Atmospheric formation of hydroxynitropyrenes from a photochemical reaction of particle-associated 1-nitropyrene

The Kinetics and Mechanisms for Photodegradation of Nitrated Polycyclic Aromatic Hydrocarbons on Lettuce Leaf Surfaces: An In Vivo Study

Insights into the environmental fates of nitrated polycyclic aromatic hydrocarbons (NPAHs) in edible vegetables are of great significance for better evaluating human exposure to NPAHs through the dietary pathway. In this work, a fluorescence quenching method using graphene quantum dots as a fluorescent probe was first applied for the in vivo determination of 9-nitroanthracene (9-NAnt) and 1-nitropyrene (1-NPyr) adsorbed on the leaf surfaces of living lettuce (Lactuca sativa L.) seedlings. Moreover, the photolysis kinetics and mechanisms of the two adsorbed NPAHs were discussed. The photodegradation kinetics followed the pseudo-first-order equation, and the photodegradation half-life of 1-NPyr (7.4 ± 0.2 h) was greater than that of 9-NAnt (2.3 ± 0.1 h). Anthraquinone and pyrenediones were identified to be the main photolytic products of 9-NAnt and 1-NPyr, respectively. Intramolecular rearrangement was the most reasonable mechanism for the NPAH photolysis. The photolysis-driven degradation exhibited a key role in scavenging NPAHs from the vegetable leaf, indicating the reduction of NPAH transportation in the food chain.

Taurine ameliorates particulate matter-induced emphysema by switching on mitochondrial NADH dehydrogenase genes

Exposure to high levels of particulate matter (PM) poses a major threat to human health. Cigarette smoke is the most common irritant that causes chronic obstructive pulmonary disease (COPD); however, at least one-fourth of patients with COPD are nonsmokers, and their disease is largely attributed to air pollution. The occurrence of pollution episodes in China has raised an emergent question of how PM leads to the pathogenesis of COPD. In this paper, we show that deregulation of mitochondrial NADH dehydrogenase gene expression levels plays a key role in the aggravation of COPD during air pollutant exposure, which can be rescued by taurine and 3-MA treatments in both mammalian cells and animals.

Chronic obstructive pulmonary disease (COPD) has been linked to particulate matter (PM) exposure. Using transcriptomic analysis, we demonstrate that diesel exhaust particles, one of the major sources of particulate emission, down-regulated genes located in mitochondrial complexes I and V and induced experimental COPD in a mouse model. 1-Nitropyrene was identified as a major toxic component of PM-induced COPD. In the panel study, COPD patients were found to be more susceptible to PM than individuals with normal lung function due to an increased inflammatory response. Mechanistically, exposure to PM in human bronchial epithelial cells led to a decline in CCAAT/enhancer-binding protein alpha (C/EBPα), which triggered aberrant expression of NADH dehydrogenase genes and ultimately led to enhanced autophagy. ATG7-deficient mice, which have lower autophagy rates, were protected from PM-induced experimental COPD. Using metabolomics analysis, we further established that treatment with taurine and 3-methyladenine completely restored mitochondrial gene expression levels, thereby ameliorating the PM-induced emphysema. Our studies suggest a potential therapeutic intervention for the C/EBPα/mitochondria/autophagy axis in PM-induced COPD.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in the environment - A review

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are derivatives of PAHs with at least one nitro-functional group (-NO₂) on the aromatic ring. The toxic effects of several nitro-PAHs are more pronounced than those of PAHs. Some nitro-PAHs are classified as possible or probable human carcinogens by the International Agency for Research on Cancer. Nitro-PAHs are released into the environment from combustion of carbonaceous materials (e.g. fossil fuels, biomass, waste) and post-emission transformation of PAHs. Most studies on nitro-PAHs are about air (gas-phase and particulate matter), therefore less is known about the occurrence, concentrations, transport and fate of nitro-PAHs in soils, aquatic environment and biota. Studies on partition and exchange of nitro-PAHs between adjacent environmental compartments are also sparse. The concentrations of nitro-PAHs cannot easily be predicted from the intensity of anthropogenic activity or easily related to those of PAHs. This is because anthropogenic source strengths of nitro-PAHs are different from those of PAHs, and also nitro-PAHs have additional sources (formed by photochemical conversion of PAHs). The fate and transport of nitro-PAHs could be considerably different from their related PAHs because of their higher molecular weights and considerably different sorption mechanisms. Hence, specific knowledge on nitro-PAHs is required. Regulations on nitro-PAHs are also lacking. We present an extensive review of published literature on the sources, formation, physico-chemical properties, methods of determination, occurrence, concentration, transport, fate, (eco)toxicological and adverse health effects of nitro-PAHs. We also make suggestions and recommendations about data needs, and future research directions on nitro-PAHs. It is expected that this review will stimulate scientific discussion and provide the basis for further research and regulations on nitro-PAHs.

