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Toxicity to microorganisms

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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:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-standard published study
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Non-standard study investigating effects on bacteria in sewage sludge.
GLP compliance:
no
Remarks:
older, published study
Specific details on test material used for the study:
Sodium sulphate will dissociate under aqueous conditions to form sodium and sulphate ions.
Analytical monitoring:
no
Vehicle:
not specified
Test organisms (species):
activated sludge
Test type:
static
Water media type:
freshwater
Total exposure duration:
40 d
Test temperature:
20-23C
pH:
7-7.5
Dissolved oxygen:
2.3-3.5 mg/L
Nominal and measured concentrations:
concentrations were increased from 10 to 40 g/l over a time period of ca. 40 days. Concentration steps were 10 g/l.
Details on test conditions:
TEST SYSTEM - Concentrations: concentrations were increased from 10 to 40 g/l over a time period of ca. 40 days. Concentration steps were 10 g/l. - Exposure vessel: 10 l - Analyses: effluent analyses were done according to APHA standard methods. - pH: 7 - 7.5 - Temperature: 20 - 23 degree C - Dissolved oxygen: 2.3 - 3.5 mg
Reference substance (positive control):
no
Duration:
30 d
Dose descriptor:
NOEC
Effect conc.:
>= 30 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Validity criteria fulfilled:
not specified
Conclusions:
A NOEC of approximately 30 g/L is reported for sodium sulphate.
Executive summary:

The authoris investigated the effects of salinity on bacteria in sewage sludge. A NOEC of approximately 30 g/L is reported for sodium sulphate, confirming the essentially low toxicity of sulphate to bacteria in sewage sludge.

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:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-standard published study.
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Non-standard study investigating effects on bacteria in sewage sludge
GLP compliance:
no
Remarks:
older published study, pre-dates GLP
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material: Sodium sulphate will dissociate under aquoeus conditions to form sodium and sulphate ions.
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
activated sludge
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
37 d
Test temperature:
18.5-22.5 C
Dissolved oxygen:
6-8 mg/L
Nominal and measured concentrations:
Concentrations: concentrations were increased from 8 to 35 g/l over a time period of 37 days. Concentration steps were 2 - 5 g/l.
Reference substance (positive control):
no
Duration:
37 d
Dose descriptor:
NOEC
Effect conc.:
ca. 26 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

A NOEC of approximately 26 g/L is reported under the conditions of this study.

Validity criteria fulfilled:
not applicable
Conclusions:
A NOEC of approximately 26 g/L is reported for sodium sulphate, incidating that sulphate is essentially non-toxic to activated sludge.
Executive summary:

The authors investigated the effects of inorganic salts (inclduing sodium sulphate) on bacteria in activated sludge. A NOEC of approximately 26 g/L is reported for sodium sulphate, incidating that sulphate is essentially non-toxic to activated sludge.

Endpoint:
toxicity to microorganisms, other
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Published non-standard study investigating pH effects
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Investigation of pH effects in a microcosm study.
GLP compliance:
no
Remarks:
published, non-guideline study
Analytical monitoring:
no
Vehicle:
yes
Test organisms (species):
other: total bacteria
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
5.34 other: pH units
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: pH
Basis for effect:
other: bacterial abundance
Remarks on result:
other: 100 mg/L
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
6.61 other: pH
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: pH
Basis for effect:
other: bacterial abundance
Remarks on result:
other: 88 mg/L

Bacterial abundance decreased at pH levels of 5.34 and less. The concentration of sulphuric acid added to the test systemic to achieve this pH ws 100 mg/L. No effect was seen on bacterial abundance at pH levels of 6.61 and above (88 mg/L).

Validity criteria fulfilled:
not applicable
Conclusions:
Bacteria were shown to be relatively insensitive to the effects of acid pH under the conditions of this study.
Executive summary:

The authors investigated the chronic effects of pH of protozoa, bacteria and algae in a microcosm study using sulphuric acid as a test substance. Bacterial abundance was shown to decrease at pH levels of <= 5.34 (100 mg/L sulphuric aicd), with no effects seen at pH 6.61 (88 mg/L sulphuric acid). Bacteria were shown to be relatively insensitive to the effects of acid pH under the conditions of this study.

