The most comprehensive assessment of selected antibiotics and hormones in 139 streams in 30 states was done between 1999 and 2000 by the U.S. Geological Survey. Samples were collected from streams draining agricultural and urbans areas. The antibiotics that were detected at parts per trillion concentrations in greater than 4% of the streams sampled were erythromycin, lincomycin, roxithromycin, sulfamethazine, sulfamethoxazole, trimethoprin, and tylosin. The naturally occurring hormones progesterone, testosterone, estradiol and their metabolites were detected in parts per trillion concentrations with frequencies of occurrence between 3 and 21%.
For more, see: US Geological Survey Fact Sheet FS-027-02
