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Description of key information

Ecotoxicity reference values (ERV)


The ERVs are based on the ecotoxicity of the Zn++ion. For deriving the ERVs for acute and chronic toxicity, all individual data were normalized towards two pH values (6 and 8), and, to further ensure conservatism, towards realistic worst-case conditions for DOC (2mg/L, the value also referred to in TD protocol (OECD 2001)). Water hardness was set at 40mg Ca/L which is the 50P of EU waters as described in the EU wide database FOREGs (Salminen 2005). It is noted that hardness is not relevant for zinc toxicity to the algae, which are often the most sensitive taxonomic group. By predicting the ecotoxicity for all individual values against exactly the same physicochemical conditions, all individual values could be considered for calculating the species geomean, according to ECHA guidance (ECHA 2017). This approach has the advantage that the sources of variability mentioned above are largely reduced, which enhances significantly the reliability and relevancy of the end result. The lowest geomean values for acute and chronic toxicity at pH 6 and 8 are selected as the ERV.


For data and full analysis, see document "Ecotoxicity Reference Value for Zinc for aquatic classification", IUCLID section 13.


 


ERVs for acute aquatic effect:



  • at pH 6.0: 154 µg Zn/l (Daphnia magna)

  • at pH 8.0: 41 µg Zn/l (Pseudokirchneriella subcapitata)


ERVs for chronic aquatic effect:



  • at pH 6.0: 99 µg Zn/l (Pseudokirchneriella subcapitata)

  • at pH 8.0: 11 µg Zn/l (Pseudokirchneriella subcapitata)


 


References


ECHA 2017. Guidance on the application of the CLP criteria, version 5, July 2017


OECD 2001. series on testing and assessment No 29: Guidance document on transformation/dissolution of metals and metal compounds in aqueous media. http://www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=env/jm/mono(2001)9&doclanguage=en 


Salminen R. 2005. Geochemical Atlas of Europe. http://weppi.gtk.fi/publ/foregsatlas/ 

Additional information

1. Aquatic toxicity: freshwater, short-term


Acute data - establishing the dataset


In accordance to the approach followed in the RAR, only acute data from standardised test protocols were considered in the analysis for setting the reference value for classification. This is possible because numerous data are available, and it ensures that the tests were performed under rather well defined and standard conditions.


Still, the quality and some aspects of relevancy should be checked in a critical way when using the extensive datasets from the open literature, available for zinc. It is e.g. important to know the conditions under which the organisms were tested and cultured, because these conditions may result in acclimatisation and deviating toxicity response. The information on these test conditions is often scarce in non-standardised test reports.


The short-term aquatic ecotoxicity data base for zinc was reviewed according to the following principles:



  • the data accepted for setting the acute aquatic reference value in the RA (ECB 2008, Annex 1.3.2a, table 1) were as such also accepted and used for the present analysis. Prescriptions from standard protocols were strictly followed, e.g. data from an acute Daphnia test exceeding 48 hrs were not used.

  • Data that were rejected for use in the RA (ECB 2008, Annex 1.3.2a, table 2) were also not used for the present analysis. In this respect, data from studies that were accepted for use in the chronic database, but rejected for use in the acute toxicity database were reconsidered; this resulted in the acceptance of a few additional data.

  • In accordance to the approach followed in the RA, acute data obtained in natural waters that contained e.g. significant amount of DOC, were not used. Exception to this rule were data obtained on the N.-American Great Lakes waters, which were used, in accordance to the RA.

  • Fish data mentioned in the RA under “EHC 1996” were not used, since they were from a review, not from original study reports. These data are not influencing the outcome of the analysis, since they are all at the higher concentration level.

  • More recent (obtained after 1996 to the present) short-term acute toxicity data on standard organisms were included in the database.


After checking and updating the data base, the data are normalized towards pH 6 and 8 and towards realistic worst-case conditions for DOC (2 mg/L) and a water hardness of 40 mg Ca/L. If 4 or more data points were available on a same species, the geomean of the normalized values was calculated and used for the analysis.


Acute data - results


The short-term acute aquatic toxicity database covers 59 species (5 algae, 29 invertebrates, 21 fish species, 3 amphibians and 1 aquatic plant). The full set of EC50 values are presented together with the pH and hardness of the test media in the document "Ecotoxicity Reference Value for Zinc for aquatic classification", IUCLID section 13.


