Chromium

Endpoint summary

Description of key information

According to Chapter R.7c: Endpoint specific guidance, the octanol-water partition coefficient (Kow) is not a useful predictive tool to assess the bioaccumulation potential for inorganic substances. Some indication may be given by read-across of bioaccumulation and toxicokinetic information from similar elements or chemical species of the same element. Factors such as ionic size, metabolism, oxidation state, etc., should be taken into account if sufficient data exist.

The same guidance establishes that: “the availability of inorganic substances for uptake may vary depending on factors such as pH, hardness, temperature and redox conditions, all of which may affect speciation. BCF values will therefore be influenced by water chemistry. In general, only dissolved ions are potentially available for direct uptake.”

 

In the light of the Chapter R.7c, a weight-of-evidence approach was carried out to assess the bioaccumulation potential of chromium metal and adaptation rules in column 2 of Annex IX, (9.3.2).

Chromium is a natural trace element and an essential metal to various life forms and therefore, the rules on bioaccumulation, bioconcentration and secondary poisoning, generally used for organic substances do not necessarily apply to chromium. In addition, the amounts of dissolved species from metallic chromium are so low that they hardly have any effect on the natural environmental background levels.

 

International Chromium Development Association (ICDA) has conducted between 2005 and 2010 a voluntary risk assessment which considered and concluded on the Environmental becoming of metallic chromium and trivalent chromium Compounds. The report is divided in 3 parts as follows:

1. Release characterization of Chromium III


2. PEC calculation


3. Risk characterization

Which allows to understand the bioaccumulation potential pf Chromium in the different compartments.

Literature data has also been assessed and several Klimish 2 studies have been selected and discussed to determine the bioaccumulation potency of chromium metal in aquatic (including sediment) and terrestrial compartments (Dweveldi et al., 2010 ; Yian et al., 2011 ; Dsikowtzky et al., 2013 ; Cheng et al., 2013 ; Di veroli et al., 2014; Milošković et al., 2016).

The different trophic levels, species, in different water and sediment confirm:

• Low bioavailability of trivalent chromium


• Very low BAF, BSAF and BMF


• The absence of human risk (HR) by assessing food chain in comparison with WHO FAD and USNAS reference recommendation.

Bioconcentration and biomagnification of trivalent chromium is not ever an issue for both water and soil organisms. Several studies conducted on several plant species:

• Parthenium hysterophorus,


• Solanum nigrum,


• Mentha spicata L.,


• Lippia citriodora L.,


• Mentha piperita L., or


• Allium cepa cv. Hybrid

exposed to soluble forms of chromium (choride and nitrate) and quoted Klimisch 2 demonstrated that chromium retains in roots (Razic & Dogo, 2010 ; Nematshashi et al., 2012 ; Dogo et al., 2010 ; Baruchas et al. 2014 ; Uddun et al., 2014) .  However, this confirms the absence of risk to human.

Regarding bioaccumulation to assess the evolution of chromium III across environment to potential human bioavailability and risk, several studies and authors defined chromium III bioaccumulation in different environmental compartments (water, soil, sediment) and in different species (algae, fishes).

Two studies, both scored Klimisch 2 evaluated chromium impact in situ illustrate this end point:

- The first one (Dvořák P et al., 2015) assessed data on the levels of heavy and toxic metals in water, sediment, and fish muscles obtained from European chub (Squalius cephalus), from 5 sites of the Morava river basin (Czech Republic) in the context of legal hygienic limits. The limit of chromium in surface water is defined as 18 μg.L–1 (Government Regulation No. 61/2003 in the Czech Republic). The values of contaminants in monitored locations did not exceed the limits set by the regulation. The hygienic limit for chromium i sediment is defined as 0.05 mg.kg–1 w.w. in Codex Alimentarius valid in the Czech Republic, respectively. The chromium did not exceed hygienic limits. Monitoring performed did not show any increased burden of the river system by observed pollutants from industrial agglomerations of Central and South Moravia.

The contaminants of tested metals including chromium did not exceed hygienic limits.

- In a second study (Kelepertzis et al., 2012) the concentrations of chromium [Cr], were determined in water, sediments, and tissue of tadpoles inhabiting these metalliferous streams to point out differences of heavy-metal bioaccumulation according to different levels of drainage sediment and stream water contamination.

All water samples had Cr levels that were either low or lower than the detection limit of the analytical technique.

 

The authors concluded that measured Cr levels were within the local background range for all of the sediment samples indicating that there are no significant sources for these elements. No significant changes of such parameters were observed during the 2-year period of the current study. As a result, sediment composition was considered to be unaltered between 2008 and 2010.

Transfer of chromium via the alga to bivalve, and sediment to bivalve food chains appears to be relatively low.  In addition, the available BAF values for chromium (III) indicate a low potential for bioaccumulation in aquatic and terrestrial environments based on spiking experiments and field studies. In addition, chromium is not expected to biomagnify in aquatic or terrestrial food-chains.