Excretion of hexachlorobenzene and metabolites in feces in a highly exposed human population

A set of 53 individuals from a population highly exposed to airborne hexach lorobenzene (HCB) were selected to study the elimination kinetics of this c hemical in humans. The volunteers provided blood, 24-hr urine, and feces sa mples for analysis of HCB and metabolites. The serum HCB concentrations ran ged from 2.4 to 1,485 ng/mL (mean +/- SD, 124 +/- 278), confirming that thi s human population has the highest HCB blood levels ever reported. All anal yzed feces samples contained unchanged HCB (range, 11-3,025 ng/g dry weight ; mean +/- SD, 395 +/- 629). The HCB concentration in feces strongly correl ated with HCB in serum (r = 0.85; p < 0.001), suggesting an equilibrium in feces/serum that is compatible with a main pulmonary entrance of the chemic al and low intestinal excretion of nonabsorbed foodborne HCB. The equilibri um is also compatible with a nonbiliary passive transfer of the chemical to the intestinal lumen. Two HCB main metabolites, pentachlorophenol (PCP) an d pentachlorobenzenethiol (PCBT), were detected in 51% and 54% of feces sam ples, respectively. All urine samples contained PCP and PCBT, confirming th e conclusions of a previous study [Environ Health Perspect 105:78-83 (1997) ]. The comparison between feces and urine showed that whereas daily urinary elimination of metabolites may account for 3% of total HCB in blood, intes tinal excretion of unchanged HCB may account for about 6%, thus showing the importance of metabolism in the overall elimination of HCB. The eliminatio n of HCB and metabolites by both routes, however, appears to be very small (< 0.05%/day) as compared to the estimated HCB adipose depots. Features of HCB kinetics that we present in this study, i.e., nonsaturated intestinal e limination of HCB and excretion in feces and urine of inert glutathione der ivatives, may explain, in parr, the absence of porphyria cutanea in this hu man population heavily exposed to HCB.