High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix

Toxicity to birds

Administrative data

Endpoint:

long-term toxicity to birds

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Regulation (EC) 1907/2006, Annex X, Column 2, Section 9.6.1: “Any need for testing should be carefully considered taking into account the large mammalian dataset that is usually available at this tonnage level.”

According to the ECHA Guidance on information requirements and CSA (Chapter R.16: Environmental Exposure Estimation, Version: 2.1, October 2012), there is not a need for a detailed assessment of secondary poisoning i) if there are not any indications for bioaccumulation and ii) if there is not a potential for toxic effects if accumulated in higher organisms (based on classification on the basis of mammalian toxicity data).

Regarding mammalian toxicity and the relevant uptake via the oral pathway, signs of systemic toxicity were not observed in rats when administered at a dose of 1000 mg/kg bw/day for up to 28 days. Either no or only marginal increases in Fe plasma concentrations were observed, documenting the lack of bioavailability of this pigment (Leuschner, 2018). Thus, based on currently available information, the potential for systemic toxicity in mammals is low. According to the integrated testing strategy for avian toxicity in Figure R.7.10-2 of ECHA guidance on IR & CSA, R.7c (V 3.0, 2017), a mammalian hazard and risk cannot be identified. Thus, testing of High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is not required.

According to ECHA guidance on IR & CSA, R.10 (2008); “Secondary poisoning is concerned with toxic effects in the higher members of the food chain, either living in the aquatic or terrestrial environment, which result from ingestion of organisms from lower trophic levels that contain accumulated substances. Previous cases have demonstrated that severe effects can arise after exposure of animals via their food and that bioconcentration, bioaccumulation and biomagnification in food chains need to be considered.”

High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix 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 (Grané, 2010) that indicate a very low release of pigment components. Transformation/dissolution of High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix (24-screening test according to OECD Series 29, loading of 100 mg/L, pH 6 and 8) resulted in mean dissolved iron concentrations of 0.131 µg/L Fe and 0.002 µg/L Fe, silicon concentrations of 215.7 µg/L Si and 204 µg/L Si at pH 6 and 8, respectively. Dissolution of iron and silicon is highest at pH 6, therefore pH 6 is considered as pH that maximised metal release. Metal release at the 1 mg/L loading and pH 6 remained below the respective LOD for iron and silicon (<0.22 µg/L Fe and <0.07 µg/L Si). After 28 days at the 1 mg/L loading and pH 6 iron concentrations of 0.29 µg/L were measured whereas silicon concentrations remained below the LOD (< 0.07 µg/L Si). Thus, the rate and extent to which High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix produces soluble (bio)available ionic and other silicon- and iron-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 High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix is expected to determine its behaviour and fate in the environment, including its low potential for bioaccumulation and biomagnification.

Regarding essentiality, “Silicon is considered necessary for various functions in some species, including diatom algae, gastropods and mammals. Silicon deficiency in animals may lead to delays in growth, bone deformations and abnormal skeletal development, and one of the symptoms of silicon deficiency is aberrant connective and bone tissue metabolism (Pérez-Granados and Vaquero, 2002).

Iron as essential element plays a crucial role in a wide variety of biological process, i.e. electron transport, nitrogen fixation and oxidative metabolism. As an essential component of haemoglobin, it functions as a carrier of oxygen in the blood and muscles of animals. The uptake of iron into cells is actively regulated by a strict homeostatic control system. The active regulation of iron uptake in combination with internal detoxification mechanism indicates a low potential for iron bioaccumulation. This assumption is supported by results of Bustamante et al. (2000) indicating that iron concentrations of digestive glands of cephalopods living in natural and in iron-enriched habitats are similar. Winterbourn et al. (2000) further demonstrate that iron does not biomagnify but rather “biodilutes” up the aquatic food chain. Thus, the potential for bioaccumulation of iron in aquatic and terrestrial environments can be expected to be low.

Based on available information, there is not any indication of a bioaccumulation potential for High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix. In addition, the potential for systemic toxicity in birds and mammals is low. Hence, secondary poisoning is not considered relevant for High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix. In accordance with Regulation (EC) 1907/2006, Annex X, Column 2, Section 9.6.1, testing of High-temperature calcination products of diiron trioxide and amorphous silica resulting in a glassy silica matrix does not appear to be scientifically necessary and it is further scientifically not justified to conduct any toxicity study with birds for reasons of animal welfare.

References:

Bustamante et al. (2000) Bioaccumulation of 12 trace elements in the tissues of the nautilus Nautilus macromphalus from New Caledonia. Marine Pollution Bulletin 40/8: 688-696.

Winterbourn et al. (2000) Aluminium and iron burdens of aquatic biota in New Zealand streams contaminated by acid mine drainage: effects of trophic level. The Science of The Total Environment 254, 45-54.

Pérez-Granados and Vaquero (2002) Silicon, aluminium, arsenic and lithium: Essentiality and human health implications. The Journal of Nutrition Health and Aging 6/2:154-62.