mancozeb (ISO); manganese ethylenebis(dithiocarbamate) (polymeric) complex with zinc salt  

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:

from 1999-10-19 to 2000-02-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1984

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

- For the preliminary test, 1.836 g of Dithane M-45 were diluted to 300 mL tap water to give a stock concentration of 6.12 g Dithane M-45/L (5.0 g a.i./L).
- For the definitive test, 0.612 g of Dithane M-45 were diluted to 100 mL tap water to give a stock concentration of 6.12 g Dithane M-45/L (5.0 g a.i./L).
- The test suspensions were prepared as follows: 16 mL of synthetic sewage feed
together with appropriate amounts of test item stock solution were made up to 300 mL with tap water. This suspension was poured into the test vessel, followed by addition of 200 mL of microbial inoculum.
- In the preliminary test, the addition of 10 ~L, 100 ~L, 1 mL, 10 mL, and 100 mL of test item stock solution resulted in final concentrations of 0.1, 1, 10, 100, and 1000 mg a.i./L, respectively.
- In the definitive test, the addition of 313 ~L, 625 ~L, 1.25 mL, 2.5 mL, 5 mL, and 10 mL of test item stock solution resulted in final nominal concentrations of 3.13, 6.25, 12.5, 25, 50, and 100 mg a.i./L, respectively.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Activated sludge from a domestic sewage treatment plant (Wastewater Treatment Plant from the town of Romanshorn, Switzerland)
- Preparation of inoculum for exposure: The sludge was centrifuged at 1500 rpm for 10 minutes, supernatant was decanted. This procedure was repeated until the centrifuge tubes were filled 3/4 with concentrated sludge.
- Initial biomass concentration: suspended solid concentration of 4.02 g/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 ± 0.5 °C

pH:

7.60 - 7.7.1

Nominal and measured concentrations:

Nominal concentrations: control, 3.13, 6.25, 12.5, 25, 50, and 100 mg a.i. test item/L
No measured concentrations.

Details on test conditions:

TEST SYSTEM
- Test vessel: BOD bottles
- Material, size, headspace, fill volume: glass, 1000 mL
- Aeration: yes, aerated at 0.5 to 1 L/min using ambient air
- No. of vessels per control (replicates): 2
- Sludge concentration (weight of dry solids per volume): 4.02 g/L

OTHER TEST CONDITIONS
- Adjustment of pH: none

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol at 5, 15, and 30 mg a.i. reference item/L

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

13 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

47 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

25 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

The inhibition of respiration by the reference item, 3,5-dichlorophenol, when compared to the mean control respiration rate was 5, 65, and 90 % for 5, 15, and 30 mg a.i./L (nominal), respectively. The calculated EC50 for the reference item was 13 mg a.i./L, which was within the acceptable limits (5 - 30 mg a.i./L) as specified in OECD Guideline # 209.

Preliminary Test
In the preliminary test, the respiration after a 3-hour contact time was inhibited by -9, -24, 4, 88 and 88 % at nominal concentrations of 0.1, 1, 10, 100, and 1000 mg a.i. Dithane M-45/L, respectively. Based on these results, the definitive test was performed at nominal concentrations of 3.13, 6.25, 12.5, 25, 50, and 100 mg a.i./L. The concentrations chosen for the reference item were based on the test acceptability criteria (GECD Guideline # 209), and these were 5, 15, and 30 mg a.i./L.

Definitive Test
The temperature in the environmental chamber where the test system was located ranged from 19.5 to 20.5 °C during the test. Respiration rates for the two control vessels were comparable (within 7 % of each other).
Inhibition of respiration by the test item was -5, 7, 36, 31, 92, and 93 % for 3.13, 6.25, 12.5, 25, 50 and 100 mg a.i./L (nominal), respectively. The corresponding calculated EC50 of Dithane® M-45 was 25 mg a.i./L (95 % confidence interval 7 to 102 mg a.i./L).

