Azo Dye Toxicity: a measure of toxic effect metabolized azo dyes have on the body

Azo dyes represent the world’s largest and most diverse group of synthetic dyes with uses spanning almost every industry (Pandey et al. 2007). Their significance to public health is great as these globally produced dyes have been proven to be carcinogenic upon biodegrading into their aromatic amines (Harmse 2013). But aside from their carcinogenic properties, azo dyes have another dangerous effect: their toxic ability to harm the intestinal bacteria that are most likely to digest them. I tested for azo dye metabolism in four dyes and three bacterial species and found all four azo dyes (Congo Red, Methyl Orange, Cibacron Red, Ponceau BS) were metabolized and created toxic metabolites by Enterococcus faecium and Suttonella indogenes, but Rhodococcus rhodochrous was only able to metabolize Congo Red and Methyl Orange. Despite this, the R. rhodochrous “metabolites” inserted into bacteria cultures, still incurred a toxic effect on bacterial growth. So, dye toxicity to bacterial growth was highest in those dyes metabolized the most, but also can be found in un-metabolized parent dyes. Therefore, the implication of our findings suggest the need for more research to help identify the toxicity of some 8000 azo dyes produced globally.