Registration Dossier

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
PNEC aqua (freshwater)
PNEC value:
20.6 µg/L
Assessment factor:
1
Extrapolation method:
sensitivity distribution

Marine water

Hazard assessment conclusion:
PNEC aqua (marine water)
PNEC value:
6.1 µg/L
Assessment factor:
1
Extrapolation method:
sensitivity distribution

STP

Hazard assessment conclusion:
PNEC STP
PNEC value:
100 µg/L
Assessment factor:
1
Extrapolation method:
assessment factor

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
117.8 mg/kg sediment dw
Assessment factor:
1
Extrapolation method:
sensitivity distribution

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
121 mg/kg sediment dw
Assessment factor:
2
Extrapolation method:
sensitivity distribution

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
PNEC soil
PNEC value:
106.8 mg/kg soil dw
Assessment factor:
1
Extrapolation method:
sensitivity distribution

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

A basic assumption made in this hazard assessment and throughout this CSR, (in accordance to the same assumption made in the EU RA process) is that the ecotoxicity of zinc and zinc compounds is due to the Zn++ion. As a consequence, all aquatic, sediment and terrestrial toxicity data in this report are expressed as “zinc”, not as the test compound as such, because ionic zinc is considered to be the causative factor for toxicity. A further consequence of this is that all ecotoxicity data obtained on different zinc compounds, are mutually relevant for each other. For that reason, the available ecotoxicity databases related to zinc and the different zinc compounds are combined before calculating the PNECs. The only way zinc compounds can differ in this respect is in their capacity to release zinc ions into (environmental) solution. That effect is checked eventually in the transformation/dissolution tests and may result in different classifications.

Conclusion on classification

In the RA, distinction was made for classification between zinc in powder form and in massive form, based on the following observations regarding the criteria, set out in the guidance:

-the evidence on Transformation/Dissolution according to OECD 29 testing, summarised in section 4.8., demonstrates the significantly lower potential for Zn++ ion release from the massive form, as compared to zinc powder.

-zinc powder is produced only by specific (atomisation) processes, not by normal handling and use of the massive form

- zinc in massive form is, under conditions of normal handling and use, basically melted by the first line zinc users (e. g; galvanisers, alloyers, manufacturers of semi-finished products such as rolled zinc). The massive zinc is not polished, ground, machined or handled in any other way that may give rise to small (e. g; <1mm) particles.

 

7.6.1. Classification of zinc powder/dust under Annex I dangerous substances directive 67/548/EEC

Zinc powder-zinc dust (pyrophoric and stabilized) was classified N; R50-53 (Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment) according to Annex 1 of Directive 67/548/EEC (ECB 2008).

7.6.2. Revised classification of zinc powder/dust under2nd Adaptation to Technical Progress (ATP) to the CLP Regulation (2ndATP CLP)

According to the classification listed in Annex I to Directive 67/548/EEC, the classification of zinc powder was translated as H400 - H410 (very toxic to aquatic life with long lasting effects) according to Annex VI of the EU CLP Regulation (EU 2008).

The M-Factor for the acute aquatic effect of zinc powder is 1, referring to the acute aquatic ecotoxicity values of 136 µg Zn/l and 413 µg Zn/l for the zinc ion at pH 8 and 6 respectively.

The M-factor for chronic aquatic effect of zinc powder/dust is 1, referring to a) the lowest chronic aquatic ecotoxicity value observed for the algae Pseudokircherniella subcapitata (19µg Zn/l) at neutral pH. This reference value is in any case less than factor 10 different from the criterion for chronic 1 classification for aquatic effect (being 10µg/l or 100µg/l depending on whether or not the substance is considered rapidly degadable or not).

In conclusion, zinc powder is classified under CLP as H400, H410. The M-factor for both acute and chronic aquatic effects is 1.

7.6.3. Further considerations on the classification of Zinc powder/dust based on recent information

Taking into account the lowest chronic ecotoxicity value observed on a wide variety of species of different taxonomic groups (19 µg Zn/l), it can be reconsidered what exactly the level of chronic classification of the substance should be:

As was mentioned above the chronic ecotoxicity reference value for the substance is 19 µg Zn/. This value must be compared with the criteria for chronic classification, also taking into account whether the substance is considered rapidly degradable or not.

The concept of “Degradability” was developed for organic substances and is not applicable to inorganic substances like zinc. As a surrogate approach for assessing “degradability”, the concept of “removal from the water column” was developed to assess whether or not a given metal ion would remain present in the water column upon addition (and thus be able to excert a chronic effect) or would be rapidly removed from the water column. In this concept, “rapid removal” (defined as >70% removal within 28 days) is considered as equivalent to “rapidly degradable”. Under section 4.6., the rapid removal of zinc from the water column is documented. Consequently,zinc is considered as equivalent to being ‘rapidly degradable” in the context of classification for chronic aquatic effects. 

