TCE in Minnesota community water systems

Total Trichloroethylene (TCEs) in Minnesota community water systems:

• Mean TCE levels
• Maximum TCE levels
• People served, by mean TCE levels

What is TCE and where is it found? 

Trichloroethylene (TCE) is a common environmental contaminant that dissolves in water and readily evaporates from soil and water into the air. If spilled on the ground, TCE can move through soil and into groundwater where it may pollute private and public drinking water wells. TCE is:

• a nonflammable, colorless liquid or gas 
• sweet-smelling at high concentrations, but odorless at lower levels 
• used in industry for degreasing metal parts and has been used as a dry-cleaning solvent 
• also found in household products such as wood finishes, adhesives, paint removers, lubricants, and cleaners 

Standards and guidance for TCE in Minnesota water systems 

The maximum contaminant level (MCL) for TCE is 5 micrograms per liter of drinking water (µg/L). Maximum Contaminant Levels (MCLs) are set by the United States Environmental Protection Agency (US EPA) and enforced by Minnesota Department of Health (MDH). All public water systems in Minnesota must meet these standards. 

Drinking water with TCE at levels lower than the MCL may increase the risk of adverse health effects for some people. As a result, MDH set a health-based value (HBV) of 0.4 µg/L for TCE in drinking water. This guidance does not consider the feasibility or cost of water treatment to reach that level of TCE in drinking water. 

This concentration is safe for all people at any time during their life, including pregnant women and their fetuses, infants, children, and other sensitive people, including those with impaired immunity. This value also protects people exposed to TCE in drinking water used in any way (ingesting water, showering, cooking, etc.). 

At 2 μg/L of TCE in drinking water, all people who are exposed for a lifetime are protected from cancer. At this concentration, the increased risk is estimated to be no more than 1 additional cancer in 100,000 people. This concentration of TCE in drinking water is also safe for healthy adults and protects pregnant women and their developing fetus from heart defects.

Health effects of TCE 

The main health concerns from exposure to TCE at the lowest exposures are the potential for immune system effects such as immunosuppression or autoimmune disease, including increased hypersensitivity. Other effects may be a concern at higher concentrations, such as an increased chance of cancer from long-term exposure and heart defects in the developing fetus if the pregnant mother is exposed in the first trimester. The concentration of TCE that is considered a risk to health depends on many variables, such as the amount of water a person drinks, their size, their age, and whether they have other health conditions, such as an immune condition. 

The chart above shows the percent of community water systems by TCE mean annual concentration. In Minnesota, there are no systems with TCE at levels of concern.

In the chart above, the maximum value of each system shows the highest concentration in any single sample, prior to any blending of water in the distribution system. The level of TCE in blended water that reaches the consumer's tap may be lower because of dilution. 

Minnesota residents drink water with TCE below levels of concern

The table below shows the number of people served by community water systems by mean concentration of TCE. Note that the estimates of number of people served by each system are rough calculations periodically updated by water system managers.

Population served, by mean TCE annual concentration of their Community Water Systems, 2020 

Health effects of TCE 

The main health concerns from exposure to TCE at the lowest exposures are the potential for immune system effects such as immunosuppression or autoimmune disease, including increased hypersensitivity. Other effects may be a concern at higher concentrations, such as an increased chance of cancer from long-term exposure and heart defects in the developing fetus if the pregnant mother is exposed in the first trimester. The concentration of TCE that is considered a risk to health depends on many variables, such as the amount of water a person drinks, their size, their age, and whether they have other health conditions, such as an immune condition. 

Most community systems provide drinking water with TCE below levels of concern  

No community water systems exceed the MCL for TCE. All Community Water Systems (CWS) test for TCE and other contaminants. If a system's TCE levels are above the MCL, the CWS notifies customers and makes changes to reduce the level.  

Very few exceed the health-based guidance of 0.4 and no systems exceed the health-based guidance of 2. MDH works with CWSs to reduce levels of TCE to below the health-based guidance value, when possible. 

What can be done about TCE in drinking water? 

Customers of community water systems can find out the level of TCE in their drinking water by reading the Consumer Confidence Report (sometimes called the Water Quality Report) issued each year by their water utility. 

MDH works with community water systems to reduce levels of TCE to below the health-based guidance value, when possible. 

Sometimes a system can find a new water source. It may also blend water from more than one source to the point that the blended water is at acceptable levels of TCE. Another option is to install a treatment process to reduce the TCE levels. Treatment options include packed tower aeration and granular active carbon adsorption. In addition, studies have shown that advanced oxidation processes involving ozone or ultraviolet light may be effective. A water system will consider many factors, including cost, when deciding on an option. 

Related topics: 

TCE and Your Health