Reaction products of sodium glucoheptonate with iron sulfate and ammonium hydroxide

Endpoint summary

Description of key information

There is no data available for the target substance iron glucoheptonate (CAS 23351 -51 -1) on toxicity towards aquatic organisms and microorganisms. However, there is data available for the read-across substances sodium gluconate, gluconic acid, iron dichloride, iron sulfate and iron salts. This data is used within a frame of a weight-of-evidence approach to assess the toxicity of iron glucoheptonate.

Fish

The LC50 (96 h) value of 46.6 mg/L reported in a study with iron dichloride on Oryzias latipes (OECD SIDS, 2004) was converted to the target substance FeGHA. The outcome is an LC50 (96 h) of 145.33 mg FeGHA/L.

The NOEC (96 h) reported for Sodium gluconate was > 100 mg/L.

Invertebrates

The EC50 (48 h) value of 19 mg/L reported in a study with iron dichloride on Daphnia magna (OECD SIDS, 2004) was converted to the target substance FeGHA. The outcome is a EC50 (48 h) of 59.26 mg/L. The EC50 (48 h) value reported for Sodium gluconate was > 1000 mg/L (OECD SIDS, 2004).

Algae

The ErC50 and NOErC (72 h) value of 6.9 mg/L and 2.4 mg/L reported in a study with iron dichloride on Selenastrum capricornutum (OECD SIDS, 2004) were converted to the target substance FeGHA. The outcome is an ErC50 (72 h) value of 21.52 mg/L and a NOErC of 7.48 mg/L.

The ErC50 and NOErC (72 h) values reported for Sodium gluconate on Desmodesmus subspicatus were 100 mg/L and > 100 mg/L (OECD SIDS, 2004).

Microorganisms

In a TOXcontrol® assay (MicroLAN BV, The Netherlands; Lopez-Roldan et al., 2012) withVibrio fisheri an EC50 (15 min) value of 52.08 mg Fe(III)/L was measured with the test substance Iron (III) sulfate hydrate. Converted to the target substance FeGHA, the EC50 (15 min) value is 369.14 mg FeGHA/L.

Additional information

General considerations

Ecotoxicological investigations concerning fish, aquatic invertebrates, algae and microorganisms are not available for the target substance Iron glucoheptonate (CAS 23351 -51 -1). However, sufficient data on read-across substances such as Sodium gluconate (CAS 527-07-01), Gluconic acid (CAS 526-95 -4), Iron sulphate (CAS 7720 -78 -7) and Iron (III) sulphate hydrate (CAS 15244-10-7) are available and have been used to cover the respective endpoints for the tonnage band of 10 - 100 tpa.

It is expected that the aquatic toxicity of Iron glucoheptonate is mainly driven by the release of the metal cation (i.e. iron). The release of the iron ion depends on several factors such as pH value, temperature, abundance of other ions and its stability constant within the chelate. An evaluation of these (numerous) dependencies was not possible since environmental conditions vary and conclusions which apply to a specific aquatic system cannot be transferred to another one. For the evaluation of the metal component of the substance, a total release of the iron ions into the aquatic environment is assumed.

In order to sufficiently asses the aquatic toxicity of Iron glucoheptonate, both data on gluconates as well as on iron salts are evaluated within a weight-of-evidence-approach to address the aquatic toxicity of iron dichloride. The (non)-effective/lethal concentrations of the test compounds have been converted in order to account for the target substance. These calculations are shown in detail in the respective subsections.

Short-term toxicity to fish

Data for the read-across substances Sodium gluconate (CAS 527-07-01) and Iron dichloride (CAS 7758-94-3) have been assessed.

The acute toxicity of the read-across substance Sodium gluconate (CAS 527-07-1) towards fish was determined according to OECD Guideline 203 in compliance with GLP (OECD SIDS, 2004). A range finding test (5 fish/vessel/concentration) was conducted before the definitive test. Based on the results of the range finding test, only two concentrations were tested in the definitive test: 0 and 100 mg/L (limit test). Oryzias latipes served as test organism. 10 fish/concentration were used for the definitive test. Neither toxicological symptoms nor any death were observed at 100 mg/L. Conclusively, the NOEC/LC0 (96 h) was set to > 100 mg/L based on the nominal concentration.

