Hydroxylammonium nitrate

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.006 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.008 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.001 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

0.5 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

no exposure of sediment expected

Sediment (marine water)

Hazard assessment conclusion:

no exposure of sediment expected

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no exposure of soil expected

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

The PNEC is the concentration of a chemical in any compartment above which there is the potential for unacceptable effects on the ecosystem and its organisms during long term or short term exposure. The PNEC is ideally derived from toxicity data for organisms living in the compartment in question that have been obtained through laboratory testing or by non-testing methods. However, if no experimental data are available for organisms of a given compartment (e.g. soil), a PNEC value can be estimated based on results of tests with other organisms (e.g. if no data on soil organisms are available then data from aquatic organisms may be used).

 

Because the diversity in ecosystems is high and only a few species are used in the laboratory, it is considered most likely that ecosystems will be more sensitive to the chemicals than individual organisms in the laboratory. Therefore, results of tests are not used directly for the risk assessment but used as a basis for extrapolation of the PNEC using defined procedures.

2.Development of Predicted No Effect Concentrations

 

2.1 Development of aquatic Predicted No Effect Concentrations

 

2.1.1 Introduction

The amount of information required under REACH on aquatic toxicity depends on the quantity of the substance manufactured or imported. Typically, data on short-term toxicity will be available for organisms representing 3 different trophic levels/groups of organisms (algae, invertebrates, fish) when a substance is manufactured or imported in a quantity of more than 10 and less than 100 t/y, but data from other groups of organisms or on long-term toxicity may occasionally be available as well. For higher tonnages, more data may be required (cf. REACH, Annexes VII-X).

2.1.2 Development of the PNEC for freshwaters

No toxicity data are available for hydroxylammonium nitrate, but relevant ecotoxicological data is available for the read across analogue hydroxylammonium sulphate, for which a European Union Risk Assessment Report has been prepared by Germany (EU RAR 2008) and hydroxylammonium hydrochloride. Most of the tests using these substances were performed at pH 7 or higher. Considering this, and the duration of the tests, it can be assumed that the substance degrades at least partially to hydroxylamine during the static exposure, and the organisms were also exposed to hydroxylamine.

 

Reliable data (Klimisch Code = 1 or 2) are available on the short-term toxicity of hydroxylammonium sulphate to algae (Scenedesmussubspicatus), short- and long-term toxicity to the invertebrate Daphnia magna and short-term toxicity data for fish with the fathead minnow Pimephales promelas (Table 42).

 

Data for hydroxylammonium hydrochloride

Table 2.1. Available experimental toxicity data on hydroxylammonium nitrate (using read across) for aquatic organisms

 

Method	Results	Remarks	Reference
Scenedesmus subspicatus (algae)   Freshwater, Static	EC20 (96 hour based on growth rate): 0.50 mg/l (nominal)   EC50 (96 hour based on growth rate): 0.81 mg/l (nominal)	2 (Reliable with restrictions)   Key study, Experimental result   Test material: Hydroxylammonium sulphate	BASF (1988b)  1. Background   For environmental effects assessment, three main environmental compartments are considered: - water - soil - air   The compartmentalisation of the environment is primarily based on the distinction between aquatic and terrestrial (“land”) compartments. For the aquatic compartment, fresh water (PNECfreshwater) and marine ecosystems (PNECsaltwater) are considered separately. In addition to these environments, risk assessment procedures have been considered for other routes of exposure or areas of concern, namely - micro-organisms in waste water treatment plants (PNECmicroorganisms) - sediments (PNECsediment) - secondary poisoning in predators exposed via the food chain (PNECoral)   The PNEC is the concentration of a chemical in any compartment above which there is the potential for unacceptable effects on the ecosystem
Daphnia magna (invertebrate)   Freshwater, Static   EC Guideline 67/548/EEC, C2	EC50 (48 hour based on immobilisation): 1.6 mg/l (nominal)	2 (Reliable with restriction)   Key study, Experimental result   Test material: Hydroxylammonium sulphate	BASF (1988a)
Daphnia magna (invertebrate)   Freshwater, Semi-static   OECD TG 211	NOEC (21 days based on reproduction):>0.62 mg/l (measured)   NOEC (21 days based on growth as weight):>0.62 mg/l (measured)   NOEC (21 days based on growth as length ): 0.31 mg/l (measured)	1 (Reliable without restriction)   Key study, Experimental result   Test material: Hydroxylammonium sulphate	BASF (2007a)
Pimephales promelas Static American Society for testing and Methods	LD50 (96 h): 7.2 mg/l Based on: mortality	2 (reliable with restrictions weight of evidence read across based on grouping of substances (category approach) Test material: Hydroxylammonium sulphate.	NAPM (1974)

 

