Identification of oxygenated polycyclic aromatic hydrocarbons in diesel particulate matter by capillary gas chromatography and capillary gas chromatography/mass spectrometry

Preneoplastic lesions, DNA adduct formation and mutagenicity of 5-, 7- and 9-hydroxy-2-nitrofluorene, metabolites of the air pollutant 2-nitrofluorene

The metabolites of 2-nitrofluorene (NF), 5-, 7- and 9-OH-2-nitrofluorene (OH-NF) were compared for their genotoxicity. Seventy-two hours after intraperitoneal administration of these substances individually to rats (100 mg/kg body wt.), DNA adducts in liver tissue were analyzed with 32P-TLC and 32P-HPLC. An in vivo liver model was used to test the initiating capacity of the said substances for the formation of preneoplastic lesions. 5-OH-NF showed low capacity to induce DNA adduct formation and low potential as initiator to induce preneoplastic lesions-foci/nodules in the liver of rats. Both 7- and 9-OH-NF induced DNA adducts and preneoplastic liver lesions but with smaller quantities compared to NF. It seems that 7- and 9-OH-NF can not be considered as detoxification products of NF. In general, the initiating capacity of these substances for the formation of preneoplastic lesions has a good correlation with their potency to form DNA adducts.

In vivo metabolism and genotoxic effects of nitrated polycyclic aromatic hydrocarbons

During incomplete combustion of organic matter, nitro-polycyclic aromatic hydrocarbons (nitro-PAHs), are formed in a reaction that is catalyzed by a low pH. 2-Nitrofluorene (NF), a marker for nitro-PAHs, is metabolized in vivo by two different routes. After inhalation, potent mutagenic metabolites, hydroxylated nitrofluorenes (OH-NFs), are formed. The metabolites are distributed by systemic circulation. After oral administration, NF is reduced to the corresponding amine, a reaction mediated by the intestinal microflora. This metabolite is acetylated to 2-acetylaminofluorene (AAF), a potent carcinogen. Further ring-hydroxylation of AAF leads to detoxification and excretion. Induction of cytochrome P450s affects the metabolism, and more OH-NFs are formed. As a consequence, more mutagenic metabolites are found in the circulation. OH-NFs are excreted in the bile as, in terms of mutagenicity, totally harmless glucuronide conjugates. When these conjugates are excreted via the bile, intestinal beta-glucuronidase can liberate direct-acting mutagens in the intestine. Thus, inhalation of NF can lead to formation of potent mutagens in the intestine. NF is a direct-acting mutagen in bacterial assays and an initiator and promoter of the carcinogenic process, and gives rise to DNA adduct formation in laboratory animals.

Chemical characterization of a polar portion in the neutral fraction derived from airborne particulate extracts responsible for the embryotoxicity in the chicken embryo

Airborne particulate matter was collected with a high-volume air sampler between June 1984 and May 1985 on the rooftop of our institute. The tar material extracted was separated into six fractions by liquid-liquid partition and silica gel column chromatography. These fractions were then tested for their embryotoxicities by a chicken embryo assay. A moderately polar fraction per weight and a fraction containing polycyclic aromatic hydrocarbons (PAHs) had the greatest toxicity for chicken embryos. When the polar fraction was purified by high-pressure liquid chromatography, the purified fraction was 3.7 times more toxic than the original polar fraction. To determine the responsible components for the toxicity, the purified fraction as well as the original fraction was analyzed by capillary gas chromatography and gas chromatography-mass spectrometry. The characterized components were classified into oxygenated PAHs (containing ketones, quinones, and aldehydes), nitrogen-containing PAHs, diphenyl-substituted aliphatic ketones (or diketones), and esters of aliphatic acids.