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Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
No data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The reaction mass of sulphuric acid, hydrogen peroxide and peroxomonosulphuric acid is predominantly sulphuric acid (>80%). Although all constituents of the reaction mass contribute towards and are essential for the desired technical effects of the range, it is considered acceptable to read-across to data on sulphuric acid. This because significant toxicological effects are likely to be masked in the multi-constituent substance by its corrosive nature and so it considered appropriate to read across to the mean constituent, sulphuric acid, when considering long-term inhalation toxicity.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
See read-across data matrix under 'Attached background material' below.

3. ANALOGUE APPROACH JUSTIFICATION
See read-across data matrix under 'Attached background material' below.

4. DATA MATRIX
See read-across data matrix under 'Attached background material' below.

Data source

Reference
Reference Type:
publication
Title:
Long-term exposure to sulfur dioxide, sulfuric acid mist, fly ash, and their mixtures
Author:
Alarie YC, Krumm AA, Busey WM, Ulrich CE & Kantz RJ II
Year:
1975
Bibliographic source:
Arch Environ Health. 30: 254-262

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Groups of cynomolgus monkeys were exposed to mixtures of sulphur dioxide, fly ash and sulphuric acid mist.
GLP compliance:
no
Remarks:
Study pre-dates GLP
Limit test:
no

Test material

Constituent 1
Reference substance name:
Sulphuric acid, sulphur dioxide and fly ash; alone and in combination
IUPAC Name:
Sulphuric acid, sulphur dioxide and fly ash; alone and in combination
Test material form:
aerosol dispenser: not specified
Remarks:
migrated information: aerosol
Details on test material:
SULPHUR DIOXIDE
- Generation of the desired concentration of sulphur dioxide was from cylinders of 1 % or 5 % sulphur dioxide in nitrogen.
- Known amounts of the gas mixtures were metered into the incoming air and the concentration was frequently monitored by a flame ionisation sulphur dioxide analyser.

SULPHURIC ACID MIST
- Two different systems were used to generate sulphuric acid mist.
- To generate large particles, concentrated sulphuric acid was physically shattered liquid into small droplets by the use of a nebuliser.
- Small particles were generated by bubbling dry air through fuming sulphuric acid and allowing to mix prior to entry into the chambers.

FLY ASH
- Fine fly ash was obtained by high volume sampling from four large coal-buring electric generating plants in the eastern United States.
- The fly ash was collected downstream from the electrostatic precipitators at each plant, and the four samples obtained were mixed into a composite sample and determined spectrographically.
- Fly ash was introduced into the inlet stream of each chamber by means of a dust-feed mechanism.

Test animals

Species:
primate
Strain:
other: Cynomolgus (Macaca irus)
Sex:
male/female
Details on test animals or test system and environmental conditions:
- Young cynomolgus monkeys wighing 1.9 to 5.3 kg were individually caged and held in a quarantine area for eight weeks.
- Animals were tested twice for tuberculosis during the quarantine period and then transported to laboratory animal holding rooms where they were observed for a period of two weeks.
- During the following 8 to 12 weeks, animals were re-tested for tuberculosis and a chest roentgenogrph was taken.
- Animals were screened via evaluation of pulmonary function, electrocardiogram, haemotologic testing and chemical analyses.
- Animals exibiting normal values were accepted.
- During this period, animals were also placed in a restraining chair with face mask to adapt them to pulmonary function testing procedures.
- Animals accepted for studies were then transferred to individual exposure cages and placed in stainless steel and glass chambers.
- Air supplied to each exposure chamber passed through a charcoal bed and absolute filter.
- Temperature was maintained at 22.2 ± 1.1 °C.
- Relative humidity was maintained at 50 ± 5 %
- Airflow through each chamber was slightly in excess of 1000 L/min.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
whole body
Vehicle:
other: water
Remarks on MMAD:
MMAD / GSD: Mass Median Diameter 0.5 to 3.35 μm (sulphuric acid)
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
SULPHUR DIOXIDE
- Instruments were calibrated against a published wet chemical method.
- For groups exposed to mixtures of sulphur dioxide and sulphuric acid mist, sulphur dioxide was sampled daily with an impinger at the chamber inlet, prior to mixing with sulphuric acid, and analysed by the wet chemical method to check concentration.
- Prior experimentation verified that the resulting sulphur dioxide concentration was the same at the chamber air inlet and in the chamber.
- For the group exposed to sulphur dioxide alone (group 2), samples of chamber air were taken daily and analysed by the wet chemical method.