The Photochemical Branching Ratio in 1,6-Dinitropyrene Depends on the Excitation Energy

Nitropolycyclic aromatic hydrocarbons constitute one of the most disconcerting classes of pollutants. Photochemical degradation is thought to be a primary mode of their natural removal from the environment, but the microscopic mechanism leading to product formation as a function of excitation wavelength is poorly understood. In this Letter, it is revealed that excitation of 1,6-dinitropyrene with 425, 415, or 340 nm radiation leads to an increasing amount of radical production through photodissociation at the expense of triplet-state population-the two primary reaction pathways in this class of pollutants. Radical formation requires overcoming an energy barrier in the excited singlet manifold. This activation energy explains the large fraction of the initial singlet-state population that intersystem crosses to a doorway triplet state, instead of leading overwhelmingly to photodissociation. The unforeseen excitation wavelength dependence of this branching process is expected to regulate the photochemistry of 1,6-dinitropyrene and possibly of other nitroaromatic pollutants in the environment.

Environmental Behaviors and Toxicities of Polycyclic Aromatic Hydrocarbons and Nitropolycyclic Aromatic Hydrocarbons

Airborne particulate matter (PM) has been collected at four cities in Japan starting in the late 1990s, at five or more major cities in China, Korea and Russia starting in 2001 and at the Noto Peninsula starting in 2004. Nine polycyclic aromatic hydrocarbons (PAHs) and eleven nitropolycyclic aromatic hydrocarbons (NPAHs) were determined by HPLC with fluorescence and chemiluminescence detections, respectively. Annual concentrations of PAHs and NPAHs were in the order, China>Russia≫Korea=Japan, with seasonal change (winter>summer). During the observation period, concentrations of PAHs and NPAHs in Japanese cities significantly decreased but the increases in the PAH concentration were observed in Chinese and Russian cities. Concentrations of PAHs and NPAHs were higher in the Northern China than those in the Southern China. At the Noto peninsula, which is in the main path of winter northwest winds and a year-round jet stream that blow from the Asian continent to Japan, the concentrations were high in winter and low in summer every year. A cluster analysis and back trajectory analysis indicated that PAHs and NPAHs were long-range transported from Northeastern China, where coal burning systems such as coal-heating boilers are considered to be the major contributors of PAHs and NPAHs. A dramatic change in atmospheric concentrations of PAHs and NPAHs in East Asia suggests the rapid and large change of PM2.5 pollution in East Asia. Considering the adverse health effects of PM2.5, continuous monitoring of atmospheric PAHs and NPAHs is necessary in this area.

Effects of air pollution on human health and practical measures for prevention in Iran

Air pollution is a major concern of new civilized world, which has a serious toxicological impact on human health and the environment. It has a number of different emission sources, but motor vehicles and industrial processes contribute the major part of air pollution. According to the World Health Organization, six major air pollutants include particle pollution, ground-level ozone, carbon monoxide, sulfur oxides, nitrogen oxides, and lead. Long and short term exposure to air suspended toxicants has a different toxicological impact on human including respiratory and cardiovascular diseases, neuropsychiatric complications, the eyes irritation, skin diseases, and long-term chronic diseases such as cancer. Several reports have revealed the direct association between exposure to the poor air quality and increasing rate of morbidity and mortality mostly due to cardiovascular and respiratory diseases. Air pollution is considered as the major environmental risk factor in the incidence and progression of some diseases such as asthma, lung cancer, ventricular hypertrophy, Alzheimer's and Parkinson's diseases, psychological complications, autism, retinopathy, fetal growth, and low birth weight. In this review article, we aimed to discuss toxicology of major air pollutants, sources of emission, and their impact on human health. We have also proposed practical measures to reduce air pollution in Iran.

