Mobile and persistent chemicals that are present in urban wastewater, such as pharmaceuticals, may survive
on-site ormunicipal wastewater treatment and post-discharge environmental processes. These pharmaceuticals
have the potential to reach surface and groundwaters, essential drinking-water sources. A joint, two-phase U.S.
Geological Survey-U.S. Environmental Protection Agency study examined source and treated waters from 25
drinking-water treatment plants from across the United States. Treatment plants that had probable wastewater
inputs to their source waters were selected to assess the prevalence of pharmaceuticals in such source waters,
and to identify which pharmaceuticals persist through drinking-water treatment. All samples were analyzed
for 24 pharmaceuticals in Phase I and for 118 in Phase II.
In Phase I, 11 pharmaceuticals were detected in all source-water samples, with amaximumof nine pharmaceuticals
detected in any one sample. The median number of pharmaceuticals for all 25 samples was five.
Quantifiable pharmaceutical detections were fewer, with a maximum of five pharmaceuticals in any one
sample and a median for all samples of two. In Phase II, 47 different pharmaceuticals were detected in all
source-water samples, with a maximum of 41 pharmaceuticals detected in any one sample. The median
number of pharmaceuticals for all 25 samples was eight. For 37 quantifiable pharmaceuticals in Phase II,
median concentrations in source water were below 113 ng/L.