Dipotassium disulphate

Endpoint summary

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: This study was selected as the key study because the information provided for the hazard endpoint is sufficient for the purpose of classification and labelling and/or risk assessment.

Reason / purpose for cross-reference:

reference to same study

Principles of method if other than guideline:

A 13-week subchronic oral toxicity study was performed in male and female rats

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

Fischer 344/DuCrj

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Japan
- Age at study initiation: ~6 weeks
- Weight at study initiation: not reported
- Fasting period before study: No
- Housing: 5per plastic cage using soft chips as bedding
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): not reported
- Acclimation period: 1 week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24±1°C
- Humidity (%): 55±5%
- Air changes (per hr): 18
- Photoperiod (hrs dark / hrs light): 12/12

Route of administration:

oral: feed

Vehicle:

unchanged (no vehicle)

Details on oral exposure:

DIET PREPARATION: Food was stored at room temperature until used. Stability was checked for one week at room temperature.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13 Weeks

Frequency of treatment:

Continuously in the diet

Remarks:

Doses / Concentrations:
0.38, 0.75, 1.5, 3%
Basis:
nominal in diet

Remarks:

Doses / Concentrations:
220, 441, 886, 1792 mg/kg/day (males); 239, 484, 961, 1975 mg/kg/day (females)
Basis:
actual ingested

No. of animals per sex per dose:

10/sex/dose

Control animals:

yes, plain diet

Details on study design:

- Dose selection rationale: In a 2-week preliminary study, female F344 rats were administered 5% of the test substance in diet. Significant weight gain suppression and diarrhoea were observed when compared to controls. Based on these findings, the doses selected for the 13-week subchronic toxicity study were 0.38, 0.75, 1.5, and 3%.

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily
- Cage side observations checked : Mortality, behaviour

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Time schedule: Weekly

FOOD EFFICIENCY: No

WATER CONSUMPTION AND COMPOUND INTAKE: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Blood was collected from the aorta abdominalis post mortem (during necropsy)
- Anaesthetic used for blood collection: No
- Animals fasted: No data
- How many animals: All
- Parameters examined: erythrocyte count, haemoglobin, haematocrit, mean cell volume, mean corpuscular haemoglobin content, mean corpuscular haemoglobin concentration, platelet count, leukocyte count

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Blood was collected from the aorta abdominalis post mortem (during necropsy)
- Animals fasted: No data
- How many animals: All
- Parameters examined: total protein, albumin/globulin ratio, albumin, total cholesterol, urea nitrogen, sodium, chloride, potassium, calcium, inorganic phosphorus, glutamat-oxaloacetic transaminase, glutamate-pyruvat transaminase, alkaline phosphatase

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Brain, heart, lungs, liver, kidneys, adrenals, spleen, testes, and thymus were weighed. In addition to these, other main organs were fixed (10% neutral buffered formalin), sectioned, stained (haematoxyline and eosin) and examined histologically.

Statistics:

Variance in data for body weights, haematology, serum biochemistry, and organ weights was checked for homogeneity by the Bartlett test. When the data were homogeneous, one-way analysis of variance (ANOVA) was used. When a significant difference between groups was observed, the Dunnett method was used when the number of animals per group was equal or the Schiff method was used when the number of animals per group was unequal. When dispersion was not equal, the Kruskal-Wallis test was applied and when statistically significant differences were indicated, Dunnett's or Schiff test was employed.

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY: No mortality was observed. Diarrhoea was observed in the males at 3% starting at week 1 continuing throughout the study.

BODY WEIGHT AND WEIGHT GAIN: Body weight gain was significantly decreased in 3% males when compared with controls.
Final mean body weights were significantly decreased in males receiving 0.38%, 1.5% and 3%, and significantly increased in females of the same groups when compared with controls. The changes in the 0.38% group were not dose-related.

FOOD CONSUMPTION: There were no significant differences between the groups for both males and females.

