**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** RECYCLING WASTEWATER AS A NONTRADITIONAL SOURCE FOR CROP IRRIGATION IS HELPING TO MEET FUTURE WATER DEMANDS, BUT ALSO RAISES POTENTIAL HUMAN HEALTH CONCERNS, INCLUDING FROM CHEMICALS OF ENVIRONMENTAL CONCERN (CECS). DIRECT CONJUGATION REACTIONS, WHEREIN CECS TAKEN UP INTO PLANTS ARE JOINED WITH ANOTHER MOLECULE BUT DO NOT DEGRADE THE CORE CHEMICAL STRUCTURE, CAN IMPACT FATE, BIOACCESSIBILITY, AND POSSIBLE BIOACTIVITY OF CECS. POTENTIAL FOR CONJUGATED CECS TO BACK-TRANSFORM TO PARENT COMPOUNDS HAS ONLY RECENTLY BEEN RAISED, AND OUR DISCOVERIES WERE THE FIRST TO DEMONSTRATE PLANT EXCRETION OF CONJUGATED CONTAMINANTS. THE OVERALL OBJECTIVE FOR THIS PROPOSAL IS TO DETERMINE THE BIOACCESSIBILITY, FATE, AND FORMATION OF CONJUGATED CEC METABOLITES IN PLANTS, USING REPRESENTATIVE COMPOUNDS. OUR CENTRAL HYPOTHESIS, FORMULATED ON OUR STRONG PRELIMINARY DATA, IS THAT DIRECT IN-PLANT CONJUGATION REACTIONS, WHICH DEPEND ON COMPOUND STRUCTURE, ALTER CEC BIOAVAILABILITY TO CONSUMERS AND CAN UNDERGO SUBSEQUENT BACK-TRANSFORMATION BY BACTERIA IN THE GUT. THE PROJECT SPECIFIC AIMS ARE TO: (1) DETERMINE BIOACCESSIBILITY OF CONJUGATED CEC PLANT METABOLITES IN THE MAMMALIAN GUT, (2) QUANTIFY PRODUCT-TO-PARENT REVERSION OF PLANT-EXCRETED CONJUGATED CEC METABOLITES, (3) RELATE CEC CHEMICAL STRUCTURE TO PROPENSITY FOR DIRECT IN-PLANT CONJUGATION. A MECHANISTIC DETERMINATION OF CONJUGATED CEC METABOLITE FORMATION, BIOACCESSIBILITY, AND REVERSION POTENTIAL WILL PROVIDE NEW OPPORTUNITIES FOR IMPROVING THE SAFETY AND RESILIENCE OF WATER RECYCLING USING NONTRADITIONAL SOURCES. THESE OUTCOMES WILL VERTICALLY ADVANCE FOUNDATIONAL KNOWLEDGE OF PLANT METABOLISM AND BIOAVAILABILITY TO POSITIVELY IMPACT INFORMED WATER REUSE SUSTAINABILITY IN AGROECOSYSTEMS, THEREBY INCREASING WATER AND FOOD SECURITY. RESULTS WILL BE COMMUNICATED TO SCIENTIFIC PEERS, STAKEHOLDERS AND THE PUBLIC.