Phenyl isocyanate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

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

Adequacy of study:

key study

Study period:

no data

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:

Uptake and elimination kinetics experiments were performed as described by:
Kalsch et al. (1990). Uptake, elimination and bioconcentration of ten anilines in zebrafish Brachydanio rerio. Chemosphere 22: 351-363

GLP compliance:

not specified

Radiolabelling:

yes

Vehicle:

no

Details on preparation of test solutions, spiked fish food or sediment:

- solution of test substance in charcoal-filtered tapwater

Test organisms (species):

Danio rerio (previous name: Brachydanio rerio)

Details on test organisms:

TEST ORGANISM
- Common name: zebrafish
- Source: West Aquarium, Bad Lauterberg, FRG
- Age at study initiation (mean and range, SD): 150-450 mg

Route of exposure:

aqueous

Test type:

static

Water / sediment media type:

natural water: freshwater

Test temperature:

26°C

pH:

8.1+/-0.1

Details on test conditions:

- 60 fishes of both sexes were exposed under static conditions to 5L of a 0.2 µg/L solution of the test substance
- animals were not fed during the experiment
- chemical exposure under static conditions until steady state of uptake and elimination
- afterwards fish were kept in clean water under flow-through conditions (10 L/h)
- amount of radioactivity kept constant by adding stock solution, if required
- To determine the concentration of the test substance in fish, samples of 3 fishs were removed, weighed and combusted in a sample oxidizer

Nominal and measured concentrations:

test concentration: 0.2 µg/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

BASIS INFORMATION
- Calculated logPow: 0.9 (Arnold et al., 1990. QSAR)

BASIS FOR CALCULATION OF BCF
- Uptake data are fitted to a monophasic time course (Branson et al., 1975; Bishop and Maki, 1980; Call et al., 1980), according to a one-compartment model for the fish
- Since an obviously biphasic elimination occured, elimination data can be described by a two-compartment model for the fish (Nagel and Ulrich, 1980; Spacie and Hamelink, 1982)
- Calculation of the uptake rate constant is carried out according to Nagel (1988).

Type:

BCF

Value:

2.6 L/kg

Remarks on result:

other: +/- 0.06

Details on kinetic parameters:

- Uptake rate constant (k1): 11.1 +/- 3.2 /h

Metabolites:

- The only metabolite identified in water is the corresponding acetanilide. It was also detected in the ethanolic extract of fish.
- N-Acetylation of the primary amino group by acetyl CoA-dependent N-acetyltransferase is reviewed for several species by King and Glowinski (1983) and by Caldwell (1986).

- result in accordance with measured log Kow of 0.9
- no indication of a bioaccumulation potential due to exposure via water

Validity criteria fulfilled:

not specified

Conclusions:

The aquatic bioaccumulation of aniline was measured, yielding a BCF of 2.6 L/kg wwt+/- 0.06 L/kg wwt.

Executive summary:

The aquatic bioaccumulation of aniline was measured as BCF of 2.6 L/kg wwt+/- 0.06 L/kg wwt.

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:

bioaccumulation in aquatic species: 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

Type:

BCF

Value:

2.6 L/kg

Remarks on result:

other: +/- 0.06

Details on kinetic parameters:

- Uptake rate constant (k1): 11.1 +/- 3.2 /h

Metabolites:

- The only metabolite identified in water is the corresponding acetanilide. It was also detected in the ethanolic extract of fish.
- N-Acetylation of the primary amino group by acetyl CoA-dependent N-acetyltransferase is reviewed for several species by King and Glowinski (1983) and by Caldwell (1986).

- result in accordance with measured log Kow of 0.9
- no indication of a bioaccumulation potential due to exposure via water

Conclusions:

The aquatic bioaccumulation of aniline was measured, yielding a BCF of 2.6 L/kg wwt+/- 0.06 L/kg wwt.

Executive summary:

The aquatic bioaccumulation of aniline was measured as BCF of 2.6 L/kg wwt+/- 0.06 L/kg wwt. The only metabolite identified in water is the corresponding acetanilide. It was also detected in the ethanolic extract of fish. Radioactivity was measured by a liquid-scintillation spectrometer and biotransformation products were analyzed by HPLC.

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 aquatic bioaccumulation of the hydrolysis product aniline was measured, yielding a BCF of 2.6 L/kg wwt.

Key value for chemical safety assessment

BCF (aquatic species):

2.6 L/kg ww

Additional information

Due to the rapid hydrolysis of phenyl isocyanate and the absence of bioaccumulation data for the substance, a read across approach is applied, 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.

For assessment, only the most reliable study using aniline as test substance is considered, to draw a conclusion on the bioaccumulation behaviour of phenyl isocyanate.

The aquatic bioaccumulation of aniline was measured, yielding a BCF of 2.6 L/kg wwt +/- 0.06 L/kg wwt.