The acute toxicity of the read-across substance Iron dichloride (CAS 7758-94-3) towards fish was determined according to OECD Guideline 203 in compliance with GLP (OECD SIDS, 2004). The following test concentrations have been used: 0 (control), 10, 15, 24, 39, 63 and 100 mg/L (based on nominal concentrations). Measured concentrations were 11.7, 16.5, 24.0, 34.4, 62.6 and 99.2 mg/L (Method applied: ICP-AES). Oryzias latipes was chosen as test organism which was exposed for 96 h to the test substance. 7 fish were tested for each concentration (incl. control). At 39 mg/L test concentration, one dead fish was observed after 96 hours. At 63 mg/L, 6 dead fish were observed after 96 hours. At 100 mg/L, all fish died after 96 hours. When iron dichloride was dissolved in water, the test solution became acidic. The influence of the pH value on the mortality of the fish has, thus, been evaluated as well. The mortality was affected at pH 3.5 only. Therefore, mortality increase in 63 mg/L at 96 hours was due to the low pH. The LC50 (96 h) value was determined to be 46.6 mg/L (based on measured concentration). LC50 (96 h) with 95 % confidence limit was 36.1 – 61.5 mg/L.

In addition, the acute toxicity of Iron dichloride (CAS 7758-94-3) to fish (Labeo rohita) has been studied in a static test including the determination of 96-h LC50 values. No guideline was followed and GLP compliance was not fulfilled. The test was performed at constant temperature (30°C), pH (7) and hardness (100 mg/L). Three fish age groups (30-, 60- and 90-days) were tested for their sensitivity. Physico-chemical variables such as water temperature, pH, total hardness, dissolved oxygen, total ammonia, sodium, potassium and carbon dioxide were also studied during the experiment. 10 fish/concentration were tested (3 replicates/concentration) for an exposure duration of 96 hours. Specific test concentrations are not clarified. In order to avoid the sudden stress to fish, the concentrations of metals in aquariums were increased gradually, 50% test concentration being reached in three and half hours and full toxicant concentration in seven hours. The data obtained from analytical analyses (methods described in S.M.E.W.W., 1989) confirmed that the determined iron concentrations coincided with the estimated data. The fish had the lowest mean iron LC50 concentration of 49.75 ± 2.78 mg/L for 30-days fish, followed by that of 60- and 90-days that had the average values of 53.18 ± 2.74 and 58.18 ± 2.74 mg/L, respectively. The differences among three fish age groups for LC50 values were statistically significant. No mortality was observed among control fish.

Short-term toxicity to aquatic invertebrates

Data for the read-across substances Sodium gluconate (CAS 527-07-01) and Iron dichloride (CAS 7758-94-3) have been assessed.

 

The acute toxicity of the read-across substance Sodium gluconate (CAS 527-07-1) towards Daphnia magna has been determined according to OECD Guideline 202 in compliance with GLP (OECD SIDS, 2004a). After the range-finding study (2 vessels/concentration, 10 daphnids/concentration), the definitive test was conducted with test concentrations of 0 (control) and 1000 mg/L (limit test). The measured concentrations of the test substance in the test solution were within +/- 20% of the nominal concentration in all concentrations (HPLC technique has been used). The EC50/NOEC (48 h) value amounts to > 1000 mg/L based on the nominal test concentration.

AIn addition, a limit test with 1000 mg/L sodium gluconateon D. magna was conducted. The test organisms (5 daphnids/vessel) were exposed for 48 h to the test substance. The EC50 (48 h) value based on mobility was determined to be > 1000 mg/L. Toxic effects were not observed (OECD SIDS 2004b).

