Potassium nitrite

Endpoint summary

Description of key information

Repeated dose toxicity: Oral

A subchronic oral toxicity study with test chemical was carried out in groups of ten male and ten female 6-wk-old rats. No mortality observed and the rats appeared to be healthy throughout the study. Effects were observed in food and water consumption, opthalological and haematological effects were observed. It was concluded that in the study reported here the NOEL is lower than I00 mg /litre in the drinking-water, which is equivalent to a level lower than 10 mg /kg body weight/day and a NOAEL of 300 mg/L drnking water was observed.

Repeated dose toxicity: Inhalation

According to column 2 of Annex VIII, exposure by inhalation route is negligible on account of high boiling points (as has been informed in the boiling point that is greater than 300 °C).

 

Repeated dose toxicity: Dermal

The acute dermal toxicity value for test chemical is >2000 mg/kg body weight. Considering this, the end point for repeated dermal toxicity is considered as waiver.

Key value for chemical safety assessment

Toxic effect type:

dose-dependent

Repeated dose toxicity: via oral route - systemic effects

Link to relevant study records

Reference

Reference 1

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:

data from handbook or collection of data

Justification for type of information:

Data is from publication

Qualifier:

according to guideline

Guideline:

other: As mentioned below

Principles of method if other than guideline:

To determine Subchronic oral toxicity study of test chemical on Rats.

GLP compliance:

no

Limit test:

no

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Weanling, Wistar derived SPF-bred rats (Bor; WlSW)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Winkelmann (Institute for the Breeding of Laboratory Animals GmbH & Co. KG, Borchen, FRG).
- Females (if applicable) nulliparous and non-pregnant:yes
- Age at study initiation: 6 weeks old
- Weight at study initiation: NA
- Fasting period before study: NA
- Housing: The rats were housed under conventional conditions, in suspended stainless-steel cages fitted with a wire-mesh floor and front.
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 13 days

DETAILS OF FOOD AND WATER QUALITY: All rats were fed the Institute's grain-based open-formula diet (with a nitrite and nitrate content of 2 and 140mg/kg, respectively)

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 + 2°C
- Humidity (%): 40-70%
- Air changes (per hr): 10/hr
- Photoperiod (hrs dark / hrs light): 12hr light/dark cycles

IN-LIFE DATES: From: To:

Route of administration:

oral: drinking water

Details on route of administration:

The rats received potassium nitrite in the drinking-water (tap-water; nitrite and nitrate content <0.01 and 10mg/litre, respectively) at levels of 0 (negative control), 100, 300, 1000 and 3000mg/litre.

Vehicle:

water

Details on oral exposure:

PREPARATION OF DOSING SOLUTIONS:

DIET PREPARATION
- Rate of preparation of diet (frequency): Test solutions and tap-water were freshly supplied to the rats in glass bottles every day.
- Mixing appropriate amounts with (Type of food): Drinking water
- Storage temperature of food: NA

VEHICLE
- Justification for use and choice of vehicle (if other than water):
- Concentration in vehicle: nitrite and nitrate content <0.01 and 10mg/litre
- Amount of vehicle (if gavage): NA
- Lot/batch no. (if required): NA
- Purity:NA

Additional information: The potassium concentrations in the nitrite solutions were equalized by adding KCl up to the K+ level of the 3000 mg KNO2/litre solution.
An additional group received drinking-water supplemented with KCl only, to achieve the same K+ concentration as that found in the 3000 mg KNO2/litre solution.

