Glass-bottled drinking water: a time capsule to study the historic presence of hazardous chemicals using effect-based methods

Background Contamination 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. Results Samples 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. Conclusions This 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