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Sediment toxicity

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Reference
Endpoint:
sediment toxicity: long-term
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
16 July 2001- 28 November 2001
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
GLP - Guideline study, tested with the source substance zinc(bis) dimethyldithiocarbamate (CAS No. 137-30-4). In accordance to the ECHA guidance document “Practical guide 6: How to report read-across and categories (March 2010)”, the reliability was changed from RL1 to RL2 to reflect the fact that this study was conducted on an read-across substance
Qualifier:
according to guideline
Guideline:
OECD Guideline 219 (Sediment-Water Chironomid Toxicity Test Using Spiked Water)
Qualifier:
according to guideline
Guideline:
other: Proposal for a BBA-Guideline (1995)
GLP compliance:
yes (incl. QA statement)
Remarks:
The Swiss GLP Monitoring Authorities
Details on sampling:
Water, pore water and sediment samples from the test systems were taken from the middle and highest test concentrations of 320 and 2000 µg/L ziram 76 WG on day 0 (approximately one hour after the test item application), on day 7 and at the test termination on day 27.
On day 27 analytical samples were taken out of the first test beaker from the biological test. The analytical samples from day 0 and 7 were taken from test beakers prepared exclusively for analytical measurements in parallel to the biological test (two test beakers were prepared for each sampled test concentration, and one for the control). One of the two treated test beakers and the control beaker were sampled approximately one hour after test item application. The other treated replicates were incubated under the conditions of the test until sampling on day 7. To these additional replicates test organisms were inserted and food was added as in the biological part of the study.
Vehicle:
no
Test organisms (species):
Chironomus riparius
Details on test organisms:
- Strain: Chironomus riparius, first larval stage
- Source: Novartis Crop Protection AG, CH-4002 Basel, Switzerland
- Age (at start of the study): At the date when the test animals were placed into the test beakers, the larvae were 2-3 days old.
- Breeding method: Only fresh egg masses were used as source for the test animals.
- Kind of food: Tetra Min® fish food (supplied by TETRA-Werke, D-49304 Melle, Germany) was used as food for the larvae during the test.
- Amount of food: The following amounts of dry Tetra Min® were fed per vessel and day:
On Days 0/3 (5 – 0.58 mL/vessel ≈ 29 mg Tetra Min®/vessel
On Days 7/10/12/14/17/19/21/24/26: 1.2 mL/vessel ≈ 60 mg Tetra Min®/vessel
- Feeding frequency: The fish food flakes were finely ground and suspended in test water. Food was added at least three times per week until Day 26, when all of the larvae had emerged (see above).
- Pretreatment: Six days before application of the test item into the test beakers some fresh egg masses were taken from the test organism culture and deposited into small vessels in test water with a small amount of food (mixture of fresh green algae Scenedesmus subspicatus from a laboratory culture and a Tetra Min® fish food suspension).
Feeding of animals during test: Yes
Study type:
laboratory study
Test type:
static
Water media type:
freshwater
Type of sediment:
artificial sediment
Limit test:
no
Duration:
27 d
Exposure phase:
total exposure duration
Test temperature:
19.8 - 21.4°C
pH:
8.0 to 8.4
Dissolved oxygen:
6.6 – 8.8 mg O2/L
Nominal and measured concentrations:
Nominal: 51, 128, 320, 800 and 2000 µg/L ziram 76 WG (corresponding to 38.6, 96.7, 242, 605 and 1512 µg/L ziram). The analytically measured concentrations of ziram in the application solution samples ranged from 93 to 98 % of the nominal values (with the exception of one sample resulting in a mean value of 126 %).
Details on test conditions:
Artificial sediment prepared on the basis of dry weights as follows (according to the test guidelines):
Sphagnum peat: 4 %
(air dried, very finely ground to ≤ 1 mm)
Kaolin clay (kaolinite content > 30 %): 20 %
Sand* (Sihelco 36): 76 %
Size distribution:
0.25 mm 1.0 %
0.18 mm 6.0 %
0.125 mm 80.0 %
0.09 mm 12.0 %
<0.09 mm 1.0 %
Calcium carbonate (CaCO3): 0.3 %
Each beaker contained approx. 3 cm high layer of sediment (670 g wet weight with 46% water content, or about 459 g dry weight, respectively); approx. 1.6 L water was poured into the beakers (overlying water).
Reference substance (positive control):
no
Duration:
27 d
Dose descriptor:
EC50
Effect conc.:
721 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
act. ingr.
Basis for effect:
emergence rate
Duration:
27 d
Dose descriptor:
NOEC
Effect conc.:
242 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
act. ingr.
Basis for effect:
emergence rate

Emergence ratio (male and female midges pooled)

Nominal initial concentration of ziram 76 WG [µg/L]

control

51

128

320

800

2000

Σ(inserted larvae/treat.)

100

100

100

100

100

100

Σ(emerges midges/treat.)

97

91

92

97

70

0

% emerged midges/treat. (mean)

97

91

92

97

70

0

Emergence ratio ERarc: mean

1.449

1.321

1.296

1.420

0.992

0.000

SD

0.1452

0.2120

0.0993

0.1007

0.0566

0.000

Min

1.284

1.059

1.159

1.369

0.927

0.000

Max

1.571

1.571

1.369

1.571

1.059

0.000

n

4

4

4

4

4

4

% of control

100

91

89

98

68

0

STAT

-

n.s.

n.s.

n.s.

s.

s.

Development rate over (male and female midges pooled)

Development rate/ treat. (day-1)

Male and female midges pooled

Nominal initial concentration of ziram 76 WG [µg/L]

control

51

128

320

800

2000

Mean

0.067

0.069

0.066

0.064

0.056

n.a.

