Potential for anaerobic biodegradability in marine and freshwater of Linear Alkylbenzene Sulphonates (LAS)

SCHEER WG on Anaerobic Biodegradation of Linear Alkylbenzene Sulphonates (LAS)
SCHEER members: Marco Vighi (Chair), Rodica Ion, Marian Scott, Pim de Voogt (Rapporteur)
External expert: Jan Linders
Contact:SANTE-C2-SCHEERec [dot] europa [dot] eu (SANTE-C2-SCHEER[at]ec[dot]europa[dot]eu)
On request from: European Commission
Adopted on: 18 June 2020

In agreement with the main conclusions of the study, it is the opinion of the SCHEER that the potential for anaerobic degradation of LAS is negligible in freshwaters and may occur in marine waters only under particular conditions.

It is also the opinion of the SCHEER that the conditions in which some anaerobic degradation has been observed (sandy sediments and low organic carbon content) may be atypical for sites impacted by wastewater, where muddy and organic sediments may be encountered more frequently.

These opinions are supported by an overall assessment of a moderate weight of evidence: good evidence from a primary line of evidence but evidence from several other lines is missing (important data gaps).

However, it is the opinion of the SCHEER that the Cadiz study presents some limitations and weaknesses. In particular:

• SPC amounts are not reported in the mass balance and no explanations are provided for that.
• The results of the degradation experiments are only reported in figures (e.g., Figs. 10, 14, etc.), not in numeric tables. Therefore, to perform additional statistical assessments or calculations, approximated values derived from the figures had to be used.
• There are improvements needed in both the statistical analysis performed and the reporting of the results.
• The reference quoted to support the low toxicity of SPCs is not appropriate.
• In Figs. 8 and 9, the title of the Y-axis is wrong; it is not “log Kd”, it is “Kd”, the scale of the axis is logarithmic.

Despite these flaws, it is the opinion of the SCHEER that the methodology was applied correctly, according to OECD 308 Guideline, and that the results obtained may be considered reliable.

Considering that LAS are compounds produced in very high volumes and continuously emitted in sites impacted by wastewater, it is the opinion of the SCHEER that the negligible anaerobic degradation in freshwaters and degradation in marine waters only under certain conditions may be a problem of relevant environmental concern. It must be also considered that estuarine and coastal environments are among the most productive yet sensitive ecosystems on earth; hence, exposures can have significant environmental implications.

Keywords:

anionic surfactants, persistence, sorption, biodegradation, marine, freshwater, sediment, wastewater, high production volume chemical

Opinion to be cited as:

SCHEER (Scientific Committee on Health, Environmental and Emerging Risks), final Opinion on the potential for anaerobic biodegradability in marine and freshwater of Linear Alkylbenzene Sulphonates (LAS), 18 June 2020.