The history, genotoxicity, and carcinogenicity of carbon-based fuels and their emissions. Part 3: Diesel and gasoline

Unveiling the Surface Chemical Reactions during Multi-Phase Catalytic Oxidation of Soot on Nanoengineering/Interfacing/Doping-Prepared Mn-CeO2 Catalysts Using TG-MS and Operando DRIFTS-MS

The aerosol pyrolysis method from nitrate precursors was used to prepare the Mn-CeO2 catalyst containing Mn2O3, CeO2, and Mn-doped CeO2 nanoparticles for catalyzing carbonous soot oxidation. The prepared Mn-CeO2 catalysts have high specific surface areas, Ce3+ ratio, and oxygen vacancy defects; these are a benefit for soot oxidation. The T50 for soot oxidation on the 0.57Mn-CeO2 catalyst is as low as 355 °C, which is 329 °C lower than that for soot oxidation without a catalyst. The catalysts were characterized using XRD, SEM-EDS, HRTEM, XPS, Raman spectroscopy, H2-TPR-MS, O2-TPD-MS, soot-TPR-MS, and operando DRIFTS-MS. The functions of Mn2O3, CeO2, and Mn-doped CeO2 in the 0.57Mn-CeO2 catalyst are unveiled. Mn-doped CeO2 plays a key role and CeO2 participates in soot oxidation, while Mn2O3 is used to enhance higher ratios of Ce3+, via the reaction of Mn3+ + Ce4+ = Mn4+ + Ce3+. The mechanism of soot oxidation on Mn-CeO2 was proposed.

Biodiesel exhaust particle airway toxicity and the role of polycyclic aromatic hydrocarbons

Renewable alternatives to fossil diesel (FD) including fatty acid methyl ester (FAME) biodiesel have become more prevalent. However, toxicity of exhaust material from their combustion, relative to the fuels they are displacing has not been fully characterised. This study was carried out to examine particle toxicity within the lung epithelium and the role for polycyclic aromatic hydrocarbons (PAHs). Exhaust particles from a 20% (v/v) blend of FAME biodiesel had little impact on primary airway epithelial toxicity compared to FD derived particles but did result in an altered profile of PAHs, including an increase in particle bound carcinogenic B[a]P. Higher blends of biodiesel had significantly increased levels of more carcinogenic PAHs, which was associated with a higher level of stress response gene expression including CYP1A1, NQO1 and IL1B. Removal of semi-volatile material from particulates abolished effects on airway cells. Particle size difference and toxic metals were discounted as causative for biological effects. Finally, combustion of a single component fuel (Methyl decanoate) containing the methyl ester molecular structure found in FAME mixtures, also produced more carcinogenic PAHs at the higher fuel blend levels. These results indicate the use of FAME biodiesel at higher blends may be associated with an increased particle associated carcinogenic and toxicity risk.

Level of oxidative stress for the land snail Cepaea nemoralis from aged and bioremediated soil contaminated with petroleum products

Here, we investigated whether the widely distributed snail Cepaea nemoralis could be used as a suitable sentinel animal for assessing the effects of soil contaminants-petroleum oil derivatives-after years of soil ageing and treatment with a bacterial formulation. Oxidative stress was assessed in the foot and hepatopancreas of C. nemoralis L. exposed to soil contaminated with unleaded petrol, spent engine oil or diesel oil and bioremediated with a bacterial formulation (soil was used 2 years after contamination and bioremediation process). We measured total antioxidant capacity, catalase and glutathione transferase activity and concentrations of superoxide anions, hydrogen peroxide and protein carbonyls in the foot and hepatopancreas of snails after 2 and 4 weeks of treatment. The studied antioxidant responses appeared largely to be tissue and remediation process specific, while the concentrations of superoxide anions, hydrogen peroxide and protein carbonyls depended on time of exposure, tissue type and the type of contaminants, but mostly not on the remediation process. Generally, changes in the concentrations of superoxide anions, hydrogen peroxide and protein carbonyls in the hepatopancreas of snails seemed to be a suitable measure to assess the risk of animals exposed to soil contaminated with petroleum substances and used after many years of ageing and treatment with a microbial formulation.

