Potassium nitrite

Endpoint summary

Description of key information

Short term toxicity to fish

Short term toxicity to fish was conducted for 96 hrs for assessing the effect of test chemical. The test was performed in accordance to OECD guideline No. 203 “Fish Acute Toxicity Test”. Zebra fish (Danio rerio) of average weight 0.045 g and average length of 1.4 cm was used as a test organism for the study. Test fishes were kept in a static tank in tap water passed through reverse osmosis system, under natural conditions along with proper feed and aeration. During the housing period, test fishes were fed once daily with standard brand fed. The test conditions during the housing of the test organisms were oxygen content of 7.6 mg/l, pH 7.5, water temperature 23.9°C and under a photoperiod of 16:8 hr light: dark conditions, respectively. Test was performed using test chemical concentrations of 0, 6.25 mg/l, 12.5 mg/l, 25 mg/l, 50 mg/l and 100 mg/l, respectively. Total 8 fishes were exposed to test chemical in a 5 lit bowl aquaria containing 4 liters of potable water. The test vessels were placed in a room at a temperature of 23.9°C, pH 7.2, hardness of water 155.5 mg of CaCO3 and under a photoperiod of 16:8 hr light: dark conditions, respectively. Aeration in test vessels was provided 1 day before the start of the experiment. No mortalities were observed in the control. Test fishes were moving slowly as compared to control. On the basis of effect of test chemical on mortality of the test organism, the median lethal concentration (LC50 (96 h)) was determined to be ≥100 mg/l. Thus, test chemical chemical was considered as non-toxic to aquatic fishes at environmental relevant concentrations and hence, considered to be not classified as per the CLP classification criteria.

Short term toxicity to aquatic invertebrates

Short term toxicity to aquatic invertebrate study was conducted for 96 hrs for assessing the effect of test chemical. Test conducted in accordance with OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test). Daphnia magna was used as a test organism. The stock solution was prepared by dissolving 1g of the test substance in 1L of ADaM’s media. Achieving test concentrations of 6.25mg/L, 12.5mg/L, 25mg/L, 50mg/L, 100mg/L, respectively was prepared from stock solution. 10 Daphnids was added per concentration. Test conducted under the static system at a temperature of 21.2 ± 0.1°C, hardness of 153.5 mg of CaCO3, dissolved oxygen of 7.1 mg/l and pH of 7.5, respectively for 48 hours. The effect of test chemical was calculated on the basis of immobility observations of Daphnia magna. Observations including (immobility, pH, Temperature, dissolved oxygen content) were recorded in the interval of 24 and 48 hours. After the exposure of test chemical with aquatic invertebrates Daphnia magna for 48 hours, immobility were observed and the EC50 value was determine to be > 100 mg/l. Based on the EC50 value, it can be consider that the chemical was nontoxic and hence, considered to be not classified as per the CLP classification criteria.

Toxicity to aquatic algae and cyanobacteria

A freshwater algal growth inhibition test was conducted for 72 hrs for assessing the effect of test chemical on green algae. The test was performed in accordance to OECD guideline No. 201 – Alga growth inhibition test under static condition. Pseudokirchneriella subcapitata (green algae) was used as a test organism for the study. Initial cell density of the culture was kept at 1 х 10000 cells/ml. OECD medium was used as a growth medium for the study. The test solution was prepared by dissolving 500 mg of test chemical in 500 mL of OECD medium to get the final concentration of 1000 mg/L, which was then analytically determined. The final solubility value obtained after analytical detection is 123.55 mg/L. To get the maximum dissolution, stock solution was stirred for To have a better growth and visibility of cells, the initial cell count of the culture was kept 10,000 cells/ml. Care was taken to have a homogeneous solution for the experiment. Nominal test chemical concentration used for the study were 0, 0.25, 0.5, 1, 2, 4 and 8 mg/L. Green algae were exposed to various nominal concentration of test chemical in 100 ml conical flasks. Test vessel were placed in orbital shaking incubator for 72 hrs at a room at a temperature of 22±2°C under a photoperiod of 16:8 hr light: dark conditions and with a continuous uniform illumination of 3000 -4000 lux light intensity, respectively. The speed of the orbital shaking incubator was set at a 120 revolutions per minute throughout the study period. Control (containing only the test medium) was also included in the test.One positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. The cultures were observed daily with the helpof an automated cell counter to verify a normal and healthy appearance of the algae cells and also to observe any abnormal appearance of the algae. Apart from this, the cell count of each test vessel was also noted with the help of an automated cell counter. In the control vessel, all cells appeared healthy,round and green throughout the study duration. The microscopic observations were also noted in each of the test vessel. EC50 value of the reference substance was determined to be 0.75 mg/l. Based on the growth inhibition of green algae by the test chemical, the EC50 was determined to be 0.971 mg/l (95% CI – 0.513 to 1.839 mg/l). Thus, based on the EC50 value, test chemical can be considered as toxic to aquatic organisms at environmental relevant concentrations and hence, considered to be classified in ‘’aquatic acute category 1’’ as per the CLP classification criteria.

