Sulphur trioxide

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Published, investigative, non-guideline, non-GLP study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

read-across source

Qualifier:

no guideline available

Principles of method if other than guideline:

A chronic toxicity study was performed with the aquatic midge Tanytarsus dissimilis to determine the effects on growth and reproduction in natural lake water with pH adjustment using sulphuric acid.

GLP compliance:

not specified

Remarks:

older, published study

Analytical monitoring:

yes

Details on sampling:

Not applicable

Vehicle:

no

Details on test solutions:

Test media were prepared using carbon-filtered Lake Superior water. The pH was adjusted using sulphuric acid

Test organisms (species):

other: Tanytarsus dissimilis

Details on test organisms:

The species was selected for use because of its widespread distribution, value as food for fish, ease of rearing in the laboratory and its relatively short life cycle.

Test type:

static

Water media type:

freshwater

Limit test:

no

Remarks on exposure duration:

Three generations in the control

Post exposure observation period:

Not applicable

Hardness:

Test water data (after 35 days), all values in mg/L:
pH 3.0 - 78.0, pH 4.0 - 64.0, pH 5.0 - 54.0, pH 5.5 - 54.0, pH 6.0 - 50.0, pH 7.8 - 50.0

Test temperature:

Test water data (after 35 days), all values in degrees C:
pH 3.0, 4.0, 5.0, 5.5, 6.0 and 7.8 - all were 18.5

pH:

Not applicable

Dissolved oxygen:

Test water data (after 35 days), all values in mg/L:
pH 3.0 - 7.71, pH 4.0 - 8.06, pH 5.0 - 7.93, pH 5.5 - 8.70, pH 6.0 - 8.54, pH 7.8 - 9.01

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal pH values:
pH 3.0, pH 4.0, pH 5.0, pH 5.5, pH 6.0, pH 7.8

Details on test conditions:

A series of different pH were prepared by adjusting the pH of natural, carbon- filtered lake water with sulphuric acid. The following pHs were used:

pH 3.0, 4.0, 5.0, 5.5 and 6.0. Lake water was used as a control and had a pH of 7.8.

Reference substance (positive control):

no

Dose descriptor:

NOEC

Effect conc.:

0.15 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: NOEC duration not specified. The treatment was allowed to continue to obtain three complete generations.

Details on results:

pH 3.0 - all larvae died within 5 days

pH 4.0 - all larvae died within 10 days

pH 5.0 - larvae survived, began pupating after 13 to 17 days, adults failed to emerge within 35 days. Five of the pupal cases were examined, larvae had successfully pupated and adult characteristics were present but the adults were unable to escape from the pupal case. The 10 remaining larvae were kept under test conditions for an additional 10 days and no adults appeared.

pH 5.5 - larve survived, began pupating after 12 to 14 days, adults began to emerge after 27 days, all 15 larvae emerged successfully within 35 day, eggs hatched within 35 days. The treatment was allowed to continue and three complete generations were obtained. The numbers increased from the original 15 to between 500 and 550 larvae.

pH 6.0 - larve survived, began pupating after 12 to 14 days, adults began to emerge after 27 days, all 15 larvae emerged successfully within 35 day, eggs hatched within 35 days. The treatment was allowed to continue and three complete generations were obtained. The numbers increased from the original 15 to between 500 and 550 larvae.

pH 7.8 (control) - larve survived, began pupating after 12 to 14 days, adults began to emerge after 27 days, all 15 larvae emerged successfully within 35 day, eggs hatched within 35 days. The treatment was allowed to continue and three complete generations were obtained. The numbers increased from the original 15 to between 500 and 550 larvae.

Based on the results an NOEC of pH 5.5 (equivalent to 0.15 mg/L) was observed.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

not applicable

Only a brief description of the materials and methods was reported. However, the reported study details indicate that the study was conducted in a scientifically valid way and the results are considered to be reliable.

Validity criteria fulfilled:

not applicable

Remarks:

There were no appropriate study guidelines when the study was conducted.

Conclusions:

Based on the reported information an acceptable assessment of chronic toxicity to aquatic invertebrates was achieved.

Executive summary:

A chronic toxicity study with the midge Tanytarsus dissimilis was conducted. Midge larvae were exposed to a series of test media, carbon-filtered lake water with pH adjustment using sulphuric acid, to varying pHs. At pH 3.0 and 4.0 all of the larvae died within 10 days. At pH 5 larvae pupated but the adults were unable to escape from the pupal case. At pH 5.5 and 6.0 there were no effects on the initial larvae and three complete generations were obtained. The initial 15 larvae increased to between 500 and 550 larvae. The results from the control group (lake water with no adjustment pH 7.8) were the same as in the pH 5.5 and 6.0.

The no-observed effect concentration (NOEC) for T. dissimilis (based on reproduction) exposed to sulphuric acid was observed to be pH 5.5, equivalent to 0.15 mg/L.

Reference 2

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Published, investigative, non-guideline, non-GLP 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:

no guideline available

Principles of method if other than guideline:

A chronic toxicity study was performed with the aquatic midge Tanytarsus dissimilis to determine the effects on growth and reproduction in natural lake water with pH adjustment using sulphuric acid.

GLP compliance:

not specified

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:

yes

Details on sampling:

Not applicable

Vehicle:

no

Details on test solutions:

Test media were prepared using carbon-filtered Lake Superior water. The pH was adjusted using sulphuric acid

Test organisms (species):

other: Tanytarsus dissimilis

Details on test organisms:

The species was selected for use because of its widespread distribution, value as food for fish, ease of rearing in the laboratory and its relatively short life cycle.