Mutagenicity and carcinogenicity of combustion emissions are impacted more by combustor technology than by fuel composition: A brief review

Studies during the past 50 years have characterized the carcinogenicity and mutagenicity of extractable organic material (EOM) of particulate matter (PM) in ambient air and from combustion emissions. We have summarized conclusions from these studies and present data supporting those conclusions for 50 combustion emissions, including carcinogenic potencies on mouse skin (papillomas/mouse/mg EOM), mutagenic potencies (revertants/μg EOM) in the Salmonella (Ames) mutagenicity assay, and mutagenicity emission factors (revertants/kg fuel or revertants/MJ_thermal ) in Salmonella. Mutagenic potencies of EOM from PM in ambient air and combustion emissions span 1-2 orders of magnitude, respectively. In contrast, the revertants/m³ span >5 orders of magnitude due to variable PM concentrations in ambient air. Carcinogenic potencies of EOM from combustion emissions on mouse skin and EOM-associated human lung cancer risk from those emissions both span ~3 orders of magnitude and are highly associated. The ubiquitous presence of polycyclic aromatic hydrocarbons (PAHs), nitroarenes, and aromatic amines results in mutagenic and carcinogenic potencies of PM that span only 1-3 orders of magnitude; most PM induces primarily G to T mutations. Mutagenicity emission factors of combustion emissions span 3-5 orders of magnitude and correlate with PAH emission factors (r > 0.9). Mutagenicity emission factors were largely a function of how material was burned (highly efficient modern combustors versus open burning) rather than what materials were burned. Combustion systems that minimize kinetic and mass-transfer limitations and promote complete oxidation also minimize the mutagenicity of their emissions. This fundamental engineering principle can inform environmental and public health assessments of combustion emissions.

Chemical and toxicological characterization of particulate emissions from diesel vehicles

This paper presents a detailed chemical and toxicological characterization of the diesel particulate matter (PM) emitted from diesel vehicles running on a chassis dynamometer under different driving conditions. Chemical analyses were performed to characterize the contents of organic carbon (OC), elemental carbon (EC), and 31 polycyclic aromatic hydrocarbons (PAHs) in the collected PM samples. The OC-EC analysis results revealed that PM emissions from diesel vehicles in this study were dominated by OC and that the emission of vehicles equipped with diesel particulate filters had high OC/EC ratios. The PAH analysis results revealed that 4- and 5-ring PAHs were the dominant PAHs in the OC fraction of the PM samples. Particle toxicity was evaluated through three toxicological markers in human A549 cells, namely (1) acellular 2,7-dichlorofluorescein (DCFH) for oxidative potential, (2) interleukin-6 (IL-6) for inflammation, and (3) glutathione (GSH) for antioxidation after exposure. Statistical analyses revealed that vehicle sizes have statistically significant effects on the concentrations of the markers. Correlation analysis between PAHs and toxicological markers revealed that significant correlations existed between specific compounds and markers. Our results can be used as a reference by policy makers to formulate emission control strategies and as a dataset for other modeling studies.

Quantitative Evaluation of the Emissions of a Transport Engine Operating with Diesel-Biodiesel

The present work is about evaluating the emission characteristics of biodiesel-diesel blends in a reciprocating engine. The biodiesel was produced and characterized before the test. A virtual instrument was developed to evaluate the velocity, fuel consumption, temperature, and emissions of O2, CO, SO2, and NO from an ignition-compression engine of four cylinders with a constant rate of 850 rpm. The percentages of soybean-biodiesel (B) blended with Mexican-diesel (D) analyzed were 2% B-98% D (B2), 5% B-95% B (B5), and 20% B-80% D (B20). The biodiesel was obtained through a transesterification process and was characterized using Fourier-Transform Infrared spectroscopy and Raman spectroscopy. Our results indicate that CO emission is 6%, 10%, and 18% lower for B2, B5, and B20, respectively, in comparison with 100% (D100). The O2 emission is 12% greater in B20 than D100. A reduction of 3% NO and 2.6% SO2 was found in comparison to D100. The obtained results show 44.9 kJ/g of diesel’s lower heating value, this result which is 13% less than the biodiesel value, 2.8% less than B20, 1.3% than B5, and practically the same as B2. The specific viscosity stands out with 0.024 Poise for the B100 at 73 °C, which is 63% greater than D100. The infrared spectra show characteristics signals of esters groups (C-O) and the pronounced peak from the carbonyl group (C=O). It is observed that the increase in absorbance of the carbonyl group corresponds to an increase in biodiesel concentration.

Fifteen Years of Airborne Particulates in Vitro Toxicology in Milano: Lessons and Perspectives Learned

Air pollution is one of the world’s leading environmental causes of death. The epidemiological relationship between outdoor air pollution and the onset of health diseases associated with death is now well established. Relevant toxicological proofs are now dissecting the molecular processes that cause inflammation, reactive species generation, and DNA damage. In addition, new data are pointing out the role of airborne particulates in the modulation of genes and microRNAs potentially involved in the onset of human diseases. In the present review we collect the relevant findings on airborne particulates of one of the biggest hot spots of air pollution in Europe (i.e., the Po Valley), in the largest urban area of this region, Milan. The different aerodynamic fractions are discussed separately with a specific focus on fine and ultrafine particles that are now the main focus of several studies. Results are compared with more recent international findings. Possible future perspectives of research are proposed to create a new discussion among scientists working on the toxicological effects of airborne particles.

