What is 1,2-Dichloropropane and Why Does It Matter?

1,2-Dichloropropane is a synthetic chemical that doesn't occur naturally in the environment. It was once widely used as a soil fumigant to kill pests before planting crops, and it still shows up as a byproduct in some chlorinated solvent mixtures. Industrial facilities that manufacture or use chlorinated chemicals can release it into the surrounding soil and groundwater. From there, it slowly migrates into drinking water sources — sometimes decades after the original contamination occurred.

This chemical has been detected in 63 water systems across the United States. Of those, 19 systems are delivering water at levels that exceed the EWG's health guideline. The average detected level sits at 0.386 parts per billion (ppb), but some systems have measured as high as 2.3 ppb. That upper number is significant, because even low-level exposure over time raises real health concerns.

The International Agency for Research on Cancer (IARC) classifies 1,2-dichloropropane as a Group 1 carcinogen — meaning there is sufficient evidence it causes cancer in humans. Most of that evidence comes from studies of workers exposed to high concentrations, particularly cases of bile duct cancer (cholangiocarcinoma) in printing industry workers in Japan. At the lower levels found in drinking water, the risk is smaller, but it is not zero. Long-term consumption of water containing this compound may increase cancer risk over time, according to the EWG. Children and pregnant women face heightened concern because their bodies are more vulnerable to chemical exposure during development.

The EPA's legal limit — called a Maximum Contaminant Level (MCL) — for 1,2-dichloropropane is 5 ppb. The EWG's health guideline, however, is set at just 0.4 ppb. That's a 12-fold difference between what's legally allowed and what researchers consider safe for long-term consumption. Why the gap? EPA limits are set using a mix of health science and economic feasibility, meaning cost and technical limitations factor into the final number. The EWG guideline is based purely on the health risk. The highest levels detected in U.S. water systems — up to 2.3 ppb — fall below the EPA's legal limit, but they exceed the EWG health guideline by nearly 6 times.

Geographically, North Carolina leads the country with 22 affected water systems, followed by Florida with 13, New York and California with 6 each, and Ohio with 3. North Carolina and Florida's numbers likely reflect a combination of historical agricultural fumigant use and industrial activity near water sources. Both states have significant farming regions where soil fumigants were applied heavily in past decades. New York and California's affected systems tend to cluster near older industrial sites and areas with legacy chemical manufacturing. If you live in any of these states — especially in a rural or semi-rural area — it's worth checking your local water quality report, also called a Consumer Confidence Report (CCR), which your utility is required to provide annually.

The good news is that 1,2-dichloropropane is very effectively removed with the right filtration. Activated carbon filters can reduce levels meaningfully, but reverse osmosis (RO) is the gold standard. A properly functioning RO system removes up to 99% of volatile organic compounds (VOCs) like 1,2-dichloropropane from your drinking water. Echo Water's reverse osmosis systems are designed specifically for contaminants like this — chemicals that slip through basic filters but can't survive the multi-stage RO process. If you're on a municipal system in one of the affected states, or if you have a private well near agricultural or industrial land, an under-sink RO system is one of the most practical steps you can take. Testing your water first gives you a clear picture of what you're dealing with — and confirms whether your filter is doing its job.

Regulatory Standards for 1,2-Dichloropropane

Cities With the Highest 1,2-Dichloropropane Levels

States Most Affected by 1,2-Dichloropropane

Frequently Asked Questions

Related Contaminant Guides