weight) soil, spiked with either test or reference substance, sparged with CO2-free air and the off-gas passed through CO2 absorbent scrubbers. The ¹⁴C evolved measured by liquid scintillation counting.

GLP compliance:

no

Test type:

laboratory

Radiolabelling:

yes

Oxygen conditions:

aerobic

Soil classification:

not specified

Details on soil characteristics:

SOIL CHARACTERISTICS: Source: St. Charles Ray-Silt Loam pH: 7.05 % organic carbon: 0.56 Water content: 0.14 g/g (dry-weight basis) Water Holding Capacity: 0.45 g/g

Parameter followed for biodegradation estimation:

radiochem. meas.

Details on experimental conditions:

TEST DETAILS: St. Charles ray-silt loam - was seived through a 2 mm screen and the water content adjusted with either distilled water or a dilute sodium azide solution (to approximate a sterile control). Degradation units, each containing 20 g (dry-weight) soil, were spiked with either test substance or linear dodecylbenzene sulfonate (LAS) at a nominal level of 10 µg/g (for test substance, as active acid). Each soil unit was sparged with CO2-free air and the off-gas passed through two scrubbers each containing 5 ml of the CO2 absorbent (monoethanolamine-ethylene glycol) monoethyl ether 1:7 (v/v) solution. Periodically, the first scrubber was removed, the second scrubber moved to position one and replaced with a fresh scrubber. The C-14 evolved was then measured by liquid scintillation counting using a Mark III Liquid Scintillation Spectrometer (Model 6880, Searle Analytic, Inc.). The percent C-14 evolved was calculated from the disintegrations per minute and the initial C-14 charged to each unit.

Key result

Soil No.:

#1

% Degr.:

14

Parameter:

radiochem. meas.

Remarks:

(¹⁴CO2 generation)

Sampling time:

148 d

Transformation products:

not measured

Evaporation of parent compound:

not measured

Volatile metabolites:

no

Residues:

not measured

Table 1: Percent degradation values (C-14 CO2 evolved, % theory)

Type of suspension	% degradation at sampling time (days)
	2	6	12	16	21	28	35	43	58	72	86	100	114	128	148
Reference substance (LAS) Microbial	0.03	0.14	2.20	4.53	7.69	11.46	15.68	20.49	29.44	36.34	41.92	46.59	50.41	53.60	56.97
Reference substance (LAS) Sterile	0	0.02	0.05	0.05	0.05	0.07	0.07	0.07	0.07	0.08	0.08	0.08	0.08	0.08	0.10
Test sample Microbial	1.87	2.98	4.07	4.74	5.40	6.16	6.86	7.61	8.86	9.89	10.82	11.69	12.48	13.22	14.18
Test sample      Sterile	0.16	0.21	0.24	0.24	0.24	0.24	0.24	0.24	0.26	0.27	0.27	0.27	0.27	0.27	0.28

 

The data suggest that no induction period is required before degradation occurs.

Conclusions:

Soil biodegradation of 14% over 148d in a silt loam soil was determined in a reliable study conducted according to generally accepted scientific principles.

Reference 3

Endpoint:

biodegradation in soil: simulation testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

weight of evidence

Justification for type of information:

Please refer to Annex 3 of the CSR and IUCLID Section 13 for justification of read-across within the ATMP category.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Soil No.:

#1

% Degr.:

14

Parameter:

radiochem. meas.

Remarks:

14CO2 generation

Sampling time:

148 d

Remarks on result:

other: Saeger (1978)

% Degr.:

7.11 - 14.64

Parameter:

CO2 evolution

Sampling time:

119 d

Remarks on result:

other: Saeger (1977)

Remarks:

Four different soils

Transformation products:

not measured

Description of key information

Two reliable studies are available for ATMP-H. Biodegradation of 14% over 148 days in a silt loam soil was determined (Saeger, 1978). In a separate study, biodegradation of between 7 and 15% over 119 days in four soils was determined (Saeger, 1977).

 

Although biodegradation in soil has not been demonstrated for ATMP-H and its salts, the role of abiotic removal processes is significant. The key data for soil adsorption are from the study by Michael (1979; refer to IUCLID Section 5.4.1). There is no evidence for desorption occurring. Effectively irreversible binding is entirely consistent with the known behaviour of complexation and binding within crystal lattices. The high levels of adsorption which occur are therefore a form of removal from the environment. For analogous phosphonate complexing agents, after 38-50 days, the phosphonate is >95% bound to sediment with only 5% extractable by ultrasonication and use of 0.25N HCl xylene solvent (based on radiolabelling) in river microcosms (cited in Gledhill and Feijtel, 1992). In the same study, ATMP-H rapidly, and to a high degree was irreversibly removed from a natural water column. (Saeger, 1979, see IUCLID sections 5.2.2 and 5.4.1). In the context of the exposure assessment, largely irreversible binding is interpreted as a removal process; 5% remaining after 40 - 50 days is equivalent to a half-life of 10 days which is significant for the environmental exposure assessment in the regional and continental scales. This abiotic removal rate is used in the chemical safety assessment of ATMP-H and its salts.

Key value for chemical safety assessment

Half-life in soil:

10 d

at the temperature of:

12 °C

Additional information

Some biological degradation in soil takes place, as demonstrated by the higher level of removal of ATMP-H in active soils (14% removal in 148 days compared to up to <1% removal in sterile control soil) (Saeger, 1978).

 

7.11-14.64% degradation of ATMP-H was observed in soils after 119 days, based on CO2 evolution (Saeger, 1977).

There are degradation modes operative in the environment which could prevent long-term persistence.

A supporting study conducted with ATMP-H recorded 2-53% degradation after 10 weeks, based on radiochemical measurement. Documentation was insufficient for assessment and the study has been assigned Reliability 4 (Steber and Wierich, 1987).

The ammonium ion upon release into the environment would enter natural nitrogen cycles in air, soil and water.

The acid, sodium, potassium and ammonium salts in the ATMP category are freely soluble in water. The ATMP anion can be considered fully dissociated from its sodium, potassium or ammonium cations when in dilute solution. Under any given conditions, the degree of ionisation of the ATMP species is determined by the pH of the solution. At a specific pH, the degree of ionisation is the same regardless of whether the starting material was ATMP-H, ATMP.4Na, ATMP.7K or another salt of ATMP.

 

Therefore, when a salt of ATMP is introduced into test media or the environment, the following is present (separately):

1. ATMP is present as ATMP-H or one of its ionised forms. The degree of ionisation depends upon the pH of the media and not whether ATMP (3-5K) salt, ATMP (3-5Na) salt, ATMP-H (acid form), or another salt was used for dosing.
2. Disassociated potassium, sodium or ammonium cations. The amount of potassium or sodium present depends on which salt was dosed.
3. It should also be noted that divalent and trivalent cations would preferentially replace the sodium or potassium ions. These would include calcium (Ca²⁺), magnesium (Mg²⁺) and iron (Fe³⁺). These cations are more strongly bound by ATMP than potassium, sodium and ammonium. This could result in ATMP-dication (e.g. ATMP-Ca, ATMP-Mg) and ATMP-trication (e.g. ATMP-Fe) complexes being present in solution.

In this context, for the purpose of this assessment, read-across of data within the ATMP Category is considered to be valid.