Prenatal exposure to diesel exhaust particles causes anxiety, spatial memory disorders with alters expression of hippocampal pro-inflammatory cytokines and NMDA receptor subunits in adult male mice offspring

Air pollution by Diesel exhaust (DE) consists of gaseous compounds and diesel exhaust particles (DEPs). Previous studies show associations between prenatal exposure to diesel exhaust affects the central nervous system (CNS). However, there was not reported that these effects were caused by gaseous compounds, diesel exhaust particles, or both. A limited number of studies in rodent models have shown that exposure to DEPs can result in CNS. Here, we explored the effects of prenatal exposure to DEPs on anxiety and learning and memory in NMRI mice male offspring. Three groups of pregnant mice were exposed to 350-400 μg DEPs/m³ for 2, 4 and 6 h daily in a closed system room. We examined anxiety and learning and memory in 8-to-9-week-old male offspring using the Elevated plus maze and Morris water maze (MWM) test. Hippocampi were isolated after the behavioral tests and measured pro-inflammatory cytokines and N-methyl-D-aspartate (NMDA) receptor expression by quantitative RT-PCR analysis. Mice exposed to DEPs in utero showed deficits in the Elevated plus maze and Morris water maze test. In addition, DEPs exposed mice exhibited decreased hippocampal NR2A and NR3B expression. Taken together, our data suggest that maternal DEP exposure is associated with anxiety, disrupts learning and memory and reduction hippocampal NR2A and NR3B expression in male offspring.

Exposure to nanoscale diesel exhaust particles: Oxidative stress, neuroinflammation, anxiety and depression on adult male mice

Exposure to nanoscale diesel engines exhausted particles (DEPs) is a well-recognized risk factor for respiratory and cardiovascular diseases. Rodents as commonly used models for urban air pollution in health effect studies demonstrate constant stimulation of inflammatory responses in the main areas of the brain. Nevertheless, the primary effect of diesel exhaust particulate matter on some of the brain regions and relation by behavioral alterations still remains untouched. We evaluated the brain regional inflammatory responses to a nanosized subfraction of diesel engines exhaust particulate matter (DEPs < 200 nm) in an adult male mice brain. Adult male mice were exposed to DEPs for 3, 6, and 8 h per day, 12 weeks and five days per week. Degree of anxiety and the depression by elevated plus maze and Forced Swimming Test respectively (FST) did measurement. After behavior tests, the plasma and some of the brain regions such as olfactory bulb (OB) and hippocampus (HI) were analyzed for oxidative stress and inflammatory responses. The inflammation and oxidative stress changes in OB and HI, markedly coincides with the results of behavioral alterations. These responses corresponded with rapid induction of MDA and nitrite oxide (NO) in brain regions and neuronal nitric oxide synthase (nNOS) mRNA followed by IL6, IL1α, and TNFα in OB and HI. The different times of DEPs exposure, leads to oxidative stress and inflammatory in plasma and brain regions. That this cumulative transport of inhaled nanoscale DEPs into the brain and creating to inflammation responses of brain regions may cause problems of brain function and anxiety and depression.

Biological effects of airborne fine particulate matter (PM2.5) exposure on pulmonary immune system

Airborne fine particulate matter (PM_2.5) attracts more and more attention due to its environmental effects. The immune system appears to be a most sensitive target organ for the environmental pollutants. Inhaled PM_2.5 can deposit in different compartments in the respiratory tract and interact with epithelial cells and resident immune cells. Exposed to PM_2.5 can induce local or systematic inflammatory responses. This review focus on the effects of respiratory tract exposed to PM_2.5. Firstly, we introduced the major emission sources, basic characteristics of PM_2.5 and discussed its immunoadjuvant potential. Secondly, we elaborated the immune cells in the respiratory tract and the deposition of PM_2.5 regarding the structural characteristics of the respiratory tract. Furthermore, we summarized the in vivo/vitro studies that revealed the immunotoxic effects of PM_2.5 exposure to pulmonary cellular effectors and explored the contribution of PM_2.5 exposure to the Th1/Th2 balance.

