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Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08/02/08-21/03/08
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP and conducted to current guideline, but read across to an analogous substance prevents use of highest reliability score. The read-across from MnCl2 to MnSO4 is justified on the following basis: both substances are very soluble in water hence bioavailable and both will release Mn2+ ions. Therefore, from an ecotoxicity standpoint, the chloride or sulphate anions are not considered to have any influence on the effective toxicity of Mn2+ or any toxicity in their own right, so the anions can be disregarded. Therefore any effect will be related to the Mn2+ cation, and the data from MnCl2 ecotoxicity tests is regarded as a suitable surrogate for read-across.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)
Principles of method if other than guideline:
This study was conducted according to the protocol, ''42- day Chronic Toxicity of Manganese to the freshwater amphipod crustacean, Hyalella aztecaThis protocol was designed to comply with methods described in the following references:
Environmental Canada(1997). Biological Test Methods: Test for Growth and Survival in Sediment Using the Freshwater Amphipod Hyalella azteca. Report EPS 1/RM/33.
U.S. Environmental Protection Agency(2000). Methods for measuring the toxicity and bioaccumulation of sediment associated contaminants with freshwater invertebrates. EPA 600/R-99/064,Duluth,MN.
GLP compliance:
yes (incl. certificate)
Remarks:
U.S. EPA GLP standard (40 CFR 792)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Analytical monitoring:
yes
Details on sampling:
- Concentrations: were determined at test initiation and then determined twice a week
- Sampling method: Analytical samples from each treatment were collected for total recoverable and dissolved Mn analysis at test initiation. For the remainder of the test, samples for dissolved Mn analysis were collected from alternating replicates within each treatment twice a week.
- Sample storage conditions before analysis: Samples were preserved with nitric acid ( trade metal grade) to pH < 2 prior to analysis.
Vehicle:
yes
Details on sediment and application:
PREPARATION OF SPIKED SEDIMENT
Artificially- formulated sediment was used as the sediment type in the toxicity test. Components and characteristics of the formulated sediments are provided in Table 1. Preparation instructions for the formulated sediments are detailed in OECD Guideline 218 (OECD 2004).
Test organisms (species):
Hyalella azteca
Details on test organisms:
TEST ORGANISM
- Common name: terrestrial amphipods
- Source: Aquatic Biosystems (Fort Collins, CO, USA)
- Age of parental stock (mean and range, SD): Arrived at the testing laboratory as 5 to 7 day old organisms
- Age of animals at beginning of exposure: 7-9 days old
- Feeding during test
The organism were held in-house for 2 days as per PERL standard operating procedure(SOP) # 5102, with appropriate feeding s and water nenwals to maintain health in the organisms prior to test initiation.


ACCLIMATION
- Acclimation period: 2 days
- Acclimation conditions (same as test or not):The organism were held in-house for 2 days as per PERL standard operating procedure (# 5102, with appropriate feeding and water renewals to maintain health in the organisms prior to test initiation.
- Health during acclimation (any mortality observed): Visual observation, the organism appeared healthy at test initiation.
Study type:
laboratory study
Test type:
flow-through
Water media type:
freshwater
Type of sediment:
artificial sediment
Duration:
42 d
Exposure phase:
total exposure duration
Post exposure observation period:
Not reported
Hardness:
104±5 mg/L as CaCO3
Test temperature:
23±2°c
pH:
7.3-8.1
Dissolved oxygen:
Dissolved oxygen concentration was maintained above 2.5 mg/L.
Salinity:
Not applicable
Ammonia:
<1.0 mg/L
Nominal and measured concentrations:
Nominal Concentration - 250, 500, 1000, 2000, 4000, and 8000 µg Mn/L
Average Measured Dissolved Mn Concentration - <62.5, 136.0, 285.9, 627.2, 1402.6, 3351.1, and 6663.6 µg/L
Details on test conditions:
TEST SYSTEM
- Test container (material, size): 1L glass jars with a mesh covered drainage hole.
- Sediment volume: Containers was filled with 100-mL of sterilised sand. A piece of nitex screen was placed in each chamber above the surface of the sand.
- Overlying water volume: The overlying volume of water in each chamber was approximately 500-600 mL.