Validity criteria fulfilled:

yes

Conclusions:

Inhibition of respiration by the test item was -5, 7, 36, 31, 92, and 93 % for 3.13, 6.25, 12.5, 25, 50, and 100 mg a.i./L (nominal), respectively. The calculated
EC50 of Dithane M-45 was 25 mg a.i./L (95% confidence interval 7 to 102 mg a.i./L).

Executive summary:

In a study performed according to OECD 209 (1984), the effect of Dithane M-45, at nominal concentrations of 3.13, 6.25, 12.5, 25, 50, and 100 mg a.i.IL, on sewage sludge microorganisms by measuring the respiration rate under defined conditions was determined. The use of a reference item, 3,5-dichlorophenol, allowed for an evaluation of the sensitivity of the microbial population and the adequacy of the test procedures. For the reference item 3,5-dichlorophenol the calculated EC50 was 13 mg reference item/L, which was within the acceptable limits (5 - 30 mg a.s./L) as specified in the OECD guideline 209.
The calculated EC50 of Dithane M-45 was 25 mg a.s./L (95 % confidence interval 7 to 102 mg a.s./L). The EC20 was 0.924 mg a.s./L (95 % confidence interval 3 to 47 mg a.s./L, and the EC80 was 47 mg a.s./L (95 % confidence interval 13-236 mg a.s./L).
Temperature conditions during the test did not stray from the acceptable range (20 ± 2 °C). The concentration of suspended solids in the activated sludge suspension used in this test was within the acceptable range (4 ± 0.4 g/L). This study satisfied the validity criteria for this kind of study. The respiration rates of the two controls was were within 7 % of each other (below the maximum acceptable if 15 %), and the EC50 of the reference was 13 mg a.s./L (within the acceptable limits of 5 - 30 mg/L). Concluded endpoints can therefore be acceptable as being reliable.

Description of key information

The calculated EC50 of Dithane M-45 was 25 mg a.s./L (95 % confidence interval 7 to 102 mg a.s./L). The EC20 was 0.924 mg a.s./L (95 % confidence interval 3 to 47 mg a.s./L, and the EC80 was 47 mg a.s./L (95 % confidence interval 13 - 236 mg a.s./L).

Key value for chemical safety assessment

EC50 for microorganisms:

25 mg/L

Additional information

The summary below is taken from the RAR Dossier, Volume 3 - B.9, (March 2019) of Mancozeb:

In a study performed according to OECD 209 (1984), the effect of Dithane M-45, at nominal concentrations of 3.13, 6.25, 12.5, 25, 50, and 100 mg a.i.IL, on sewage sludge microorganisms by measuring the respiration rate under defined conditions was determined. The use of a reference item, 3,5-dichlorophenol, allowed for an evaluation of the sensitivity of the microbial population and the adequacy of the test procedures. For the reference item 3,5-dichlorophenol the calculated EC50 was 13 mg reference item/L, which was within the acceptable limits (5 - 30 mg a.s./L) as specified in the OECD guideline 209.
The calculated EC50 of Dithane M-45 was 25 mg a.s./L (95 % confidence interval 7 to 102 mg a.s./L). The EC20 was 0.924 mg a.s./L (95 % confidence interval 3 to 47 mg a.s./L, and the EC80 was 47 mg a.s./L (95 % confidence interval 13 - 236 mg a.s./L).
Temperature conditions during the test did not stray from the acceptable range (20 ± 2 °C). The concentration of suspended solids in the activated sludge suspension used in this test was within the acceptable range (4 ± 0.4 g/L). This study satisfied the validity criteria for this kind of study. The respiration rates of the two controls was were within 7 % of each other (below the maximum acceptable if 15 %), and the EC50 of the reference was 13 mg a.s./L (within the acceptable limits of 5 - 30 mg/L). Concluded endpoints can therefore be acceptable as being reliable.