Relationship between radical generation by urban ambient particulate matter and pulmonary function of school children

The mechanisms by which particulate matter (PM) produces adverse effects on the respiratory system, such as pulmonary dysfunction in children, are largely unknown. However, oxidative stress is thought to play an important role. Various chemical compounds in ambient particulate matter, including transition metals and aromatic organic compounds, may contribute to adverse effects through intrinsic generation of reactive oxygen species (ROS). It was hypothesized that ROS generation by PM, as determined through electron spin resonance (ESR) spectroscopy, may be negatively associated with pulmonary function in school children. PM(2.5), PM(10), and total suspended particulates (TSP) were sampled at the playgrounds of six elementary schools in the city of Maastricht, the Netherlands. All children (8-13 yr) from the six schools were asked to undergo spirometry. Multivariate linear regression models were constructed to evaluate associations between oxygen radical formation by PM and lung function. The radical-generating capacity per microgram PM correlated negatively to forced expiratory volume in 1 s (FEV(1)) and forced expiratory flow at 50% (FEF(50%)) of forced vital capacity (FVC). The data indicate that chemical features that contribute to intrinsic generation of ROS may be relevant for PM risk assessment.     

Benzo[a]pyrene diones are produced by photochemical and enzymatic oxidation and induce concentration-dependent decreases in the proliferative state of human pulmonary epithelial cells

Organic components within mixtures of combustion-derived materials may play an important role in the correlation between air pollution and adverse cardio/respiratory health. One class of these organic components, polycyclic aromatic hydrocarbons (PAHs), has been shown to produce a wide variety of adverse health effects. An air toxic and a model PAH, benzo[a]pyrene (BaP), is a component of combustion-derived particulate matter (PM). Although most biological effects associated with BaP have been attributed to the cytochrome P-450 derived BaP 7,8-diol 9,10-epoxide, many other BaP oxidation products are formed in atmospheric and biological reactions and may contribute to PAH-induced adverse health effects. In an ambient environment, BaP and other PAHs undergo oxidation in the presence of ultraviolet light, O(2), O(3), NO(2), or OH(*). Biological peroxidase- and P-450 mediated conversion of BaP produces an extensive metabolic profile of BaP oxidation products that significantly outnumber the 7,8-diol/diol epoxide. The data herein show that in addition to near-ultraviolet light and P-450 isozymes, lactoperoxidase (airway peroxidase) converted BaP into a mixture of three diones, the 1,6-, 3,6-, and 6,12-BaP dione (BPD). In addition, it was found that low concentrations of BPDs induced a concentration-dependent decrease in the proliferation state of human pulmonary epithelial cells in vitro. Nanomolar concentrations of BPDs mediated cell growth inhibition, which was partially reversed by co-incubation with N-acetyl-L-cysteine and ascorbate. BPDs induced the formation of reactive oxygen species as measured by the fluorophore 2,7-dichloro-fluorescein. Together, these results may indicate a role for PAH oxidation products (PAH diones) in the adverse health effects associated with combustion-derived PM and semivolatile organic compounds.     

Assessment of toxicity and mutagenicity in air particulate matter from an urban industrial area in the coast of the Rio de la Plata

Chemical characterization and effects assessment of semivolatile organic compounds in organic extracts from air particulate matter from the region of the greater La Plata area was undertaken. Effects covered the study of mutagenicity with the Ames test (Salmonella typhimurium TA100 and TA98 strains with metabolic activation by S9) and cytotoxicity using the Tetrahymena pyriformis test system (growth rate, cell volume, and cell respiration). Chemical analysis of organic extracts was done using gas chromatography. Results demonstrate the presence of polycyclic aromatic hydrocarbons (PAH) in the matrix, high mutagenicity, and cytotoxicity. A higher mutagenic activity detected with TA98 and TA100 strains is associated with an increment of total PAH and total five or six ring PAH content, respectively. Linked with it, a PAH dependent toxicity on Tetrahymena pyriformis has been observed. This cell system proved to be very sensitive. From the results obtained with the cell respiration assay with T. pyriformis it appears that uncoupling agents are present in the samples. The results of this study indicate that air particulate matter from the Rio de La Plata area contains significant genotoxic and cytotoxic activity probably due to the presence of PAHs.     

