Zinc bis[12-hydroxyoctadecanoate]

Endpoint summary

Additional information

Zinc bis[12-hydroxyoctadecanoate]:

Based on similar structural analogy, water solubility and zinc content of zinc bis[12-hydroxyoctadecanoate] (CAS 35674-68-1) and Fatty acids, C16-18, zinc salts (CAS 91051-01-3), a 1:1 read-across of ecotoxicological data of Fatty acids, C16-18, zinc salts is applied to zinc bis[12-hydroxyoctadecanoate].

 

Aquatic toxicity: freshwater, short-term

Invertebrates: The acute toxicity of Fatty acids, C16-18 zinc salts to Daphnia magna was determined according to OECD 202 in M7 medium at pH 6 and 8 (Bouwman et al., 2003). The EC50was not reached up to a loading rate of 100 mg Fatty acids, C16-18 zinc salts /L. At this loading, the zinc concentration at the beginning of the test was 1170 μg Zn/L at pH 8 and 800 μg Zn/L at pH 6. The test report concludes: “No daphnids became immobilised during the test period... Although all daphnids exposed to the undiluted water fraction had test substance on their bodies at the end of the test, this did not hinder them”. It is concluded, that the toxicity of the substance fatty acids, C16 -18, zinc salts to daphnia is (far) above the water solubility.

Fish: Information on fish toxicity of Fatty acids, C16-18 zinc salts is available from a study performed according to EU Method C.1 (Acute Toxicity for Fish) in the former version of 1992 (Henkel KGaA, 1995), from a study performed according to OECD Guideline 203 (Fish, Acute Toxicity Test) but reported only in a short study report (TÜV Bayern Sachsen E.V., 1992) and from an old publication (Dowden and Bennett, 1965). In the most reliable study (Henkel KGaA, 1995), fish (Danio rerio) were exposed for 96 hours to nominal concentrations of 0 (control), 1000, 3000 and 10000 mg/L under semi-static conditions. The nominal concentrations far exceed the water solubility of Fatty acids, C16-18, zinc salts by 3 to 4 orders of magnitude. Measures to disperse the test substance in the test water were used. At all tested concentrations, including the highest nominal test concentration, neither behavioural abnormalities nor mortality occurred. In addition, no effects were observed at nominal Fatty acids, C16-18, zinc salts concentrations up to the water solubility limit in two further studies. In accordance with the evaluation given in the EU Risk assessment on zinc distearate (Final report R074_0805_env, May 2008), it is concluded, that the toxicity of the substance fatty acids, C16 -18, zinc salts to fish is (far) above the water solubility limit of around 1 mg/L.

Algae:The toxic effects of Water Accommodated Fractions (WAF) of Fatty acids, C16-18, zinc salts on the growth rate of algae (Pseudokirchneriella subcapitata) were studied in three tests according to OECD Guideline 201 (Wenzel, 2010a,b and 2013). While in the first test, the WAF of a loading of 100 mg/L in a non-standard test medium was dilutedin series to allow the calculation of toxicity parameters (EL10, EL50) (Wenzel, 2010a), the WAFs of several loadings (1, 10, and 100mg/L) in non-standard test medium were tested in the second test according to OECD Series No. 23 (Wenzel, 2010b). In the third test by Wenzel (2013), lower concentration were applied (i.e. 0.01, 0.1, 1.0, 10.0 and 100.0 mg/L) in the standard test medium to enable the classification for a potential aquatic hazard based on WAFs. The EL50 value for the 72-h inhibition of growth rate of Pseudokirchneriella subcapitata in the standard test medium is estimated > 100 mg/L.

