Quaternary ammonium compounds, bis(C16-18 and C18-unsatd. alkyl)dimethyl, chlorides

Endpoint summary

Description of key information

Biodegradation Screening tests

In the ECETOC Technical Report No. 53 'DHTDMAC - Aquatic and Terrestrial Hazard Assessment, CAS No. 61789 -80 -8' (ECETOC, 1993) as well as in the EU Risk Assessment 'DODMAC/DTHDMAC' (EU, 2002) the available Biodegradation Screening test results are given.

Read across from a structurally similar Quat (DHTDMAC, CAS No. 61789-80-8 ) can be applied.

When assessing the biodegradation behaviour of cationic surfactants like DTDMAC / DHTDMAC it is important to consider the following facts:

1. Bioavailability of the test substance may be reduced due to the formation of liquid crystals and vesicals. Therefore for cationic surfactant instead of an S shape biodegradation curve a more or less straight line may be observed which can be interpreted such that biodegradation is rate limited by the dissolution of the test item.


2. Cationic surfactants may show toxicity to microorganisms at concentration levels normally used for Biodegradation screening tests e.g. the EC50 for nitrifying bacteria is 2.1 mg/L for DHTDMAC. Usual test item concentrations are between 5 and 20 mg/L. Based on these facts biodegradation of cationic surfactants is often higher at lower test item concentrations which is also more environmentally relevant. Also the conditions in surface water / sediment may enhance biodegradation additionally. Adaptation of the microorganisms is another important parameter for biodegradation.

The fact that the test item DTDMAC is not readily biodegradable under the conditions of the tests listed below after 28d does not allow the conclusion that DHTDMAC/DTDMAC is recalcitrant or persistent in the Sewage treatment plant (STP) or the freshwater compartment. More adequate studies like e.g. OECD 303 A (STP Simulation Test) or e.g a River die away Test have to be used in order to derive adequate biodegradation kinetics (see IUCLID Chapter 5.2.2). Table 4.xx list the most important tests with the test setting and results.

 

Table 4.xx Biodegradation Screening tests of DHTMAC/DTDMAC

 

Test class	Test type	Guide-line	Endpoint	Exposure (d)	Test conc. (mg/L)	Adaptation	Elimination (%)	Biodegradation (%)	Year	Remark
Screening tests
	Ready	301 B	CO2 evolution	28	not given	no	n.a.	not observed	1988	Schöberl et al, 1988
	Ready	301D	BOD	180	10	no	n.a.	< 20	1991	van Ginkel & Kolvenbach, 1991
	Ready	301D	BOD	20	1	yes	n.a.	19	1991	Clancy & Tanner, 1991
				20	1	yes	n.a.	8	1991
				20	0.8	yes	n.a.	12	1991
				20	0.5	yes	n.a.	17	1991
				20	0.4	yes	n.a.	35	1991
	Ready	301D	BOD	28	2.6	no	n.a.	<20	1993	van Ginkel, 1993
			BOD	140	2.6	no	n.a.	33	1993
	Inherent	302B	DOC	15	not given	no	92	n.a.	1989	Hoechst, 1989d

 

 

 

The reliable and valid study (published; Geerts et al., 2015) performed similar / equivalent to OECD 303 A (January 2001) produced the following results:

Elimination from wastewater:

Considering a suspended solids concentration of 8 mg/L in the STP effluent (Franco et al., 2013 - monitoring data from full-scale activated sludge treatment systems), an elimination from waste-water (biodegradation and adsorption) of 96.07% (+/- 0.79%) was determined for the test item.

Biodegradation (primary):

The test item was demonstrated to be biodegraded by 69% (SD: 6.05%).

Organic carbon removal:

Based on the high NPOC removal from wastewater of > 88% (given for all cationic surfactants assessed; no details given for test item), formation of any soluble recalcitrant degradation products released into the effluent of STPs can be excluded.

Biodegradation in water: simulation testing on ultimate degradation in surface water:

Waiving according to REACH Annex IX, section 9.2., column 2: the chemical safety assessment does not indicate the need to investigate further the degradation of the substance and its degradation products. Substantiation:

1. a) PBT / vPvB properties can safely be excluded because the B-criterion is not fulfilled: based on a valid bioconcentration test on fish performed equivalent to OECD 305, BCF was between 13 and 32 L/kg (whole body ww). Also for sediment organisms, BSAF determined on L. variegatus and Tubifex were very low (0.28 and 0.78, respectively).


2. b) For all exposure scenarios, compartment specific risk characterization ratios for local fresh water had reliably been demonstrated to be pronouncedly below 1 (highest RCR: 0.152).

 

Monitoring data from the Austrian Federal Environmental Agency (UBA, 2005) that specifically relate to diC16 and diC18 dialkyl-dimethyl quaternary ammonium compounds are in support of the assumption that RCRs based on estimated PECs are conservative (see Annex 2 of the CSR for a detailed analysis of these data): based on measurements (incl. suspended particles) performed in June and August 2004 at 11 sites (in part downstream of STPs) of the Danube and tributaries around Vienna, the highest measured value (240 ng/L) is a factor of about 4 lower than the highest estimated PEC (941 ng/L), and the arithmetic mean of values measured in June (59 ng/L; higher than in August) is still lower than the lowest estimated PEC (66.3 ng/L).

