Potassium trifluorozincate

Ecotoxicological Summary

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

General:

For potassium trifluorozincate, reliable acute aquatic toxicity data are available for three trophic levels: algae, invertebrates and fish. The lowest effect value (based on mean measured concentrations) is a 72-h ErC50 of 2.6 mg/L for growth reduction in algae. Two reliable studies on chronic toxicity of potassium trifluorozincate to the aquatic environment are available for two trophic levels: algae and daphnia.

• In the study of growth inhibition of the algae species Pseudokirchneriella subcapitata performed by ECT Oekotoxicologie (2012), a 72-h NOErC of 0.568 mg/L (measured concentration).
• The study on the chronic toxicity of potassium trifluorozincate to invertebrates (APM Shanghai, 2013) reported a 21-Day NOEC for Daphnia magna of 0.059 mg/L (nominal concentration)

It should be noted that the 14-day prolonged fish test is not considered as a chronic test because the sensitive life-stages (juveniles, eggs, larvae) are not exposed. The test is in fact a prolonged acute study with fish mortality as the major endpoint examined.

Using the lowest long term NOEC value (0.059 mg/L) and a default assessment factor of a 50 (default factor in case of two long-term results), the PNECaq for potassium trifluorozincate would be 1.2 µg/L. However, as potassium trifluorozincate in water rapidly dissociates into zinc and fluoride, it is not the substance itself but these ions that are expected to be actually present in the environment and consequently it is these ions for which an environmental risk assessment will be performed (potassium is not assessed due to its environmental abundance and low toxicity). In such a case PNECs for zinc and fluoride can be recalculated based on the molecular weight fractions of these ions in the whole molecule. This would lead to PNECs for zinc and fluoride of 0.48 µg/L and 0.42 µg/L, respectively.

However, for zinc metal and hydrogen fluoride EU risk assessment reports (EU-RAR) in accordance with Council Regulation (EEC) 793/93 on the evaluation and control of the risks of “existing” substances were published (ECB, 2010; ECB, 2001). In the EU-RAR for zinc PNEC values based on freely dissolved zinc have been derived on the basis of ecotoxicity tests with various soluble zinc salts (especially zinc sulfate or zinc chloride), using the “added risk approach” which accounts for background concentrations in ecotoxicity test systems. In the EU-RAR on hydrogen fluoride PNEC values have been derived for freely dissolved fluoride on the basis of ecotoxicity tests performed with sodium fluoride. For fluoride no “added risk approach” was performed. It is however stated that in case of high natural background concentrations, these are taken into consideration when carrying out the risk characterisation.

The PNECs determined in these EU risk assessment reports are based on considerably larger databases and are therefore in most cases considered to be more representative for the zinc and fluoride ions that enter the environment from emission of potassium trifluorozincate. Further detail on derivation of PNECs for zinc and fluoride in the different EU-RAR documents and the applicability of these values for the assessment of these ions from dissociation of potassium trifluorozincate is given below.

 

PNEC freshwater:

 

Zinc:

For the various zinc salts a vast amount of data is available representing a total of 8 taxonomic groups. Based on this database a PNECadd for freshwater of 7.8 µg/L for dissolved zinc in freshwater was derived by statistical extrapolation (Species Sensitivity Distributions). As the short-term effect values observed with potassium trifluorozincate are within the range of short-term effect values (fish, daphnia) and long-term effect values (algae, daphnia) reported for the different zinc salts within the EU-RAR, the PNECadd of 7.8 µg zinc/L for freshwater is considered to be representative for freely dissolved zinc ions from potassium trifluorozincate also.

