Abstract
BackgroundContamination of drinking water by hazardous chemicals can be associated with human health risks. Recent studies using effect-based in vitro methods have demonstrated that a large part of the observed toxic effects are caused by unknown chemicals. In this study, we have used a panel of effect-based methods to study the presence of chemical contaminants in a unique material; glass-bottled Swedish tap water collected during the 1990s. These water samples were compared to drinking water from the same source waters and drinking water facilities, yet collected about 25 years later, in 2020.ResultsSamples were concentrated by solid phase extraction and evaluated for the following activities; estrogen receptor activity, androgen receptor activity, antiandrogenic activity, aryl hydrocarbon receptor activity, and oxidative stress response. We observed aryl hydrocarbon receptor activities in almost all studied samples and estrogen receptor activity in three out of ten studied samples. No activities were observed for androgen receptor activity, antiandrogenic activity or oxidative stress response. In general, observed activities were more frequent and higher in the water samples collected during the 1990s as compared to the corresponding samples collected in 2020.ConclusionsThis study demonstrates that it is possible to conduct an effect-based evaluation of the presence of hazardous chemicals in drinking water, with as small starting volume as 330 mL, by using miniaturized bioassays. Further, by comparing the glass-bottled water samples with newly collected water samples from the same drinking water treatment facilities, our results indicate that the presence of aryl hydrocarbon receptor and estrogen receptor activating compounds in the drinking water has decreased over the approximately quarter of a century that is separating the two sampling occasions. This difference could be due to improved raw water quality and/or improved treatment efficiency in the treatment plants.
Highlights
Contamination of drinking water by hazardous chemicals can be associated with human health risks
Estrogen receptor activity Initially, the concentrated water samples were tested for cytotoxicity in the stably transfected T47D cell line using MTS test at relative enrichment factor (REF) 50
Aryl hydrocarbon receptor activity Initially, the concentrated water samples were tested for cytotoxicity in the stably transfected DR-EcoScreen cell line using MTS test at REF 50
Summary
Contamination of drinking water by hazardous chemicals can be associated with human health risks. There is, a substantial body of scientific literature showing that these well-known environmental pollutants can only explain a relatively small proportion of the observed toxicity in water samples, especially for toxicity endpoints such as reactive toxicity, xenobiotic metabolism and oxidative stress [3,4,5,6,7] For some of these endpoints, the well-known environmental pollutants can only explain as little as 0.1–5% of the observed toxicity, implying that up to 99.9% of the toxicity is caused by unknown chemicals or mixture effects [3, 4]. Oskarsson et al [9] recently reported the that the drinking water was contaminated by oxidative stress inducing and antiandrogenic compounds during the drinking water treatment process in a Swedish drinking water treatment plant, while all the chemical parameters were acceptable according to the current legislation This highlights the need for effect-based methods in drinking water quality control
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