Negative-chemical-ionization mass spectral screening of extracts of human seminal plasma has revealed a presence of a Cl7 ion cluster at a mass-to-charge ratio (m/z) of 463 in a significant number of the samples examined (34 out of 123). Experiments with different gases used to generate the negative-chemical-ionization plasma indicated that the ion at m/z 463 was a chloride adduct of a Cl6 molecule with a mass of 428 daltons. Negative-chemical-ionization mass measurement with ions from the iodoform mass spectrum used as reference peaks gave a mass of 427.882 daltons; C9H15O4PCl6 has a molecular weight of 427.883. Extraction of polyurethane foam with toluene produced an extract that consistently gave a negative-chemical-ionization spectrum containing an intense Cl7 ion at m/z 463. The component producing this ion was isolated, and its proton nuclear magnetic resonance spectrum confirmed that it was tris(1,3-dichloro-2-propyl)phosphate, a mutagenic flame retardant. The negative-chemical-ionization screening evidence suggests that this flame retardant or its isomer tris(2,3-dichloro-1-propyl)phosphate, or both, are absorbed into the body from formulations in which they are used as flame retardants. Remedial action indicated reduced human exposure to these compounds.