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Environmental fate & pathways

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Generally aquatic biotas regulate actively their internal concentrations of metals by active transport, storage or a combination of both. As a result of these processes which do often not discriminate non-essential metals, an inverse relationship gets established between water concentrations and the corresponding BCF of most metals. This means that organisms accumulate metals unspecifically to meet their metabolic requirements, whereat non-essential metals are moderately accumulated as well. At higher water concentrations, organisms with active regulation mechanisms are able to excrete excess metals or limit their uptake (ICMM 2007, Brix & DeForest, 2000). If such mechanisms apply, the typical figures are that metal concentrations in tissue based on a range of exposure concentrations may be quite similar, but the BCFs will be quite variable, i.e., higher BCFs occur at lower exposure concentrations and lower BCFs at higher exposure concentrations (ICMM 2007). The formation of metalorganic species on the other hand would lead to figures as known from organic chemicals. In conclusion not primarily the magnitude of measured BCF (if not alarmingly high) is indicative for evaluation but the establishment of an inverse relationship rather than apparent independence or a proportional one. The latter would be of concern while the former one is just the normal metal behaviour giving no indication for the formation of bioaccumulating species.

In conclusion the results of Frederici at al (2007), where such inverse relationship was found, lead to the assumption of little bioaccumulation.

Titanium is the ninth-most abundant element in the Earth's crust (0.63% by mass) occurring naturally as titanium dioxide (Barksdale 1968). Although it is widely distributed (Emsley 2001) no accumulation in wildlife biota is described in the literature. Thus supports the suggestion of a low potential for bioaccumulation.

No accumulation of the other hydrolysis product, hydrogen chloride (CAS 7647-01-0) and/or its dissociation products in living organisms is expected due to its high water solubility and hydrophilicity (OECD SIDS 2002 Hydrogen chloride SIAR).

  • Barksdale J (1968). “Titanium” in Hampel CA ed. The Encyclopedia of the Chemical Elements. New York. Reinhold Book Corporation. pp. 732–738. LCCN 68-29938
  • Brix K, DeForest, DK, Adams WJ (2001). Assessing acute and chronic copper risks to freshwater aquatic life using species sensitivity distributions for different taxonomic groups. Environmental Toxicology and Chemistry 20(8):1846-56.
  • Emsley J (2001). “Titanium”. Nature's Building Blocks: An A-Z Guide to the Elements. Oxford, England, UK: Oxford University Press. ISBN 0198503407
  • Federici G, Shaw BJ, Handy RD (2007). Toxicity of titanium dioxide nanoparticles to rainbow trout (Oncorhynchus mykiss): Gill injury, oxidative stress, and other physiological effects. PMID: 17727975, Aquatic Toxicology 84(4):415-30
  • ICMM (2007). MERAG: Metals Environmental Risk Assessment Guidance ISBN: 978-0-9553591-2-5, 80 p