Dizinc pyrophosphate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

respiration test according to OECD 1976

Deviations:

no

Principles of method if other than guideline:

Four short-term microbiological toxicity screening tests were compared using the following test chemicals: 3,5 dichlorophenol, cetyl trimethyl ammonium chloride, sodium lauryl sulfate, phenol, copper(II) sulfate, mercury(II) chloride and zinc(II) sulfate. These seven chemicals represent a wide range of toxicity. The methods examined were Beckman's Microtox system, the Spirillum volutans motility test, inhibition of respiratory activity of activated sludge, and inhibition of activated sludge TTC-dehydrogenase
activity.

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge

Details on inoculum:

- Initial biomass concentration: 1.5 g/L suspended solids
- Source: Rungsted municipal treatment plant, Denmark, treating almost exclusively domestic sewage

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

pH:

The respiration test with activated sludge and the TTC test were carried out at pH 7.5 _+ 0.2 and pH 7.5 + 0.5 respectively.

Reference substance (positive control):

not specified

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

5.2 other: mg Zn/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

6.1 other: mg Zn/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test item was directly added to the test medium and subsequently stirred for 24 hours.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Fresh samples of activated sludge were taken from a sewage treatment plant (Ruhrverband Kläranlage, Schmallenberg, Germany) mainly fed with municipal wastewater.
- Pretreatment: the sludge was washed with isotonic solution. A stock solution of activated sludge in tap water was prepared with a mixed liquor suspended solids level of 4.6 g dry mass sludge/liter. The sludge stock solution was fed with synthetic sewage feed and was
incubated aerated overnight at 20 ± 2 °C in the dark.
- Initial biomass concentration: 1.5 g/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 ± 2 °C.

pH:

8.1 - 8.2

Nominal and measured concentrations:

Nominal test substance concentrations: 10, 100, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flask, 1 L
- Material, fill volume: glass, 500 mL
- Aeration: yes
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 6 + 1 abiotic control


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionized water, free from inhibitory concentrations of toxic substances (e.g. Cu2+ ions)


OTHER TEST CONDITIONS
- Adjustment of pH: yes, buffered to 7.5 ± 0.5 using H2SO4 (50 g/L) solution.


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Microbial respiration rate (total oxygen uptake including heterotrophic and nitrification uptake)

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 1000 mg/L
- Results used to determine the conditions for the definitive study: EC50 > 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

No inhibition of the respiration rate was observed

Results with reference substance (positive control):

EC50: 2 - 25 mg/L.

Inhibition (%) of the respiration rate by the test item

Test item concentration	10 mg/L	100 mg/L	1000 mg/L
Inhibition	-14.1 %	-4.4 %	0.5 %

Validity criteria fulfilled:

yes

Conclusions:

There is no significant inhibition of bacterial respiration by Calcium bis(dihydrogenorthophosphate) up to and including a concentration of 1000 mg/L. The EC50 of the test item is > 1000 mg/L.

Description of key information

EC50 (3 h): 5.2 mg/L (read across).

Key value for chemical safety assessment

EC50 for microorganisms:

5.2 mg/L

Additional information

Data on the toxicity of the target substance Dizinc pyrophosphate to microorganisms are not available. The assessment was therefore based on studies conducted with the source substance calcium bis(dihydrogen orthophosphate) (CAS 7758-23-8) and zinc sulphate (CAS 7733-02-0) as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Further justification is given within the overall summary chapter 6.1 and within the analogue justification in IUCLID section 13.

The effect of zinc on aquatic microorganisms was tested in a study conducted by Dutka et al. (1983). The study investigated the effect of several substances on activated sludge organisms. The test design is comparable to OECD Guideline 209. Zinc sulphate was added to activated sludge and the respiratory activity of the sludge organisms was measured for 3 consecutive hours. An EC50 of 5.2 mg/L was determined for zinc sulphate.

Detrimental effects of phosphate on the respiration rate of microorganism are not expected. The assumption is supported by read across data available for the source substance calcium bis(dihydrogen orthophosphate). The effect of calcium bis(dihydrogen orthophosphate) on the respiration of activated sludge was tested in a study following OECD guideline 209. Activated sludge was exposed to nominal substance concentrations of 10, 100 and 1000 mg/L respectively. The oxygen consumption of the activated sludge was observed for 3 hours. An effect on the respiration rate of the activated sludge was not observed. At test termination an EC10> 1000 mg/L (nominal) was determined.

The EC50 (3 h) of 5.2 mg/L determined for the source substance zinc sulphate is used for further assessment.