How does California’s 5 ng/L State Limit for 1,2,3-TCP compare to the lack of a federal MCL?
California sets a state-level notification level for 1,2,3-trichloropropane (also known as 1,2,3-TCP or TCP) at 5 nanograms per liter (ng/L), which is equivalent to 0.005 micrograms per liter (µg/L). This is a precautionary benchmark not matched by the federal government, which currently does not have an enforceable maximum contaminant level (MCL) for 1,2,3-TCP under the Safe Drinking Water Act. Instead, federal sampling programs like the EPA’s Unregulated Contaminant Monitoring Rule (UCMR) report detections without defining these as violations or unsafe levels. This means that even if 1,2,3-TCP is measured in your municipal water, it is not classified as a health-based violation at the federal level.
How did a soil fumigant impurity from the 1950s–1980s reach deep groundwater decades later?
1,2,3-TCP is a synthetic chlorinated solvent once used as an impurity in soil fumigants widely applied in agricultural areas during the mid-20th century. Over time, it has migrated from the soil into groundwater and surface water supplies. Contamination can persist for decades due to the compound’s chemical stability and resistance to natural breakdown. Although Adams County’s South Adams County Water and Sanitation District (WSD) draws from surface water sources today, legacy contamination from this era can still be a consideration for water quality monitoring in the region.
What should Adams County residents do to understand their own home's 1,2,3-TCP situation?
The South Adams County WSD public water system record from EPA UCMR3 monitoring between 2013 and 2015 showed 28 samples with zero detections of 1,2,3-TCP above the reporting level of 0.03 µg/L (30 parts per trillion or ppt). Since these results are system-wide averages and do not reflect individual plumbing or private wells, households considering their own exposure should arrange a specialized laboratory test of their tap water if they suspect any source other than municipal supply. Testing will reveal the actual TCP concentration in their home. This stepwise approach helps separate broader public water system data from individual water quality.
What household or water facility symptoms might suggest 1,2,3-TCP presence?
1,2,3-Trichloropropane is a volatile chlorinated solvent without distinctive taste, odor, or color at typical concentrations, so it does not cause aesthetic symptoms such as staining or noticeable tastes. Complaints about water quality are unlikely to signal the presence of TCP specifically. Because it is chemically stable and does not cause corrosion or visible residues, typical household water issues like discoloration, sediment, or unusual taste stem from other causes.
Why do aesthetic secondary standards differ from health-based limits when applied to this compound?
Aesthetic secondary standards regulate constituents based on taste, odor, and appearance rather than health risk. For example, chloride or total dissolved solids may affect how water tastes or stains plumbing, but 1,2,3-TCP is primarily a contaminant of concern due to potential long-term health effects rather than aesthetic impact. The South Adams County WSD’s EPA record shows no health-based violations related to 1,2,3-trichloropropane, confirming that federally monitored levels are below thresholds requiring regulatory action. This distinction clarifies why monitoring focuses on detection rather than appearance or taste considerations.
In summary, Adams County’s public water system serving over 75,000 people has documented zero 1,2,3-TCP detections above the UCMR3 reporting limit during 2013-2015. This federal record covers system-wide measurements from surface water sources without any health-based violations. To know an individual household’s water quality for TCP, specialized laboratory testing is necessary. The C-Series 1,2,3-TCP Filter ships ready to configure and is a documented option for residential water treatment where testing confirms the presence of this chlorinated solvent.
For official data and further details, consult the EPA’s Safe Drinking Water Information System (SDWIS) public water system records for South Adams County WSD at the EPA website.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2014-02-10. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for South Adams County WSD (CO0101140), CO: 28 results across 1 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level