1,2,3-Trichloropropane (TCP) is a synthetic chlorinated chemical that was once used as a cleaning solvent, paint remover, and ingredient in some pesticides and fumigants. It is not produced in large quantities today, but it persists in soil and groundwater at sites where it was used or spilled. Working in water treatment since 1994, I have seen how a chemical can outlast the industry that used it — and why old contamination still deserves attention today.
Where It Comes From
TCP reaches drinking water through several routes:
- Agricultural fumigants: TCP was a component in some soil fumigants used in agriculture. Residues can remain in soil and leach into groundwater over time.
- Industrial sites: Manufacturing and chemical processing facilities that used TCP as a solvent or degreaser can leave contaminated soil and groundwater behind.
- Improper disposal: Dumping, spills, and leaking tanks at industrial sites can release TCP into the ground, where it migrates into aquifers.
What It Can Do to Health
TCP is classified as a probable human carcinogen. Animal studies have shown that exposure can cause tumors in multiple organs. California’s Office of Environmental Health Hazard Assessment has identified TCP as a carcinogen, and the state has set a public health goal for TCP in drinking water.
The EPA Drinking-Water Limit
At the federal level, the U.S. Environmental Protection Agency does not currently have an enforceable Maximum Contaminant Level (MCL) for 1,2,3-trichloropropane. However, California has set a state MCL of 0.005 micrograms per liter (µg/L) — one of the lowest drinking-water standards in the country — reflecting TCP’s potency as a carcinogen.
Which Home Filtration Actually Removes It
TCP is a volatile organic compound (VOC) that responds well to activated carbon filtration:
- Activated carbon filtration (granular or solid block): Activated carbon adsorbs VOCs like TCP as water passes through the porous carbon surface. This is the primary home treatment method for this contaminant.
- Reverse osmosis (RO): Residential RO systems combine activated carbon pre-filtration with a semipermeable membrane (pores around 0.0001 microns) to filter out organic contaminants.
Understanding Certification Standards
- NSF/ANSI Standard 53: This is the health-effects standard for drinking water treatment units. In plain English, a Standard 53 certification verifies that a filter reduces the specific contaminants named in that model’s certification — TCP among them, if it is listed. Check the certification list, not just the seal.
- NSF/ANSI Standard 58: This is the performance standard for reverse osmosis systems. It certifies the system and the specific reductions listed in its certification; check the list.
Facts first, then filter. — Steve
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