Generation and characterization of condensation aerosols of benzo[alpha]pyrene

Distribution to the fetus and major organs of the rat following inhalation exposure to pyrene

Concentrations of pyrene and total metabolites were determined for individual fetuses and selected maternal organs and tissues immediately and 6 h following a 95-min head-only exposure of pregnant Wistar rats, on gestation day 17, to five levels of pyrene over the range 200-800 mg m-3 as a microcondensation aerosol. The influence of uterine horn, side and position, on distribution to the fetus was assessed. The concentration of both pyrene and its metabolites increased more over the exposure range (eightfold) than did those in the fetus. Concentrations of pyrene or its metabolites in fetal tissues were not found to be related to its position on the uterine horn. There was an unexplained and significant (P less than 0.01) higher concentration of pyrene in fetuses on the right side relative to the left side of the uterine horn for the animals killed immediately following exposure. A comparison of the levels in maternal tissues measured immediately following the exposure and 6 h later showed that there was some redistribution of pyrene and its metabolites to the fat tissues, i.e. levels in the fat increased over the 6 h period following the exposure. Levels in the other tissues diminished during this period. In general, concentrations of pyrene and its metabolites were lowest in the fetal tissues relative to those in the sampled maternal organs and tissues.

Lung retention and binding of [14C]-1-nitropyrene when inhaled by F344 rats as a pure aerosol or adsorbed to carbon black particles

1-Nitropyrene (NP), as found in the environment, is more typically associated with carbonaceous particles than found as an aerosol of the pure compound. To determine whether (and why) an association with particles resulted in prolonged lung retention of NP, rats were exposed to 14C-NP as a pure aerosol or adsorbed on carbon black particles. Total 14C retained in the lung was greater at all times from 0.5 h to 30 d after exposure to 14C-NP adsorbed to carbon black particles than after exposure to pure 14C-NP (p less than .05). The fraction of total 14C in lung bound to carbon black particles decreased steadily with time after exposure, indicating in vivo removal of NP from the particles. At 0.5 h after exposure, the fraction of the estimated deposited 14C that was covalently bound to lung macromolecules was twofold greater for NP adsorbed on carbon black than for pure NP. Covalently bound 14C in lungs increased with time after exposure to 14C-NP adsorbed to carbon black, reaching levels of approximately 1% of the deposited radioactivity at 7-30 d after exposure, whereas levels of covalently bound 14C declined with time after exposure to pure NP. Thus, at 30 d after exposure, the amount of 14C covalently bound to lung macromolecules was approximately 10-fold greater (p less than .05) in rats that inhaled 14C-NP adsorbed on carbon black particles than in rats that inhaled pure 14C-NP aerosols. These results suggest that association of NP with carbon black particles augments the interaction of reactive metabolites of NP with target macromolecules. This phenomenon is thought to be related to the slow release of NP from carbon black particles, and may augment the biological effects of inhaled NP when adsorbed on carbon black or similar particles in the environment.

Effects of adsorption of benzo[a]pyrene onto carbon black particles on levels of DNA adducts in lungs of rats exposed by inhalation

Exposure of rodents to benzo[a]pyrene (BaP) associated with particles has previously been shown to result in increased retention of BaP and metabolites in lungs. To determine if DNA damage might be enhanced, DNA adducts were measured in lungs of F344 rats following inhalation of pure BaP aerosols or BaP absorbed on carbon black particles. Groups of rats were exposed nose only to filtered air, [14C]BaP (2 mg/m3), or [14C]BaP (2 mg/m3) adsorbed on carbon black (97 mg/m3) (BaP/CB) for 4 hr/day, 1 day/week, for 12 weeks. Groups of rats were terminated at 4, 8, 12, 16, 20, and 24 weeks after the beginning of the 12-week exposure period. Retention of total 14C in lungs was used as an indicator of total reactive metabolites. DNA isolated from lungs was analyzed for adducts using a 32P-postlabeling assay. Inhalation of BaP/CB resulted in 100-fold higher levels of 14C in lungs at the end of the 12-week exposure than did inhalation of pure BaP. The halftime for the decline in 14C levels was 34 +/- 3 weeks (mean +/- SE) for rats exposed to BaP/CB and 6 +/- 2 weeks for rats exposed to pure BaP. At the end of 12 weeks of exposure, DNA adducts in lungs of rats exposed to pure BaP ranged from 2-15 adducts per 10(9) bases (mean = 7, n = 4) and in rats exposed to pure BaP absorbed on carbon black ranged from 10-12 adducts per 10(9) bases (mean = 11, n = 4); DNA adducts in lungs of sham-exposed rats ranged from 0-2 adducts per 10(9) bases (mean = 1, n = 4). The halftimes for the decline in DNA adducts in lungs were 3 +/- 1 weeks (mean +/- SE) for the rats exposed to BaP/CB and 5 +/- 2 weeks for the rats exposed to BaP. One of the DNA adducts found following exposure to both BaP and BaP/CB was tentatively identified as the BaP diol epoxide deoxyguanosine (BPDE) adduct. Levels of both total and BPDE DNA adducts were significantly increased (p less than 0.05) in lungs of rats exposed to both BaP and BaP/CB compared to levels in lungs of sham-exposed rats. There were no significant differences in levels of DNA adducts in lungs of rats exposed to BaP or BaP/CB, although the pattern of adducts was different between the two exposure modes.(ABSTRACT TRUNCATED AT 400 WORDS)

