Reaction mass of copper oxide and manganese dioxide

Endpoint summary

Description of key information

Key values for acute aquatic toxicity

Fish: 96h-LC50 (rainbow trout) > 143 mg/L submission substance (total fraction, nominal)

Daphnids: 48h-EC50 (Daphnia magna, mobility) = 0.3 mg Cu/L (dissolved, measured), corresponding to 732 mg/L submission substance (total fraction, nominal)

Algae: 72h-EbC50 (Pseudokirchneriella subcapitata, biomass) = 0.025 mg Cu/L (dissolved, measured), corresponding to 64 mg/L submission substance (total fraction, nominal)

Key value for chronic aquatic toxicity

Algae: 72h-NOEbC (Desmodesmus subspicatus, biomass) = 0.018 mg Cu/L (dissolved, measured / extrapolated), corresponding to 45 mg/L submission substance (total fraction, nominal)

Daphnids: 21d-NOEC (Daphnia magna, reproduction) = 0.028 mg Cu/L (dissolved, measured / extrapolated), corresponding to 69 mg/L submission substance (total fraction, nominal)

Fish: 60d-NOEC (brook trout, growth) = 5 µg Cu/L (dissolved, measured), corresponding to 0.21 mg/L submission substance (total fraction, measured / extrapolated)

Key value for toxicity to microorganisms

3h-EC50 (activated sludge, respiration inhibition) = 14 mg Cu/L (dissolved, nominal), corresponding to 580 mg/L submission substance (total fraction, nominal)

Additional information

Acute aquatic toxicity

Reliable key studies were available for the hazard assessment of acute toxicity to aquatic algae, invertebrates and fish for the submission substance reaction mass of copper oxide and manganese dioxide. No acute aquatic toxicity was observed for the constituent manganese dioxide up to the maximum water solubility (100% (v/v) saturated solution) in algae, daphnia and fish (studies performed acc. to OECD 201, 202 and 203, respectively; RL1; 2010). The constituent copper oxide was considered the hazardous constituent of the submission substance:

Toxicity of copper oxide to microalgae Pseudokirchneriella subcapitata was carried out according to OECD guideline 201, adopted 1984 (RL2, 2009). Measured effects (yield of biomass) followed a dose-response pattern. The 72h-EbC50 (green algae; biomass) = 64 mg/L submission substance (nominal, value recalculated based on the ratio of MnO2 and CuO in the reaction mass), corresponding to 0.025 mg/L dissolved copper (measured).   

Acute toxicity of copper oxide to Daphnia magna was carried out using DAPHTOXKIT F™ according to OECD 202 (RL2, 2008). Immobilisation of Daphnia magna occurred in a dose-response relationship. The derived nominal 48h-EC50 on immobilisation = 732 mg/L (recalculated based on the ratio of MnO2 and CuO in the reaction mass), corresponding to 0.3 mg/L dissolved copper (measured).

Acute toxicity of copper oxide to fish during 96 hours followed the principles of OECD 203 (RL2, 2011). Fish mortality was observed in concentration >= 1333 mg/L (value recalculated based on the ratio of MnO2 and CuO in the reaction mass). Mortality occurred in a dose-related manner. At the highest test concentration of 4444 mg/L (value recalculated based on the ratio of MnO2 and CuO in the reaction mass), mortality was not greater than 20%. The derived 96h-LC50 was > 4444 mg/L (nominal), corresponding to 0.04 mg/L dissolved copper (measured). With regard to sub-lethal observed effects, the measured tail beat frequency of carp was lower for exposed fish compared to the control.

In conclusion, the most sensitive effect concentration of the submission substance with regard to acute toxicity to the aquatic environment was the 72h-EbC50 (green algae; biomass) = 64 mg/L submission substance (total fraction, nominal), corrsponding to 0.025 mg/L dissolved copper (measured).

Chronic aquatic toxicity

Reliable key studies were available for the hazard assessment of chronic toxicity to aquatic algae, invertebrates and fish for the submission substance reaction mass of copper oxide and manganese dioxide (acc. to OECD 201, ISO 10706 (similar to OECD 211) and U.S. EPA proposed recommended bioassay procedure for egg and fry stages of freshwater fish, later as part of EPA OPPTS 850.1400).

With regard to chronic toxicity to aquatic algae, key studies were available with the constituents manganese dioxide and copper oxide. No toxic effect of manganese dioxide to green algae was observed during chronic exposure, and therefore no long-term hazard was expected for the constituent manganese dioxide (100% (v/v) saturated solution, OECD 201, RL1, 2010). Toxicity of copper oxide to microalgae Pseudokirchneriella subcapitata was carried out according to OECD guideline 201, adopted 1984 (RL2, 2009). Measured effects (yield of biomass) followed a dose-response pattern. The derived 72h-NOEC (green algae; biomass) = 45 mg/L (nominal, value recalculated based on the ratio of MnO2 and CuO in the reaction mass), corresponding to 0.018 mg/L dissolved copper (extrapolated based on measured dissolved copper fraction of 0.18% for nominal CuO concentration, see section 6.1.5, Aruoja et al. 2009).