HAEMATOLOGY and CLINICAL CHEMISTRY: The following, statistically significant and dose-related changes were observed:
- decreased leukocyte count (3% males)
- decreased erythrocyte count, haemoglobin, decreased haematocrit, and platelet count (3% females).
- increased mean corpuscular haemoglobin content and mean corpuscular haemoglobin concentration (3% females)
The same changes in haematological parameters were also observed in 1.5% males and females; however, these changes were not dose-related.
Blood serum analysis revealed some statistically significant alterations; however, there was no dose-response. These changes were not considered biologically significant, as they were within the limits of background data and no anomalies were observed in the haematopoietic organs.

ORGAN WEIGHTS: Increased absolute and relative spleen weights (males only) and kidney weights (males and females) were observed at 3%. Relative testis weights were increased at all dose levels and relative liver weight was increased in females at all doses. However, no dose-related trend was observed. Therefore, the authors did not consider these findings adverse or indicative of obvious test substance toxicity.

PATHOLOGY: Histological examination revealed myofibrosis cordis (3% males), basophilia of the renal tubuli (3% males and females), and melanosis of the spleen (3% males and females). However, the incidence of these findings was not statistically significantly different from control.

According to the authors, with exception of the diarrhoea observed in high dose males, none of these observations was considered to indicate obvious toxicity of the test substance.

Dose descriptor:

NOEL

Effect level:

1.5 other: % (886 mg/kg bw/day)

Sex:

male

Basis for effect level:

other: based on diarrhoea observed in 3% males

Dose descriptor:

NOEL

Effect level:

3 other: % (1975 mg/kg/day)

Sex:

female

Basis for effect level:

other: no adverse effects at highest dose tested

Critical effects observed:

not specified

Conclusions:

NOAEL: 1.5% (886 mg/kg/day) for males and 3% (1975 mg/kg/day) for females
This study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).

Executive summary:

A 13-week subchronic oral toxicity study of ammonium sulphate was performed in both sexes of F344 rats by feeding them a CRF-1 powder diet containing concentrations of 0.38, 0.75, 1.5, and 3.0% of the test substance. A control group was fed plain diet. Rats were randomly divided into 5 groups each consisting of 10 males and 10 females. The mean daily doses were 220, 441, 886, 1792 mg/kg bw/day for males, and 239, 484, 961, 1975 mg/kg bw/day for females. Male animals in the 3% group exhibited diarrhoea during the administration period. No changes indicating obvious ammonium sulphate toxicity were observed in the body weights, organ weights, haematological, serum biochemical, or histopathological examinations. Based on these results, the NOEL (no-observed-effect level) of ammonium sulphate for F344 rats was judged to be 1.5% in males (886 mg/kg/day) and 3% in females (1975 mg/kg/day).

Endpoint conclusion

Dose descriptor:

NOAEL

886 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

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

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Principles of method if other than guideline:

Guinea pigs were exposed by inhalation to a number of different pollutants, including sulphuric acid, and various physiological and neurobehavioral effects were assessed.

GLP compliance:

not specified

Limit test:

no

Species:

guinea pig

Sex:

male

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

whole body

Vehicle:

not specified

Remarks on MMAD:

MMAD / GSD: MMAD: < 0.24 -0.5 µm

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: three large (23 m3) walk-in exposure chambers
- System of generating particulates/aerosols: nebulizing heated solutions and injecting the mist into the main airflow
- Air flow rate: Nominal airflow through each of the chambers was 2 m3 /min
- Method of particle size determination: Anderson impactor
- Temperature, humidity, pressure in air chamber: Temp: 20.5 - 26.1 ºC; Hum: 26.5 - 55.1%; pressure not reported

TEST ATMOSPHERE
- Brief description of analytical method used: turbidometric procedure and acid sulphate by titration

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

7, 8 and 14 weeks

Frequency of treatment:

Continuous

Remarks:

Doses / Concentrations:
2.37, 2.49 and 4.05 mg/m3
Basis:
analytical conc.

No. of animals per sex per dose:

10 males/group

Control animals:

yes

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data

BODY WEIGHT: Yes, weekly

FOOD CONSUMPTION: Yes, weekly

WATER CONSUMPTION: Yes, weekly

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At the end of the exposure period, blood chemistry tests were performed.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At the end of the exposure period, blood chemistry tests were performed.

