The City of Chicago Department of Water Management (CDWM) is proud to provide high quality drinking water that exceeds all standards set by state and federal water quality regulators. Source water taken from Lake Michigan is filtered and treated at Chicago’s two water purification plants: the Jardine Water Purification Plant (JWPP) and the South Water Purification Plant (SWPP). Having completed the purification process, the finished (fully treated) drinking water is then distributed via pipelines to all of CDWM’s customers. The reader is encouraged to visit the City of Chicago website and read the annual water quality reports posted on the CDWM’s homepage.
The CDWM is currently performing a water quality study to monitor some compounds that have not historically been considered to be contaminants of concern, but have been recently documented at trace concentrations in our nation’s waterbodies. This study includes compounds known as Endocrine Disrupting Chemicals (EDCs) and Pharmaceuticals & Personal Care Products (PPCPs), which are considered to be emerging contaminants. EDCs are compounds with potential to interfere with natural hormone systems. PPCPs are a group of compounds consisting of prescription or over-the-counter therapeutic drugs, veterinary drugs, and consumer products such as sun-screen, lotions, insect repellent, and fragrances. The reader is encouraged to visit the United States Environmental Protection Agency (USEPA) website to learn more about EDCs (http://www.epa.gov/ncer/science/endocrine/) and PPCPs (http://www.epa.gov/ppcp/).
Most of the compounds classified as EDCs and PPCPs are not currently regulated – in other words, drinking water concentration limits have not been set for these compounds and water quality regulators do not require that drinking water providers test for these compounds. At this time, human health effects have not been demonstrated at the trace levels at which these unregulated compounds are being detected. Nevertheless, more research is being conducted on the presence and impacts of EDCs and PPCPs in our nation’s waters and on human health (studies are being conducted by groups such as the USEPA and the Water Research Foundation).
Advances in technology over the past several years now allow for the detection of compounds at extremely low concentrations. Modern laboratory tests can detect certain compounds down to levels of parts per trillion (ppt) or nanograms per liter (ng/L) concentrations. Typically, regulated compounds are measured in the range of parts per million (ppm) or milligrams/liter (mg/L). Since it is difficult to conceptualize a trillion of anything, the following example from The MegaPenny Project website (http://www.kokogiak.com/megapenny/) may help. It would take approximately 2.6 trillion pennies to fill the Willis Tower (formally known as the Sears Tower). One ppt (1 ng/L) would equal approximately 2.5 pennies within a solid Willis Tower made entirely of pennies!
In response to the growing interest and awareness in EDCs and PPCPs, and recognizing that emerging contaminant research studies may take years to complete, the City of Chicago developed a sampling program that encompasses both temporal and laboratory variability. The sampling program entails collecting Lake Michigan source water and finished drinking water samples six times over two years. Sampling sites include the offshore crib intakes, shore intakes, and finished water outlets at the JWPP and the SWPP, plus one field blank (42 total samples).
Since most of these compounds are not regulated, EDC and PPCP laboratory tests do not have standardized analyte lists, methods, or reporting limits. Therefore, CDWM decided to send samples to three independent laboratories with extensive experience doing EDC and PPCP analyses. This allows for the evaluation of intra-laboratory variability, inter-laboratory variability, and the seasonal patterns and levels of occurrence of a large number of EDCs and PPCPs. The three laboratories each use different analytical methods, have partially overlapping analyte lists, and claim a range of ppt reporting limits. By sending samples to multiple laboratories, it is possible to comment on both lab performance and the actual occurrence patterns of EDCs and PPCPs.
The following report summarizes the results of the study to date. Table A shows the results of the Lake Michigan source water samples (JWPP and SWPP crib and shore intakes) and the drinking water samples (finished water from JWPP and SWPP). Disagreements between laboratories for certain compounds and issues with laboratory quality control have called some of the results into question; Table B shows all of the data that have been flagged as “not trusted” or “questionable.” Both tables are considered to be working documents and will be updated as the study proceeds. Please refer to the footnotes at the bottom of the tables for additional information.
CDWM is happy to provide the consumers of Chicago’s drinking water with additional information about water quality. Please address any questions or concerns to 312-742-7499.