J. $oc. Cosmet. Chern. 29 3-24 (1978) The activity and safety of the antimicrobial agent Bronopol (2.bromo.2.nitropropan.1, $-diol) D. M. BRYCE, B. CROSHAW, J. E. HALL, V. R. HOLLAND and B. LESSEL The Boots Company Limited, Nottingham NG2 3.8.8 Synopsis Recent work on the microbiological activity, chemistry and safety of the antimicrobial agent Bronopol is reported. Methods for the estimation of Bronopol are described, and the nature of its decomposition products is discussed. Animal metabolism and toxicology results are reported, together with animal and human studies on irritancy and sensitisation. The performance of Bronopol in a number of experimental formulations is described. INTRODUCTION Early work by Hodge, Dawkins and Kropp (1) and by Zsolnai (2)suggestedthat geminal bromonitroalkanes had antifungal activity. The broad-spectrum antibacterial properties of 2-bromo-2-nitropropan-l,3-diol (Bronopol) have been described in a preliminary communication by Croshaw, Groves and Lessel (3) and in comparison with other members of a series of antimicrobial aliphatic halogeno-nitro compounds by Clark et al. (4). Bronopol is used as a preservative in various cosmetic, toiletry and household pre- parations particularly because of its high activity against Gram-negative bacteria, especially Pseudomonas aeruginosa and other pseudomonads. These organisms are com- mon residents in water and as such can cause contamination and spoilage problems in cosmetics and toiletties (5, 6, 7, 8). Pseudomonads are frequently implicated, particularly in oil-in-water emulsions which contain a significant amount of nonionic surfactants (9, 7, 10). Bronopol is an effective antibacterial preservative over a wide pH range. It is stable at acid pH's and is also useful as a labile antibacterial preservative in alkaline media. Because of its broad-spectrum antibacterial activity Bronopol can also be used as an active agent, for example, in aerosol formulations. Bronopol has been reported to show persistent activity on the skin by Marples and Kligman (11), this contrasts with the fact that in vitro it has been shown to have a weak growth-inhibitory effect on cultured human skin cells by Onoda and Saito (12). A programme of experimental work was begun some time ago to extend our knowl- edge on the safety of Bronopol. This work is now completed and it is appropriate to review the results of these and other hitherto unpublished studies on the microbiology, chemistry, analysis and formulation of this compound. 0037-9832/78/0100-0003 $02.00 ¸ 1978 Society of Cosmetic Chemists of Great Britain

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