What is Aldicarb sulfoxide and Why Does It Matter?

Aldicarb Sulfoxide: What It Is and Why It Matters

Aldicarb sulfoxide is a pesticide byproduct that forms when aldicarb breaks down in soil and water. Aldicarb itself is one of the most toxic pesticides ever registered for use in the United States. Farmers have historically applied it to crops like potatoes, citrus, and cotton to kill insects and nematodes (tiny soil worms that damage roots). As aldicarb degrades, it transforms into aldicarb sulfoxide — and this breakdown product moves easily through soil into groundwater. From there, it can reach private wells and public water systems.

The health concerns with aldicarb sulfoxide center on its effect on the nervous system. It belongs to a class of chemicals called carbamates, which work by disrupting the enzyme that allows nerve signals to stop firing. In plain terms, it interferes with how your nerves communicate. At higher exposures, this can cause nausea, vomiting, muscle weakness, and in severe cases, seizures. The EPA classifies aldicarb as "very highly toxic" to humans. Children and pregnant women face greater risk because developing nervous systems are more sensitive to this kind of chemical interference. Even low-level, long-term exposure raises concern among researchers studying neurological development in children.

Currently, the EPA sets the legal limit for aldicarb sulfoxide in drinking water at 3 parts per billion (ppb). Across the 10 water systems where this contaminant has been detected, the average measured level is 0.286 ppb — well below that federal limit. The highest recorded level reached 0.567 ppb, also below the EPA threshold. That might sound reassuring, but it's worth understanding what "legal" means here. The EPA's legal limits are often set based on what's technically achievable to remove, not purely on what's safe. The Environmental Working Group (EWG) takes a stricter approach, recommending limits based on health-protective science rather than treatment feasibility. No current EWG health guideline exists specifically for aldicarb sulfoxide, but given its parent compound's extreme toxicity, many water quality experts treat any detectable level as worth monitoring closely.

Geographically, detections cluster in states with strong agricultural histories. New York and Kentucky each report 2 affected systems, followed by South Carolina, Georgia, and New Hampshire with 1 each. New York's Long Island region has dealt with aldicarb contamination in groundwater for decades — it was one of the first places in the country where widespread pesticide contamination of drinking water was confirmed, dating back to the 1970s. Kentucky and the Carolinas have significant farming operations where carbamate pesticides have seen historical use. New Hampshire's appearance on this list is less expected, but older agricultural land and shallow aquifers can hold chemical residues for many years after application stops. The EPA banned most uses of aldicarb in 2010, but contamination in groundwater can persist long after a pesticide is no longer applied.

The good news is that effective filtration options exist. Activated carbon filters can reduce aldicarb sulfoxide levels, but reverse osmosis (RO) systems offer the most reliable protection. A quality reverse osmosis system removes up to 99% of pesticide residues and their byproducts from your drinking water. If your home relies on a private well — especially in an agricultural area or a state on this list — testing your water annually is a smart first step. Echo Water's reverse osmosis systems are designed specifically for home use and can handle contaminants like aldicarb sulfoxide without complicated installation. If you're on a municipal system, you can request your utility's annual water quality report (called a Consumer Confidence Report) to see whether aldicarb sulfoxide has been detected in your supply. Knowing what's in your water is always the right place to start.

Regulatory Standards for Aldicarb sulfoxide

Cities With the Highest Aldicarb sulfoxide Levels

States Most Affected by Aldicarb sulfoxide

Frequently Asked Questions