Phenyl isocyanate

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

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:

According to handbook data, isocyanates react rapidly with water forming aminic structures as well as carbamic acids, which are mostly unstable, and ureas under release of carbon dioxide. Monitoring the amine formation in hydrolysis studies gives a picture of the degradation of the isocyanate. This behaviour of isocyanates has been used in studies to determine the rate of degradation*. In Guidance on IR & CSA Chapter R.6 it is mentioned that degradation products instead of parent substance can be investigated for ecotoxicological effects if the hydrolysis is very rapidly (t1/2 <1 h), OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) and Guidance on IR & CSA Chapter R.7b state the same. As phenyl isocyanate hydrolyses to aniline this is the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of phenyl isocyanate. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.
* Bayer Industry Services (2004), 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.
Bayer Industry Services (2003), Isopropyl isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.

Reason / purpose for cross-reference:

read-across: supporting information

Principles of method if other than guideline:

Method: Acute Fish Toxicity, no guideline mentioned

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

not specified

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Salmo gairdneri (renamed to: Oncorhynchus mykiss), juveniles
- average length (mm): 29 +/- 3
- average weight (g): 0.25 +/- 0.06

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

7 d

Hardness:

dilution water: hard well water; total hardness (mg/l as CaCO3): 250 (240-260)

Test temperature:

15+/-1°C

pH:

7.1-7.7

Dissolved oxygen:

> 80% air saturation

Nominal and measured concentrations:

0, 7.9, 12.6 and 19.9 mg/L (nominal)
Effective concentrations ranged from 96.3 % to 100.8 % of nominal values in the freshly prepared media and from 91.4 % to 97.9 % of nominal values in the media after 3 d of exposure.

Details on test conditions:

TEST SYSTEM
- Test vessel: 2-L glass flask
- flow-through
- Water replacement time: 20 mL/min.
- No. of organisms per vessel: 10 fish/vessel
- No. of vessels per concentration (replicates): no data
- No. of vessels per control (replicates): no data
- test was run in duplicate

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: hard well water
- ammonia (97 h, mg/l): max. 0.25

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): temperature, pH, dissolved oxygen, test item concentrations (absorption spectrometry), ammonia (Nesslerisation)

Reference substance (positive control):

not specified

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

28.3 mg/L

Remarks on result:

other: 95% confidence limits: 18.3-43.7 mg/L

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

10.6 mg/L

Remarks on result:

other: 95% confidence limits: 7.4-15.3 mg/L

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

8.2 mg/L

Remarks on result:

other: 95% confidence limits: 4.1-16.3 mg/L

Details on results:

Although the test substance solutions have not been filtrated, it can be concluded that aniline has been dissolved completely in water as the water solubility is high with 35 g/L and the maximum concentration of anilin in the test was 19.9 mg/L (nominal).

Sublethal observations / clinical signs:

Test substance concentrations (% of mean nominal value):
whole experiment after 3 d
tanks without fish: 100.8 +/- 8.6, 97.9 +/- 4.3
tanks with fish: 96.3 +/- 13.7, 91.4 +/- 6.7

Mean concentration of ammonia in test flasks with fish (mg/L): Nominal concentration of aniline (mg/L) 19.9, 12.6, 7.9; Ammonia (mg/L) 0.22, 0.26, 0.28

Concentration of ammonia in test flasks without fish (mg/L): about 0.03

The authors discussed, that trout can detach the amine moiety from aniline and excrete this in form of ammonia.

Validity criteria fulfilled:

yes

Remarks:

The dissolve oxygen concentration was above 60 % (> 80 %), deviation from nominal concentration is < 20 %

Conclusions:

After 96 h of exposure a LC50 of 28.3 mg/L was determined.

Executive summary:

The acute toxicity of Aniline toward fish (Oncorhynchus mykiss (previous: Salmo gairdneri)) was tested in a flow-through study. The LC50-value for 96 h is reported, too. Groups of 10 fish were exposed to three concentrations of aniline (7.9 mg/L, 12.6 mg/L, 19.9 mg/L) and control without aniline. Effective concentrations ranged from 96.3 % to 100.8 % of nominal values in the freshly prepared media and from 91.4 % to 97.9 % of nominal values in the media after 3 d of exposure. The test was run in duplicate. After 96 h of exposure a LC50 of 28.3 mg/L was determined.

According to handbook data, isocyanates react rapidly with water forming aminic structures as well as carbamic acids, which are mostly unstable, and ureas under release of carbon dioxide. Monitoring the amine formation in hydrolysis studies gives a picture of the degradation of the isocyanate. This behaviour of isocyanates has been used in studies to determine the rate of degradation*. In Guidance on IR & CSA Chapter R.6 it is mentioned that degradation products instead of parent substance can be investigated for ecotoxicological effects if the hydrolysis is very rapidly (t1/2 <1 h), OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) and Guidance on IR & CSA Chapter R.7b state the same. As phenyl isocyanate hydrolyses to aniline this is the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of phenyl isocyanate. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004), 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.