With regard to chronic toxicity to aquatic invertebrates and fish for the submission substance reaction mass of copper oxide and manganese dioxide, available key studies were performed with copper oxide or dissolved copper. Copper oxide or copper was considered the hazardous constituent of the submission substance with regard to the aquatic environment. No chronic studies were available for chronic toxicity of manganese dioxide to aquatic invertebrates and fish. As the constituent manganese dioxide was of very low water solubility and no toxicity of manganese dioxide was observed in any of the acute toxicity studies on aquatic organisms nor in long-term exposure of green algae, using effect concentrations on the basis of copper oxide or copper was considered protective (see also attached read-across report, section 13).

Chronic toxicity to Daphnia magna for copper oxide was performed according to ISO 10706 (similar to OECD Guideline 211) (RL2, 2014). After 21 days of exposure, onset of birth of offspring was similar for all treatment groups, indicating that copper oxide had no effect on start of reproduction. The measured effects on reproduction did not follow a typical dose-response relationship. There was a significant increase of the number of neonates relative to the blank control. The observed effect was interpreted as the organisms' attempt to preserve the species under stressful conditions, which had been reported previously. Although no significant effects on the survival of neonates (longevity) were observed during 21 days of exposure, shortening of the apical spine was observed at the end of the tests. Effects on parental growth were observed at all test concentrations including the positive control, but without a dose-dependent pattern. The effect on growth was related to feed shortage caused by the negative effect of free copper on algae growth, which was used as feed (also observed in the study on green algae here). The effect was therefore not used as reliable endpoint for the inherent toxicity on Daphnia magna. Note that growth was the sensitive endpoint in fish long-term toxicity: though derived effect concentrations were considerably more sensitive and in the low µg/L range (see below). In conclusion, the derived 21d-NOEC on reproduction of Daphnia magna was 69 mg/L submission substance (based on increased number of offspring; value recalculated based on the ratio of MnO2 and CuO in the reaction mass), corresponding to 0.028 mg/L dissolved copper (extrapolated based on measured dissolved copper fraction of 0.18% for nominal CuO concentration, see section 6.1.5, Aruoja et al. 2009).

The key study on long-term toxicity in fish investigated effects of exposure to different heavy metals on six freshwater fish species (rainbow trout, lake trout, channel catfish, white sucker, bluegill, northern pike, walleye, brook trout) (RL2, 1976). To this end, adverse effects of copper on eggs and fry were examined in soft and hard water. Results for copper on the most sensitive fish species were used for aquatic hazard assessment. The most sensitive endpoint was juvenile growth in soft water for brook trout. Observed effects followed a dose-response relationship in general. Hatching and survival of offspring were not affected at lowest copper concentration, and growth was the most sensitive endpoint. The derived effect concentrations based on grwoth were: LOEC = 7 µg Cu/L and NOEC = 5 µg Cu/L. The respective effect concentrations based on the total fraction of the submission substance were 0.29 mg/L and 0.21 mg/L submission substance, respectively (value recalculated based on the dissolved copper fraction acc. to OECD 29, i.e. 2.42%, see section 4.8).

In conclusion, the most sensitive effect concentration of the submission substance with regard to long-term toxicity to the aquatic environment was the 60d-NOEC (brook trout, growth) = 5 µg Cu/L (dissolved, measured: arithm. mean), corresponding to 0.21 mg/L submission substance (total fraction).

Toxicity to microorganisms

Two reliable key studies and one supporting study were available for the hazard assessment of toxicity to microorganisms for the submission substance reaction mass of copper oxide and manganese dioxide.

Effect of the constituent manganese dioxide on the respiration of activated sewage sludge followed OECD 209 (testing up to limit test. conc.; RL1, 2010). The effect of the test material on the respiration of activated sewage sludge gave a 3h-EC50 > 1429 mg/L and a 3h-NOEC >= 1429 mg/L (value recalculated based on the ratio of MnO2 and CuO in the reaction mass). No hazard for microorganisms was anticipated for the constituent manganese dioxide.

Adverse effects of dissolved copper to microorganisms were assessed according to OECD 209 (RL2, 2004). The present study was cited by the OECD 209 for valid EC50 values for the proposed reference substance copper-(II)-sulfate pentahydrate, used as soluble copper salt. The derived lower EC50 value of the valid range was used for the environmental hazard assessment for the submission substance: 3h-EC50 = 14 mg Cu/L (dissolved, recalculated from copper-(II)-sulfate pentahydrate, 100% soluble copper salt), corresponding to 580 mg/L submission substance (value recalculated based on the dissolved copper fraction acc. to OECD 29, i.e. 2.42%, see section 4.8). In a supporting study, rapid toxicity of water-soluble copper (test item was copper sulfate) was investigated using a fed-batch reactor technique (RL2, 1996). As the study was performed with synthetic sewage sludge consisting of six bacterial colony types only, the derived effect concentration was considered not representative for realistic environmental conditions and too sensitive with respect to the limited number of bacterial types: 4h-EC50 = 6.5 mg Cu/L (dissolved, nominal), corresponding to 269 mg/L submission substance (value recalculated based on the dissolved copper fraction acc. to OECD 29).

In conclusion, copper was considered the toxic element of the submission substance with regard to microorganisms, and the relevant effect concentration was 3h-EC50 (respiration inhibition) = 14 mg Cu/L (dissolved, nominal), corresponding to 580 mg/L submission substance (total fraction).