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-standard published study
Justification for type of information:
Sulphur trioxide readily reacts with water to form sulphuric acid. The reaction is instantaneous, to the extent that SO3 will react with water vapour in the atmosphere to form fumes of sulphuric acid. This reaction forms the basis of the manufacturing process of H2SO4. The read-across hypothesis is therefore that SO3 will instantaneously transform into H2SO4 upon contact with water (i.e. in aquatic ecotoxicology tests), thus any observed effects will be directly attributable to sulphuric acid. It is therefore justifiable to derive hazard conclusions from sulphuric acid data, with regard to ecotoxicological endpoints.
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Non-standard study investigating effects on bacteria in sewage sludge.
GLP compliance:
no
Remarks:
older, published study
Specific details on test material used for the study:
Available study data for sulphuric acid is being used for read-across to the target substance, sulphur trioxide.
Analytical monitoring:
no
Vehicle:
not specified
Test organisms (species):
activated sludge
Test type:
static
Water media type:
freshwater
Total exposure duration:
40 d
Test temperature:
20-23C
pH:
7-7.5
Dissolved oxygen:
2.3-3.5 mg/L
Nominal and measured concentrations:
concentrations were increased from 10 to 40 g/l over a time period of ca. 40 days. Concentration steps were 10 g/l.
Details on test conditions:
TEST SYSTEM - Concentrations: concentrations were increased from 10 to 40 g/l over a time period of ca. 40 days. Concentration steps were 10 g/l. - Exposure vessel: 10 l - Analyses: effluent analyses were done according to APHA standard methods. - pH: 7 - 7.5 - Temperature: 20 - 23 degree C - Dissolved oxygen: 2.3 - 3.5 mg
Reference substance (positive control):
no
Duration:
30 d
Dose descriptor:
NOEC
Effect conc.:
>= 30 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Validity criteria fulfilled:
not specified
Conclusions:
A NOEC of approximately 30 g/L is reported for sodium sulphate.
Executive summary:

Data on the toxicity to aquatic microorganisms is available for sulphuric acid and is considered suitable for read-across (based on the analogue approach) to the target substance, sulphur trioxide. Sulphur trioxide readily reacts with water to form sulphuric acid. The reaction is instantaneous, to the extent that SO3 will react with water vapour in the atmosphere to form fumes of sulphuric acid. This reaction forms the basis of the manufacturing process of H2SO4. The read-across hypothesis is therefore that SO3 will instantaneously transform into H2SO4 upon contact with water (i.e. in aquatic ecotoxicology tests), thus any observed effects will be directly attributable to sulphuric acid. It is therefore justifiable to derive hazard conclusions from sulphuric acid data, with regard to ecotoxicological endpoints.

The authors investigated the effects of salinity on bacteria in sewage sludge. A NOEC of approximately 30 g/L is reported for sodium sulphate, confirming the essentially low toxicity of sulphate to bacteria in sewage sludge.

Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Non-standard published study.
Justification for type of information:
Sulphur trioxide readily reacts with water to form sulphuric acid or sulphate, with the reaction being instantaneous. The read-across hypothesis is therefore that SO3 will instantaneously transform into H2SO4 or sulphate upon contact with water (i.e. in aquatic ecotoxicology tests), thus any observed effects will be directly driven by pH. It is therefore justifiable to derive hazard conclusions from sulphate data with regard to ecotoxicological endpoints.
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Non-standard study investigating effects on bacteria in sewage sludge
GLP compliance:
no
Remarks:
older published study, pre-dates GLP
Specific details on test material used for the study:
Available study data for disodium sulphate is being used for read-across to the target substance, sulphur trioxide.
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
activated sludge
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
37 d
Test temperature:
18.5-22.5 C
Dissolved oxygen:
6-8 mg/L
Nominal and measured concentrations:
Concentrations: concentrations were increased from 8 to 35 g/l over a time period of 37 days. Concentration steps were 2 - 5 g/l.
Reference substance (positive control):
no
Duration:
37 d
Dose descriptor:
NOEC
Effect conc.:
ca. 26 g/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate

A NOEC of approximately 26 g/L is reported under the conditions of this study.

Validity criteria fulfilled:
not applicable
Conclusions:
A NOEC of approximately 26 g/L is reported for sodium sulphate, incidating that sulphate is essentially non-toxic to activated sludge.
Executive summary:

Data on the toxicity to aquatic microorganisms is available for disodium sulphate and is considered suitable for read-across (based on the analogue approach) to the target substance, sulphur trioxide. Sulphur trioxide readily reacts with water to form sulphuric acid or sulphate, with the reaction being instantaneous. The read-across hypothesis is therefore that SO3 will instantaneously transform into H2SO4 or sulphate upon contact with water (i.e. in aquatic ecotoxicology tests), thus any observed effects will be directly driven by pH. It is therefore justifiable to derive hazard conclusions from sulphate data, with regard to ecotoxicological endpoints.

