Chromium tin calcium silicon sphene

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.”

Chromium tin calcium silicon sphene 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 (Pardo Martinez, 2013) that indicate a very low release of pigment components at pH 8. Transformation/dissolution of chromium tin calcium silicon sphene (24-screening test according to OECD Series 29) at a loading of 100 mg/L and pH 6 and 8 resulted in chromium concentrations below the LOD (< 0.5 µg/L) while tin concentrations of 5.4 and 11.5 µg Sn/L were measured, respectively. Thus, metal release from the pigment is maximised at pH 8. The dissolved chromium concentrations remained also below the LOD (< 0.5 µg/L) after 7 and 28 days in the T/D test with 1 mg/L loading at pH 8 while dissolved tin concentrations amount to 2.2 and 3.8 µg Sn/L, respectively. Calcium and silicon were not considered in the T/D assessment since they do not have an ecotoxic potential as confirmed by the absence of respective ecotoxicity reference values in the Metals classification tool (MeClas) database (see also OECD 2002 and 2004). Thus, the rate and extent to which chromium tin calcium silicon sphene produces soluble (bio)available ionic and other calcium-, chromium-, silicon- and tin-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 chromium tin calcium silicon sphene 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 calcium, chromium, silicon and tin can be summarized as follows:

According to OECD (2002), calcium is an essential constituent of the body of all animal species. “Calcium is essential for the formation of skeletons and the regulation of neural transmission, muscle contraction and coagulation of the blood… Calcium is known as an essential nutrient for higher plants and one of the basic inorganic elements of algae. Calcium plays crucial roles in strengthening cell walls and plant tissues, reducing the toxicity of soluble organic acids, elongating roots, and so on.” As an essential element calcium is actively regulated and thus its potential for bioaccumulation is low.

According to the EU RA on chromates (ECB, 2005) “uptake of chromium (III) directly from water is likely to be very low due to the limited water solubility and strong adsorption to sediment under most conditions found in the environment…Transfer of chromium via the alga -> bivalve, and sediment -> bivalve food chains appears to be relatively low.” A similar conclusion is reached by WHO (2009) in its assessment of inorganic chromium (III) compounds. “Chromium (III) is required by only some microorganisms for specific metabolic processes, such as glucose metabolism and enzyme stimulation. Chromium (III), in trace amounts, has been reported to be an essential component of animal nutrition and is most notably associated with glucose and fat metabolism (WHO, 2009).” For chromium as essential element, it is thus assumed that internal levels are homeostatically regulated and that it does not bioaccumulate and biomagnify in aquatic food-chains. Thus, the potential for bioaccumulation of chromium (III) in aquatic environments is low based on its poor solubility in environmental media.

According to OECD (2004), “the bioavailable forms of silica (SiO2) are dissolved silica [Si(OH)4] almost all of which is of natural origin. The ocean contains a huge sink of silica and silicates where a variety of the marine habitat (diatoms, radiolarians, and sponges) is able to exploit this resource as a construction material to build up their skeletons”. Most organisms contain silicon at least at trace levels. Whereas silicon is essential for some organisms, including diatom algae, gastropods and mammals, and actively taken up, others take it up passively and excrete it. “Due to the known inherent physico-chemical properties, absence of acute toxic effects as well as the ubiquitous presence of silica/silicates in the environment, there is no evidence of harmful long-term effects arising from exposure to synthetic amorphous silica/silicates (OECD, 2004).” Thus, given the ubiquitous presence of silica and silicates in the environment, silicon is regarded as element without or with a very low potential for bioconcentration and bioaccumulation.

According to the WHO (2005) and references therein, “tin is ubiquitous in animal tissues. There is evidence that tin is essential for growth in rats, but no essential function has been shown in other mammals, including humans… There is no information available on the potential transfer of inorganic tin compounds from lower trophic levels to higher levels.” A low potential for bioaccumulation of tin was observed in aquatic freshwater organisms, i.e. the bivalve mollusc, Brachidontes variabilis (Krauss), by Uensal et al. (1984), the highest BCF was determined with 6.41, and the rate of uptake decreased with increase in external tin concentration as typically observed for metals. Thus, it is concluded that tin ions have a low potential for bioaccumulation in freshwater organisms.


Based on the poor solubility of chromium tin calcium silicon sphene in aquatic environments, and essentiality and/or the low potential for bioaccumulation of calcium, chromium, silicon and tin, the potential of chromium tin calcium silicon sphene 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 chromium tin calcium silicon sphene in accordance with Column 2 of Information Requirement 9.3.2., Annex IX, Commission Regulation (EU) 1907/2006.

References:

ECB (2005) European Union Risk Assessment Report: Chromium trioxide, sodium chromate, sodium dichromate, ammonium dichromate and potassium dichromate. EUR 21508 EN.

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

OECD (2002) SIDS Initial Assessment Report Calcium Chloride CAS N°:10043-52-4. SIAM 15, 22-25 October 2002.

OECD (2004) SIDS Initial Assessment Profile Silicon dioxide, Silicic acid, aluminum sodium salt, Silicic acid, calcium salt. SIAM 19, 19-22 October 2004.

Uensal et al. (1984) Accumulation and loss of tin by mussel. Oceanol. Acta 7/4: 493-498.

WHO (2005) Concise International Chemical Assessment Document 65 (CICAD). Tin and inorganic tin compounds. International Programme of Chemical Safety (IPCS), WHO, Geneva.

WHO (2009) Concise International Chemical Assessment Document 76 (CICAD). Inorganic chromium (III) compounds. International Programme of Chemical Safety (IPCS), WHO, Geneva.