EXPOSURE REGIME
- No. of organisms per container (treatment):10
- No. of replicates per treatment group:12
- No. of replicates per control / vehicle control:12
- Feeding regime: Daily. Flow to each test chamber was diverted for 2-3 hours to allow food to settle and become available to the organisms. If excess food or bacterial growth begins to form on the sediment surface, feeding may be suspended for one or more days.
- Type and preparation of food: Each chamber was fed YTC (Yeast, Trout Chow, Cereal Leaves).
- Amount of food: Each chamber was fed 1.0 mL of an 1800 mg/L stock.


RENEWAL OF OVERLYING WATER
- Details on volume additions: A Mariotte bottle was used to continuously deliver an appropriate volume of Mn stock solution to the diluter. A flow-splitting chamber was used for each test concentration( treatment) to promote mixing of the test solution and to allocate equally the test solution among the twelve replicate test chambers.
- Flow-rate: The stock solution was delivered to the dilutor at a rate of 5.0 mL/mixture. The flow rate to each test chamber was approximately 10 mL/min providing approximately 24 volume exchanges per replicate per day.


OVERLYING WATER CHARACTERISTCS
- Type of water : The dilution and control water used for this study was laboratory-blended water ( well water blended with reverse osmosis-treated water with a targeted hardness of 80- 120 mg/L as CaCO3).
- Alkalinity:129±5 mg/L as CaCO3
- Conductivity: 339±22 µS/cm
- Total organic carbon:<0.50 mg/L (DOC)
- Unionized ammonia:<1.0 mg/L
- Residual chlorine:37.3 mg/L


CHARACTERIZATION OF ARTIFICIAL SEDIMENT
Components and Characteristics of the formulated sediment are provided in Table 1. Preparation instruction for the formulated sediment is as per OECD guideline 218 (OECD 2004).


OTHER TEST CONDITIONS
- Photoperiod: 16- hours and 8-hours dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Observations of live and dead organisms was recorded daily from test initiation until termination. Dead organism was recorded and immediately removed. At test day 28 organisms from four of the replicates was used for survival and growth measurements. The surviving organisms from the remaining eight replicates were replaced into water only chambers (without sand) and returned to the flow- through exposure system. On day 35, offspring was counted and removed from each chamber. Endpoint measured include survival (Day 28, 35, and 42), growth (as dry weight on Day 28 and 42), and reproduction (number of young/ femaleproduced from day 28 to Day 42). For dry weight measurement, organisms from each chamber was placed into a pre-weighed aluminium pan and dried for at least 12 hours at 105°C to determine dry weight

VEHICLE CONTROL PERFORMED: Yes


TEST CONCENTRATIONS
- Spacing factor for test concentrations: Six test treatments was tested using a 0.5 dilution scheme.
- Range finding study
- Test concentrations: 320 µg Mn/L
- Results used to determine the conditions for the definitive study: These concentration were selected based on findings from a previous chronic life-cycle H. azteca Mn test where concentration up to 320 µg Mn/L resulted in no effect on exposed organism.
Reference substance (positive control):
no
Duration:
42 d
Dose descriptor:
NOEC
Effect conc.:
285.9 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival
Duration:
42 d
Dose descriptor:
LOEC
Effect conc.:
627.2 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival
Duration:
42 d
Dose descriptor:
EC10
Effect conc.:
188.5 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival
Remarks on result:
other: 95% CL
Duration:
28 d
Dose descriptor:
EC10
Effect conc.:
96.4 µg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
growth rate
Remarks on result:
other: 95% CL
Details on results:
Not reported
Results with reference substance (positive control):
Not reported
Reported statistics and error estimates:
All statistical analyses were performed using the mean dissolved Mn concentrations. Differences in survival (at Days 28, 35, and 42), growth (at day 28 and 42), and reproduction (at day 35 and 42) were evaluated using a statistical computer package (comprehensive Environmental Toxicity Information System [CETIS], McKinleyville, CA, USA, and Toxicity Relationship Analysis Program [TRAP], Duluth, MN, USA). If the data met the assumptions of normality and homogeneity, the NOEC and LOEC were estimated using an analysis of variance to compare (p≤0.05) organism performance in the experimental treatments with that observed in the control. The effective concentration required to reduce the survival, growth, or reproduction by 10% relative to control performance (EC10 and EC20) were estimated using a piecewise linear regression analysis. The median-lethal concentration (LC50) was also estimated using a piecewise linear regression analysis. Exposure concentration were log-transformed before determination of EC10 and EC20 and LC50 values.

