Nickel difluoride

Endpoint summary

Description of key information

The aquatic toxicity endpoints were covered by read-across to nickel-based compounds. A categorical approach was selected for read-across, where quantitative variations in effects are predicted based on quantitative variations in bioavailability of Ni ion among category members. Environmental effects of all compounds in the category are caused by transformation of the nickel compounds to produce dissolved nickel ions (Ni2+). Details on the read-across approach can be found in the attached read-across justification.

 

Individual NOEC/EC₁₀values were collected and screened for quality and relevancy, which yielded high quality data covering many different species. The selected data set covers many different families, different trophic levels and feeding regimes.

For the aquatic compartment, Biotic Liguand Models (BLMs) were used to normalize the quatic toxicity database to sets of standard physicochemical conditions for important abiotic factors (i.e. pH, hardness, and dissolved organic carbon). Additionally, an ecoregion approach was developped to represent a serias of typical freshwater systems that cover at least 90% of abiotic condition ranges in EU freshwater. For PNEC derivation, data for the most sensitive endpoint for a given species were aggregated to derive a species geometric mean ecotoxicity value. Species geometric mean values were used to establish a species sensitivity distribution (SSD), from which a median 5th percentile (HC5-50%) was derived. The Predicted No Effects Concentration (PNEC) was derived as a function of the HC5-50% and an assessment factor covering residual uncertainty (PNEC = HC5/Assessment Factor). HC5-50% values were determined fro each ecoregion scenario.

It should be noted that some reliable aquatic ecotoxicity data that passed the relevancy criteria were not included in PNEC derivation because they were obtained from tests in which the relevant geochemical parameters (pH and/or hardness) were outside of the BLM boundaries.

Additional information

Freshwater organisms effects dataset:

For algae, EC₁₀ values of Ni for chronic exposures conducted with Pseudokirchneriella subcapitata ranged from 25.3 to 425 µg Ni/L, with a median value of 88.2 µg Ni/L (n = 47). Chronic growth inhibition data (EC₁₀) are available for other additional freshwater algae species. These EC₁₀ values range from 12.3 µg Ni/L for Scenedesmus accumulates to 51.8 µg Ni/L for Coelastrum microporum.

EC50 values range from 58.8 µg Ni/L for Chlamydymonas species and the highest EC50 being 52300 µg Ni/L for Anacystis nidulans. From the database of chronic nickel toxicity to freshwater plants, individual NOEC/L(E)C10 values reported for higher plant species. NOEC/L(E)C10 values range from 6.11 to 75 μg/L for Lemna minor (Gopalapillai et al., 2013; Schlekatet al., 2010); from 50 to 80 μg/L for Lemna gibba (Klaine and Knuteson, 2003); and from 184-196 μg/L for Spirodela polyrhiza(L.) Schleiden (Oláh et al., 2015) for a final range of 6.11 to 196 μg/L for the higher plants Lemna gibba. Lemna minor, and Spirodela polyrhiza.

Chronic nickel toxicity data are available for many invertebrate species. The large majority of data are from crustaceans, but data from insects, hydrozoans, and molluscs are also available. The NOEC/L(E)C₁₀ varied between 1.4 µg/l for Lymnaea stagnalis and 1379 µg/l for Brachionus calyciflorus. 

Chronic nickel toxicity data are available for different species of fish, with NOEC/LC₁₀ values ranging from 40 µg Ni/L for Brachydanio rerio to 15420 µg Ni/L for Brachydanio rerio. NOEC/L(E)C₁₀ data are available for three species of amphibians, with values ranging from 84.5 µg Ni/L to 13.147 µg Ni/L, both values from Xenopus laevis.

In summary, NOEC/L(E)C₁₀ values for chronic nickel toxicity to aquatic organisms range from 1.4 µg Ni/L (L. stagnalis) to 13,147 µg Ni/L (X. laevis).

 

For acute toxicity to freshwater fish, there are many high quality studies.  This represents different freshwater fish species, dominated by Pimephales promelas, Oncorhynchus mykiss, and Cyprinus carpio.  The 96h LC50 values range from 0.4 mg Ni/L (Pimephales promelas) to 320 mg Ni/L (Brachydaniorerio).  

