Effects assessments for surfactants in sludge-amended soils: a literature review and perspectives for terrestrial risk assessment

Risk assessments have two components: an assessment of the potential environmental concentrations of a chemical, and an assessment of the environmental effects of the chemical. The fate of detergent surfactants has been well characterized during wastewater treatment. They are predominantly removed due to biodegradation, while a fraction is removed via sorption to sludge solids and may thus end up in the terrestrial environment. It is assumed that sorption to sludge solids and soil components will reduce bioavailability to terrestrial organisms. A review of the literature indicates that toxicity data for invertebrates and numerous higher plants are available for the anionic surfactant linear alkyl benzene sulfonate (LAS). Different modes of exposure (hydroponic medium, addition to irrigation water, spiked soil, spiked sludge) and types of soil significantly impact toxicity test results and must be taken into account when performing a risk assessment. The extrapolation of aquatic toxicity data to derive terrestrial PNECs (predicted no effect concentrations) will be discussed. The development of practical chronic testing, such as the rapid cycling Brassica plant life-cycle test, will be discussed in the context of the various tiered testing approaches currently being proposed by different regulatory agencies.