Test type:

static

Water media type:

freshwater

Limit test:

no

Remarks on exposure duration:

Three generations in the control

Post exposure observation period:

Not applicable

Hardness:

Test water data (after 35 days), all values in mg/L:
pH 3.0 - 78.0, pH 4.0 - 64.0, pH 5.0 - 54.0, pH 5.5 - 54.0, pH 6.0 - 50.0, pH 7.8 - 50.0

Test temperature:

Test water data (after 35 days), all values in degrees C:
pH 3.0, 4.0, 5.0, 5.5, 6.0 and 7.8 - all were 18.5

pH:

Not applicable

Dissolved oxygen:

Test water data (after 35 days), all values in mg/L:
pH 3.0 - 7.71, pH 4.0 - 8.06, pH 5.0 - 7.93, pH 5.5 - 8.70, pH 6.0 - 8.54, pH 7.8 - 9.01

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal pH values:
pH 3.0, pH 4.0, pH 5.0, pH 5.5, pH 6.0, pH 7.8

Details on test conditions:

A series of different pH were prepared by adjusting the pH of natural, carbon- filtered lake water with sulphuric acid. The following pHs were used:

pH 3.0, 4.0, 5.0, 5.5 and 6.0. Lake water was used as a control and had a pH of 7.8.

Reference substance (positive control):

no

Dose descriptor:

NOEC

Effect conc.:

0.15 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: NOEC duration not specified. The treatment was allowed to continue to obtain three complete generations.

Details on results:

pH 3.0 - all larvae died within 5 days

pH 4.0 - all larvae died within 10 days

pH 5.0 - larvae survived, began pupating after 13 to 17 days, adults failed to emerge within 35 days. Five of the pupal cases were examined, larvae had successfully pupated and adult characteristics were present but the adults were unable to escape from the pupal case. The 10 remaining larvae were kept under test conditions for an additional 10 days and no adults appeared.

pH 5.5 - larve survived, began pupating after 12 to 14 days, adults began to emerge after 27 days, all 15 larvae emerged successfully within 35 day, eggs hatched within 35 days. The treatment was allowed to continue and three complete generations were obtained. The numbers increased from the original 15 to between 500 and 550 larvae.

pH 6.0 - larve survived, began pupating after 12 to 14 days, adults began to emerge after 27 days, all 15 larvae emerged successfully within 35 day, eggs hatched within 35 days. The treatment was allowed to continue and three complete generations were obtained. The numbers increased from the original 15 to between 500 and 550 larvae.

pH 7.8 (control) - larve survived, began pupating after 12 to 14 days, adults began to emerge after 27 days, all 15 larvae emerged successfully within 35 day, eggs hatched within 35 days. The treatment was allowed to continue and three complete generations were obtained. The numbers increased from the original 15 to between 500 and 550 larvae.

Based on the results an NOEC of pH 5.5 (equivalent to 0.15 mg/L) was observed.

Results with reference substance (positive control):

not applicable

Reported statistics and error estimates:

not applicable

Only a brief description of the materials and methods was reported. However, the reported study details indicate that the study was conducted in a scientifically valid way and the results are considered to be reliable.

Validity criteria fulfilled:

not applicable

Remarks:

There were no appropriate study guidelines when the study was conducted.

Conclusions:

Based on the reported information an acceptable assessment of chronic toxicity to aquatic invertebrates was achieved.

Executive summary:

Data on the chronic toxicity to freshwater invertebrates 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.

A chronic toxicity study with the midge Tanytarsus dissimilis was conducted. Midge larvae were exposed to a series of test media, carbon-filtered lake water with pH adjustment using sulphuric acid, to varying pHs. At pH 3.0 and 4.0 all of the larvae died within 10 days. At pH 5 larvae pupated but the adults were unable to escape from the pupal case. At pH 5.5 and 6.0 there were no effects on the initial larvae and three complete generations were obtained. The initial 15 larvae increased to between 500 and 550 larvae. The results from the control group (lake water with no adjustment pH 7.8) were the same as in the pH 5.5 and 6.0.

The no-observed effect concentration (NOEC) for T. dissimilis (based on reproduction) exposed to sulphuric acid was observed to be pH 5.5, equivalent to 0.15 mg/L.

Description of key information

A published paper on the chronic effects of sulphuric acid on a freshwater invertebate, the midge Tanytarsus dissimilis has been summarised and a chronic NOEC obtained.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

0.15 mg/L

Additional information

A chronic toxicity study with the midge Tanytarsus dissimilis was conducted with sulphuric acid. Midge larvae were exposed to a series of test media, carbon-filtered lake water with pH adjustment using sulphuric acid, to varying pHs. At pH 3.0 and 4.0 all of the larvae died within 10 days. At pH 5 larvae pupated but the adults were unable to escape from the pupal case. At pH 5.5 and 6.0 there were no effects on the initial larvae and three complete generations were obtained. The initial 15 larvae increased to between 500 and 550 larvae. The results from the control group (lake water with no adjustment pH 7.8) were the same as in the pH 5.5 and 6.0.

The no-observed effect concentration (NOEC) for T. dissimilis (based on reproduction) exposed to sulphuric acid was observed to be pH 5.5, equivalent to 0.15 mg/L.