Nationwide reconnaissance of contaminants of emerging concern in source and treated drinking waters of the United States: Pharmaceuticals

Highlights

• 118 pharmaceuticals determined in drinking water samples from 25 U.S. treatment plants.

• Results demonstrate substantial reduction in concentration of many pharmaceuticals.

• Some pharmaceuticals persist through treatment and thus may result in human exposure.

• One of most comprehensive sets of pharmaceutical concentrations in drinking water.

• Results help to identify and prioritize specific pharmaceuticals for USEPA’s CCL.

Abstract

Mobile and persistent chemicals that are present in urban wastewater, such as pharmaceuticals, may survive on-site or municipal 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 a maximum of 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.

For both Phase I and Phase II campaigns, substantially fewer pharmaceuticals were detected in treated water samples than in corresponding source-water samples. Seven different pharmaceuticals were detected in all Phase I treated water samples, with a maximum of four detections in any one sample and a median of two pharmaceuticals for all samples. In Phase II a total of 26 different pharmaceuticals were detected in all treated water samples, with a maximum of 20 pharmaceuticals detected in any one sample and a median of 2 pharmaceuticals detected for all 25 samples. Source-water type influences the presence of pharmaceuticals in source and treated water. Treatment processes appear effective in reducing concentrations of most pharmaceuticals. Pharmaceuticals more consistently persisting through treatment include carbamazepine, bupropion, cotinine, metoprolol, and lithium. Pharmaceutical concentrations and compositions from this study provide an important base data set for further sublethal, long-term exposure assessments, and for understanding potential effects of these and other contaminants of emerging concern upon human and ecosystem health.

Introduction

Since the earliest reports of the widespread presence and distribution of pharmaceuticals and other contaminants of emerging concern (CECs) in surface water, groundwater, wastewater effluent, and other water resources (Kolpin et al., (2002); Stackelberg et al., 2004, Stackelberg et al., 2007, Benotti et al., 2009a, Boleda et al., 2011, Focazio et al., 2008, Gibs et al., 2007, Glassmeyer and Shoemaker, 2005, Glassmeyer et al., 2005, Kostich et al., 2014, Richardson and Ternes, 2011), the presence and distribution of CECs in water supplies, and potential consumer exposure to these CECs in drinking water, has been of substantial scientific and public interest. Bruce et al. (2010) concluded that exposure through drinking water is likely to be a common route of exposure for many human populations even though it is likely a less important route of exposure when compared to direct exposure through normal or routine use of prescription and over-the-counter drugs, which provide substantially larger doses of the active pharmaceutical ingredient than consumption of drinking water. A comprehensive assessment of the widest range of CEC classes and types, including but not limited to pharmaceuticals, is necessary to more fully document and clarify the potential for exposure to mixtures of pharmaceuticals and other contaminants of emerging concern in drinking water.

Between October 2007 and March 2012, the U.S. Environmental Protection Agency (USEPA) and the U.S. Geological Survey (USGS) conducted a joint, two-phase sampling study of CECs in source and treated drinking waters in the United States. In Phase I, source and treated water samples from nine drinking water treatment plants (DWTPs) were analyzed for 24 pharmaceuticals, reflecting a wide range of therapeutic uses (Table 1). The Phase I study allowed assessment of the potential compositions and the range of expected concentrations of CECs present in these water types, tested a centrally administered sampling design and quality assurance/quality control (QA/QC) protocol, and allowed evaluation of how well the complex sample collection protocol could be carried out by DWTP plant personnel without prior experience in collecting samples for CEC analysis.

The success of Phase I resulted in an expanded Phase II, wherein 25 DTWPs from throughout the United States (including five of the nine plants [DWTPs 1–5] from Phase I) were sampled to more comprehensively assess the possible presence and distribution of a substantially wider range of CECs in water supplies used for human consumption. About three years passed between Phase I (2007) and Phase II (2010) sampling campaigns. In Phase II, the QC protocol was refined and expanded, and the categories of analytes determined also were substantially expanded to include a wider array of pharmaceuticals, perfluorinated chemicals, estrogenic hormones, inorganic elements, bacteria, viruses, and estrogenicity (as determined by bioassay), as well as all pharmaceuticals measured in Phase I (Table 2).

The DWTPs sampled in both phases of this study included surface- and groundwater sources, represented a range of geographic locations within the United States, included most common treatment practices, and spanned a range of sizes. Each plant was sampled prior to and after treatment, and sample collection was timed to the hydraulic residence time of the DWTP to determine the relative reduction of CECs during treatment. Comprehensive QA/QC designs were used to assess bias and variability of CEC determinations at environmental concentrations.

This paper is one in a series describing the presence, persistence, and concentrations of CECs and microorganisms in source and treated drinking waters of the United States. This project, a joint effort of the USEPA and the USGS, is part of a long-term interagency agreement. A primary goal of this study is to provide accurate, objective data to assess the potential for human exposure to these CECs by consuming drinking water. A secondary goal is to estimate reduction, if any, of CECs from source waters by currently used drinking water treatment processes under conventional plant operating conditions, and thus identify possible candidate compounds or microorganisms that may be amenable to enhanced reduction or removal. An overview of this comprehensive national study is provided in Glassmeyer et al. (2016); the reader is encouraged to read this paper to understand the overall project design, population and treatment characteristics of the DWTPs studied, QA/QC and sample collection design applied to all samples, and how the results described in this paper fit into the overall objectives of this larger study. This paper describes the presence and ambient concentrations of pharmaceuticals in source and treated waters in the two phases of the study (Phase I, 24 pharmaceuticals; Phase II 118 pharmaceuticals). We also assess concentration reduction between source water intake and treated water production by comparing concentrations from samples for which DWTP residence time had been accounted for in the timing of sample collection.