Reaction products of C16-18 (even numbered), C18 unsaturated alkylamines with C10-13 alkylbenzenesulfonic acid

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

other: Weight of Evidence Approach (WoE)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: The Weight of evidence approach (WoE) has to be applied as non of the tests or modelling results in itself can deliver a fully conlusive answer to bioconcentartion and bioaccumulation potential of Primary alkyl amines.

Qualifier:

no guideline available

Principles of method if other than guideline:

no guideline available

GLP compliance:

not specified

Type:

BCF

Value:

173 L/kg

Basis:

whole body d.w.

Calculation basis:

other: ADME Model

Validity criteria fulfilled:

not applicable

Conclusions:

The most suitable approach to derive a BCF for Primary alkyl amines is the ADME Model of Arnot and Gobas (2003) for the unprotonated C16 amine. Most likely this is conservative when the values are compared with the pH dependend results from Fu et al (2009).
Overall conclusion:
C16 amine is a model compound for the Primary alkyl amines. Therefore it is proposed to use for the Primary alkyl amines a BCFof 173 L/kg as estimated by the ADME Model of Arnot & Gobas (2003) on basis of a Weight of Evidence.

Executive summary:

Introduction

As Primary alkyl amines are readily biodegradable it can be expected that metabolism will occur in aquatic species like fish. This is confirmed by in vitro measurement of the metabolic rate of 1-Hexadecanamine (C16 amine) which was selected as model substance for the Primary alkyl amines. This means that establishing of the Bioconcentration factorBCFshould address Adsorption, Distribution, Metabolism and Excretion (so called ADME process).

Primary alkyl amines are cationic surfactants which sorb strongly to solid phases by van der Waals and ionic interactions (e.g. ion pair formation, cation exchange etc). This makes it extremely difficult or even impossible to ensure a constant concentration of the test item in a flow through system because of sorption but also by biodegradation as the test system is not sterile. Additionally as fish mucous is negatively charged the cationic surfactant is sorbing on the fish surface as in the test water used for aBCFtest no dissolved organice carbon (DOC) or suspended matter is present as it would under environmental conditions.

Usually for the determination of theBCFan OECD 305BCFtest would be carried out as the ADME process would be addressed completely. But due to the inherent properties of cationic surfactants technical issues arise and the measurement is likely to be highly uncertain and the result even not valid. Therefore also estimation procedures forBCFhave to be considered and evaluated for use in the context of this assessment under REACH.

 

Attempt to measure theBCFin an OECD 305 Test with 1-Hexadecanamine

Despite a high technical effort a constant flow through with acceptable analytical recoveries could not be established (Akzo Nobel, 2007). In addition due to the negatively charged fish surface continous sorption of C16 amine to the fish mucous took place. Therefore real steady state could not be observed. The calculatedBCFtaking into account the adsorbed fraction in the mucous gave high values which are unrealistic. Removing the adsorbed C16 amine with methanolic hydrogen chloride resulted inBCFvalues around 300 L/kg but the validity of this figure cannot be judged. The conclusion is that the conditions proposed in the OECD 305 Guideline do not fit to the intrinsic properties of the n-Primary alkyl amines in general. A test in natural river water which would mimic realistic environmental conditions may be more appropriate but could lead to analytical issues like insufficient sensitivity even when using 14C material.

Conclusion: This preliminary study shows that the conditions described in the OECD 305 Guideline will not be applicable for n-Primary alkyl amines. But alternative conditions e.g. use of river water might create other issues like insufficient analytical sensitivity.

 

Use of a Mechanistic model addressing ADME

Adsorption, Distribution, Metabolism and Excretion Models like the one from Arnot & Gobas (2003) describe the ADME process for a fish with help of mathematical algorithms. When such a model is applied to theunprotonatedn-Primary alkyl amines using measured fish metabolic rates lowBCFvalues will be calculated.

 

BCF   =  (1 – L_B⁾  + (k_uptake* f_diss/ (k_elimin + k_egestion+ k_growth+ k_metabol.))

