Potassium carbonate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

short-term repeated dose toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Data source

Reference

Reference Type:

publication

Title:

A subacute inhalation exposure evaluation of a scrubbing solution used in petroleum refineries

Author:

Bui QQ et al.

Year:

1998

Bibliographic source:

J. Toxicol. Environ. Health, Part A, 54:49-62, 1998

Materials and methods

Test guideline

Test guideline 1

Qualifier:

equivalent or similar to guideline

Guideline:

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

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

other: OECD Guideline 424 (Neurotoxicity Study in Rodents)

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Potassium carbonate

EC Number:

209-529-3

EC Name:

Potassium carbonate

Cas Number:

584-08-7

Molecular formula:

CH2O3.2K

IUPAC Name:

dipotassium carbonate

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Portage, MI, USA (Sprague-Dawley Crl:CD VAF/plus)
- Age at study initiation: approximately 43 days
- Weight at arrival at study laboratory:  Males: 130 g, Females: 110 g
- Fasting period before study:
- Housing: All animals were individually housed in stainless-steel, wire-mesh cages suspended above cage papers
- Diet: Purina certified rodent chow 5002, ad libitum during nonexposure periods
- Water: tap water, ad libitum during nonexposure periods
- Acclimation period: 10 to 13 days

ENVIRONMENTAL CONDITIONS
- Temperature: 23 +/- 2 °C
- Humidity: 40 - 70 %
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 13 h light/11 h dark cycle

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: The aerosol concentration was reduced to the target concentrations by dilution with the chamber ventilation air flow.

Remarks on MMAD:

MMAD / GSD: Respirable aerosol was generated, similar in all exposure groups (mean MMAD of all samples ranged from 2.16 to 2.54 µm)
Aerosol particle size was determined twice during each exposure week for each test article exposure chamber using an INTOX Products, Inc. (Albuquerque, NM), model 02-140/JB seven-stage cascade impactor with cutoff diameters ranging from 0.26 to 5.27 µm.

Details on inhalation exposure:

All animals were caged individually and exposed, 6 h/d for 21 consecutive days, in stainless-steel and glass whole-body inhalation chambers operated under dynamic conditions of at least 12 air changes per hour. Respirable-range aerosols were generated with stainless-steel atomizers (Spraying Systems, Inc., Wheaton, lL) fitted with a no. 1650 fluid nozzle and a no. 64 air eap. The atomizer sprayed into a 6-L glass chamber to collect large droplets produced during the atomization process. The resulting aerosol was piped to the exposure chamber inlets, where the aerosol concentration was reduced to the target concentrations of 0.1, 0.2, or 0.4 mg/L by dilution with the chamber ventilation air flow.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Target concentrations (mg/L): control (filtered air), 0.1, 0.2, 0.4; Mean actual concentrations (mg/L): control, 0.11, 0.16, 0.41
The actual exposure concentrations were determined by standard gravimetric methods after collecting samples on 25-mm Teflon filters (Millipore type FG, 0.2 µm).
Test atmosphere homogeneity was determined prior to Initiation of animal exposure for each target exposure level. Analytical confirmation of exposure concentrations was performed by ion-exchange chromatography using electrochemical conductivity detection for potassium.

Duration of treatment / exposure:

21 days

Frequency of treatment:

daily, 6 hours per day

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0.1, 0.2 and 0.4 mg used scrubbing solution/L
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
0.11, 0.16 and 0.41 mg used scrubbing solution/L
Basis:
analytical conc.

No. of animals per sex per dose:

15 rats per sex per dose level were assigned to the systemic toxicity study part and 15 rats per sex per dose level were assigned to the neurotoxicity study part

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: In a 2-week dose range finding study systemic toxicity (weight loss and respiratory symptoms) were noted at 0.5 mg/L.

- Rationale for selecting satellite groups: not given.

- Post-exposure recovery period in satellite groups: 14 days, 5 rats per sex per dose level in each study part

Positive control:

no data

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Mortality, abnormal behavior and appearance was observed twice daily throughout the study.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule:
Clinical observations during the exposure period: daily, prior to placement into the inhalation chambers, during the 6-h daily exposure period, and approximately 1 h following the completion of the daily exposure.