Polycyclic aromatic hydrocarbons of coal fly ash: analysis by gas-liquid chromatography using nematic liquid crystals

The seasonal variations over a period of 12 m in the amounts of polycyclic aromatic hydrocarbons (PAH) in fly-ash samples collected from the electrostatic precipitator of a thermal power plant have been studied. PAH generally did not show much seasonal variation. The gas-liquid chromatographic (GLC) analysis of benzene extract of fly ash showed the presence of 28 polyaromatic hydrocarbons, of which only phenanthrene, anthracene, pyrene, benz[a]anthracene, chrysene, and benzo[a]pyrene could be identified.

Distribution and elimination of inhaled phenanthridone in Fischer-344 rats

Aza-arenes are widely distributed in the environment. Certain members of this chemical class are biologically active and therefore could pose health hazards to humans if inhaled or ingested. Since inhalation is the most likely route for significant exposure for aza-arenes that are air pollutants, knowledge of the absorption, distribution, and excretion after inhalation is necessary to understand mechanisms of toxicity and predict health hazards associated with exposure to aza-arenes. In this study, rats were exposed nose-only to an aerosol of [14C]phenanthridone, a mutagenic aza-arene found in coal tar. Tissues, urine, feces, and expired air were collected at specified times and assayed for radioactivity. Radioactivity was rapidly absorbed from the respiratory tract and distributed to all tissues examined. It was rapidly eliminated from tissues (greater than 80% in 12 h), being concentrated only in the large intestine at later timepoints. Excretion of radioactivity in both feces and urine was complete within 4 d. Virtually none of the dose was eliminated as [14C]CO2. [14C] Phenanthridone was also administered orally to assess its absorption from the gastrointestinal tract. Absorption was nearly complete (83 +/- 6%), indicating that phenanthridone ingested as a result of mucociliary clearance and swallowing, grooming, or coprophagy could also contribute to tissue exposure. These results are similar to those obtained from inhalation studies of other polycyclic aromatic hydrocarbons, indicating that as a class, inhaled polycyclic aromatic hydrocarbons may be rapidly absorbed from the respiratory tract, widely distributed throughout the body, and readily eliminated in both urine and feces.

The metabolic fate of benzo[a]pyrene in rats after inhalation

Male Fischer-344 rats were exposed by inhalation to [3H]benzo[a]pyrene (BP) aerosols (100 micrograms/l; activity mass aerodynamic diameter, 1-2 microns) for 30 min. The concentration of organic-soluble, water-soluble and covalently-bound radioactivity was determined in rat lung, liver and kidney at 0.5, 6 and 24 h after exposure. The total amount of [3H] BP decreased rapidly in the lung as a function of time after exposure. At 0.5 h after exposure, the organic-soluble radioactivity accounted for approx. 70% of the total radioactivity in the lung. The organic-soluble radioactivity in the liver and kidney was 24% and 21%, respectively, at 0.5 h after exposure. The organic-soluble radioactivity decreased in the lung to approx. 10% of the total radioactivity by 1 day after exposure; the percent of total lung radioactivity bound to tissue at this time was 80%. Thin-layer chromatography (TLC) of extracts indicated that the organic-soluble radioactivity in the lung at 0.5 h after exposure was comprised primarily of BP, 3-OH-BP, 9-OH-BP and quinones of BP. In contrast, the organic-soluble radioactivity in the liver and kidney at 0.5 h after exposure were primarily polar metabolites, dihydrodiols, and BP. In all organs TLC profiles of the organic-soluble fraction at 6 h and 24 h after exposure were not significantly different from the 0.5 h organic soluble profiles except for the lower amount of BP.

Distribution and retention of benzo(A)pyrene in rats after inhalation

Tritium levels in tissues of rats were determined after inhalation of tritiated benzo(a)pyrene (3H-BaP; 500 micrograms/l; activity mass median diameter, 1-2 micrometers) for 1 h. Significant amounts of radioactivity were found in the nasal turbinates, trachea, larynx, lungs, tracheobronchial lymph nodes, kidneys, and liver immediately after exposure. Lower concentrations of radioactivity were found in the brain, testes, and spleen. Clearance of radioactivity from the respiratory tract occurred in two phases; a rapid phase where 50% of the radioactivity cleared by approx. 2 h, and a slower phase that continued for about 2 days after exposure. Radioactivity in the brain, testes, and spleen remained at about the same level during the first day after exposure and then decreased slightly during the second day. Benzo(a)pyrene inhaled in this particulate form was rapidly solubilized, translocated to internal organs, and excreted primarily in feces.