On the basis of the available short-term toxicity data for algae, invertebrates and fish the lowest reliable toxicity value is the 21-day NOEC of 0.31 mg/l generated in the experimental long-term reproduction study with the crustacean Daphnia magna. Since reliable short-term data, as L(E)C50 values, are available for the base set (algae, invertebrates and fish) and long-term data, as NOECs, are available for algae and invertebrates an assessment factor of 50 has been applied to account for the uncertainty in the dataset. This results in:

 

PNEC_freshwater= 0.31 mg/l / 50 = 0.0062 mg/l (6.2 µg/l)

 

2.1.3 Development of the PNEC for saltwaters

Based on the 21-day NOEC of 0.31 mg/l generated in the experimental long-term reproduction study with the crustacean Daphnia magna a PNEC for saltwaters of 0.00062 mg/l(0.62 µg/l), would be derived by applying an assessment factor of 500 to account for the uncertainty in the dataset. The assessment factor includes an additional factor of 10 compared to freshwaters to account for the absence of data regarding the potential hazard presented to marine taxa such as echinoderms and molluscs.

 

2.1.4 Development of the PNEC for intermittent releases

Based on the 96h EC50 of 0.81 mg/l generated in the experimental toxicity study with the freshwater algae Scenedesmus subspicatus PNEC for intermittent releases of 0.0081 mg/l (8.1 µg/l) would be derived by applying an assessment factor of 100 to account for the uncertainty in the dataset. 

2.2 Development of the Predicted No Effect Concentrations (PNEC) for the sediments

 

2.1.1 Introduction

For organic substances and metals pore water is one of the primary exposure routes for benthic organisms (Di Toro et al. 1991; Ankley et al.1991). However, for highly lipophilic compounds or other substances that adsorb to particles (e.g. certain metals), uptake from food or sediment may contribute to the overall exposure, depending on the living and feeding strategy of the exposed organisms. Therefore, factors that influence adsorption and thus distribution between sediment and water also influence toxicity to aquatic (pelagic and benthic) species.

 

The ECHA Guidance Document R.10 states that Predicted No Effect Concentration for sediments can be derived using:

 

1. Ecotoxicological data for sediment-dwelling organisms.

2. The equilibrium partitioning method (EPM) using the PNEC_waterfor aquatic organisms and the suspended matter/water partitioning coefficient as inputs (Di Toro et al., 1991, OECD, 1992). It has to be considered that the equilibrium partitioning method may result in either an overestimation or underestimation of the toxicity to benthic organisms (Di Toro et al. 2005).Therefore, this method can only be used as an initial screening approach to decide whether sediment toxicity tests with benthic organisms are required.

 

At present no ecotoxicological data are available for sediment dwelling organisms exposed to hydroxylammonium nitrate or structurally related substances (i.e. hydroxylammonium hydrochloride or hydroxylammonium sulphate). Furthermore, it was not possible to generate reliable (Q)SAR-based predicted values from the OECD QSAR Application Toolbox. Therefore, the EPM method would have to be used to carry out an initial assessment of the potential for hydroxylammonium nitrate to cause sediment toxicity.

 

However, because of the physico-chemical properties of hydroxylamine salts it was considered relevant to review their fate of the salts in water containing particulate matter to assess whether there is a likelihood of exposure and whether PNECs for sediment need to be derived.Taking into account the inorganic character of hydroxylammonium nitrate and its high solubility in water, a complete distribution to the aqueous compartment can be expected.

 

The EU RAR (2008) for hydroxylammonium sulphate concluded that “since the physicochemical data indicate that the substance is not very adsorptive or bioaccumulative, a relevant distribution into the sediment compartment and a considerable exposure of sediment organisms are not expected. Hence, information about effects on sediment organisms is not required”. On this basis no PNEC values for freshwater and saltwater sediments have been derived since hydroxylammonium nitrate (based on data for hydroxylammonium sulphate) is not likely to be present in sediments at significant concentrations for extended periods.

2.3 Development of the PNEC for soil

 

2.3.1 Introduction

The Predicted No Effect Concentration for sediments can be derived using:

1. Ecotoxicological data for soil-dwelling (terrestrial) organisms.

2. The equilibrium partitioning method (EPM) using the PNECwater for aquatic organisms and the soil/water partitioning coefficient as inputs (Di Toro et al., 1991, OECD, 1992). The equilibrium partitioning method may not be suitable for lipophilic substances or substances with a specific mode of action nor for organisms that are exposed primarily through food (van Gestel, 1992). It should be recognised that substitution of terrestrial toxicity data by aquatic toxicity data should be used with caution. This is because the effects on aquatic species can only be considered as effects on soil organisms that are exposed exclusively to the soil pore water and may only be appropriate for organisms with a water-permeable epidermis. Furthermore, studies have shown that the equilibrium partitioning method can give significant over- or underestimations, due to inaccurate partitioning coefficients or differences in species sensitivities.Therefore, this method can only be used as an initial screening approach to decide whether soil toxicity tests with terrestrial organisms are required.