SULPHURIC ACID MIST
- Samples of each chamber's atmosphere was collected once daily on a glass-fibre filter and analysed according to the turbidimetric method during the absence of sulphur dioxide and ash in the chambers.
- Particle size measurements were performed with a cascade impactor.
- Mass median diameter was calculated using a published method.
- Determinations were made during the absence of fly ash in the chambers.

FLY ASH
- Chamber samples were obtained daily with a glycerin-filled impinger and the suspensions were analysed for fly ash concentration by standard spectrophotometry.
- Particle size analysis was performed with a multiple stage aero-dynamic particle sizer.
- Mass median diameter was calculated by standard methods.
- Samples were also obtained for examination by light or electron microscopy.
- Determinations were made during exclusion of sulphuric acid mist from the chambers.
Duration of treatment / exposure:
Animals were exposed for 22 to 23 hours per day for 78 weeks
Frequency of treatment:
Daily
Doses / concentrations
Remarks:
Doses / Concentrations:
0.1 to 1 mg/m3
Basis:
analytical conc.
No. of animals per sex per dose:
Nine animals (five males and four females or vice versa)
Control animals:
yes, sham-exposed
Details on study design:
- After the animals were placed in the exposure chamber, a period of two weeks was allowed for adaptation.
- During the following eight weeks, all groups were exposed to filtered air and physiological measurements were made to establish base line values and normal week to week variations.
- Exposure to sulphur dioxide, sulphuric acid mist and fly ash mixtures was then initiated and continued for a period of 18 months.
- The exposure was interrupted twice each day to permit feeding of the animals and cleaning of the chambers.
- Exposures were also interrupted for the duration of the particular test on days when physiological measurements were made.
- When mixtures of sulphur dioxide and sulphuric acid were used, interruption of one agent or other was also made from time to time to permit verification of analytical concentrations.

