CHLORPYRIFOS METABOLITES IN SERUM AND URINE OF POISONED PERSONS

Concentrations of parent pesticide and corresponding diethylphosphorus metabolites in blood serum and urine were investigated in persons who had ingested a concentrated solution of organophosphorus pesticide ch lorpyrifos. The organophosphate poisoning was indicated by a significa nt depression of blood cholinesterase (EC 3.1.1.7 and EC 3.1.1.8) acti vities. Blood and spot urine samples were collected daily after admiss ion of the persons to hospital. Chlorpyrifos was detected only in seru m samples in a period up to 15 days after posioning. In the same sampl es chlorpyrifos oxygen analogue, chlorpyrifos oxon, was not detected. The presence of diethylphosphorothioate in all serum and urine samples confirmed that part of chlorpyrifos was hydrolysed before its oxidati on. The maximum concentrations of chlorpyrifos in serum and of metabol ites in serum and urine were measured on the day of admission. The dec rease in concentrations followed the first-order kinetics with the ini tial rate constant faster and the later one slower. In the faster elim ination phase chlorpyrifos was eliminated from serum twice as fast (t1 /2 = 1.1 - 3.3 h) as the total diethylphosphorus metabolites (t1/2 = 2 .2 - 5.5 h). The total urinary diethylphosphorus metabolites in six ch lorpyrifos posioned persons were excreted with an average elimination half-time of 6.10 +/- 2.25 h (mean +/- S.D.) in the faster and of 80.3 5 +/- 25.8 h in the slower elimination phase.