Gene expression induction of volatile organic compound and/or polycyclic aromatic hydrocarbon-metabolizing enzymes in isolated human alveolar macrophages in response to airborne particulate matter (PM2.5)

To contribute to improve the knowledge of the underlying mechanisms of action involved in air pollution particulate matter (PM)-induced cytotoxicity, we were interested in the metabolic activation of volatile organic compounds (VOC) and/or polycyclic aromatic hydrocarbons (PAH) coated onto Dunkerque City's PM2.5 in human alveolar macrophages (AM) isolated from bronchoalveolar lavage fluid (BALF). This in vitro cell lung model is closer to the normal in vivo situation than other lung cell lines, notably in the characteristics that AM display in terms of gene expression of phase I and phase II-metabolizing enzymes. The bronchoscopic examinations and BAL procedures were carried out without any complications. After 24, 48 and 72h of incubation, calculated lethal concentrations at 10% and 50% of collected airborne PM were 14.93microg PM/mL and 74.63microg PM/mL, respectively, and indicated the higher sensibility of such target lung cells. Moreover, VOC and/or PAH coated onto PM induced gene expression of cytochrome P450 (cyp) 1a1, cyp2e1, nadph quinone oxydo-reductase-1, and glutathione S-transferase-pi 1 and mu 3, versus controls, suggesting thereby the formation of biologically reactive metabolites. In addition, these results suggested the role of physical carrier of carbonaceous core of PM, which can, therefore, increase both the penetration and the retention of attached-VOC into the cells, thereby enabling them to exert a longer induction. Hence, we concluded that the metabolic activation of the very low doses of VOC and/or PAH coated onto Dunkerque City's PM2.5 is one of the underlying mechanisms of action closely involved in its cytotoxicity in isolated human AM in culture.     

粒径小于2．5微米可吸入颗粒物的危害

大量流行病学研究证明,心血管系统疾病和呼吸系统疾病的发病率、入院率、病死率与室外空气污染呈显著的正相关关系,特别与直径≤2．5μm和≤10μm的颗粒物（相应地以PM25和PM10表示）浓度相关。PM25的粒径小、比表面积大,易于富集空气中的有毒有害物质,更容易富集重金属元素及挥发性有机物（VOC）、多环芳烃（PAH）,可以随着人的呼吸进人气管、支气管,甚至穿过气血屏障,进入血液循环,广泛分布于体内器官和组织,加重或导致各种疾病。本文就颗粒物PM25;的理化性质和进人体内的方式,以及引起呼吸系统、心血管系统疾病的发病机制和造成细胞的遗传毒性机制作一综述。     

UVA photoirradiation of retinyl palmitate--formation of singlet oxygen and superoxide, and their role in induction of lipid peroxidation

We have previously reported that photoirradiation of retinyl palmitate (RP) in ethanol with UVA light results in the formation of photodecomposition products, including 5,6-epoxy-RP and anhydroretinol (AR). Photoirradiation in the presence of a lipid, methyl linoleate, induced lipid peroxidation, suggesting that reactive oxygen species (ROS) are formed. In the present study, we employ an electron spin resonance (ESR) spin trap technique to provide direct evidence as to whether or not photoirradiation of RP by UVA light produces ROS. Photoirradiation of RP by UVA in the presence of 2,2,6,6-tetramethylpiperidine (TEMP), a specific probe for singlet oxygen, resulted in the formation of TEMPO, indicating that singlet oxygen was generated. Both 5,5-dimethyl N-oxide pyrroline (DMPO) and 5-tert-butoxycarbonyl 5-methyl-1-pyrroline N-oxide (BMPO) are specific probes for superoxide. When photoirradiation of RP was conducted in the presence of the DMPO or BMPO, ESR signals for DMPO-*OOH or BMPO-*OOH were obtained. These results unambiguously confirmed the formation of superoxide radical anion. Consistent with a free radical mechanism, there was a near complete and time-dependent photodecomposition of RP and its photodecomposition products. ESR studies on the photoirradiation of 5,6-epoxy-RP and AR indicate that these compounds exhibit similar photosensitizing activities as RP under UVA light.     

Particle-associated organic compounds and symptoms in myocardial infarction survivors

CONTEXT: The aerosol components responsible for the adverse health effects of the exposure to particulate matter (PM) have not been conclusively identified, and there is especially little information on the role of particulate organic compounds (POC). Objective: This study evaluated the role of PM and POC with regard to daily symptoms. Methods: One hundred and fifty-three myocardial infarction survivors from Augsburg, Germany, recorded daily occurrence of different symptoms in winter 2003/2004. Ambient concentrations of PM with a diameter <2.5 μm (PM(2.5)), particle number concentration (PNC), PM(2.5)-bound hopanes, and polycyclic aromatic hydrocarbons (PAH) were quantified. Data were analyzed using generalized estimating equations adjusting for meteorological and other time-variant confounders. Results: The odds for avoidance of physically demanding activities due to heart problems increased immediately associated with most POC measures (e.g. 5% per 1.08 ng/m(3) increase in benzo[a]pyrene, 95%-confidence interval (CI):1-9%) and tended to a delayed decrease. After a 2-day delayed decrease associated with hopanes, the odds for shortness of breath increased consistently after 3 days with almost all POC measures (e.g. 4% per 0.21 ng/m(3) increase in 17α(H), 21β(H)-hopane, CI: 1-8%). The odds for heart palpitations marginally increased immediately in association with PNC (8% per 8146 cm(-3) increase in PNC, CI: 0-16%). Conclusions: The study showed an association between PM, particle-bound POC, and daily symptoms. The organic compounds may be causally related with cardiovascular health or act rather as indicators for traffic- and combustion-related particles.     

Pro‐inflammatory response and oxidative stress induced by specific components in ambient particulate matter in human bronchial epithelial cells

Previous studies have shown that biological effect of particulate matter (PM2.5) is involved in including chemical composition and mass concentration, but the precise components and biological action on human bronchial epithelial cell line (BEAS‐2B) are still unclear. The aim of this study was to evaluate the in vitro toxicity of PM2.5 collected at six urban sites in China, and to investigate how particle composition affects cytotoxicity. We used human bronchial epithelial (BEAS‐2B) cell lines as model in vitro to expose to PM2.5 from different source, and then reactive oxygen species (ROS), superoxide dismutase activity and total antioxidant capacity were analyzed. Furthermore, we estimated the polycyclic aromatic hydrocarbon (PAH) and transition metal and the endotoxin contents. The mRNA expression of IL‐1β and IL‐10 following exposure to PM2.5 was measured by QRT‐PCR. We also observed the mitochondrial membrane potential (MMP) using JC‐1 staining, and apoptosis of BEAS‐2B using flow cytometry. In addition, double‐stranded DNA breaks (DSBs) were assessed using γ‐H2AX immunofluorescence. Our results show that high concentrations of PAHs and elemental Ni were strongly associated with high apoptosis rates and high expression of IL‐1β, in addition, Fe element was associated with the ROS level, furthermore, Fe and Cr element were associated with DNA damage in BEAS‐2B cells. The cytotoxic effects of urban PM2.5 derived from six different cities in China appear dependent on the specific components in each. Our results indicate that air quality standards based on PM2.5 components may be more relevant than concentration–response functions (CRF). © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 923–936, 2016.     

Polycyclic aromatic hydrocarbon (PAH) o-quinones produced by the aldo-keto-reductases (AKRs) generate abasic sites, oxidized pyrimidines, and 8-oxo-dGuo via reactive oxygen species

Reactive and redox-active polycyclic aromatic hydrocarbon (PAH) o-quinones produced by Aldo-Keto Reductases (AKRs) have the potential to cause depurinating adducts leading to the formation of abasic sites and oxidative base lesions. The aldehyde reactive probe (ARP) was used to detect these lesions in calf thymus DNA treated with three PAH o-quinones (BP-7,8-dione, 7,12-DMBA-3,4-dione, and BA-3,4-dione) in the absence and presence of redox-cycling conditions. In the absence of redox-cycling, a modest amount of abasic sites were detected indicating the formation of a low level of covalent o-quinone depurinating adducts (>3.2 x 10(6) dNs). In the presence of NADPH and CuCl2, the three PAH o-quinones increased the formation of abasic sites due to ROS-derived lesions destabilizing the N-glycosidic bond. The predominant source of AP sites, however, was revealed by coupling the assay with human 8-oxoguanine glycosylase (hOGG1) treatment, showing that 8-oxo-dGuo was the major lesion caused by PAH o-quinones. The levels of 8-oxo-dGuo formation were independently validated by HPLC-ECD analysis. Apyrimidinic sites were also revealed by coupling the assay with Escherichia coli (Endo III) treatment showing that oxidized pyrimidines were formed, but to a lesser extent. Different mechanisms were responsible for the formation of the oxidative lesions depending on whether Cu(II) or Fe(III) was used in the redox-cycling conditions. In the presence of Cu(II)-mediated PAH o-quinone redox-cycling, catalase completely suppressed the formation of the lesions, but mannitol and sodium benzoate were without effect. By contrast, sodium azide, which acts as a *OH and 1O2 scavenger, inhibited the formation of all oxidative lesions, suggesting that the ROS responsible was 1O2. However, in the presence of Fe(III)-mediated PAH o-quinone redox-cycling, the *OH radical scavengers and sodium azide consistently attenuated their formation, indicating that the ROS responsible was *OH.     

