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EC number: 618-780-1 | CAS number: 916809-14-8
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
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Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Experimental logPow value is available for n-propyl phosphoro thioic triamide, being below 1. A bioaccumulation potential is therefore not expected for the substance.
Key value for chemical safety assessment
- Bioaccumulation potential:
- no bioaccumulation potential
Additional information
Chemical and physico-chemical description of the substance
The target substance NPPT can be described as thiophosphoric triamide, an indirect urease inhibitor, and is a crystalline solid. It is a urease analogue that blocks three active sites of the urease enzyme (CAS-No. 916809-14-8).
According to the analytical investigations, the following major component / three minor components are present:
- > 80.0 % (w/w) N-propyl-phosphorothioic triamide
- ca. 10 % (w/w) N,N’-dipropylphosphorothioic triamide
- ca. 2.5 % (w/w) N,N’-dipropylpropan-1-amine
- ca. 1.0 % (w/w) propylamine
Description of the physico-chemical properties
- Physical state (20 °C): solid
- Vapour pressure (25 °C): 2.8 * 10-6hPa
- Molecular weight: 153.19 g/mol
- Log pow(24 °C): < 0.3
- Water solubility (20 °C): 51.5 g/L
- Melting point (1013 hPa): 91 °C
- Boiling point (1013 hPa): not applicable, substance decomposes before boiling
- (Relative) Density (20 °C): 1.253 g/cm³
Toxicokinetic Assessment
No experimental data on absorption, metabolism, distribution and excretion are available for the substance. Therefore, the toxicokinetic behavior was evaluated based on the structure and the physico-chemical properties of the substance as well as data from experimental in vivo toxicity studies. Additionally, data from an experimental study with radiolabeled [14C]NBPT were taken into consideration for the assessment of NPPT.
Absorption
The molecular weight of 153.19 g/mol implies that the target substance is favourable for absorption after oral intake. Due to this comparatively low molecular weight in combination with the high water solubility, the substance may pass through aqueous pores or be carried through the epithelial barrier by the bulk passage of water. The rate of absorption will be limited because of the likely ionization of the molecule and the low log Pow. The low log Powalso is favourable for absorption by passive diffusion. With a water solubility of 51.5 g/L, the target substance is assumed to dissolve in the gastrointestinal fluid. In the acute oral toxicity study available for the reaction mass of the target substance and NBPT, a LD50of > 2000 mg/kg bw was deduced. Clinical signs like impaired general state, dyspnea, reduced feces, staggering, salivation, exsiccosis and piloerection were observed. Therefore, it is assumed that absorption has occurred. In a short-term repeated dose toxicity study with the reaction mass of the target substance and NBPT in rats the substance caused signs of systemic toxicity like decreased food consumption and decreased body weight parameters, revealing that absorption has occurred. However, apart from that, no specific data concerning oral absorption of the test substance are available. Therefore, as a worst case an oral absorption of 100 % is assumed.
With regard to absorption after inhalation, the target substance has a low vapour pressure of 2.8 * 10-6hPa and the boiling point is not applicable because the substance decomposes before boiling, indicating that inhalation as a vapour will be negligible. If the substance reaches the respiratory tract, passive diffusion is likely due to the low log Powand the rather low molecular weight. Because of the good water solubility, the substance is likely to dissolve in the mucus of the upper respiratory tract, and consequently will at least partly be removed before reaching the lower respiratory tract. Due to the lack of data as a worst case 100 % absorption after inhalation is assumed as well.
The physical state of the target substance is solid, therefore the substance will have to dissolve into the surface moisture of the skin before uptake can begin. Due to the high water solubility and low log Powthe substance may be too hydrophilic to cross the lipid rich environment of the stratum corneum. Hence, dermal uptake for this substance is suggested to be low. In the acute dermal toxicity study available for the reaction mass of the target substance and NBPT, a LD50of > 2000 mg/kg bw was deduced. As no systemic clinical signs were observed, it is assumed that the substance has only been partly absorbed. However, apart from that, no specific data concerning dermal absorption of the test substance are available. Therefore, a dermal absorption of about 10 % is assumed also based on an assessment using the DERMWIN software that calculated a Kp-value of 0.000343 cm/hr (with a worst case log Kowof 0.3) which is in line with a very low dermal absorption potential based on the user manual for the internet version of the Danish (Q)SAR database (Database Version 1 May 2005).
Distribution
The target substance is a small molecule and therefore wide distribution of the systemically available part could be assumed. In combination with the high water solubility diffusion through aqueous channels and pores is likely to occur. However, the rate at which the very hydrophilic molecule diffuses across membranes could limit its distribution. A bioaccumulation potential is not expected, considering the physico-chemical properties of the target substance. An experimental log Powvalue for the target substance being below 1 confirms this assumption.
Metabolism
In an experimental toxicokinetic study with radiolabeled NBPT, the two major metabolites of NBPT N-(n-butyl)thiophosphoric diamide and the glucuronic acid conjugate of NBPT were found in the urine samples of treated rats. Therefore, NPPT is assumed to be biotransformated to N-(n-propyl)thiophosphoric diamide and the glucuronic acid conjugate of NPPT which then hydrolyzes to N-(n-propyl)thiophosphoric diamide. Both metabolites are assumed to be readily excreted in the urine. Therefore, NPPT and / or its metabolites are not expected to bioaccumulate.
Based on the results of the repeated dose oral toxicity study in the rat with NBPT that show some microscopic changes in the liver of rats that may be consistent with increased metabolism, NPPT is assumed to behave similar. This may be a consequence of amine oxidation.
Excretion
NPPT and its metabolites will mainly be excreted via the urine due to the low molecular weight and good water solubility. Because of these properties it is also unlikely that more than 5 – 10 % will be excreted in the bile. Any test material that is not absorbed following oral ingestion will be excreted in the feces.
In an experimental toxicokinetic study with radiolabeled NBPT, NBPT was eliminated mainly via expired air and via urine. Rat liver contained the highest level of radiolabel of all measured tissues, but still contained less than 0.29 % of the administered dose. No other tissue was found to contain residues above 0.10 % of the administered dose except carcass contained 2.49 %.
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