Reaction products of sodium glucoheptonate with zinc sulfate and sodium hydroxide

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2004

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

not specified

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

Samples of natural surface waters were taken at eight locations, five in The Netherlands, two in Belgium, and one in France. Samples for toxicity assays with different organisms were taken on various occasions. Two sampling techniques were used. The first technique consisted of taking a 50-L sample of natural water in acid-washed (0.14 N HNO3) polyethylene vessels. Upon arrival in the laboratory, the sample was filtered (0.45 mm; Gelman Science, Ann Arbor, MI, USA) and stored at 4°C in the dark until use. This technique was used for all toxicity tests with D. magna and for two tests with P. subcapitata. The second technique consisted of concentrating in situ approximately 1,000 L of water to a volume of approximately 20 L using reverse osmosis. This technique was used for all tests with rainbow trout and six tests with P. subcapitata. The technique was considered the most practical in order to obtain the large quantities of water needed for the chronic tests with rainbow trout. Upon arrival in the laboratory, the sample was stored at 4°C in darkness. In order to use the sample for testing, the concentrated sample was diluted with deionized water to obtain the DOC concentration originally present in the natural surface water. As Ca and Mg were replaced with Na during the reverse osmosis process, the Ca and Mg concentrations of the diluted sample were readjusted to obtain the Ca and Mg levels measured in the original water sample using reagent-grade CaCl2 or MgCl2. We have previously demonstrated that this method yields very similar water chemistry in the reconstituted water as compared with the original water. Furthermore, tests with diluted reverse-osmosis concentrates and original water have been demonstrated to yield identical copper and zinc toxicity to D. magna and P. subcapitata.

Vehicle:

no

Details on test solutions:

Surface waters were spiked with different Zn concentrations and, before testing, the spiked samples were allowed to equilibrate for 2 d to obtain near-equilibrium zinc speciation. For all tests with P. subcapitata (except Markermeer), for most chronic tests with D. magna (except Markermeer, Rhine, and Voyon), and for the rainbow trout test with Bihain water, 750 mg/L 3-N-morpholinopropanesulfonic acid was added as a pH buffer. Zinc and copper toxicity have been demonstrated not to be affected by the presence of 3-N-morpholinopropanesulfonic acid.

Test organisms (species):

Daphnia magna

Details on test organisms:

Daphnia magna <24 h old were used as test organism. Feeding with 8, 16, and 24 x 10E6 cells/d of Pseudokircheneriella subcapitata and Chlamydomonas reinhardtii in a 3:1 mixture (on a cell-number basis) was provided in 1st, 2nd, and 3rd weeks of the test, respectively.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Test temperature:

20°C

pH:

6.0 - 8.4

Details on test conditions:

TEST SYSTEM
- Test vessel: 50-ml polyethylene vessels
- fill volume: 50-ml
- Aeration: no
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: 6 natural water and 1 synthetic water samples
- Dissolved organic carbon: 0.3 - 17.3 mg/L
- Chlorine: 15 - 318 mg/L
- Alkalinity: 6.9 - 165 mg CaCO3/L
- Intervals of water quality measurement: start of test, pH daily

OTHER TEST CONDITIONS
- Adjustment of pH: N-morpholinopropanesulfonic acid was added as a pH buffer
- Photoperiod: 12:12 (light:dark)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
21-d NOEC, 21-d EC10, 21-d EC50

VEHICLE CONTROL PERFORMED: no

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

LC50

Remarks:

pH 6.8, DOC 17.3 mg/L, Ca 38.3 mg/L

Effect conc.:

536 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

LC50

Remarks:

pH 7.3, DOC 2.53 mg/L, Ca 5 mg/L

Effect conc.:

112 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Remarks:

pH 6.0, DOC 5.37 mg/L, Ca 3.7 mg/L

Effect conc.:

62.6 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Remarks:

pH 6.8, DOC 17.3 mg/L, Ca 38.3 mg/L

Effect conc.:

491 µg/L

Nominal / measured:

meas. (initial)

Conc. based on:

element (dissolved fraction)

Basis for effect:

reproduction

Details on results:

A large variation of physico-chemical characteristics important for zinc bioavailability was observed in the tested waters, i.e., dissolved organic carbon (DOC) concnetration between 2.48 and 22.9 mg/L, pH between 5.7 and 8.4, Ca between 1.51 and 80.2 mg/L, Mg between 0.79 and 18.4 mg/L, and Na between 3.8 and 116 mg/L. For D. magna, the variation in chronic toxicity was up to a factor of 7, as indicated by 21-d EC10s (between 59.2 and 387 mg Zn/L) and 21-d EC50s (between 112 and 536 mg Zn/L).