For acute toxicity to freshwater invertebrates, there are many high quality studies which predominantly report the 48h LC50 as the endpoint. Many species are represented in these studies, dominated by Daphnia magna and Ceriodaphnia dubia. The 48h LC50 values range from 0.013 mg Ni/L (Ceriodaphnia dubia) to 4970 mg Ni/L (Daphnia magna).

Many high quality acute toxicity values are available for different species of other aquatic organisms, with the lowest EC50 being 146 µg Ni/L for Xenopus laevis and the highest EC50 being 3740 µg Ni/L for Bufo terrestris. The LC50 values range from 420 µg Ni/L for Ambystoma opacumto 21427 µg Ni/L for Ambystoma opacum.

 

Marine organisms effects database:

The marine chronic ecotoxicity database is represented by many species of marine organisms from different families, and includes a wide range of taxonomic groups, including unicellular algae, macroalgae, crustaceans, molluscs, echinoderms, and fish. Bioavailability correction was not implemented in selecting the marine effects data.

EC10 values for different species of marine algae are reported, ranging from 97 µg Ni/L for growth of giant kelp (Macrocystis pyrifera) to 17891 µg Ni/L for growth of the dinoflagellate, Dunaliella tertiolecta. High quality EC50 values are available for species of marine algae, with the lowest EC50 being 456 µg Ni/L for Champia parvula and the highest EC50 being 4400 µg Ni/L for Macrocystic pyrifera.

NOEC/EC10/LOEC values are reported for marine invertebrates, ranging from 22.5 µg Ni/L for reproduction of the polychaete, Neanthes arenaceodentata, 431 μg Ni/L for development of the bivalve, Crassostrea gigas.

EC10 values are reported for marine fish, ranging from 3599 µg Ni/L for growth of the topsmelt, Atherinops affinis, to 20760 µg Ni/L for growth of the sheepshead minnow, Cyprinodon variegatus.

In summary, the chronic EC10 data used in the derivation of the HC5 (50%) for the marine compartment ranged from 22.5 µg Ni/L for Neanthes arenaceodentatato 20,760 µg Ni/L for Cyprinodon variegatus.  

For acute toxicity to marine fish, there are high quality studies that represent different marine fish species. The 96h LC50 values range from 24.8 mg Ni/L (Fundulus heteroclitus; Bielmyeret al., 2013) to 350 mg Ni/L (Fundulus heteroclitus).  

From the database of acute toxicity to marine invertebrates, there are many high quality studies which report predominantly 48h LC50 and 48h EC50 as the endpoint, representing many species. The 48h LC50 values range from 0.07 mg/L (Diadema savigny) to 415 mg/L (Penaeus duorarum; Bentley et al., 1975b). The 48h EC50 values range from 0.07 mg/L (Diadema savignyi; Rosen et al., 2015) to 4.66 mg/L (Artemia salina; Kissa et al., 2002b).

 

Effects assessment for aquatic micro-organisms in sewage treatment plants (STP):

Only a few internationally accepted test methods, such as the OECD N° 209 (inhibition of respiration of activated sludge) and ISO N° 9509 (inhibition of nitrification) exist. Short-term measurements (in terms of hours) are preferred, generally corresponding with typical retention times in biological STPs. The TGD (EC, 2003) suggests 10 has a preferable test duration. Furthermore, the information available has to be relevant for the processes that are potentially at risk of disruption, e.g., microbial degradation activity in an STP. To assess risks to these processes, microbial endpoints such as respiration and nitrification inhibition are considered to be the most relevant. Testing using a mixed microbial inoculum is considered more relevant than using single-species inoculum. Thus information reported on individual bacterial species like Microtox (with Vibrio fisheriastest organism), Pseudomonas putida, Pseudomonas fluorescens and even Escherichia coli are therefore considered as less relevant than those from mixed inoculum.

Studies assessing the effects of nickel on ciliated protozoa (preferably T. pyriformis) and respiration/nitrification using bacteria originating from sewage treatment plants were regarded as directly relevant for the derivation of a PNEC STP. The key publication selected for Ni-PNEC STP derivation is Cokgor et al (2007). No other PNEC relevant studies that investigated the effects of Ni on bacterial populations were identified. However, the other studies in the database not deemed directly relevant, supported the relevancy and the conservative nature of an EC50 of 33 mg/L.