BODY WEIGHT: Yes
- Time schedule for examinations: twice weekly, beginning 1 week prior to treatment

FOOD CONSUMPTION: Yes
- Food consumption for each animal determined: twice weekly, beginning 1 week prior to treatment
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data
FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No data

WATER CONSUMPTION: No data

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations: prior to the first exposure, during the treatment period (day 18), and after completion of exposure, all ocular examinations were conducted using a biomicroscope and indirect ophthalmoscope, preceded by mydriasis (1% atropine sulfate solution).
- Dose groups that were examined: all animals

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the primary (day 21) and satellite necropsies (day 35)
- Anaesthetic used for blood collection: No data
- Animals fasted: Yes overnight
- How many animals: all surviving animals per group and sex
- Parameters checked:
erythrocyte, leukocyte, differential leukocyte, and platelet counts, hemoglobin concentration, hematocrit, mean corpuscular hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin concentration, prothrombin time, and activated partial thromboplastin time

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the primary (day 21) and satellite necropsies (day 35)
- Animals fasted: Yes overnight
- How many animals: all surviving animals per group and sex
- Parameters checked:
creatine kinase, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, lactate dehydrogenase, and alkaline phosphatase activities, concentrations of blood urea nitrogen, total serum protein, albumin, globulin, creatinine, cholesterol, glucose, calcium, phosphorus, sodium, potassium, chloride, and total bilirubin

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: Yes
- A functional observational battery (FOB) was conducted on 10 rats per sex per group at prestudy, 1 h following the completion of the first exposure (day 0), approximately 18 h after the first exposure (Day 1), following completion of the last exposure (day 21), and on 5 rats per sex per group at the end of the recovery period (day 35). Tests included, while in the home cage, each animal was observed and scored for posture, convulsions/tremors, biting, circling, writhing, palpebral closure, and vocalization; upon removal from the cage: ease of removal, ease of handling, lacrimation, chromodacryorrhea, piloerection, palpebral closure, fur appearance, and salivation; open-field observations over a 2-min period: time to first steps, degree of locomotion, arousal, convulsions/tremors, grooming, gait abnormalities, responses to approach, startle, touch, and tail pinch, olfactory orientation, air righting reflex, forelimb and hindlimb extension, and eye-blink response; grip strength, hind-limb extensor strength, hind-limb food splay, rotarod performance, body temperature, and catalepsy were also monitored and recorded.

- Locomotor activity was recorded after completion of each FOB session using a Digiscan "Micro" animal activity system; sessions were 40 min in length, and each session was divided into for 10-min intervals.

- Neurohistopathologic examinations: Brain weight and dimension were recorded and neurohistopathologic examinations were conducted on various sections of the brain (forbrain, center of cerebrum, midbrain, cerebellum and pons, and medulla), spinal cord (cross and longitudinal sections of the cervical and lumbar cord), eyes, and nerves (optic, sciatic, neural, tibia, and peroneal).

Sacrifice and pathology:

A complete necropsy was conducted on all animals that were found dead or euthanized at the scheduled primary (day 21) and satellite sacrifice (day 35, after 21 exposure and 14 recovery days).

GROSS PATHOLOGY: Yes
The necropsy included an examination of external surface, all orifices, and the cranial, thoracic, abdominal, and pelvic cavities, including the viscera. The adrenals, brain, heart, kidneys, liver, lungs (prior to inflation with fixative), ovaries, spleen, testes, and thymus were removed and weighed. Aorta, bone marrow (sternal and femoral), exorbital lacrimal glands, eyes, femur, gastrointestinal tract, mesenteric lymph nodes, mammary glands, nasal cavities, optic nerve, pancreas, sciatic nerve, pituitary, prostate, salivary glands, seminal vesicles, thyroid, trachea, urinary bladder, uterus, vagina, and all gross lesions were also removed.
All Tissues including the entire head (after removal of other appropriate specified tissue) were placed in 10% neutral buffered formalin. Following fixation, the sculls were decalcified until soft. All tissues were stained with hematoxilin and eosin.