 

 

 

 

 

 Table 6. Survival Data1

 

Average Measured Dissolved Mn (mg/L)

% Survival (±SD)

Day 28

Dat 35

Day 42

<62.5

91±10

81±15

51±32

136.0

83±22

60±38

56±30

285.9

91±11

79±27

48±42

627.2

72±24*

48±26*

13±15*

1402.6

58±35*

37±34*

20±23*

3351.1

23±23*

8±11*

0±0*

6663.6

0±0*

-

-

1Survival is reported as the average survival within a treatment (combination of all replicates within a treatment).

* Significant less than control (p≤0.05).

 SD = Standard Deviation

 Table 7. Organism Growth Data (Biomass)1

 

Average Measured Dissolved Mn Concentration (µg/L)

Average Dry weight per original organism in mg (±SD)

Day 28

Day 42

<62.5

0.18±0.01

0.08±0.07

136.0

0.19±0.01

0.15±0.09

285.9

0.12±0.04

0.12±0.08

627.2

0.10±0.05*

0.04±0.04

1402.6

0.16±0.052,*

0.07±0.03

3351.1

0.03±0.01*

-

6663.6

-

-

1Biomass (average dry weight per original organism) is reported as a combination of all replicates within a treatment

2Day 28 average includes ‘outliers’ replicate.

*Significantly less than control (p≤0.05).

SD = Standard Deviation.

 

Table 8. Organism Growth Data1

 

Average Measured Dissolved Mn Concentration (µg/L)

Average Dry weight per original organism in mg (±SD)

Day 28

Day 42

<62.5

0.22±0.03

0.15±0.05

136.0

0.20±0.01

0.21±0.08

285.9

0.14±0.05*

0.18±0.03

627.2

**

**

1402.6

**

**

3351.1

**

**

6663.6

**

**

1Dry weight is reported as the average weight per organism (combination of all replicates within a treatment).

*Significantly less than control (p≤0.05).

** Data was not used in statistical analysis (hypothesis testing) because a survival effect was observed at this concentration.

SD = Standard Deviation.

 

Table 8. Organism Reproduction Data1

 

Average Measured Dissolved Mn Concentration (µg/L)

Average Reproduction (±SD) (young/female)

Day 35

Day 42

<62.5

0.75±1.1

1.55±2.57

136.0

0.12±0.24*

0.12±0.24

285.9

0.0±0.0*

0.28±0.45

627.2

**

**

1402.6

**

**

3351.1

**

**

6663.6

**

**

1 Reproduction is reported as the average number of young per female (combination of all replicates within a treatment)

*Significantly less than control (p≤0.05).

** Data was not used in statistical analysis (hypothesis testing) because a survival effect was observed at this concentration.

SD = Standard Deviation

 

Table 10. Summary of Survival Statistics (µg Mn/L)1

 

Endpoint

Survival

28 day

35 day

42 day

NOEC

285.9

285.9

285.9

LOEC

627.2

627.2

627.2

EC10 (95% Cl)

568.6 (349.9-923.9)

382.8(104.7-1399.5)

188.47(27.47-1293.2)

EC20 (95% Cl)

752.6(494.0-1146.4)

512.6(170.1-1544.3)

255.9(51.9-1260.5)

1NOEC = No Observed Effect Concentration. LOEC = Lowest Observed Effect Concentration. EC10= Effective Concentration for 10% reduction in survival relative to control performance. EC20 = Effective Concentration for 20% reduction in survival relative to control performance. CI – Confidence interval.