 

Aquatic toxicity: freshwater, long-term

Based on the comprehensive data set on aquatic long-term toxicity of zinc and mean values for standard species (i.e.Pseudokircherniella subcapitata, Daphnia magna, Oncorhynchus mykiss), algae appear to be the most sensitive taxa; respective NOEL/EL10 estimates for the long-term toxicity of zinc to invertebrates and fish are substantially higher (more than factor of 4) than the NOEL/EL10 value for algae. Thus, chronic toxicity data for algae determine the worst-case hazard and testing of further taxa is scientifically not justified. Chronic toxicity data of Fatty acids, C16-18, zinc salts are available for algae. The long-term toxic effects of Water Accommodated Fractions (WAF) of Fatty acids, C16-18, zinc salts on the growth rate of algae (Pseudokirchnerella subcapitata) were studied in a state-of-the-art test according to OECD Guideline 201 (Wenzel, 2013). The WAFs were prepared according to OECD Series No. 23 in the standard test medium to enable the classification for a potential chronic aquatic hazard based on WAFs. Thus, WAFs of the loadings 0.01, 0.1, 1.0, 10.0 and 100.0 mg/L were tested; the EL10 value for the 72-h inhibition of growth rate of P. subcapitata in standard test medium is 3.31 mg/L.

As further chronic toxicity data are not available for Fatty acids, C16-18, zinc salts and respective data are also not available for zinc bis[12-hydroxyoctadecanoate], a read-across to insoluble/slightly soluble zinc substances is made, and the PNECs water as derived in the Chemical Safety Assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 are read-across to zinc bis[12-hydroxyoctadecanoate].

Marine toxicity:

As marine toxicity data are lacking for zinc bis[12-hydroxyoctadecanoate] and Fatty acids, C16 - 18, zinc salts, a read-across to insoluble/slightly soluble zinc substances is made, and the PNECs water as derived in the Chemical Safety Assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 are read-across to zinc bis[12-hydroxyoctadecanoate].

 

Conclusions:

It is concluded that the toxicity of Fatty acids, C16 -18, zinc salts to bacteria and the acute toxicity of Fatty acids, C16 -18, zinc salts to algae, Daphnia and fish is (far) above the water solubility limit of around 1 mg/L. The chronic endpoint of the most sensitive trophic level, i.e. the estimated EL10 value for the 72-h inhibition of algal growth rate by Fatty acids, C16 -18, zinc salts in a standard test is 3.31 mg/L (based on testing WAFs of individual loadings).and also above the water solubility limit of around 1 mg/L. These conclusions are read-across to zinc bis[12-hydroxyoctadecanoate] and are consistent with conclusions from the EU RAR for the structural analogue Zinc distearate (CAS-No.: 557-05-1 & 91051-01-3 EINECS-No.: 209-151-9 & 293-049-4) Part 1 - Environment (Final report R074_0805_env, May 2008: "From these data, although very limited, it is concluded that the toxicity of zinc distearate to bacteria and the acute toxicity of zinc distearate to Daphnia magna and fish is (far) above the water solubility limit of around 1 mg/L)."

 

As only limited chronic toxicity data are available for Fatty acids, C16-18, zinc salts and respective data are not available for zinc bis[12-hydroxyoctadecanoate], a read-across to insoluble/slightly soluble zinc substances is made, and the PNECs water as derived in the Chemical Safety Assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 are read-across to zinc bis[12-hydroxyoctadecanoate]. For a comprehensive overview of the toxicity of zinc, see the hazard assessment of "Zinc" within the framework of Regulation (EC) No 1907/2006 below.

ZINC:

1. Aquatic toxicity: freshwater, short-term

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 grouped per species as follows:

-pH: low (6 -<7) - neutral/high (7 -8.5)

-hardness: low/medium (<100mg CaCO3/l) and medium/high (>100 mg CaCO3/l).

If 4 or more data points were available on a same species, the geomean was calculated and used for the analysis.

Acute data – results

The short-term acute aquatic toxicity database covers 10 species (1 algae, 4 invertebrates and 5 fish species). The full set of EC50 values are presented together with the pH and hardness of the test media in the CSR. A significant number of data are available at both low and neutral/high pH.

