Sulphur trioxide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06.12.2008-15.01.2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples and observations made after 24 and 48 hours.

Vehicle:

no

Details on test solutions:

To produce the only test concentration 105.5 mg of the test item was added to 1 litre of dilution water. The pH was measured to be pH 4.0 and was adjusted to pH 8.0. with 1 M sodium hydroxide solution. 19 mL of the stock solution was taken and diluted with 1 mL dilution water containing 10 daphnids resulting in a final concentration of 100 mg/L. For each test item concentration and control 2 replicates were prepared.

Test organisms (species):

Daphnia magna

Details on test organisms:

A population of parthenogenetic females of synchronized age structure has been maintained for more than 15 years in the test facility under constant temperature conditions (20 +/- 1 °C) at a 16 : 8 hour light-dark photoperiod (illumination: < 1000 lux). The culture water (so-called 'M4 medium') was partly renewed once a week. The Daphnia were exclusively fed with unicellular green algae (Desmodesmus subspicatus) 'ad libitum'. Mortalities of parent Daphnia during the culture period were recorded daily in a semi-quantitative way. The neonates were separated from their parent Daphnia by filtration prior to the acute test.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Post exposure observation period:

Not applicable

Hardness:

Not reported

Test temperature:

During the test a temperature range of 18 - 22°C was maintained in the test vessels, with a maximum temperature fluctuation of +/- 1°C in each individual test.

pH:

All samples are maintained at pH 8.0

Dissolved oxygen:

The concentration remained above 3 mg/L throughout the exposure period.

Salinity:

Not reported

Nominal and measured concentrations:

100 mg/L

Details on test conditions:

Photoperiod; 16 h light and 8 h dark.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Daphnia were exposed to the test item added to water at a limit test concentration of nominally 100 mg/L for a period of 48 hours. At this concentration no toxic effects against Daphnia were observed at the end of the 48 hour study period. Immobilisation rates were recorded at 24-hour intervals. Analysis of the immoblisation rates gave an EC 50 value of >100 mg/L at both 24 and 48 h.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Not reported

The results collected are summarised below in tables 1 and 2. Analysis of the immobilisation rates showed that there was no toxic effect on Daphnia when exposed to the test item at a concentration of 100 mg/L. No abnormalities were noted.

Table 1: Control

 

Abiotic parameters	24 h	48 h
Temperature [°C]	-----	20.6
Oxygen [mg/L]	-----	8.5
Oxygen [% saturation]	-----	96
pH value	-----	7.8
Immobilisation	24 h	48 h
Absolute	0	0
Cumulative	0	0
Cumulative [%]	0	0
Abnormalities *	24 h	48 h
Abnormal colouration	0/20	0/20
Abnormal swimming behaviour	0/20	0/20
Chemical analysis	0 h	48 h
Sulfate replicates [mg/L]	5.267 / 5.265 # 51.356 / 51.315	51.356/51.315

Comments: * Daphnia with effects / Daphnia, 
                  + = all Daphnia immobile

# The values at 0 h were declared as outliers. The values after 48 h of exposure equal the values of the pre-test (51 mg/L) and the theoretical amount of sulfate content of 48 mg/L in the dilution water. Therefore the values after 0 h were replaced with the values after 48 h exposure for further calculations.

Table 2: 100 mg/L

 

Abiotic parameters	24 h	48 h
Temperature [°C]	-----	20.3
Oxygen [mg/L]	-----	8.6
Oxygen [% saturation]	-----	96
pH value	-----	7.9
Immobilisation	24 h	48 h
Absolute	0	0
Cumulative	0	0
Cumulative [%]	0	0
Abnormalities *	24 h	48 h
Abnormal colouration	0/20	0/20
Abnormal swimming behaviour	0/20	0/20
Chemical analysis	0 h	48 h
Sulfate replicates [mg/L]	102.253/103.352	99.512/99.870
Sulfate mean values [mg/L]	102.803	99.691
Corrected Sulfate values [mg/L](1)	51.467	48.356
Test item [mg/L]	52.547	49.370

Comments: According to the product informations, 1 mg/L sulfate equals 
                    1.0210 mg/L of the test item (structural formula: H₂SO₄,molecular
                    weight: 98.074 g/moL).

*Daphniawith effects /Daphniamobile, + = allDaphnia immobile

 ₍₁₎corrected for control values

Validity criteria fulfilled:

yes

Remarks:

The immobilisation and other abnormalities in the controls did not exceed 10% by the end of the test. The dissolved oxygen concentration remained above 3 mg/L throughout the exposure period.

Conclusions:

The 48 hour EC50 for Daphnia magna exposed to sulfuric acid was observed to be >100 mg/L (the highest concentration tested).

Executive summary:

Daphnia were exposed to a limit test concentration of nominally 100 mg/L Sulfuric acid dissolved in water. Observations were made on the swimming ability and the immobilisation rate, respectively, after 24 and 48 hours of exposure. There were no observed toxic effects on Daphnia at the limit concentration of 100 mg/L after 48 hours.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

06.12.2008-15.01.2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline 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:

reference to same study

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

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:

yes

Details on sampling:

Samples and observations made after 24 and 48 hours.

Vehicle:

no

Details on test solutions:

To produce the only test concentration 105.5 mg of the test item was added to 1 litre of dilution water. The pH was measured to be pH 4.0 and was adjusted to pH 8.0. with 1 M sodium hydroxide solution. 19 mL of the stock solution was taken and diluted with 1 mL dilution water containing 10 daphnids resulting in a final concentration of 100 mg/L. For each test item concentration and control 2 replicates were prepared.

