Time Course of Congener Uptake and Elimination in Rats after Short-Term Inhalation Exposure to an Airborne Polychlorinated Biphenyl (PCB) Mixture

Abstract

Despite the continued presence of PCBs in indoor and ambient air, few studies have investigated the inhalation route of exposure. While dietary exposure has declined, inhalation of the semi-volatile, lower-chlorinated PCBs has risen in importance. We measured the uptake, distribution and time course of elimination of inhaled PCB congeners to characterize the pulmonary route after short-term exposure. Vapor-phase PCBs were generated from Aroclor 1242 to a nose-only exposure system and characterized for congener levels and profiles. Rats were exposed via inhalation acutely (2.4 mg/m3 for 2 hr) or subacutely (8.2 mg/m3, 2 hr × 10 days), after which pulmonary immune responses and PCB tissue levels were measured. Animals acutely exposed were euthanized at 0, 1, 3, 6 and 12 hr post exposure to assess the time course of PCB uptake and elimination. Following rapid absorption and distribution, PCBs accumulated in adipose tissue, but decayed in other tissues with half-lives increasing in liver (5.6 hr) < lung (8.2 hr) < brain (8.5 hr) < blood (9.7 hr). PCB levels were similar in lung, liver and adipose tissue, lower in brain and lowest in blood. Inhalation of the airborne PCB mixture contributed significantly to the body burden of lower chlorinated congeners. Congeners detected in tissue were mostly ortho-substituted ranging from mono- to pentachlorobiphenyls. Selective uptake and elimination led to accumulation of a distinct congener spectrum in tissue. Minimal evidence of toxicity was observed.

Polychlorinated biphenyls and organochlorine pesticides in atmospheric particulate matter of Northern China: distribution, sources, and risk assessment

“…The PCBs in humans generally came from diet, but occupational exposure received increasing attention in recent years (Harrad et al 2006;Hu et al 2010). The chlorinated congeners can transform the genotoxic/ carcinogenic intermediates to effect on humans (Ludewig et al 2008).…”

Atmospheric polychlorinated biphenyls in Indian cities: Levels, emission sources and toxicity equivalents

“…The predominant source of human exposure to PCBs is the diet, but occupational exposure has received increasing attention in recent years (Harrad et al, 2006;Hu et al, 2010). Though the toxic effects on humans through direct inhalation are not yet clear but lower chlorinated congeners, predominating in air, may expose humans to reactive, possibly genotoxic/ carcinogenic intermediates because they are relatively easier metabolized (Ludewig et al, 2008).…”

Chiral polychlorinated biphenyls: absorption, metabolism and excretion—a review

“…In addition, PCBs can be formed inadvertently by industrial processes, which represent a contemporary source of certain PCB congeners. For example, PCBs are present in paint pigments from several manufactures in USA and Japan (Anezaki and Nakano 2014, Hu et al 2010). …”