Phenyl isocyanate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

supporting 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:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.01 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: mortality, reproduction rate, appearance of first offspring

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.004 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

other: mortality, reproduction rate, appearance of first offspring

Conclusions:

For aniline a 21d-NOEC of 0.004 mg/L was extrapolated for reproduction of Daphnia magna.

Executive summary:

In a semi-static test (three renewals per week) the long-term toxicity of aniline to Daphnia magna was studied at 25 °C. Eight test concentrations ranging nominally from 0.1 μg/L to 316 μg/L were employed. A 21-day NOEC for reproduction of 10 μg/L based on nominal concentration was found. As it was not possible to analyse the real aniline concentration in the samples (detection limit of the used method was 0.1 mg/L). An additional test vessel without daphnids and food but with a nominal aniline concentration of 316 μg/L was employed. After 2 days the aniline concentration in this sample was only 40 to 60% of the nominal concentration. Therefore, a NOEC value of 4 μg/L is extrapolated from this recovery rate. This extrapolation does not take into account the possibly enhanced degradation of aniline in the presence of daphnid food.

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:

long-term toxicity to aquatic invertebrates

Type of information:

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

Adequacy of study:

supporting study

Study period:

1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Data from EU Risk 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

Qualifier:

according to guideline

Guideline:

other: Umweltbundesamt, Provisional procedure: prolonged toxicity test using Daphnia magna (dated 01.01.1984)

Deviations:

no

Principles of method if other than guideline:

German Federal Environmental Agency internal method, comparable to OECD TG 211.

GLP compliance:

no

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

- dilution water: synthetic freshwater according to German Industrial Standard DIN 38412, Part 1 and Part 11 (1982): 11.76 g/L CaCl2*2H2O, 4.93 g/L MgSO4*7H2O, 2.59 g/L NaHCO3, 0.23 g/L KCl, oxygen-saturated, pH 8.0 +- 0.2 - stock solution of test substance: 2000 mg/L (dilution water heated to 30 °C)

Test organisms (species):

Daphnia magna

Details on test organisms:

- test animals: Daphnia magna (IRCHA strain)
- age: 24 h 
- 20-30 animals in 40 2-L beakers filled with >= 1.6 L tap water (hardness: 285.76 mg/L as CaCO3; pH 7.6-7.7; oxygen-saturated)      
- temperature: 20 °C      
- fluorescent light (9 h light : 15 h dark)      
- offspring removed daily from cultures      
- feeding: dried algae (Scenedesmus sp.; 9 g/L, 2 mL/beaker)

Test type:

semi-static

Water media type:

freshwater

Total exposure duration:

21 d

Hardness:

285.76 mg/L as CaCO3

Test temperature:

25 +- 1 °C

pH:

7.6 - 7.7

Details on test conditions:

- test vessel: closed
- test concentration: 8-1000 mg/L, dilution ratio: 1:2
- replicates: 4/concentration, 1 animal/50 mL, 20 animals/conc.
- semistatic conditions (3 times/week)
- feeding: 3 times/week (Tetramin fish feed)
- illumination: fluorescent light (9 h light : 15 h dark)
- temperature: 25 +- 1 °C
- observations: 3 times/week: dead/immobile animals, offspring, pH, dissolved oxygen
- analytical monitoring of test substance concentration in stock solution, test vessels, and blanks

Reference substance (positive control):

not specified

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.01 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: mortality, reproduction rate, appearance of first offspring

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.004 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

other: mortality, reproduction rate, appearance of first offspring

Conclusions:

For aniline a 21d-NOEC of 0.004 mg/L was extrapolated for reproduction of Daphnia magna.

Executive summary:

In a semi-static test (three renewals per week) the long-term toxicity of aniline to Daphnia magna was studied at 25 °C. Eight test concentrations ranging nominally from 0.1 μg/L to 316 μg/L were employed. A 21-day NOEC for reproduction of 10 μg/L based on nominal concentration was found. As it was not possible to analyse the real aniline concentration in the samples (detection limit of the used method was 0.1 mg/L). An additional test vessel without daphnids and food but with a nominal aniline concentration of 316 μg/L was employed. After 2 days the aniline concentration in this sample was only 40 to 60% of the nominal concentration. Therefore, a NOEC value of 4 μg/L is extrapolated from this recovery rate. This extrapolation does not take into account the possibly enhanced degradation of aniline in the presence of daphnid food.

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 the substance, long-term toxicity results for aquatic invertebrates of the hydrolysis product aniline is taken into account for assessment. Three Daphnia long-term results (21 d) are available that are regarded of equal value: NOEC = 0.016 mg/L, 0.004 mg/L and 0.024 mg/L .
However, the lowest of the three NOECs was taken as key result to present the most conservative situation.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.004 mg/L

Additional information

Due to the rapid hydrolysis of the phenyl isocyanate, long-term toxicity results for aquatic invertebrates of the hydrolysis product aniline are taken into account for assessment, based on the following assumption:

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.