The authors investigated the effects of inorganic salts (inclduing sodium sulphate) on bacteria in activated sludge. A NOEC of approximately 26 g/L is reported for sodium sulphate, incidating that sulphate is essentially non-toxic to activated sludge.

Endpoint:
toxicity to microorganisms, other
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Published non-standard study investigating pH effects
Justification for type of information:
Sulphur trioxide readily reacts with water to form sulphuric acid. The reaction is instantaneous, to the extent that SO3 will react with water vapour in the atmosphere to form fumes of sulphuric acid. This reaction forms the basis of the manufacturing process of H2SO4. The read-across hypothesis is therefore that SO3 will instantaneously transform into H2SO4 upon contact with water (i.e. in aquatic ecotoxicology tests), thus any observed effects will be directly attributable to sulphuric acid. It is therefore justifiable to derive hazard conclusions from sulphuric acid data, with regard to ecotoxicological endpoints.
Reason / purpose for cross-reference:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Investigation of pH effects in a microcosm study.
GLP compliance:
no
Remarks:
published, non-guideline study
Specific details on test material used for the study:
Available study data for sulphuric acid is being used for read-across to the target substance, sulphur trioxide.
Analytical monitoring:
no
Vehicle:
yes
Test organisms (species):
other: total bacteria
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
21 d
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
5.34 other: pH units
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: pH
Basis for effect:
other: bacterial abundance
Remarks on result:
other: 100 mg/L
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
6.61 other: pH
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: pH
Basis for effect:
other: bacterial abundance
Remarks on result:
other: 88 mg/L

Bacterial abundance decreased at pH levels of 5.34 and less. The concentration of sulphuric acid added to the test systemic to achieve this pH ws 100 mg/L. No effect was seen on bacterial abundance at pH levels of 6.61 and above (88 mg/L).

Validity criteria fulfilled:
not applicable
Conclusions:
Bacteria were shown to be relatively insensitive to the effects of acid pH under the conditions of this study.
Executive summary:

Data on the toxicity to aquatic microorganisms is available for sulphuric acid and is considered suitable for read-across (based on the analogue approach) to the target substance, sulphur trioxide. Sulphur trioxide readily reacts with water to form sulphuric acid. The reaction is instantaneous, to the extent that SO3 will react with water vapour in the atmosphere to form fumes of sulphuric acid. This reaction forms the basis of the manufacturing process of H2SO4. The read-across hypothesis is therefore that SO3 will instantaneously transform into H2SO4 upon contact with water (i.e. in aquatic ecotoxicology tests), thus any observed effects will be directly attributable to sulphuric acid. It is therefore justifiable to derive hazard conclusions from sulphuric acid data, with regard to ecotoxicological endpoints.

The authors investigated the chronic effects of pH of protozoa, bacteria and algae in a microcosm study using sulphuric acid as a test substance. Bacterial abundance was shown to decrease at pH levels of <= 5.34 (100 mg/L sulphuric aicd), with no effects seen at pH 6.61 (88 mg/L sulphuric acid). Bacteria were shown to be relatively insensitive to the effects of acid pH under the conditions of this study.

Description of key information

Available non-standard data for the read-across compound sodium sulphate report NOECs for bacteria in sewage sludge of 26 -30 g/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
26 000 mg/L

Additional information

Sulphate is inherently non-toxic to bacteria and is used by strains of anaerobic bacteria as an energy source. Sulphate reducing bacteria are required for the anaerobic digestion of raw sewage sludge. Sulphate is included as a component of the synthetic sewage feed defined by OECD 209. The toxic effects of SO3 / sulphuric acid will therefore be driven by pH. Available non-standard data for the read-across compound sodium sulphate report NOECs for bacteria in sewage sludge of 26 -30 g/L. Niederlehner & Cairns (1990) investigated the chronic effects of pH of protozoa, bacteria and algae in a microcosm study using sulphuric acid as a test substance. Bacterial abundance was shown to decrease at pH levels of <= 5.34 (100 mg/L sulphuric acid), with no effects seen at pH 6.61 (88 mg/L sulphuric acid). Bacteria were shown to be relatively insensitive to the effects of acid pH under the conditions of this study.