Chromium iron oxide

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 iron oxide 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, 2010) that indicate a very low release of pigment components. Transformation/dissolution of chromium iron oxide (24-screening test according to Oecd Series 29, loading of 100 mg/L, pH 6 and 8) resulted in metal concentrations that are below the respective LODs for chromium and iron (< 0.5 µg/L). Dissolved chromium and iron concentrations remained also below the respective LOD after 7 days with 1 mg/L (and also 100 mg/L) and after 28 days with 1 mg/L at pH 6. Thus, the rate and extent to which chromium iron oxide produces soluble (bio)available ionic and other chromium- 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 chromium iron oxide 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).”

Regarding the potential of bioaccumulation for chromium, the EU RA on chromates (ECB, 2005) concludes that “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.

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 in aquatic environments can be expected to be low.

Thus, based on the poor solubility of chromium iron oxide in aquatic environments and essentiality and active regulation of internal concentrations if chromium (III) and iron, the potential of chromium iron oxide 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 iron oxide in accordance with Column 2 of Information Requirement 9.3.2., Annex IX, Commission Regulation (EU) 1907/2006.

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.

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.

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

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.