 

Table 11. Summary of Growth Statistically (µg Mn/L)1

 

Endpoint

Mean Dry Biomass

Dry Weight

28 day2

42 day

28 day

42 day

NOEC

285.9

1402.6

136.0

285.9

LOEC

627.2

>1402.6

285.9

>285.9

EC10( 95% CI) all replicates

1349.8

(138.2-13184.3)

N/A

1720.5 9N/A)

N/A

EC10( 95% CI)

Without outlier replicate

1063.1

(549.0-2058.5)

N/A

96.4(12.9-720.7)

N/A

EC20(95% CI)

all replicates

1610.2(256.0-10126.5)

N/A

1949.0(N/A)

N/A

EC20(95% CI)

Without outlier replicate

1248.6(706.4-2206.9)

N/A

203.4(39.5-1046.9)

N/A

1NOEC = No Observed Effect Concentration. LOEC = Lowest Observed Effect Concentration. EC10= Effective Concentration for 10% reduction in survival relative to control performance. EC20 = Effective Concentration for 20% reduction in growth relative to control performance. CI– Confidence interval. N/A = Non-applicable/determinable.

Validity criteria fulfilled:
yes
Remarks:
Control survival was greater than 80% at the end of the test
Conclusions:
The lowest NOEC (survival) was 0.29 mg Mn/L. The read-across from MnCl2 to MnSO4 is justified on the following basis: both substances are very soluble in water hence bioavailable and both will release Mn2+ ions. Therefore, from an ecotoxicity standpoint, the chloride or sulphate anions are not considered to have any influence on the effective toxicity of Mn2+ or any toxicity in their own right, so the anions can be disregarded. Therefore any effect will be related to the Mn2+ cation, and the data from MnCl2 ecotoxicity tests is regarded as a suitable surrogate for read-across.
Endpoint:
sediment toxicity: long-term
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
17/10/08 - 10/12/08
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP and conducted to current guideline. The read-across from MnCl2 to MnSO4 is justified on the following basis: both substances are very soluble in water hence bioavailable and both will release Mn2+ ions. Therefore, from an ecotoxicity standpoint, the chloride or sulphate anions are not considered to have any influence on the effective toxicity of Mn2+ or any toxicity in their own right, so the anions can be disregarded. Therefore any effect will be related to the Mn2+ cation, and the data from MnCl2 ecotoxicity tests is regarded as a suitable surrogate for read-across.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 218 (Sediment-Water Chironomid Toxicity Test Using Spiked Sediment)
Principles of method if other than guideline:
This study was conducted according to the protocol, ''Life-Cycle Toxicity of Manganese to the Midege, Chironomus tentans)''
This protocol was designed to comply with methods described in the following references:
Environment Canada(1997), Biological Test Methods: Test for Growth and Survival in Sediment Using the Larvae of Freshwater Midges (Chironomus tentans or Chironomus riparius). Report EPS 1/RM/32.
American Society for Testing and Materials(1999). Standard test methods for measuring the toxicity of sediment-associated contaminants with freshwater invertebrates.E1706-95b. In Annual Book of ASTM Standards, Philadelphia, PA.
U.S. Environmental Protection Agency(2000). Methods for measuring the toxicity and bioaccumulation of sediment-associated contaminants with freshwater invertebrates. EPA 600/R-99/064, Duluth, MN
GLP compliance:
yes (incl. certificate)
Remarks:
U.S. EPA GLP standard (40 CFR 792)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Analytical monitoring:
yes
Details on sampling:
- Concentrations: determined for each treatment at test initiation, then at Tuesday and Friday and then finally at test termination
- Sampling interval: Analytical samples from each treatment were collected for total recoverable and dissolved Mn analysis at test initiation. For the remainder of the test, samples for dissolved Mn were collected from alternating replicates in each treatment on Tuesday and Friday and at test termination. Dissolved Mn is defined as Mn recovered from samples passed through a 0.45µm filter prior to preservation.
- Sample storage before analysis: Preserved with nitric acid (trace metal grade) to pH < 2 prior to analysis.


