How did 1,2,3-trichloropropane, a soil fumigant impurity from decades ago, end up in groundwater now?
1,2,3-Trichloropropane (TCP) is a chlorinated solvent that was used as an impurity in soil fumigants primarily from the 1950s through the 1980s. Its presence in groundwater often results from past agricultural practices where fumigants containing TCP seeped into soil layers and slowly migrated downward over many years. Because groundwater moves slowly, residues of this chemical can appear in water sources long after its use has ended. This delayed arrival is why 1,2,3-TCP detections in water systems can be a legacy concern, even in areas where it is no longer applied.
How does California's 5 ng/L (parts per trillion) guideline for 1,2,3-TCP compare to the absence of a federal maximum contaminant level?
The federal government has not established a maximum contaminant level (MCL) for 1,2,3-TCP, meaning there is no legally enforceable drinking water limit at the national level. However, California has set a public health goal of 0.005 micrograms per liter (µg/L), or 5 nanograms per liter, which is equivalent to 0.005 parts per billion (ppb). This guideline is notably more stringent and reflects a precautionary approach to this chlorinated solvent. It is important to recognize that the lack of a federal MCL does not imply safety or risk but indicates ongoing evaluation by regulatory agencies. Different states may choose varied benchmarks based on their assessments and policies.
What does a certified laboratory test for 1,2,3-trichloropropane report and how should I read it?
A certified laboratory test report for 1,2,3-TCP will typically show the concentration in micrograms per liter (µg/L), equivalent to parts per billion (ppb). The test focuses on detecting whether concentrations exceed the laboratory’s reporting level, which for 1,2,3-TCP is often around 0.03 µg/L (30 parts per trillion). This reporting level is the lowest concentration the lab can consistently measure, and values below this level are generally indicated as 'not detected' or 'below reporting level.' It is essential to understand that a detection above the reporting level does not mean the water is violating standards or is unsafe; it simply means measurement instruments have found trace levels of the chlorinated solvent in the water sample.
Why is the reporting level for 1,2,3-TCP thousands of times lower than for common metals in water testing?
The reporting level for 1,2,3-TCP is set very low because of its chemical potency and the concern over its presence even at trace levels. Chlorinated solvents like TCP can pose health risks at concentrations far lower than those typical for metals such as lead or iron. This higher sensitivity requires analytical methods capable of detecting parts per trillion concentrations, which is thousands of times lower than levels used for many metals testing. Consequently, test reports for 1,2,3-TCP often show 'non-detect' results even when some trace molecules are present, reflecting the strict detection thresholds rather than indicating a regulatory violation or immediate safety concern.
What should households with multiple residents or seasonal use consider regarding 1,2,3-TCP testing and treatment?
For larger households or properties used seasonally, it is especially important to obtain a recent, certified laboratory test specific to your home's water source. Area-wide data, like that from the Parker Water and Sanitation District serving Douglas County, show no detections of 1,2,3-TCP above 0.03 µg/L in public water samples collected between 2013 and 2015, covering about 75,949 residents across 20,005 connections. While this offers some regional reassurance, an individual home's water can differ due to private wells or plumbing variations. Seasonal or second homes might experience varying water quality due to inactivity or different source connections. Testing allows tailored decisions about water treatment needs, such as using the Pentair 1,2,3-TCP Filter, a product designed to address this chlorinated solvent specifically and ships ready to configure in your home's water system.
What should I not conclude from regional 1,2,3-TCP monitoring data?
It is important not to assume that the absence of detectable 1,2,3-TCP in regional or public water system data guarantees that your home's water is free from this chlorinated solvent. Conversely, a detection reported in your test does not automatically mean the water is unsafe or violates health standards. Government sampling results represent averages or snapshots for the public water system as a whole and do not replace individual water testing. To understand your home's water quality thoroughly, obtaining a certified laboratory analysis is necessary. This ensures that treatment choices are based on precise, current information rather than area-wide monitoring alone.
Where this information comes from
Source: EPA SDWIS public water system record. Sampled 2013-11-04. These figures describe the public water system's record, not the plumbing inside any individual building.
On record: EPA UCMR3 monitoring (2013-2015) for Parker WSD (CO0118040), CO: 16 results across 1 listed contaminants, 0 detections above the reporting level; nothing detected above the method reporting level