 

species	Low pH/ hardness<100mg CaCO3/l	Low pH, hardness>100mg CaCO3/l	Neutral-high pH/ hardness<100mg CaCO3/l	Neutral-high pH, hardness>100mg CaCO3/l
algae
Selenastrum capricornutum	/	/	0.136	/
Daphnids
Daphnia magna	/	/	0.244	1.052
Daphnia pulex	0.425	/	0.364	0.507
Daphnia carinata	/	/	0.34	/
Ceriodaphnia dubia	0.413	> 0.530	0.147	0.228
Ceriodaphnia reticulata	/	/	/	0.937
fish
Pimephales promelas	/	0.780	/	0.33
Thymallus arcticus	/	/	0.307	/
Cottus bairdii	/	/	/	0.439
Oncorrhynchus kisutch	/	/	1.155	/
Oncorrhynchus mykiss	/	/	0.169	/

Discussion: reference values for short term aquatic ecotoxicity

Table above presents an overview of the information available for short-term aquatic toxicity for zinc. It can be seen that significant number of data are available at both low and neutral/high pH.

At low pH, 2 values are available for 2 daphnia species. The values are similar. They were obtained at lower hardness, where the highest sensitivity is expected, which is confirmed by the value >530 µg/l, obtained on Ceriodaphnia dubia at high hardness. Algae are as a rule not tested under standardised conditions at low pH, but from chronic algae data (72 hrs NOECs), it is known that the sensitivity of algae is much lower at lower pH. Simulation with the biotic ligand model gives an aquatic ecotoxicity value for algae at pH 6 which is about 5 times higher than the one observed at neutral/high pH. Fish toxicity at low pH is also not critical in this respect, so the values for the daphnids are representative for the sensitivity of organisms to zinc at low pH. The lowest value observed for Ceriodaphnia dubia is used for the classification at low pH.  

At neutral/high pH, the value obtained on the algae Selenastrum capricornutum is the lowest of the dataset. This value is taken forward as reference value for classification at this pH. This value is obtained at low hardness conditions, where sensitivity is highest. The same algae species is also the most sensitive in the chronic aquatic toxicity database (see below) so this sensitivity pattern is consistent. Among the daphnids, Ceriodaphnia dubia is also here the most sensitive, and the lowest value comes close to the one for the alga. From the paired data, it follows that the Daphnids are more sensitive at lower hardness than at the higher hardnesses. The fish are also at this pH less sensitive to zinc, although the lowest value observed on O. Mykiss also comes close to the reference value. All together, the lowest values among the species show also here a consistent pattern, supporting the lowest value identified.

In conclusion, the reference values for the Zn⁺⁺ion that are used for the aquatic toxicity hazard assessment of Zn⁺⁺are:

• for low pH: 0.413 mg Zn/l (based on single lowest value for Ceriodaphnia dubia)
• for the neutral/high pH: 0.136 mg Zn/l (based on single lowest value for Selenastrum capricornutum (=Pseudokircherniella subcapitata)

2. Aquatic chronic toxicity: freshwater

Chronic data - establishing the dataset

In this analysis, like in the RAR, the results of the chronic aquatic toxicity studies are expressed as either the actual (measured) concentration or as the nominal (added) concentration (Cn). The actual concentrations include the background concentration (Cb) of zinc. Because of the “added risk approach”, the results based on actual concentrations have been corrected for background, if possible. This correction for background is based on the assumption that only the added concentration of zinc is relevant for toxicity. In case both actual and nominal concentrations were reported, the results are expressed in the RAR (and in this CSR) as nominal concentrations, provided the actual concentrations were within 20% of the nominal concentrations.

Many of the reported aquatic toxicity data (either actual or nominal) represent total-zinc concentrations, i.e. the dissolved plus particulate fraction. However, the results are regarded as being dissolved-zinc concentrations, because under the conditions that were used in the laboratory tests, it is assumed that the greater part of zinc present in the test waters was in the dissolved fraction. This is especially true for the long-term studies, e.g. by using flow-through systems, in which particulate matter (suspended inorganic material and/or organic matter) was removed from the artificial test waters or natural waters. The fact that in ecotoxicity testing the nominal added concentration of zinc is very close to the actually measured zinc concentration, is also demonstrated by the many data reported in the papers of the chronic aquatic ecotoxicity database. Also in static and flow-through acute toxicity studies with several saltwater species, dissolved zinc was greater than 93% of the total zinc. Therefore, the PNEC_addvalues derived from the aquatic toxicity studies are considered to be relevant for dissolved zinc.

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

-study design preferably conform to OECD guidelines or equivalent

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

- whether or not NOEC 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 considerably less already covers one or more generations, especially in water, thus for these kinds 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.  

