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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

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Ecotoxicological information

Endpoint summary

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Description of key information

Additional information

In general, all relevant experimental results in this chapter were derived from studies on aquatic organisms, where the documentation and given results indicate that the study was well-performed and satisfies general scientific requirements. So all relevant studies were classified as reliable with restrictions and consequently, the results can considered to be reliable and used for classification and further risk assessment.


The LC50 values in a 96 h acute toxicity test in Colisa fasciatus with the read-across substance MnSO4 were determined to be 2850 mg/L (Agrawal SJ, 1980) and 3230 mg/L (Nath K, 1987), respectively, in US guideline studies. Therefore, these values can be considered as reliable as can be used for classification and further assessment. Since these studies were with the same species and the values are of the same magnitude, the LC50 value of manganese acetate can be estimated within the Weight-of-evidence approach as 3 g/L. This value does not trigger the classification of Manganese acetate, neither according to regulation 1272/2008/EC nor directive 67/548/EEC. Additionally, the available supporting studies further confirm the conclusion not to classify Manganese (II) acetate. With a LC50 value of 3 g/L, which is more than one magnitude above the limit for classification according 1272/2008/EC was set as </= 100 mg/L (LC50, 96h). Therefore, no further information on long-term toxicity was needed to be obtained because no extremely lower long-term value can be expected which is supported by that fact that manganese (II) acetate has no potential for bioaccumulation.


For the characterization of the possible adverse effects in invertebrates, the existing data suggest to follow the approach of assessing the two ions individually and perform the subsequent risk assessment, i.e. deriving PNECs, based on the more distressing ion.

Regarding the acetate anion, an EC50 value of 132 µl/L (approx. 132 mg/L) after 48 h was found in Artemia nauplii (Espiritu EQ, 1995), and an EC50 (48 h) of 65 ± 9 µl/L, corresponding to approx. 65 mg/L, was found in Daphnids. Taking into account the sensitivity of daphnids towards acidic conditions and the fact, that the pH was not adjusted in both experiments, the EC50 value would be much higher if pH was adjusted, preferably above 100 mg/L as already shown in Artemia nauplii. Additionally, it can be concluded from the magnitude of the observed EC50s, the NOEC in a chronic study will be above 1 mg/L. Acetic acid is part of many metabolic pathways, has an ionic structure and low molecular weight, so it can be concluded, that it has a low BCF and no toxic metabolites will be formed. In Summary, the observed EC50 values obtained from acetic acid and subsequent conclusions do not trigger classification.

When assessing the toxicity of the manganese (II) cation, most studies on the read across substances exhibited EC50, LC50, LC0 and LC100 values above 100 mg/L on several timepoints up to 7 d (see IUCLID section 6.1.3)

These high EC50, LC50, LC0 and LC100 values determined in aquatic invertebrate studies covering this endpoint do not reasonable indicate the necessity to perform long-term toxicity test because the NOEC which would be determined in these test is expected to be very high, too, i.e. much higher than the boundary value of 1 mg/L, which is especially supported by the LC0 values after 7 days: Carinogammarus Roeselii, LC0 = 45 mg/L; Tubifex tubifex, LC0 = 600 mg/L; Chironomus thummy larvae, LC0 = 750 mg/L; Anabolia nervosa larvae, LC0 = 3000 mg/L (Schweiger G, 1956). Additionally, the manganese (II) cation as an inorganic ion is neither expected to have a BCF500 nor a logKow4. Taking into account the classification criteria as set out in regulation 1272/2008/EC, Mn2+ does not trigger classification, and consequently, Manganese (II) acetate does not need to be classified as well as no further long-term testing is indicated.

As the key value (freshwater invertebrates) for further risk assessment the LC0 (7d) of 45 mg/L in Carinogammarus Roeselii was chosen. Since the determined EC50, LC50, LC0 and LC100 values do not indicate further long-term testing, the possibly best surrogate for a chronic NOAEL should be chosen. 7 days is the longest test duration available and the value LC0 indicates that no animal was affected, which corresponds very well to a No Observed Adverse Effects Level. Furthermore, Carinogammarus Roeselii was determined to be the most sensitive species. Consequently, when performing the further assessment of Manganese (II) acetate toxicity and deriving PNECs, it must be taken into account that 45 mg/L is not the usually used EC50 (48 h) value but the LC0 (7 d) value and subsequently lower assessment factors should be applied.

The EC50 for marine water invertebrates of 132 mg/L was chosen on the basis of the effects of Acetic acid on Artemia nauplii, although it is most likely to be caused by changes in the pH, because it is the only value available for marine water invertebrates.


For assessing the toxicity of Manganese (II) acetate in aquatic algae and cyanobacteria, the relevant EC50 and EC10 values were chosen from the study in Plectonema boryanum on the Manganese cation (Singh, 1975). Since P. boryanum is the more sensitive species, and the acetate anion does not pose any risk to aquatic algae, these values are used for classification: An EC50 value of approx. 0.2 mM Mn2+, which corresponds to 34.5 mg/ Manganese (II) acetate, was determined. Taking into account that Manganese (II) acetate as an inorganic salt has no potential for bioaccumulation and no effects were observed at the hypothetic concentration of 5.1 mg/L Mn(acO)2 after 10 days in this experiment, Manganese (II) acetate does not need to be classified according to regulation 1272/2008/EC. So, the determined EC10 value of 5.1 mg/L Mn(acO)2 can serve as a NOEL for further risk assessment.


In general, algae or other aquatic organisms serve as model organisms in order simulate actual environmental conditions and how a testing substance could affect them. Testing only on standard species can only give a limited insight in real conditions, and every testing on additional species, such as aquatic plants or higher tier mesocosm studies, could enlarge the insight, how a substance would affect the environment. So every testing on other aquatic plants or aquatic organisms in general would decrease the possible uncertainties due to extrapolation from only one species and hence, can serve to support the results from algae or other aquatic organisms toxicity testing and to lower any assessment factor.

Three studies, in addition to the non-standard organisms already included in IUCLID sections 6.1.1 and 6.1.3, are available to support the results from the testing on algae, fish and invertebrates and the conclusion that no classification of Manganese (II) acetate is required.

A study on Duckweed (Lemna minor) (Wang S, 1986) revealed a growth inhibition of 50% after 4 days at a concentration of 96 mg/L, corrected for Manganese (II) acetate and based on the increase of their front number. Two studies on aquatic protozoae, i.e. Tetrahymena pyriformis (Bogaerts P, 1998) with an IC50 (9h) of 650.6 mg/L, corrected for Manganese (II) acetate and based on growth inhibition, and Spirostomum ambiguum (Nalecz-Jawecki G, 1998) with an LC50 (48h) of 452.4 mg/L, corrected for Manganese (II) acetate and based on growth mortality, are available.

As the results from these studies broaden additionally the spectrum of aquatic organisms and, as additional models, allow a deeper insight in the expectable effects of the test substance on the aquatic environment, these results should be also taken into account when assessing the possible hazard of Manganese (II) acetate to the aquatic environment and consequently the need for classification.


Although the test durations and endpoints of these mentioned studies are not equal enough to allow one to plot them as a species sensitivity distribution, it can be clearly stated that the available endpoint for algae toxicity on Plectonema boryanum, i.e. an EC50 value of approx. 34.5 mg/L and an EC10 value of 5.1 mg/L Manganese (II) acetate after 10 days, can considered to be the most sensitive endpoint in the most sensitive species, and should therefore be taken into account when assessing the possible hazard of Manganese (II) acetate to the aquatic environment.


In summary, no classification of Manganese (II) acetate as hazardous to the aquatic environment is needed.