Traffic air pollution and risk of death from ovarian cancer in Taiwan: fine particulate matter (PM2.5) as a proxy marker

The relationship between mortality attributed to ovarian cancer and exposure to ambient air pollutants was examined using an ecological design. The study areas consisted of 61 municipalities in Taiwan. Air quality data for recorded concentrations of fine particulate matter (PM2.5) from study municipalities for 2006-2009 were obtained as a marker of traffic emissions. These were used as a proxy for polycyclic aromatic hydrocarbons (PAH) exposure. Age-standardized mortality rates for ovarian cancer were calculated for the study municipalities for the years 1999-2008. A weighted multiple regression model was employed to calculate the adjusted risk ratio (RR) in relation to PM2.5 levels. After adjusting for urbanization level and fertility rate, the adjusted RR values (95% confidence interval [CI]) for ovarian cancer were 1.2 (1.02-1.41) for the municipalities with PM2.5 levels between 30.48 μg/m3 and 39.41 μg/m3 and 1.2 (1.03-1.39) for the municipalities with PM2.5 levels between 39.48 μg/m3 and 51.1 μg/m3, compared to the municipalities with PM2.5 levels less than 30.39 μg/m3. Results showed that individuals who resided in municipalities with higher levels of PM2.5, a proxy measure of PAH, were at an increased risk of death from ovarian cancer compared to those subjects living in municipalities with the lowest PM2.5. The findings of this study warrant further investigation into the role of exposure to air pollutants in the etiology of ovarian cancer development.     

Reactive oxygen species-dependent transient induction of genotoxicity by retene in human liver HepG2 cells

Retene is a polycyclic aromatic hydrocarbon (PAH) emitted mainly by biomass combustion, and despite its ubiquity in atmospheric particulate matter (PM), studies concerning its potential hazard to human health are still incipient. In this study, the cytotoxicity and genotoxicity of retene were investigated in human HepG2 liver cells. Our data showed that retene had minimal effect on cell viability, but induced DNA strand breaks, micronuclei formation, and reactive oxygen species (ROS) formation in a dose- and time-dependent manner. Stronger effects were observed at earlier time points than at longer, indicating transient genotoxicity. Retene activated phosphorylation of Checkpoint kinase 1 (Chk1), an indicator of replication stress and chromosomal instability, which was in accordance with increased formation of micronuclei. A protective effect of the antioxidant N-acetylcysteine (NAC) towards ROS generation and DNA damage signaling was observed, suggesting oxidative stress as a key mechanism of the observed genotoxic effects of retene in HepG2 cells. Altogether our results suggest that retene may contribute to the harmful effects caused by biomass burning PM and represent a potential hazard to human health.     

Endotoxin and polycyclic aromatic hydrocarbons in ambient fine particulate matter from Fresno,California initiate human monocyte inflammatory responses mediated by reactive oxygen species

