1,2,3 Trichloropropane (TCP)
1,2,3-TCP·Affects liver, kidneys
A chlorinated solvent and pesticide impurity. A known human carcinogen with no federal MCL, but California regulates it at an extremely strict 5 parts per trillion.
1,2,3-TCP
EPA limit
No federal MCL (California MCL: 0.000005 mg/L / 5 ppt)
Most at risk
Households in California's Central Valley, Hawaii, and other agricultural areas with a history of soil fumigant use
Found in
Well water · Industrial areas
AquaOx filters
YesActivated coconut shell carbon
What it does to you
Health effects
1,2,3-TCP is one of the most potent carcinogens regulated in drinking water. California's Office of Environmental Health Hazard Assessment classifies it as a known human carcinogen, and the EPA lists it as likely to be carcinogenic. Animal studies show tumors at multiple organ sites including the liver, kidneys, and forestomach at very low doses.
Acute exposure can cause liver and kidney damage. Chronic low-dose exposure is the primary concern in drinking water, and the cancer risk drives the regulatory limit. California set its MCL at 5 parts per trillion, the lowest drinking-water standard for any organic contaminant in the United States.
There is no federal EPA MCL yet, though 1,2,3-TCP appears on the EPA's Contaminant Candidate List under consideration for future regulation.
Where it comes from
How it gets into your water
1,2,3-TCP is a notorious legacy contaminant from soil fumigant products such as Shell's D-D and Dow's Telone, applied for decades to control nematodes in pineapple, citrus, and row-crop fields. The fumigants contained TCP as a manufacturing impurity that was not disclosed to growers.
Because TCP is dense, persistent, and not strongly retained by soil, decades of application have left widespread groundwater plumes, particularly in California's Central Valley and former pineapple-growing areas of Hawaii. The compound is essentially impossible to remediate at scale and continues to spread.
Agricultural fumigants
Legacy impurity in nematicides
Contaminated wells
Widespread in California's Central Valley and Hawaii
Industrial sites
Solvent and chemical intermediate
Find out for yourself
Is it in your water?
Federal Consumer Confidence Reports may not list TCP because there is no federal MCL. California utilities are required to test and report. If you live in California's Central Valley, Hawaii, or other historic fumigant-use areas, check your local utility's TCP results directly.
Private well owners in agricultural regions should specifically request TCP testing using EPA Method 524.2 or 524.3 with a low detection limit. Many standard VOC panels will not detect at parts-per-trillion levels, so confirm the lab's reporting limit before ordering.
The fix
How AquaOx filters it
Activated carbon is the most cost-effective home treatment for TCP. The Centaur catalytic carbon and coconut shell carbon stages in The AquaOx adsorb the compound as water passes through. Municipal utilities in California have built large granular activated carbon plants specifically for TCP filtration.
Because the California standard is so low, we strongly recommend pairing The AquaOx with the under-sink RO at the kitchen tap for any household in a known TCP impact area. The two-stage approach delivers the lowest residual at the point of consumption.