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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

- There is no experimental information available on the bioaccumulation potential of cholesterol.
- The REACH guidance on information requirements and chemical safety assessment Chapter R.7.10 describes some QSAR models based on a correlation between BCF and logKow. The modified Connell equation is a non-linear equation showing better performance for substances with a log Kow of 6 or higher than linear equations. The result is a high BCF of 25,119 L/kg at a logKow of 8.
The Arnot-Gobas method as estimated in BCFBAF does take biotransformation into acount. The resulting BCF for a mid-trophic fish is 1730 L/kg wwt.

Key value for chemical safety assessment

Additional information

Cholesterol is the principal sterol synthesized by human and animal cells and is an essential component of cell membranes for normal cellular function. There is a strong mechanism regulating the balance between internal synthesized cholesterol and external cholesterol uptake. Furthermore, as cholesterol is the main precursor of vitamin D and of the steroid hormones, cholesterol is biotransformed into essential structures. Additionally, cholesterol is oxidized by the liver into a variety of bile acids. Most of these bile acids are reabsorbed from the intestines and the remainder is lost in the feces. Based on the different metabolism mechanisms and excretion of cholesterol in feces and urine, it is anticipated that cholesterol does not tend to bioaccumulate. The cholesterol homeostasis, achieved by a balance of uptake, biosynthesis, transport and excretion is shown in a publication of Yun et al. (2011) in section 6.1.2.

The REACH guidance on information requirements and chemical safety assessment Chapter R.7.10 describes some QSAR models based on a correlation between BCF and logKow. The modified Connell equation is a non-linear equation showing better performance for substances with a log Kow of 6 or higher than linear equations. The result is a high BCF of 25,119 L/kg at a logKow of 8. Based on the fact that cholesterol is widely distributed in organisms as essential component of cell membranes and that cholesterol may be metabolized to bile acids, steroid hormones and vitamine D and eliminated from the body via faeces and urine, it is anticipated that the modified Connell equation overestimates the BCF as no account is taken for the cholesterol homeostasis. The Arnot-Gobas method as estimated in BCFBAF (US EPA Episuite) does take biotransformation into acount. The resulting BCF for a mid-trophic fish is thus significantly lower, 1730 L/kg wwt.

As other mechanisms of homeostasis (incl. active transport, specific interactions with tissue components and uptake and depuration kinetics) are not accounted for in the calculated values, it is anticipated that the BCF will be even lower than the BCFBAF calculated value.

Furthermore, cholesterol is expected to be present in very low concentrations within the aquatic environment due to its hydrophobic character and its rapid biodegradation.

It is thus anticipated the that bioaccumulation potential of cholesterol in organisms is low. Furthermore, the outcome of the chemical safety assessment (section 13) does not lead to the need of further investigations into the bioaccumulation potential of cholesterol.

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