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EC number: 233-296-7 | CAS number: 10108-64-2
Freshwater short term toxicity
Acute data- establishing the dataset
Numerous data are available on acute toxicity of cadmium to aquatic organisms. The quality and relevancy of the unique data is of great importance because, in contrast to the PNEC derivation (where all the chronic data are used in a species sensitivity distribution), one single value defines the ecotoxicity reference value for classification. Therefore, for setting the reference value for classification, only data from standardised test protocols and organisms were considered in the analysis.
The RAR made an in-depth analysis of the reliability of the acute data and assigned a “reliability index” (RI) to each data point. For setting the reference value for acute aquatic ecotoxicity, only the results qualified as RI 1 (standard tests) were used, complemented for the fish and invertebrates with RI 2 qualified data (not standard test but from a similar protocol and with a complete background information on test conditions).
In the RAR, acute ecotoxicity reference values were specifically set for Cd (metal) and CdO. These values were based on high quality (Q1=RI 1) test results. Since these data are expressed on basis of a measured cadmium (ion) concentration, they were pooled with the data obtained on other Cd-compounds, also mentioned in the RAR.
This strict selection of the highest quality data is possible because the high number of acute data that are available. It ensures that the tests were performed under well defined and/or standard conditions, and provide a sound basis for classification.
The acute aquatic ecotoxicity data base for cadmium was reviewed further according to the following principles:
Hardness is the main determining factor for Cd toxicity to aquatic organisms (RAR 2007). Cd-toxicity is more important under conditions of low hardness. Therefore, in the review of the acute data, special attention was paid to considering and selecting data obtained under low hardness conditions. Only tests performed at Cd background <1µg Cd/l were used, according to the RAR.
If 4 or more data points were available on a same species, and the data were obtained under similar conditions, the geomean was calculated and used for the analysis.
Acute data - results
The short-term acute aquatic toxicity data on cadmium for all species (1 algae species, 2 invertebrate species, and 6 fish species) are summarised in the CSR.
The data span for all groups a variety of hardnesses, from very low to high. Low hardness data are available for all 3 taxonomic groups. Most data are obtained at neutral to higher pH (7-8.5).
The EC50 values show strong variability, but the lowest values observed at low hardness are of the same order of magnitude for all 3 taxonomic groups.
In conclusion, the data set covers the 3 taxonomic groups (algae, daphnids and fish) and allows to set the reference value for acute aquatic toxicity for Cd (dissolved, ionic form). The lowest value is obtained on the algaeSelenastrum capricornutumunder low hardness conditions: 18 µg Cd/l. This value was also used as reference value for acute aquatic toxicity in the RAR on CdO (ECB 2007).
Chronic data - establishing the dataset
As for the acute toxicity, numerous data are available on the chronic toxicity of cadmium to aquatic organisms. The quality and relevancy of the data has been reviewed in detail by the Belgian rapporteur for the EU risk assessment (RA; ECB 2007).
The chronic aquatic toxicity data (NOECs) that are used for PNEC derivation in the EU RA, are summarised in table below. Chronic NOECs categorised RI 1 and RI 2 are combined with data categorised RI 3. For some species, no species geomean was made, because test was done in different medium or different endpoint was mentioned. It is noted that the “case-by-case” approach deviates from the one generally used in statistical extrapolation; still, it was used in the EU risk assessment and therefore taken over in the present analysis.
Results' extensive table "Case-by-case"- selected NOEC data of effects of Cd in freshwater and case-by-case calculation of 'geometric mean NOEC's can be found in the CMR (after table 3.2.9C of the EU risk assessment).
In the EU RA, it was concluded that the conditions for using a statistical extrapolation method to derive the PNEC for Cd in freshwater were met. Accordingly, this approach is also used for the present analysis. All chronic data mentioned in table referred to above are used in a species sensitivity distribution (SSD), and the PNEC is derived based on the HC5 concentration.
As one multi-species LOEC and 3 single species LOECs were under the HC5, an assessment factor 2 was applied to give the final PNEC freshwater = 0.19 µg/l Cd
Hardness is the main determining factor for Cd toxicity to aquatic organisms (RAR 2007). Cd-toxicity is more important under conditions of low hardness. The effect of water hardness on Cd toxicity has been quantified by the US-EPA (US-EPA 2001). Based on data for e.g.Daphnia magna, Pimephales promelasandSalmo trutta, a quantitative relationship between hardness and chronic toxicity could be derived and is expressed as follows:
PNECHx= 0.09 (50/Hx)0.7409
Marine long term toxicity
The Cd Risk Assessment has not carried out an effect assessment on the aquatic marine environment, while REACH requires protection of this environmental compartment, i.e. the derivation of a saltwater PNEC for Cd. The saltwater PNEC derived in this section covers truly marine conditions. It is derived based on chronic toxicity data from the literature. The available chronic cadmium toxicity 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 cadmium in marine waters were searched and reviewed for sources of relevant and reliable chronic toxicity data on cadmium. Only original literature was used.
Data reliability and relevance
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.
Chronic toxicity of Cd in saltwater
Aquatic marine ecotoxicity database for cadmium
The marine cadmium 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, 48 species mean NOECs based on 62 NOEC values, coming from 39 families and 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 Cd database includes 1 micro- and 1 macro-algae species, 4 annelid species, 11 crustacean species, 7 echinoderm species, 13 mollusc species, 3 nematod species, 2 cnidarian species, 1 ascidian species and 6 fish species. The geometric mean values of the species NOECs are presented in the CSR.
Statistics on Species sensitivity distribution
Given the multitude of relevant high quality ecotoxicity data, species mean NOECs were plotted in a species sensitivity distribution (SSD) and statistical extrapolation was used for PNEC determination. 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. But according to the rules established in previous Risk Assessments for metals, and given the significance levels are accepted, the use of a log-normal distribution is preferred over other statistical distributions (Cd RAR 2007).
The 5thpercentile value of the SSD (the HC5), set at 50% confidence value, using the lognormal distribution (ETX 2.0) function, results in a value of 2.28 µg cadmium/L. This value is taken forward for the PNEC derivation.
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