1,3,5-triazine-2,4,6(1H,3H,5H)-trione, zinc salt

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

93.6 µg/L

Assessment factor:

1

Extrapolation method:

sensitivity distribution

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

27.7 µg/L

Assessment factor:

1

Extrapolation method:

sensitivity distribution

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

454.5 µg/L

Assessment factor:

1

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

535.5 mg/kg sediment dw

Assessment factor:

1

Extrapolation method:

sensitivity distribution

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

256.8 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:

161.8 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

The fate and toxicity of zinc cyanurate in the environment is most accurately evaluated by separately assessing the fate of its constituents zinc and cyanurate.

 

In transformation/dissolution tests according to the OECD Series on Testing and Assessment Number 29 (2001) with a loading of 1 mg/L, a nearly complete dissolution of zinc cyanurate was already observed after 24 h resulting in dissolved Zn concentrations of 173 microg Zn/L at pH 6 and 164 microg Zn/L at pH 8 (corresponding to 854 and 811 microg/L zinc cyanurate, respectively). Thus, zinc cyanurate is soluble and expected to dissociate upon contact with water and to release zinc cations and cyanurate anions. The respective dissociation is reversible and the ratio of the salt /dissociated ions is dependent on the metal-ligand dissociation constant of the salt, the composition of the solution and its pH.

In the assessment of enviromental fate of zinc cyanurate, read-across to the assessment entities soluble zinc substances and cyanuric acid is applied since the ions of zinc cyanurate determine its environmental fate and toxicity. Since zinc cations and cyanurate anions behave differently in the environment, including processes such as stability, degradation, transport and distribution, a separate assessment of the environmental fate and toxicity of each assessment entity is performed. Please refer to the data as submitted for each individual assessment entity.

Conclusion on classification

Aquatic toxicity studies with zinc cyanurate are not available. In the assessment of zinc cyanurate, read-across to the assessment entities soluble zinc substances and cyanuric acid is applied since the ions of zinc cyanurate determine its fate and toxicity in the environment. Reliable data available for soluble zinc substances and cyanurate indicate that the moiety of ecotoloxicological concern are zinc cations. Toxicity data of cyanuric acid point to low potential for acute (short-term) and long-term aquatic toxicity to algae, invertebrates and fish. The aquatic hazard assessment is based on the most toxic moiety, i.e. the zinc cation, and acute and chronic ecotoxicity reference values of zinc are recalculated for zinc cyanurate based on a maximum zinc content of 22 %.

Zinc cyanurate meets based on i) the acute aquatic ecotoxicity values of 136 µg Zn/L and 413 µg Zn/L for the zinc ion at pH 8 and pH 6 respectively; ii) the maximum zinc content of zinc cyanurate of 22 %, and iii) the resulting acute ecotoxicity reference value of 618 µg/L zinc cyanurate at pH 8 as worst case, classification criteria of acute (short-term) aquatic hazard Category 1 of Regulation (EC) No 1272/2008 with an acute M-Factor of 1.

Zinc cyanurate meets based on i) the lowest chronic aquatic ecotoxicity reference value observed for the algae Pseudokircherniella subcapitata (19 µg Zn/L) at neutral pH; ii) the maximum zinc content of zinc cyanurate of 22 %, and iii) the resulting chronic ecotoxicity reference value of 86 µg/L zinc cyanurate as worst case, classification criteria of long-term aquatic hazard of Regulation (EC) No 1272/2008.

The chronic ecotoxicity reference value of 76 µg/L is compared with the criteria for long-term aquatic hazard classification, taking into account whether the zinc, the only toxic moiety of concern, is considered rapidly degradable or not.

The concept of “Degradability” was developed for organic substances and is not applicable to inorganic zinc substances. 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”. The rapid removal of zinc from the water column is documented in the sectopn „Environmental fate“. Consequently, zinc is considered as equivalent to being ‘rapidly degradable” in the context of classification for chronic aquatic effects. 

Based on the chronic ecotoxicity reference value of 86 µg/l, zinc cyanurate meets classification criteria of long-term aquatic hazard Category 2 in accordance with Table 4.1.0 (b) (ii) of Regulation (EC) No 1272/2008.