Magnesium diniobate

Endpoint summary

Description of key information

Aquatic toxicity studies with magnesium diniobate are not available, thus aquatic toxicity will be addressed with existing data on the dissociation products, i.e. magnesium and niobium ions.

 

Magnesium: Magnesium as an essential element has a very low potential for toxicity to freshwater and saltwater organisms.

Niobium: displays a very low mobility under all but the most extreme environmental conditions due to the high stability and very low solubility of niobium oxides. Thus, reported

Magnesium diniobate: The solubility of magnesium diniobate (MgNb2O6) in environmental media is expected to be low since dissolution in water resulted in Mg concentrations < 25 microg/L and Nb concentrations < 0.2 microg/L after 34 days. Aquatic toxicity is unlikely to occur since the substance is highly insoluble in water. Aquatic toxicity is also unlikely to occur since reported EC/LC50 values for short-term toxicity to algae, daphnia and microorganisms of niobium and short-term toxicity to algae, daphnia, fish and microorganisms of magnesium are at least 100-fold above the respective magnesium and niobium concentrations measured after dissolution in water for 34 days.

Additional information

Magnesium essentiality

The inorganic mineral elements are classified into two groups, the macro (major; > 1 g/L) and micro (trace; < 1 g/L [Soetan et al. 2010]) elements. The macro element magnesium, which is the most abundant divalent cation within living cells[Smith & Maguire, 1998], is essential to living organisms since it is an essential component of bones(including crustacean exoskeletons)and cartilage and an important activator of many key enzyme systems including kinases, (i.e. transfer of the terminal phosphate of ATP to sugar or other acceptors), mutases (transphosphorylation reactions), muscle ATPases and the enzymes cholinesterase, alkaline phosphatase, enolase, isocitric dehydrogenase, arginase, deoxyribonuclease and glutaminase. Moreover, Mg stimulates muscle and nerve irritability (contraction),is involved in the acid-base balance (pH regulation)and plays an important role in carbohydrate, protein and lipid metabolism[Tacon, 1987].Magnesium deficiency causes characteristic syndromes, reflecting its specific functions in the metabolism of animal or plants [Soetan et al. 2010].In general, Mg is readily absorbed through the gastro-intestinal tract (also gills of aquatic organisms) and transported in the blood plasma either in ionic form or bound to plasma proteins. Most of the Mg is stored primarily in bone (e.g. ~60 % for common carp [ADCP, 1978]), but also in muscle and extracellular fluids [Tacon, 1987]. The process of Mg homeostasis prevents any bioaccumulation [OECD SIDS, 2011] even at extremely high concentrations that may harm the organism. Finally, Mg can be excreted via urine (main route of excretion) and feces, but also via breast feeding (mammals) [OECD SIDS, 2011] or via the gills (fish), although the latter one has been shown to be rather limited [ADCP, 1978].

Mineral requirements as well as mineral functions are species-specificand are addressed in the respective endpoint summary of this dossier. It should further be kept in mind that minerals mutually interact affecting concentration and function of each single mineral [Soetan et al. 2010].

Reference

ADCP/REP/80/11 - Fish Feed Technology - Lectures presented at the FAO/UNDP Training Course in Fish Feed Technology, held at the College of Fisheries, University of Washington, Seattle, Washington, U.S.A., 9 October-15 December 1978.

OECD HPV Chemical Programme (2011), SIDS Initial Assessment Report for SIAM 32, National Institute of Environmental Research in Korea, Paris, France, p. 20.

Soetan, K.O., Olaiya, C.O., Oyewole, O.E., 2010. The importance of mineral elements for humans, Domestic animals and plants: a review. Afr. J. Food Sci. 4(5), 200–22.

Smith, R.L., and Maguire, M.E. (1998). Microbial magnesium transport: Unusual transporters searching for identity. Mol. Microbiol. 28(2), 217–226.

Tacon, A.G.I., 1987. The nutrition and feeding of farm fish and shrimp a training manual. 1. The essential nutrients. FAO Brasilia Brazil, GCP/RLA/075/ITA Field Document 2/E, p. 117.