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Environmental fate & pathways

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Environmental fate and pathways

In general, three routes of entry in the environment needs to be considered for textile dyes. These are:

- entry during or after the production of dyes and dye products,

- entry during or after application of dye products on the fabric and

- release of dye during and after the use of dyed products (wearing, washing, wasting).

The first route of environmental exposure is not relevant for Europe, as the dye is not produced within the EU anymore and the formulation of dye products is also not done in Europe maybe with a very few exceptions (business of distributors). In any case mixing and blending is done only at industrial level at dedicated industrial sites.

The second route of exposure, dyeing of textile fabrics, takes also place at dedicated industrial sites only. Disperse dyes are designed for dyeing of synthetic fibers used for sports and outdoor equipment, fashion and technical textiles for automotive and home textiles, while most of the volume ends up in the automotive sector. The dye is applied by exhaust-dyeing from a dye-bath with confirmed exhaust rates of ≥99 %, in case the dye is used below the saturation concentration of 2.4 % in the dyeing solution. During this process requiring high temperatures and pressure the dye melts up in the synthetic fiber at the so-called glass-transition point with no intention to be released again. This process requires an industrial setting and can therefore not be performed by professionals or consumers. That means in the wastewater of the dyeing solution less than 0.024 % of the dye is present that is introduced in the sewage treatment plant or collected to be incinerated as such. Remaining dye in the dye bath when introduced in the sewage treatment plant is precipitated in a first step within the local or communal waste-water treatment plants with an efficacy of again 90 % and the precipitate is incinerated subsequently. The adsorption/desorption study conducted with the test material demonstrated a log Koc-value of greater than 4 indicating the substance to adsorb to the activated sludge and will be eliminated by incineration. That means of 10 tons used for industrial dyeing, 9.9 tons are exhausted and bound to the fabric, another 0.09 tons is precipitate in the first clearance step to be incinerated and finally only 0.01 ton will be introduced in the activated sludge for biological clearance and either be degraded or attached to the microbial surface to be incinerated subsequently. That means far less than 10 kg of the original 10 tons of used dye might enter the environment per year and spread among different dyeing industries in whole Europe. In addition, as the chemical structure does not contain any metals or heavy metals, but organic structures only the incineration process is expected to be completely burn any remaining dye chemical and no elements will be set free that might propose any harm to the environment except CO2 or CO. Therefore, the entry into the environment of the dye chemical is very low. 

The third route of environmental exposure is estimated as follows. As long as textile fabrics (either fashion articles, sports and outdoor articles or technical textiles) are used as intended, leakage of dye out of the textile fabric is again negligible as explained already during the dyeing procedure in the upper paragraph.

For the automotive sector (9 out of 10 tons of the European market) no environmental exposure takes place at all because these articles are never washed throughout their whole life cycle.

For the apparel, sports and outdoor sector clothing articles we assume a life cycle of 50 wearing/washing cycles and we could demonstrate, that during 1 wash cycle dye leaks out the textile fabric in the range of less than 1 PPM. In case of 1 ton of dye this means 50 grams will be released throughout the life cycle equally spread over whole Europe within one calendar year. These 50 grams are then again cleared within the communal waste-water treatment plants the households are connected to and estimating a similar clearing efficacy for all waste-water treatment plants again 99 % of these 50 grams will adsorb to the activated sludge and will be incinerated subsequently. Further, it is assumed, that most of wasted textile articles are incinerated at the end of the article service life so also here no entry in the environment occurs.

Discussing environmental fate further, we again need to consider log Koc values measured. In case of dyes entering the environment apart from sewage treatment plans the measured Koc value indicates that the material is highly likely to adsorb on the soil or sediment. Concerning biodegradation, the BOD5/COD quotient calculated using data from several individual studies was less than 0.5 in each case, indicating the substance as not rapidly biodegradable. When tested for hydrolysis, FAT 36038/J was observed to be hydrolytically unstable after five days of incubation 50±0.5 °C in all the three buffers indicating the substance to be degraded hydrolytically in the environment. 


Taking results from the acute and chronic aquatic toxicity studies into account the results obtained in all tests conducted, indicate the test substance FAT 36038 to be not toxic to aquatic environment.


Finally, considering all information available on the substance, the chemical is considered to be not persistent, mobile or toxic and also not persistent and toxic. As the entry into the environment is regarded to be low and the fate and pathways are sufficiently described no further testing is required.

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