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

13 weeks (91 days)

Frequency of treatment:

Everyday

Dose / conc.:

0 mg/L drinking water

Remarks:

Negative control

Dose / conc.:

100 mg/L drinking water

Dose / conc.:

300 mg/L drinking water

Dose / conc.:

1 000 mg/L drinking water

Dose / conc.:

3 000 mg/L drinking water

No. of animals per sex per dose:

ten rats of each sex/group (Five treatment groups )

Control animals:

yes, concurrent vehicle

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes / No / Not specified
- Time schedule:

BODY WEIGHT: Yes / No / Not specified
- Time schedule for examinations: The rats were weighed at weekly intervals and were observed daily for condition and behaviour

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes / No / Not specified
- Compound intake calculated as time-weighted averages from the consumption and body weight gain data: Yes / No / Not specified

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: Yes / No / Not specified

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes / No / Not specified
- Time schedule for examinations: Food and liquid intake were measured over weekly periods throughout the study

OPHTHALMOSCOPIC EXAMINATION: Yes / No / Not specified
- Time schedule for examinations: Ophthalmoscopic observations were made in all rats of the control and top-dose groups prior to the administration of the test substances and during wk 13.
- Dose groups that were examined:

URINALYSIS: Yes / No / Not specified
- Time schedule for collection of urine: In wk 9 of treatment urine was collected over a 24-hr period from all rats, except those receiving unsupplemented tap-water
- Metabolism cages used for collection of urine: Yes It was collected in calibrated tubes under cooling on dry ice. Its volume was determined and it was examined for
creatinine and nitrite and nitrate

Sacrifice and pathology:

Early in wk 14, the rats were killed by exsanguination from the abdominal aorta whilst under light ether anaesthesia, and a thorough autopsy was performed.

Statistics:

Data on body weight were evaluated by a oneway analysis of covariance, followed by Dunnett's multiple comparison tests

Clinical signs:

not specified

Mortality:

no mortality observed

Description (incidence):

There were no deaths and the rats appeared to be healthy throughout the study

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Body weight was decreased at 3000 mg/l in males.

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

Growth and food intake were significantly decreased in the 3000-mg/litre group in males.

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

Food efficiency was decreased in the 3000-mg/litre group in males. (data not shown).

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

effects observed, treatment-related

Description (incidence and severity):

Liquid intake was clearly diminished in the 3000- and the 1000-mg/litre groups of males and in the 3000-mg/litre group of females

Ophthalmological findings:

no effects observed

Description (incidence and severity):

Ophthalmoscopic examination did not reveal any differences between the test rats and controls that could be ascribed to treatment

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Haemoglobin concentration, packed-cell volume and erythrocyte count were slightly decreased in the males receiving 1000 and 3000mg/litre, and in the females receiving 1000 mg/litre. In females, the erythrocyte count was also decreased with a dose of 3000 mg/litre which was accompanied by increases in mean corpuscular volume and mean corpuscular haemoglobin. Methaemoglobin concentration was significantly increased with 3000mg/litre in both sexes

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

With the 3000-mg/litre treatment the plasma urea level was increased in males, while the plasma alkaline phosphatase activity was slightly decreased in both sexes, although the difference was statistically significant in females only (Table 3). There was a decrease in plasma aspartate aminotransferase in the females given 1000 and 3000 mg/litre in comparison to the KCI group, but not as compared with the controls receiving unsupplemented drinking-water

Urinalysis findings:

effects observed, treatment-related

Description (incidence and severity):

The volume of the urine produced during 24 hr decreased with increasing nitrite levels in the drinking-water, the differences from the controls being statistically significant in males treated with 3000 mg/litre and in females treated with 300 mg/litre and above . The urine concentration test revealed an increase in the density of the urine of the animals treated with 3000mg/litre in both sexes, accompanied by a decrease in urine production in males . Excretion levels of creatinine and
nitrate did not show treatment-related differences among the groups and nitrite was not found in the urine of any of the groups. There was no evidence of
increased mutagenic activity in the urine of rats receiving 3000 mg/litre, either in the presence or in the absence of S-9 mix and fl-glucuronidase.

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

The absolute and relative weights of the kidneys and spleen in females and the relative weight of the kidneys in males were increased in the group receiving 3000 mg/litre. The increase in the relative brain weight in males receiving 3000 mg/iitre is ascribed to the lower body weight in this group and the well-known inverse correlation between body weight and relative brain weight

Gross pathological findings:

not specified

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

no effects observed

Description (incidence and severity):

Histopathological examination of all other organs was essentially negative.

