What is Dinoseb and Why Does It Matter?

Dinoseb is a herbicide that was widely used on crops like soybeans, beans, and fruit orchards before the EPA banned it in 1986. Despite that ban, it still shows up in drinking water today. That's because dinoseb binds to soil and can persist in groundwater for years — sometimes decades — after its last application. Old agricultural land, especially in states with a long farming history, continues to leach trace amounts into wells and surface water supplies.

Across the United States, 24 water systems have detected dinoseb in their supplies. The average level found is 0.126 parts per billion (ppb), with the highest recorded measurement reaching 0.8 ppb. While those numbers may sound small, they're worth paying attention to — especially for pregnant women and young children.

At higher exposure levels, dinoseb is known to interfere with the body's ability to produce energy at the cellular level. The EPA classifies it as a possible human carcinogen and has linked it to reproductive harm, including reduced fertility and developmental problems in fetuses. Animal studies show that even low-level exposure during pregnancy can affect fetal development (EPA). Dinoseb works by disrupting a process called oxidative phosphorylation — essentially, it interferes with how cells convert food into usable energy. Over time, that kind of disruption can affect multiple organ systems, including the thyroid and reproductive organs.

The EPA's legal limit for dinoseb in drinking water is 7 ppb. None of the 24 systems where dinoseb was detected exceeded that legal limit, which is reassuring on the surface. But the EWG (Environmental Working Group) sets its health guideline much lower — at 0.6 ppb — based on the most current reproductive and developmental toxicity research. By that standard, the highest detected level of 0.8 ppb does cross a meaningful health threshold. This gap between the legal limit and the health guideline reflects a common pattern: EPA standards often lag behind the latest science. The legal limit tells you what's allowed. The health guideline tells you what researchers believe is actually safe.

Geographically, Florida leads the country with 10 water systems detecting dinoseb — more than any other state. West Virginia follows with 5 systems, and New York, Pennsylvania, and South Carolina each appear on the list as well. Florida's warm climate and long history of intensive agriculture make it particularly vulnerable. Pesticides applied to citrus groves and vegetable farms over past decades have had plenty of time to migrate into the state's shallow aquifer systems. West Virginia's detections likely reflect older agricultural practices in rural areas where groundwater is the primary drinking source. New York and Pennsylvania share a similar story — farming regions with legacy pesticide use and aging infrastructure that doesn't always catch these trace compounds.

The good news is that dinoseb is removable. Activated carbon filtration — the kind found in many under-sink and whole-house filters — can reduce dinoseb levels significantly. Reverse osmosis (RO) filtration goes further, removing up to 99% of a wide range of pesticides and herbicides, including dinoseb. If you live in Florida, West Virginia, or another affected state — especially in a rural area served by a private well or a small water system — an RO system is one of the most reliable ways to protect your household. Echo Water's reverse osmosis systems are independently tested to NSF/ANSI standards, so you know exactly what they're removing. If you're unsure whether dinoseb is present in your water, you can request a Consumer Confidence Report from your utility or have your water tested by a certified lab. Knowledge is the first step — and clean water is a straightforward fix from there.

Regulatory Standards for Dinoseb

Cities With the Highest Dinoseb Levels

States Most Affected by Dinoseb

Frequently Asked Questions

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