OTHER: Pulmonary function was assessed

Sacrifice and pathology:

GROSS PATHOLOGY: No
HISTOPATHOLOGY: No

Statistics:

All biological parameters were measured after a recovery period in which all groups were exposed to filtered air. The analysis of variance test was
used to analyse all data except the acid·base data, which were analysed using the t test.

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

not examined

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Dose descriptor:

LOEC

Effect level:

> 4.05 mg/m³ air

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No effects at highest dose tested; 7 week exposure, MMAD 0.5 µm

Dose descriptor:

NOEC

Effect level:

4.05 mg/m³ air

Based on:

test mat.

Sex:

male

Basis for effect level:

other: No effects at highest dose tested; 7 week exposure, MMAD 0.5 µm

Critical effects observed:

not specified

Conclusions:

No clinical signs, body weight, food/water consumption, clinical chemistry, or pulmonary effects were observed up to the highest dose tested.
Male Guinea Pig NOEC = 4.05 mg/m3 air

Executive summary:

Male guinea pigs were exposed to submicron particles of sulphuric acid for periods of time of 7 -14 weeks. No clinical signs, body weight, food/water consumption, clinical chemistry, or pulmonary effects were observed up to the highest dose tested. The male guinea pig NOEC was 4.05 mg/m³ air.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Species:

other: rat and guinea pig

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

migrated 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:

other: This study was selected as the key study because the information provided for the hazard endpoint is sufficient for the purpose of classification and labelling and/or risk assessment.

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Deviations:

yes

Remarks:

Exposure for 5 or 28 days; pathology limited to the respiratory tract

GLP compliance:

not specified

Limit test:

no

Species:

rat

Strain:

other: ALPK:APfSD (Wistar)

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
Rats were housed 5 per cage, in multiple rat racks suitable for animals of this strain and the weight range expected during the course of the study.
The rats were transferred to clean cages and racks as necessary during the study. Both temperature and relative humidity were measured and recorded daily and the recorded values were within the specified ranges.
Diet (CT1) supplied by Special Diet Services Limited, Witham, Essex, UK and mains water, supplied by an automatic system, were available ad libitum, except during exposure.
Each batch of diet was routinely analysed for composition and for the presence of contaminants. Water was also periodically analysed for the presence of contaminants. No contaminants were found to be present in the diet or water at levels considered to be capable of interfering with the purpose or outcome of the study. The animals were housed under the experimental conditions for 13 days at CTL, prior to the start of the study. The study was divided into 2 replicates (randomised blocks), each containing 10 cages, one per treatment group. Computer-generated, random number permutations were used to allocate the cages within each replicate to an experimental group.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 ± 3 °C
- Humidity (%): 30–70%
- Air changes (per hr): at least 15 air changes per hour
- Photoperiod (hrs dark / hrs light): 12 h per day of fluorescent light.

Route of administration:

inhalation: aerosol

Type of inhalation exposure:

nose only

Vehicle:

other: unchanged (no vehicle)

Remarks on MMAD:

MMAD / GSD: Particle sizes were 0.62, 0.83 and 0.94 µm, respectively.

Details on inhalation exposure:

The rats were exposed nose-only to the test atmospheres. Animals were restrained in polycarbonate tubes supplied by Battelle, Geneva, Switzerland. These were inserted into a PERSPEX exposure chamber. The chamber was covered with a stainless steel cone and stood on a stainless steel base. The atmosphere was shown to be acceptably stable over approximately 30 minutes before exposure of the test animals. During this period the holes of the exposure chamber were plugged. The animals were exposed for 6 hours per day, 5 days per week, for a period of 28 days. Test atmospheres were generated using a glass concentric - jet atomiser to generate atmospheres into 2 reservoir chambers (each fitted with a cyclone), one serving the exposure chambers for groups 4&5 and 6&7, and another serving exposure chambers for groups 8, 9 & 10. Clean, dry air (dried and filtered using equipment supplied by Atlas-Copco, Sweden) was passed through the atomiser at nominal flow rates for each group respectively and carried the atmosphere to each of the exposure chambers (internal volume of 36.8 litres), in order to achieve a minimum of 12 air changes per hour. Air flows were monitored and recorded at approximately 30 minute intervals using variable area flowmeters (KDG Flowmeters, Burgess Hill, Sussex, UK) and were altered as necessary to maintain the target concentrations.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The particulate concentration of each test atmosphere, close to the animals’ breathing zone, was measured gravimetrically at least twice during exposure. This was done by drawing each test atmosphere, at a known flow rate, for a known time, through a 25 mm diameter, polyvinyl chloride (PVC) GN-4 filter housed in a Delrin open-faced filter holder (both filters and holders supplied by Gelman Sciences Limited, Northampton, UK). The filter was weighed before and after the sample was taken. The aerodynamic particle size distribution of each test atmosphere was measured at least once during exposure period, using a Marple Cascade Impactor (supplied by Schaeffer Instruments Limited, Wantage, Oxon, UK) which aerodynamically separates airborne particles into pre-determined size ranges. The amount of aerosol, by weight, in each size range, was then used to calculate the aerodynamic particle size distribution of the aerosol. Using a microcomputer, the data were transformed using a log/probit transform and a linear regression derived from the cumulative data.
Using this regression line, the mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were calculated.

Duration of treatment / exposure:

5 or 28 days

Frequency of treatment:

6 hours/day; 5 days/week

Remarks:

Doses / Concentrations:
0.00, 0.2, 1.0, 5.0 mg/m3
Basis:
nominal conc.

Remarks:

Doses / Concentrations:
0.00, 0.30. 1.38, 5.52 mg/m3
Basis:
analytical conc.

No. of animals per sex per dose:

10 females

Control animals:

yes, concurrent no treatment

Observations and examinations performed and frequency:

For examination of effects in the lung, 5 designated rats per group, per time point, were implanted subcutaneously with osmotic minipumps (Alzet 2ML1) for delivery of BrdU 7 days before termination. The minipumps contained BrdU at a concentration of 15 mg/mL.
At post mortem, the lungs (tracheas attached but larynx removed) were excised and weighed, prior to inflation with 10% neutral buffered formalin. The lungs were fixed in 10% neutral buffered formalin for 24 hours. The tissue was trimmed and processed to paraffin wax blocks and sections made and stained to reveal BrdU positive nuclei. Labelling indices (LI) were determined for the central acinar region and in the terminal bronchiole regions of the lung. LI were determined by counting the number of BrdU labelled cell nuclei and the total number of cell nuclei (labelled and non labelled). LI were then determined by dividing the number of BrdU labelled cells by the total number of labelled and non labelled cells, the result being expressed as a percentage. Labelling indices were determined for the small intestine. The small intestine has an inherently high rate of cell turnover and as such acts as a positive control for the BrdU immunostaining. Pulse labelling with tritiated thymidine, followed by autoradiography, was used for the assessment of rate of cell proliferation in the nasal passages; thymidine being incorporated into DNA during s-phase.
Five designated rats per group were injected intra-peritoneally with tritiated thymidine at a dose level of 1µCi/g body weight, approximately one hour prior to scheduled termination. At post mortem, the heads from all designated animals were removed, excess skin and muscle removed, the brain excised and the nasal cavity perfused with 10% formol saline through the nasopharynx. The head was then immersed in formol saline followed by decalcification with 20% formic acid. After processing, six standard sections were produced to include all different epithelial cell types and accessory nasal structures. The six sections were exposed to nuclear emulsion (Ilford K2) for 8-10 weeks. Sections were developed and examined by light microscopy. Labelling indices (LI) were determined for each of the 6 nasal passage levels. LI were determined by counting the number of thymidine labelled cell nuclei and the total number of cell nuclei (labelled and non labelled). LI were then determined by dividing the number of thymidine labelled cells by the total number of labelled and non labelled cells, the result being expressed as a percentage. Where more than one section was examined from a tissue, results for each level of that tissue are reported separately.