 

At present no ecotoxicological data are available for soil dwelling organisms exposed to hydroxylammonium nitrate or structurally related substances (i.e. hydroxylammonium hydrochloride or hydroxylammonium sulphate). Furthermore, it was not possible to generate reliable (Q)SAR-based predicted values from the OECD QSAR Application Toolbox. Therefore, the EPM method would have to be used to carry out an initial assessment of the potential for hydroxylamine nitrate to cause soil toxicity.

 

However, because of the physico-chemical properties of hydroxylamine it was considered relevant to review the fate of the salts in water containing particulate matter to assess whether there is a likelihood of exposure and whether PNECs for sediment need to be derived. Taking into account the inorganic character of hydroxylammonium nitrate and its high solubility in water, a complete distribution to the aqueous compartment can be expected.

 

The EU RAR (2008) for hydroxylammonium sulphate concluded that “Due to production methods, processing, and use of hydroxylammonium sulphate and considering further the distribution behaviour of the substance, a relevant exposure of this compartment can be excluded”.On this basis no PNEC values for freshwater and saltwater sediments have been derived since hydroxylammonium nitrate (based on data for hydroxylammonium sulphate) is not likely to be present in soils at significant concentrations for extended periods.

 

2.4 Development of the Predicted No Effect Concentration (PNEC) for micro-organisms in waste water treatment plants

No data are available on the biodegradation of hydroxylammonium nitrate but data are available from three tests on the effects of hydroxylammonium sulphate on the inhibition of activated sludge were submitted (BASF 1979, BASF 1984, BASF 2007a).

 

In the two older studies, inoculum of the producer’s sewage treatment plant was used. Due to insufficient documentation, especially on the test procedure, test duration and the origin of the inoculum both studies were invalid (Klimisch Code = 3). However, in both tests a concentration-dependent inhibition of microbial respiration was observed starting at concentrations of 0.5 - 1 mg/l. The EC20 values determined in the studies were 0.6 and 1.0 mg/l.

 

In 2007 BASF conducted a third valid study (Klimisch Code = 1) on the effects of hydroxylammonium sulphate on activated sludge (BASF 2007a). The inhibition of oxygen consumption by activated sludge was investigated according to OECD 209. Activated sludge was obtained from a municipal wastewater treatment plant, test concentrations ranged from 0.05 to 504 mg/l (nominal). After 180 minutes incubation at 20 ± 2 °C the respiration rates were recorded. At a test concentration ≤ 5 mg/l the test substance did not inhibit respiration, at 50.4 mg/L 56% inhibition was observed (approximating the EC50), whilst at 504 mg/l 78% inhibition was recorded.

 

Hydroxylammonium sulphate is known to inhibit microbial activity, also in sewage treatment plants (BASF 1997). Other findings (e.g. Amarger and Alexander 1968), indicate an inhibition of microbial activity due to high concentrations of hydroxylamine. However, since hydroxylamine is an intermediate in the nitrification process, in lower concentrations hydroxylamine is expected to be degraded biologically to nitrite (e.g. Jetten et al. 1997). Taking these findings together with the data concerning transformation of hydroxylammonium sulphate, it can be assumed that the toxicity to microorganisms is associated with high concentrations of the hydroxyl-ammonium ion or hydroxylamine. In sewage treatment plants pH is buffered to pH 8 where the hydroxyl-ammonium ion is present only in very low concentrations. In addition to that, hydroxylamine (free base) is expected to decompose rapidly due to abiotic processes. The remaining concentration is not expected to inhibit microbial activity. Hence it can be assumed that additional biological degradation occurs in the waste water treatment plant.

 

The test on hydroxylamine sulphate conducted following OECD Guideline 209 is considered valid and the calculated EC20 of 5 mg/l (which is considered to represent the NOEC) has been used to derive a PNEC for aquatic microorganisms. Hence, the PNEC for the assessment of microbial activity in biological treatment plants is calculated as follows using an assessment factor of 10

 

PNEC_{micro-organisms}= 5.0 mg/l / 10 = 0.5 mg/l

 

2.5 Non-compartment specific effects relevant for the food chain (secondary poisoning)

It is not expected that hydroxylammonium nitrate will accumulate in aquatic organisms (particularly fish) and the food chain based on an experimentally derived log Kow of -3.6 for hydroxylammonium sulphate. No accumulation in organisms and the food chain is expected.Therefore, no PNECs for secondary poisoning have been derived.

Conclusion on classification

Hydroxylamine nitrate is classified as Aquatic acute 1, H400, very toxic to aquatic life.