of NPSs in four rural communities in southern Illinois. Nine NPSs (carfentanil, furanyl fentanyl, methoxyacetyl fentanyl, MAB-CHMINACA, methcathinone, 4-methyl pentedrone, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MMMP), 1-(3-chlorophenyl) piperazine (mCPP), and 5-(2-Aminopropyl) Indole (5IT) were quantified. Methcathinone was the most frequently detected NPS (detection frequency, df = 100 %) followed closely by the MMMP and mCPP (df = 91%). The mass loading of methcathinone, mCPP, and 5-IT using ammoniacal nitrogen-based population were up to 21.1 ± 1.3 mg/d/1000 people, 15.0 ± 0.5 mg/d/1000 people, and 9.75 ± 2.72 mg/d/1000 people, respectively. This is the first study to determine the occurrence of NPSs including synthetic opioids, synthetic cannabinoids, synthetic cathinones