Dodecaaluminium trimolybdenum dodecaoxide

Long-term toxicity to aquatic invertebrates

Description of key information

NOEC (21d) = 49.9 mg Mo/L for Daphnia magna (OECD 210) (read-across from sodium molybdate dihydrate)
EC10 (7d) = 0.021 mg Al/L for Ceriodaphnia dubia (US EPS guideline) (read-across from aluminium nitrate)

Additional information

No data on long-term toxicity to aquatic invertebrates are available for aluminium molybdenum oxide. However, there are reliable data available for different analogue substances.

The environmental fate pathways and ecotoxicity effects assessments for aluminium metal and aluminium compounds as well as for molybdenum metal and molybdenum compounds is based on the observation that adverse effects to aquatic, soil- and sediment-dwelling organisms are a consequence of exposure to the bioavailable ion, released by the parent compound. The result of this assumption is that the ecotoxicological behaviour will be similar for all soluble aluminium and molybdenum substances used in the presented ecotoxicity tests. As aluminium molybdenum oxide has shown to be only slightly soluble in water (pH 4.5, 7d) and poorly soluble in ecotoxicity test media (pH 7.5-8.5, 96h), it can be assumed that under environmental conditions in aqueous media, the components of the substance will be present in a bioavailable form only in minor amounts (Mo) or hardly, if at all (Al). Within this dossier all available data from soluble and insoluble aluminium and molybdenum substances are taken into account and used for the derivation of ecotoxicological and environmental fate endpoints, based on the aluminium ion and molybdenum ion. All data were pooled and considered as a worst-case assumption for the environment. However, it should be noted that this represents an unrealistic worst-case scenario, as under environmental conditions the concentration of soluble Al³⁺and MoO₄^2-ions released from aluminium molybdenum oxide is negligible (Al) or low (Mo), respectively.

Aluminium

Literature Review: Six long-term chronic toxicity studies to two species of aquatic invertebrates (Ceriodaphnia dubia and Daphnia magna) were identified as acceptable studies. EC_r10s were calculated using raw data provided from each study using the statistical program Toxicity Relationship Analysis Program (TRAP) version 1.10 from the US EPA National Health an Environmental Effects Research Laboratory (NHEERL). All other endpoints were as reported in each study. NOECs and EC10s ranged from 0.076 to 4.9 mg Al/L and 0.021 to 0.997 mg Al/L, respectively. Water quality data for these studies suggest a direct relationship between toxicity and pH, hardness, and DOC. For studies that experimentally manipulated water quality (e.g., CIMM 2009 and 2010a ), toxicity decreased with increasing pH, hardness, and DOC.

Recent studies conducted by the Chilean Mining and Metallurgy Research Center (CIMM) tested aluminium toxicity to C. dubia and D. magna (one data point) across a range of pH, DOC, and hardness values. These results demonstrated that increasing DOC concentration has a protective effect on aluminium LC50s for invertebrates. Increasing water hardness also had a protective effect. Aluminium toxicity was reduced at high pH, but a larger reduction was observed when changing pH from 6 to 7 than from 7 to 8. 

The acute fish BLM developed for S. salar was applied to the chronic invertebrate data (CIMM 2009, CIMM 2010; Figure 7.1.1.2.2.-1) by developing a critical accumulation value appropriate for this organism. In addition, the chronic invertebrate data suggested that overall fit would be improved with a small increase in the Ca binding parameter (i.e. the log K for Ca binding at the biotic ligand was increased from 4.2 to 4.8), which is the same adjusted value used in the chronic fish model. After application of the modified Al BLM, the variability in the response curve data substantially decreased (Figure 7.1.1.2.2.-2). These data were subsequently used to establish the CA10 (i.e. the critical accumulation level that results in a 10% reduction in reproduction), and likewise, the CA50. The CA10 and CA50 values can then be used to predict EC10 values and EC50 values in various water types.  

Figures 7.1.1.2.2.-3 and 7.1.1.2.2.-4 provide an evaluation of the ability of the chronic invertebrate Al BLM to predict EC50 and EC10 values. All of the EC50 values are predicted within 2-fold of the reported EC50 values. Most of the EC10 values are predicted within 2-fold of the reported EC10 values, and all of the predicted EC10 values are within 4-fold of the reported values. These results indicate that the chronic Al BLM performs reasonably well for predicting sublethal effects of Al on invertebrates. It should be noted that in both the fish and the invertebrate tests, saturation index calculations suggested that the majority of the toxicity values exceed Al(OH)₃solubility. However, bioavailability factors (i. e. pH, DOC, and hardness) still are consistent with the trends predicted by the Al BLM.

