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:
56.5 mg/kg sediment dw
Assessment factor:
1
Extrapolation method:
equilibrium partitioning method

Hazard for air

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

Trizinc bis(orthophosphate) was classified N; R50-53 (Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment) according to Directive 67/548/EEC (ECB 2008).

7.6.2. Classification under2nd Adaptation to Technical Progress (ATP) to the CLP Regulation (2ndATP 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 theacuteaquatic effect of trizinc bis(orthophosphate) is 1, referring to a) the acute aquatic ecotoxicity values (EC50) 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 trizinc bis(orthophosphate) versus the Zn++ion (136 x MW (Zn3(PO4)2 / MW (Zn) = 136 x 385/65 = 806µg substance /l at pH 8 as worst case).

The M-factor forchronicaquatic effect of trizinc bis(orthophosphate) is 1, referring to a) the lowest chronic aquatic ecotoxicity value (NOEC) 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).

Moreover, the molecular weight ratio of trizinc bis(orthophosphate) 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 (Zn3(PO4)2 / MW (Zn) = 19 x 385/65 = 113µg substance /l which is above both criteria for chronic 1 classification for aquatic effect (being 10µg/l or 100µg/l). This suggests that the substance should not be classified chronic 1, but chronic 2 or 3 (depending on whether or not the substance is considered rapidly degadable or not).

In conclusion, Trizinc bis(orthophosphate) 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 Trizinc bis(orthophosphate) 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), the chronic classification of the substance should be reconsidered:

As was mentioned above, when the MW ratio between Zn and the substance is factored into the assessment of the chronic ecotoxicity reference value (19µg/l x MW (Zn3(PO4)2 / MW (Zn) = 19 x 385/65 = 113µg of substance /l), this reference value is higher than the criteria for chronic 1, and/or chronic 2 classification, depending on whether the substance is considered rapidly degradable or not.

The concept of “Degradability” was developed for organic substances and is not applicable as such 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 from the wwater column” (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 the information mentioned above with a chronic ecotoxicity reference value for Trizinc bis(orthophosphate of 113µg/l, and considering zinc and its compounds as equivalent to being rapidly degradable, the classification of the substance for chronic aquatic effect should be “chronic 3”, 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 trizinc bis(orthophosphate) should be “chronic 3”, 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 Annex VI classification is applied at present.