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1. General remark on Biodegradation Testing

C20/22 ATQ inhibts sludge respiration at concentrations which are normally used in Screening test on biodegradation (ready and inherent tests). From an OECD209 Test the EC10 (3h) is 9.5 mg/L and the EC50 (3h) 43 mg/L which makes clear that the test concentration has to be selected carefully not to interfere with toxicity.

2. OECD 301 Type Screening tests

An OECD 301B CO2Evolution test was carried out at 10 and 5 mg/L test concentration for 28d. The biodegradation rate was higher at the lower concentration (see Table 5.2-1) but at these test concentrations the test criteria for ready biodegradation was not achieved. When carrying out the OECD 301B with [14C]-C22 ATQ at a test concentration of 0.2 mg/L the formation of CO2reached 80% after 28d.


Table 5.2-1  OECD 301 B Biodegradation results (see IUCLID Chapter 5.1.2) after 28d

 Test material Test conc. (mg/L)  Formation of CO2 (%) 
 C20/22 ATQ  10 21 
 C20/22 ATQ  5  40
 [14C] C22 ATQ  0.2  80
 C18 TMAC  1


(O2 Consumption)


C20/22 ATQ is readily and ultimately biodegradable at a concentration of 0.2 mg/L being which is higher than the STP influent concentration e.g. for manufacturing and cosmetic use of C20/22 ATQ.

In an Enhanced OECD 301D Closed bottle test (see REACH Guidance Document) at 0.5-2 mg/L different test settings were applied. For example Humic acid and river water with silica gel was used and the exposure time expanded up to 60 days. In two of the four test setting biodegradation exceed the test criteria of 60% but only after 60d.

.A second study was conducted to determine the biodegradation in water of the test substance, C18 TMAC (99.5% active) according to OECD guideline 301D, EU Method C.6 and ISO 10707 (Closed Bottle test), in compliance with GLP. The test was performed with activated sludge, domestic in 0.30L BOD (biological oxygen demand) bottles with glass stoppers. There were 10 bottles containing only river water, 6 bottles containing river water and sodium acetate, 10 bottles containing river water with the test substance. The concentrations of the test substance, and sodium acetate in the bottles were 1.0, and 6.7 mg/L, respectively. (A slight inhibition of the endogenous respiration of the inoculum by the test substance was detected at day 7. Therefore, limited inhibition of the biodegradation due to the "high" initial concentration of the test compound is expected. This toxicity was the reason for testing at an initial test compound concentration of 1.0 mg/L). The test substance was biodegraded by 77% and 73% by the end of 28 days using and ThODNH3 and ThODNO3 equations respectively. The test was valid, as shown by an endogenous respiration of 1.1 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 66% of its theoretical oxygen demand after 14 day. Oxygen concentrations remained >0.5 mg/ L in all bottles during the test period. Under the study conditions, the test substance can be considered readily biodegradable (van Ginkel, 2005).

OECD 303A C20/22 ATQ Simulation Test Activated Sludge Unit -Aerobic Sewage Treatment
C20/22 ATQ was continuously dosed into the activated sludge unit resulting in an influent concentration of 300 µg/L (41 µg/L C20 isomer, 243 µg/L C22 isomer). Influent and effluent concentration of C20/22 ATQ were measured daily using LC MS MS (LOQ C20influent= 4.1 µg/L, C22 24.3 µg/L; LOQ C20effluent= 2.1 µg/L, C22 12.1 µg/L). Already one day after the start of the test the elimination of C20/22 ATQ was > 99% (C20 and C22 fraction). Biodegradation of C20/22 ATQ has started immediately and reached a maximum of 98% during the plateau phase. Biodegradation of the C20 fraction was 94-98% (median 96%) and of the C22 fraction 87-93% (median 91%).

OECD 308

Docosyltrimethylammonium Chloride (DTAC) was steadily degraded in two water-sediment systems to carbon dioxide.  Dissipation rates of DTAC from the water phases in the Calwich Abbey and Lumsdale systems, under the experimental conditions gave DT50 (water) values of 4.16 days and 1.19 days, respectively.  Disappearance times calculated for DTAC in the total system under the experimental conditions gave DT50 (total) values of 29.0 days and 56.7 days obtained for Calwich Abbey and Lumsdale sediment systems, respectively.

OECD 309

[14C]Carbon dioxide was a major product of degradation in both the low and high application rate of the surfactant [14C]Docosyltrimethylammonium chloride.  The rate of transformation was moderate and consistent throughout the study, where the DT50 (half-life) was 101 and 166 days for the high and low application rates respectively.  No major metabolites were identified, but one minor metabolite was present within the high application rate vessels and identified as desaturated [14C]Docosyltrimethylammonium chloride (– 2H).


OECD 307 Aerobic Transformation in Soil, Key study

According Annex IX, Section column 2 of the REACH Regulation 1907/2006/EC a Soil simulation test need not to be carried out if the substance is readily biodegradable. Nevertheless available information is provided using read across from the supporting substance C22-ATQ (CAS 17301-53-0). The degradation rate of 14C-C22 -ATQ in three aerobic soils was investigated during 124 days. The 14C-labelled substance was applied at a rate of 0.2 mg a.i./kg soil dw. using sewage sludge as carrier. The application rate was determined from an exposure modelling using realistic use rates. Soil sampling was done after 3, 7, 14, 29, 62 and 124 days. Significant amounts of radioactive carbon dioxide and bound residues were formed. The total mean recoveries of radioactivity were in the range of 105 to 107% for the three soils. From the measurements the following DT50 for biotransformation were calculated:

DT50 soil 1: 23.2 d;

DT50 soil 2: 24.9 d;

DT50 soil 3: 41.4 d,

Additional information