 


 


2. Aquatic chronic toxicity: 


Chronic data - establishing the dataset


A vast database on chronic ecotoxicity of zinc to freshwater and marine organisms is available. Based on that, a Species Sensitivity Distribution (SSD) approach has been developed for the assessment of zinc in the freshwater and marine compartment, using the reliable species-specific chronic toxicity effects.


 


The chronic freshwater and marine toxicity dataset for zinc was checked according to the general criteria for data quality:


- toxicological endpoints, which may affect the species at the population level, are taken into account. In general, these endpoints are survival, development, hatching, growth and reproduction,


- whether or not toxicity values are considered chronic is not determined exclusively by exposure time, but also by the generation time of the test species, e.g., for unicellular algae and other microorganisms (bacteria; protozoa), an exposure time of four days or less already covers one or more generations thus for these type of species, chronic NOEC values may be derived from relatively short experiments. For PNEC derivation a full life-cycle test, in which all relevant toxicological endpoints are studied, is normally preferred to a test covering not a full life cycle and/or not all relevant endpoints. However, NOEC values derived from tests with a relatively short exposure time may be used together with NOEC values derived from tests with a longer exposure time if the data indicate that a sensitive life stage was tested in the former tests,


- test media should be relevant: both artificial and natural marine waters are selected,


- for freshwater tests pH, hardness and temperature should be reported. In case pH or hardness is not reported, the composition of the test medium or type of test medium should be provided. DOC should be measured or robustly estimated; for marine toxicity tests pH, salinity (preferably, although it is expected that pH (±8) /salinity (±30 ppt) does not substantially change in marine test media) and test temperature should be reported,


-for bioavailability normalization puroposes in the freshwater compartment, the physico-chemistry of the test media should be within the boundaries of the bioavailability models (pH 5.7 – 8.4, and Ca 4.8 – 156 mg/L; see Table 10),


- Zn concentrations should be measured in test media (or as a minimum in stock solutions),


- only the results of tests in which the organisms were exposed to zinc alone are used, thus excluding tests with metal mixtures,


- statistically derived EC10 or NOEC values are retained; in cases where both the NOEC and EC10 values are available from the same experiment, preference is given to the EC10. If the EC10 was used as NOEC equivalent, the EC10 should not be more than 3.2-times lower than the lowest concentration used in the test, and the confidence intervals should not be too wide (and it is proposed that the confidence interval should not exceed a factor of ±10),


- unbounded NOEC values (i.e., no effect was found at the highest or lowest concentration tested) are not used.


For the purpose of PNEC setting the lowest toxicity value for the most sensitive endpoint observed on the species is selected. The lowest value is determined on the basis of the geometric mean if more than one value for the same endpoint is available. An overview of these species-specific toxicity data for the freshwater compartment is given in Table 1, while Table 2 provides an overview for the marine environment. It should be emphasized that for freshwater PNEC derivation purposes, all individual chronic toxicity value are first normalized to the specific water chemistry of European surface waters using bioavailability models.


 


Freshwater:


 


The 41 distinct chronic species ecotoxicity values from 17 taxonomic groups that were used for the SSD in the present analysis are summarised in the CSR, and in table below. The “species mean” NOEC values used for PNEC derivation (freshwater PNECadd, aquatic), range from 13.9 to 1310 µg/l.


The following table gives an overview of the geometric mean and most sensitive freshwater species-specific chronic K2-NOEC/EC10-values for zinc (values as reported in references; non-normalized for bioavailability)





























































































































































































































































































































































































































































Test organism



Taxonomic group



Endpoint



Geometric mean EC10/NOEC (µg/L)



Lowest EC10/NOEC (µg/L)



Acipenser transmontanus



Fish (Acipenseridae)



Growth (length)



195



104.2



Growth (weight)



104.2


 

Mortality



136.6


 

Alathyria profuga



Mollusc (Bivalvia)



Mortality



29.6



29.6



Anuraeopsis fissa



Rotifer



Gross reproductive rate



35.1



30.8



Life span



31.8


 

Net reproductive rate



30.8


 

Rate of population increase



43.7


 

Brachionus calyciflorus



Rotifer



Growth Rate



215.1



215.1



Brachionus rubens



Rotifer



Gross reproductive rate



98.7



39.0



Life span



68.9


 

Net reproductive rate



39.0


 

Rate of population increase



64.0



 



