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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1997-01-23 to 1997-02-10
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: EC Guideline: 88/302/EC (30.5.1988)
GLP compliance:
yes
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Activated sludge from Marl-West (Lippeverband) sewage treatment plant. Suspended solids: 2.75 g/l activated sludge
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
At the beginning of incubation 18 - 19.5 °C

During the determination of oxygen content 19.2 - 20 °C
Nominal and measured concentrations:
Nominal concentrations: 180, 240, 300, 360, 420 mg/L
Details on test conditions:
Test substance, synthetic sewage (16 mL), inoculum (200 mL). Total volume 500 ml.
Reference substance (positive control):
yes
Remarks:
3, 5, Dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
400 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
197 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration

Table 1 % inhibition

Substance ID / Conc.

Time period of O2 measurement (minutes)

Start value mg O2/L

End value mg O2/L

Mg O2/L*h

% Inhibition

pH before O2 Measurement

CPMDCS

480 mg/L

7.5

8.21

7.17

8.32

69.2

6.3

CPMDCS 360 mg/L

7

6.92

5.1

15.6

42.2

7

CPMDCS 300 mg/L

8

7.21

4.43

20.85

22.8

7.3

CPMDCS 240 mg/L

8

6.91

3.9

22.58

16.4

7.4

CPMDCS 180 mg/L

7

7.01

4.14

24.6

8.9

7.7

DCP 5 mg/L

8

7.87

5.89

14.85

45

8.5

DCP 15 mg/L

7.5

8.41

7.29

8.96

66.8

8.5

DCP 30 mg/L

7.5

8.72

8.03

5.52

79.6

8.5

Control RC1

6.5

7.67

4.83

26.22

8.4

Control RC2

6.5

7.63

4.62

27.78

8.3

Sum RC1+ RC2

54

 

Validity criteria fulfilled:
yes
Conclusions:
An activated sludge respiration inhibition 3hr EC50 value of 400 mg/L and EC10 value of 197 mg/L were determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Toxicity to microorganisms: Activated sludge respiration inhibition 3 hour EC50 value of 400 mg/L and EC10 value of 197 mg/L (EC Guideline: 88/302/EC), read-across from an analogous substance.

Key value for chemical safety assessment

EC50 for microorganisms:
400 mg/L
EC10 or NOEC for microorganisms:
197 mg/L

Additional information

There are no microorganism toxicity data available for 3-chloropropyl(dimethoxy)methylsilane, therefore good quality data for the analogous substance dichloro(3-chloropropyl)methylsilane (CAS 7787-93-1), have been read across. The submission substance, 3-chloropropyl(dimethoxy)methylsilane, hydrolyses rapidly in contact with water to form 3-chloropropyl(methyl)silanediol and methanol. The read-across substance, dichloro(3-chloropropyl)methylsilane hydrolyses very rapidly in contact with water to form 3-chloropropyl(methyl)silanediol and hydrochloric acid. Both substances hydrolyse rapidly and share the same silanol hydrolysis product; 3-chloropropyl(methyl)silanediol. In view of the rapid hydrolysis of the registered substance, it is the silanol hydrolysis product that is relevant for environmental risk assessment.

Methanol does not have adverse effects on microorganisms (OECD 2004).

Hydrochloric acid is not expected to have adverse effects on microorganisms in a sewage treatment plant, where the pH is maintained within a favourable range.

3-Chloropropyl(dimethoxy)methylsilane and dichloro(3-chloropropyl)methylsilane are within an analogue group of substances within which, in general there is no evidence of significant toxicity to microorganisms.

This group consists of substances containing a number of different functional groups but specific read across is between substances with similar functionality.

The table below presents microorganism toxicity data for substances relevant to 3-chloropropyl(dimethoxy)methylsilane (CAS 18171-19-2).

It is therefore considered valid to read-across the results for dichloro(3-chloropropyl)methylsilane (CAS 7787-93-1) to fill the data gap for the registered substance since the source and target substances generate the same silanol hydrolysis product. Additional information is given in a supporting report (PFA 2013j) attached in Section 13.

Table: Microorganism toxicity data for relevant substances

CAS

Name

Result: E(I)C50 (mg/L)

Result: NOEC (or EC10/ EC20) (mg/L)

Guideline Number

Test method

Species

Duration

Reliability

7787-93-1

Dichloro(3-chloropropyl)methylsilane

400

 

88/302/EC

ASRI

 

3 hours

1

2530-87-2

3-chloropropyl(trimethoxy)silane

 

EC10 1.1 ml/L
Note: WS predicted 14000

Huls method

oxygen consumption

P. putida

5 hours

2

5089-70-3

3-chloropropyl(triethoxy)silane

 

EC10 >2 ml/L

Huls method

oxygen consumption

P putida

5 hours

2

15267-95-5

3-chloromethyl(triethoxy)silane

>1000

≥1000

OECD 209

ASRI

 

3 hours

1

 

A 3-hour EC50 value and NOEC value of 400 mg/L and 197 mg/L respectively, have been determined for the effects of dichloro(3-chloropropyl)methylsilane (CAS 7787-93-1) on the inhibition of respiration of wastewater treatment plant bacteria based on nominal concentrations of the substance (Werner 1997).

References:

OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1

PFA (2013j). Peter Fisk Associates, STP Microorganism toxicity Main Analogue Group report, PFA.300.003.006