Examinations

Observations and examinations performed and frequency:
- Body weights were recorded weekly during the 8 week pre-exposure period and during the 78 weeks of exposure.
- Observation for survival and gross signs of behavioural abnormality were made daily.
- Regular pulmonary function tests included measurement of mechanical properties of the lung (weekly during pre-exposure period and the first nine weeks of exposure, and then every four weeks). Diffusing capacity of the lung was also tested (five times during the pre-exposure period, every two weeks for the first ten weeks of exposure, and then every four weeks).
- Lung tests were performed without anaesthesia and after removal of the animals from the exposure chamber. The animals were placed in a sitting position in a restraining chair and allowed to adapt to the face mask attachment for 10 to 20 minutes.
Sacrifice and pathology:
- Animals were killed with an overdose of pentobarbital sodium followed by exsanguination.
- Complete necropsies were performed on each animal.
- The trachae, peribronchial lymph nodes, heart, liver and kidneys were taken and fixed in 10% neutral buffered formaldehyde solution. Six-micron hematoxylin-eosin stained slides were then prepared.
- The lungs were removed from animals in an inflated state and perfused intratracheally with a volume of 10 % neutral buffered formaldehyde solution equal to the tidal volume of the animal. Slides were prepared from each of the seven lobes of the lungs.
Other examinations:
- Arterial blood was obtained from the femoral artery for measurements of oxygen tension, carbon dioxide tension and acidity. Each sample of blood was obtained 10 to 20 minutes after injection of phencyclidine hydrochloride for tranquilisation of the animal.
- Blood obtained from the femoral artery was used to determine hematocrit, haemoglobin, total erythrocyte and leucocyte counts, lymphocytes, segmented neutrophils, blood urea nitrogen, total bilirubin, serum total protein, serum albumin, serum glutamic oxaloacetic transaminase (SGOT), serum glutamicpyruvic transaminase (SGPT), serum lactic acid dehydrogenase (LDH), and serum alkaline phosphatase. Determinations were made once during the pre-exposure period and at weeks 11, 16, 25, 49 and 77 of the exposure period.
Statistics:
- All data were stored and analysed using a digital computer system.
- Regression analysis techniques were used on the measured functions when sufficient data points (> 8) were available.
- Comparisons of the regression coefficients between groups were made by t-test and confidence intervals were calculated.
- In all cases P < 0.05 was chosen for accepting or rejecting differences between groups as significant.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
One death in the control group of set A and one death in Group 3 of set A (neither death was considered to be related to exposure to the pollutants)
Mortality:
mortality observed, treatment-related
Description (incidence):
One death in the control group of set A and one death in Group 3 of set A (neither death was considered to be related to exposure to the pollutants)
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not specified
Food efficiency:
not specified
Water consumption and compound intake (if drinking water study):
not specified
Ophthalmological findings:
not specified
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Description (incidence and severity):
Considerable variation in SGOT, SGPT, LDH and alkaline phosphatase were observed during the exposure period in all groups of monkeys but no trend indicating possible effects from the exposures were observed
Urinalysis findings:
not specified
Behaviour (functional findings):
not specified
Organ weight findings including organ / body weight ratios:
not specified
Gross pathological findings:
effects observed, treatment-related
Description (incidence and severity):
Fly ash was deposited peribronchially, perivascularly and in the alveolar septa in the lungs. Fly ash particles had been phagocytised and, with the exception of occasional focal alveolitis, no significant reaction was associated with particle deposition.
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
Exposure related microscopic alterations observed in the lungs
Histopathological findings: neoplastic:
not specified
Details on results:
- With the exception of results obtained with measurements of pulmonary flow resistance (R1) and distribution of ventilation, no other measured functions changed as the result of exposure, and only variations normally presented by unexposed control animals were observed.
- Increases in pulmonary flow resistance could not be definitely attributed to exposure conditions.
- Results for distribution of ventilation, measured by the nitrogen washout technique, demonstrated a significant increase in the number of breaths to washout 1 % nitrogen, only in group 12 and was not considered to indicate a detrimental effect because the group began the study with significantlylower values than monkeys in group 1 or group 15.
- Incidental microscopic alterations were present in tissues from the control animals of groups 1 and 9 as well as from all exposed groups.
- Exposure related microscopic alterations were observed in the lungs in groups 4, 10 and 16. In group 10, exposed to 0.99 ppm sulphur dioxide and 0.93 mg/m3 of sulphuric acid mist, the microscopic alterations were characterised by changes in the bronchial mucosa. In some areas of the bronchial tree, focal goblet cell hypertrophy and occasionally hyperplasia were seen; whereas, in other areas of the bronchial tree, the mucosa was thinner thn normal and possessed focal areas of squamous metaplasia. In goup 16, exposed to approximately the same concentrations of sulphur dioxide and sulphuric acid mist as group 10, plus 0.41 mg/m3 fly ash, the same alterations were present.
- In group 4, exposed to 0.99 mg/m3 of sulphuric acid mist and 0.55 mg/m3 of fly ash, microscopic alterations were characterised primarily by changes in the mucosa of the bronchi and respiratory bronchioles. Focal areas of erosion were present in these conducting areas as were focal areas of epithelial hypertrophy and hyperplasia. The severity of these alterations was generally slight. The walls of the bronchi were occasionally thickened and in some instances the airways were ectatic.
- The addition of fly ash to the binary combination of sulphur dioxide and sulphuric acid did not increase the severity of the microscopic alterations over that seen in the lungs from monkeys exposed to the binary combination.
- No detrimental effect had been detected in previous work when cynomolgus monkeys underwent long-term exposure to sulphur dioxide from 0.1 to 5 ppm.
- No detrimental effect had been detected in previous work with exposure of cynomolgus monkeys to fly ash from 0.1 to 0.5 mg/m3.
- No detrimental effect had been detected in previous work when mixtures of sulphur dioxide and fly ash were investigated.
- Regardless of particle size, previous work demonstrated that exposure to sulphuric acid at concentrations above 2.5 mg/m3 induced definite pulmonary function impairment (pulmonary ventilation) in cynomolgus monkeys as well as histopathological effects.

Effect levels

Dose descriptor:
LOAEC
Effect level:
1 mg/m³ air
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see 'Remark'

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

JUSTIFICATION FOR USE OF READ-ACROSS DATA

See comparison of overall physico-chemical and toxicity profiles for target and source chemicals in the data matrix (attached).

