What is Bromate and Why Does It Matter?

Bromate is not something that exists naturally in your tap water. It forms during the treatment process itself — specifically when water suppliers use ozone (a powerful disinfectant) to kill bacteria and viruses, and that ozone reacts with naturally occurring bromide in the source water. Chlorination can also produce bromate as a byproduct. In other words, the very process designed to make your water safe can create a new problem.

The health concerns around bromate are serious. The International Agency for Research on Cancer classifies bromate as a possible human carcinogen. Animal studies show it causes kidney tumors, thyroid tumors, and mesothelioma — the cancer linked to asbestos exposure — at elevated doses (WHO). Even at lower levels, long-term exposure raises concern. The EWG sets its health guideline at just 0.1 parts per billion (ppb), based on a one-in-one-million cancer risk threshold. That number matters a lot when you look at what's actually showing up in tap water across the country.

The EPA's legal limit for bromate is 10 ppb — 100 times higher than what the EWG considers safe. This gap is not unusual in water regulation, but it is significant. Of the 165 water systems that detected bromate in recent testing, 152 of them — more than 92% — exceeded the EWG health guideline of 0.1 ppb. The average detected level was 1.548 ppb, or about 15 times above that guideline. One system recorded a peak of 18 ppb, nearly double the EPA's legal limit. Water utilities can report full compliance with federal law while still delivering water that exceeds health-based targets by a wide margin.

Geography plays a clear role in bromate exposure. California leads all states with 38 affected water systems, followed by Texas with 20 and Florida with 16. Kansas and New Jersey round out the top five, with 8 and 6 systems respectively. These states share a few things in common: large populations served by surface water sources (lakes, rivers, and reservoirs), higher natural bromide levels in those sources, and widespread use of ozone treatment at water plants. Coastal and agricultural states often have elevated bromide in their source water due to saltwater intrusion or runoff, which gives ozone more raw material to work with when bromate forms. Warmer climates can also intensify the chemical reaction that produces it.

The good news is that bromate is very effectively removed at the tap. A reverse osmosis (RO) system reduces bromate by up to 95% or more, making it one of the most reliable options for households in affected areas. Activated carbon filters alone are not enough — bromate does not bind well to carbon media. If you're in California, Texas, Florida, or another high-prevalence state, checking your local water utility's annual Consumer Confidence Report is a smart first step. That report will tell you whether bromate was detected and at what levels. Echo Water's reverse osmosis systems are designed specifically to target disinfection byproducts like bromate, along with dozens of other contaminants that standard filters miss. If your water tests high for bromate, an RO system installed under your kitchen sink gives you a reliable, daily layer of protection — especially important for children, pregnant women, and anyone with heightened health concerns.

Regulatory Standards for Bromate

Cities With the Highest Bromate Levels

States Most Affected by Bromate

Frequently Asked Questions

Related Contaminant Guides