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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Expert judgement combined with experimental data.
Justification for type of information:
R

Data source

Reference
Reference Type:
secondary source
Title:
Human & Evironmental Health Risk Assessment on ingredients of European household cleaning products. Alcohol Ethoxylates. September 2009
Author:
HERA
Year:
2009
Bibliographic source:
http://www.heraproject.com/RiskAssessment.cfm?SUBID=34

Materials and methods

Objective of study:
toxicokinetics
Principles of method if other than guideline:
No guideline followed.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Radiolabelling:
yes

Test animals

Species:
other: rat and human
Sex:
male/female
Details on test animals and environmental conditions:
not applicable

Administration / exposure

Route of administration:
oral: unspecified
Duration and frequency of treatment / exposure:
Various, for details see HERA report
Doses / concentrations
Remarks:
Doses / Concentrations:
Various, for details see HERA report
No. of animals per sex per dose:
Various, for details see HERA report
Control animals:
other: Various, for details see HERA report

Results and discussion

Main ADME resultsopen allclose all
Type:
absorption
Results:
The results suggest an almost complete absorption from the alimentary tract.
Type:
excretion
Results:
Mainly excreted via urine but as well in expired air and faeces. The relative proportions did not differ with the route of application.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
The major degradation pathway of AEs appears to be the degradation of the ether linkage and oxidation of the alkyl chain to form lower molecular weight polyethylene glycol-like materials and ultimately carbon dioxide and water. Studies with radio-labelled compounds showed that both the alkyl and the ethoxy groups are sites of attack. AE surfactants labelled either with 14C in the α-carbon of the alkyl group or the hydroxyl-bearing position of the ethoxylate moiety showed that distribution and excretion of ethoxylate groups of varying length was similar but the metabolism of their alkyl chains was a function of chain length. Metabolism of the alkyl chain seemed to change as the alkyl chain length increased with longer alkyl chains giving rise to a higher percentage of 14CO2 into expired air, and a lower percentage in urine.

Any other information on results incl. tables

In summary, 14C was excreted by the rats mainly in the urine after oral or parenteral administration of the compound. The relative proportions of compounds found in the urine, faeces, air and carcass did not differ with the route of application and the recoveries were close to 100% for all routes. Small proportions were recovered as 14CO2 and in the faeces. These proportions increased with longer ethoxylate length. The results suggest an almost complete absorption from the alimentary tract. There were indications that some of the longer ethoxylate chain compounds may be excreted via the bile or excreted into the intestine by other routes. Each detergent gave rise to two distinct polar metabolites in the urine and no parent compound. It was hypothesized that the alcohol chain was oxidized and the ethoxylate residue remained intact.

In the second study most of the administered compound was resorbed in the intestine (i.e., about 80-90%) of that approx. 30% was excreted via the bile and 2% was excreted as 14CO2 in air. Within 72 h about 98-99% of the compound was rapidly eliminated with 90% being excreted within the first 24 h. The test compound was excreted in the urine and in the faeces (i.e., about 40-50%) to equal amounts. Very low levels of residual radioactivity (i.e., about 1%) were noted in the liver and to an even lower extent in the kidney. No dose-dependant differences in elimination were observed. The test substance was excreted rapidly even at quite high doses. The highest dose did not cause any symptoms of toxicity within the test rats.

In the study with human volunteers most of the radioactivity (i.e., about 83-89%) for both compounds was recovered after 144 h in the urine, faeces and air. Amounts in the blood were very low and never exceeded 1%. In general, metabolism of these compounds in humans closely patterns the disposition in rats, namely that most of the radioactivity (75%) was excreted via the urine within the first 24 h whereas faecal and air elimination were lower: 5% and 4%, respectively. As seen in the rats C13AE6 and C12AE6 distribution and excretion of the ethoxylate groups of different AEs was similar, but the metabolism of their alkyl chains was function of chain length, with the longer chained compounds giving rise to more CO2 and less urinary elimination products.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
The most likely pathway of AE metabolism was predicted to be the hydrolysis of the ether linkage and subsequent oxidation of the alkyl chain.
Executive summary:

The mammalian absorption, distribution and excretion of AEs containing linear and branched carbon chains were comparable. When rats were administered C12AE6 (linear), C13AE6 (branched) and C15AE7 (branched) the distribution in the rat was similar with the major portion of the radioactivity appearing in the urine (52-55%) and smaller amounts in the faeces (23-27%) and expired CO2 (2-3%) for all three compounds.

In the study with human volunteers which examined the adsorption, distribution and excretion of 14C labelled C12AE6 (linear) and C13AE6 (branched), the behaviour of the two compounds in the males was comparable and most of the radioactivity was recovered after 24 h in the urine, 75% for both compounds.

The most important structural component determining the adsorption, distribution and excretion of AEs was therefore not the degree of branching of the alcohol but rather the length of the ethoxy chain unit with more of the AE being excreted via the faeces and expired in air as the ethoxy unit length increased. Also, the length of the alkyl chain may have determined how AEs were distributed in the rat. An oral gavage study with 14C labelled C14-18AE10 (linear) indicated that AEs with longer alkyl chains were excreted at a higher proportion into expired air and less into the urine and faeces (i.e., about 40-50%).

The major degradation pathway of AEs appears to be the hydrolysis of ether linkage and subsequent oxidation of the alkyl chain to form lower molecular weight polyethylene glycol-like materials and ultimately carbon dioxide and water. Oxidation of the alkyl chain and subsequent elimination via urine and expired air appears to be a common excretion pathway in aliphatic alcohols and branched-chain fatty acids.

Aliphatic alcohols are eliminated in humans by three pathways: oxidation, conjugation and elimination of the unchanged alcohol into the expired air and urine. Which route constituted a major pathway was contingent on physical and chemical factors of the alcohol including the number of carbon atoms in the alcohol, the nature of the alcoholic hydroxyl group and the extent of branching of the hydrocarbon chain. It is, however, not clear to which extent the branching of the carbon chain determined metabolism and elimination of the alcohol.

In other studies with AE surfactants labelled either with 14C in the first carbon of the alkyl group or the hydroxyl-bearing position of the ethoxylate moiety it was shown that distribution and excretion of ethoxylate groups of varying length was similar in rats but the metabolism of their alkyl chains was a function of chain length. Metabolism of the alkyl chain seemed to change as the alkyl chain length increased with longer alkyl chains giving rise to a higher percentage of 14CO2 into expired air, and a lower percentage in the rat’s urine.

As mentioned above the most likely pathway of AE metabolism was predicted to be the hydrolysis of the ether linkage and subsequent oxidation of the alkyl chain, however, no studies were found that looked at the route of metabolism of AEs in mammals.

It is therefore hard to predict if the pathway of metabolism of branched versus linear AEs would be significantly different. However, the above presented studies on the absorption, distribution and excretion serve to illustrate that the behaviour of the metabolites of the two different types of AEs is very similar and that other factors such as degree of ethoxylation and carbon chain length were probably more important structural determinants than branching of the alkyl chain.