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Biodegradation in water: screening tests

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Description of key information

neither readily nor inherently biodegradable

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

There are no experimental data available on the Leucophor 1111X, thus a read across approach with the structural analogous substance 01 has been proposed.

Analogous substance 01 was investigated for its ready biodegradability in a manometric respirometry test over 28 days, according to OECD Guideline for Testing of Chemicals No. 301 F (1992). The percent biodegradation of the test item was calculated based on the Chemical Oxygen Demand (COD) of 1.31 mg O2/mg test item. The Biochemical Oxygen Demand (BOD) of the test item in the test media slowly but gradually increased from about Exposure Day 2 until test termination after 28 days. At the end of the 28-day exposure period, the mean biodegradation of the test substance amounted to 32 %. Consequently, test item was found to be moderately biodegradable under the test conditions within 28 days.

The analogous substance 01 is a multicomponent substance, which has four main constituents. They are all 4,4’-bis(1,3,5-triazinyl-2-yl)amino)stilbene-2,2’-disulfonic acid derivatives. Despite in the test report is stated that calculation of ThOD was not possible due to the complex structure of the test item, the calculation for each one of the substance constituent can be performed. Since the nitrite and nitrate values recorded during the study were in a low range, showing that no significant nitrification occurred in the test media, the ThOD value has been calculated according to the formula that does not take into account nitrification.

Formula g/mol ThOD
mg O2/mg
% Biodegradation*
Constituent 01 C42H44N14O10S2.2C4H12NO 1149 1.45 32.4
Constituent 02 C42H44N14O10S2.2Na 1015 1.28 36.7
Constituent 03 C39H39N13O9S2.2C4H12NO  1078 1.45 32.4
Constituent 04 C39H39N13O9S2.2Na 944 1.27 37.0

*Based on the average of BOD calculated at the end of the test (47 mg O2/mg)

The amount of oxygen taken up by the microbial population during biodegradation of the test substance, corrected for uptake by the blank inoculum run in parallel, is expressed as a percentage of ThOD or, less satisfactorily COD. According to the OECD 301 guideline, when COD is determined there is the possibility of falsely high values of percentage biodegradation, due to the incomplete oxidation in the COD test.

As can be seen from the calculation of ThOD and the test results, the percentage of biodegradation at 28 days is comparable.

Leucophor 1111X is a Stilbene Fluorescent Whitening Agent (SFWA), 4,4’-bis(1,3,5-triazinyl-2-yl)amino)stilbene-2,2’-disulfonic acid (DAS) derivative. This class of substances have been available since 1941 and remain the most important class of optical brighteners in terms of quantity [1]. Some 75 derivatives have been put on the market [2]. Extensive work has been done to characterize aquatic toxicity and photo- and biodegradation: many data are available in the contexts of IUCLID dataset, OECD SIDS, HPV, HERA projects and some DAS derivatives have been registered under the REACH Regulation. In general, they are considered as neither readily nor inherently biodegradable.

An assessment of the ecological situation regarding the use of Stilbene Fluorescent Whitening Agents (SFWAs) is described in literature secondary source [3]. Data related to analogous substance 04, 05 and 08 are available: in laboratory tests the oxygen demand for SFWAs was zero, thus there was no degradation measurable by this method. In the review it is indicated that more satisfactory results were obtained in tests, in which the index of biodegradability was the difference between the amounts of total organic carbon (TOC) at the inflow and outflow as determined by chemical analyses. The reduction TOC was 96 % for analogous substance 04, 48 % for the analogous substance 08 and 28 % for the analogous substance 05. The results were interpreted as an indication that the adsorption on to the activated sludge was the first stage of elimination, aspect that is reported as confirmed by field trials at public sewage plants.

The analogous substance 04 has been submitted to the voluntary industry programme to carry out Human and Environmental Risk Assessments on ingredients of household cleaning products, known as HERA project. In the review document it is reported that the substance was tested on inherent biodegradation (OECD 302B) and was eliminated to 89.6 % after 3 hours, showing a DOC removal of 98.8 % after 21 days [4]. This indicated that the substance has been mostly removed by adsorption, rather than by biodegradation.

Furthermore, a field study at a full-scale STP on a analogous substance 04 gave no evidence of biodegradation when the mass flow was monitored (Poiger, 1994. IUCLID section 5.5.2).

In conclusion, Leucophor 1111X is considered and treated as neither readily nor inherently biodegradable.


[1] AAVV, 2003. Industrial dyes. Chemistry, Properties, Applications. Edited by Klaus Hunger. Wiley-vch.

[2] Siegrist A. E., Eckhardt C., Kaschig J., Schmidt E. 1991. Optical Brighteners in Ullmann’s Encyclopedia of Industrial Chemistry, vol. A18, VCH, Weinheim, pp. 153176.

[3] Zinkernagel R, 1975. Fluorescent whitening agents in the environment. Environ Qual Saf Suppl.;4:12.-42.

[4] HERA, 2004. Human & Environmental Risk Assessment on ingredients of European household cleaning products. Substance: Fluorescent Brightener FWA-1 (CAS 16090-02-1) - Draft - Version October 2004