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Long-term toxicity to aquatic invertebrates

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Reference
Endpoint:
long-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Results are based on nominal values, and test did not exacty follow existing guidance (1972-study), but followed test method well described and test conditions (e.g. test medium composition) were properly identified, and meets generally accepted scientific standards. NOEC is estimated value based on ECHA methodology (i.e., EC16/2).
Qualifier:
no guideline followed
Principles of method if other than guideline:
General test methods of this study are in line with existing guidelines (e.g., OECD 211 D magna reproduction) with regard to age and number of test organisms, exposure period, test conditions, volume of test beakers, renewal and endpoints (survival and reproduction)
GLP compliance:
not specified
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia magna
- Strain: laboratory clone
- Source: University of Michigan
- Age at study initiation (mean and range, SD): 12h +/- 12h
- Feeding during test: yes
- Type of food: 0.5 g of powdered dried grass and 10g of enriched trout-fry granules to 250 mL of Lake Superior water and mixed vigorously in a blender for 5 minutes. This suspension was strained through #20 bolting cloth. The blender was then rinsed with an additional 50 mL of lake water, and the rinse water was added to the suspension. This suspension was stored in a refrigerator and mixed thoroughly each time an aliquot was withdrawn.
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 wk
Hardness:
45.3 mg/L as CaCO3
Test temperature:
18 +/- 1 °C
pH:
7.74
Dissolved oxygen:
+/- 9 mg O2/L
Salinity:
not reported
Nominal and measured concentrations:
5-12 concentrations (not specified); a geometric series af concentrations was used for obtaining an approximation of toxicity; a linear series of concentrations was used for delineating reproductive impairment levels
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Type: open 250 mL beaker, but covered with a pane glass to minimize evaporation
- Fill volume: 200 mL
- Renewal rate of test solution (frequency/flow rate): weekly renewal of test medium
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Lake Superior water; unfiltered water strained through a #20 bolting cloth. Chemical characteristics of Lake Superior water were monitored during the testing period according to procedures outlined by the American Public Health Association and procedures employing atomic absorption spectroscopy.
- Metals: 14 µg Ba/L; 16 µg Sr/L; 0.78 µg Zn/L; <0.5 µg Ni/L; 1.51 µg Cu/L; <0.5 µg Co/L; < 0.01 g Hg/L; < 0.1 µg Cd/L
- Chloride: 1.22 mg/L
- Alkalinity: 42.3 mg/L as CaCO3
- Ca: 13.7 mg /L
- Mg: 3.12 mg/L
- K: 0.53 mg/L
- Na: 1.13 mg/L

OTHER TEST CONDITIONS
- Photoperiod: 16h light
- Light intensity: +/- 115 ft-c at the air-water interface

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
1) survival after 1, 2 3 weeks
2) reproduction (counting of the young produced each week)

Reference substance (positive control):
no
Duration:
3 wk
Dose descriptor:
other: EC16
Effect conc.:
5 800 µg/L
Nominal / measured:
nominal
Conc. based on:
element
Remarks:
as barium
Basis for effect:
reproduction
Details on results:
According to ECHA methodology, the EC16 (i.e., effects situated between 10 and 20%) can be used to estimate a NOEC-value; ECx (10% < x < 20%) /2 = NOEC. In this case, a NOEC of 2900 µg/L cas be derived.

Other 21d-effect levels that were reported, are the 21d-EC50 (reproduction) of 8900 µg/L and the 21d-LC50 of 13500 µg/L (12200-15000 µg/L). Endpoints are nor relevant for PNEC derivation, hence not included as K2-data points
Reported statistics and error estimates:
Results were statistically evaluated with the method of Litchfield and Wilcoxon (1949) for establishing approximations of the 95% confidence limits for survival. The terminology recommended by Sprague (1969) (i.e., LC), was used for survival and represents an interpolation from three or more partial-effect concentrations. reproductive effects were analyzed in a similar manner excluding confidence limits, but are given in terms of reproductive impairments by percentage.
Validity criteria fulfilled:
not specified
Conclusions:
The 21d-EC16 for Daphnia magna exposed to barium chloride dihydrate is reported as 5.8 mg Ba/L which corresponds to a NOEC value of 2.9 mg/L (i.e., EC16/2; ECHA-guidance).
Executive summary:

An chronic toxicity test with barium chloride dihydrate to Daphnia magna was realized according to non standardised method with no GLP statement. However the test method is well described and the test conditions were properly identified. This test is part of a serie of similar tests on daphnids performed in 1972 by Biesinger and Christensen. A full study was performed under semi-static conditions. The treatment and control groups had four replicates, each containing 5 daphnids and the test duration was 21 days. The results are based on nominal concentrations. The 21d-EC16 for Daphnia magna is reported as 5.8 mg Ba/L which corresponds to a NOEC value of 2.9 mg/L (i.e., EC16/2; ECHA-guidance).

Description of key information

Two reliable chronic toxicity studies were identified. the first study by Biesinger and Christensen reported a 21d-EC16 of 5.8 mg Ba/L (nominal values), which can be used for the estimation of a NOEC-value of 2.9 mg/L (i.e., EC16/2; ECHA-guidance).
The second data point was generated for the marine invertebrate Cancer anthonyi (Macdpnald et al, 1988). Here, a nominal, 7d-NOEC of 10 mg Ba/L was reported, and thids for the endpoint embryonal hatching.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
NOEC
Effect concentration:
2.9 mg/L

Marine water invertebrates

Marine water invertebrates
Dose descriptor:
NOEC
Effect concentration:
10 mg/L

Additional information

According to ECHA Guidance, a NOEC can be estimated by dividing a reliable ECX by 2, and this when X is situated between 10 and 20 % effect. The 21d-EC16 of 5.8 mg Ba/L for D. magna, as reported by Biesinger and Christensen (1972) is in compliance with this criterion. Therefore a NOEC of 2.9 mg Ba/L could be derived for the freshwater compartment.

For C. anthonyi, 24h-acclimated embryo's stripped from the pleopods of ovigerous females were used as test organisms. This type of life-stage is generally considered as the most sensitive one, and a 7 day exposure period combined with the endpoint under consideration (i.e., hatching/development) should therefore result in relevant chronic effects data.