Toxicity to microorganisms

On the basis of the experimental studies of read across chemical and applying the weight of evidence approach and by evaluating the effect of test chemical on test organism, the EC50 value can be expected to be >180 mg/l.

Additional information

Short term toxicity to fish

Experimental study of the target chemical and various supporting weight of evidence studies for its read across analogue were reviewed for short term toxicity to fish endpoint which are summarized as below:

 

In an experimental weight of evidence study from study report, the short term toxicity to fish was conducted for 96 hrs for assessing the effect of test chemical. The test was performed in accordance to OECD guideline No. 203 “Fish Acute Toxicity Test”. Zebra fish (Danio rerio) of average weight 0.045 g and average length of 1.4 cm was used as a test organism for the study. Test fishes were kept in a static tank in tap water passed through reverse osmosis system, under natural conditions along with proper feed and aeration. During the housing period, test fishes were fed once daily with standard brand fed. The test conditions during the housing of the test organisms were oxygen content of 7.6 mg/l, pH 7.5, water temperature 23.9°C and under a photoperiod of 16:8 hr light: dark conditions, respectively. Test was performed using test chemical concentrations of 0, 6.25 mg/l, 12.5 mg/l, 25 mg/l, 50 mg/l and 100 mg/l, respectively. Total 8 fishes were exposed to test chemical in a 5 lit bowl aquaria containing 4 liters of potable water. The test vessels were placed in a room at a temperature of 23.9°C, pH 7.2, hardness of water 155.5 mg of CaCO3 and under a photoperiod of 16:8 hr light: dark conditions, respectively. Aeration in test vessels was provided 1 day before the start of the experiment. No mortalities were observed in the control. Test fishes were moving slowly as compared to control. On the basis of effect of test chemical on mortality of the test organism, the median lethal concentration (LC50 (96 h)) was determined to be ≥100 mg/l. Thus, test chemical chemical was considered as non-toxic to aquatic fishes at environmental relevant concentrations and hence, considered to be not classified as per the CLP classification criteria.

 

In a supporting weight of evidence study from authoritative database and other reliable source (1976), short term toxicity to fish study was carried out. Poecilia reticulata (Guppy) of 8.7 mm (6.7 to 10.5 mm) length was used as a test organism. The test organism were grown, bred and maintained in a 20 gallon stainless steel-glass aquaria until testing. Each aquarium was equipped with under-gravel and outside filters, an airstone, and plants to help the fry in hiding from adults. The tanks were kept in an air-conditioned room and the water temperature was maintained with the heaters at 77° to 80°F. The fish were fed at least once but usually twice daily with dried commercial food (TetraMin or Biorell) or brine shrimp hatched from eggs obtained from Metaframe Corporation (San Francisco Brand). The aquaria were kept clean of unconsumed food and other debris by periodic siphoning and partial replacement of the water*. The fish w.ere observed daily for the presence of diseases and dead specimens. They were acclimated to the test conditions for 48 hours during which time the tanks were aerated continuously. Fishes were not fed during the acclimation period. Test fishes were not fed during the study. Test fishes (10 or 20 fish/vessel) were exposed to different conc. of test chemical (0, 191.3, 199, 218.8, 266.5 mg/l) in a five-gallon rectangular glass aquaria provided with a loose fitting plastic cover to prevent evaporation of the water. The fish were distributed to the test aquaria in the random fashion. Columbus city tap water was used to maintain the fish and as experimental water. The tap water was vigorously aerated for at least one week and then was passed through a bed of activated carbon to remove residual chlorine. Finally the water was pumped through 8-micron Whatman filter tube to remove precipitated iron. Sodium hydroxide or hydrochloric acid was added to the test water to adjust pH as needed. Test conditions involve a pH of 7.39 to 7.57, temperature of 24 to 26°C, dissolved oxygen of 7.3 to 8.2 and hardness of 160 mg/l as CaCO3 in a continuous light supplied by fluorescent and incandescent bulb. The number of dead fish in the test tanks were observed and recorded several times daily. With all tests the 24, 48, 72 and 96 hour observations were obtained and recorded. Dead fish were removed immediately with a small net. Based on the effect of test chemical on mortality of the test fish, the 96 hr LC50 value was determined to be 190 mg/l. Thus, based on the LC50 value, test chemical was considered as non-toxic to aquatic fishes and hence, considered to be ‘not classified’ as per CLP classification criteria.