Bryocamptus zschokkei



Crustacean (Copepoda)



Mortality



300.0



300.0



Reproduction



300.0



 



Ceriodaphnia dubia



Crustacean (Cladocera)



Mortality



87.1



51.8



Reproduction



51.8


 

Chlorella sp. (isolate 12)



Alga (Chlorophyta)



Growth rate



136.0



136.0



Cirrhinus mrigala



Fish (Cyprinidae)



Growth (weight)



100.0



100.0



Cottus bairdi



Fish (Cottidae)



Biomass



37.0



27.0



Growth (length)



27.0


 

Growth (weight)



37.0


 

Mortality



69.6


 

Cucumerunio novaehollandiae



Mollusc (Bivalvia)



Mortality



13.9



13.9



Cyprinus carpio



Fish (Cyprinidae)



Mortality



1183.7



1183.7



Danio rerio



Fish (Cyprinidae)



Hatching



666.1



666.1



Daphnia longispina



Crustacean (Cladocera)



Mortality



1587.0



181.0



Reproduction (number of juveniles)



181.8


 

Reproduction (brood size)



181.0


 

Daphnia lumholtzi



Crustacean (Cladocera)



Mortality



24.9



24.9



Reproduction



42.8



 



Daphnia magna



Crustacean (Cladocera)



Intrinsic growth rate



263.0



107.5



Mortality



125.0


 

Reproduction



107.5


 

Dreissenia polymorpha



Mollusc (Bivalvia)



Mortality



382



382



Echyridella menziesii



Mollusc (Bivalvia)



Mortality



148.2



148.2



Ephoron virgo



Insect Ephemeroptera



Mortality



718.0



718.0



Euchlanis dilatata



Rotifer



Mortality



31.0



31.0



Reproduction



92.4



 



Gobiocypris rarus



Fish (Cyprinidae)



Mortality



78.0



78.0



Hyalella azteca



Crustacean (Amphipoda)



Reproduction,



42.0



42.0



Mortality



42.0



 



Hyridella australis



Mollusc (Bivalvia)



Mortality



15.4



15.4



Hyridella depressa



Mollusc (Bivalvia)



Mortality



22.8



22.8



Hyridella drapeta



Mollusc (Bivalvia)



Mortality



23.2



23.2



Jordanella floridae



Fish (Cyprinodontidae)



Growth



26.0



26.0



Lampsilis siliquoidea



Mollusc (Bivalvia)



Growth (length)



32.7



32.7



Mortality



126.0


 

Lemna gibba



Plant (Araceae)



Frond numbers



2120.0



1310.0



Growth (weight)



1310.0



 



Lithobates chiricahuensis



Amphibia



Development



62.0



62.0



Growth (length)



62.0


 

Growth (weight)



62.0



 



Lymnaea stagnalis



Mollusc (Gastropoda)



Development



530.0



223.0



Growth Rate (length)



506.8


 

Growth rate (weight)



223.0


 

Microcystis aeruginosa



Cyanobacteria



Growth (cell density)



1000.0



1000.0



Navicula pelliculosa



Alga ((Diatomaea)



Growth rate



280.0



280.0



Oncorhynchus mykiss



Fish (Salmonidae)



Biomass



150.0



150.0



Growth (length)



300.0


 

Growth (weight)



199.0


 

Mortality



152.9


 

Phoxinus phoxinus



Fish (Cyprinidae)



Mortality, Growth



50.0



50.0



Pimephales promelas



Fish (Cyprinidae)



Reproduction



78.0



78.0



Planothidium lanceolatum



Cyanobacteria



Growth (cell density)



234.0



234.0



Potamopyrgus jenkinsi



Mollusc (Gastropoda)



Growth



72.0



72.0



Pseudokirchneriella subcapitata



Alga (Chlorophyta)



Growth Rate



24.1



24.1



Salmo trutta



Fish (Salmonidae)



Hatching



119.4



119.4



Salvelinus fontinalis



Fish (Salmonidae)



Hatching



534.0



534.0



Velesunio ambiguus



Mollusc (Bivalvia)



Mortality



28.9



28.9



 


The data in the above table (the geometric mean for the most sensitive endpoint) have been used for the construction of a Species Sensitivity Distribution (SSD) from which the median 5th percentile was derived. This value represents the HC5,50% with 5%-95%-confidence interval. The outcome of this analysis allows the derivation of the HC5,50% with 5%-95% confidence interval, and this value should be used for PNEC-derivation (i.e., PNECaquatic= HC5,50%/Assessment Factor). For the purpose of PNEC setting, the lowest value normalised for bioavailability for the most sensitive endpoint is selected for the freshwater compartment. The lowest value is determined on the basis of the geometric mean if more than one value for the same endpoint is available.


