What is 4-Androstene-3,17-dione and Why Does It Matter?

4-Androstene-3,17-dione (commonly called androstenedione) is a naturally occurring steroid hormone. Your body produces it as a stepping stone to making testosterone and estrogen. So why is it showing up in tap water? The answer comes down to how our water systems handle waste. When humans and animals excrete hormones, those compounds travel through sewage and agricultural runoff into rivers, lakes, and groundwater. Wastewater treatment plants weren't designed to remove hormones, so androstenedione passes through and enters drinking water sources. Livestock operations are a particularly significant source — large animal farms generate enormous volumes of hormone-rich waste that can leach into nearby waterways.

The health effects of androstenedione in drinking water are still being studied, but researchers have reason for concern. As a hormone — specifically an androgen — it can interfere with the body's endocrine system (the network of glands that regulates growth, metabolism, and reproduction). Even at low concentrations, hormones can act as endocrine disruptors. Children and pregnant women are considered most vulnerable because their hormone systems are either still developing or working to support a pregnancy. The Environmental Working Group (EWG) flags androstenedione as a compound of concern precisely because small hormonal shifts during critical developmental windows can have lasting effects. Long-term exposure studies on humans are limited, but animal research shows reproductive and developmental disruption at low levels.

Currently, the EPA has not set a legal limit for androstenedione in drinking water. That means water utilities are not required to remove it or even report it at specific thresholds. The EWG has not yet established a formal health guideline for this compound either. What we do know from the data: androstenedione was detected in 67 water systems across the United States. The average level found was 0.159 parts per trillion (ppt), with a peak detection of 1.12 ppt. While those numbers sound tiny, the key issue with hormones is that "tiny" doesn't always mean "harmless." Hormones operate at parts-per-trillion concentrations inside your body naturally — meaning water-borne hormones at similar levels are biologically relevant.

Geographically, California leads with detections in 10 water systems, followed by Illinois (9), Michigan (6), Iowa (4), and Pennsylvania (4). That pattern isn't random. California and the Midwest are home to large-scale agriculture and concentrated animal feeding operations (CAFOs). Iowa, in particular, has one of the highest densities of livestock operations in the country. When it rains, runoff from these facilities carries hormones into rivers and reservoirs that supply drinking water. Illinois and Michigan sit within the Great Lakes watershed, which receives agricultural runoff from multiple states. Pennsylvania's detections likely reflect a mix of farming activity and older wastewater infrastructure in some communities.

The good news: effective filtration options exist. Reverse osmosis (RO) filtration is the most reliable method for removing hormones like androstenedione from tap water. RO systems push water through an extremely fine membrane that blocks contaminants at the molecular level, removing up to 99% of many hormone compounds. Activated carbon filters — especially high-quality carbon block filters — also show meaningful reduction of steroid hormones, though not as completely as reverse osmosis. A whole-home system protects every tap, but a dedicated under-sink RO unit is a practical starting point for drinking and cooking water. Echo Water's reverse osmosis systems are designed specifically to address contaminants like these that standard municipal treatment misses. If you're in California, Illinois, Michigan, Iowa, or Pennsylvania, checking your local water quality report and pairing it with a quality filter is a smart, straightforward step toward protecting your family.

Regulatory Standards for 4-Androstene-3,17-dione

Cities With the Highest 4-Androstene-3,17-dione Levels

States Most Affected by 4-Androstene-3,17-dione

Frequently Asked Questions

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