A new study has found that chemicals known to affect fertility and reproductive health are present in natural and drinking water supplies. Researchers have created a new tool to detect these substances. By analyzing samples from rivers, tap water, bottled water, rainwater, and storage tanks, they identified hormone-disrupting chemicals—specifically estrogen-like substances—present in many of the sources. The research, published in the journal iScience, highlights the widespread presence of these contaminants in the environment. Senior author Alison Heather, a professor at the University of Otago and chief scientific officer of a biotech startup called InsituGen, explains that these chemicals are linked to both ecological harm and human health issues, including declining fertility and reproductive health. "This doesn't mean all water is unsafe to drink, but it does show that detectable estrogen-like signals are present in many common water sources, while other sources are essentially free of such activity," Heather says. The findings underscore both the extent of environmental contamination and the possibility of obtaining cleaner, low-estrogenic water sources. For example, the study found strong estrogenic activity in some rivers, household tap water, certain storage tanks, and one brand of bottled water. In contrast, one spring, one filtered fountain, and one bottled product showed no detectable estrogenic activity. Heather emphasizes that current water monitoring methods typically test for only a small number of chemicals, but the new tool is an easy-to-use, sensitive bioassay that measures the concentration of estrogenic contaminants. Environmental samples often contain complex mixtures of natural hormones, pharmaceutical estrogens, pesticides, plasticizers, and other industrial chemicals. It is the combined biological effect of these mixtures that matters most, Heather explains. The new tool can help identify areas where the mixtures of endocrine-disrupting chemicals are highest, enabling public health regulators and water suppliers to take action to reduce exposure over time. While the study did not directly measure health outcomes, Heather says it reinforces the need to treat estrogenic endocrine-disrupting chemicals as a long-term ecological and public health issue.