Test organisms (species):

Daphnia magna

Details on test organisms:

A population of parthenogenetic females of synchronized age structure has been maintained for more than 15 years in the test facility under constant temperature conditions (20 +/- 1 °C) at a 16 : 8 hour light-dark photoperiod (illumination: < 1000 lux). The culture water (so-called 'M4 medium') was partly renewed once a week. The Daphnia were exclusively fed with unicellular green algae (Desmodesmus subspicatus) 'ad libitum'. Mortalities of parent Daphnia during the culture period were recorded daily in a semi-quantitative way. The neonates were separated from their parent Daphnia by filtration prior to the acute test.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Post exposure observation period:

Not applicable

Hardness:

Not reported

Test temperature:

During the test a temperature range of 18 - 22°C was maintained in the test vessels, with a maximum temperature fluctuation of +/- 1°C in each individual test.

pH:

All samples are maintained at pH 8.0

Dissolved oxygen:

The concentration remained above 3 mg/L throughout the exposure period.

Salinity:

Not reported

Nominal and measured concentrations:

100 mg/L

Details on test conditions:

Photoperiod; 16 h light and 8 h dark.

Reference substance (positive control):

no

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

Daphnia were exposed to the test item added to water at a limit test concentration of nominally 100 mg/L for a period of 48 hours. At this concentration no toxic effects against Daphnia were observed at the end of the 48 hour study period. Immobilisation rates were recorded at 24-hour intervals. Analysis of the immoblisation rates gave an EC 50 value of >100 mg/L at both 24 and 48 h.

Results with reference substance (positive control):

Not applicable

Reported statistics and error estimates:

Not reported

The results collected are summarised below in tables 1 and 2. Analysis of the immobilisation rates showed that there was no toxic effect on Daphnia when exposed to the test item at a concentration of 100 mg/L. No abnormalities were noted.

Table 1: Control

 

Abiotic parameters	24 h	48 h
Temperature [°C]	-----	20.6
Oxygen [mg/L]	-----	8.5
Oxygen [% saturation]	-----	96
pH value	-----	7.8
Immobilisation	24 h	48 h
Absolute	0	0
Cumulative	0	0
Cumulative [%]	0	0
Abnormalities *	24 h	48 h
Abnormal colouration	0/20	0/20
Abnormal swimming behaviour	0/20	0/20
Chemical analysis	0 h	48 h
Sulfate replicates [mg/L]	5.267 / 5.265 # 51.356 / 51.315	51.356/51.315

Comments: * Daphnia with effects / Daphnia, 
                  + = all Daphnia immobile

# The values at 0 h were declared as outliers. The values after 48 h of exposure equal the values of the pre-test (51 mg/L) and the theoretical amount of sulfate content of 48 mg/L in the dilution water. Therefore the values after 0 h were replaced with the values after 48 h exposure for further calculations.

Table 2: 100 mg/L

 

Abiotic parameters	24 h	48 h
Temperature [°C]	-----	20.3
Oxygen [mg/L]	-----	8.6
Oxygen [% saturation]	-----	96
pH value	-----	7.9
Immobilisation	24 h	48 h
Absolute	0	0
Cumulative	0	0
Cumulative [%]	0	0
Abnormalities *	24 h	48 h
Abnormal colouration	0/20	0/20
Abnormal swimming behaviour	0/20	0/20
Chemical analysis	0 h	48 h
Sulfate replicates [mg/L]	102.253/103.352	99.512/99.870
Sulfate mean values [mg/L]	102.803	99.691
Corrected Sulfate values [mg/L](1)	51.467	48.356
Test item [mg/L]	52.547	49.370

Comments: According to the product informations, 1 mg/L sulfate equals 
                    1.0210 mg/L of the test item (structural formula: H₂SO₄,molecular
                    weight: 98.074 g/moL).

*Daphniawith effects /Daphniamobile, + = allDaphnia immobile

 ₍₁₎corrected for control values

Validity criteria fulfilled:

yes

Remarks:

The immobilisation and other abnormalities in the controls did not exceed 10% by the end of the test. The dissolved oxygen concentration remained above 3 mg/L throughout the exposure period.

Conclusions:

The 48 hour EC50 for Daphnia magna exposed to sulfuric acid was observed to be >100 mg/L (the highest concentration tested).

Executive summary:

Data on the acute toxicity to the freshwater invertebrate, Daphnia magna, 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.

Daphnia were exposed to a limit test concentration of nominally 100 mg/L Sulfuric acid dissolved in water. Observations were made on the swimming ability and the immobilisation rate, respectively, after 24 and 48 hours of exposure. There were no observed toxic effects on Daphnia at the limit concentration of 100 mg/L after 48 hours.

Description of key information

An OECD 202 Guideline study on the acute toxicity of sulphuric acid on Daphnia magna is available, which showed no observed toxic effect at the limit concentration of 100 mg/L after 48 hours.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

> 100 mg/L

Additional information

Read-across from studies performed with sulphuric acid is proposed.

Daphnia were exposed to a limit test concentration of nominally 100 mg/L Sulfuric acid dissolved in water. Observations were made on the swimming ability and the immobilisation rate, respectively, after 24 and 48 hours of exposure. There were no observed toxic effects on Daphnia at the limit concentration of 100 mg/L after 48 hours.