Factors affecting atmospheric 1-, 2-nitropyrenes and 2-nitrofluoranthene in winter at Noto peninsula, a remote background site, Japan

Airborne particulates were collected at a background site (Wajima Air Monitoring Station; WAMS) on the Noto Peninsula, Japan from January 2006 to December 2007. 1-, 2-nitropyrenes (1-, 2-NPs) and 2-nitrofluoranthene (2-NFR), in the particulates were determined with a sensitive HPLC method with chemiluminescence detection. The average concentrations were higher in winter than in summer. A meteorological analysis indicated that the air samples collected in winter were transported mainly from Northeast China over the Japan Sea. Both the concentration ratios of 2-NFR to 1-NP and 1-NP to pyrene were similar to those in Shenyang in Northeast China which located along the air transportation route to WAMS, but not in Kanazawa which near WAMS. These results strongly suggest that most of the atmospheric 1-, 2-NPs and 2-NFR at WAMS in winter were long range transported from Northeast China.

Assessment of nitro-polycyclic aromatic hydrocarbons in PM₁ near an area of heavy-duty traffic

The objective of this research was to evaluate nitro-polycyclic aromatic hydrocarbons (NPAHs) associated with ultrafine airborne particles (PM1) in areas affected by vehicles in the metropolitan area of Porto Alegre (MAPA), RS, Brazil. Extraction, isolation/derivatization, and subsequently gas chromatography with electron capture detection (GC/ECD) were the techniques used to extract and determine NPAHs (1-nitronaphthalene, 2-nitrofluorene,3-nitrofluoranthene,1-nitropyrene, and 6-nitrochrysene) associated with PM1 Airborne particles (PM1) were collected using PTFE filters in a PM162M automatic sampler. The analytical method was validated by the Standard Reference Material - SRM 1649 b - from the National Institute of Standards and Technology (NIST, USA). The results were consistent with the certified values. 3-NFlt and 6-NChr reached highest concentrations of 0.047 ng·m(-3) and 0.0284 ng·m(-3), respectively, in Sapucaia do Sul and Canoas. Seasonal variation showed higher NPAH concentrations in cold days. The NPAHs associated with PM1 were correlated with the pollutants nitrogen oxides and NPAHs with meteorological variables: temperature and wind speed. The results indicated that vehicles with diesel engines were influential. This was confirmed by the study of the ratios NPAHs/PAHs, 1-NPyr/Pyr, and 6-NChr/Chr.

Phototransformations of dinitropyrene isomers on models of the atmospheric particulate matter

The 1,6 and 1,8-dinitropyrenes (DNP) isomers are strong mutagens and carcinogens encountered in diesel exhaust and airborne particles. Relative photodegradation rates were determined and some products were characterized when these isomers were irradiated adsorbed onto models of the atmospheric matter. These are compared to their photochemical behavior in a polar nonprotic solvent. The 1,8-DNP isomer is three times more reactive than the 1,6-DNP when irradiated adsorbed onto silica gel surfaces, while the reverse order is observed in solution, demonstrating the influence of structural differences and environmental effects on the photoreactivity. Oxygen is a key factor in the formation of pyrenediones from 1,8-DNP in solution and on silica gel which is not the case for 1,6-DNP. The average pore diameter (2.5 versus 6.0 nm) of the silica surfaces induces a significant change in the product distribution and relative yields of 1,8-DNP because pyrenediones or 8-hydroxy-1-nitropyrene are not produced in the smaller pore silica. A 6-hydroxy-1-nitropyrene product is observed both in acidic alumina and silica (6.0 nm) surfaces. On acidic alumina the rates of phototransformation of the isomers are equal, a significant increase in the relative yield of the hydroxynitropyrene product is observed compared to the silica and unidentified products in which the absence of NO₂ and pyrene absorption bands were observed, demonstrating the surface effect on the photodegradation. Overall, the presence of some products indicates the occurrence of a nitro-nitrite rearrangement on the surface with the participation of a pyrenoxy radical as their precursor.

Biological effects of polycyclic aromatic hydrocarbon derivatives

Polycyclic aromatic hydrocarbons (PAHs) are included in various environmental pollutants such as airborne particles and have been reported to induce a variety of toxic effects. On the other hand, PAH derivatives are generated from PAHs both through chemical reaction in the atmosphere and metabolism in the body.PAH derivatives have become known for their specific toxicities such as estrogenic/antiestrogenic activities and oxidative stress, and correlations between the toxicities and structures of PAH derivatives have been shown in recent studies. These studies are indispensable for demonstrating the health effects of PAH derivatives, since they would contribute to the comprehensive toxicity prediction of many kinds of PAH derivatives.