Bayer Industry Services (2003), Isopropyl isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

According to handbook data, isocyanates react rapidly with water forming aminic structures as well as carbamic acids, which are mostly unstable, and ureas under release of carbon dioxide. Monitoring the amine formation in hydrolysis studies gives a picture of the degradation of the isocyanate. This behaviour of isocyanates has been used in studies to determine the rate of degradation*. In Guidance on IR & CSA Chapter R.6 it is mentioned that degradation products instead of parent substance can be investigated for ecotoxicological effects if the hydrolysis is very rapidly (t1/2 <1 h), OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) and Guidance on IR & CSA Chapter R.7b state the same. As phenyl isocyanate hydrolyses to aniline this is the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of phenyl isocyanate. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.
* Bayer Industry Services (2004), 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.
Bayer Industry Services (2003), Isopropyl isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.

Reason / purpose for cross-reference:

read-across source

Duration:

48 h

Dose descriptor:

LC50

Effect conc.:

28.3 mg/L

Remarks on result:

other: 95% confidence limits: 18.3-43.7 mg/L

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

10.6 mg/L

Remarks on result:

other: 95% confidence limits: 7.4-15.3 mg/L

Duration:

7 d

Dose descriptor:

LC50

Effect conc.:

8.2 mg/L

Remarks on result:

other: 95% confidence limits: 4.1-16.3 mg/L

Details on results:

Although the test substance solutions have not been filtrated, it can be concluded that aniline has been solved in total as the water solubility is high with 35 g/L and the maximum concentration of anilin in the test was 19.9 mg/L (nominal).

Validity criteria fulfilled:

yes

Remarks:

The dissolve oxygen concentration was above 60 % (> 80 %), deviation from nominal concentration is < 20 %

Conclusions:

After 96 h of exposure a LC50 of 28.3 mg/L was determined.

Executive summary:

The acute toxicity of aniline toward fish (Oncorhynchus mykiss (previous: Salmo gairdneri)) was tested in a flow-through study. The LC50-value for 96 h is reported, too. Groups of 10 fish were exposed to three concentrations of aniline (7.9 mg/L, 12.6 mg/L, 19.9 mg/L) and control without Aniline. Effective concentrations ranged from 96.3 % to 100.8 % of nominal values in the freshly prepared media and from 91.4 % to 97.9 % of nominal values in the media after 3 d of exposure. The test was run in duplicate. After 96 h of exposure a LC50 of 28.3 mg/L was determined.

According to handbook data, isocyanates react rapidly with water forming aminic structures as well as carbamic acids, which are mostly unstable, and ureas under release of carbon dioxide. Monitoring the amine formation in hydrolysis studies gives a picture of the degradation of the isocyanate. This behaviour of isocyanates has been used in studies to determine the rate of degradation*. In Guidance on IR & CSA Chapter R.6 it is mentioned that degradation products instead of parent substance can be investigated for ecotoxicological effects if the hydrolysis is very rapidly (t1/2 <1 h), OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) and Guidance on IR & CSA Chapter R.7b state the same. As phenyl isocyanate hydrolyses to aniline this is the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of phenyl isocyanate. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004), 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.

Bayer Industry Services (2003), Isopropyl isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.

Description of key information

Due to the rapid hydrolysis of phenyl isocyanate, results from the hydrolysis product aniline are also taken into account for assessment and the most conservative value is chosen.

The acute toxicity for aniline to fish (Oncorhynchus mykiss) was measured yielding a 96h-LC50 of 10.6 mg/L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

10.6 mg/L

Additional information

For aniline vaious fish species short term toxicity tests are available with 96h-LC50-values ranging form 10.6 mg/L to >100 mg/L. Due to the rapid phototransformation of aniline, results of toxicity tests using flow-through or semi-static conditions and/or measured concentrations were considered as more reliable. The lowest 96h-LC50 value was reported for Oncorhynchus mykiss.

A study with phenyl isocyanate is also available. However, as the substance hydrolyses rapidly to anilin and the resulting value for aniline was lower the latter was taken as a conservative approach.

According to handbook data, isocyanates react rapidly with water forming aminic structures as well as carbamic acids, which are mostly unstable, and ureas under release of carbon dioxide. Monitoring the amine formation in hydrolysis studies gives a picture of the degradation of the isocyanate. This behaviour of isocyanates has been used in studies to determine the rate of degradation*. In Guidance on IR & CSA Chapter R.6 it is mentioned that degradation products instead of parent substance can be investigated for ecotoxicological effects if the hydrolysis is very rapidly (t1/2 <1 h), OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) and Guidance on IR & CSA Chapter R.7b state the same. As phenyl isocyanate hydrolyses to aniline this is the ecotoxicological relevant species. Concluding, tests performed using the corresponding amine can equally be used to assess the ecotoxicological hazards of phenyl isocyanate. An underestimation of environmental hazards is thus avoided supporting a conservative and thus protective hazard assessment.

* Bayer Industry Services (2004), 4-chlorophenyl-isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300181. Leverkusen, Germany.

Bayer Industry Services (2003), Isopropyl isocyanate: Investigation on Stability in Aqueous Test Solutions. Project No: 200300095. Leverkusen, Germany.