Potassium nitrate

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June-October 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 403 (Acute Inhalation Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

acute toxic class method

Limit test:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Potassium nitrate

EC Number:

231-818-8

EC Name:

Potassium nitrate

Cas Number:

7757-79-1

Molecular formula:

HNO3.K

IUPAC Name:

potassium nitrate

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in study report): potassium nitrate, NPC
- Physical state: Solid, crystalline

Test animals

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Animal Breeding Facility, Jai Research Foundation.
- Age at study initiation: 8-9 weeks.
- Weight at study initiation: males between 244-279 g and females between 175-197 g.
- Housing: 5 rats/cage according to group and sex in solid polipropylene rat cages (stainless steel grip on top)
- Diet (e.g. ad libitum): rat pellet, ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: Minimum period of 5 days prior to exposure


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-24
- Humidity (%): 65-68
- Air changes (per hr): Minimum 15 per hour.
- Photoperiod (hrs dark / hrs light): 12 hours light/12 hours dark.

Administration / exposure

Route of administration:

inhalation: dust

Type of inhalation exposure:

nose/head only

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Inhalation chamber, model head/nose only
- Exposure chamber volume: 63.5 L
- Method of holding animals in test chamber: portholes with transparent perspex rat exposure tubes.
- Source and rate of air: compressed air, 40 liters perminute (inflow)
- Method of conditioning air: air filters and moisture separator.
- System of generating particulates/aerosols: Fluidized bed dust generator system (In-Tox Products, USA)
- Method of particle size determination: Seven stage cascade impactor (Model No 02-150).
- Treatment of exhaust air: 1% sodium hydroxide solution and moisture traps containing silica gel.
- Temperature, humidity, pressure in air chamber: temperature 21.2-23.7 °C, relative humidity 42.1-58.9%, pressure 40 psi

TEST ATMOSPHERE
- Brief description of analytical method used: A open sampler with glass microfibre papers (Whatman International Ltd, Maidstone, England) was used to assess the breathing zone concentration. A suitable measured volume of air (1.77 L per minute) was extracted from the inhalation chamber. At the end of air sampling (1 minute), the glass microfibre papers with the test substance were weighed to determine the concentration of potassium nitrate at the breathing zone of the rats.
- Samples taken from breathing zone: yes, every one hour of exposure.


VEHICLE
- Composition of vehicle: No vehicle

TEST ATMOSPHERE
- MMAD (Mass median aerodynamic diameter) / GSD (Geometric st. dev.): MMAD 50% 3.13 u, GSD 2.75

Analytical verification of test atmosphere concentrations:

yes

Remarks:

gravimetric concentration analysis

Duration of exposure:

4 h

Concentrations:

the maximum achievable concentration (4 hour mean measured value by gravimetric analysis) of potassium nitrate in the air at breathing zone of rats was 0.527 mg/L air.

No. of animals per sex per dose:

5 females and 5 males per group

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: Toxic signs and mortality were observed at hourly intervals during the 4 h exposure period and at 1 hour post exposure on the day of exposure. Subsequently, rats were observed daily, twice a day for moribund state and mortality. The detailed clinical signs were recorded once a day.
- Necropsy of survivors performed: yes. Gross pathological examination.
- Other examinations performed: clinical signs, body weight,organ weights, histopathology, other: Observations included, but not limited to, evaluation of skin and fur, eyes and mucous membranes, respiratory and circulatory effects, autonomic and central nervous system effects, somatomotor activity and behaviours patter and observation of tremor, convulsions, salivation, diarrhea, lethargy, sleep and coma. Body weight was recorded individually, immediately prior to exposure, on day 7 and 14.

Statistics:

As the study conducted was a limit test at the maximum achievable breathing zone concentration, no statistical analysis was required to calculate the LC50.

Results and discussion

Preliminary study:

At maximum achievable breathing zone concentration no mortality and lesion of pathological significance were observed in the treatment group as well as in the control group rats.

Effect levels

Key result

Sex:

male/female

Dose descriptor:

LC50

Effect level:

> 0.527 mg/L air

Exp. duration:

4 h

Remarks on result:

other: maximum achievable concentration

Mortality:

No mortality was observed in the control group as well as the treatment group rats.

Clinical signs:

other: No toxic signs were observed in the control group rats as well as in rats treated with 0.527 mg potassium nitrate/L air.

Body weight:

The per cent body weight change of rats from the treatment group were comparable to that of the control group at the end of the experiment.

Gross pathology:

External examination of the terminally sacrificed rats belonginf to both the control and treatment groups did not reveal any lesion of pathological significance.
Visceral examination of control and treatment group rats sacrificed during termination did not reveal any lesion of pathological significance except uuterine distension (rat no 19). Above noticed lesion is physiological/cyclical in nature and coould be considered as spontaneous finding, unrelated with the treatment.

Other findings:

No other findings

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Remarks:

Not classified according to Regulation (EC) 1272/2008

Conclusions:

No mortality, no lesion of pathological significance were observed at the maximum achievable breathing zone concentration (0.527 mg/L air). The acute median lethal concentration (LC50) of potassium nitrate was found to be greater than 0.527 mg/L air.

Executive summary:

The study was performed to assess the acute inhalation toxicity (LC50) of potassium nitrate in Wistar rats. The method follow was as per the guidelines of OECD 403 (May 1981).

The study was conducted using inhalation equipment (head/nose only). Two groups of rats comprising of five males and five females each, were used for the study. The rats from Group I were exposed to air passed through inert bed material (iron grid) and served as control group. The rats from Group II were exposed to the maximum achievable breathing zone concentration (0.527 mg/L air) of potassium nitrate. Rats from either group were exposed for 4 hours followed by observation for a period of 14 days. No toxic signs and no mortality were observed in the rats of the control as well as rats treated with potassium nitrate. No effect on body weight was observed during the experiment in the rats from either the control or treated group.

The acute median lethal concentration (LC50) of potassium nitrate was found to be greater than 0.527 mg/L air.