Considering this, in combination with the abovementioned chronic ecotoxicity reference value for zinc of 19 µg/l, the classification of the substance for chronic aquatic effect should be “chronic 2”, rather than the “chronic 1” classification in Annex VI of the CLP

7.6.4. Classification of zinc in massive form under Annex I dangerous substances directive 67/548/EEC

Zinc metal in massive form was not classified under Directive 67/548/EEC, and does not figure in.Annex 1 of Directive 67/548/EEC (ECB 2008).

7.6.5. Classification of zinc metal in massive form under2nd Adaptation to Technical Progress (ATP) to the CLP Regulation (2ndATP CLP)

The potential ecotoxicity of metals in massive form is determined by their capacity to release ions in aqueous media. This capacity is assessed in transformation/dissolution (T/D – see section 4.6.) testing. For zinc metal in massive form, this approach is relevant. The assessment below is made on T/D results obtained at pH 6, at which release of zinc ions from metal is maximal.

Acute classification

Under section 4.6., transformation dissolution data were presented and demonstrate that zinc ions are released from massive zinc in a limited way only. It was concluded from the data that at1mg/l loading, the critical diameter of a sphere resulting in sufficient surface loading to reach the reference value for acute aquatic effects, is 0.082 mm.

In other words, the diameter of a zinc metal sphere of 1mg should be ≤ 0.082 mm, in order to reach the reference value for acute aquatic effects. This particle size is much smaller than the default particle size distinguishing massive metal from powder/dust (1mm).

Consequently, zinc metal in massive form is not classified for acute aquatic effect.

 

Chronic classification

In a similar approach as the one described above for acute classification, T/D data were used for chronic classification too. In this case, however, information on long-term T/D (28days) was used (section 4.8.). The critical diameter of a spherical metal particle, resulting in sufficient surface loading to reach the reference value for chronic aquatic effects at 1mg/l loading of the substance was set at 2.1 mm. Accordingly, the critical diameters of a sphere, resulting in reaching the reference value for chronic aquatic effect at mass loading criteria of 0.1mg/l and 0.01mg/l are determined to be 0.21 mm and 0.021 mm, respectively.

 

The 2.1mm critical diameter for loading at 1mg/l is slightly greater then the default particle size distinguishing massive metal from powder/dust (1mm). However, 2 additional elements can be observed in this respect:

- When the epoxy-mounted zinc surfaces (see section 4.6.) after the test were kept for 3 days in the laboratory air, and the test was repeated, the zinc amount dissolving was only 50% of the original amount that had been observed (T/D after 7 days at 100 mg/l loading was 2656 µg Zn/l and 1321 µg Zn/l, on freshly polished metal and metal passivated in water, respectively) (Rodriguez 2010). This demonstrates that the freshly polished metal surface had passivated over 7 days in the test solution, and , when re-immersed for checking further dissolution, only released half of the original amount. So passivation in water is occurring rapidly (within 7 days) and is significant. The critical diameter for zinc release of a “passivated” spheric particle be only half the one calculated for the freshly polished surface.This observation is relevant for the dissolution potential of zinc from a metallic zinc surface in aqueous medium. Considering this effect, the critical diameter of a spherical metal particle, resulting in sufficient surface loading to reach the reference value for chronic aquatic effects at 1mg/l loading of the substance would be equal to the default size for distinguishing powders/dusts and metal in massive form.

 

An additional remark can be made on the forms and sizes of metallic zinc produced in the EU.The vast majority of zinc in massive form is put on the EU market as large ingots and blocks (>1Tonne). Detailed analysis of the sizes and forms and related tonnages that were put on the market shows that < 0.01% of the massive forms would fall in the category 0.3-1cm; sizes smaller than this range are only observed in the powder/dust range (<1mm) (IZA-Europe 2002). Furthermore, under normal handling and use, zinc in massive form is basically melted by the first line zinc users (e.g; galvanisers, alloyers, manufacturers of semi-finished products such as rolled zinc). The massive zinc is not polished, ground, machined or handled in any other way that may give rise to small (e.g; <1mm) particles. The CLP guidance allows for deviation from the default particle size of 1mm for massive forms for classification, if justified. The elements mentioned under this item demonstrate that 2.1mm size particles are not at all representative for the massive forms of zinc produced and put on the EU market.

 

In conclusion, considering the elements above, zinc metal in massive form is not classified for chronic aquatic effect.