 

The acute toxicity of the read-across substance Iron dichloride (CAS 7758-94-3) towards Daphnia magna was determined according to OECD Guideline 202 in compliance with GLP (OECD SIDS, 2004). The following test concentrations have been used: 0 (control), 3, 6, 12, 23, 45 and 90 mg/L (based on nominal concentrations). Measured concentrations were 3.93, 7.14, 14.0, 24.2, 44.7 and 83.6 mg/L (Method applied: ICP-AES). The test organisms (3 replicates/concentration, 10 daphnids/vessel) were exposed for 48 h to the test substance. The EC50 (48 h) value based on mobility was determined to be 19 mg/L. EC50 (48 h) with 95 % confidence limit was 15 – 25 mg/L. EC50 value and 95 % confidence limit were calculated by Probit method (EPA/600/4-85/13, 1985).

Toxicity to aquatic algae

Data for the read-across substances Sodium gluconate (CAS 527-07-01), Gluconic acid (CAS 526-95-4) and Iron dichloride (CAS 7758-94-3) have been assessed.

The toxicity of the read-across substance Sodium gluconate (CAS 527-07-1) towards algae has been determined according to OECD Guideline 201 in compliance with GLP (OECD SIDS, 2004). Two tests have been performed. In the first test, 1000 mg/L of the test item have been tested. However, a decrease of the test item concentration was observed and therefore the test could not meet the stability requirements. Conclusively, a second test with 100 and 1000 mg/L test concentration was performed. Desmodesmus subspicatus CHODAT (strain No 86.81 SAG) was used as test organism. An initial cell density of 10 x 10E4 algae/mL was applied. For the second test, 3 flasks with 100 mg/L, 3 flasks with 1000 mg/L and 6 flasks without test item were used. The common OECD procedure has been modified by covering the test vessels with glass petri dishes to prevent contamination by micro-organisms. After 24, 48 and 72 hours, cell concentration was determined using a microscope with a counter chamber (8 fields counted). No cell growth inhibition at 100 mg/L was determined. At 1000 mg/L, 70% cell growth inhibition was observed. For the average specific growth rate, no inhibition at 100 mg/L but 42% inhibition at 1000 mg/L was determined. The cell concentrations in controls increased by a factor of 65.9 after 72 h. As final results and based on growth rate, an EC50 (72 h) of > 100 mg/L and a NOEC (72 h) of 100 mg/L were derived.

The acute toxicity of the read-across substance Iron dichloride (CAS 7758-94-3) towards algae (Selenastrum capricornutum, Strain: ATCC 22662) was determined according to OECD Guideline 201 in compliance with GLP (OECD SIDS, 2004). The test organisms were exposed to nominal concentrations of the test substance at 3, 6, 13, 25, 50 and 100 mg/L for 72 hours. Iron concentrations in the test solutions were analysed with ICP-AES (measured substance was total iron (Fe) and measured total iron concentration was converted into iron dichloride concentration in the test solution). The measured concentrations were 75 – 85 % of nominal concentrations. So, measured concentrations were used in the test instead of nominal concentration. An initial cells density of 1 x 10E4 cells/mL was used. Based on biomass, an EC50 (72 h) value of 3.8 mg/L and a NOEC (72 h) of 1.1 mg/L were estimated. Based on growth rate, the EC50 (72 h) was 6.9 mg/L while the NOEC (72 h) was 2.4 mg/L.

In addition, the acute toxicity of the read-across substance Sodium gluconate (CAS 527-07-1) towards algae was determined according to OECD Guideline 201 in compliance with GLP (OECD SIDS, 2004). A range-finding test was conducted prior to the definitive test to enable the following concentrations in the definitive test: 0 (control), 100, 180, 320, 560, 1000 mg/L (nominal concentrations). Measured concentrations of the test substance in the test solutions at the beginning of exposure were +/-20 % of the nominal concentrations. As test organism, Pseudokirchnerella subcapitata has been used (Biomass loading: 1 x 10 E04 cells/mL).As final results, the EC50 (72 h) was determined to be > 1000 mg/L while the NOEC (72 h) was set to 560 mg/L based on the growth rate (nominal concentration).

