1. to determine the concentrations of 8 target PPCPs (acetaminophen, ampicillin, caffeine, metformin, naproxen, sulfamethoxazole, triclosan, and trimethoprim) and an additional 10 analytes in raw and treated drinking water from Lake Erie;
2. to evaluate whether the enzyme-linked immunosorbent assay (ELISA) is an effective method for screening and characterizing PPCPs in drinking water; and
3. to quantify the human health risks from exposure to trace levels of PPCPs in drinking water from Lake Erie.
To achieve the first objective, raw and treated water samples were collected from the Wasielewski Water Treatment Plant in Erie, Pennsylvania between October 2016 and August 2017. Along with grab samples, long-term samples were collected using Polar Organic Chemical Integrative Samplers (POCIS). Samples were analyzed by liquid chromatography- mass spectroscopy (LC-MS-MS) by an accredited laboratory. For short-term samples, six of the 18 PPCPs were found at detectable levels in raw or treated drinking water including atrazine, bisphenol-A, caffeine, ibuprofen, metformin and simazine. In the majority of cases, analyte levels in treated water were lower compared to raw water samples. For long-term samples, an additional four PPCPs (ten total) were found at detectable levels including gemfibrozil, naproxen, sulfamethoxazole and trimethoprim. Aqueous phase concentrations of PPCPs were estimated using sampling rates, deployment periods and analytical results of POCIS samplers. Similar to the grab sample results, the concentration of all analytes in treated water were lower than those in raw water samples.
A method comparison study was conducted to assess the agreement between the ELISA test with that of LC-MS-MS for three analytes (atrazine, caffeine and triclosan). Spiked samples in triplicate were prepared from certified standards to include concentrations of 0, 0.25, 0.5, 1.0 and 2.5 ng/mL. The spiked samples were split and analyzed separately using each method. Analyte concentrations from each method were compared using Pearson product moment correlations and the construction of Bland-Altman plots. Results across all three analytes showed a moderate to high level of agreement between the two analytical methods. The correlation coefficient (r) ranged between 0.96 and 0.99. The highest level of agreement was observed with atrazine, followed by caffeine and triclosan, respectively.
The third objective was to calculate the human health risks from the PPCP concentrations found in treated water samples. A literature review was conducted to find sources of average daily intake (ADI) or reference dose (RfD) values needed to calculate a drinking water exposure level (DWEL) for each analyte. The value of the DWEL was then compared to the maximum measured value or the method detection limit for each of the 18 analytes to estimate the risk quotient (RQ). A cumulative RQ was estimated at 0.003 for the 18 PPCPs included in this study. This level is well below any level considered to pose a risk. A value approaching 1 would be considered significant.
The major public health finding was that the 18 PPCPs quantified in this study were found at trace or non-detect levels and estimated to pose an insignificant health risk to the community. Additional findings include that the long-term POCIS and ELISA methods were practical and appropriate for measuring trace levels of PPCPs in source and treated water.