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Environmental fate & pathways

Hydrolysis

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Description of key information

In contact with water bronopol will hydrolyse rapidly.

Key value for chemical safety assessment

Additional information

In Annex VIII of Regulation (EC) no. 1907/2006 it is laid down that the study on hydrolysis does not need to be conducted if the substance is readily biodegradable. Although bronopol is readily biodegradable, the hydrolysing potential of the test substance has been investigated in a guideline study according to OECD 111 (preliminary test) at pH 4, 7 and 9 at 50°C in sterile buffer solutions [Knoll MicroCheck, 1996].

In water and at environmental relevant pH values, hydrolysis of Bronopol takes place very rapidly, with a significant pH and concentration dependency displaying an accelerated rate of hydrolysis at lower concentrations and elevated pH.

Decomposition of Bronopol in water results in the formation of tris(hydroxymethyl)-nitromethane, glycolic acid, formic acid, methanol (all <5%, 24 h) and 2,2-nitroethanol (<1%) which is shown in a supporting publication conducted by Challis and Yousaf, 1991. Four concurrent degradation pathways resulting in the production of these degradation products have to be considered, with 3 of them involving 2-bromo-2-nitroethanol as reactive intermediate. It could be shown that at pH 8.98 and 25°C, 2-bromo-2-nitroethanol is formed from Bronopol and increases in concentration over about 30 min following pseudo first-order kinetics. Thereafter, the concentration of 2-bromo-2-nitroethanol remained constant in equilibrium with the parent compound Bronopol. Moreover, Challis and Yousaf confirmed the fact that the degradation of Bronopol accelerates with increasing pH.