Antimony nickel titanium rutile

Bioaccumulation: aquatic / sediment

Administrative data

Endpoint:

bioaccumulation in aquatic species: fish

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance has a low potential to cross biological membranes

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Column 2 of Information Requirement 9.3.2., Annex IX, Commission Regulation (EU) 1907/2006, ”The study need not be conducted if: the substance has a low potential for bioaccumulation (for instance a log Kow ≤ 3) and/or a low potential to cross biological membranes.”

Antimony nickel titanium rutile can be considered environmentally and biologically inert due to the characteristics of the synthetic process (calcination at a high temperature of approximately 1000°C), rendering the substance to be of a unique, stable crystalline structure in which all atoms are tightly bound and not prone to dissolution in environmental and physiological media. This assumption is supported by available transformation/dissolution data (Klawonn, 2017) that indicate a very low release of pigment components. Transformation/dissolution tests of antimony nickel titanium rutile for 24 h at a loading of 100 mg/L (24 h-screening test according to OECD Series 29) resulted in mean dissolved antimony concentrations of 1.893 and 1.607 µg Sb/L and dissolved nickel concentrations of 24.949 and 16.407 µg Ni/L at pH 6 and 8, respectively. According to ECHA Guidance on the Application of the CLP Criteria (Version 5.0, July 2017), “Where the acute ERV for the metal ions of concern is greater than 1 mg/L the metals need not be considered further in the classification scheme for acute hazard”. Further, “Where the chronic ERV for the metal ions of concern is greater than 1 mg/L, the metals need not be considered further in the classification scheme”. Accordingly, titanium was not considered in the T/D assessment since it does not have an ecotoxic potential as confirmed by ecotoxicity reference values of > 100 mg Ti/L listed in the Metals classification tool (MeClas) database. The release of antimony and nickel from antimony nickel titanium rutile in aqueous media is highest at pH 6 and thus pH 6 is considered as pH that maximises dissolution. Metal release at the 1 mg/L loading and pH 6 resulted in dissolved antimony and nickel concentrations of 1.610 µg Sb/L and 0.598 µg Ni/L after 7 days and 1.851 µg Sb/L and 0.480 µg Ni/L after 28 days, respectively. Thus, the rate and extent to which antimony nickel titanium rutile produces soluble (bio)available ionic and other antimony- or nickel-bearing species in environmental media is limited. Hence, the pigment can be considered as environmentally and biologically inert during short- and long-term exposure. The poor solubility of antimony nickel titanium rutile is expected to determine its behaviour and fate in the environment, including its low potential for bioaccumulation.

Further, “for naturally occurring substances such as metals, bioaccumulation is more complex, and many processes are available to modulate both accumulation and potential toxic impact. Many biota for example, tend to regulate internal concentrations of metals through (1) active regulation, (2) storage, or (3) a combination of active regulation and storage over a wide range of environmental exposure conditions. Although these homeostatic control mechanisms have evolved largely for essential metals, it should be noted that non-essential metals are also often regulated to varying degrees because the mechanisms for regulating essential metals are not entirely metal-specific (ECHA, 2008).”

The potential essentiality and bioaccumulation of the pigment components antimony, nickel and titanium can be summarized as follows:

An essential or beneficial effect of antimony is not known (Goyer et al, 2004). According to the EU Risk Assessment of diantimony trioxide (EU RAR, 2008), “The bioaccumulation potential seems to be low to moderate. No reliable bioaccumulation studies are available and measured data from different aquatic organisms have been used to calculate tentative BCF values. For marine fish the BCFs vary between 40 and 15000 whereas for freshwater fish the BCF values are lower, the highest being 14. For invertebrates tentative BCFs below 1 up to 4000-5000 have been calculated. It should be noted that there is a considerable uncertainty in these BCF values. The BCF value finally used in the risk characterisation is 40.” Hence, antimony is not expected to biomagnify.

Due to the importance of nickel in the catalytic activity of certain plant and bacterial enzymes, the WHO (1991) concludes that “Nickel has been shown to be essential for the nutrition of many microorganisms, a variety of plants, and for some vertebrates.” Regarding the potential of biomagnification of nickel, the WHO (1991) claims that “Accumulation factors in different trophic levels of aquatic food chains suggest that biomagnification of nickel along the food chain, at least in aquatic ecosystems, does not occur.”

Titanium has very low mobility under almost all environmental conditions, mainly due to the high stability of the insoluble oxide TiO2 under all, but the most acid conditions, i.e., below pH 2. There is no evidence to suggest that Ti performs any necessary role in the human body. Titanium is considered to be non-toxic, because of its poor absorption and retention in living organisms” (Salminen et al, 2005 and references therein). A similar conclusion was reached by WHO (1982) as follows: “There is no evidence of titanium being an essential element for man or animals”, and “…titanium is poorly absorbed and retained by both animals and plants…”. Thus, titanium is also not expected to bioaccumulate to any relevant extent or to biomagnify.

The OECD SIDS Initial Assessment (2002) of antimony nickel titanium rutile summarises: “No data on bioaccumulation are available. However, regarding the extremely low water solubility, experiences from rodent investigations and the structure-related inert properties of the rutile, bioavailability and therefore bioconcentration is not expected”. The OECD SIDS Initial Assessment (2002) concludes: “According to the low water solubility and the structural properties of the pigment, bioaccumulation is not expected”.

Thus, based on the poor solubility of antimony nickel titanium rutile in aquatic environments, the potential of antimony nickel titanium rutile for bioaccumulation can safely be expected to be low. Consequently, the study on bioaccumulation does not need to be conducted based on low solubility, bioavailability and a corresponding low bioaccumulation potential of antimony nickel titanium rutile in accordance with Column 2 of Information Requirement 9.3.2., Annex IX, Commission Regulation (EU) 1907/2006.

References:

ECHA (2008) Guidance on IR & CSA, Appendix R.7.13-2: Environmental risk assessment for metals and metal compounds. July 2008.

EU RAR (2008) Risk assessment - Diantimony trioxide, CAS No: 1309-64-4, EINECS No: 215-175-0. Final report, November 2008.

Goyer R et al (2004) Issue paper on the human health effects of metals. Submitted to U.S. Environmental Protection Agency, 19.08.2004.

OECD (2002) SIDS Initial Assessment Profile C.I. Pigment Yellow 5, CAS No. 8007-18-9. SIAM 15, 22-25 October 2002.

Salminen et al. (2005) Geochemical Atlas of Europe - Part 1: Background information, Methodology and Maps. EuroGeoSurveys.

WHO (1982) Environmental Health Criteria 24 - Titanium. International Programme on Chemical Safety.

WHO (1991) Environmental Health Criteria 108 – Nickel. International Programme on Chemical Safety.