Since chronic toxicity of Zn depends on the physico-chemistry of the test medium, all chronic toxicity data (i.e., NOEC/EC10 values) from the database were normalized to the various combinations of specific physico-chemical conditions occurring in European surface waters, as reflected by the conditions monitored in the individual monitoring sites from the FOREGs database  (http://weppi.gtk.fi/publ/foregsatlas/index.php). All freshwater chronic toxicity data were normalized to each of the different environmentally relevant water chemistries documented in this extensive  dataset (see BOX 1). After this bioavailability normalization, the geometric mean value of the most sensitive endpoint per species is used as input data for the calculation of the HC5,50% related to each of the different physico-chemistries occurring in the FOREGs dataset. The distribution of all these HC5,50% values is finally used for setting the  PNEC value for Zn. The different steps in this process are described in more detail in the background document.


 


For each sampling site from the FOREGs database, a separate normalized SSD is constructed through fitting of the log-normal transformed normalised toxicity data to 7 different distributions, ie. cauchy, exponential, gamma, log-normal, logistic, normal, weibull and gumbel. Best fitting statistic such as Anderson-Darling was used to select the best fitting distribution for each of the 546 datapoints from the FOREGs database, after which HC5,50% values were derived for each sampling site from the FOREGs database. In the last step, a distribution of all 546 bioavailabilty normalized HC5,50%’s were plotted and the 10th percentile of that distribution is proposed as final HC5,50% value (Figure 2), resulting in a value of 14.4 µg Zn/L (as normalised dissolved value). The 10th percentile is proposed to represent reasonable worst-case conditions of bioavailability in PNEC derivation in analogy with the use of the 90th percentile of reasonable worst-case setting in the PEC derivation (ECHA 2008).


 


Based on the weight of evidence from the different considerations provided by the extensive uncertainty analysis, combined with the inherent conservatism resulting from the setting of the HC5,50% value with reference to realistic worst case conditions of bioavailability, an Assessment Factor of 1 on the HC5,50% is applied for the derivation of the PNEC, resulting in a PNECfreshwater of 14.4 µg Zn/L.


 


For a detailed discussion on the uncertainty related to the SSD and the HC5, and the derivation of the PNEC, seethe background document on environmental risk assessment of zinc in the aquatic compartment, attached to section 13 of IUCLID.


 


 


 


 


Marine:


 


The 32 distinct chronic species ecotoxicity values from 18 taxonomic groups that were used for the SSD in the present analysis are summarised in the CSR, and in table below. The “species mean” NOEC values used for PNEC derivation (freshwater PNECadd, aquatic), range from 4.2 to 2074 µg/l.


 


 


The following table gives an overview of the geometric mean and most sensitive marine species-specific chronic NOEC/EC10-values for zinc (all values Klimish 2 score)


















































































































































































































































































Test organism



Taxonomic group



Endpoint



Geometric mean EC10//NOEC (µg/L)



Lowest EC10//NOEC (µg/L)



Allorchestes compressa



Crustacean (Amphipoda)



Mortality



63.0



63.0



Apostichopus japonicus



Echinoderm (Holothuroidea)



Mortality



444.0



18.8



Growth rate (weight)



18.8



 



Capitella capitella



Annelid (Polychaeta)



Reproduction



108



108.0



Ceramium tenuicorne



Macrophyte (Rhodophyta)



Growth (length)



11.9



11.9



Conticriba weissflogii



Alga (Thalassiosirales)



Growth rate



430.0



430.0



Cryothecomonas armigera



Alga  (Cryomonadida)



Growth rate



366.0



366.0



Crassostrea gigas



Mollusc (Bivalvia)



Mortality



254.0



192.9



Growth (length)



192.9



 



Etroplus suratensis



Fish (Cichlidae)



Mortality



1480.0



1480.0



Evechinus chloroticus



Echinoderm (Echinacea)



Growth (length)



10.0



9.7



Development



9.7



 



Gaimardia trapesina



Mollusc (Bivalvia)



Mortality



2074.0



2074.0



Galeolaria caespitosa



Annelid (Polychaeta)



Fertilization



134.8



134.8



Haliotis diversicolor supertexta



Mollusc (Gastropoda)



Growth rate (length)



64.0



64.0



Haliotis iris



Mollusc (Gastropoda)



Development



4.2



4.2



Haliotis rufescens



Mollusc (Gastropoda)



Development



15.3



15.3



Harpacticus sp.



