Desmedipham

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991-09-19 to 1991-10-31

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

not specified

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

other: Sewage Plant Secondary effluent (domestic sewage) & Soil

Details on inoculum:

- Source of inoculum/activated sludge: A composite inoculum was used for the test. Secondary effluent from the sewage plant at Frankfurt/M-Niederrad dealing with predominantly domestic sewage. 100 g of a mixture of five different soil samples of the Battelle-area at Frankfurt/M were suspended in 1 L tap water and stirred for 30 minutes by means of a magnetic stirrer.

- Preparation of inoculum for exposure: The inoculum was aerated by means of a magnetic stirrer until use on the same day of preparation.

- Type and size of filter used, if any: Sewage was filtered through a coarse paper filter the first 200 mL being discarded. The soil particles were allowed to settle, and the supernatant was filtered through a coarse paper filter the first 200 mL being discarded.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: The test substance was dissolved in an inorganic medium (mineral nutrient solution).
- Test temperature: The test solution was kept in closed bottles in the dark at a constant temperature of 20°C ± 1°C.
- Temperature of the dilution water after aeration: 21.6°C
- Aeration of dilution water: Yes, Ultrapure Water (Millipore, Milli Q) was used for the test. Prior to application the water was slightly aerated with O2 (Messer Griesheim) by means of a sintered glass tube until an O2 content of 8.13 mg O2 per litre was reached. After the aeration the water was mixed by means of a magnetic stirrer for a 5 min. period. Then the water was ready for use.

TEST SYSTEM
- Measuring equipment: O2 determinations were performed using O2 electrode (WTW; FRG; Model OXI 530 with electrode Model TriOxmatic EO 200).
- Other: Special calibrated bottles for O2 determination were used for the test (ORI NS 19, volume about 290 mL). 11.6 mg of the test substance were weighed into a 100 mL calibrated measuring flask. 100 mL of ethylacetate were transferred into the flask with the test material. The flask was closed, and the test material was dissolved completely. 5 mL of this dilution were transferred into the test bottles and the solvent was evaporated. By this method the test substance was distributed in a very thin layer covering the glass surface of the bottles. After the solvent had been evaporated the bottles were filled with the mineral nutrient solution and immediately closed with special stoppers. Prior to use the mineral nutrient solution was inoculated with one drop of mixed inoculum by means of a pointed pipette per litre of final volume. The final concentration of the test material was about 2 mg/L. The volumes of the bottles were documented, and the final results were corrected according to the final concentration, respectively.
A predetermined amount of the test substance was dissolved in an inorganic medium (mineral nutrient solution), providing a concentration of ~ 2.0 mg active substance per litre (AS/L). A control with inoculum, but without any test material was run in parallel for determination of oxygen blanks. For checking the inoculum one reference substance (Na-Benzoate) was run in parallel. For checking toxicity of the test material one control series of bottles with the test substance plus the Na-Benzoate control were run in parallel. In the case of toxicity the oxygen consumption in that series should have been lower than in the Na-Benzoate control.

SAMPLING
- Sampling method: The degradation was followed by oxygen analysis over a 28-day period. A control with inoculum, but without any test material was run in parallel for determination of oxygen blanks.
- Sample storage before analysis: Closed bottles in the dark.

CONTROL AND BLANK SYSTEM
- Inoculum blank: For checking the inoculum one reference substance (Na-Benzoate) was run in parallel. For checking toxicity of the test material one control series of bottles with the test substance plus the Na-Benzoate control were run in parallel. In the case of toxicity the oxygen consumption in that series should have been lower than in the Na-Benzoate control.
- Toxicity control: For checking toxicity of the test material one control series of bottles with the test substance (~2mg/L as described above) plus the Na-Benzoate control (3mg/L as described above) were run in parallel. In the case of toxicity the oxygen consumption in that series was lower than in the Na-Benzoate control. This toxicity was expressed as a percentage of oxygen consumption compared with the non-affected Na-Benzoate control. All transfer and filling operations of the air saturated water were conducted bubble-free by siphon.

Reference substance:

benzoic acid, sodium salt

Remarks:

Na-Benzoate

Key result

Parameter:

% degradation (O2 consumption)

Remarks:

On basis of the COD and BOD.

Value:

21

Sampling time:

28 d

Details on results:

Under the chosen conditions 21 % of the test substance was degraded within 28 d of test period calculated on basis of the COD and BOD. The test is valid because the wanted test conditions were met: the control substance was degraded to > 60% within 10 days after biodegradation had started, and the O2 depletion values of the controls with and without inoculation were within the required range.

The toxicity towards bacteria was measured to be 6.2 % at t5d, 1.3 % at t15d and 3.3 % at t28d.