Details on sediment and application:
PREPARATION OF SPIKED SEDIMENT
Preparation instruction for the formulated sediment are detailed in OECD guideline 219 (OECD 2004).

Test organisms (species):
Chironomus dilutus (previous name: Chironomus tentans)
Details on test organisms:
TEST ORGANISM
- Source: Egg masses were obtained from Aquatic Biosystems (Fort Collins, CO, USA) on 15 October ( for test initiation) and 21 October 2008 (for auxiliary chamber initiation)
- Handling of egg masses and larvae: Upon arrival at the testing laboratory and prior to test initiation, the egg masses were held in water identical to that which would be used for testing.
- Age of animals at beginning of exposure: Newly-hatched (<24 hours old) chironomids


Study type:
laboratory study
Test type:
flow-through
Water media type:
freshwater
Type of sediment:
artificial sediment
Duration:
54 d
Exposure phase:
total exposure duration
Post exposure observation period:
Not reported
Hardness:
89±20 mg/L as CaCO3
Test temperature:
23 ± 2°c
pH:
7.3-8.0
Dissolved oxygen:
Dissolved oxygen concentrations will be maintained above 2.5 mg/L
Salinity:
Not applicable
Ammonia:
<1.0 mg/L
Nominal and measured concentrations:
2.5, 5, 10, 20, 40 and 80 mg Mn/L - Nominal concentrations
0.01, 2.40, 4.66, 9.14, 18.12, 35.41 and 71.20 mg/L - Average measured dissolved concentrations
Details on test conditions:
TEST SYSTEM
- Test container (material, size):1L glass jars with a mesh covered drainage hole
- Sediment volume:50 mL of formulated sediment
- Overlying water volume:Approximately 500- 600 mL of overlying water
- Aeration:no


EXPOSURE REGIME
- No. of organisms per container (treatment):15 organism was partitioned into each test chamber
- No. of replicates per treatment group: 12 replicates for each treatment. Four extra replicates per concentration was used for auxiliary males with a total of 420 organism. These four extra replicates was seeded with organisms two days after the initiation of the other twelve replicates. These auxiliary chambers are necessary because males begin emerging ~ 2 days earlier than females.
- No. of replicates per control / vehicle control: 12 replicates for control (i.e non-exposed organism)
- Feeding regime: Each chamber was fed a Tetramin slurry once daily.
- Type and preparation of food:The Tetramin slurry was prepared by pulverising 1.6g of Tetramin flakes with 400 mL dilution water to create a slurry
- Amount of food:Each chamber was fed 1.5 to 2.5 mL (based upon day of test) of a 4.0 mg/mL stock

RENEWAL OF OVERLYING WATER
- Details on volume additions: The exposure system consisted of a continuous-flow proportional diluter gravity fed by a Marriotte bottle containing the toxicant stock. Mixtures of toxicant and dilution water will be delivered to exposure chambers (1L glass jars) via polyethylene tubing. Control (without manganese) and treatment solutions was continuously ( with the exception of feeding time) delivered to exposure chambers for the duration of the test.
- Flow-rate:Nominal flow to exposure chambers was approximately 10 ml/mixture (~ 15 L/day)

OVERLYING WATER CHARACTERISTCS
- Type of water :Dilution water was obtained from on-site well and blended with laboratory water that has undergone reverse osmosis treatment to achieve a target alkalinity and pH
- Alkalinity:80-120 mg/L as CaCO3
- Conductivity:292±27 µS/ cm
- Particulate matter:
- Total organic carbon:<0.50 mg/ L (Dissolved organic carbon)
- Unionized ammonia:<1.0 mg/L
- Residual chlorine:<0.05 mg/L

