Trimethoprim
Cities measured
87
Detected in
87 / 87
Highest
0.048 μg/L — Delhi
Overview
Trimethoprim is an antibiotic commonly used for urinary tract infections (UTIs), often combined with sulfamethoxazole. It is one of the most frequently detected antibiotics in European surface and drinking waters and is persistent under UV and biological degradation.
Health Relevance
Primary concern is AMR selection — at ng/L concentrations, trimethoprim promotes dihydrofolate reductase resistance genes in environmental bacterial communities.
Regulatory Limits
Drinking Water Directive 2020/2184
No EU regulatory limit.
Controversy & Contested Science
Trimethoprim resistance in E. coli UTI strains has increased dramatically across Europe — to the point where trimethoprim monotherapy is no longer recommended as first-line UTI treatment in many countries. A 2019 Lancet Infectious Diseases study found trimethoprim resistance in community-acquired E. coli UTIs correlated geographically with river trimethoprim concentrations — a disturbing direct linkage between environmental antibiotic pollution and clinical resistance patterns.