DOC

The percentage of Zn calculated to be bound to DOC in natural waters varied between 5 and 89%. A general pattern is that, at lower Zn concentrations, more Zn tends to be complexed to DOC.

Alkalinity

ZnCO3 accounted in some cases for more than 10% of the dissolved zinc, notably in those test waters with the highest levels of alkalinity and pH.

Table 5.Physico-chemistry and effect concentrations of zinc(µg/L as dissolved) obtained for the toxicityassays in natural waterwithDaphnia magna(numbersbetween parentheses are 95%confidence limits)^a
Water	pH	DOC^b(mg/L)	Ca(mg L)	Mg(mg L)	Na(mg L)	K(mg L)	SO4(mg L)	Cl(mg L)	Alkalinity^c	21-d NOEC	21-d EC10	21-d EC50	% Zn-DOC^d
Synthetic	7.2	0.3^e	80.2	12.2	17.7	3.0	48.0	73.8	33.2	155	196(150-256)	299 (249-358)	2-3
Ankeveen	6.8	17.3	38.3	6.5	17.4	6.1	127	50.0	12.3	491	387 (319-460)	536 (497-579)	35-56
Bihain	6.0	5.37	3.7	1.1	6.2	0.9	4.0	15.0	6.9	62.6	NC^f	NC	42-50
Brisy	7.3	2.53	5.0	3.4	8.8	2.1	9.5	23.0	13.6	94.5	92.7 (81.3-105)	112 (84-151)	30-50
Markermeer	8.0	7.49	52.7	14.0	87.3	8.7	109	318	127	244	171 (129-227)	313 (273-359)	15-60
Regge	8.0	9.87	60.1	8.0	52.9	10.4	63.0	144	165	251	265 (171-413)	473 (399-561)	NP-69
Rhine	8.2	2.30	61.0	10.7	55.4	5.0	57.0	215	159	143	126 (92-175)	242 (209-279)	5-33
Voyon	8.4	4.17	37.1	7.1	10.0	1.3	20.0	21	125	72.7	59.2 (30.1-116)	171 (130-226)	15-68
^a NOEC =^no-observed-effect concentration; EC10 and EC50 are the 10 and 50% effective concentrations, respectively. ^b DOC =^dissolved organic carbon. ^c Alkalinity as mg CaCO3/L. ^d The range of dissolved Zn present as complexed to DOC, calculated using the^Biotic Ligand Model software at the 48-h EC50and the 21-d EC10assumingthe averageactive fulvic acid of 61%. ^e Approximate background DOC concentration in deionized water used for preparing this synthetic test water. ^f NC =^could not be calculated due to insufficient number of tested Zn concentrations resulting in a significant effect. ^g NP =^test not performed.

Conclusions:

Both inorganic and organic Zn complexation reduces Zn2+ activity and thus also reduce toxicity. Inorganic complexation (i. e. ZnCO3) is relatively straightforward, while dissolved organic matter (DOM) vary much in their zinc-binding characteristics. Therefore, for unknown samples, it is suggested to assume that the DOM consists of a fixed fraction of chemically active fulvic acid, i.e., 61%, which is the mean of optimal %AFA of the five abovementioned samples with which Zn titration studies were performed.

Executive summary:

Zinc toxicity to Daphnia magna was evaluated in a series of experiments with spiked natural surface waters. The eight selected freshwater samples had varying levels of bioavailability modifying parameters: pH (5.7–8.4), dissolved organic carbon (DOC, 2.48–22.9 mg/L), Ca (1.5–80 mg/L), Mg (0.79–18 mg/L), and Na (3.8–120 mg/L). In those waters, chronic zinc toxicity (expressed as 50% effective concentrations [EC50]) varied up to 5-fold for the D. magna (21 -d EC50 from 112 to 536 mg Zn/L). Both inorganic and organic Zn complexation reduces Zn2+ activity and thus also reduce toxicity. Inorganic complexation (i. e. ZnCO3) is relatively straightforward, while dissolved organic matter (DOM) vary much in their zinc-binding characteristics. Therefore, for unknown samples, it is suggested to assume that the DOM consists of a fixed fraction of chemically active fulvic acid, i.e., 61%, which is the mean of optimal %AFA of the five abovementioned samples with which Zn titration studies were performed.

