Dodecaaluminium trimolybdenum dodecaoxide

Bioaccumulation: aquatic / sediment

Description of key information

For Aluminium, the available evidence shows the absence of aluminium biomagnification across trophic levels both in aquatic and terrestrial food chains. The existing information suggests not only that aluminium does not biomagnify, but rather that it tends to exhibit biodilution at higher trophic levels in the food chain. More detailed information can be found in the attached document (White paper on waiving for secondary poisoning for Al & Fe compounds final report 02-02-2010. pdf).
All of the 27 BCF/BAF reported for Molybdenum ranged below 100 with the exception of one BAF measured for a mollusc exposed to background Mo water concentrations (BAF of 164). Further data demonstrates that Mo, like other essential elements, shows homeostatic control by organisms.

Additional information

No data on aquatic bioaccumulation 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

Bioconcentration factors (BCF) and/or bioaccumulation factors (BAF) are typically calculated in order to estimate bioaccumulation and biomagnification. However, it has recently been demonstrated that unlike many organic substances, the BCF/BAF is not independent of exposure concentration for many metals (Brix and Deforest, 2000 and Mc Geer et al., 2003). Rather it is inversely related (i. e., decreasing BCF/BAFs with increasing exposure concentration) to exposure concentration. Metal concentrations in tissue based on a range of exposure concentrations may be quite similar but the BCFs will be quite variable reflecting an inverse relationship (i. e., higher BCFs at lower exposure concentrations and lower BCFs at higher exposure concentrations) between metal concentrations and the corresponding BCF (Brix et al, 2001). From the above it is clear that any conclusion based on the application of classical concepts (e. g., use of bioconcentration factors; BCF -biomagnification factors; BMF) to metals as they are applied to organic substances should be treated with caution. As a result, use of a simple ratio C_biota/C_wateror C_biota/C_sedimentsas an overall approach for estimating bioconcentration factors for aluminium body burdens is not appropriate.

References:

Brix KV, DK DeForest (2000). Critical review of the use of bioconcentration factors for hazard classification of metals and metal compounds. OECD (Organization for Economic Cooperation and Development) Aquatic Hazards Extended Workshop Meeting, May 15, Paris, France.

Brix, K. V., DeForest, D. K. and Adams, W. J. (2001). Assessing acute and chronic copper risks to freshwater aquatic life using species sensitivity distributions for different taxonomic groups. Environmental Toxicology and Chemistry 20: 1846–1856.

Herrmann and Frick (1995). Do Stream Invertebrates Aluminium at low pH conditions? Water, Air and Soil Pollution 85: 407-412.

McGeer et al. (2003). Inverse relationship between bioconcentration factor and exposure concentration for metals; implications for hazard assessment of metals in the aquatic environment. Env. Tox. and Chem. 22, No 5.

Molybdenum

The current data set comprises thirty-five values that represent whole body Mo levels in fish (based on wet weight). Values are situated between 0.012 and 14.3 mg/kg wet weight, with a median Mo concentration of 0.22 mg/kg wet weight. Four values below detection limit were not included as the detection limit of <0.5 mg/kg wet weight was greater than the median value. Assuming that levels in these fish were equal to 0.5 mg/kg wet weight, a median value of 0.31 mg/kg wet weight is obtained. The 90th percentile of Mo concentration in whole body samples was 3.00 mg/kg wet weight.

Also available are Mo levels in fish compartments. Regardless of the exposure concentration, Mo levels in livers of fish ranged from <0.019 to 14.9 mg/kg wet weight (n=15), with a median value of 0.45 mg/kg wet weight, and a 90th percentile of 1.71 mg/kg wet weight. Mo levels in muscle samples were markedly lower, i.e., ranging from 0.01 to 7.59 mg/kg wet weight (n=15), with a median value of 0.043 mg/kg wet weight, and a 90th percentile of 0.924 mg/kg wet weight. Median Mo level in the muscle tissue is one order of magnitude lower than the median Mo level in liver samples.

Median levels for other organs like bone (n=4), brain (n=4), intestines (n=4), kidneys (n=4), skin (n=4), spleen (n=5) and stomach (n=4), were 0.185, 0.028, 0.064, 0.1184, 0.071, 0.092 and 0.041 mg/kg wet weight, respectively. For the gill only three data points were identified, ranging from 0.016 to 5.94 mg/kg wet weight.

Whole body Mo levels in crustaceans and other invertebrates ranged from 0.035 to 0.455 mg Mo/kg wet weight at background concentration levels in water. At a highly contaminated site, whole body internal concentrations ranged from 2.8 to 32 mg Mo/kg wet weight, although the Mo concentration in the water was not reported.

The data for Mo levels in other organisms (molluscs and phytoplankton) were also generally found below 1 mg Mo/kg wet weight.

Further to the data reviewed and presented here, Eisler (1989) made an exhaustive compilation of environmental concentrations of Mo, including the aquatic compartment. This review concluded also that Mo concentrations in algae, freshwater and marine fish and molluscs are all well below 10 mg/kg dry weight.

Reported whole-body BAFs vary more than 2 orders of magnitude but, as theoretically predicted for essential elements, there is a distinct close relationship between exposure concentration and BAF, i.e., decreasing BAFs with increasing Mo levels in the water column, showing homeostatic control of Mo by these organisms. The homeostatic control of Mo is observed to continue to function up to the milligramme range of exposure.

BCF/BAF could not be derived for all the studies that report internal Mo concentrations in organisms because not all studies report the Mo concentrations in water. From the data where BCF/BAF could be derived, it is noted that BCF/BAF range from 30.1 to 71.6 (average of 49) for fish exposed to background Mo concentrations in water (wet weight basis). The BCF/BAF range from 0.4 to 9.9 (average 1.4) for fish exposed to waters contaminated with Mo (with levels of Mo up to the mg/L range).

BCF/BAF range from 76.2 to 97.6 (average 84) for crustaceans exposed to background Mo concentrations in water (wet weight basis). A BAF of 4.8 was derived for crustaceans exposed to waters contaminated with Mo. For molluscs, the BCF/BAF ranged from 77.3 to 164.3 (average 121) exposed at background Mo concentrations (wet weight basis). No BCF/BAF could be derived for molluscs exposed to Mo contaminated waters.

For phytoplankton a BCF of 20.4 was derived from exposure at background Mo concentrations.

Some information on transfer of Mo through the food chain has been reported by Saiki et al. (1992) and Ikemoto et al. (2008).

In the report by Saiki et al. (1992), highest concentrations of molybdenum were found in detritus and filamentous algae, whereas low concentrations were reported in sediment, invertebrate and fish living in a river containing 10 ug/L Mo in the water. In the study by Ikemoto et al. (2008) the authors measured internal concentrations of Mo in phytoplankton, crustaceans and fish and conclude that there is no biomagnification of Mo across the aquatic foodchain.

These studies indicate that biomagnification of Mo is not significant in the aquatic foodchain.