In urban areas, a correlation between exposure to particulate matter (PM) from air pollution and increased cardiovascular morbidity and mortality has been observed. Components of PM include bacterial contaminants, transition metals, salts, polycyclic aromatic hydrocarbons (PAH), and carbonaceous material, which could interact with various cell types to produce systemic responses when inhaled. We examined the effects of PM collected from Fresno, California on activation of human monocytes and their interaction with vascular endothelium, a key event in atherogenesis. PM exposure increased cytokine expression and secretion from monocytes and enhanced monocyte adhesion to human aortic endothelial cells, both of which were attenuated by neutralizing endotoxin. PM also increased monocyte CYP1a1 expression, and inhibition of the aryl hydrocarbon receptor reduced the CYP1a1 and inflammatory responses. PM-treated monocytes accumulated intracellular reactive oxygen species (ROS), and antioxidants attenuated inflammatory and xenobiotic responses. Finally, supernatants from PM-treated pulmonary microvascular endothelial cells induced monocyte inflammatory responses that were not a consequence of endotoxin transfer. These results suggest that certain components of urban PM, namely endotoxin and PAH, activate circulating monocytes directly or indirectly by first stimulating other cells such as pulmonary endothelial cells, providing several mechanisms by which PM inhalation could induce pulmonary and/or systemic inflammation.     

Toxicological effects of emission particles from fossil- and biodiesel-fueled diesel engine with and without DOC/POC catalytic converter

There is increasing demand for renewable energy and the use of biodiesel in traffic is a major option when implying this increment. We investigated the toxicological activities of particulate emissions from a nonroad diesel engine, operated with conventional diesel fuel (EN590), and two biodiesels: rapeseed methyl ester (RME) and hydrotreated fresh vegetable oil (HVO). The engine was operated with all fuels either with or without catalyst (DOC/POC). The particulate matter (PM(1)) samples were collected from the dilution tunnel with a high-volume cascade impactor (HVCI). These samples were characterized for ions, elements, and polycyclic aromatic hydrocarbon (PAH) compounds. Mouse RAW264.7 macrophages were exposed to the PM samples for 24 h. Inflammatory mediators, (TNF-α and MIP-2), cytotoxicity, genotoxicity, and oxidative stress (reactive oxygen species [ROS]) were measured. All the samples displayed mostly dose-dependent toxicological activity. EN590 and HVO emission particles had larger inflammatory responses than RME-derived particles. The catalyst somewhat increased the responses per the same mass unit. There were no substantial differences in the cytotoxic responses between the fuels or catalyst use. Genotoxic responses by all the particulate samples were at same level, except weaker for the RME sample with catalyst. Unlike other samples, EN590-derived particles did not significantly increase ROS production. Catalyst increased the oxidative potential of the EN590 and HVO-derived particles, but decreased that with RME. Overall, the use of biodiesel fuels and catalyst decreased the particulate mass emissions compared with the EN590 fuel. Similar studies with different types of diesel engines are needed to assess the potential benefits from biofuel use in engines with modern technologies.     

Effects of nitrosation on the chemical composition and epidermal carcinogenicity of the nitrogen-rich fraction of a high-boiling coal liquid

An 800-850 degrees F solvent-refined coal-II liquid was fractionated into chemical classes to obtain the aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAH), nitrogen-containing polycyclic aromatic compounds (NPAC), and hydroxy-substituted PAH (hydroxy-PAH). The isolated NPAC fraction was refractionated by chemical class both before and after undergoing a nitrosation reaction. The nitrosated and non-nitrosated refractionated NPAC fractions were further subfractionated into secondary amine (pyrroles), primary amine-enriched (amino-PAH), and tertiary amine (azaarene) classes. The PAH and hydroxy-PAH composition of the NPAC fraction increased upon nitrosation, whereas the amino-PAH fraction composition decreased upon nitrosation. Nitrosation of standards indicated the amino-PAH compounds reacted to form parent PAH, chloro-substituted PAH, and methoxy-substituted PAH when analyzed by high-resolution gas chromatography (GC) and GC/mass spectrometry (MS). Some easily oxidized PAH compounds reacted to form ketones and quinones. All other standard reference compounds, chosen to be representative of the major chemical classes of compounds present in coal liquefaction materials, were unchanged by the nitrosation reaction. The amino-PAH of the nitrosated NPAC fraction reacted to form parent and some chloro-substituted PAH when analyzed by low-voltage direct-probe MS in addition to the methods given above. Epidermal carcinogenesis studies with the PAH, NPAC, nitrosated NPAC, and hydroxy-PAH fractions isolated from the 800-850 degrees F coal liquid indicated the PAH and NPAC were the most important determiners of skin carcinogenesis, with the PAH giving a higher response than the NPAC. The tumorigenicity of the NPAC was drastically reduced by nitrosation, probably due to the destruction of the amino-PAH upon nitrosation.     

