Bronopol, nitrosamine formation

Brononol (2-Bromo-2-nitropropane-1,3-diol) in combination with methyl and propyl paraben. The paper generated by the Danish group (ref. 5 Knoll BASF publication) shows that the mechanism of action of Bronopol is independent of formaldehyde formation. The inclusion of Tetrasodium EDTA at about 0.02% to remove ions in the water or extracts and carefully excluding any tertiary amines such as triethanolamine to counteract the fears of the marketers with reference to possible nitrosamine formation and release of formaldehyde. The pH used is usually at 6 and below. 

Animal toxicity studies have shown no evidence of phototoxicity or tumor occurrence when bronopol is applied to rodents topically or administered orally and there is no in vitro or in vivo evidence of mutagenicity this is despite the demonstrated potential of bronopol to liberate nitrite on decomposition, which in the presence of certain amines may generate nitrosamines. Formation of nitrosamines in formula-... 

Bronidox can be used as preservative for functional industrial fluids including cosmetics within a comparatively broad pH range (5-9). The average concentration is 01%. In terms of degradation and potential nitrosamine formation Bronidox and Bronopol behave analogously. Bronidox is mentioned in the EC list of preservatives for cosmetics (max. authorized concentration 01% limitations and requirements rinse-off products only avoid formation of nitro-samines). 

Thanks to its characteristics colourless and odourless, easily soluble in water and alcohol, low toxicity, good skin compatibility, broad effective spectrum , Bronopol is being used on a large scale as a preservative for cosmetics and pharmaceuticals (concentrations 0 01-01%). It is listed in the EC list of preservatives allowed for the in-can protection of cosmetics (max. authorized concentration 01% limitations and requirements avoid formation of nitrosamines). Since it is in acidic solutions that Bronopol features the highest stability, weakly acidic media are the ideal field of application. In neutral or weakly alkaline formulations there is a risk that Bronopol releases nitrite (see above) which, with defined amines and amides, forms nitrosamines and nitrosamides which are regarded as carcinogens. 

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