Alcohols, C12-15-branched and linear

Endpoint summary

Additional information

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

There is very substantial and convincing evidence in support of rapid and complete biodegradation / biotransformation by a range of organisms (bacteria, fungi, algae, fish and mammals) and in a range of environmental media and conditions (particularly aquatic and water/sediment systems) for members of the C6-24 Alcohols category.

Estimated data

Predicted data from the SRC BIOWIN v4.10 program (part of the EPIWeb suite v4.01) supports rapid degradation for the linear alcohols, but cannot be used quantitatively. However, the extent of measured data means that it is not necessary to rely upon any form of (Q)SAR: interpolation to fit data gaps can be done by expert judgement across the data set.

Measured data

A range of screening and simulation data with different types of cultures is available and discussed in this section. The data consistently show that linear and essentially linear aliphatic alcohols in the range C6 - C24 are readily biodegradable in standard screening studies, rapidly and extensively biodegraded under aerobic and anaerobic conditions, biodegradable by garden soil inoculum, biodegraded by algae and aquatic microorganisms in long-term aquatic ecotoxicity tests, and biodegraded in sediments in several studies.

Biodegradation under anaerobic conditions

The anaerobic biodegradability of a range of chain lengths within the category has been investigated (C8 and C16 alcohols, 2 studies; and C16-18 and C18 unsaturated alcohols, 2 studies). All test substances were anaerobically degradable.

Biodegradation by algae

Rapid degradation in water is indicated by the difficulties encountered in aquatic toxicity tests (chronic Daphnia reproduction) for long chain aliphatic alcohols (Section 6.1.4). Alcohols in the range C10-C15 were found to be rapidly removed from the test medium. This was attributed to metabolism by algae present as a food source in tests, and in later stages of the 21-day tests to bacterial degradation by microbes adsorbed onto the carapace of the test daphnids, despite daily cleaning of the animals.

Natural occurrence

It is important for context to note the findings from studies in the EU and US which consistently show that anthropogenic alcohols in the environment are minimal compared to the level of natural occurrence. Using stable isotope signatures of fatty alcohols in a wide variety of household products and in environmental matrices sampled from river catchments in the United States and United Kingdom, Mudge et al. (2012) estimated that 1% or less of fatty alcohols in rivers are from waste water treatment plant (WWTP) effluents, 15% is from in situ production (by algae and bacteria), and 84% is of terrestrial origin. Further, the fatty alcohols discharged from the WWTP are not the original fatty alcohols found in the influent. While the compounds might have the same chain lengths, they have different stable isotopic signatures (Mudge et al., 2012).

In conclusion, the environmental impact of these studies is that it has confirmed that the fatty alcohols entering a sewage treatment plant (as influent) are partly derived from detergents, but these are not the same alcohols as those in the effluent which arise from in-situ bacterial synthesis. In turn, 99% or more of the fatty alcohols found in sediments near the outfall of the WWTP are derived from natural synthesis and are not the same alcohols as those in the effluent.