 

For the test chemical, an acute toxicity to fish study was carried out. Study was performed under static conditions for a period of 96 hrs. Micropterus salmoides (Largemouth bass) of 2.8 gm weight was used as a test organism. Test conditions involve a pH of 7.7 to 8.2, temperature of 23°C, dissolve oxygen of 8.1 mg/l and hardness of 202.4 mg/l as CaCO3, respectively. On the basis of the effect of test chemical on mortality of the test organism, the 96 hr LC50 value was determined to be 140.2 mg/l. Thus, based on the LC50 value, test chemical was considered as non-toxic to aquatic fishes and hence, considered to be ‘not classified’ as per CLP classification criteria.

 

On the basis of the above results, test chemical can be considered non-toxic to aquatic fishes at environmental relevant concentrations and hence, considered to be 'not classified' as per the CLP classification criteria.

Short term toxicity to aquatic invertebrates

Experimental study of the target chemical and supporting weight of evidence study for its read across analogue were reviewed for short term toxicity to aquatic invertebrate endpoint which are summarized as below:

 

In an experimental weight of evidence study from study report, the short term toxicity to aquatic invertebrate study was conducted for 96 hrs for assessing the effect of test chemical. Test conducted in accordance with OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test). Daphnia magna was used as a test organism. The stock solution was prepared by dissolving 1g of the test substance in 1L of ADaM’s media. Achieving test concentrations of 6.25mg/L, 12.5mg/L, 25mg/L, 50mg/L, 100mg/L, respectively was prepared from stock solution. 10 Daphnids was added per concentration. Test conducted under the static system at a temperature of 21.2 ± 0.1°C, hardness of 153.5 mg of CaCO3, dissolved oxygen of 7.1 mg/l and pH of 7.5, respectively for 48 hours. The effect of test chemical was calculated on the basis of immobility observations of Daphnia magna. Observations including (immobility, pH, Temperature, dissolved oxygen content) were recorded in the interval of 24 and 48 hours. After the exposure of test chemical with aquatic invertebrates Daphnia magna for 48 hours, immobility were observed and the EC50 value was determine to be > 100 mg/l. Based on the EC50 value, it can be consider that the chemical was nontoxic and hence, considered to be not classified as per the CLP classification criteria.

 

For the test chemical from authoritative databases and secondary sources, short term toxicity to aquatic invertebrate study was carried out for 48 hrs for assessing the effect of test chemical. Test chemical concentrations were not verified analytically. Study was performed using Daphnia magna (Water flea) as a test organism under static conditions at a temperature of 21-25°C. Dilution water used in the study was glass-wool filtered University Lake water. On the basis of the effect on mobility of the test daphnids, the 48 hr LC50 value was determined to be 490 mg/l. Based on the LC50 value, it can be consider that the chemical was non-toxic and hence, considered to be not classified as per the CLP classification criteria.