SD

0.0016

0.0022

0.0008

0.0005

0.0013

n.a.

min

0.066

0.067

0.065

0.064

0.055

n.a.

max

0.069

0.072

0.067

0.065

0.057

n.a.

n

4

4

4

4

4

n.a.

%of control

100

103

99

96

84

n.a.

STAT

-

n.s.

n.s.

s.

s.

n.a.

ERarc:                   arcsin-transformed emergence r

STAT:              results of a Williams-test (a= 0.05, one-sided smaller)
n.s.:
                   mean ERarcnot significantly lower than in the solvent control
s.:
                      mean ERarcsignificantly lower than in the solvent control
n.a.:
                    not applicable (no midges emerged)

Validity criteria fulfilled:
yes
Conclusions:
The test showed no major deviations from the guideline and the study can be regarded as valid.
Executive summary:

Materials and methods: Toxic effects of ziram 76 WG (a formulation of the active ingredient ziram) on the development of sediment-dwelling larvae of the midgeChironomus ripariusin water-sediment systems were investigated following the proposal for a BBA-Guideline: “Effects of plant protection products on the development of sediment-dwelling larvae ofChironomus ripariusin a water-sediment system” (1995) and the proposal for a new OECD guideline 219, draft document: “Chironomid Toxicity Test using spiked water” (2001).

First-instar larvae ofChironomus ripariuswere exposed to nominal concentrations of 51, 128, 320, 800 and 2000 µg/L ziram 76 WG (corresponding to 38.6, 96.7, 242, 605 and 1512 µg/L ziram) for a period of 27 days, sufficient to assess the impact on full maturation of the larvae to adult midges. A control (water-sediment systems without test item application) was run in parallel.

The test parameters were the development time/rate of the midges and the emergence ratio as the number of fully emerged male and female midges.

Results and discussion: The analytically measured concentrations of ziram in the application solution samples ranged from 93 to 98 % of the nominal values (with the exception of one sample which resulted in a mean value of 126 %). The measured concentrations confirmed the correct preparation of the application solutions. The mean measured concentrations of ziram in the water columns one hour after the test item application corresponded to 107 – 115 % of the nominal concentrations. The concentrations of ziram decreased fast in the water of the water-sediment systems. Seven days after the application only 7-8 % of the nominal test concentrations were still found. At study termination after 27 days the concentrations of ziram in the water columns corresponded to 1-6 % of the nominal values.

In the pore water the concentrations of ziram on days 0, 7 or 27 were always very low (in maximum 4 % of the nominal concentrations).

Up to and including the test concentration of nominal initial 320 µg/L ziram 76 WG the mean emergence ratio of pooled sexes were not significantly lower than in the control. At the test concentration of nominal initial 800 µg/L ziram 76 WG the mean emergence ratio was statistically significantly reduced compared to the control. At the highest test concentration of 2000 µg/L ziram 76 WG no midges emerged.

The mean development rate of fully emerged midges (pooled sexes) in the control was 0.067 day-1 (and thus fulfilled the validity criterion of the test guidelines requesting a development rate between 0.05 and 0.10 day-1).

The mean development rates of the females were not significantly lower than in the control up to and including the test concentration of nominal initial 320 µg/L ziram 76 WG. At the concentration of nominal initial 800 µg/L ziram 76 WG the mean development rate of females was significantly reduced compared to the control.

The mean development rate of the males was statistically significantly reduced already at the test concentration of 320 µg/L ziram 76 WG. However, the mean development rate at this concentration still amounted to 93 % of the control value. The reduction of 7 % at this test concentration is within the normal range of biological variability in this study type. Although of statistically significance, probably biologically not relevant. This result was therefore not taken into account at the assessment of the NOEC and LOEC of this study.

Thus, the 27-day NOEC of ziram 76 WG (highest test concentration without toxic effects) for Chironomus riparius in this water–sediment study was determined to be 320 µg/L ziram 76 WG (= 242 µg/L ziram). The 27-day EC50for the emergence ratio was 954 µg/L ziram 76 WG (= 721 µg/L ziram) with 95 % confidence limits from 845 to 1077 µg/L ziram 76 WG (= 639 – 814 µg/L ziram).

The 27-day EC50for the development rate was >800 µg/L ziram 76 WG. This value could not be calculated since at the next higher test concentration of 2000 µg/L ziram 76 WG no midges emerged.

Description of key information

NOEC (27 d) = 242 µg a.i./L (Chironomus riparius)

Key value for chemical safety assessment

Additional information

No studies on the toxicity of disulfiram (CAS No. 97 -77-8) to sediment organisms are available. Therefore, a conclusion based on an analogue approach had to be drawn. Zinc(bis) dimethyldithiocarbamate (137-30-4) which is structurally and composition related to tetraethylthiuram disulfide, was tested in a study with Chironomus riparius as test organism (Memmert, 2001). This study was conducted according to OECD Guideline No. 219: Sediment-Water Chironomid Toxicity Test using Spiked Water (2004) and a proposal for BBA-Guideline: Effects of plant production products on the development of sediment dwelling larvae of Chironomus riparius in a water-sediment system (1995), under GLP conditions. After 27 days of exposure to the compound, significant effects were found at the two highest concentrations tested on emergence rate and development. No effects on emergence rate or development were observed up to (and including) a concentration of 320 µg/L Ziram 76 WG (242 µg a.i./L Zinc(bis) dimethyldithiocarbamate), the NOEC for the study.

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