Histopathological findings: neoplastic:

not specified

Other effects:

not specified

Key result

Dose descriptor:

NOEL

Effect level:

< 100 mg/L drinking water

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

clinical biochemistry

food consumption and compound intake

food efficiency

haematology

ophthalmological examination

organ weights and organ / body weight ratios

urinalysis

water consumption and compound intake

Dose descriptor:

NOAEL

Effect level:

300 mg/L drinking water

Based on:

test mat.

Sex:

female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

mortality

Dose descriptor:

LOAEL

Effect level:

1 000 mg/L drinking water

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

food consumption and compound intake

mortality

Critical effects observed:

no

Conclusions:

A subchronic oral toxicity study with test chemical was carried out in groups of ten male and ten female 6-wk-old rats. No mortality observed and the rats appeared to be healthy throughout the study. Effects were observed in food and water consumption, opthalological and haematological effects were observed. It was concluded that in the study reported here the NOEL is lower than I00 mg /litre in the drinking-water, which is equivalent to a level lower than 10 mg /kg body weight/day and a NOAEL of 300 mg/L drnking water was observed.

Executive summary:

A subchronic oral toxicity study with test chemical was carried out in Wistar derieved SPF Bred rats. Groups of ten male and ten female 6-wk-old rats received test chemical in the drinking-water (tap-water) at levels of 0, 100, 300, 1000 and 3000mg/litre for a period of 13 week. The potassium concentration in the nitrite solutions was equalized by adding potassium chloride (KCL) up to the potassium level of the 3000 mg /litre solution. An additional group of ten males and ten females received drinking-water supplemented with KCI only, at an amount resulting in a potassium concentration equivalent to that of the 3000 mg /litre solution. No mortality observed and the rats appeared to be healthy throughout the study. Ophthalmoscopic examination did not reveal any differences between the test rats and controls that could be ascribed to treatment. Body weight, food intake and food efficiency were decreased at 3000-mg/litre level in males, while liquid intake was decreased in males given 1000 and 3000 mg/litre and in females given 3000 mg/litre. There was a significant increase in the methaemoglobin concentration in animals given 3000 mg/litre, while slight decreases in red blood cell variables occurred at the 1000 and 3000 mg/litre dose. No impaired renal function was observed in any of the test groups, although the relative weight of the kidneys and the plasma urea nitrogen level was increased at 3000 mg/litre. There was a slight decrease in plasma alkaline phosphatase activity at 3000 mg/litre. A small amount of nitrite was present in the saliva of the rats receiving 3000 mg/litre but there was no evidence of increased mutagenic activity in the urine of these rats. Interestingly, hypertrophy of the adrenal zone glomerulosa was observed in all test groups, the incidence and degree being dose related. It was concluded that in the study reported here the NOEL is lower than I00 mg /litre in the drinking-water, which is equivalent to a level lower than 10 mg /kg body weight/day and a NOAEL of 300 mg/L drnking water was observed.

Reference 2

Endpoint:

short-term repeated dose toxicity: oral

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

a short-term toxicity study does not need to be conducted because a reliable sub-chronic (90 days) or chronic toxicity study is available, conducted with an appropriate species, dosage, solvent and route of administration

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEL

300 mg/kg bw/day

Study duration:

subchronic

Species:

rat

Quality of whole database:

K2

System:

urinary

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: inhalation

Data waiving:

exposure considerations

Justification for data waiving:

a short-term toxicity study does not need to be conducted because exposure of humans via inhalation in production and/or use is not likely as based on the provided thorough and rigorous exposure assessment

Endpoint conclusion

Quality of whole database:

