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EC number: 215-149-9
CAS number: 1306-25-8
Referring to “ECHA Guidance on the Application of the CLP Criteria Guidance to Regulation (EC) No 1272/2008 on classification, labelling and packaging (CLP) of substances and mixtures Version 5.0 July 2017” (ECHA 2017), the environmental classification of CdTe under CLP is made based on:
a) the acute and chronic ecotoxicity reference values (ERVs) for soluble Cd substances.
b) the specific 7day and 28 day transformation/dissolution (TD) data obtained on CdTe
Given the much lower aquatic toxicity of the Te-ion, the contribution of Te to the classification is negligible (see below)
1) Acute classification of CdTe for aquatic effect
-in the 7d TD test with 1 mg/L CdTe loading, 14.1µg Cd/L is dissolved
-so, at 1mg/L loading, the dissolved amount of Cd is less than the ERV: 14.1 µg Cd/L < 18 µg Cd/L (toxic unit ratio: 0.78)
-the 7d TD test with 1 mg/L substance loading shows also 15.7µg Te/L dissolved
-the acute ERV of Te is 5.8mgTe/L
-the toxic unit ratio for Te is 0.003. The contribution of Te is thus negligible compared to the effect of Cd.
Given that the dissolved Cd concentration in the 7d TD test at 1mg/L loading of CdTe is lower than the acute ERV for Cd, and the contribution of Te to the classification is insignificant,CdTe is not classified for acute aquatic effect under CLP
(ECHA 2017: Annex IV.5.2.: classification strategies for metals: “Concentration at 1 mg/l loading rate ≥ acute ERV of dissolved form? NO” (figure IV.1. p589)
Chronic classification of CdTe for aquatic effect:
-in the 28d TD test with 1 mg/L loading 23.2 µg Cd/L is dissolved
-the chronic ERV for Cd is 0.21µg Cd/L
-the28d TD with 1 mg/L loading results in 25.6 µg Te /L dissolved
-the lowest NOEC of Te for algae is 4.2mg Te/L (no chronic ERV for Te yet available - testing proposal for long term aquatic toxicity on Daphnia submitted)
For determining the chronic classification from these data, reference is made to a) Table 4.1.0 of the guidance: “Classification categories for hazardous to the aquatic environment” (ECHA 2017, p505-506), and b) to the section IV.5.2.2 of the guidance: “Classification strategy for determining long-term aquatic hazard for metals” (ECHA 2017, p589-590).
Following table 4.1.0., the “rapid degradability” of the substance needs also to be determined for assessing the chronic classification. Cadmium, like all metals, is an element, and therefore the criterion “degradability” cannot be applied as it is developed for organic substances (“for metals and inorganic metal compounds, the concept of degradability as applied to organic compounds has limited or no meaning” (ECHA 2017, p495).
As a surrogate for evaluating the criterion on “degradability”, the concept of “removal from the water column” was developed for metals, to assess whether or not a given metal (ion) would upon addition remain present in the water column for a longer time (and thus be able to exert a chronic effect) or would be rapidly transformed, resulting in its removal from the water column. In this concept, “rapid removal” (defined as >70% removal within 28 days, cfr the criterion for degradability) is considered as equivalent to “rapidly degradable”. The rapid removal of cadmium from the water column is documented under section 4.6.2. of the CSR. Consequently, the metal is considered as equivalent to being ‘rapidly degradable” in the context of classification for chronic aquatic effects, and, referring to the chronic classification scheme in table 4.1.0., the approach under (b)(ii) (“Rapidly degradable substances for which there are adequate chronic toxicity data available” - ECHA 2017, p505), is used for the classification.
Referring to the criteria as set out in table 4.1.0.(b)(ii), the Cd concentration dissolved at 0.01mg/L loading of CdTe is calculated from the TD result obtained at 1 mg/L loading :23.2 µg Cd/L/100 = 0.23 µg/L.
Considering that the chronic ERV for Cd is exceeded at 0.01mg/L loading (0.23µg/L > 0.21 µg/L),CdTe is classified chronic 1, according to section IV.5.2.2 of the guidance, “Classification strategy for determining long-term aquatic hazard for metals” (ECHA 2017, p590): “a. Classify the metal as Category Chronic 1 if the dissolved metal ion concentration obtained at a loading rate of 0.01 mg/l is greater than or equal to the chronic ERV, an M factor must also be established as part of this classification”. Since the ERV for Cd is not exceeded at loading of 0.001mg/L CdTe, the M-factor is set at 1. Te has no influence on the above conclusions (28d TD result Te <<< lowest observed NOEC for Te). An earlier TD test performed in 2010 showed with 1mg/L loading after 28d a slightly lower Cd concentration than the ERV: 19 +/- 7.7 µg/L; however, considering the rather high observed standard deviation, the chronic 1 classification as derived above is considered appropriate. In this earlier experiment, the Te TD results showed also very low concentration (18.3 +/- 8.2µg Te/L), compared to the lowest NOEC for Te on algae.
“The standard protocol in Annex 10 to UN GHS presently only foresees a long-term loading rate of 1 mg/l and lower loading rates may not even be practically feasible for each case. While TDp testing at lower loading rates is in principle the best way forward it is technically often not feasible for the lower chronic loading rates. Extensive experience with the T/D protocol demonstrated that reliable predictions can be made for other loading rates. In order to make maximal use of existing Transformation Dissolution data, the 28 days results for the lower chronic loading rates (0,1 and 0,01 mg/l) can therefore be derived by extrapolation from TDp evidence from other loading rates”. (ECHA 2017, p585)
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