Advanced Collaborative Emissions Study Auxiliary Findings on 2007-Compliant Diesel Engines: A Comparison With Diesel Exhaust Genotoxicity Effects Prior to 2007

Since its beginning, more than 117 years ago, the compression-ignition engine, or diesel engine, has grown to become a critically important part of industry and transportation. Public concerns over the health effects from diesel emissions have driven the growth of regulatory development, implementation, and technological advances in emission controls. In 2001, the United States Environmental Protection Agency and California Air Resources Board issued new diesel fuel and emission standards for heavy-duty engines. To meet these stringent standards, manufacturers used new emission after-treatment technology, and modified fuel formulations, to bring about reductions in particulate matter and nitrogen oxides within the exhaust. To illustrate the impact of that technological transition, a brief overview of pre-2007 diesel engine exhaust biomarkers of genotoxicity and health-related concerns is provided, to set the context for the results of our research findings, as part of the Advanced Collaborative Emissions Study (ACES), in which the effects of a 2007-compliant diesel engine were examined. In agreement with ACES findings reported in other tissues, we observed a lack of measurable 2007-compliant diesel treatment-associated DNA damage, in lung tissue (comet assay), blood serum (8-hydroxy-2'-deoxyguanosine [8-OHdG] assay), and hippocampus (lipid peroxidation assay), across diesel exhaust exposure levels. A time-dependent assessment of 8-OHdG and lipid peroxidation also suggested no differences in responses across diesel exhaust exposure levels more than 24 months of exposure. These results indicated that the 2007-compliant diesel engine reduced measurable reactive oxygen species-associated tissue derangements and suggested that the 2007 standards-based mitigation approaches were effective.

Assessment of urothelial cells atypical changes among petroleum station workers in Saudi Arabia

The aim of the present study was to assess atypical changes in urothelial cells among petroleum station workers. This is a case control study, investigating 300 participants by cytological methods. Of the 300 participants, 150 were cases (exposed to petroleum products) and 150 were controls (non-exposed). Full voided urine was obtained and was cytologically assessed. Cytological atypia was identified in nine (6%) out of the 150 cases and could not be identified in 141/150 (94%) of the cases, whereas, in the control group, cytological atypia was recognized in four (2.7%) of the 150 controls and could not be identified in 146/150 (97.3%). The risk associated with petroleum product exposure, the odds ratio (OR), and 95% confidence interval (CI) was 2.33 (0.7015–7.7378), P = 0.1673. Exposure of petroleum station workers to petroleum products increases the risk of urothelial atypical changes, which may progress to precancerous and cancerous changes.

Application of Biologically Based Lumping To Investigate the Toxicokinetic Interactions of a Complex Gasoline Mixture

People are often exposed to complex mixtures of environmental chemicals such as gasoline, tobacco smoke, water contaminants, or food additives. We developed an approach that applies chemical lumping methods to complex mixtures, in this case gasoline, based on biologically relevant parameters used in physiologically based pharmacokinetic (PBPK) modeling. Inhalation exposures were performed with rats to evaluate the performance of our PBPK model and chemical lumping method. There were 109 chemicals identified and quantified in the vapor in the chamber. The time-course toxicokinetic profiles of 10 target chemicals were also determined from blood samples collected during and following the in vivo experiments. A general PBPK model was used to compare the experimental data to the simulated values of blood concentration for 10 target chemicals with various numbers of lumps, iteratively increasing from 0 to 99. Large reductions in simulation error were gained by incorporating enzymatic chemical interactions, in comparison to simulating the individual chemicals separately. The error was further reduced by lumping the 99 nontarget chemicals. The same biologically based lumping approach can be used to simplify any complex mixture with tens, hundreds, or thousands of constituents.

Social Isolation-Induced Territorial Aggression in Male Offspring Is Enhanced by Exposure to Diesel Exhaust during Pregnancy

