The original PNAS paper referenced in the Guardian article is open access: https://www.pnas.org/content/119/8/e2113947119 https://www.pnas.org/content/119/8/e21

The original PNAS paper referenced in the Guardian article is open access: https://www.pnas.org/content/119/8/e2113947119 https://www.pnas.org/content/119/8/e2113947119 Some brief highlights for readers wondering about significance: - Most rivers have one or more compounds above detection limits. About 26% have one or more compounds above PNEC [1] levels. - The most commonly detected compounds (caffeine, metformin, carbamazepine) were not commonly detected above PNEC levels. - The compounds most often detected above PNEC levels are sulfamethoxazole (antimicrobial), propranolol (β-blocker), loratadine (antihistamine), amitriptyline (antidepressant), citalopram (antidepressant), fexofenadine (antihistamine), verapamil (Ca channel blocker), and ketotifen (antihistamine). - The worst affected areas were middle income countries. The authors hypothesize that these are regions where populations can broadly afford pharmaceuticals but where sewage treatment systems lag behind those of high income countries. [1] Predicted No-Effect Concentration (PNEC) is the concentration of a substance in any environment below which adverse effects will most likely not occur during long term or short term exposure.