If you live near a gas station, major highway, or in a state with a history of groundwater contamination, there's a chance MTBE may be in your drinking water. Methyl tert-butyl ether (MTBE) is a chemical that was added to gasoline for decades to reduce air pollution and improve fuel efficiency. But what was meant to help the environment has become a serious water quality problem for millions of Americans. This guide explains what MTBE is, why it matters, how to test for it, and what you can do to protect your family.
What Is MTBE and Why Is It in Drinking Water?
MTBE is a volatile organic compound (VOC) that was widely used as a gasoline additive starting in the 1970s. The Environmental Protection Agency (EPA) promoted its use because it helped gasoline burn more completely, reducing air pollution and meeting Clean Air Act requirements. By the 1990s, MTBE was present in about 30% of the gasoline sold in the United States.
The problem emerged slowly. MTBE is highly soluble in water, meaning it dissolves easily and travels through soil and groundwater. When gasoline leaked from underground storage tanks at gas stations, refineries, and pipelines, MTBE seeped into aquifers and groundwater supplies that many communities rely on for drinking water. Unlike some other contaminants, MTBE doesn't break down quickly in the environment. Once it enters groundwater, it persists for years.
The contamination became so widespread that the EPA issued a phase-out of MTBE in 2006. However, the damage was already done. Today, MTBE remains one of the most common groundwater contaminants in the United States, affecting drinking water supplies in at least 27 states.
Which States and Communities Are Most Affected?
MTBE contamination is not evenly distributed across the country. Certain regions have been hit much harder than others, primarily because they adopted MTBE-laced gasoline earlier or have higher population densities with more fuel infrastructure.
States with the Highest MTBE Contamination
- California has the most widespread MTBE problem in the nation. The state mandated oxygenated gasoline in the 1990s specifically to meet air quality goals, which accelerated MTBE use. Multiple drinking water systems have been forced to shut down wells due to MTBE contamination, affecting hundreds of thousands of residents.
- New York and the broader Northeast have experienced significant MTBE contamination, particularly in Long Island and the Hudson Valley where hundreds of public and private wells tested positive.
- New Jersey has documented MTBE in both public water systems and private wells throughout the state.
- Massachusetts has found MTBE contamination in numerous groundwater sources.
- Connecticut, Rhode Island, Florida, Ohio, and Texas have also reported significant detections.
If you live in any of these states, or near a major city, gas refinery, pipeline, or highway, your water may have been tested for MTBE. You can check whether your water utility has detected MTBE by using ClearWater's free ZIP code lookup tool at checkclearwater.com, which provides access to EPA drinking water quality reports for your area.
Health Risks and EPA Guidelines for MTBE
Understanding the health risks of MTBE is important for making informed decisions about your drinking water. However, the EPA's approach to MTBE is somewhat confusing because the agency has not set a legally enforceable maximum contaminant level (MCL) for it in drinking water.
EPA's Non-Enforceable Advisory Level
The EPA issued a non-enforceable health advisory for MTBE of 20 to 40 parts per billion (ppb) in 1997. A non-enforceable advisory means it is a recommendation, not a legal requirement that water utilities must follow. This creates a gap where some water systems may contain MTBE above what health experts consider safe, but water providers are not legally required to remove it.
Why no MCL? The EPA has been cautious about setting a binding limit because the health data on MTBE in humans is limited. Most studies on MTBE's effects have been conducted on animals rather than people, which makes it harder to establish a firm legal threshold.
Health Effects of MTBE Exposure
Laboratory and animal studies have identified several potential health concerns with MTBE exposure:
- Potential cancer risk: Studies in animals have suggested that long-term exposure to high levels of MTBE may increase cancer risk, particularly kidney and liver cancers. The EPA classifies MTBE as a possible human carcinogen based on animal evidence.
- Neurological effects: Some animal studies have shown that MTBE exposure can affect the nervous system and cause symptoms like dizziness, headaches, and tremors at high concentrations.
- Kidney and liver damage: Animal studies have documented damage to kidneys and livers at elevated exposure levels.
- Reproductive effects: Limited evidence suggests MTBE may affect reproduction and development in animals exposed at high doses.
It's important to note that most of this evidence comes from animal studies or workers exposed to high occupational levels. Direct evidence of these effects in humans drinking contaminated water is limited. However, the EPA and public health agencies take a precautionary approach: if a chemical causes concern in animal studies, it's treated as a potential human health risk until proven otherwise.
Who Is Most at Risk?
Certain groups may face higher risk from MTBE exposure:
- Infants and young children: Children have smaller body weights and developing organ systems, so they may be more sensitive to chemical exposures per unit of body weight.
- Pregnant women: Chemicals that cross the placental barrier could potentially affect fetal development.
- People on dialysis: Dialysis patients consume large quantities of treated water and may have reduced ability to clear certain chemicals.
- Individuals with compromised immune systems: People with weakened immunity may be more vulnerable to water quality issues.
How to Test Your Drinking Water for MTBE
Testing is the first step toward understanding whether MTBE is a concern in your home. There are several approaches depending on your water source and circumstances.
If You Get Water from a Public Water System
Public water utilities are required by the EPA to test for MTBE and issue annual Consumer Confidence Reports (also called Water Quality Reports) that detail any contaminants found. You can access this report by:
- Visiting your water utility's website and looking for the annual water quality report or Consumer Confidence Report.
- Calling your local water utility directly and requesting the report.
- Using ClearWater's free lookup tool at checkclearwater.com by entering your ZIP code. The tool aggregates EPA data and makes it easy to see whether MTBE or other contaminants have been detected in your area.
These reports must be provided to customers by July 1st each year and will show whether MTBE was detected, at what levels, and whether any action was taken. If your utility's report shows MTBE detection above the EPA's advisory level, you may want to consider additional home treatment.
If You Have a Private Well
Private well owners are not required to test for MTBE, but testing is strongly recommended if your well is located near a gas station, highway, industrial facility, or in a state with known MTBE contamination. Testing a private well for MTBE typically costs between $150 and $300 at a certified laboratory. To find a testing lab in your area:
- Contact your state's Department of Environmental Quality or Health Department.
- Ask your local county extension office for lab recommendations.
- Search for EPA-certified drinking water labs in your state online.
When you send a sample, the lab will test for MTBE and often other VOCs at the same time. Results typically come back within one to two weeks.
Home Test Kits
Over-the-counter home test kits for MTBE exist but are less reliable than certified laboratory testing. If you want a quick screening, some basic kits may give you a preliminary answer, but confirmation through a certified lab is recommended if results are positive or if you have health concerns.
How to Remove MTBE from Your Drinking Water
If testing shows MTBE in your water above the EPA advisory level, several treatment methods can effectively remove it. The best choice depends on your water source, contamination level, and budget.
Activated Carbon Filtration
Activated carbon is one of the most widely used and effective methods for removing MTBE from drinking water. Activated carbon works like a sponge, with a large surface area that absorbs MTBE molecules and other organic contaminants as water passes through.
Activated carbon is available in multiple forms:
- Pitcher filters: Affordable and simple, though they may not remove all MTBE and require frequent cartridge changes.
- Faucet-mounted filters: Inexpensive but slower flow rate and limited contact time with the filter.
- Under-sink filters: More effective because water has longer contact time with the carbon. Cartridges typically last 6 to 12 months depending on usage and contamination levels.
- Whole-house systems: Treat all water entering your home but are more expensive. Best for wells or homes where multiple family members need protection.
Important: Standard carbon filters work best for MTBE, but the cartridge must be replaced regularly. Once activated carbon becomes saturated with contaminants, it stops working. Manufacturers typically recommend replacement every 6 to 12 months for under-sink systems, but this varies based on water quality and usage.
Reverse Osmosis (RO) Systems
Reverse osmosis is another highly effective method for MTBE removal. RO systems force water through a semipermeable membrane under pressure, removing MTBE and most other contaminants including bacteria, viruses, and minerals. RO typically removes 95% or more of MTBE from drinking water.
RO systems are available in under-sink and whole-house configurations. They are more expensive than activated carbon, both in initial cost and ongoing maintenance. RO systems also produce wastewater (typically 3 to 4 gallons of waste water for every 1 gallon of treated water), so they are less water-efficient. However, they are highly effective and eliminate a broad range of contaminants beyond just MTBE.
Distillation
Distillation boils water and collects the steam, leaving contaminants behind. This method is effective for MTBE removal but is slow and energy-intensive. Home distillers produce only a few gallons per day, making them suitable only for drinking and cooking water, not whole-house use.
Air Stripping (Aeration)
Air stripping works by bubbling air through contaminated water, which causes MTBE to evaporate from the water. This method is very effective for MTBE because the chemical is volatile (it evaporates easily). Air stripping is commonly used by large water utilities but is less common for home use. Some advanced home systems incorporate aeration, but they are less widely available than carbon or RO filters.
Combination Approaches
Some homeowners use multiple treatment methods for maximum protection. For example, a combination of activated carbon followed by reverse osmosis provides redundancy and removes both MTBE and a broad spectrum of other contaminants.
Real-World MTBE Contamination Cases
Understanding how MTBE contamination has affected real communities helps illustrate the scope of the problem.
Santa Monica, California
Santa Monica experienced one of the most severe MTBE contamination events in the country. In the late 1990s, MTBE was discovered in multiple drinking water wells serving hundreds of thousands of residents. The contamination was traced to leaking underground gasoline storage tanks. The city was forced to shut down several wells and spend millions of dollars on treatment and remediation. This case highlighted how a single leaked tank could contaminate an entire groundwater basin.
Long Island, New York
Long Island's sole-source aquifer, which provides drinking water to 2.5 million people, has been significantly impacted by MTBE. Hundreds of private and public wells tested positive for MTBE in the 1990s and 2000s. Spill sites, aging gas stations, and leaking underground storage tanks were major sources. Some wells were permanently shut down, and treatment systems were installed to address contamination in others.
Nationwide Impact on Water Utilities
The MTBE problem prompted major water utilities across the country to upgrade their treatment systems. Water systems in California, New York, New Jersey, Massachusetts, and Florida have all invested in additional treatment infrastructure specifically to address MTBE. Some utilities switched to activated carbon treatment or reverse osmosis, significantly increasing operational costs that are often passed on to customers through higher water bills.
What Should You Do Now?
Here is a practical action plan for concerned homeowners:
Step 1: Check Your Water Quality Report
Find out whether MTBE has been detected in your water supply. Use your water utility's annual Consumer Confidence Report or visit checkclearwater.com with your ZIP code for quick access to EPA drinking water quality data specific to your area.
Step 2: Assess Your Risk
If you have a private well, determine whether your location warrants testing. Are you near a gas station, highway, industrial site, or in a state with known MTBE issues? If yes, consider professional testing.
Step 3: Choose a Treatment Method
If MTBE is detected above 20 ppb, activated carbon or reverse osmosis are the most practical home solutions. Activated carbon is more affordable and easier to maintain, while reverse osmosis is more comprehensive.
Step 4: Install and Maintain Your System
Follow manufacturer instructions carefully and replace filter cartridges on schedule. Write down the installation date and replacement date to stay on track.
Step 5: Test Again Periodically
Even after installing a treatment system, periodic testing confirms the system is working. Test annually or whenever you replace cartridges in under-sink systems.
The Bottom Line
MTBE in drinking water is a real but manageable problem. While the EPA has not set a legally binding limit, the agency's advisory level of 20 to 40 ppb reflects legitimate health concerns based on animal studies and the chemical's classification as a possible human carcinogen. Millions of Americans, particularly in California, the Northeast, and other areas with significant gasoline infrastructure, may be exposed.
The good news is that MTBE is relatively easy to remove with activated carbon, reverse osmosis, or other proven treatment methods. By checking your water quality, understanding your risk, and taking action if needed, you can protect your family from MTBE contamination. Start with a free lookup of your water quality using your ZIP code, then decide whether additional home treatment is right for your situation.