Contaminants of Emerging Concern
1,2,3-Trichloropropane (1,2,3-TCP)

September 2011

farmlandSome chemicals have many uses, but we do not hear much about them. This is the case with 1,2,3-trichloropropane (1,2,3-TCP). 1,2,3-TCP is mainly used to make other chemicals. It is also a contaminant of pesticides that were used in Minnesota to get rid of insects, worms, weeds, and fungi in soil (soil “fumigants”). Although these pesticides are no longer registered for use in Minnesota, some 1,2,3-TCP may have remained in the environment and reached drinking water. MDH developed three new guidance values for 1,2,3-TCP in 2010. The lowest MDH guidance value for 1,2,3-TCP is 0.003 parts per billion (ppb or micrograms per liter) in drinking water. This value is to protect against cancer. MDH just finished a small-scale study of 1,2,3-TCP in water, including drinking water sources. MDH used a new method that can detect as little as 0.0007 ppb 1,2,3-TCP; so far, none has been found. If we do find 1,2,3-TCP in drinking water, having guidance values will help us decide if 1,2,3-TCP poses a health risk to Minnesotans.


  • 1,2,3-TCP is a contaminant of soil fumigants that were once used in Minnesota. It is also an organic solvent used in industrial settings as a cleaner, degreasing agent, solvent, and paint/varnish remover.
  • So far, 1,2,3-TCP has not been found in drinking water sources, groundwater, or surface water in Minnesota. However, very few studies have looked for 1,2,3-TCP in drinking water sources in Minnesota.
  • MDH recently conducted a small-scale study using a new, more sensitive test method. The new method measures 1,2,3-TCP at much lower concentrations than we could before (0.0007 ppb). 1,2,3-TCP was not found in any of the water sources tested, even using the new method.
  • The Minnesota Pollution Control Agency (MPCA) found 1,2,3-TCP in only one of 54,288 groundwater samples. The concentration of
    1,2,3-TCP in this one sample was 4.3 ppb. These samples were taken at closed landfills from 1998-2007. This study used an older, less sensitive, test method.
  • The lowest MDH guidance value for 1,2,3-TCP is 0.003 ppb in drinking water. If you drink water containing up to 0.003 ppb for up to a lifetime there is little to no health risk, including cancer risk.
  • Exposure to 1,2,3-TCP can occur if contaminated water is used for drinking, showering, bathing, or cooking.
  • The toxicity of 1,2,3-TCP was recently reevaluated. This reevaluation showed that 1,2,3-TCP is more toxic than previously known. The
    0.003 ppb guidance value for 1,2,3-TCP is very low, which means small amounts may cause cancer.
  • MDH does not have specific recommendations for individual action at this time.

A Citizen's Guide is currently under development for 1,2,3-TCP. Check this page for updates.

See the Exposure and Toxicity Summary (PDF: 37KB/3 pages) for additional information about 1,2,3-TCP. This information was gathered before the MDH guidance value was completed.

Do you need more details about the health-based guidance?

See 1,2,3-TCP Toxicity Summary information used by MDH (PDF: 147KB/6 pages) for toxicity values used to develop health-based guidance.

Do you need more technical information about toxicity and exposure?

 “An Environmental and Health Professional’s Technical Guide to
1,2,3-TCP” will be posted here and announced to our email subscriber list when available. Subscribe to our email notification service by selecting "Groundwater Rules, Guidance and Chemical Reviews.”

Updated Wednesday, October 05, 2011 at 08:04AM