Crustacean (Copepoda)



Mortality



122.6



122.6



Holmesimysis costata



Crustacean (Mysida)



Mortality



7.1



7.1



Hyale longicornis



Crustacean (Amphipoda)



Mortality



970.0



970.0



Hydroides elegans



Annelid (Polychaeta)



Development (larvae settlement)



23.2



23.2



Development


(from eggs to trochophore larvae)



37.0



 



Macrocystis pyrifera



Macroalga (Lessoniaceae)



Growth (length of germination tubes)



190.2



190.2



Melita awa



Crustacean (Amphipoda)



Mortality



480.0



480.0



Melita matilda



Crustacean (Amphipoda)



Mortality



230.0



230.0



Mysidopsis juniae



Crustacean (Mysida)



Growth (length)



75.0



64.5



Mortality



64.5



 



Mytilus galloprovincialis



Mollusc (Bivalvia)



Development



54.0



54.0



Mytilus trossolus



Mollusc (Bivalvia)



Development



48.0



48.0



Neanthes arenaceaodentata



Annelid (Polychaeta)



Reproduction



108.5



108.5



Nitzschia closterium



Alga (Bacillariales)



Growth



85.5



85.5



Penaeus monodon



Crustacean (Decapoda)



Mortality



8.6



8.6



Phaeocystis antarctica



Alga (Phaeocystales)



Growth rate



450.0



450.0



Pleurochrysis roscoffensis



Alga (Syracosphaerales)



Growth rate



100.0



100.0



Sepia officinalis



Mollusc (Cephalopoda)



Growth rate (length)



53.0



53.0



Mortality



185.0



 



Strongylocentrotus purpuratus



Echinoderm (Echinacea)



Development



29.0



29.0



Thalassiosira pseudonana



Alga (Thalassiosirales)



Growth (cell density)



350.0



350.0



Tigriopus angulatus



Crustacean (Copepoda)



Mortality



1190.8



1190.8



 


 


 


The data in the above table(the geometric mean for the most sensitive endpoint) have been used for the construction of a Species Sensitivity Distribution (SSD) from which the median 5th percentile was derived. This value represents the HC5,50% with 5%-95%-confidence interval. The outcome of this analysis allows the derivation of the HC5,50% with 5%-95% confidence interval, and this value should be used for PNEC-derivation (i.e., PNECaquatic= HC5,50%/Assessment Factor). For the purpose of PNEC setting the lowest toxicity value for the most sensitive endpoint is selected for the marine compartment. The lowest value is determined on the basis of the geometric mean if more than one value for the same endpoint is available.


 


The SSD was constructed through fitting of log-normal transformed toxicity data to 7 different distributions using the bootstrapping method, ie. exponential, gamma, log-normal, logistic, normal, weibull, and gumbel. The outcome of this analysis allows the derivation of the HC5,50% with 5%-95% confidence interval, and this value should be used for PNEC-derivation (i.e., PNECaquatic= HC5,50%/ Assessment Factor). Using this analysis, the Weibull distribution was defined as the optimal distribution considering the Anderson-Darling goodness-of-fit statistics, which emphasizes the tails of the distributions. The HC5,50% (± 95%CL) that was associated with this distribution was 7.2 µg Zn/L (95%CL: 4.4– 12.5 µg Zn/L; see Table 16). Application of an assessment factor between 1 and 5 on this HC5,50% results in the final PNEC for zinc in the aquatic environment. The value of this assessment factor depends on the uncertainty analysis. Based on the weight of evidence from all the different considerations provided by this extensive analysis  an Assessment Factor of 1 on the HC5,50% is applied for the derivation of the marine water PNEC,  resulting in a PNECmarine of 7.2 µg Zn/L. 


For a detailed discussion on the uncertainty related to the SSD and the HC5, and the derivation of the PNEC, see the background document on environmental risk assessment of zinc in the aquatic compartment, attached to section 13 of IUCLID.