 

In a supporting weight of evidence study, short term toxicity to aquatic invertebrate study was carried out for 48 hrs for assessing the effect of test chemical (Secondary source, 2000). Study was carried out in accordance with the DIN 38412 part 11. Test chemical concentrations were verified analytically. Analytical details was not specified in the published literature. Study was performed using Daphnia magna (Water flea) as a test organism under static conditions. On the basis of the effect on mobility of the test daphnids, the 48 hr EC0, EC50 and EC100 value was determined to be 587, 825 and 1010 mg/l, respectively. Based on the EC50 value, it can be consider that the chemical was non-toxic and hence, considered to be not classified as per the CLP classification criteria.

 

On the basis of the above results, test chemical was considered as non-toxic to aquatic invertebrates at environmental relevant concentrations and hence, considered to be 'not classified' as per the CLP classification criteria.

Toxicity to aquatic algae and cyanobacteria

A freshwater algal growth inhibition test was conducted for 72 hrs for assessing the effect of test chemical on green algae. The test was performed in accordance to OECD guideline No. 201 – Alga growth inhibition test under static condition. Pseudokirchneriella subcapitata (green algae) was used as a test organism for the study. Initial cell density of the culture was kept at 1 х 10000 cells/ml. OECD medium was used as a growth medium for the study. The test solution was prepared by dissolving 500 mg of test chemical in 500 mL of OECD medium to get the final concentration of 1000 mg/L, which was then analytically determined. The final solubility value obtained after analytical detection is 123.55 mg/L. To get the maximum dissolution, stock solution was stirred for To have a better growth and visibility of cells, the initial cell count of the culture was kept 10,000 cells/ml. Care was taken to have a homogeneous solution for the experiment. Nominal test chemical concentration used for the study were 0, 0.25, 0.5, 1, 2, 4 and 8 mg/L. Green algae were exposed to various nominal concentration of test chemical in 100 ml conical flasks. Test vessel were placed in orbital shaking incubator for 72 hrs at a room at a temperature of 22±2°C under a photoperiod of 16:8 hr light: dark conditions and with a continuous uniform illumination of 3000 -4000 lux light intensity, respectively. The speed of the orbital shaking incubator was set at a 120 revolutions per minute throughout the study period. Control (containing only the test medium) was also included in the test.One positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. The cultures were observed daily with the helpof an automated cell counter to verify a normal and healthy appearance of the algae cells and also to observe any abnormal appearance of the algae. Apart from this, the cell count of each test vessel was also noted with the help of an automated cell counter. In the control vessel, all cells appeared healthy,round and green throughout the study duration. The microscopic observations were also noted in each of the test vessel. EC50 value of the reference substance was determined to be 0.75 mg/l. Based on the growth inhibition of green algae by the test chemical, the EC50 was determined to be 0.971 mg/l (95% CI – 0.513 to 1.839 mg/l). Thus, based on the EC50 value, test chemical can be considered as toxic to aquatic organisms at environmental relevant concentrations and hence, considered to be classified in ‘’aquatic acute category 1’’ as per the CLP classification criteria.

Toxicity to microorganisms

Data available of the read across chemicals has been reviewed to determine the effect of the test chemical on microorganisms. The studies are as mentioned below:

 

Toxicity to microorganisms study was carried out. Study was performed in accordance with the ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation) for 30 mins. Activated sludge (adapted) was used as a test inoculum. With proper introduction to adapted biological Purification plants are not disruptions to the dismantling activity of the activated sludge to be expected. No respiratory inhibition of adapted activated sludge up to to the highest tested concentration of 1800 mg/l. Thus, based on effect on total respiration of the test inoculum activated sludge, the 30 mins EC0 and EC50 value was determined to be 1800 and >1800 mg/l, respectively.

 

Another toxicity to microorganisms study was carried out. Study was performed using Escherichia coli as a test organism for a period of 96 hrs. Based on effect on growth inhibition of the test bacteria, growth inhibition threshold value was determined to be 180 mg/l. Thus, based on reviewer judgement, 96 hr EC50 value can be considered as >180 mg/l.

 

On the basis of the experimental studies of read across chemical and applying the weight of evidence approach and by evaluating the effect of test chemical on test organism, the EC50 value can be expected to be >180 mg/l.

On the basis of the available information of aquatic toxicity studies, it can be concluded that the test chemical can be considered as toxic to aquatic organismsat environmental relevant concentrations and hence, considered to be classified in ‘’aquatic acute category 1’’ as per the CLP classification criteria.