Zinc hexafluorosilicate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms

Type of information:

other: evidence from degradation product

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: study not according to standard protocol but good quality and considered relevant for microbial ecotoxicity. Culture medium, test water conditions well described and relevant for the PNEC STP.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Lab-designed batch growth system for measurement of inhibition kinetics of activated sludge process.

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

activated sludge

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 d

Test temperature:

25°C

pH:

7+/-0.2

Nominal and measured concentrations:

nominal doses: 1,5,10,20 mg Zn/l

Details on test conditions:

the sludge was shock-dosed with the nominal zinc concnetrations indicated above. Mixed liquor suspended solids measurements were done every 2 hrs.

Reference substance (positive control):

no

Duration:

3 d

Dose descriptor:

NOEC

Effect conc.:

5 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

growth inhibition

Validity criteria fulfilled:

yes

Conclusions:

Test not done according to standard protocol, but of good quality and considered useful for supporting the PNEC for STP.

Executive summary:

Study into the effect of zinc on activated sludge growth kinetics by following the rate of change of biomass production in batch growth experiments. NOEC of 5 mg Zn/l was derived.

Reference 2

Endpoint:

toxicity to microorganisms

Type of information:

other: evidence from degradation product

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: study not according to standard protocol but good quality and considered relevant for the setting of the PNEC-STP. Culture medium, test water conditions well described and relevant.

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Version / remarks:

for the respiration measurements

Qualifier:

equivalent or similar to guideline

Guideline:

other: Swedish EPA report Nr 4424 (1995) for the inhibition of nitrification

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

metal stock solutions were checked for correct metal concentration.

Vehicle:

no

Test organisms (species):

activated sludge

Details on inoculum:

Activated sludge samples for nitrification inhibition and respirometry bioassays were collected from the aeration tank of the Urduliz waste water treatment works (Biskaia, Spain) ("model B").

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20°C

Nominal and measured concentrations:

not indicated

Details on test conditions:

Tests were carried out in 1 L test bottles, containing 0.5 l test solution. Bottles were sealed and the sludge was monitored for 3 hrs by an electrolytic respirometer. Oxygen consumption was measured every 5 minutes for 3 hrs.

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

not specified

Basis for effect:

inhibition of nitrification rate

Details on results:

The following other parameters were also measured but considered of less relevancy for REACH: Vibrio fischeri toxicity test, ATP bioluminescence test (very insenssitive to zinc), enzyme inhibition .

Reported statistics and error estimates:

Error bars are graphically reported, are very small (number of tests respiration: 11; for nitrification inhibition: 10)

Validity criteria fulfilled:

yes

Conclusions:

Tests done according to standard protocol. Good quality and considered relevant for settting the PNEC STP.

Executive summary:

Five rapid direct toxicity assessment methods were used in 3 EU member states. Nitrification inhibition and respiration were measured as REACH-relevant endpoints. The IC50 for respiration was graphically derived as > 10mg Zn/l, the IC50 for nitrification inhibition was 10mg Zn/l.

Reference 3

Endpoint:

activated sludge respiration inhibition testing

Type of information:

other: evidence from degradation product

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

study not according to standard protocol but good quality and considered useful for setting the reference value for acute aquatic ecotoxicity. Study used for that purpose in the EU risk assessment process on zinc (ECB 2008). Culture medium, test water conditions well described and according to the conditions set out in OECD 209.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

not specified

Analytical monitoring:

not specified

Vehicle:

no

Details on test solutions:

test is performed by adding activated sewage sludge to a series of vessels with synthetic sewage medium

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Inoculate originated from a predominantly domestic sewage treatment plant (Rungsted municipal sewage treatment plant , DK). The concentration of sludge in the final test mixture was 1.5g/l of suspended solid.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

pH:

7.5

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

5.2 mg/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Validity criteria fulfilled:

yes

Conclusions:

Tests done under conditions similar to standard protocol. Good quality and used in the EU risk assessment for setting the PNEC for STP.

Executive summary:

Study compares the effect of different substances , e.g. zinc on different microbiological parameters. The EC50 for sludge respiration inhibition was used in the risk assessment for setting the PNEC for STP. Result: see "results " section.

Reference 4

Endpoint:

activated sludge nitrification inhibition testing

Type of information:

other: evidence from degradation product

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

ISO 9509 (Toxicity test for assessing the inhibition of nitrification of activated sludge microorganisms)

GLP compliance:

not specified

Analytical monitoring:

not specified

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge from a municipal wastewater treatment plant

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

4 h

Test temperature:

20°C

pH:

6.5-7.5

Dissolved oxygen:

5-6 mg/L

Nominal and measured concentrations:

between 0-1.2 mg Zn/L.

Reference substance (positive control):

no

Duration:

4 h

Dose descriptor:

other: IC20

Effect conc.:

0.16 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

inhibition of nitrification rate

Duration:

4 h

Dose descriptor:

IC50

Effect conc.:

0.35 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

inhibition of nitrification rate

Duration:

4 h

Dose descriptor:

NOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

element

Basis for effect:

inhibition of nitrification rate

Validity criteria fulfilled:

yes

Conclusions:

Test done according to standard protocol.

Executive summary:

Test done according to standard protocol and considered useful for PNEC derivation for STP.

Description of key information

A nitrification inhibition test with Zn sulfate on activated slugde originating from a municipal wastewater treatment plant was performed leading to a NOEC of  100 µg Zn/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 µg/L

Additional information

The following robust study summary is based on the data presented in the environmental sections of this dossier and adresses solely zinc, zinc oxide and zinc chloride. The environmental hazards of zinc hexafluorosilicate originate exclusively from the zinc ion. Refer to read-across justification for details.

Several data were available for this endpoint. Formerly (ECB 2008), and in the REACH-registrations of a number of zinc substances of November 2010, a PNEC of 52 µg/L for STP was derived, based on the lowest EC50 of 5.2 mg Zn/L observed in a sludge respiration inhibition test (Dutka et al. 1983). According to the guidance (ECHA 7.8.17.1) preference should be given to nitrification inhibition because respiration inhibition is a less sensitive endpoint. A study conducted by Juliastuti et al. (2003) reported a NOEC of 0.1 mg Zn/L in an ISO 9509 nitrification inhibition test. Applying the rules for PNEC setting (ECHA R.10, table R.10.6) this result yields a PNEC STP of 100 µg Zn/L (AF of 1).