 

Fluoride:

For sodium fluoride both short-term and long-term ecotoxicity data are available from each of three trophic levels (fish, aquatic invertebrates and algae) representing different taxonomic groups. The entire database does however not allow for derivation of PNECs based on statistical extrapolation and therefore the assessment factor method is applied. After evaluation of all available data, the PNEC for the freshwater compartment is determined on the basis of the calculated mean NOEC value for two 21-d studies with Daphna and application of a default assessment factor of 10 based on the datavailability. This gives a PNEC freshwater of 0.9 mg/L. Overall, the effect values reported for the ecotoxicity studies with sodium fluoride are considerably higher than those observed with potassium trifluorozincate. Based on the entire zinc salts ecotoxicity database however, the lower effect values from the trifluorozincate are most likely to be contributed to the dissociated zinc ion rather than the fluoride ion. Secondly, several of the studies with sodium fluoride were performed with very soft water. Therefore, the PNEC freshwater of 0.9 mg/L derived for the freely dissolved fluoride ion in the EU-RAR for hydrogen fluoride is considered to be representative for the freely dissolved fluoride ions formed from dissociation of (potassium) trifluorozincate.

 

PNEC saltwater:

 

Zinc:

In the EU-RAR on zinc, no PNECadd for saltwater is derived. Instead, the PNECadd for freshwater is applied for both freshwater and for saltwater. For the assessment of zinc from potassium trifluorozincate this approach is adopted and a consequently a PNECadd for saltwater of 7.8 µg zinc/L used in the assessment.

 

Fluoride:

In the EU-RAR for fluoride, short-term and long-term studies with saltwater species are either lacking or have limitations in design and or reporting. A PNEC for marine waters was not derived. As however background concentrations of fluoride are 7-fold higher in seawater than in freshwater, and in addition marine background concentrations are higher that the PNEC aqua of 0.9 mg/L, derivation of a separate PNEC marine is considered to be unnecessary. Instead, the PNEC for freshwater is applied also in assessment of the marine environment. The PNEC marine is determined at 0.9 mg/L.

 

PNEC intermittent:

 

Potassium trifluorozincate released originates from continuous processes and not intermittent (i.e. less than once per month for no more than 24 hours).Therefore, a PNEC intermittent is not derived for zinc and fluoride.

 

PNEC STP:

 

Zinc:

In the EU-RAR for zinc it is concluded that the available data for aquatic microorganisms are insufficient to apply statistical extrapolation. Therefore, the data obtained from the activated sludge respiration inhibition test with potassium trifluorozincate are considered most appropriate for derivation of the PNEC. In this study a 3-h EC50 value of 130 mg/L is determined which is equivalent to 53 mg zinc/L, based on the molecular weight fraction of this ion in the whole molecule. When applying a default assessment factor of a 100, the PNEC STP for zinc is 0.53 mg/L.

 

Fluoride:

In the EU-RAR for fluoride, both short-term and long-term studies with micro-organisms are available. After evaluation of all available data, the PNEC for microorganisms is in the EU-RAR determined based on a 3-h NOEC of 510 mg/L from an activated sludge test and application of a default assessment factor of 10 based on the data used. This gives a PNEC STP of 51 mg/L. Overall, the effect values reported for the microorganisms studies with sodium fluoride are considerably higher than those observed with potassium trifluorozincate. Based on the entire zinc salts microorganism toxicity database however, the lower effect values from the trifluorozincate are most likely to be contributed to the dissociated zinc ion rather than the fluoride ion. Therefore, the PNEC STP of 51 mg/L derived for the freely dissolved fluoride ion in the EU-RAR for hydrogen fluoride is considered to be representative for the freely dissolved fluoride ions formed from dissociation of (potassium) trifluorozincate.

 

PNEC sediment (freshwater):

 

Zinc:

No sediment toxicity data are available for potassium trifluorozincate. In the EU-RAR a PNECadd for sediment of 860 mg zinc/kg d.w. is calculated using the equilibrium partitioning method (EPM) and in parallel a PNECadd for freshwater of 49 mg zinc/kg d.w. is determined based on freshwater sediment toxicity data available from zincdichloride. In the EU-RAR it is concluded that due to limitations of the EPM for derivation of a reliable PNECadd for sediment, especially for metals, preference is to be given to the PNECadd for sediment based on toxicity data with benthic organisms. As this PNECadd sediment is expressed as mg zinc/kg, and

the acute and chronic aquatic effect values observed with potassium trifluorozincate are within the range of the effect values reported for the different zinc salts within the EU-RAR, it is considered justified to use this PNECadd for sediment derived from zincchloride for freely dissolved zinc ions from potassium trifluorozincate also. Thus the PNECadd for freshwater sediment of 49 mg zinc/kg d.w. is used in this assessment.