Sacrifice and pathology:

From all animals surviving to scheduled termination (day 29 for main study animals and after 4 or 8 weeks monitoring in recovery animals), the lungs were removed, trimmed free of extraneous tissue and weighed (with trachea attached but larynx removed, each pair of lungs weighed together). At post mortem the larynx was removed from all animals and fixed in 10% neutral buffered formalin for 24 hours. The tissues were trimmed and processed to paraffin wax blocks and three standard sections of larynx produced, taken at the level of the base of the epiglottis, through the ventral pouch and the cricoid cartilage to include all different epithelial cell types of the larynx and underlying seromucinous glands.
Standard sections of larynx from animals receiving BrdU were stained to reveal BrdU positive nuclei, while those from animals receiving thymidine, were exposed to nuclear emulsion (Ilford K2) for 8-10 weeks before being developed. For both the BrdU and thymidine animals, cell replication rates in the larynx were expressed as unit length labelling indices (ULLI).
In ULLI’s, the basement membrane length is substituted for the total cell count in the labelling index equation. ULLI’s were determined by counting the number of BrdU (and thymidine) labelled nuclei and dividing the result by the length of underlying basement membrane; ULLI’s being expressed as the number of BrdU (or thymidine) labelled cells per unit length (mm) of epithelium. The length of the basement membrane was determined using a Kontron Image Analyser attached to a Leitz light microscope.

Statistics:

All data (except cell proliferation data) were evaluated using analysis of variance and/or covariance for each specified parameter using the MIXED procedure of the SAS Institute (1989) and were carried out separately for the main study and for recovery animals. Cell proliferation data was analysed using ARTEMIS statistical methods (two-sided Student’s test).

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEC

Effect level:

0.3 mg/m³ air (analytical)

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Findings at 0.3 mg/m3 were limited to minimal metaplastic change after 28 days, considered to be an adaptive response to a respiratory irritant.

Critical effects observed:

not specified

There were no deaths, no signs of toxicity, and no adverse effects on body weight or lung weight in any treatment group. There were no macroscopic findings in animals killed at term. Microscopically, no treatment related changes were seen in either the lung or the nasal cavity. The major treatment related effect was squamous metaplasia of the ventral epithelium of level 1 of the larynx, the severity of which was concentration-dependent. In the 5-day satellite study, the NOAEC for this effect was 0.30 mg/m³. In the 28-day study, squamous metaplasia of the larynx was seen at all concentrations (including minimal squamous metaplasia in 3/10 animals exposed to 0.30 mg/m³); the severity of this finding was directly related to exposure concentration. After 4 and 8 weeks recovery following exposure to the highest concentration (5.52 mg/m³) evidence of metaplasia remained, although it was less severe than that seen immediately following the 28-day exposure period. No increases in cell proliferation were detected in either the lung or the nasal cavity at either 5 or 28 days; results were in agreement with the pathological assessment. In the larynx, a treatment related increase in cell turnover was seen in the same region of level 1 as the exposure related pathological finding of squamous metaplasia, with a NOAEC for this finding of 0.30 mg/m³ for both 5 and 28 days.

Conclusions:

This study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).

Female NOAEC = 0.3 mg/m³ air (analytical)
Following inhalation exposure to sulphuric acid mists, treatment-related findings were limited to histopathology and cell proliferation of the larynx, consistent with a local irritant effect of the substance

Executive summary:

Groups of female rats were exposed to aerosols of sulphuric acid (mists) at target concentrations of 0, 0.2, 1.0 or 5.0 mg/m³ for 6 hours a day, 5 days a week for 5 or 28 days. Additional groups exposed to 0 or 5.0 mg/m³ (nominal concentration) for 28 days were investigated following recovery periods of 4 or 8 weeks. Effects of exposure were limited to the larynx. Squamous metaplasia and significant cell proliferation was seen following exposure to 1.38 and 5.52 mg/m³ for 5 and 28 days; findings had decreased in severity following the recovery periods. Findings following exposure to 0.3 mg/m³ for 28 days were limited to minimal metaplasia (with no proliferation); no effects were apparent following exposure to 0.3 mg/m³ for 5 days. The NOAEC for this study is therefore considered to be 0.3 mg/m³.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

0.3 mg/m³

Species:

rat

Quality of whole database:

