Determination of Polycyclic Aromatic Hydrocarbons (PAH) and Their Metabolites in Blood, Feces, and Urine of Rats Orally Exposed to PAH Contaminated Soils

Abstract

Polycyclic aromatic hydrocarbons (PAH) have become an ubiquitous upper soil component as a consequence of industrialization involving a multitude of combustion processes. Ingestion of PAH contaminated soil is considered to be a major exposure route, specifically for small children living on these soils. Health risk assessment is based on extrapolations from data obtained via studies performed with pure chemicals. Additionally it is assumed that after oral intake all PAH present in the soil will be absorbed by the human body. Interactions with the soil matrix, however, may modulate the bioavailability of PAH. In this study, we examined the absorption and excretion of PAH in rats orally exposed either to industrially contaminated soils or pure model compounds as anthracene, pyrene and benzo(a)pyrene (B[a]P). The model compounds and the metabolites, 1-hydroxypyrene (1-OH-pyrene) and 3-hydroxybenzo(a)pyrene (3-OH-B[a]P), were measured in blood, feces or urine by means of HPLC with fluorescence detection. Because of rapid biotransformation only minimal levels of unmetabolized anthracene, pyrene and B[a]P in blood could be detected. The pharmacokinetic parameters were nonlinear and suggestive of enterohepatic cycling. Only low levels of the compounds were excreted unchanged in feces whereas the levels of the metabolites were considerably higher in feces and urine. These results indicate that the dosed PAH are largely absorbed by the gastrointestinal tract, subsequently metabolized and excreted as metabolites via urine and feces. Significant differences between the soil-treated group and the pure mixture-treated group could be observed; the soil-treated group showed higher fecal excretion of unchanged pyrene (0.5 versus 0.2% of the original dose) and B[a]P (1 versus 0.3%), lower excretion of 1-OH-pyrene in feces (5.1 versus 17. 0%), and lower excretion of 1-OH-pyrene in urine (0.2 versus 3.4%). The fecal excretion of 3-OH-B[a]P between the two groups was similar (8.8 versus 8.8%). These results suggest that the soil matrix is capable of reducing the absorption of at least pyrene. Therefore, exposure risk assessment models assuming complete bioavailability of soilmatrix-bound PAH probably overestimate the endogenous dose.

Intestinal absorption of 14C from 14C-phenanthrene, 14C-benzo[a]pyrene and 14C-tetrachlorodibenzo-para-dioxin: approaches with the Caco-2 cell line and with portal absorption measurements in growing pigs

“…Some previous studies suggest an intestinal metabolism of lipophilic micropollutants, especially PAHs [11,25]. The results presented here probably accounted for the absorption of the molecules but also for their metabolism.…”

“…Many in vivo studies on dioxins and some works on PAHs report that the absorption mechanisms of these molecules depend on their matrices and their physicochemical properties (water solubility, lipophilicity and molecular weight mainly) [6][7][8][9][10][11][12]. Among PAHs, some studies with fish or rats suggest that the compounds are absorbed differently by the gastrointestinal tract, maybe as a function of their physicochemical characteristics [13,14].…”

Bioaccumulation and biotransformation of pyrene and 1‐hydroxypyrene by the marine whelk Buccinum undatum

“…Polar metabolites of PAHs accumulate in bile and urine [19]. Because of the ease of analysis of metabolites in these biofluids, this approach has been adopted as a biomarker of exposure and effects [20,21].…”

Docking and QSAR study on the binding interactions between polycyclic aromatic hydrocarbons and estrogen receptor

“…Humans and animals are exposed to PAHs from environmental (air, soil, water), dietary and occupational sources, and also from cigarette smoke (vanSchooten et al, 1997;Watson and Brandt, 2003). Hydroxy-substituted polycyclic aromatic hydrocarbons (HOPAHs) are formed from the corresponding PAHs in the presence of cytochrome P450 enzymes (CYPs) in humans and in animals, as well as chemically in the atmosphere.…”