Hexamethylene diisocyanate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

other: Commission Directive 88/302/EEC; Official Journal of the EC L 133, Part C

Principles of method if other than guideline:

corresponds for the most parts to the test method OECD 209

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Because of the rapid hydrolysis the test substance was added to 130 ml deionized water in different weights, treated 3 – 4 h by ultrasound and stirred overnight before testing (equilibration phase).

Test organisms (species):

activated sludge

Details on inoculum:

TEST ORGANISM:
- type: mixed population of different microorganisms
- origin: aeration tank of a waste water plant treating predominantly domestic sewage (Wupper area water authority, Germany)
- pretreatment: none
- pH-value: 6.8

Because of the strong respiration of the activated sludge only 0.32 g/l ss were used.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

No data

Test temperature:

the values varied between 20. 9 and 21.0 °C

pH:

the values varied between 8.2 and 8.4

Dissolved oxygen:

oxygen (mg/l) at O2-start: the values varied between 6.0 and 8.3
oxygen (mg/l) at O2-end: the values varied between 3.0 and 8.2

Salinity:

No data

Nominal and measured concentrations:

The test vessel with 1000 mg/l direct weight resulted in a 3 h-EC36.
The 3 h-EC50 estimated by Probit analysis gave a value of 842 mg/l.

Details on test conditions:

TEST CONDITIONS:
- type of application: direct weighing
- test concentration of the activated sludge: 320 mg/l
- incubation time: 3 hours
- aeration: permanent
- temperature: 20 + 2 °C
- test concentration: 5 (320, 560, 1000, 1800, 3200 mg/l)
- test concentration (reference substance): 5 (2.5, 5, 10, 20, 40 mg/l)
- test parameter: respiration rate

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (purity 97 % )

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

842 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

299 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC25

Effect conc.:

489 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

other: EC90

Effect conc.:

2 370 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

The EC values are determined by statistical method (probit analysis).

Results with reference substance (positive control):

EC50: 13 mg/l (EC10 4.0 mg/l, EC90 39 mg/l)
The EC values are determined by statistical methods (probit analysis).

Validity criteria fulfilled:

yes

Remarks:

•respiratory rates of the 2 controls differ less than 15 % •respiratory rate of the controls < 60 mg O2 /L*h •EC50 of the reference substance 3.5-dichlorophenol is in the range 5 – 30 mg/L

Executive summary:

In a 3-h acute toxicity test, activated domestic sewage sludge were exposed to hexamethylenediisocyanate (HDI) at nominal concentrations of 320, 560, 1000, 1800, 3200 mg/L. 3, 5-dichlorophenol was used as reference material at 2.5, 5, 10, 20 and 40 mg/L (nominal concentration). The study was performed according to the OECD Guideline No 209. The 3h-EC50 value was determined at 842 mg/L (estimated by Probit analysis) (Bayer AG, 2000). This study is classified as acceptable and satisfies the guideline requirements for toxicity to microorganisms study with Activated Sludge.

Results synopsis

Activated sludge

Static conditions

3 -h EC50: 842 mg/L (estimated by Probit analysis)

Endpoint Effected: respiration

Description of key information

Concerning the acute toxicity of hexamethylene diisocyanate (HDI) to activated sludge

a study was conducted according to Directive 88/302/EEC Part C. The 3 h-EC50 estimated by Probit analysis gave a value of 842 mg/l (Bayer AG, 2000b).

Key value for chemical safety assessment

EC50 for microorganisms:

842 mg/L