-If for one species several chronic NOEC values (from different tests) based on the same toxicological endpoint are available, these values are averaged by calculating the geometric mean, resulting in the “species mean” NOEC.

-If for one species several chronic NOEC values based on different toxicological endpoints are available, the lowest value 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.

-In some cases, NOEC values for different life stages of a specific organism are available. If from these data it appeared that a distinct life stage was more sensitive, the result for the most sensitive life stage is selected. The life stage of the organisms is indicated in the tables as the life stage at start of the test (e.g. fish: yearlings) or as the life stage(s) during the test (e.g. eggsàlarvae, which is a test including the egg and larval stage).

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

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

-If the NOEC was <100 µg/l, the separation factor between the NOEC and LOEC should not exceed a factor of 3.2.

-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.

-Like in the RAR, only the results of tests with soluble zinc salts are used, thus excluding tests with “insoluble” zinc salts (ZnO, ZnCO₃), unless dissolved zinc is measured.  

 

Referring to the EU RA on zinc (ECB 2008), all the data that were accepted for deriving the freshwater PNEC in the RA (ECB 2008, Annex 3.3.2.A. part I) were as such also accepted for the present analysis. On the other hand, the data that were considered not useful for the purpose of PNEC derivation in the RA (ECB 2008, Annex 3.3.2.A. part II), were also not used for the present analysis.

 

The relevancy of the long-term aquatic ecotoxicity data base for PNEC derivation was further checked in accordance to the same principles as those applied in the RA (ECB 2008). Relevancy was checked

1) related to the zinc background: in accordance to the RA (ECB 2008), a level of 1µg/l Zn was set as a cut-off for this.

2) related to test medium conditions: Zinc ecotoxicity to aquatic organisms is a function of the physicochemical characteristics of the water. Parameters such as hardness, pH, dissolved organic carbon (DOC) are well-known drivers for zinc ecotoxicity. For this reason, it was considered important in the EU RA to select ecotoxicity data that were obtained under test conditions similar to the conditions observed in EU waters. Based on information related to the parameters mentioned above in EU waters, the following boundaries for EU relevancy for pH, hardness have been used in the RA (ECB 2008) and also in the present analysis for data selection, also considering OECD test guidelines:

pH:                             minimum value: 6

                                   maximum value: 9

Hardness:                   minimum value: 24 mg/l (as CaCO₃)

                                   maximum value: 250 mg/l (as CaCO₃)          

As indicated above, background zinc concentration was also considered in the RA to be a factor influencing the toxicity response of organisms to zinc; to avoid influence of acclimatisation towards very low or very high zinc concentrations (not occurring in the EU waters), a minimum value for soluble zinc was also set in the RAR for data selection: “around 1 µg/l” (ECB 2008).

Data obtained under conditions failing these relevancy criteria were not used for PNEC derivation in the present analysis. For a detailed description of the relevancy criteria and their application in the RA, see the RAR (ECB 2008).

It is realised that the selected ranges of the three criteria will not cover all European aquatic systems, e.g. specific aquatic systems in the Scandinavian countries. In particularly, hardness is much lower in the Scandinavian countries, although also other abiotic parameters differ from the ‘average’ situation in European freshwaters. Therefore, a “soft water PNEC_{add, aquatic}” has been derived in the RA process, in addition to the generic PNEC_{add, aquatic}.The present analysis however relates to the development of a generic PNEC for EU waters.

DOC: Tests have been considered relevant for the present analysis if DOC concentrations in the test media are between 0 mg/l and 13 mg/l. In most test solutions, DOC is not present.

 

The extensive dataset on chronic aquatic toxicity in the RA (ECB 2008) was also updated with new information. This information was screened for the same criteria as those described above.

For details on data selection see the CSR zinc.

 

Results

The 23 distinct chronic species ecotoxicity values that were used for the SSD in the present analysis are summarised in the CSR. The “species mean” NOEC values used for PNEC derivation (freshwater PNEC_{add, aquatic}), range from 19 to 530 µg/l.

