Estimation of the Contribution Made to Down-the-Drain Emissions of D5 by Personal Care Product Categories in the European Union

Aquatic risk assessment of personal care chemicals requires quantifying the contribution of all product types containing these ingredients to down-the-drain emissions. We developed a probabilistic model framework embracing stochastic variability associated with individual consumers and their behaviors in the European Union, as well as other sources of uncertainty related to losses following applications (e.g., volatilization). The model was applied to decamethylcyclopentasoloxane (D5), an emollient used in wash-off (WO) and leave-on (LO) products. Quantifying contributions from each product category containing D5 to down-the-drain emissions is necessary to inform optimal risk management options. Simulation results for the baseline scenario in 2012 support the argument that LO products make up a minor contribution (7.1%) to down-the-drain emissions of D5, with only 0.20% of the D5 used in LO products being released to wastewater. The most influential model parameters are the release factor from WO products and the time between application and use for various LO product types, stressing the importance of embracing stochastic variability across individuals' behavior when assessing contributions of various product types to environmental emissions. The downward trend in WO use from 2010 to 2016 is reflected in declining concentrations in wastewater influent during the same period. Uncertainty remains about future levels of D5, once phasing out WO products is complete. The probabilistic model in conjunction with high-tier data of consumer habits is a promising high-tier tool for the characterization of complex emission scenarios of personal care ingredients. Integr Environ Assess Manag 2019;00:1-12. © 2019 SETAC.