Full consideration of the available literature on biodegradation of quaternary ammonium compounds including relevant analogues for DTDMAC is given in the read-across report (sections 1.4.2 and 1.4.4) attached in IUCLID section 13. Accordingly, it could be demonstrated that dialkyl-dimethyl quaternary ammonium compounds including DTDMAC can be fully mineralized (prolonged closed bottle test) albeit slow due to high adsorption. Specifically, even at minute dissolved concentrations in the presence of relevant solid adsorption surfaces (e.g. silica gel), long-chain dialkyl-dimethyl-QUATs are metabolized by microorganisms able to use this dissolved fraction as sole energy and carbon source (van Ginkel et al., 2003). Thus, degradation of the bioavailable fraction in river water will occur.

 

Biodegradation in water: sediment simulation testing:

Waiving according to REACH Annex IX, section 9.2., column 2: the chemical safety assessment does not indicate the need to investigate further the degradation of the substance and its degradation products. Substantiation:

1. a) PBT / vPvB properties can safely be excluded because the B-criterion is not fulfilled: based on a valid bioconcentration test on fish performed equivalent to OECD 305, BCF was between 13 and 32 L/kg (whole body ww). Also for sediment organisms, BSAF determined on L. variegatus and Tubifex were very low (0.28 and 0.78, respectively).


2. b) For all exposure scenarios, compartment specific risk characterization ratios for local fresh water sediment had reliably been demonstrated to be pronouncedly below 1 (highest RCR: 0.287).

 

Monitoring data from the Austrian Federal Environmental Agency (UBA, 2005) that specifically relate to diC16 and diC18 dialkyl-dimethyl quaternary ammonium compounds are in support of the assumption that RCRs based on estimated PECs are conservative (see Annex 2 of the CSR for a detailed analysis of these data): based on measurements of sediments performed in June and August 2004 at 11 sites (in part downstream of STPs) of the Danube and tributaries around Vienna, the highest measured value (2690 μg/kg sed. dw) is a factor of about 6 lower than the highest estimated PEC (15800 μg/kg sed. dw), and the arithmetic mean of values measured in August (546 μg/kg sed. dw; higher than in June) is still lower than the lowest estimated PEC (1113 μg/kg sed. dw).

Low concentrations modelled (PECs) and measured for / in river sediments do agree with low modelled (PECs) / measured aquatic concentrations and are plausible, considering that based on a valid OECD 303 A study (Geerts et al., 2015), elimination form waste-water in STPs is 96.07%, with a biodegradation extent of 69%.

 

Biodegradation in soil

Waiving according to REACH Annex IX, section 9.2., column 2: the chemical safety assessment does not indicate the need to investigate further the degradation of the substance and its degradation products. Substantiation:

1. a) PBT / vPvB properties can safely be excluded because the B-criterion is not fulfilled: based on a valid bioconcentration test on fish performed equivalent to OECD 305, BCF was between 13 and 32 L/kg (whole body ww). Also for sediment organisms, BSAF determined on L. variegatus and Tubifex were very low (0.28 and 0.78, respectively).


2. b) For all exposure scenarios, compartment specific risk characterization ratios for local agricultural soil had reliably been demonstrated to be pronouncedly below 1 (highest RCR with sludge to soil ‘yes’: 0.269).

 

Further, direct exposure of soil can be excluded based on the uses and corresponding exposure scenarios, and indirect exposure of agricultural soil via sludge to soil pathway will be low: based on a valid OECD 303 A study (Geerts et al., 2015), elimination form waste-water in STPs is 96.07%, biodegradation 69%, and such the remaining fraction adsorbed on sewage sludge limited to 27.1%. In the exposure estimation using CHESAR V3.4, in a conservative way an elimination from wastewater of 95% and an overall biodegradation of only 40% was assumed, resulting in a release to sludge of 55%. In spite of this, RCRs for agricultural soil are very low (see above).

Full consideration of the available literature on biodegradation of quaternary ammonium compounds including relevant analogues for DTDMAC is given in the read-across report (sections 1.4.2 and 1.4.4) attached in IUCLID section 13. Accordingly, it could be demonstrated that dialkyl-dimethyl quaternary ammonium compounds including DTDMAC can be fully mineralized (prolonged closed bottle test) albeit slow due to high adsorption. Specifically, even at minute dissolved concentrations in the presence of relevant solid adsorption surfaces (e.g. silica gel), long-chain dialkyl-dimethyl-QUATs are metabolized by microorganisms able to use this dissolved fraction as sole energy and carbon source (van Ginkel et al., 2003). Thus, degradation of the bioavailable fraction in soil will very likely occur as well.