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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Bioconcentration factors in fish for cetrimonium bromide have been reported to be 407-741, by the Japanese institute of Technology and Evaluation.

Key value for chemical safety assessment

BCF (aquatic species):
750 dimensionless

Additional information

Bioconcentration factors have been reported for cetrimonium bromide by the Japanese National Institute of Technology and Evaluation. The Japanese National institute of Technology and Evaluation (2002) reports BCF of 407 -741 for cetrimonium bromide at concentrations of 0.05 mg/L and BCF of 444 -677 at concentrations of 0.005 mg/L. The data are obtained in a standard 8-week bioconcentration test with carps. However, substantial information on the test conditions is lacking.

In a weight of evidence approach, datasets on structurally alike quaternary ammonium halides are included to support the results from the key study on bioaccumulation of cetrimonium bromide. The datasets in the weight of evidence approach represent experimental data as well as general considerations on the bioaccumulation of surfactants.

For the experimental data sets, read across is made to cetrimonium bromide. The justifications for read across are supported by the general considerations included in the weight of evidence approach. All read across are done to quaternary ammonium compounds with the same structure of the hydrophobic part (alkyl chain of C16), which has been shown to determine the bioconcentration of the surfactants (Versteeg & Shorter, 1992). 

A study by Knezovich et al. (1989) presents experimental data on fish, clams and tadpoles exposed to hexadecylpyridinium bromide in 24-h static experiments. The study reports BCFs of 165,130 and 170 for gill tissue and 21, 22 and 13 for whole body of the three different species.

In a continuous exposure study by Krzeminski et al. (1977), the BCF was determined after 60 days of exposure of C12-16 alkyldimethylbenzylammonium chloride to bluegill sunfish. The BCF values found were approximately 30 and 80 in tissue and viscera, respectively, indicating that the bioconcentration of this type of substance is limited.

Versteeg & Shorter (1992) examined the bioconcentration in a study on fathead minnow for three trimethylammonium chlorides of varying alkyl chain length; C16/18, C12 and C8. Uptake and depuration rate constants were estimated in short term experiments and BCF values were determined. The results showed that the bioconcentration of alkyltrimethylammonium chloride in fish increases with increasing length of the alkyl chain with BCF of 1962 L/kg for C16/18 trimethylammonium chloride. The presence of humic acid caused a lower uptake for C16/18 trimethylammonium chloride and a BCF of 141 L/kg, whereas no significant effect was observed on the uptake of C8 and C12 trimethylammonium chloride in fish. Based on the observations, it was suggested that the effect of organic carbon on bioavailability is a hydrophobic interaction rather than caused by the positive charge of the quaternary ammonium nitrogen.

The experimental studies included in this weight of evidence approach all used Liquid Scintillation Counting in the determination of BCFs. The method cannot distinguish between parent and metabolic compounds, and therefore the determined BCFs may be overestimates of the expected BCF of the substances. 

The general considerations on BCF of surfactants in reviews by Cooper (1988) and Tolls et al. (1994) are in accordance with the findings in the experimental studies. The reviews are pointing to the fact that surfactants in general should be considered non or low bioaccumulative, due to the nature of the molecules; high water solubility, low lipophilicity with low logPow (logPow <3) and high molecular weight (MW>200). These properties minimize transport of the substance across cell membranes. The experimental study by Knezovich et al. (1989) indicated that surfactants are mainly concentrated in gill tissue, as well as in the food in the intestines. Other tissues of toxicological interest, liver, kidneys accumulated only trace amounts of the surfactant, indicating that the transport of surfactant over membranes was limited.

The experimental studies also pointed out that the bioavailability is mainly determined by the hydrophobic part of the quaternary ammonium compounds rather than the positively charged part. In addition, environmental factors are important for the bioavailability of the surfactants which was indicated for C16/18 trimethylammonium chloride in the study by Versteeg & Shorter (1992). This means that BCFs derived in experimental systems without organic material may overestimate the BCFs expected in the presence of organic material.

The available studies provide sufficient evidence to conclude that cetrimonium bromide does not have a potential for bioaccumulation. The substance may bioaccumulate to some extent in aquatic organisms, but the experimental data provide evidence that the substance do not fulfill the B criterion (BCF > 2000 L/kg).