CHARACTERIZATION OF ARTIFICIAL SEDIMENT
- % dry weight of sphagnum moss peat: 4-5 %
- Particle size distribution
- % sand: Grain size: > 50% of the particles should be in the range of 50-200µ
- % silt: particles size ≤ 1mm
- Composition (if artificial substrate): Kaolinite clay - Kaolinite content 30%
- Method of preparation (if artificial substrate): Preparation instruction for the formulated sediment are detailed in OECD 219 (OECD 2004)
- Total organic carbon (%) - 2(±0.5) % of sediment dry weight
- Other: Calcium carbonate - 0.05-0.1 % of sediment dry weight, Water(Conductivity ≤ 10µS/ cm) -30-50 % of sediment dry weight

OTHER TEST CONDITIONS
- Photoperiod: 16-Hours light and 8-hours dark
- Light intensity: illumination of 500 to 100 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Observation of live and dead organisms was recorded daily from test initiation until termination. Dead organisms were recorded and immediately removed. Organisms were monitored for emergence (complete and partial), pupal and adult mortality, time to death (adults), reproduction, and egg hatchability.
Emergent traps were placed on top of each test chambers on day 10. This is when monitoring for emergence began. As emergence occurred, adults were transferred to a corresponding oviposition/ reproduction chamber. The chamber contained at least a 1:1 female to male ratio. If needed, organisms within the same concentration. but from different replicates, were combined to ensure the opportunity of mating. The number of eggs produced was estimated either by the ring or indirect count method. The males from the auxiliary chambers was used to support reproduction where no males were present in the primary chambers. The auxiliary chambers was not monitored for mortality nor was the females used for reproduction or in endpoint analysis.

VEHICLE CONTROL PERFORMED: no


TEST CONCENTRATIONS
- Spacing factor for test concentrations: Six test treatments was tested using a 0.5 dilution scheme
- Range finding study
- Test concentrations: The concentrations were selected based on findings from a previous acute C. riparius Mn test with concentrations of up to 20 mg Mn/L that had no effect on exposed organism.
Reference substance (positive control):
no
Duration:
54 d
Dose descriptor:
NOEC
Effect conc.:
18.12 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival, emergence and reproduction
Duration:
54 d
Dose descriptor:
LOEC
Effect conc.:
35.41 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival and emergence
Duration:
54 d
Dose descriptor:
EC10
Effect conc.:
16.34 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival
Remarks on result:
other: 95% CL
Duration:
54 d
Dose descriptor:
other: EC20
Effect conc.:
17.83 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
other: Survival
Remarks on result:
other: 95% CL
Duration:
54 d
Dose descriptor:
EC10
Effect conc.:
16.44 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
emergence rate
Remarks on result:
other: 95% CL
Duration:
54 d
Dose descriptor:
other: EC20
Effect conc.:
17.93 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
dissolved
Basis for effect:
emergence rate
Remarks on result:
other: 95% CL
Details on results:
- Mortality of test animals at end of exposure period: See table 5 (Remarks on results including tables and figures)
- No. of offspring produced: See table 6(Remarks on results including tables and figures)
- No. of emerged male and female midges (per vessel and per day):See table 5 (Remarks on results including tables and figures)
- No. of pupae failing to emerge (per vessel and per day):See table 5(Remarks on results including tables and figures)
- Percent emergence per replicate and test concentration:See table 5(Remarks on results including tables and figures)
- Mean development rate of fully emerged midges (per replicate and treatment rate; male and female midges pooled):See table 6 (Remarks on results including tables and figures)
Results with reference substance (positive control):
Not reported
Reported statistics and error estimates:
All statistical analyses were performed using the mean dissolved Mn concentration and were performed using statistical computer packages (Comprehensive Environmental Toxicity Information System [CETIS], McKinleyville, CA, USA and Toxicity Relationship Analysis Program [TRAP], Duluth, MN, USA). The CETIS statistical program follows a decision tree for analysis of survival, emergence and reproduction data(USEPA 2000). If the data met the assumptions of normality and homogeneity, the NOEC and LOEC were estimated using an analysis of variance (Bonferroni Adjusted t, Steel Many-One Rank or Wilcoxon/Bonferroni) to compare (p=0.05) organism performance in the experimental treatments with that observed in the control. The EC10 and EC20 values were estimated using a piecewise linear regression. Exposure concentrations were log- transformed before determination of EC10 and EC20 values.