 

Fluoride:

In the EU-RAR no quantitative risk assessment is carried out for the sediment department as there are no measured data for fluoride levels in sediment and no ecotoxicity data for the compartment. Therefore, a provisional PNEC sediment is calculated using the EPM on the basis of the PNEC freshwater of 0.9 mg/L and the sediment-water partitioning coefficient used in the assessment. For freshwater sediment, the PNEC is 0.766 mg/kg w.w. (3.52 mg/kg d.w.).

 

PNEC sediment (marine water):

 

Zinc:

In the EU-RAR no PNECadd for marine sediment is derived. Instead, the PNECadd sediment for freshwater is applied for both freshwater and for saltwater. For the assessment of zinc from potassium trifluorozincate this approach is adopted and consequently a PNECadd for marine sediment of 49 mg zinc/kg d.w. is used in the assessment.

 

Fluoride:

For the same reasons that for fluoride no separate PNEC for marine water is derived, no separate PNEC for marine sediment is derived. The PNEC for freshwater sediment is applied in both the assessment of the freshwater and saltwater compartment. For marine sediment, the PNEC is 0.766 mg/kg w.w (3.52 mg/kg d.w.).

 

PNEC soil:

 

Zinc:

No soil toxicity data are available for potassium trifluorozincate. For other zinc salts a vast amount of terrestrial toxicity data is available. Based on this database in the EU-RAR for zinc a PNECadd for soil of 26 mg/kg d.w. was derived by statistical extrapolation (Species Sensitivity Distributions). As this PNECadd sediment is expressed as mg zinc/kg, and the acute and chronic aquatic effect values observed with potassium trifluorozincate are within the range of the effect values reported for the different zinc salts within the EU-RAR, it is considered justified to use this PNECadd for sediment derived from zincdichloride for freely dissolved zinc ions from potassium trifluorozincate also. Thus, the PNECadd for soil of 26 mg zinc/kg d.w. is used in the assessment.

 

Fluoride:

In the EU-RAR for fluoride, studies with several different terrestrial macro- and micro-organisms are available. After evaluation of all available data, the PNEC for the soil compartment is in the EU-RAR determined based on a 63-d nitrification study with a NOEC of 106 mg/kg d.w. and a default assessment factor of 10 based on the data used. This gives a PNEC soil of 11 mg kg d.w.. However, in the EU-RAR reference is made to several member state target values for total fluoride in different soils.

The mean fluoride concentration in mineral soil is 200 to 300 mg/kg; whereas that of organic soils is generally lower (97 mg/kg). In the Netherlands the fluoride concentrations in clay soils range from 80 to 700 mg/kg dw. In soils with higher pH values a higher amount of soluble F-complexes is found. Because the variation in background levels throughout Europe is substantial, the Dutch reference value is used. This gives a PNEC soil of 500 mg/kg d.w.

Conclusion on classification

As inorganic compound, potassium trifluorozincate is not biodegraded but abiotic dissociation and subsequent interactions occur instead. Nonetheless, for classification purposes, inorganic substances are to be considered as non-rapidly degradable. Short-term toxicity EC/LC50 values of potassium trifluorozincate for 3 trophic levels are situated between 2.6 mg/L and 9.2 mg/L. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (a), classification for acute aquatic hazard is not required for potassium trifluorozincate as all EC50/LC50 values are above the classification criteria of 1 mg/L.

Long-term toxicity data are available for two trophic levels and range from 0.059 mg/L to 0.568 mg/L for daphnids and algae, respectively. In accordance with Regulation (EC) No 1272/2008, Table 4.1.0 (b) (i), potassium trifluorozincate is to be classified as hazardous to the aquatic environment category Chronic 1; H410 (Very toxic to aquatic life with long lasting effects) since the chronic NOEC values are below the classification criteria of 0.1 mg/L. According to Directive 67/548/EEC for the Classification, Packaging and Labelling of Dangerous Substances, the substance is to be classified as N; R50/53 (Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment).