1,3-Dichloropropane in Drinking Water: Complete Guide (2026)

What is 1,3-Dichloropropane and Why Does It Matter?

# 1,3-Dichloropropane: What You Need to Know

## What It Is and Where It Comes From

1,3-Dichloropropane (1,3-DCP) is a synthetic chemical used primarily as a soil fumigant in agricultural applications. Farmers spray it on fields to kill nematodes—microscopic worms that damage crop roots—before planting. Once applied, this chemical doesn't stay in the soil. It leaches downward into groundwater, where it can persist for decades. Because groundwater feeds many municipal water supplies, especially in agricultural regions, 1,3-DCP occasionally shows up in tap water. Industrial manufacturing and dry cleaning operations can also release it into the environment, though agricultural use accounts for the majority of contamination.

The chemical is volatile, meaning it evaporates easily. However, in groundwater where oxygen is limited, it breaks down very slowly. This persistence is why even small amounts detected today signal past or ongoing exposure risks for communities relying on contaminated groundwater sources.

## Health Effects and Exposure Risks

The EPA has not set a federal drinking water standard for 1,3-DCP, which means there's no legal limit water utilities must follow. However, the Environmental Working Group (EWG), which evaluates health risks more conservatively than the EPA, recommends a guideline of 0.3 ppb (parts per billion). This guideline is based on animal studies showing that 1,3-DCP causes cancer in rats and mice at relatively low doses.

Current data shows 25 water systems across the country contain detectable levels of 1,3-DCP, with amounts ranging from trace levels up to 0.5 ppb. None currently exceed the EWG guideline, but the presence of this chemical warrants attention. Long-term exposure to 1,3-DCP has been linked to increased cancer risk in laboratory animals. Human studies are limited, but the EPA classifies it as a probable human carcinogen. Children are particularly vulnerable because their bodies are still developing, and they drink proportionally more water relative to their body weight than adults.

## The Regulatory Gap

Here's where things get complicated: the EPA has not established a Maximum Contaminant Level (MCL) for 1,3-DCP in drinking water, despite recognizing it as a probable carcinogen. This means water utilities aren't required to test for it or remove it. The EWG's 0.3 ppb guideline is stricter and based on the precautionary principle—assuming lower exposure is safer when evidence is uncertain.

This regulatory gap leaves homeowners in affected areas without federal protection. Some states, particularly California, have been more proactive. California set its own standard at 0.6 ppb in 2018, recognizing the chemical's widespread presence in agricultural groundwater. However, most states follow federal guidelines, leaving them without any enforceable limit.

## Geographic Patterns and Why

Alabama leads with 15 water systems detecting 1,3-DCP, followed by New York with 6 systems. Single detections appear in South Carolina, California, and Georgia. The concentration in Alabama and the Southeast reflects the region's heavy agricultural use of soil fumigants, particularly in peanut and vegetable farming. New York's detections correlate with intensive agricultural zones in the Hudson Valley and Long Island, where groundwater contamination from decades of pesticide use remains a persistent problem.

California's single detection is notable given the state's strict regulations and extensive agricultural fumigant use. This suggests California's more aggressive testing and remediation efforts are working, though vigilance remains necessary.

## Removal and Protection

If your water system reports 1,3-DCP, activated carbon filtration is highly effective. Granular activated carbon (GAC) filters remove up to 99% of 1,3-DCP from drinking water. Reverse osmosis systems also work well, removing 95-99% of the chemical. Point-of-use filters—installed at your kitchen tap—provide immediate protection for drinking and cooking water at a fraction of the cost of whole-house systems.

Request your local water quality report to see if 1,3-DCP has been detected in your area. If it has, installing a certified carbon filter is a practical, affordable step to reduce your family's exposure while advocating for stronger state and federal standards.

Regulatory Standards for 1,3-Dichloropropane

Cities With the Highest 1,3-Dichloropropane Levels

States Most Affected by 1,3-Dichloropropane

Frequently Asked Questions

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