 

L_B                          = Lipid fraction in organism

K_uptake    = uptake rate (estimated by: 1/(0.01 + 1/Kow)* Weight^0.4)

f_diss                         = fraction of dissolved substance

k_elimin                     = elimination rate (estimated by: k_uptake/ L_B* Kow)

k_egestion                   =  faecal egestion rate (estimated by: 0.02*Weight^-0.15* e^-0.06T/(5.1*10^-8*Kow+2)*0.125

k_growth                     =  0.0005*Weight^-0.2

_kmetabol.                              =  measured rate

 

 

Table4.2.1    Parameter values used in the Arnot & Gobas Model for 1-Hexdecanamine

Parameter	Value used in modelling	Remark
Log Kow	6.7	Estimated with US EPA KOWWIN V. 1.67 (USEPA, 2008
LB (lipid fraction)	0.2	Standard in model
Weight of fish (kg)	0.438	Av. Fish weight in study for carp metabolic rate (Bernard et al., 2006)
Temperature (deg C)	12	REACH Guidance R.16.4.3.1
ffreely diss (freely dissolved fraction)	0.2	Estimated from the differences in ecotoxcity measured in tap and in river water
kmetabolism  (1/d)	0.152	Lowest value from in vitro study (Bernhard et al, 2006)

 

Metabolic rates may not only be measured (Perdu-Durand et al, 2006) but could be estimated from Property property estimation programs like US EPA BCFBAF (US EPA, 2008).

 

Table4.2.2    Compilation of Km (Metabolic rate fish) for unprotonated & protonated C16 amine

                                                                        

The estimation program predicts much higher metabolism rates for the protonated C16 amine when compared with the unprotonated. The in vitro measured K_mis lower than the comparable values which were estimated.

Table4.2.3gives theBCFvalues calculated with the ADME Model from Arnot & Gobas (2003) using the parameter listed inTable4.2.1before as well as specific data. Log K_owwere taken from Table 1.3 and it was assumed that the metabolic rate for the n-Primary alkyl amines (C12 to C18) is the same.

 

 

 

 

Table4.2.3    BCFcalculated with an ADME Model using Parameters listed inTable4.2.1

Chain length n-Primary alkyl amines	BCFusing Log Kow(L/kg)	BCFusing Log Coct/Cwater(L/kg)
C12	162	168
C14	172	173
C16	173	173
C18	174	174
C18= (Oleyl)	173	175

 

The data fromTable4.2.3show that Log K_owdoes not influence theBCFmuch for this partitioning range. The reason is that the high measured metabolic rate controls theBCFoutput. TheBCFrange for the C12 to C18 amines is 162 to 174 L/kg with C16 amine 173 L/kg. So 1-Hexadecanmine (C16 amine) is a reasonable representative for the C12 to C18 n-Primary alkyl amines.

Conclusion:This model requires e.g. K_owas input parameter as well as a metabolic rate which can be measured either by in vitro methods (complex) or calculated by property estimation program like US EPA BCFBAF (US EPA, 2008). The adavantage of this model is that it addresses the ADME process for fish but can only cope with neutral molecules.

 

Use ofBCFProperty estimation programs

BCFproperty estimation programs like US EPA BCFBAF use correlations between Log K_owandBCFe.g.

                       LogBCF= 0.6598 log K_ow– 0.333 + correction

 

Such estimation programs address only the adsorption process of ADME but not distribution, metabolism and excretion. For rapidly biodegrable substances this may overestimate the trueBCFby far as metabolism is not taken into account. When using the log Kow of 6.7 for the unprotonated and and Log Coct/Cwater of 1.48 for the protonated C16 amine the US EPA BCFBAF model estimatesBCFof 500 for the unprotonated and aBCFof 4 for the protonated C16 amine.

Conclusion:Property estimation programs as the US EPA BCFBAF can supply quickly estimates but can address only the partitioning either for the unprotonated or the protonated amines but not for both in an equilibrium described by the pKa.

 

 

 

Use of a Model which can predict theBCFfor acids and bases in equilbrium

Fu et al (2009) have published a model which can estimate theBCFof acid and bases as function of the pH. The fraction of the unprotonated amine f_n can be calculated by the Henderson-Haselbalch equation 

                        f_n = 1 / (1+10^i(pKa-pH))   with i = 1 for bases

The apparent Kow for weak electrolytes also called D can be calculated by

                       D = f_n* Kow (unprotonated) + f_d* Kow (protonated)

K_ow(protonated) can be either calculated by

                       Log Kow (protonated) = Log Kow (unprotonated) – 3.5

or the measured Log Coct/Cwater for the protonated can be used.

