What is Antimony* and Why Does It Matter?

Antimony is a naturally occurring metal found in the earth's crust, but it doesn't stay there on its own. Industrial activities push it into water supplies through mining operations, coal burning, and the manufacturing of flame retardants, batteries, and plastics. Old pipes and solder can also leach small amounts into drinking water over time. When antimony-containing waste seeps into soil, it eventually finds its way into groundwater — the source many communities rely on.

Right now, antimony shows up in 380 water systems across the United States. The average detected level is 0.276 parts per billion (ppb), which sounds small. But the maximum recorded level hits 4.05 ppb — well above what independent health researchers consider safe for long-term consumption.

At low levels, antimony exposure typically causes no immediate symptoms. Prolonged exposure is a different story. The EPA classifies antimony as a possible human carcinogen, meaning long-term ingestion may increase cancer risk over time. Animal studies have shown that ongoing antimony exposure can affect cholesterol levels, blood sugar, and heart function (EPA). Children and pregnant women face greater risk because their bodies are more sensitive to heavy metal accumulation. Even at levels that meet federal standards, the Environmental Working Group (EWG) warns that current regulations may not fully protect long-term health.

That gap between federal rules and health-based guidelines is worth understanding. The EPA sets the legal limit for antimony in drinking water at 6 ppb. The EWG's health guideline is significantly stricter — just 0.63 ppb. Of the 380 systems where antimony was detected, 6 exceeded the EWG guideline. That means those communities are drinking water that passes federal inspection but still falls into a range that health researchers flag as a concern. The EPA limit was last updated decades ago and doesn't fully reflect what newer research shows about low-level, long-term exposure. The EWG guideline is based on a one-in-a-million cancer risk threshold, which many public health scientists consider a more protective standard.

Geographically, antimony detections cluster in specific parts of the country. South Dakota leads with 91 affected systems, followed by West Virginia (56), Iowa (51), Minnesota (36), and Utah (23). That pattern isn't random. South Dakota and Utah have significant mining histories — antimony ore has been extracted in both states for over a century, leaving behind contaminated soil and groundwater. West Virginia's coal industry contributes through combustion byproducts that settle into waterways. Iowa and Minnesota detections likely reflect a combination of agricultural runoff, industrial activity, and naturally occurring antimony in regional geology. If you live in any of these states, it's worth checking your specific water system's annual quality report, also called a Consumer Confidence Report.

The good news is that antimony is one of the contaminants that home filtration handles well. Reverse osmosis (RO) filtration is the most effective method, removing up to 99% of antimony from tap water. RO systems work by pushing water through a semi-permeable membrane that blocks heavy metals, including antimony, at the molecular level. Activated alumina filters and certain ion exchange systems also reduce antimony levels, though not as consistently as RO. Standard carbon filters — like pitcher-style filters — are not designed to remove heavy metals and won't make a significant dent in antimony levels. Echo Water's reverse osmosis systems are specifically tested to address contaminants like antimony, giving you confidence in what actually reaches your glass. If you're in one of the higher-risk states or simply want to know what's in your water before acting, starting with a home water test is a smart first step.

Regulatory Standards for Antimony*

Cities With the Highest Antimony* Levels

States Most Affected by Antimony*

Frequently Asked Questions

Related Contaminant Guides