 

 

  

 

 

  

Table 5. Survival and Emergence Data

 

Average Measured Dissolved Concentration (mg/L)

% Survival (±SD)1

% Emerged (±SD)2

0.01

67(12)

68(11)

2.40

76(16)

77(14)

4.66

60(26)

60(260

9.14

70(17)

71(17)

18.12

53(11)

54(10)

35.41

1(2)

1(2)

71.20

0(0)

0(0)

1Survival is reported as the average survival within a treatment ( combination of all replicates within a treatment), excluding the auxiliary replicates.

2Average emergence within the treatment (combination of all replicates within a treatment), excluding auxiliary replicates. 

SD =Standard Deviation

 Table 6. Organism Reproduction Data1

 

Average Measured Dissolved Concentration (mg/L)

Average Number of eggs/case (±SD)

Average % Hatched (±SD)

0.01

1691.7(344.0)

91.7(6.5)

2.40

1493.8(220.4)

92.9(5.5)

4.66

1676.3(279.8)

95.0(4.5)

9.14

1346.4(201.2)

92.6(7.3)

18.12

1718.3(309.7)

90.4(7.3)

35.41

N/A

N/A

71.20

N/A

N/A

 1Average within a treatment, excluding auxiliary replicates

SD = Standard Deviation, N/A= Not applicable, due to no emergence in treatment

 

Table 7. Summary of test statistics (mg/L dissolved Mn)1

 

 

 

 

Reproduction

Endpoint

Survival

Emergence

# eggs/case

% Hatched

NOEC

18.12

18.12

18.12

18.12

LOEC

35.41

35.41

>18.12

>18.12

EC10(95% CI)

16.34

16.44

-

-

EC20(95% CI)

17.83

17.93

-

-

1NOEC = No Observed Effect Concentration. LOEC =Lowest Observed Effect concentration. EC 10/20= Effective Concentration for 10/20% reduction in survival or emergence relative to control performance. CI= Confidence Intervals.

Validity criteria fulfilled:
yes
Remarks:
The average adult emergence in the control treatment was 68%. All treatment groups that had reproductive data averaged over 1300 eggs/case and averaged over 90% hatchability.
Conclusions:
There was no significant effect on midge reproduction. The 54d NOEC was 18.12 mg Mn/L. The read-across from MnCl2 to MnSO4 is justified on the following basis: both substances are very soluble in water hence bioavailable and both will release Mn2+ ions. Therefore, from an ecotoxicity standpoint, the chloride or sulphate anions are not considered to have any influence on the effective toxicity of Mn2+ or any toxicity in their own right, so the anions can be disregarded. Therefore any effect will be related to the Mn2+ cation, and the data from MnCl2 ecotoxicity tests is regarded as a suitable surrogate for read-across.

Description of key information

Chronic endpoints are available for two sediment dwelling organisms, Hyalella Azteca and Chironomus tentans, representing different living and feeding conditions. The lowest of these endpoints is a NOEC of 0.29 mg Mn/L, which is equivalent to 0.22 mg Mn/kg wwt sediment (assuming density of sediment of 1.3 g/cm3) and 0.57 mg Mn/kg dwt sediment (based on a conversion factor of 2.6).

It should be noted that these values are considerably lower than the background concentration of manganese in European environments (452 mg/kg in sediment; “Probabilistic Distribution of Manganese in European Surface Water, Sediment and Soil and Derivation of Predicted Environmental Concentrations (PEC)”, Parametrix, 2009 and supported by GEMAS data).

Key value for chemical safety assessment

EC10, LC10 or NOEC for freshwater sediment:
0.57 mg/kg sediment dw

Additional information