Aldicarb sulfoxide in Drinking Water: Complete Guide (2026)

What is Aldicarb sulfoxide and Why Does It Matter?

ALDICARB SULFOXIDE IN YOUR TAP WATER: WHAT YOU NEED TO KNOW

What Is Aldicarb Sulfoxide and Where Does It Come From?

Aldicarb sulfoxide is a breakdown product of aldicarb, a pesticide once widely used on crops like potatoes, cotton, and citrus fruits. When aldicarb breaks down in soil and groundwater, it transforms into aldicarb sulfoxide — sometimes called a metabolite. This compound doesn't stay put. It leaches into groundwater supplies, particularly in agricultural regions where the original pesticide was heavily applied. Though the EPA restricted aldicarb use starting in 2001, the chemical persists in soil and water for years. Groundwater moves slowly, so contamination from decades-old pesticide applications still shows up in wells today.

Our analysis found aldicarb sulfoxide in 12 water systems across the United States, with levels ranging from 0.303 to 0.567 parts per billion (ppb). No systems exceeded current EPA guidelines, but the presence of this chemical in drinking water deserves attention.

Health Effects: What the Research Shows

Aldicarb is a cholinesterase inhibitor, meaning it disrupts an enzyme your body needs for normal nerve function. Short-term exposure to high levels can cause headaches, nausea, blurred vision, and muscle weakness. Chronic exposure — drinking contaminated water over months or years — raises different concerns. Animal studies suggest potential effects on the nervous system and reproductive health at elevated doses, according to EPA toxicology reviews. Children may be more sensitive to these effects because their bodies are still developing and they drink more water per pound of body weight than adults.

The good news: the levels detected in the 12 affected water systems are low. However, the EPA and environmental health advocates argue there's no safe threshold for pesticide metabolites in drinking water. Even at current levels, some researchers recommend minimizing exposure when possible.

Regulatory Standards: EPA Limits vs. Health Guidelines

The EPA set a Maximum Contaminant Level (MCL) of 0.03 ppb for aldicarb itself, but aldicarb sulfoxide has a higher limit of 1.1 ppb. This distinction matters: the metabolite is considered slightly less toxic than the parent compound, so regulators allow higher concentrations. All 12 systems with detected aldicarb sulfoxide stayed below 1.1 ppb, keeping them compliant with federal law.

The Environmental Working Group (EWG), which sets stricter health-based guidelines, recommends 0.003 ppb for aldicarb sulfoxide — about 367 times lower than the EPA limit. This gap reflects a philosophical difference: the EPA sets limits based on what's economically feasible to treat, while the EWG prioritizes health protection. The maximum level we detected (0.567 ppb) exceeds the EWG guideline by 189 times, highlighting why some families choose additional filtration even when their water meets EPA standards.

Where Aldicarb Sulfoxide Appears Most Often

Kentucky leads with 4 affected systems, followed by New York with 2 systems. Single detections appeared in South Carolina, Georgia, and New Hampshire. This pattern reflects agricultural history. Kentucky and the Carolinas grew cotton heavily during aldicarb's peak use. New York's potato farming regions relied on the pesticide for decades. These states' groundwater-dependent communities remain vulnerable because the chemical moves slowly through soil layers, persisting long after application stopped.

Removing Aldicarb Sulfoxide From Your Water

If your water system detected aldicarb sulfoxide, several filtration methods work effectively. Activated carbon filters remove this pesticide metabolite efficiently, particularly when used in point-of-use systems like pitcher filters or under-sink models. For comprehensive protection, reverse osmosis systems eliminate up to 99.9% of aldicarb sulfoxide along with other pesticide residues. Whole-house systems using granular activated carbon (GAC) treat all water entering your home, protecting your family at every tap.

Request a water quality report from your local utility to see if aldicarb sulfoxide appears in your system. If it does — or if you prefer an extra layer of protection — Echo Water's testing can identify what's in your specific tap water and recommend the right filtration solution for your home.

Regulatory Standards for Aldicarb sulfoxide

Cities With the Highest Aldicarb sulfoxide Levels

States Most Affected by Aldicarb sulfoxide

Frequently Asked Questions