PNEC derivation

All adequate chronic data on fish, invertebrates, algae and plants were considered together in a species sensitivity distribution (SSD), and the PNECwas calculated by means of statistical extrapolation, using all available chronic NOEC values as input. The database is indeed sufficiently large and answers the basic requirements to use an SSD, since it covers the required 8 different taxonomic groups and > 10 test organisms.

Since the log-normal distribution significantly fits the data, this distribution was used for the SSD (like in the RAR). Other conditions to apply statistical extrapolation were also met (see CSR, discussion on the safety factor to be applied to the HC5). 

 

Because of the inclusion of 6 additional species, the species sensitivity distribution (SSD) that was calculated for the present analysis is slightly different from the one of the RAR (2008). For a detailed discussion on the uncertainty related to the SSD and the HC5, and the derivation of the PNEC, see the CSR.

As a result of the analysis, a PNEC freshwater of 20.6 µg Zn/l was derived.

3. Aquatic chronic toxicity: marine waters

For zinc, a specific effects assessment was made and a specific PNEC was derived for the marine environment, since there is a vast dataset available on marine ecotoxicity. This specific approach is also more reflective of the toxicity of zinc in the marine environment given the different speciation and bioavailability of zinc in salt – and freshwater, and differences in physiology of saltwater organisms. Given the vast amount of available toxicity data, statistical extrapolation was used to derive the marine PNEC. This marine effects assessment is following an added risk approach, as applied for the freshwater.

 

 

Sources of data

The ecotoxicological data were derived from original papers, published in peer-reviewed international journals. Literature and environmental databases, including AQUIRE (US EPA), MARITOX, ECETOC, and BIOSIS, as well as review articles covering zinc in marine waters were searched and reviewed for sources of relevant and reliable chronic toxicity data on zinc. Only original literature was used.

 

Data reliability and relevancy

Selection of ecotoxicity data for quality was done according to a systematic approach as presented by Klimisch et al. 1997. Standardized tests, as prescribed by organizations such as ASTM, OECD and US EPA, are used as a reference when test methodology, performance and data treatment/reporting are considered. A detailed description of data reliability and relevancy is provided in the CSR.

 

PNEC saltwater

Ecotoxicity database for zinc on species of the marine aquatic environment

The marine zinc database largely fulfils the species and taxonomic requirements for input chronic toxicity data as explained in the RIP R. 10 guidance (at least 10 species NOECs and 8 taxonomic groups). Indeed, 39 species mean NOECs based on 48 NOEC values, from 9 taxonomic groups covering three trophic levels were found to fulfil the relevancy and reliability requirements as explained by Klimisch et al. 1997. The marine zinc database includes 4 micro- and 5 macro-algae species, 4 annelid species, 6 crustacean species, 5 echinoderm species, 9 mollusc species, 1 nematod species, 1 cnidarian species and 1 fish species. The geometric mean values of the species NOECs are presented in the CSR.

 

Statistics on the species sensitivity distribution (SSD)

Given the multitude of relevant high quality toxicity data, statistical extrapolation was used for PNEC determination. As the approach taken is based on added risks, the results of the toxicity tests based on measured concentrations were corrected for background zinc concentration. Given the wealth of experimental data, no alternative method i.e. assessment factor approach was applied for the PNEC determination.  

Following the RIP R. 10 guidance, different distributions may be used for the SSD. Fitting of the chronic zinc toxicity data was assessed towards the log-normal frequency distribution (default distribution).  To be conform with the approach taken in the Zn RAR 2008, it is the lognormal distribution which was used to provide a basis for setting the PNEC saltwater, in spite of a better fit with the Weibull statistical distribution.   It is noted also that the PNEC is a PNECadd., i.e. the background concentration needs to be considered in the compliance assessment exercise. The 5^thpercentile value of the SSD (the HC5), set at 50% confidence value, using the lognormal distribution function, results in a value of 6.09 µg zinc/L. For further details on the setting of the PNEC from the SSD, see the CSR zinc.

Reference:

RAR zinc: European Communities, European Union Risk Assessment Report CAS: 7440-66-6 EINECS No: 231-175-3 ZINC METAL, EUR 24587 EN, available athttp://echa.europa.eu/documents/10162/d7248de0-eb5b-4a9b-83b9-042c4fd66998