Textile and cosmetic colorants as a possible source of aromatic amines

Alemán. Azo dyes, the most important class of synthetic organic colorants, are widely used in textiles and cosmetics. The reductive cleavage of azo dyes into the corresponding aromatic amines by liver enzymes and the intestinal microflora is well known. Several aromatic amines are, or are suspected to be, mutagenic and carcinogenic. Some compounds of this class have an allergenic potential.In previous investigations we could show that azo dyes can be split into aromatic amines by human skin bacteria invitro . The aromatic amine o-tolidin is released from the water soluble colorant DirectBlue14 (CI23850). The lipophilic azo dye Disperse Orange3 (CI11005) is split into the aromatic amines 4nitroaniline and pphenylene diamine.We have now tested Disperse Yellow 3 (CI11855) as a further model substance. Due to the functional groups of the corresponding amines the analytical procedures for sample preparation had to be modified. Different recovery rates of the amines were found as a function of the method used for sample preparation. Analytical methods based on liquid extraction as well as new solid phase extraction method were validated. Chemical reduction of the azo dyes with sodium dithionite as well as HPLC of methanolic dye solutions were used to evaluate the dye content and purity of the commercially available products used in our study.The azo dyes CI Solvent Red (CI12150, Sudan Rot G), CI Acid Orange 24 (CI20170), and CI Acid Red 73 (CI27290, Crocein Scarlet) are positively listed for legal use in cosmetic products marketed in the EU (Directive 76/768/EEC). Assuming that azo cleavage can occur by the bacterial skin flora, the safety of these azo dyes has to be questioned. To assess the risk of these colorants, the formation of aromatic amines per se and the rate of formation by human skin flora might be important.We used our standard assay for incubating the azo dyes with skin bacteria combined with a modification of the analytical procedure (5 x 10¶9 cells in synthetic sweat, 28°C, 24 h, filtration, solid phase extraction, HPLC/DAD). We here demonstrate that all three dyes indeed release aromatic amines when incubated with human skin bacteria under both aerobic and anaerobic conditions. Anaerobic conditions usually result in the release of significantly higher amounts of amines. In the lower concentration range, azo cleavage increases in linear correlation with the dye concentration in the assay.The results indicate a potential exposure of consumers with carcinogenic aromatic amines by azo dyes used in cosmetics. We suggest that the use of these azo dyes in cosmetics should be reconsidered with respect to consumer health risk.Further studies with additional strains of bacteria and azo dyes as well as kinetic investigations are in progress.