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Environmental fate & pathways

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Potassium bromide is an inorganic salt that dissociates to its composite ions in aqueous solutions at environmental pH and temperature. Comparison of the available data on the various bromide salts have shown that the bromide ion is the relevant ion for determination of the toxicological profile with simple cations such as potassium, sodium or ammonium, that are ubiquitous in nature, having little or no influence on the bromide ion properties. It is therefore justified to read-across data from other inorganic bromide salts to ammonium bromide.

The chemical nature of the bromide ion is such that it cannot biodegrade. The bromide ion is also stable to photolysis and abiotic degradation. This is demonstrated by the presence of significant quantities in certain environmental systems, e.g. sea water and some soils. Reported concentrations of bromide in freshwater are between 0.02 to 0.27 mg Br-/L, while for marine waters a range of 41 to 71 mg Br-/L is reported (Flury and Papritz, 1993). It is not clear whether the data of Flury and Papritz (1993) always refer to undisturbed areas, but at least the seawater data are expected to represent natural background concentrations. Cooper et al. (2007) cite Br- levels of 67 mg Br-/L at 35 ‰ salinity.

The high water solubility and negative charge of the ion suggest that this species will partition predominantly to the aqueous phase. The very low vapour pressure measured for potassium bromide indicates that the volatilisation of the ion into the atmosphere in quantities of concern will not occur.

The very high water solubility of potassium bromide suggests that the log Pow is very low. This, together with the measured low BCF of 0.23 for sodium bromide indicates that it is unlikely that potassium bromide will accumulate in biological membranes.