HISTOPATHOLOGY: Yes
Microscopic evaluation was conducted on all tissues for the control and highest exposure level groups. Microscopic examination of the nasal cavities, lungs, liver, kidneys, and gross lesions was performed for the low and mid exposure level groups. Levels I and II of the nasal cavities and the lungs were examined microscopically from all animals at the satellite necropsy.

Statistics:

Body weights, body weight changes, food consumption, clinical pathology parameters, and organ weights were analyzed by a one-way analysis of variance (ANOVA). Pair wise comparisons between test and control groups were made with Dunnett´s test. Continuous FOB and motor activity data were analyzed using a two-way repeated measure ANOVA. If significant treatment or treatment-time interactions occurred, a one-way ANOVA was conducted at each time point. When corresponding F-test for difference was significant, Dunnett´s multiple test was conducted to determine significant differences from the control group (p < .05). Non-continuous data were analyzed with Fischer´s exact test using the .05 significance level.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

- Clinical observations during the exposure period: no treatment-related abnormalities
- Abnormal behavior and appearance: no treatment-related abnormalities

Mortality:

mortality observed, treatment-related

Description (incidence):

One female in the 0.4 mg/l exposure level died on day 14 of exposure. Gasping was noted prior to death, but the specific cause of death could not be identified at necropsy.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

-- 0.1 and 0.2 mg/l dose groups: no treatment-related abnormalities
-- 0.4 mg/l dose group: in females no treatment-related abnormalities; in males, a statistically significant reduction in weight gain of 6 g was noted during study days 10 to 14 in conjunction with a statistically significant reduction in food intake of 2 g. During the recovery period the mean body weight gain of the high-exposure males was comparable to control values.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

-- 0.4 mg/l dose group: in females no treatment-related abnormalities; in males, a statistically significant reduction in weight gain of 6 g was noted during study days 10 to 14 in conjunction with a statistically significant reduction in food intake of 2 g

Food efficiency:

not examined

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Description (incidence and severity):

no treatment-related effects
In the 0.2 mg/L group females, the mean albumin-globulin ratio was statistically higher than control values at d 21; this was not observed at higher exposure levels and thus was not attributed to exposure.

Urinalysis findings:

not examined

Behaviour (functional findings):

no effects observed

Description (incidence and severity):

- Functional observational battery (FOB): No apparent test-material-related differences; no treatment-related effects were noted in the home cage observations, open-field, sensory, neuromuscular, and physiological observations and locomotor activities at any exposure level. The rotarod performance activities in the 0.2 mg/L males were decreased. However, rotarod performance activities were not changed in the 0.2 mg/L females or 0.4 mg/L groups.
- Brain weight and size: no treatment-related effects.
- Neurohistopathologic examinations: no treatment-related findings;
No unusual microscopic lesions were observed in any of the central or peripheral nervous system tissues examined. Digestion chambers were noted in the peroneal nerve of one control female and one 0.4 mg/l male, and in the sciatic nerve of one control male.

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

- Mean absolute and relative lung weights at end of exposure period: significantly dose-related increased (9-35%) in both male and females in all treated groups
- Mean absolute and relative lung weights at end of recovery period: comparable to control values except for a significant increase in the 0.4 mg/l group females
- Further measured organ weights: no treatment-related effects.
In the female 0.2 mg/L satellite recovery group, a significant increase in absolute thymus gland weight was noted. However, this change was not attributed to treatment since a dose-response relationship was not observed at higher exposure levels.

Gross pathological findings:

not specified

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

-- Respiratory tract at end of exposure period: Effects attributed to the irritant property of the test material were seen in all dose levels.
--- Nasal cavity: In level I of the nasal cavities, minimal to moderate epithelial hyperplasia and minimal to moderate epithelial necrosis were found in all treated groups.
In level II of the nasal cavities, mild cytoplasmic vacuolization of the olfactory epithelium lining dorsal meatus was noted in the 0.2 and 0.4 mg/L groups. Minimal epithelial necrosis in level II of nasal cavities was found in two 0.4 mg/l group females.