Waiver

Repeated dose toxicity: dermal - local effects

Link to relevant study records

Reference

Endpoint:

short-term repeated dose toxicity: dermal

Data waiving:

exposure considerations

Justification for data waiving:

a short-term toxicity study does not need to be conducted because exposure of humans via the dermal route in production and/or use is not likely as based on the provided thorough and rigorous exposure assessment

Endpoint conclusion

Quality of whole database:

Waiver

Additional information

Data available for the target chemical was reviewed to determine the toxic nature of the test chemical upon repeated exposure. The studies are as mentioned below:

 

Repeated dose toxicity: Oral

A subchronic oral toxicity study with test chemical was carried out in Wistar derieved SPF Bred rats. Groups of ten male and ten female 6-wk-old rats received test chemical in the drinking-water (tap-water) at levels of 0, 100, 300, 1000 and 3000mg/litre for a period of 13 week. The potassium concentration in the nitrite solutions was equalized by adding potassium chloride (KCL) up to the potassium level of the 3000 mg /litre solution. An additional group of ten males and ten females received drinking-water supplemented with KCI only, at an amount resulting in a potassium concentration equivalent to that of the 3000 mg /litre solution. No mortality observed and the rats appeared to be healthy throughout the study. Ophthalmoscopic examination did not reveal any differences between the test rats and controls that could be ascribed to treatment. Body weight, food intake and food efficiency were decreased at 3000-mg/litre level in males, while liquid intake was decreased in males given 1000 and 3000 mg/litre and in females given 3000 mg/litre. There was a significant increase in the methaemoglobin concentration in animals given 3000 mg/litre, while slight decreases in red blood cell variables occurred at the 1000 and 3000 mg/litre dose. No impaired renal function was observed in any of the test groups, although the relative weight of the kidneys and the plasma urea nitrogen level was increased at 3000 mg/litre. There was a slight decrease in plasma alkaline phosphatase activity at 3000 mg/litre. A small amount of nitrite was present in the saliva of the rats receiving 3000 mg/litre but there was no evidence of increased mutagenic activity in the urine of these rats. Interestingly, hypertrophy of the adrenal zone glomerulosa was observed in all test groups, the incidence and degree being dose related. It was concluded that in the study reported here the NOEL is lower than I00 mg /litre in the drinking-water, which is equivalent to a level lower than 10 mg /kg body weight/day and a NOAEL of 300 mg/L drnking water was observed.

A 13 week repeated oral toxicity test was performed on Weanling Wistar derived SPF-bred rats (Bor; WlSW). A dose range of 0, 12.5, 25, 50, 100 and 3000 mg/l was admistered to nine dose groups consisting of 10 male and 10 female rats each via drinking water. There were no noticeable differences in appearance or behaviour between the treated rats and the controls during the experimental period. Body weights were significantly increased in males of the 12.5 mg KNO]litre group, which is in agreement with the higher food intake in this group. The results obtained in this study with the 100 and 3000 mg/litre levels of potassium nitrite in drinking water are comparable with those obtained at the same levels in the previous 90-day study (Til et al., 1988), although the effects on red blood cell variables at 3000 mg/litre and the incidence of hypertrophy of the zona glomerulosa of the adrenals at 100 and 3000 mg/litre were somewhat less pronounced than in the previous study at the same levels. Based on all the available data, and from the observations and conclusion, the NOAEL and LOAEL for the test chemical, was found to be 100 mg/l and 3000 mg/l, respectively.

Repeated dose toxicity: Inhalation

According to column 2 of Annex VIII, exposure by inhalation route is negligible on account of high boiling points (as has been informed in the boiling point that is greater than 300 °C).

 

Repeated dose toxicity: Dermal

The acute dermal toxicity value for test chemical is >2000 mg/kg body weight. Considering this, the end point for repeated dermal toxicity is considered as waiver.

Justification for classification or non-classification

Based on the animal data available, the test chemical is non-toxic and observed to be safe after repeated exposures. Hence, the test chemical is like to be 'unclassified' as per CLP classification.