Phenyl isocyanate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

Deviations:

no

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

actual concentration of each flask wase determined at the beginning and at the end of the test

Vehicle:

no

Details on test solutions:

- stock solutions were prepared directly in the culture medium, and were stirred for at least 24 hours
- stock solutions were used to prepare fresh test solutions by dilution with medium

Test organisms (species):

Chlorella pyrenoidosa

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

22 °C

pH:

7.4

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

156 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

175 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

73 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

90 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Results relate to nominal concentrations, as analytical monitoring shows that concentrations may drop down to 40% of the nominal ones.

Conclusions:

The toxicity to aquatic algae (chlorella pyrenoidosa) of aniline was tested according to OECD guideline 201 "Alga, Growth Inhibition Test, 1984". During 72 hours an EC50 of 175 mg/L and a NOEC of 90 mg/L were determined.

Executive summary:

The toxicity to aquatic algae (chlorella pyrenoidosa) of aniline was tested according to OECD guideline 201 "Alga, Growth Inhibition Test, 1984". During 72 hours an EC50 of 175 mg/L and a NOEC of 90 mg/L were 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:

toxicity to aquatic algae and cyanobacteria

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:

72 h

Dose descriptor:

LOEC

Effect conc.:

156 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

175 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

73 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

90 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Results relate to nominal concentrations, as analytical monitoring shows that concentrations may drop down to 40% of the nominal ones.

Conclusions:

The toxicity to aquatic algae (chlorella pyrenoidosa) of aniline was tested according to OECD guideline 201 "Alga, Growth Inhibition Test, 1984". During 72 hours an EC50 of 175 mg/L and a NOEC of 90 mg/L were detemined.

Executive summary:

The toxicity to aquatic algae (chlorella pyrenoidosa) of aniline was tested according to OECD guideline 201 "Alga, Growth Inhibition Test, 1984". During 72 hours an EC50 of 175 mg/L and a NOEC of 90 mg/L were 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

The toxicity to aquatic algae (chlorella pyrenoidosa) of the hydrolysis product aniline was tested according to OECD guideline 201 "Alga, Growth Inhibition Test, 1984". During 72 hours an EC50 of 175 mg/L and a NOEC of 90 mg/L was shown.

Key value for chemical safety assessment

EC50 for freshwater algae:

175 mg/L

EC10 or NOEC for freshwater algae:

90 mg/L

Additional information

Concerning toxicity towards aquatic algae, there are no data available for phenyl isocyanate. Due to the rapid hydrolysis of the substance, results from its hydrolysis product aniline is taken into account for assessment, based on the justification for read-across. The most reliable and sensitive study is a toxicity test to the aquatic algae (chlorella pyrenoidosa) using aniline as test susbtance.

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.