RESULTS FOLLOWING EXPOSURE OF CYNOMOLGUS MONKEYS TO VARIOUS AGENTS FOR 18 MONTHS

SET A

Group

Initial Body Weight (kg) ± SE

Agents

Concentration* in mg/m3 for sulphuric acid and fly ash; ppm for sulphur dioxide

Particle size MMD (μm) **

Range for geometric deviation of particle size determinations

Deaths occurring during exposure

Conclusion on effects of exposure

1

3.1 ± 0.2

Filtered air

-

-

-

1 accidental

-

2

2.9 ± 0.2

SO2

5.12 ± 0.21

-

-

0

No detrimental effects detected

3

3.0 ± 0.4

H2SO4

0.11 ± 0.09

0.75 ± 0.3

1.5-3.0

1 due to gastric tympany

No detrimental effects detected

Fly ash

0.53 ± 0.29

4.11 ± 3.0

1.8-2.2

4

3.0 ± 0.3

H2SO4

0.99 ± 0.29

0.64 ± 0.3

1.5-3.0

0

Detrimental effects detected

Fly ash

0.55 ± 0.38

5.34 ± 2.8

1.8-2.2

5

3.3 ± 0.2

SO2

0.11 ± 0.01

-

-

0

No detrimental effects detected

H2SO4

0.10 ± 0.04

1.00 ± 0.3

1.4-2.8

6

3.0 ± 0.3

SO2

1.04 ± 0.09

-

-

0

No detrimental effects detected

H2SO4

0.10 ± 0.03

0.53 ± 0.3

1.4-2.8

7

3.3 ± 0.3

SO2

5.15 ± 0.26

-

-

0

No detrimental effects detected

H2SO4

0.11 ± 0.05

1.07 ± 0.1

1.4-2.8

8

3.5 ± 0.3

SO2

5.23 ± 0.45

-

-

0

No detrimental effects detected

H2SO4

0.97 ± 0.28

0.52 ± 0.2

1.4-2.8

* Mean ± SD of between 542 to 952 daily determinations during the 18 months of exposure

** Mean ± SD of between 8 to 82 determinations during the 18 months of exposure

 

SET B

Group

Initial Body Weight (kg) ± SE

Agents

Concentration* in mg/m3 for sulphuric acid and fly ash; ppm for sulphur dioxide

Particle size MMD (μm) **

Range for geometric deviation of particle size determinations

Deaths occurring during exposure

Conclusion on effects of exposure

9

3.1 ± 0.3

Filtered air

-

-

-

0

-

10

3.4 ± 0.3

SO2

0.99 ± 0.22

-

-

0

Detrimental effects detected

H2SO4

0.93 ± 0.26

0.50 ± 0.06

1.5-3.8

0

11

3.2 ± 0.3

SO2

0.11 ± 0.05

-

-

0

No detrimental effects detected

H2SO4

0.11 ± 0.05

3.35 ± 1.26

1.5-5.2

0

12

3.3 ± 0.3

SO2

0.89 ± 0.18

-

-

0

No detrimental effects detected

H2SO4

0.11 ± 0.05

3.11 ± 0.77

4.5-5.2

0

13

3.1 ± 0.2

H2SO4

0.09 ± 0.06

2.58 ± 0.64

1.5-5.2

0

No detrimental effects detected

Fly ash

0.45 ± 0.17

5.89 ± 3.64

1.6-2.6

14

3.2 ± 0.3

SO2

0.12 ± 0.04

-

-

0

No detrimental effects detected

H2SO4

0.10 ± 0.04

2.73 ± 0.54

1.5-5.2

Fly ash

0.46 ± 0.22

4.87 ± 3.12

1.6-2.6

15

3.0 ± 0.2

SO2

0.84 ± 0.17

-

-

0

No detrimental effects detected

H2SO4

0.09 ± 0.04

2.37 ± 0.59

1.5-5.2

Fly ash

0.42 ± 0.18

4.92 ± 1.09

1.6-2.6

16

3.3 ± 0.4

SO2

1.01    1.00

-

-

0

Detrimental effects detected

H2SO4

0.88 ± 0.29

0.54 ± 0.10

1.5-3.8

Fly ash

0.41 ± 0.16

4.10 ± 0.96

1.8-2.8

17

3.5 ± 0.4

SO2

0.11 ± 0.04

-

-

0

No detrimental effects detected

H2SO4

0.10 ± 0.03

0.71 ± 0.19

1.49-3.80

Fly ash

0.44 ± 0.18

5.24 ± 2.34

1.80-2.78

18

3.1 ± 0.3

SO2

0.93 ± 0.22

-

-

0

No detrimental effects detected

H2SO4

0.09 ± 0.03

0.64 ± 0.29

1.49-5.80

Fly ash

0.48 ± 0.22

5.18 ± 3.12

1.80-2.78

19

3.6 ± 0.2

SO2

5.29 ± 0.94

-

-

0

No detrimental effects detected

H2SO4

0.10 ± 0.04

0.54 ± 0.23

1.49-3.80

Fly ash

0.44 ± 0.16

4.87 ± 1.90

1.80-2.78

* Mean ± SD of between 542 to 952 daily determinations during the 18 months of exposure

** Mean ± SD of between 8 to 82 determinations during the 18 months of exposure

 

Applicant's summary and conclusion

Conclusions:
The authors conclude that deleterious effects detected from exposure to mixtures of sulphur dioxide, fly ash and sulphuric acid mist were attributable to the presence of the acid mist alone.

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