The fate of inhaled 14C-labeled PCB11 and its metabolites in vivo

- We performed a mass balance study in rats after delivering [14C]PCB11 to the lung.
- The absorption of PCB11 in lung was rapid and complete (99.8%).
- 35% of the dose was excreted via feces and 18% via urine within 12 h postexposure.
- Half-lives of initial tissue elimination were ≤ 30 min except for skin and fat.
- Phase II metabolites dominated and decayed more slowly than other compounds.

BackgroundThe production ban of polychlorinated biphenyl (PCB) technical mixtures has left the erroneous impression that PCBs exist only as legacy pollutants. Some lower-chlorinated PCBs are still being produced and contaminate both indoor and ambient air.ObjectivesTo inform PCB risk assessment, we characterized lung uptake, distribution, metabolism and excretion of PCB11 as a signature compound for these airborne non-legacy PCBs.MethodsAfter delivering [14C]PCB11 to the lungs of male rats, radioactivity in 34 major tissues and 5 digestive matter compartments was measured at 12, 25, 50, 100, 200 and 720 min postexposure, during which time the excreta and exhaled air were also collected. [14C]PCB11 and metabolites in lung, liver, blood, digestive matter, urine, feces, and adipose tissues were extracted separately to establish the metabolic profile of the disposition.Results[14C]PCB11 was distributed rapidly to all tissues after 99.8% pulmonary uptake and quickly underwent extensive metabolism. The major tissue deposition of [14C]PCB11 and metabolites translocated from liver, blood and muscle to skin and adipose tissue 200 min postexposure, while over 50% of administered dose was discharged via urine and feces within 12 h. Elimination of the [14C]PCB11 and metabolites consisted of an initial fast phase (t½ = 9-33 min) and a slower clearance phase to low concentrations. Phase II metabolites dominated in liver blood and excreta after 25 min postexposure.ConclusionsThis study shows that PCB11 is completely absorbed after inhalation exposure and is rapidly eliminated from most tissues. Phase II metabolites dominated with a slower elimination rate than the PCB11 or phase I metabolites and thus can best serve as urine biomarkers of exposure.

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