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Environmental fate & pathways

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By the nature of their design and use, acid dyes are not intended to be readily biodegradable as this would assist in the rapid destruction of the dyestuff, rendering it unfit for purpose. As such, it is accepted that such substances are not readily biodegradable under relevant environmental conditions. A published study (Pagga & Brown, 1986) describes the results of the testing of 87 dyestuffs in short-term aerobic biodegradation tests. The authors of this publication concluded that dyestuffs are very unlikely to show any significant biodegradation in such tests and that 'there seems little point in carrying out such test procedures’ on dyestuffs. There are ISO, European, American (AATCC) and national standards available for the colour fastness of dyes. Dyes are required to have specific fastness properties. If the dyes were biodegradable, it would not be possible for them to have these fastness properties. 


References:


Pagga U, Brown D (1986) The degradation of dyestuffs: Part II. Behaviour of dyestuffs in aerobic biodegradation tests. Chemosphere 15: 479-491. 


 


Nevertheless, 97.75 % degradation was observed in an inherent biodegradability test conducted according to OECD Guideline 302B. In addition, the BOD5/COD ratio was found to be <0.5 indicating that the test substance FAT 20004 is not rapidly biodegradable. Hence, Acid Yellow 219 can be concluded to be inherently biodegradable without being readily biodegradable.

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