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Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

In the natural environment the fate and behaviour of DTPMP-H and its salts are dominated by abiotic dissociation / complexing, irreversible adsorption to surfaces, and less by degradation processes. The most important properties are summarised in the table below.

While some biodegradation has been observed, the results for DTPMP-H and its salts do not show significant biodegradation in the short term, and they are not readily or inherently biodegradable, based on several reliable studies (OECD 301E, Huntingdon, 1984; OECD 301D, TNO, 2006; SCAS test, Saeger, 1978; anaerobic screening test, Zeneca, 1995; OECD 306, TNO, 1996; OECD 302B, SafePharm 1999; for further details, please refer to IUCLID Section 5.2). However, photodegradation in water in the presence of common metal ions has been observed (Lesueur et al., 2005 and Saeger, 1979a) (IUCLID Section 5.1.3). Based on evidence from the data summarised in this section, DTPMP-H and its salts are considered to be partially degradable in aqueous media over short time periods, with evidence of mineralisation, particularly in the light, over longer periods. Oxidation may also play a role in the longer term environmental fate of DTPMP, based on evidence of oxidation of structurally analogous phosphonates in the form of manganese complexes (Nowack and Stone, 2003).

Removal from the aqueous phase occurs principally by irreversible adsorption to substrates present (minerals), and to a lesser extent removal by photodegradation, oxidation in the presence of iron(III) and limited biodegradation. The significant role of adsorption is discussed in Section 5.4. For DTPMP Ksolids-water (sediment) values of 1340 l/kg (soft water) and 950 l/kg (hard water) are reported in the key study. The degradation processes operate most rapidly in combination as abiotic breakdown products are more susceptible to biodegradation than the starting material. Bioavailability from solution is extremely low due to the highly unfavourable hydrophilicity (reliable measured BCF <10 and <94 (at two different concentrations), supported by log Kow<-3.4 under environmental conditions).

In soil and sediments, removal is expected to occur by the same partitioning mechanisms. A consistent value of Ksolids-water (soil) is 380 l/kg. Bioavailability from interstitial water present in soils and sediments is extremely low due to both the very strong adsorption and low bioconcentration properties, even if the phosphonate were to be ingested in an adsorbed state in the soil or sediment constituents.

Table: Summary of significant properties affecting environmental fate of DTPMP-H and its salts


Values / results


Reference/ Discussion



Vapour pressure

2.7E-09 Pa (estimated)

<2.7E-09 Pa (estimated)


MPBPVP (v1.43;EpiWeb4.0, 2009, Syracuse Research Corporation)


ca. 500 - 700 g/l, with no pH adjustment / miscible

≥ ca. 500 - 700 g/l / miscible



Salt solubility for pH 7 (industry use information based on production materials)





Michael, P.R. (1979a)

Biodegradability (see IUCLID Section 5.2.1)

Not rapidly degradable



Huntingdon, 1984

Abiotic degradability (see IUCLID Section 5.1)

Significantly susceptible tophotodegradation; the product is more susceptible to biodegradation than the parent structure


Lesueur, 2005

Saeger, 1979


Highly adsorbing in a process which is largely irreversible


Michael, 1979


Very low (BCF <10 and <94 at two test concentrations)


Yokohama Laboratory, 2002


The properties of DTPMP-H and its salts are profoundly directed by their ionisation behaviour, as discussed in the table and paragraphs below.

Table: Ionisation behaviour of DTPMP-H and its salts and impact on environmental fate


Relevant information for DTPMP

Reference / comment

Multiple ionisations

·   13 possible ionisations

·   pKa values in literature (1.03, 2.08, 3.11, 4.15, 5.19, 6.23, 7.23, 8.30, 11.18, 12.58)

·   At pH7, DTPMP6-predominates, based on the pKa values


Tomson et al. 1994

Implication for partitioning and environmental fate

·   very hydrophilic with very high solubility limit in water (several hundred grams per litre)

·   highly adsorbing (please refer to section describing adsorption evidence)



·   strong complexing agent

·   calcium complex (41%), zinc complex (35%), magnesium complex (21%) and copper complex (2%) predominate in natural waters in presence of natural ligands


Nowack (2003)


DTPMP can ionise by loss of a hydrogen ion up to ten times and protonation of the amines up to three times. As a consequence it is a strong complexing agent, and is highly hydrophilic. Because ionisation is a rapid and reversible process, salts such as sodium and potassium salts will dissolve readily in water to give a speciation state dictated by the pH of the medium. DTPMP has thirteen possible ionisations. In a primary data source for information on pKa values and stability constants (Martell and Sillen, 1968), eight discernible pKa values of DTPMP are reported, of 2.8, 4.45, 5.5, 6.38, 7.17, 8.15, 10.1, 12.04. These were measured in 0.1 M potassium chloride. The original source (a 1967 paper in Russian) is cited in the data book. In a source giving no experimental details, DTPMP is described as having ten pKa values, of 1.03, 2.08, 3.11, 4.15, 5.19, 6.23, 7.23, 8.30, 11.18, 12.58 (Tomson et al. 1994). These values are a more complete set of data, are consistent with the values from the standard source, and are the best available set.

Ionisation state of a particular functionality changes most significantly at the pKa value (50% ionisation at the pKa value), but at one pH unit lower than the pKa there is still 10% ionisation (of the acidic functional groups; the converse being true for the protonated amine groups). In the present case, this means that at pH 7, DTPMP in water will be almost fully ionised five times, with a majority of the molecules ionised six times, and some seven or eight times; DTPMP-H in its molecular state is not present under the normal conditions of the natural environment considered in the chemical safety assessment.

Sodium, potassium and ammonium counter-ions, where present, 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 fully dissociate when in contact with water, including atmospheric moisture, but the phosphonate will complex with polyvalent metal ions when they are present. Nowack (2003) presents calculated speciation of DTPMP in natural river water sample from Switzerland with well-known composition of metals, anthropogenic and natural ligands. The other ligands compete with DTPMP and must be taken into account for a truly realistic assessment. In the presence of no other ligands, the mass balance is 24% as zinc complex and 76% as copper complex. In the presence of ETDA, NTA and natural ligands, DTPMP is present as calcium complex (41%), zinc complex (35%), magnesium complex (21%) and copper complex (2%).

The available weight of evidence shows that removal from solution to a non-bioavailable bound form, and abiotic mechanisms, are important in the environmental exposure and risk assessment. Specific deficiencies in the available studies of biodegradability are not significant compared to the other fate and distribution mechanisms.

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

Further information on the category and the validity of read-across are presented in IUCLID Section 13 and Annexes 4 and 5 of the CSR.