Results with reference substance:

The control substance was degraded to > 60% within 10 days after biodegradation had started.

Table 1: Results of the CLOSED BOTTLE TEST: 02 Determinations

Culture Medium	mg O2/L at
	to		t5d		t15d		t28d
	Anal.	Mean	Anal.	Mean	Anal.	Mean	Anal.	Mean
Mineral nutrient solution without test material and without in- oculation (Blank without inoculation) mo	7.92	7.92	7.67	7.66	7.50	7.46	7.51	7.47
			7.60		7.44		7.46
			7.71		7.45		7.40
							7.50
Mineral nutrient solution without test material but with inoculum (Blank with inoculation) mbx	7.93	7.93	7.73	7.69	7.55	7.55	7.46 7.55 7.51 7.57	7.52
			7.61		7.54
			7.73		7.55
Mineral nutrient solution with the control substance and with inoculum	7.89	7.89	4.74	4.76	4.07	4.10	4.05 3.81 3.98 3.49 3.82	3.83
			4.74		4.13
			4.79		4.11
mtx	mgO2/L	mean	mg O2/L	vol.	mg O2/L	vol.	mg O2/L	vol.
Mineral nutrient solution with test material and with inoculum	7.91	7.91	(0.06)* (4.14)* 7.25 6.92	292.70 295.50 291.90 295.60	6.45 6.51 (3.70)*	293.1 293.2 292.1	6.51 6.57 6.43 6.51	293.5 292.2 291.5 291.4
mtx + Na-Benz.	mgO2/L	mean	mg O2/L	vol.	mg O2/L	vol.	mg O2/L	vol.
Mineral nutrient solution with test material and with inoculum	7.94	7.94	4.58 4.51 4.28	308.50 301.60 293.40	2.89 3.10 3.13	291.6 291.4 293.3	0.09 2.93 2.88 2.83 3.15	289.7 291.2 295.4 291.1 291.4

 

*       outlier acc. to Nalimov at the 95% probability level

 

Table 2: 02 Depletions (mg BOD/L after x days)

	mg BOD/L after x d	mg BOD/L after x d	mg BOD/L after x d
Test substance	5 d	15 d	28 d
Desmedipham	0.695	1.14	1.063
Reference: Na-Benzoate	2.93	3.45	3.69

 

Table 3: Biodegradability of Desmedipham according to O₂ Depletions (BOD_X, see table 2) and TOD (Control Substance) or COD (Test Substance)

	Biodegrability (%) after x days	Biodegrability (%) after x days	Biodegrability (%) after x days
Test substance	5 d	15 d	28 d
Desmedipham	13.9	22.8	21.2
Reference: Na-Benzoate	58.7	69.1	73.9

Validity criteria fulfilled:

yes

Remarks:

The control substance was degraded to > 60% within 10 days after biodegradation had started, and the O2 depletion values of the controls with and without inoculation were within the required range.

Interpretation of results:

not readily biodegradable

Conclusions:

Desmedipham has relative poor water solubility resulting in a poor bioavailability. Toxicity towards bacteria may be regarded negligible as the inhibition effect was in the range of 6.2 % at t5d to 1.3 % at t15d.

Executive summary:

Desmedipham was tested for biodegradability according to Closed-Bottle-Test (OECD 301 D). Under the chosen conditions 21 % of the test substance was degraded within 28 d of test period calculated on basis of the COD (Chemical Oxygen Demand). Within the test series for checking toxitity towards bacteria an inhibition of oxygen consumption of 6.2 % was found at t_5d. This inhibition was reduced to 1.3 % at t_15d and 3.3 % at t_28d. 

Description of key information

In the OECD 301D test, 21% of desmedipham was degraded during 28 days in test solution inoculated with mixture of sewage plant effluent and five soils. Desmedipham is considered not to be readily biodegradable.

 

In the table below all available studies are listed. For some studies only the results are presented since they are not considered relevant due to the reasons given under “Assessment”. All available studies have been evaluated within the scope of Plant Protection Regulation in the respective Draft Renewal Assessment Report (DAR) under Regulation (EC) 1107/2009.

Test type	Result	Assessment	Reference
Closed bottle test OECD 301D	Desmedipham was not considered to be readily biodegradable (21% degradation observed).	Key study	Lebertz (1991)
Inherent biodegradability test (OECD 302C)	45% was degraded after 28 days	Supporting study	Wuethrich (1990)
Modified MITI test	No result	Invalid as technical material was applied at higher concentration than the solubility of desmedipham	Ritter (1989)
Not carried out to any OECD test guidelines	No result	Invalid as not performed to appropriate guidelines and only for 5 days	Wuethrich (1993)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater