Isonicotinaldehyde

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 March - 16 April 2003

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP - guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Report date:

2003

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes

Remarks:

with the exception that the test substance was not analysed for purity and that the incubation mixtures were not analysed for concentration of the test substance

Test material

Test material information

Constituent 1

Reference substance name:

Isonicotinaldehyde

EC Number:

212-832-3

EC Name:

Isonicotinaldehyde

Cas Number:

872-85-5

Molecular formula:

C6H5NO

IUPAC Name:

pyridine-4-carbaldehyde

Test material form:

other: liquid

Details on test material:

- Name of test material (as cited in study report) : Pyridine-4-aldehyde
- Physical state : clear yellowish liquid
- Analytical purity : 98,7% (GC)
- Lot/batch No. : 1120126/001
- Expiration date of the lot/batch : not stated
- Storage condition of test material : Refrigerator at approx. 4°C , in the dark , under nitrogen

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge :
Activated sludge was collected from a sewage treatment works A-2500 Baden , which wastewater catchment is predominantly domestic .
- Pretreatment :
On arrival in the laboratory , the sample was aerated by means of a filtered compressed air before being used for the study .
The suspended solids concentration was determined by filtering a 5 ml sample trough a pre-dried and pre-weighed glass filter (Whatman GF/C) . The filter with solid were dried at 105°C and re-weighed and the sludge solids determined by difference .
The inoculum was not acclimatised or adapted to "Pyridine-4-aldehyde" before exposure to the test substance in this study .

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

15 mg/L

Based on:

other: organic carbon

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium : see at "Any other information on materials and methods incl. tables"
- Test temperature : 21,3 +/- 0,4°C
- pH adjusted: no
- Suspended solids concentration : 30 mg/l
- Continuous darkness : yes
- Preparation of the test substance : Based on the molecular formula of the test substance , its carbon content is 67,28% by weight . The test substance was weighed and added directly to two vessels and the toxicity control . Weights of 0,0670 g , 0,0668 g and 0,0678 g were added to 3 litre of medium to give a nominal concentration of 15 mg carbon/l . This concentration corresponds to a theoretical CO2 (ThCO2) concentration of 165 mg/3l .
- Procedure : 2400 ml mineral medium were added to each of 5-litre flask . The test substance was suspended in the medium which was free of CO2 by purging with CO2 free air , at a concentration of nominally 15 mg organic carbon per litre . The reference substance was added for positive control and toxicity control . Each vessel was inoculated with micro-organisms derived from a sample of activated sludge and was filled up to a total volume of 3000 ml .

TEST SYSTEM
- Culturing apparatus : 5-litre flasks
- Number of vessels/concentration : 2
- Method used to create aerobic conditions : The air flow was regulated for each vessel individually . Air flow was determined volumetrically in intervals . Adjustments were made as necessary to maintain a flow rate in the range 50 to 100 ml/min. The air used was CO2-free "control air" (Linde Gase , A-2492 Eggendorf) . As an added precaution , a 0,0125 M barium hydroxide solution was used as CO2 absorber .
- Details of trap for CO2 : 3 absorption bottles connected in line each containing 100 ml of 0,0125 M barium hydroxide solution

SAMPLING
- Sampling frequency : after 1,2,4,6,8,10,15,20,25 and 28 days
- Sampling method : 3 absorption bottles were connected in line each containing 100 ml of 0,0125 M barium hydroxide solution . On the days of CO2-measurement , the barium hydroxide absorbers closest to the test vessels were disconnected and the barium hydroxide solution was titrated with 0,05 M HCl using phenolphthalein as the indicator . The remaining absorbers were connected to the incubation vessels and a new absorber containing 100 ml fresh 0,0125 M barium hydroxide was placed at the far end of the series . In case a substantial precipitation was seen in the first trap , also the second bottle was analysed .
- Sample storage before analysis : The samples were analysed on the day of sampling

