Iodine pentafluoride

Bioaccumulation: aquatic / sediment

Description of key information

Bioaccumulation for iodine pentafluoride is not to be expected as the substance instantly dissociates into iodate and fluoride ions. Data available on these ions indicates that bioaccumulation and/or secondary poisoning is unlikely to occur.

Additional information

Bioaccumulation of iodine pentafluoride as such will not occur as the substance rapidly and violently dissociates into its various ions. Data is available on uptake of iodine species (relevant for iodide and iodate) and fluoride ions. 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. The following information is available on bioaccumulation of iodine species and fluoride ions:

Iodine species:

Molecular iodine is a chemically unstable element with oxidizing properties and it is assumed that when iodine reaches fresh- or marine water systems it will speciate into iodate and iodide. In a document from the US Department of health and human services (US-DHHS, 2004 (and references therein)), it is stated that "Iodine has been shown to bioaccumulate in many seawater and freshwater aquatic plants. Freshwater plants (e.g., algae) contain 10-5% by weight of iodine, whereas marine plants (algae) contain 10-3% by weight. In freshwater fish, iodine concentrations in tissues range from 0.003 to 0.81 ppm, which gives concentration ratios (fish/water) of 0.9–810. In marine fish, the iodine concentrations range between 0.023 and 0.11 ppm, yielding concentration ratios of between 10 and 20". Further, "Aquatic bioaccumulation factors for iodine in fresh water are 40 (algae), 5 (invertebrates), and 15 (fish); in salt water, these factors are 4,000–10,000 (algae), 50–100 (invertebrates), and 10–20 (fish). Certain seaweeds and algae can concentrate iodine to levels as high as 0.8–4.5 g/kg of dried material; these high levels are usually associated with the relatively high levels of iodine in seawater (50 μg/kg)".

In a draft Competent Authority Report on iodine (CAR, draft april 2011), it is stated that "Bioaccumulation (BCF) values for iodine are generally low (0.001 to 810 for freshwater and marine fish, freshwater and marine invertebrates, marine and terrestrial plants), [...] although values up to 10000 have been found. However, the reported values should be treated with caution, since they are not acquired from bioaccumulation studies, but are merely a comparison of iodine content in the source and in the organism. High intracellular iodine concentrations may have other explanations, e.g. physiological processes like active transport and intracellular enzymatic reactions".

Based on the available data it may be concluded that iodine is concentrated by aquatic organisms from the surrounding water, and that the degree of concentration is species-dependent, varying from insignificant in fish and most invertebrates to highly significant in algae. In view of the decreasing BCF values with increasing trophic level in the food web (BCF algae > BCFinvertebrates > BCFfish), it is further concluded that biomagnification is of little significance.

Fluoride:

In the EU-RAR (ECB, 2001) on hydrogen fluoride, bioaccumulation of fluoride in freshwater and marine organisms is summarized as follows: “In aquatic organisms fluoride accumulates primarily in the exoskeleton of crustacea and in the bones of fish. No F accumulation was reported in edible tissues. In fish, BCF-values of 53-58 (d.w.) and <2 (w.w.) were found. In crustacea BCF-values based on whole body fluoride content are found to be <1 (d.w.). The highest reported BCF-value for Mollusca and aquatic macrophyta were 3.2 and 7.5 (w.w.), respectively. In an experimental marine ecosystem with fish, crustaceans and plants, F was found to accumulate in all species. The highest value, 149, was found in fish. BCF-values for crustacea range from 27 to 62. Fluoride concentrations up to 30 mg F/kg were found in consumption fish”.