What is 1, 2, 3 - TCP? 1, 2, 3 - TCP is a man-made, colorless, chlorinated hydrocarbon that is used as a degreasing and cleaning agent and industrial solvent. It was also used as a chemical in pesticides for low growing crops such as potatoes, tobacco, and beets. 1, 2, 3 - TCP passes through soil and leaches into ground water, contaminating drinking water sources. 1, 2, 3 - TCP is a non-aqueous liquid that is more dense than water, making it difficult to remove from ground water wells. This compound is currently unregulated by the USEPA, although it is on the Contaminant Candidate List 4 (CCL4) for future regulation.