CONTROL AND BLANK SYSTEM
- Inoculum blank : yes
- Toxicity control : yes (reference substance + test substance)

Reference substance

Reference substance:

benzoic acid, sodium salt

Remarks:

(3,43 mg/l)

Results and discussion

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

87

Sampling time:

28 d

Details on results:

The biodegradation of "Pyridine-4-aldehyde" was 81% and 92% with a mean of 87% after 28 days . The 10% level was reached on approx. Day 5 . 60% degradation was exceeded on approximately Day 26 .
See table 1 at "Any other information on results incl. tables"

BOD5 / COD results

Results with reference substance:

Positive control :
The plateau of biodegradation was reached on about Day 10 and the degradation of the positive control substance sodium benzoate exceeded the pass level on Day 5 .

Toxicity control :
Degradation in the toxicity control , which contained sodium benzoate and the test substance , was indicative of a slight inhibition of the microbial activity by the test substance . The final biodegradation was about 75% .

Any other information on results incl. tables

Table 1 : Biodegradation as percentage of the theoretical CO₂ yield

Elapsed time	test substance			positive control	toxicity control
Days	A 3	A 4	mean	PK 5	TK 6
1	2,1	2,7	2,4	5,8	2,1
2	5,3	7,0	6,2	23,4	5,0
4	7,9	11,3	9,6	48,8	18,1
6	10,3	14,3	12,3	66,8	27,5
8	12,3	17,4	14,9	75,7	33,4
10	14,9	20,1	17,5	83,5	36,9
15	17,6	23,6	20,6	89,8	43,2
20	25,5	32,3	28,9	91,1	55,0
25	44,3	53,5	48,9	92,0	65,3
28	81,3	92,3	86,8	91,8	75,3

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The plateau of biodegradation was reached on about Day 10 and the degradation of the positive control substance sodium benzoate exceeded the pass level of 60% on Day 5

Interpretation of results:

other: not readily but rapidly biodegradable

Conclusions:

The study was conducted under GLP compliance and a well documented study report is available.
The pass level for "ready biodegradability" is 60% evolution of CO2 . The pass level has to be reached within a 10-d window , that begins when the biodegradation has reached 10% and that must end before Day 28 of the test . In this study the 10-d window started at about Day 5 and ended at Day 15 . At this time the biodegradation of the test substance was only about 21% . Therefore pyridine-4-aldehyde is not readily biodegradable although an extensive biodegradation , reaching 87% at Day 28 was obtained .

Executive summary:

The biodegradability of the substance pyridine-4-aldehyde was investigated according to OECD guideline 301B and EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test). The study was conducted in compliance with the Principles of Good Laboratory Practice (GLP). A mixed population of activated sewage sludge micro-organisms collected from a sewage treatment works A-2500 Baden, which treats predominantly domestic sewage was used as inoculum. For the purpose of the definitive study the test material was dispersed directly in culture medium. It was used in a concentration of 15 mg carbon/L for the study. Sodium benzoate (C6H5COONa) was used as reference substance. The test material plus the reference substance in inoculated culture medium act as toxicity control. The study was conducted under aerobic conditions in a temperature controlled room at 21 °C, in darkness. The plateau of biodegradation of the positive control substance sodium benzoate was reached on about Day 10 and the degradation exceeded the pass level of 60 % on Day 5. The degradation in the toxicity control, which contained sodium benzoate and the test substance, was indicative of a slight inhibition of the microbial activity by the test substance. The final biodegradation was about 75 %.

The pass level for "ready biodegradability" is 60 % evolution of CO2. The pass level has to be reached within a 10 -d window, that begins when the biodegradation has reached 10 % and that must end before Day 28 of the test.

In this study the 10 -d window started at about Day 5 and ended at Day 15. At this time the biodegradation of the test substance was only about 21 %. Therefore pyridine-4 -aldehyde is not readily biodegradable although an extensive biodegradation, reaching 87 % at Day 28 was obtained.