Structure-dependent lipid peroxidation by photoirradiation of pyrene and its mono-substituted derivatives

Pyrene, one of the most studied polycyclic aromatic hydrocarbons, can damage biological macromolecules and cause toxicity when irradiated by light. The effect of substituents, 1-amino, 1-hydroxy, 1-nitro, and 1-bromo, on light-induced lipid peroxidation is studied. Degradation kinetics and photoproduct analyses were conducted to test how these substituents affect the photoreaction. All five compounds have widely different photodegradation rates, with degradation half-lives, ranging from 8 min to 495 min. These rates parallel their light absorptivity. Four out of the five compounds induce lipid peroxidation when irradiated with UVA light, whereas 1-aminopyrene causes minimum or no lipid peroxidation. The relative amount of lipid peroxidation caused is: 1-bromopyrene > pyrene > 1-nitropyrene ≈ 1-hydroxypyrene > 1-aminopyrene. This relative lipid peroxidation is dependent on the substituent due to the following factors: light absorptivity, relative rates of the competing processes in the excited states, nature of the photoreaction, and nature of the photoproducts.

Photodegradation mechanisms of 1-nitropyrene, an environmental pollutant: the effect of organic solvents, water, oxygen, phenols, and polycyclic aromatics on the destruction and product yields

This work describes studies of the photodegradation mechanism of 1-nitropyrene (1-NO(2)Py) in a chemical model system consisting of an organic solvent and known constituents of an aerosol particle. Photoproducts such as 1-hydroxypyrene (1-OHPy), 1-hydroxy-x-nitropyrenes (1-OH-x-NO(2)Py), 1-nitrosopyrene, and 1,6- and 1,8-pyrenediones were identified by high-performance liquid chromatography (HPLC) and HPLC/mass spectrometry (HPLC/MS) techniques, and their quantum yields show a significant dependence on the type of solvent. The photodegradation quantum yield of 1-NO(2)Py, φ((-1-NO2Py)), was larger in toluene, benzene, and polar protic solvents (10(-3)) in comparison with nonpolar and polar aprotic solvents, where the yield is on the order of 10(-4). In solvents with an abstractable hydrogen atom, the products formed in higher yields were 1-OHPy and 1-OH-x-NO(2)Py. These represent 60-80% of the photodestruction yield and result from abstraction and recombination reactions of the pyrenoxy radical, an intermediate postulated to be formed as a result of a nitro-nitrite rearrangement in nitroaromatics. The small O(2) effect in the photodegradation yield and the quenching experiments with azulene demonstrate the small contribution of the (3)(π,π*) state in the 1-NO(2)Py photoreaction. The nitrosopyrene product was not observed under these conditions, demonstrating the participation of the (3)(π,π*) state in its formation. In the presence various phenol aerosol constituents, the photodegradation yield increased by 10-fold in all solvents. This effect is partly ascribed to the reaction of the (3)(π,π*) state with the phenol. The effect of water resulted in the reduction of the 1-NO(2)Py photodegradation yield and of its photoproducts. The phototodegradation of 1-NO(2)Py was also studied in a viscous solvent, hexadecane, and it was determined that this medium does not inhibit its photodecay.

[How do transport and metabolism affect the biological effects of polycyclic aromatic hydrocarbons?]

Polycyclic aromatic hydrocarbons (PAHs), some of which are carcinogenic/mutagenic, are generated by combustion of fossil fuels and also released through tanker or oilfield accident to cause a large scale environmental pollution. PAHs concentration in China is especially high in East Asia because of many kinds of generation sources such as coal heating systems, vehicles and factories without exhaust gas/particulate treatment systems. So, the atmospheric pollution caused by PAHs in China has been seriously concerned from the view point of health effects. Like yellow sand and sulfur oxide, PAHs exhausted in China are also transported to Japan. Additionally, strongly mutagenic nitrated PAHs (NPAHs), estrogenic/antiestrogenic PAH hydroxides (PAHOHs) and reactive oxygen species-producing PAH quinones (PAHQs) are formed from PAHs by the chemical reaction during the transport. Furthermore these PAHOHs and PAHQs are produced by the metabolism in animal body. In the biological activities caused by the above PAH derivatives, the structure-activity relationship was observed. In this review, our recent results on the generation of PAH derivatives by atmospheric transport and metabolism are reported. Also, the existing condition of PAHs as atmospheric pollutants is considered.