Scientifically valid study

Repeated dose toxicity: dermal - systemic effects

Endpoint conclusion

Endpoint conclusion:

no study available

Repeated dose toxicity: dermal - local effects

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No data were available for repeated dose toxicity with the test substance, but inhalation studies in rats and guinea pigs with H₂SO₄ and oral studies in rats with Na₂SO₄ and (NH₄)₂SO₄ were used as a read across to fulfil the data gap for the test substance. The underlying hypothesis for the read-across between the test substance and H₂SO₄, Na₂SO_4,and (NH₄)₂SO₄ is the likelihood of common precursors and/or breakdown products, via physical or biological processes, which result in structurally similar chemicals (e.g. the metabolic pathway approach of examining related chemicals such as acid/ester/salt). Additional documentation, provided within the IUCLID Assessment Reports section, supports the read-across approach. Because the test hydrolysis generates corrosive H₂SO₄, local effects from repeated inhalation exposure are considered to be the primary consequence of inhalation exposure to test substance dusts. Several inhalation studies with H₂SO₄ are available to assess this particular endpoint. In addition to the local effects of the test substance on the respiratory tract, consideration was given to sulphate anion and its systemic toxicity in evaluating which endpoint, i.e., local versus systemic toxicity is more relevant for repeated exposure.

A combined repeated dose and reproductive/developmental screening study according to OECD 421 was performed using Na₂SO₄. Na₂SO₄ was administered in highly purified water at 0, 100, 300, and 1000 mg/kg body weight/day to male rats for at least 28 days and to female rats for 14 days prior to pairing, through the pairing and gestation periods until the F1 generation reached day 4 post partum. In absence of any effect, the NOEL was established at 1000 mg/kg/day.

Chronic toxicity and carcinogenicity studies of (NH₄)₂SO₄ were performed in male and female rats at dietary concentrations of 0, 0.1, 0.6, and 3% in a 52-week toxicity study and 0, 1.5, and 3% in a 104-week carcinogenicity study. Treatment with the test substance caused significant increase in kidney and/or liver weights in males and females of the 3% diet group, but no effects were found on survival rate, body weights, and haematological, serum biochemical, or histopathological parameters at any dose levels in the chronic toxicity study. Regarding carcinogenicity, the test substance did not exert any significant influence on the incidences of tumours in any of the organs and tissues examined. It was concluded that the no observed adverse effect level was 0.6% diet, which is equivalent to 256 and 284 mg/kg/day in males and females, respectively, and the test substance is non-carcinogenic under the conditions of the study.

A 13-week subchronic oral toxicity study of (NH₄)₂SO₄ was performed in both sexes of F344 rats by feeding them a CRF-1 powder diet containing concentrations of 0.38, 0.75, 1.5, and 3.0% of the test substance. A control group was fed plain diet. Rats were randomly divided into 5 groups each consisting of 10 males and 10 females. The mean daily doses were 220, 441, 886, 1792 mg/kg bw/day for males, and 239, 484, 961, 1975 mg/kg bw/day for females. Male animals in the 3% group exhibited diarrhoea during the administration period. No changes indicating obvious (NH₄)₂SO₄ toxicity were observed in the body weights, organ weights, haematological, serum biochemical, or histopathological examinations. Based on these results, the NOEL (no-observed-effect level) of (NH₄)₂SO₄ for F344 rats was judged to be 1.5% in males (886 mg/kg/day) and 3% in females (1975 mg/kg/day).

Groups of female rats were exposed to aerosols of H₂SO₄ (mists) at target concentrations of 0, 0.2, 1.0 or 5.0 mg/m³ for 6 hours a day, 5 days a week for 28 days. Additional groups exposed to 0 or 5.0 mg/m³ (nominal concentration) for 28 days were investigated following recovery periods of 4 or 8 weeks. Effects of exposure were limited to the larynx. There were no deaths, no signs of toxicity, and no adverse effects on bodyweight or lung weight in any treatment group. There were no macroscopic findings in animals killed at term. Microscopically, no treatment related changes were seen in either the lung or the nasal cavity. Squamous metaplasia of the larynx and significant cell proliferation was seen following exposure to 1.38 and 5.52 mg/m³ for 28 days; but findings had decreased in severity following the recovery periods. Findings following exposure to 0.3 mg/m³ for 28 days were limited to minimal metaplasia (with no proliferation) and were considered to be an adaptive response of the tissue from exposure to an irritant aerosol. The NOAEC for this study is therefore considered to be 0.3 mg/m³.

