A new approach to estimate concentrations of alcohol ethoxylate in rivers in Japan for screening-level risk assessment

Alcohol ethoxylate (AE) is a widely used household detergent that is ubiquitous in aquatic environments. To assess and manage the risk of AE, its environmental exposure concentrations must be evaluated in rivers nationwide; however, very few AE monitoring data are currently available. Furthermore, developing a rigorous exposure model that would cover rivers nationwide would require a great deal of time, human resources, and money. We developed a new approach to estimate AE concentrations in rivers throughout Japan for screening-level risk assessment. In this approach, five-day biochemical oxygen demand (BOD5) data were used as a surrogate indicator of the AE concentration in river water. The Tama and Nikko Rivers were ranked according to their BOD5 data, and the AE concentrations of the Nikko River were then estimated using the Standardized Hydrology-based Assessment tool for chemical Exposure Load (AIST-SHANEL) model. For each river, the concentrations of AE in its waters were projected based on that river's reported BOD5 values, its ranking, the approximation formula for AE and BOD5, and estimated AE concentrations in water of the Nikko River from the model. The accuracy of the projected values was validated by comparing the projected AE concentrations in water from the Tama River with its monitoring data. There are various technical uncertainties associated with this approach; however, our results suggest that this new approach can be applied in screening-level exposure assessment of other chemical substances that have properties similar to AE.