Zinc hexafluorosilicate

Ecotoxicological Summary

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:

56.5 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

35.6 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

7.6.1. Classification under Annex I dangerous substances directive 67/548/EEC

Zinc chloride 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. Classification under2nd Adaptation to Technical Progress (ATP) to the CLP Regulation (2^ndATP CLP)

Accordingly, under CLP, this classification listed in Annex I to Directive 67/548/EEC 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 is 1, referring to a) 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, and b) the molecular weight ratio of zinc chloride versus the Zn⁺⁺ion (136 x MW (ZnCl₂/ MW (Zn) = 136 x 135/65 = 282µg substance /l at pH 8 as worst case).

The M-factor for chronic aquatic effect is 1, referring to a) the lowest chronic aquatic ecotoxicity value observed for the algae Pseudokircherniella subcapitata (19µg Zn/l) at neutral pH. The molecular weight ratio of zinc chloride versus the Zn⁺⁺ion for which the reference value of 19µg/l was derived, would lead to a chronic ecotoxicity value of 19µg/l x MW (ZnCl₂/ MW (Zn) = 19 x 135/65 = 39.5µg substance /l 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).

In conclusion, zinc chloride 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 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 39.5µg 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 chloride of 39.5µg/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

General discussion

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.

The elements brought forward above indicate that the chronic classification of zinc chloride should be “chronic 2”, rather than the “chronic 1” classification currently in Annex VI. However, since the substance has been classified under Annex VI of the CLP Regulation, this classification is applied at present.