Dichlorodifluoromethane in Drinking Water
Found in 56 water systems • vocs
Updated September 2026 • Data from EWG & EPA
What is Dichlorodifluoromethane and Why Does It Matter?
# Dichlorodifluoromethane in Tap Water: What You Need to Know
Dichlorodifluoromethane, commonly known as CFC-12 or Freon, is a synthetic chemical that was widely used in refrigeration and air conditioning systems throughout the 20th century. It enters groundwater when old appliances leak or are improperly disposed of, and it can persist in water for decades. Our analysis found dichlorodifluoromethane in 56 public water systems across the United States, with the highest concentration reaching 7.8 parts per billion (ppb). While the average level is much lower at 0.773 ppb, the presence of this chemical anywhere in drinking water signals potential contamination from aging infrastructure or improper waste disposal in your area.
The health effects of dichlorodifluoromethane exposure depend on the amount and duration of contact. At the low levels typically found in drinking water, the immediate health risks are minimal. However, the chemical is classified as a volatile organic compound (VOC), and long-term exposure to elevated levels has been linked to neurological effects and liver damage in animal studies. The EPA has not established a maximum contaminant level (MCL) for dichlorodifluoromethane in drinking water, meaning there's no federal limit that water utilities must meet. This absence of regulation doesn't mean the chemical is safe—it simply means the EPA hasn't determined a specific threshold for public water systems. The Environmental Working Group (EWG) has not published a health guideline for this contaminant either, which reflects the limited human health data available.
Interestingly, none of the 56 water systems we detected dichlorodifluoromethane in exceeded any existing guideline, partly because formal guidelines are sparse. This regulatory gap creates a gray area where a contaminant can be present in your water without triggering mandatory action from your utility. Water utilities in affected areas are not required to notify customers about dichlorodifluoromethane unless it exceeds an MCL, which it currently does not. However, the fact that it appears in 56 systems suggests it's worth monitoring, especially as environmental regulations evolve and scientific understanding improves.
New York leads the nation with 23 affected water systems, followed by California with 16 systems. Wisconsin, Nebraska, and Vermont round out the top five states. The concentration in New York likely reflects both the age of the water infrastructure and the historical prevalence of refrigeration and cooling systems in the region. California's high count may similarly point to aging infrastructure combined with industrial activity. These geographic patterns suggest that older regions with established manufacturing and commercial cooling systems are more vulnerable to this contamination.
Removing dichlorodifluoromethane from your tap water requires activated carbon filtration or reverse osmosis. Activated carbon filters excel at capturing volatile organic compounds like dichlorodifluoromethane, typically removing 85-95% of the chemical when properly installed and maintained. Reverse osmosis systems are even more effective, removing up to 99.9% of dichlorodifluoromethane along with other contaminants. If you live in New York, California, or other affected areas, a whole-home activated carbon system provides broad protection for all your water uses. For drinking water specifically, a point-of-use reverse osmosis system under your kitchen sink offers the highest level of protection. Replace activated carbon filters every 6-12 months, depending on water usage and contaminant levels, to maintain effectiveness. If you're unsure whether your water system is affected, check your local water quality report or contact Echo Water for a detailed water analysis tailored to your address.
Regulatory Standards for Dichlorodifluoromethane
| Standard | Level | Notes |
|---|---|---|
| Average Detected Level | 0.77 ppb | Across all tested systems |
| Highest Detected Level | 7.80 ppb | Worst-case system |
Cities With the Highest Dichlorodifluoromethane Levels
| # | City | Detected Level | People Served |
|---|---|---|---|
| 1 | Alexandria Bay, NY | 7.80 ppb | 60 |
| 2 | Alexandria Bay, NY | 7.80 ppb | 500 |
| 3 | Alexandria Bay, NY | 7.80 ppb | 0 |
| 4 | San Jose, CA | 3.30 ppb | 22,620 |
| 5 | Gresham, NE | 2.31 ppb | 0 |
| 6 | Cecilton, MD | 1.53 ppb | 0 |
| 7 | San Bernardino, CA | 1.41 ppb | 204,870 |
| 8 | Altoona, WI | 1.02 ppb | 7,345 |
| 9 | Saranac Lake, NY | 0.86 ppb | 90 |
| 10 | Port Orchard, WA | 0.71 ppb | 126 |
| 11 | Garden City, NY | 0.69 ppb | 46,000 |
| 12 | Upland, CA | 0.68 ppb | 78,376 |
| 13 | San Jose, CA | 0.65 ppb | 60,215 |
| 14 | Abbotsford, WI | 0.65 ppb | 1,956 |
| 15 | Stowe, VT | 0.60 ppb | 240 |
States Most Affected by Dichlorodifluoromethane
How to Remove Dichlorodifluoromethane From Your Water
CFC-12 is a volatile compound effectively removed by activated carbon filters through adsorption; aeration also helps due to its volatility. Standard pitcher and fridge filters are adequate.
Standard pitcher filters and carbon block filters can provide some reduction of Dichlorodifluoromethane, though effectiveness varies by brand and flow rate. For maximum protection, a certified RO system is recommended.
CFC-12 removal is straightforward with carbon or aeration; the primary concern is environmental contamination and ozone layer impact rather than drinking water toxicity.
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Shop Hydrogen FlaskFrequently Asked Questions
Is Dichlorodifluoromethane in my drinking water?
Dichlorodifluoromethane was detected in 56 water systems across the US. Check your city's water quality report to see if it affects your water supply.
What are the health effects of Dichlorodifluoromethane in water?
Dichlorodifluoromethane has been associated with various health concerns at elevated levels. The EWG has set health guidelines that are typically stricter than EPA legal limits.
Which city has the most Dichlorodifluoromethane in its water?
Based on our analysis, Alexandria Bay, NY has the highest detected levels of Dichlorodifluoromethane in its water supply.
How do I remove Dichlorodifluoromethane from my water?
Reverse osmosis (RO) systems are generally the most effective at removing this contaminant. Check the filtration recommendations section for specific guidance.
Related Contaminant Guides
Data sources: Environmental Working Group (EWG) Tap Water Database, U.S. EPA Safe Drinking Water Information System (SDWIS)
Last updated: September 2026
Methodology: Contaminant levels are compared against both EPA legal limits (Maximum Contaminant Levels) and EWG health guidelines, which are often stricter and based on the latest scientific research.
