Isothiazolinones are ubiquitous in our daily life; they are used as preservatives in cosmetics, household products and in building materials. These biocidal substances may be emitted inside house, inducing a potential risk for health, and released into the environment through wastewater or runoff, thus inducing a potential impact on aquatic ecosystems. The overall objective of this communication was to explore the isothiazolinone contamination of the continuum House-Sewer-River and to assess the induced risks for health and the aquatic life. The experimental results showed the ubiquity of isothiazolinones in indoor dust, urban water discharges and in the Seine River. Annual mass loads discharged into the Seine River were estimated using Monte Carlo method at both the conurbation and annual scales, they showed that wastewater discharges constitute the major entry pathway.