Male rats and guinea pigs were exposed to submicron particles of H₂SO₄ for 6 -14 weeks. Pulmonary function pulmonary function studies indicated that H₂SO₄ exposure caused increased pulmonary resistance, respiration rate, compliance and a decrease of tidal volume in young and adult rat (but not in guinea pigs). Effects on blood gas parameters are likely, were not seen consistently, but may be secondary to exposure; inconsistent effects on spontaneous locomotor activity are of unclear toxicological significance.

In a 7-week exposure experiment to 4.05 mg/m³ H₂SO₄ (MMAD: 0.5 µm), no effects were observed on food and water consumption, bodyweight or activity level, learning activity or acid-base parameters. However, pulmonary function studies indicated that H₂SO₄ exposure caused increased pulmonary resistance, respiration rate, compliance and a decrease of tidal volume in young and adult rats. In an 8-week experiment to H₂SO₄ (2.49 mg/m³; MMAD: 0.24 µm), rats showed a decreased spontaneous locomotor activity and slower treadmill performance than controls. No impairment of lung function and no alteration of blood gas parameters were observed. Spontaneous locomotor activity, learning behaviour and pulmonary functions and blood gas parameters were not affected by exposure to 2.37 mg/m³ sulphuric acid (MMAD: 0.5 µm) for 14 weeks. The NOEC in male rats was 2.37 mg/m³ air. No effects were observed in the guinea pigs; therefore, the NOEC in male guinea pigs was 4.05 mg/m³.

Toxicity to H₂SO₄ is confined to changes in the structure and function of the respiratory tract suggesting it has a local effect and no systemic effects. The observed changes are related to the irritant properties of H₂SO₄ and are most likely due to the corrosivity of locally high concentrations of hydronium ion. Therefore, for hazard assessment, the H₂SO₄ NOAEC of 0.3 mg/m³ is a conservative read-across value for purposes of assessing local (respiratory tract) toxicity for the repeated exposure endpoint.

Justification for selection of repeated dose toxicity via oral route - systemic effects endpoint:
Scientifically valid study

Justification for selection of repeated dose toxicity inhalation - systemic effects endpoint:
In addition to the 90-day study in rats with H2SO4,a scientifically valid study in guina pigs with H2SO4 has been identified as pertinent to the hazard conclusion for this endpoint.

Justification for selection of repeated dose toxicity inhalation - local effects endpoint:
Scientifically valid study

Justification for classification or non-classification

Concentrated related pathological changes in the laryngeal epithelium of rats at all tested concentrations were observed in a repeat exposure inhalation study with the read-across chemical, H₂SO₄, but no pathology in the nose or lungs was observed. Laryngeal injury at 0.3 mg/m³ H₂SO₄ was considered to be an adaptive response to an irritant aerosol while exposure at 1.38 mg/m³ or greater was associated with more severe histopathology and cell proliferation changes. Other animal data indicate that H₂SO₄ impairs pulmonary function and or respiratory tract particle clearance at exposure concentrations under 10 mg/m³. These data indicate that effects resulting from inhalation of H₂SO₄ are confined to changes in the structure and function of the respiratory tract due to local tissue injury. Although repeated exposure respiratory effects with H₂SO₄ are below the concentration threshold for classification (STOT-RE), they are consistent with those seen in animals after single exposure to H₂SO₄ at comparable concentrations (SCOEL, 2007).Thus, repeated exposure toxicity with H₂SO₄ is considered to be due to local, concentrated-dependent injury from a corrosive substance. Since the notified substance hydrolyses in contact with biological fluids, generating H₂SO₄, respiratory effects from it are expected to be comparable to those of H₂SO₄. For these reasons, no classification for repeat exposure is required according to the EU Directive 67/548/EEC and EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008.