Two additional LC50 values that are not included in this comparison were reported for pH 7 and pH 8 in filtered test media (i. e., filtered before organisms were exposed). The filtered test media were approximately 5-fold less toxic, meaning that their LC50s were approximately 5-fold higher than the results from exposure to unfiltered media. Therefore, toxicity was largely a function of exposure to aluminium hydroxides, which are removed by filtration through these types of filters.

Molybdenum

Freshwater:

For the rotifer Brachionus calyciflorus the 48h-EC₁₀value of 193.6 mg/L is retained for assessment purposes (De Schamphelaere et al., 2008). EC₁₀values are preferred over NOEC values as the latter are test design-dependent values. In this specific case the 48h-EC₁₀is even more sensitive than the 48h-NOEC of 244 mg/L.

For Ceriodaphnia dubia two reliable studies were identified: GEI (2009) and De Schamphelaere et al. (2008). High quality data values were available for two endpoints, with reproduction being more sensitive than survival. The geometric mean of both studies, 63.0 mg Mo/L, was selected for assessment purposes.

For the midge Chironomus riparius the 14d-EC₁₀value of 121.4 mg/L is retained (De Schamphelaere et al., 2008). EC₁₀values are preferred over NOEC values as the latter are test design-dependent values. In this specific case the 14d-EC₁₀is more sensitive than the 14d-NOEC of 393 mg/L.

For the cladoceran Daphnia magna there were three studies that provided high quality effects data: GEI (2009), Rodriguez (2007) and De Schamphelaere et al. (2008a). Each of these studies reported 21d-EC₁₀values based on reproduction. The geometric mean of 89.5 mg/L that is derived with these three values (62.8, 105.6, 108 mg Mo/L) is put forward for D. magna for assessment purposes. 

Author, year	Species	Endpoint	Value [mg Mo/L]
De Schamphelaere et al., 2008	Daphnia magna	21 d NOEC (reproduction) EC10 (reproduction)	112 105.6
GEI, 2006	Daphnia magna	21 d NOEC (reproduction)  EC10 (reproduction)	96.3 - 192.3 108
Rodriguez, 2007	Daphnia magna	21 d NOEC (reproduction) EC10 (reproduction)	49.9 62.8
De Schamphelaere et al., 2008	Ceriodaphnia dubia	7 d NOEC (reproduction)  EC10 (reproduction)	97.3 78.2
GEI, 2006	Ceriodaphnia dubia	21 d NOEC (mortality)	156.5 - 161.5
		21 d EC10 (reproduction)	50.8
De Schamphelaere et al., 2008	Brachionus calyciflorus	48 h NOEC (reproduction)  EC10 (reproduction)	244 193.6
De Schamphelaere et al., 2008	Chironomus riparius	14 d NOEC (growth rate)  EC10 (growth rate)	393 121.4

 

Hence, the NOEC for freshwater invertebrates ranges from 49.9 to 393 mg Mo/L, and the EC10 ranges from 50.8 to 193.6 mg Mo/L.

 

Marine:

A reliable 20d-EC₁₀of 7.96 mg Mo/L has been generated for the marine copepod Acartia tonsa (Aquasense, 2009). EC₁₀values are preferred over NOEC values as the latter are test design-dependent values. In this specific case the 20d-EC₁₀is markedly lower than the 20d-NOEC of 26 mg Mo/L. The reported EC₁₀for A. tonsa is used for assessment purposes. A chronic 28d-growth and reproduction test has been conducted with the marine mysid shrimp Americamysis bahia (Lehman, 2010). No significant effects were noted at the highest exposure concentration level of 116 mg Mo/L (mean measured value). Evaluated endpoints were survival (first and second generation), reproduction (time of first brood, interbrood time, number of young produced per female), and growth (length and dry weight of male and female adult first generation organims). The unbounded value of 116 mg Mo/L is considered as a reliable and conservative NOEC-value for A. bahia.  

Conclusion

The effect values derived from analogue aluminium compounds are considerably lower than those derived from analogue molybdenum substances. However, these values were not considered for the assessment as it can be assumed that under environmental conditions in aqueous media, aluminium will predominantly be present as insoluble species (Al(OH)₃) and hence, will be present in a bioavailable form only in minor amounts, if at all. Therefore, it was concluded to put forward the most sensitive and reliable results derived from analogue molybdenum compounds for assessment purposes. Still, it should be noted that his represents an unrealistic worst-case scenario as under environmental conditions in aqueous media, the components of the sparingly soluble substance will be present in a bioavailable form only in minor amounts, and hence, the concentration of soluble MoO₄^2-ions released is very low.