Zinc bis(dihydrogen phosphate)

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

14.4 µg/L

Assessment factor:

1

Extrapolation method:

sensitivity distribution

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

7.2 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:

146.9 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

sensitivity distribution

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

162.2 mg/kg sediment dw

Assessment factor:

1

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:

83.1 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 Zn²⁺ 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.

An elaborated justification for this read-across approach is attached in IUCLID section 13.

Conclusion on classification

For the zinc substances, Ecotoxicity Reference Values (ERVs) are based on the soluble ion, Zn²⁺, and are determined from the extensive datasets on acute and chronic ecotoxicity testing of soluble zinc salts.  For details, please refer to IUCLID section 13.2:  “Background document – Environmental Effects Assessment of Zinc in the Aquatic Compartment. The Ecotoxicity Reference Values used for classification for acute and chronic aquatic effect at different pH bands are presented in Table 1 (for a detailed description of the setting of the ERVs, see IUCLID section 13.2, IZA 2021 document: “Ecotoxicity Reference Value for Zinc”).

Table 1. Zinc ERVs at different pH bands

	Acute	Acute	Chronic	Chronic
	pH 6 to < 7	pH 7 to 8	pH 6 to < 7	pH 7 to 8
Zn^2+ (µg/l)	154	41.4	99	11

Considering these ecotoxicity reference values for the soluble Zn²⁺ ion and considering zinc and its compounds as equivalent to being rapidly degradable, the classification of the substance for aquatic effect is "Acute 1" (H410: Very toxic to aquatic life) and “Chronic 2” (H411: Toxic to aquatic life with long lasting effects).

M-factors self-assessment:

• Acute M factor = 10
  Referring to the acute aquatic ERV values of 41.4 µg Zn/L and 154 µg Zn/L defined for the Zn²⁺ ion at pH 8 and 6, respectively, the M-Factor for acute aquatic effect of zinc ion is self-assessed as being 10, using the most conservative value obtained at pH 8.
  
  
• Chronic M-factor = 1
  Referring to the chronic aquatic ERV values of 11 µg Zn/L and 99 µg Zn/L defined for the Zn²⁺ion at pH 8 and 6, respectively, the M-factor for chronic aquatic effect of zinc ion is self-assessed as being 1. For this last conclusion, zinc is considered equivalent to being ‘rapidly degradable” in a context of chronic classification.

For the scientific background documenting this conclusion, please refer to IUCLID section 13.2: “Removal from the Water Column_Nov_2021_IZA”.