Sodium dichromate

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Non-guideline study with deficiencies in the documentation, i.e. no information about light intensity/photoperiod and no details on the test substance. Besides, the hardness was not in the recommended range of the reference guideline OECD 203. The hatching success of one of the control replicates (2nd test, replicate A) was below the recommended value of the reference guideline OECD 210.

Qualifier:

according to guideline

Guideline:

other: Proposed Recommended Bioassay Procedure for Egg and Fry Stages of Freshwater Fish. U.S. Environmental Protection Agency 1972, National Water Quality Laboratory, Duluth, Minnesota

Version / remarks:

1972

Principles of method if other than guideline:

Embryo and larvae of rainbow trout (Oncorhynchus mykiss) were exposed for 60 days after hatch to sodium dichromate in soft water. The effects on survival, growth and hatchability were investigated.

GLP compliance:

not specified

Remarks:

not specified in study report

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Controls plus each concentration
- Sampling method: Unfiltered samples were collected in high-density polyethylene bottles which were cleaned prior to use.
- Sample storage conditions before analysis: Concentrated nitric acid was added to each water sample (1% per volume) and the sample was stored at room temperature for 2-3 weeks.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Dissolved in distilled water (obtained from a Corning AG-l all-glass still and passed through a Barnstead mixed-bed ion exchange cartridge)
- Controls: Yes, negative control

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Wareham, Massachusetts
- Age at study initiation: Eggs ≤1 day old
- Feeding during test: Yes
- Food type: Oregon moist trout starter
- Frequency: A minimum of four times daily

ACCLIMATION
- Acclimation period: Not stated

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

60 d

Hardness:

1st test: 34.0 ± 3.2 mg/L as CaCo3
2nd test: 3.4 ± 4.5 mg/L as CaCO3

Test temperature:

10 ± 1 °C

pH:

6.7-7.0

Dissolved oxygen:

9.5±0.9

Nominal and measured concentrations:

Measured
1st test: Control, 1.6, 3.2, 6.1, 12.2, 26.7, 49.7 mg/L
2nd test: Control, 0.051, 0.105, 0.194, 0.384, 0.822 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Test aquaria 35 x 30 x 30 cm (water depth of 20 cm) with growth chambers (25 x 30 x 12.5 cm). Egg incubation cups, made from 4-oz., 2-in. OD round glass jars with the bottoms cut off and replaced with nylon screen (40 mesh), were oscillated in the test water by a rocker arm at 2 rpm motor.
- Type: Eggs and fry were shielded from all sources of light by black polyethylene curtains.
- Type of flow-through (e.g. peristaltic or proportional diluter): Proportional diluters with a dilution factor of 0.5
- No. of organisms per concentration: 400 eggs (after hatch, 200 fry)
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: From a 400 ft. bedrock well
- Alkalinity: 31.5±2.8 mg/L as CaC03

VEHICLE CONTROL PERFORMED: No

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Mortality (Egg mortality and fish survival were recorded daily), growth (length was documented after 30 and 60 days, wet weight after 60 days), reproduction (hatching success)

Reference substance (positive control):

no

Dose descriptor:

NOEC

Effect conc.:

3.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Cr

Basis for effect:

number hatched

Remarks on result:

other: Test 1

Duration:

30 d

Dose descriptor:

NOEC

Effect conc.:

1.6 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Cr

Basis for effect:

mortality

Remarks on result:

other: Test 1

Duration:

60 d

Dose descriptor:

NOEC

Effect conc.:

0.384 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Cr

Basis for effect:

mortality

Remarks on result:

other: Test 2

Duration:

60 d

Dose descriptor:

NOEC

Effect conc.:

0.194 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Cr

Basis for effect:

length

Remarks on result:

other: Test 2

Key result

Duration:

60 d

Dose descriptor:

NOEC

Effect conc.:

0.051 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

element

Remarks:

Cr

Basis for effect:

weight

Remarks on result:

other: Test 2

Details on results:

- See Table 1 and 2

Reported statistics and error estimates:

Measured biological parameters from duplicate containers during continuous exposure were averaged and subjected to analysis of variance. When effects were observed, the means of these effects were subjected to Duncan's Multiple Range Test to determine, which treatments were statistically different from the controls.