Fu et al. analyzed available data for strong bases and found the following regression

                       LogBCF       =  0.24 Log D + 0.87

For the C16 amine theBCFcan be estamated as function of pH 4, 7 and 9

              

Table4.2.4    BCFas function of pH for the C16 amine

 

 

Conclusion:The model of Fu et al (2009) is the only which can address theBCFof acids and bases as function of the pH but it cannot be judged if cationic surfactants were included in the regression of the model. The model can also not address metabolism in e.g. fish.

 

Weight of Evidence Approach (WoE)

None of the approaches described in this chapter used to derive theBCFof Primary alkyl amines can give a reliable results which addresses the full ADME process especially for fish. Therefore a Weight of Evidence Approach has to be applied.

1) The test design for an OECD 305 test for the measuring of theBCFis not suitable. The result from this preliminary test has an uncertainty which cannot be judged.

2) The ADME model of Arnot & Gobas (2003) can address the ADME process but only for the unprotonated amine. Due to the relatively high metabolic rate from an in vitro measurement lowBCFare predicted based on uptake of the unprotonated C16 amine which is considered as a worst case assumption.

3) ClassicalBCFestimation methods based on Log K_ow,predict higherBCFvalues for the unprotonated than for the protonated C16 amine

4) The model of Fu et al (2009) is the only model which can address the coexisting protonated and unprotonated C16 amine as function of pH. Unfortunately it does address only the Adsorption of the ADME process and in addition it is not known if it is valid for cationic surfactants.

The most suitable approach to derive aBCFfor Primary alkyl amines is the ADME Model of Arnot and Gobas (2003) for the unprotonated C16 amine. Most likely this is conservative when the values are compared with the pH dependend results from Fu et al (2009).

Overall conclusion: 

C16 amine is a model compound for the Primary alkyl amines. Therefore it is proposed to usefor the Primary alkyl amines aBCFof 173 L/kgas estimated by the ADME Model of Arnot & Gobas (2003) on basis of a Weight of Evidence.

 

Description of key information

The registered substance is an uvcb, each constituent are predicted to be not bioaccumulable (BCF < 2000 L/kg). 

 

Considering a worst case approach, the predicted value for alkylamines constituents remains the highest predicted BCF value. Therefore the BCF = 173 L/kg was used for regulatory purpose to define the bioaccumulation potential of the registered reaction mass (EC 701-164-2). 

 

Key value for chemical safety assessment

BCF (aquatic species):

173 L/kg ww

Additional information

The registered substance is a reaction products of C16-18 (even numbered), C18 unsaturated alkylamines with C10-13 alkylbenzenesulfonic acid (EC 701-164-2). The reaction mass is constituted by both type of constituent (alkylamine and alkylbenzene sulfonic acid) are generally present with a 1:1 ratio. Bioaccumulation potential was estimated on both constituents which constitute the registered reaction mass (EC 701-164-2).

 

Regarding the Primary Alkylamine part of the reaction mass, the most suitable approach to derive a BCF is the ADME Model of Arnot and Gobas (2003) for the unprotonated C16 amine. C16 amine is a model compound for the Primary alkyl amines. Therefore it is proposed to use for the Primary alkyl amines a BCF of 173 L/kg as estimated by the ADME Model of Arnot & Gobas (2003) on basis of a Weight of Evidence.

 

Regarding the C10-13 alkylbenzenesulfonic acid part, the linear alkylbenzene sulfonate compound (C13) has been considered to predict the BCF and constitute a worst-case approach. QSAR estimation using the BCFBAF v3.01 of the EPISUITE 4.1 indicate that the BCF in fish of the C13 linear alkylbenzene sulfonate acid is 70.8 L/kg ww. The (Q)SAR is valid and was applied to a chemical falling within its applicability domain. 

This predicted value on the C13 Alkylbenzenesulphonate was supported by experimental studies available on similar substance:

- Freitag D, 1982 (publication similar to OECD 305, BCF = 130 L/kg, 3 days, Na n-Dodecylbenzene sulfonate (N salt), Leuciscus idus melanotus)

- Versteeg, 2003 (publication similar to OECD 305, BCF = 36 to 119 L/kg, 32 days, C12-LAS mixed isomer (97% of C12) Pimephales promelas & Ictalurus punctatus)

 

Considering a worst case approach, the predicted value for alkylamines constituents remains the highest predicted BCF value. Therefore the BCF = 173 L/kg was used for regulatory purpose to define the bioaccumulation potential of the registered reaction mass (EC 701-164-2).