Description of key information

There is no data available for the target substance zinc glucoheptonate on long-term toxicity towards aquatic invertebrates. However, there is data available for different zinc compounds. Since the ecotoxicity of zinc glucoheptonate is driven by zinc ion, this data is used within a frame of a weight-of-evidence approach to assess the toxicity of zinc glucoheptonate.

Chronic effect-concentrations of zinc on Daphnia magna and Ceriodaphnia dubia were found in literature. The values were converted to the target substance ZnGHA (table 1).

De Schamphelaere et al., 2005

Zinc toxicity to Daphnia magna was evaluated in a series of experiments with spiked natural surface waters. The eight selected freshwater samples had varying levels of bioavailability modifying parameters: pH (5.7–8.4), dissolved organic carbon (DOC, 2.48–22.9 mg/L), Ca (1.5–80 mg/L), Mg (0.79–18 mg/L), and Na (3.8–120 mg/L). In those waters, chronic zinc toxicity (expressed as 50% effective concentrations [EC50]) varied up to 5-fold for the D. magna (21 -d EC50 from 112 to 536 mg Zn/L). Both inorganic and organic Zn complexation reduces Zn2+ activity and thus also reduce toxicity. Inorganic complexation (i. e. ZnCO3) is relatively straightforward, while dissolved organic matter (DOM) vary much in their zinc-binding characteristics.

Muyssen and Janssen, 2002

In this study, the cladoceran Ceriodaphnia dubia was acclimated for 10 generations to four zinc concentrations ranging from 0 to 100 µg Zn/L and changes in zinc tolerance were monitored using chronic (9 days) assays. The chronic test results indicate that organisms acclimated to 50 and 100 µg Zn/L performed better (survival and reproduction). The reproduction and survival of organisms acclimated to 3 and 13 µg Zn/L was significantly lower than those acclimated to higher zinc concentrations. It can be concluded that culturing test animals in media lacking trace metals such as zinc could give rise to animals that are unnaturally sensitive to those same metals during toxicity tests.

Conclusion

The chronic EC50(21 d)-values for D. magna range between 0.71 mg ZnGHA/L and 3.38 mg ZnGHA/L and the NOEC lies between 0.4 and 3.1 mg ZnGHA/L (De Schamphelaere et al., 2005). This variation is explained by the protective effect of Na and DOC. Both concentrations are higher in the sample with the lower EC. In addition, the pH is decreased. pH has been shown to reduce zinc toxicity to D. magna, significantly (De Schamphelaere et al., 2005). The EC50-values obtained by Muyssen and Janssen (2002), converted to ZnGHA range between 2.23 and 3.09 mg ZnGHA/L. The chronic test results indicate that organisms acclimated to 50 and 100 µg Zn/L performed better (survival and reproduction), than organisms acclimated to lower concentrations of Zinc (3 and 13 µg Zn/L).

Table 1: Effect concentration (EC)-values from studies performed with elemental zinc (Zn2+) converted to ZnGHA

Species	Duration of exposure	Dose descriptor	Basis for effect	elemental Zn in source substance [µg/L]	ZnGHA (75%) [mg/L]	Impact	Reference
D. magna	21 d	EC50	reproduction	536	3.38	pH 6.8, DOC 17.3 mg/L, Ca 38.3 mg/L	De Schamphelaere et al., 2005
D. magna	21 d	EC50	reproduction	112	0.71	pH 7.3, DOC 2.53 mg/L, Ca 5 mg/L
D. magna	21 d	NOEC	reproduction	0.062	0.40	pH 6.0, DOC 5.37 mg/L, Ca 3.7 mg/L
D. magna	21 d	NOEC	reproduction	0.491	3.10	pH 6.8, DOC 17.3 mg/L, Ca 38.3 mg/L
C. dubia	9 d	EC50	mortality	354	2.23	acclimation to 3 µg Zn/L for 10 generations	Muyssen and Janssen 2002
C. dubia	9 d	EC50	mortality	387	2.44	acclimation to 13 µg Zn/L for 10 generations
C. dubia	9 d	EC50	mortality	449	2.83	acclimation to 50 µg Zn/L for 10 generations
C. dubia	9 d	EC50	mortality	489	3.09	acclimation to 100 µg Zn/L for 10 generations

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

3.1 mg/L