Furthermore, acute toxicity of four relatively new chelating agents and their equimolar manganese and cadmium complexes was studied (Silanpää et al., 2003). The chelating agents studied were gluconic acid (GA), β-alaninediacetic acid (ADA), diethylenetriaminepentakismethylenephosphonic acid (DTPMP), and nitrilotriacetic acid (NTA).The bioassay with R. subcapitata using gluconic acid was performed according to a Finnish standard SFS 5072 (1986, Toxicity test with pure culture of algae). At the time of an inoculation, the alga was in its exponential growth phase. During the test, the flasks were shaken in every 24 h. The volume in all tests was 10 mL and illumination intensity was set to 5000 lx. Temperature was maintained at 22 ± 1°C throughout the 72-h test. Two simultaneous experiments were performed for each test concentration and the highest concentration of chelating agents was 1000 mg/L. The growth was estimated with in vivo fluorescence of chlorophyll (Labsystems, Fluoroskan Ascent) and the results obtained from the bioassay are expressed as 72-h EC50 values with 95% confidence interval. The EC50 (72 h) value for gluconic acid is reported as 76 mg/L.R. subcapitata proved the most sensitive to these compounds compared to Daphnia magna and Photobacterium phosphoreum.

Toxicity to aquatic microorganisms

Data for the read-across substances Sodium gluconate (CAS 527-07-01), Iron sulphate (CAS 7720-78-7) and Iron (III) sulphate hydrate (CAS 15244-10-7) have been evaluated in a weight of evidence approach. All in all, four different studies are available which are briefly summarised as follows.

 

The toxicity of the read-across substance Sodium gluconate (CAS 527-07-1) was tested according to the German standard procedure DIN 38412, part 8 (Pseudomonas Zellvermehrungshemm-Test; OECD SIDS, 2004). As test organism, Pseudomonas putida has been used. Three different concentration ranges were tested: 0 -40 mg/L, 80 -5000 mg/L and > 5000 mg/L. It was reported that in the 0 -40 mg/L concentration range, no effect were observed. In the 80 -5000 mg/L concentration range, growth was stimulated. For the range of > 5000 mg/L, neither stimulation of growth nor toxic effects were observed. As final result, the EC0 (16 h) amounts to > 5000 mg/L.

The aquatic toxicity of the read-across substance Ferrous sulfate (CAS 7720 -78 -7) was determined using a Photobacterium phosphoreum Microtox test (Calleja et al., 1994). Exact test conditions such as substance concentrations are not mentioned. As final result, an EC50 (15 min) of 782 µmol/L (equals 118.7 mg/L) for Ferrous sulfate is reported.

 

The toxicity of the read-across substance Iron (III) sulfate hydrate (CAS 15244-10-7) towards aquatic microorganisms was determined by using TOXcontrol® assay (MicroLAN BV, The Netherlands; Roldan et al., 2012). The equipment works on the same basis as the certified methodology for the analysis of toxicity with Vibrio fisheri (ISO 11348-3; strain used: NRRL B-11177) but adapted to automatic equipment. TOXcontrol® is an advanced automatic on-line water toxicity monitor which gives an indication of the toxicity of the contaminants in water as a function of the emitted light. Series of five concentrations of each test solution were prepared and the measures were performed in triplicate. As positive control, zinc sulphate (2500 mg/L) has been used. For Fe (III), the standard solution contained 624 mg/L. The concentration range of the working solution is between 20 and 80 mg/L. Positive and negative controls of the measurements were done before and after each series of measurement. As final result, the EC50 (15 min) amounts to 52.08 mg Fe(III)/L.

The impact of iron salts on activated sludge and interaction with nitrite or nitrate was experimentally investigated and gives additional information referring to the evaluation of iron toxicity towards microorganisms (Philips et al., 2003). The influence of addition of Fe(II) or Fe(III), alone or together with NO2(-) or NO3(-) on bench-scale activated sludge reactors was examined. Large differences were established between the distinct treatments, regarding reactor performance, sludge characteristics as well as microbial community. Ferric iron was more detrimental than ferrous iron. In some cases, nitrite was found to enhance inhibitory effects of the added iron, whereas nitrate had more a neutralizing effect. It was found that precipitation of phosphate by the iron was not responsible for the observed inhibition. Decrease in pH upon formation of iron hydroxides and the impairment of the floc structure could partially explain the toxicity of the iron dosages.