--- Lungs: Bronchiolization was observed in the treated groups, and alveolar macrophage infiltration was found in both control and treated groups. These changes were mostly multifocal and accompanied by minimal to moderate nonsuppurative interstitial inflammation in a single 0.2 mg/L male, and 7 males and 4 females in the 0.4 mg/L group

-- Respiratory tract at end of recovery period
--- Nasal cavity: There were no test-material-related findings observed in either level I or II of the nasal cavities, thus demonstrating reversibility of effects seen in the nasal cavity at the end of exposure period.
--- Lungs: Mild bronchiolization and alveolar macrophage infiltration were found in the high-exposure group. A general trend toward reversibility of the changes in the lungs was discerned due to the decreased incidence of alveolar macrophage infiltration, nonsuppurative interstitial inflammation, and severity of the effects seen in this dose-group. The absence of bronchiolization in the low- and mid-dose groups was also considered as evidence of reversibility.

-- Reproductive organs: no treatment-related findings (ovaries, mammary glands, uterus, vagina, testes, prostate, and seminal vesicles examined)
-- Further examined organs and tissues: no treatment-related findings

Histopathological findings: neoplastic:

no effects observed

Effect levels

1

Dose descriptor:

NOEC

Remarks:

systemic

Effect level:

0.4 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: highest concentration tested, no effects, based on product

2

Dose descriptor:

NOEC

Remarks:

systemic

Effect level:

0.123 mg/L air

Sex:

male/female

Basis for effect level:

other: recalculated, based on potassium carbonate content of test item

3

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

0.2 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: see 'Remark'

4

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

0.062 mg/L air

Sex:

male/female

Basis for effect level:

other: recalculated, based on potassium carbonate content of test item

5

Dose descriptor:

LOEC

Remarks:

local

Effect level:

0.1 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: see 'Remark'

6

Dose descriptor:

LOEC

Remarks:

local

Effect level:

0.031 mg/L air

Sex:

male/female

Basis for effect level:

other: recalculated, based on potassium carbonate content of test item

7

Dose descriptor:

NOEC

Remarks:

neurotoxicity

Effect level:

0.4 mg/L air (analytical)

Sex:

male/female

Basis for effect level:

other: highest concentration tested; no effects (FOB, locomotor activities, brain weight and size, neurohistopathology), based on product

8

Dose descriptor:

NOEC

Remarks:

neurotoxicity

Effect level:

0.123 mg/L air

Sex:

male/female

Basis for effect level:

other: recalculated, based on potassium carbonate content of test item

Target system / organ toxicity

Critical effects observed:

no

Applicant's summary and conclusion

Conclusions:

Whole body exposure to up to and including 0.4 mg/l of a used scrubbing solution aerosol (pH 9.9, with main active ingredient 30.8% potassium carbonate) 6 h/d for 21 consecutive days did not result in any relevant systemic toxicity or neurotoxicity in either male or female rats. Reversible histopathological changes were noted in levels I and II of the nasal cavities and in the lungs of the treated animals, and were indicative of a local response to the irritant property of the test solution.The respiratory-tract findings were considered a local response to the high alkalinity of the test material as substantiated by the return to normal upon cessation of exposure.

Executive summary:

In a sub-acute inhalation toxicity study similar to OECD guideline 412 (Repeated Dose Inhalation Toxicity: 28/14-Day) and OECD Guideline 424 (Neurotoxicity Study in Rodents) an aerosol of a used potassium carbonate-based scrubbing solution “Catacarb” (pH 9.9, with main active ingredient 30.8% potassium carbonate; further ingredients: 65.1% water, 1.6% diethanolamine, 0.4% potassium borate (as boron), 0.3% potassium metavanadate (as vanadium), and 6.7 ppm chromium, 8.4 ppm molybdenum and 4.5 ppm nickel) was administered to groups of 30 Sprague Dawley rats per sex and concentration The scrubbing solution was administered by whole body exposure at concentrations of 0, 0.1, 0.2 and 0.4 mg/L for 6 hours per day, 7 days/week for a total of 21 consecutive days. A functional observational battery (FOB) and locomotor activity tests were conducted on 10 rats per sex per group at prestudy, 1 h following the completion of the first exposure (d 0), approximately 18 h after the first exposure (d 1), following completion of the last exposure (d 21), and on 5 rats per sex per group at the end of the recovery period (d 35).At the end of the exposure period, 10 rats per sex per dose level were anesthetized with methoxyfluorane, exsanguinated, and necropsied for systemic toxicity evaluation and 10 rats per sex per dose level were euthanized by carbon dioxide and then perfused in situ for neurotoxic evaluation. The remaining 10 rats per sex per dose level were allowed a 14-d recovery period, and sacrificed on study day 35, 5 rats each were evaluated for systemic toxicity or neurotoxicity.

One female in the 0.4 mg/l exposure level died on day 14 of exposure. Gasping was noted prior to death, but the specific cause of death could not be identified at necropsy. Food consumption and weight gain were not affected in the 0.1 and 0.2 mg/L group males and females and 0.4 mg/L group females. In the 0.4 mg/L males, a statistically significant reduction in weight gain of 6 g was noted during study days 10-14 in conjunction with a statistically significant reduction in food intake of 2 g. During the recovery period the mean body weight gain of the high-exposure males was comparable to control values. No apparent adverse effects were noted at any exposure level as determined by clinical observations, hematology, serum chemistry, ophthalmologic observations, and gross pathology. Statistically significant increases in lung weights were noted at all treatment levels but returned to control values upon cessation of exposure except for the 0.4 mg/L female group. There were no significant changes in other organ weights. Histopathological findings were restricted to the respiratory tract and characterized by minimal to moderate epithelial hyperplasia, epithelial necrosis, and cytoplasmic vacuolation at levels I and II of the nasal cavities. Lung bronchiolization and alveolar macrophage infiltration were also observed. The histopathological respiratory tract findings were fully reversible in all dose groups, except for the 0.4 mg/l exposure group, in which bronchiolization and alveolar macrophage infiltration were tendentially but not fully reversible. The respiratory-tract findings were considered a local response to the high alkalinity of the test material (pH approximately 9.9) as substantiated by the return to normal upon cessation of exposure. No treatment-related findings were seen in further examined organs and tissues including the reproductive organs (ovaries, mammary glands, uterus, vagina, testes, prostate, and seminal vesicles examined). Exposure to scrubbing solution had no adverse effect on FOB endpoints and locomotor activity evaluations, brain weight and size, and neurohistopathologic examinations.

The study authors came to the conclusion, that whole body exposure to up to and including 0.4 mg/l of a used scrubbing solution aerosol (pH 9.9, with main active ingredient 30.8% potassium carbonate) 6 h/d for 21 consecutive days did not result in any persistent systemic toxicity or neurotoxicity in either male or female rats. Reversible histopathological changes were noted in levels I and II of the nasal cavities and in the lungs of the treated animals, and were indicative of a local response to the irritant property of the test solution.The respiratory-tract findings were considered a local response to the distinct alkalinity of the test material as substantiated by the return to normal upon cessation of exposure.

NOEC systemic based on product 0.4.mg/l air

NOAEC based on potassium carbonate content of test item: 0.123 mg/l air

 

NOAEC local based on product: 0.2 mg/l air

NOAEC based on potassium carbonate content of test item: 0.062 mg/l air

NOAEC local derivation based on temporary histopathological respiratory tract findings and increased lung weights considered as a local response to the high alkalinity of the test material in all dose groups (0.1, 0.2 and 0.4 mg scrubbing solution/l), fully reversible within 14 days up to and including the dose level of 0.2 mg/l, tendentially reversible at dose level 0.4 mg/l (LOEC is 0.1 mg/l (lowest tested concentration))

Toxicodynamic cause of the irritating effect: solely alkalinity