Complex substances aquatic risk assessment (CSARA)
The CSARA project demonstrated that the use of alcohol ethoxylates in detergents is safe for the environment. The outcome of the research has been published in a special issue of Ecotoxicology and Environmental Safety (2006) as part of a series of seven publications1.
The CSARA project was set up to investigate the ecotoxicological risk assessment of the complex mixture of individual alcohol ethoxylate homologues that are contained in detergents. Alcohol ethoxylates [AEs] are a class of non-ionic surfactants used globally. A milestone for AE ecotoxicological risk assessment was achieved in the 1990s when an extensive review of the environmental safety of surfactants used in the Netherlands was performed (A.I.S.E. and CESIO, 1996, Limelette). The review was conducted jointly by governmental scientists (RIVM), regulators (VROM), trade associations (NVZ) and industry scientists. However, further work was still indicated for countries other than the Netherlands and a commitment to further work was taken by ERASM.
Applying a novel ecotoxicological risk assessment approach (the toxic unit method), it was concluded that for AE, even in a worst-case situation, the potential risk to the aquatic environments of Europe and North America is low.
The risk assessment consists of several elements:
- An analytical methodology for the determination of the full range of AE components in effluents in the same analysis was developed (“environmental fingerprint”). This approach has been deployed in European and Canadian effluent monitoring of biofilm and activated sludge waste water treatment plants [WWTPs] receiving predominantly municipal effluent. The environmental fingerprints indicate that the distribution of AE-homologues in WWTP-effluents differ from the distribution in commercial AE products with a relative increase in the proportion of fatty alcohol (AOH=AE with zero ethoxylation).?
- To determine the contribution of AE-derived AOH to the total concentration of AE and AOH in WWTP effluents, as well as the individual sorption behaviour and biodegradation rates, a laboratory continuous activated-sludge study [CAS] was conducted.
- Mixture toxicity theory was applied using a concentration addition of AE homologues in a species sensitivity distribution [SSD] context (toxic unit [TU] approach).
- An ecotoxicological risk assessment finally integrated effluent monitoring, fate analysis, and eco-toxicity. Effluent exposure and SSD results were included into a TU based model. Summed TUs using the SSD and environmental effluent fingerprints corrected for exposure, accounting for alcohol derived only from AE and for bioavailability due to sorption resulted in RCR<<1.