Table 1 (1st test): Mean percentage hatch of eggs, mean survival, total lengths and wet weights of rainbow trout (Oncorhynchus mykiss) fry continuously exposed to chromium in soft water (34.0 ± 3.2 mg/L as CaCO3)

			1-30 days		31-60 days
Mean measured chromium conc. (mg/L)	Replicate	Mean hatch (%)	Survival (%)	Mean total length (mm)	Survival (%)	Mean total length (mm)	Mean total wet wt. (mg)
49.7	A	0	-	-	-	-	-
	B	0	-	-	-	-	-
26.7	A	0	-	-	-	-	-
	B	0	-	-	-	-	-
12.2	A	0	-	-	-	-	-
	B	31	0	-	-	-	-
6.1	A	56	7	20	0	-	-
	B	62	0	-	0	-	-
3.2	A	82	17	20	0	-	-
	B	85	4	19	0	-	-
1.6	A	77	84	21	14	21	250
	B	87	85	21	2	28	250
Control	A	76	96	26	96	34	480
	B	77	99	26	88	33	460

Table 2 (2nd test): Mean percentage hatch of eggs, mean survival, total lengths and wet weights of rainbow trout (Oncorhynchus mykiss) fry continuously exposed to chromium in soft water (33.4 ± 4.5 mg/L as CaCO3)

			1-30 days		31-60 days
Mean measured chromium conc. (µg/L)	Replicate	Mean hatch (%)	Survival (%)	Mean total length (mm)	Survival (%)	Mean total length (mm)	Mean total wet wt. (mg)
822	A	72	94	23	20	25	170
	B	70	95	23	22	25	170
384	A	68	96	26	78	32	270
	B	79	99	26	86	33	300
194	A	66	100	27	96	35	350
	B	68	97	28	96	37	380
105	A	70	100	27	88	37	400
	B	68	99	27	80	35	370
51	A	66	99	28	88	38	450
	B	72	98	26	86	37	440
Control	A	69	98	28	88	36	450
	B	76	91	26	92	38	550

Validity criteria fulfilled:

yes

Remarks:

only hatching success of one of the control replicates (2nd test, replicate A) was below the recommended value of the reference guideline OECD 210.

Conclusions:

Eggs and fry of Oncorhynchus mykiss were continuously exposed for 60 days after hatching to a series of concentrations of sodium dichromate (chromium) in soft water. From a first test conducted with concentrations of chromium up to 49.7 mg/L, a NOEC of 3.2 mg/L (measured) was determined for percentage hatch, while a NOEC of 1.6 mg/L (measured) was derived based on survival. In a second test with lower test concentrations (0.051-0.822 mg Cr/L), NOEC values of 0.384, 0.194 and 0.0051 were determined for survival, length and wet weight, respectively, after 60 days exposure.

Description of key information

One reliable study on the long-term toxicity to freshwater fish is available for sodium dichromate (Sauter et al. 1976). In an early life stage toxicity test with Oncorhynchus mykiss, the lowest NOEC of 0.051 mg Cr/L was derived for the wet weight of fish 60 days post-hatch. Effect concentrations derived in an additional long-term study of the toxicity of potassium dichromate to Pimephales promelas are higher and thus not consiered as key values.

The substance sodium dichromate consists of sodium cations and dichromate anions (Cr2O7-). Based on the solubility of sodium dichromate in water, a complete dissociation resulting in sodium cations and chromate anions may be assumed under environmental conditions. Therefore, the fate and toxicity of sodium dichromate in the environment is most accurately evaluated by assessing the fate and toxicity of its ecotoxicologically relevant moiety, i.e. the chromate anion, and read-across to data available for other (soluble) chromate substances is applied. Please refer to the respective endpoint summary for soluble chromium (VI) substances for further information.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

0.051 mg/L