Protection by uridine diphosphoglucuronic acid and DT-diaphorase against the cytotoxicity of polycyclic aromatic hydrocarbons isolated from a complex coal gasification condensate

The cytotoxicities of polycyclic aromatic hydrocarbon (PAH) subclasses isolated from a complex organic mixture (coal gasification condensate) were studied in vitro in Chinese hamster ovary cells, in the presence of rat liver microsomes from animals pretreated with Aroclor. Toxicity was enhanced by microsomal metabolism and was inversely related to aromatic ring number. Rat liver cytosol, semipurified DT-diaphorase, and uridine diphosphoglucuronic acid decreased the cytotoxicity of a variety of PAH mixtures and representative PAH, as well as individual PAH metabolites. The results indicate that the in vitro toxicity of complex PAH mixtures is caused primarily by hydroxy-PAH and quinone metabolites of the predominant, nonmutagenic two- and three-ring PAHs.     

Particle-associated organic compounds and symptoms in myocardial infarction survivors

Context: The aerosol components responsible for the adverse health effects of the exposure to particulate matter (PM) have not been conclusively identified, and there is especially little information on the role of particulate organic compounds (POC).

Objective: This study evaluated the role of PM and POC with regard to daily symptoms.

Methods: One hundred and fifty-three myocardial infarction survivors from Augsburg, Germany, recorded daily occurrence of different symptoms in winter 2003/2004. Ambient concentrations of PM with a diameter <2.5 μm (PM_2.5), particle number concentration (PNC), PM_2.5-bound hopanes, and polycyclic aromatic hydrocarbons (PAH) were quantified. Data were analyzed using generalized estimating equations adjusting for meteorological and other time-variant confounders.

Results: The odds for avoidance of physically demanding activities due to heart problems increased immediately associated with most POC measures (e.g. 5% per 1.08?ng/m³ increase in benzo[a]pyrene, 95%-confidence interval (CI):1–9%) and tended to a delayed decrease. After a 2-day delayed decrease associated with hopanes, the odds for shortness of breath increased consistently after 3 days with almost all POC measures (e.g. 4% per 0.21?ng/m³ increase in 17α(H), 21β(H)-hopane, CI: 1–8%). The odds for heart palpitations marginally increased immediately in association with PNC (8% per 8146?cm^?3 increase in PNC, CI: 0–16%).

Conclusions: The study showed an association between PM, particle-bound POC, and daily symptoms. The organic compounds may be causally related with cardiovascular health or act rather as indicators for traffic- and combustion-related particles.     

Formation of polycyclic aromatic hydrocarbons from tobacco: the link between low temperature residual solid (char) and PAH formation.

The formation of condensed ring polycyclic aromatic hydrocarbons (PAHs) from the pyrolysis of ground tobacco in helium over the temperature range of 350-600 degrees C was investigated. PAH yields in the ng/g range were detected and the maximum yields of all PAHs studied including benzo[a]pyrene (B[a]P) and benzo[a]anthracene (B[a]A) occurred between 500 and 550 degrees C. The pathway to PAH formation in the 350-600 degrees C temperature range is believed to proceed via a carbonization process where the residual solid (char) undergoes a chemical transformation and rearrangement to give a more condensed polycyclic aromatic structure that upon further heating evolves PAH moieties. Extraction of tobacco with water led to a two fold increase in the yields of most PAHs studied. The extraction process removed low temperature non-PAH-forming components, such as alkaloids, organic acids and inorganic salts, and concentrated instead (on a per unit weight basis) tobacco components such as cell wall bio-polymers and lipids. Hexane extraction of the tobacco removed lipophilic components, previously identified as the main source of PAH precursors, but no change in PAH yields was observed from the hexane-extracted tobacco. Tobacco cell wall components such as cellulose, hemicellulose, and lignin are identified as major low temperature PAH precursors. A link between the formation of a low temperature char that evolves PAHs upon heating is established and the observed ng/g yields of PAHs from tobacco highlights a low temperature solid phase formation mechanism that may be operable in a burning cigarette.     

Effects of ascorbic acid on the free radical formations of isoniazid and its metabolites]

By the use of electron spin resonance (ESR) spectroscopy and of spin-trapping technique, the effects of ascorbic acid on the formation of the free radical intermediates due to isoniazid (INAH) and its metabolites were investigated with a microsomal system. When alpha-(4-pyridyl 1-oxide)-N-tert butylnitrone (4-POBN) was used as a spin trapping agent, the ESR signal due to hydrazine (Hy) was formed to be most intensive among others. Therefore, it was presumed that Hy is a potent intermediate to cause an INAH-induced hepatic injury. In the presence of ascorbic acid (AA), the free radical formation of Hy, INAH and acetyl hydrazine was significantly inhibited, suggesting that AA may affect the INAH-hepatitis. By the addition of inhibitors of cytochrome P-450 like metyrapone and CO, the generation of the radical from Hy decreased, confirming that the radical is formed by the cytochrome P-450 dependent microsome systems. The 4-POBN-trapped radical species generated from Hy was presumed to be the hydrazyl radical by the results of mass spectrometry.     

Enzymatic and nonenzymatic production of free radicals from the carcinogens 4-nitroquinoline N-oxide and 4-hydroxylaminoquinoline N-oxide.

The anion radicals of 4-nitroquinoline N-oxide (4-NQO) and 4-nitrosoquinoline N-oxide (4-NOQO) carcinogens were detected and characterized by electron spin resonance (ESR) spectroscopy. The structures of the radical intermediates were examined by density functional theory (DFT) at the level of hybrid unrestricted uBecke3LYP. The formation of superoxide anion radical catalyzed by flavin-containing enzymes such as cytochrome P450 reductase or xanthine oxidase in the presence of 4-NQO or 4-nitroquinoline N-oxide was studied by spin-trapping experiments. In this case, the ESR signal of the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-superoxide radical adduct was observed, and its formation was inhibited by superoxide dismutase (SOD). No ESR signal was detected when the two-electron-transferring flavoenzyme DT-diaphorase (NADPH-quinone oxidoreductase) was used. The above is consistent with a one-electron reduction in the metabolism of these nitro compounds to anion free radicals by various flavoenzyme reductases.     

Determination of the Size Distribution and Chemical Composition of Fine Particulate Semivolatile Organic Material in Urban Environments Using Diffusion Denuder Technology

Abstract

Collection of particles on a filter results in underestimation of particulate organic compounds due to losses from the semivolatile organic fraction during sample collection, that is, a “negative sampling artifact.” This sampling-induced change in the phase distribution of semivolatile organic material resulted in the loss of an average of 35% of the particulate organic material in samples collected at the South Coast Air Quality Management District (SCAQMD) sampling site at Azusa, CA, in the Los Angeles Basin. These semivolatile organic compounds lost from particles were measured using two diffusion denuder sampling systems. A multichannel diffusion denuder sampling system (BOSS) was used to determine the concentrations of fine particulate carbonaceous material, and a multisystem, multichannel, high-volume diffusion denuder sampler (BIG BOSS) was used for the determination of the particle size distribution and chemical composition of semivolatile organic compounds in fine particles. Results obtained with the two sampling systems agreed. A smaller artifact associated with the absorption of gas-phase organic compounds by the filter during sampling was corrected for using two tandem quartz filters in the BOSS sampling system. The quartz filter artifact was not present after removal of gas-phase compounds by the diffusion denuder. Comparison of the denuder results with those obtained by the SCAQMD using filter pack sampling systems showed that the observed concentration of the quartz filter artifact was dependent on the sample flow rate. However, the denuder sampler results on the concentration of particulate carbonaceous material retained on a quartz filter during sampling, corrected for the quartz filter artifact, were also in agreement with results reported by the SCAQMD. The loss of semivolatile organic material from particles during sampling resulted in an underestimation of particulate organic material by collection with tandem quartz filters by an average of 55% of the measured concentration. Semivolatile particulate organic compounds lost from the particles during sample collection included paraffinic compounds, aromatic compounds, and organic acids and esters. Underestimation of the concentration of semivolatile organic compounds in particles is a function of molecular weight, chemical compound class, and particle size. The maJority of the organic compounds in fine particles 0.8–2.5 μm in size are semivolatile organic compounds lost from the particles during sampling onto a filter. The maJority of carbonaceous material in particles smaller than 0.4 μm is not lost from the particles during sample collection. The results obtained using the diffusion denuder sampling systems indicate that the fine particulate organic constituents to which an urban population is exposed have not been well characterized or quantified in previous studies.