Diesel exhaust particles are a major component of ambient particulate matter, and concern about the health effects of exposure to ambient particulate matter is growing. Previously, we found that in utero exposure to diesel exhaust affected locomotor activity and motor coordination, but there are also indications that such exposure may contribute to increased aggression in offspring. Therefore, the aim of the present study was to test the effects of prenatal diesel exhaust exposure on social isolation-induced territorial aggression. Pregnant mice were exposed to low concentrations of diesel exhaust (DE; mass concentration of 90 μg/m3: DE group: n = 15) or clean air (control group: n = 15) for 8 h/day during gestation. Basal locomotion of male offspring was measured at 10 weeks of age. Thereafter, male offspring were individually housed for 2 weeks and subsequently assessed for aggression using the resident-intruder test at 12 weeks of age, and blood and brain tissue were collected from the male offspring on the following day for measuring serum testosterone levels and neurochemical analysis. There were no significant differences in locomotion between control and DE-exposed mice. However, DE-exposed mice showed significantly greater social isolation-induced territorial aggressive behavior than control mice. Additionally, socially-isolated DE-exposed mice expressed significantly higher concentrations of serum testosterone levels than control mice. Neurochemical analysis revealed that dopamine levels in the prefrontal cortex and nucleus accumbens were higher in socially isolated DE-exposed mice. Serotonin levels in the nucleus accumbens, amygdala, and hypothalamus were also lower in the socially isolated DE-exposed mice than in control mice. Thus, even at low doses, prenatal exposure to DE increased aggression and serum testosterone levels, and caused neurochemical changes in male socially isolated mice. These results may have serious implications for pregnant women living in regions with high levels of traffic-related air pollution.

PAH dynamics in roadside environments: Influence on the consistency of diagnostic ratio values and ecosystem contamination assessments

Roadside contamination (of air, soils and organisms) by polycyclic aromatic hydrocarbons (PAHs) was examined in an arable field and a mature forest (central France). Measured contents accounted for minute fractions of the cumulative vehicular exhaust emissions. The fate of vehicular PAHs was affected by many factors, including: atmospheric load dispersal, deposition on soils and vegetation, incorporation into water and organic matter cycles, and accumulation in species. Given these empirical results, we evaluated the consistency of a set of well-known diagnostic ratios. This effort has revealed that: i) most diagnostic ratio values vary considerably across roadside samples, including exhaust emissions; and ii) the first few meters from the carriageway or the road verge/forest interface or remote areas where surface water accumulates actually define turning or inflection points in the ratio profiles. These variations constitute a major obstacle to delimitating the extent of roadside contamination due to PAHs, in addition to raising questions over the applicability of ratios routinely used to designate sources. New ratios, namely (Flt+BkF)/(Pyr+BbF) and (Flt+BkF+BghiP)/Σ10PAH, have been specifically developed to address this challenge. The higher consistencies exhibited among environmental compartments as well as between surface soil and exhaust emissions still yield differentiated values relative to several industrial sources.

In utero exposure of mice to diesel exhaust particles affects spatial learning and memory with reduced N-methyl-D-aspartate receptor expression in the hippocampus of male offspring

Diesel exhaust consists of diesel exhaust particles (DEPs) and gaseous compounds. Previous studies reported that in utero exposure to diesel exhaust affects the central nervous system. However, there was no clear evidence that these effects were caused by diesel exhaust particles themselves, gaseous compounds, or both. Here, we explored the effects of in utero exposure to DEPs on learning and memory in male ICR mice. DEP solutions were administered subcutaneously to pregnant ICR mice at a dose of 0 or 200 μg/kg body weight on gestation days 6, 9, 12, 15, and 18. We examined learning and memory in 9-to-10-week-old male offspring using the Morris water maze test and passive avoidance test. Immediately after the behavioral tests, hippocampi were isolated. Hippocampal N-methyl-D-aspartate receptor (NR) expression was also measured by quantitative RT-PCR analysis. Mice exposed to DEPs in utero showed deficits in the Morris water maze test, but their performance was not significantly different from that of control mice in the passive avoidance test. In addition, DEP-exposed mice exhibited decreased hippocampal NR2A expression. The present results indicate that maternal DEP exposure disrupts learning and memory in male offspring, which is associated with reduced hippocampal NR2A expression.

Combusting vegetable oils in diesel engines: the impact of unsaturated fatty acids on particle emissions and mutagenic effects of the exhaust

High particle emissions and strong mutagenic effects were observed after combustion of vegetable oil in diesel engines. This study tested the hypothesis that these results are affected by the amount of unsaturated or polyunsaturated fatty acids of vegetable oils. Four different vegetable oils (coconut oil, CO; linseed oil, LO; palm tree oil, PO; and rapeseed oil, RO) and common diesel fuel (DF) were combusted in a heavy-duty diesel engine. The exhausts were investigated for particle emissions and mutagenic effects in direct comparison with emissions of DF. The engine was operated using the European Stationary Cycle. Particle masses were measured gravimetrically while mutagenicity was determined using the bacterial reverse mutation assay with tester strains TA98 and TA100. Combustion of LO caused the largest amount of total particulate matter (TPM). In comparison with DF, it particularly raised the soluble organic fraction (SOF). RO presented second highest TPM and SOF, followed by CO and PO, which were scarcely above DF. RO revealed the highest number of mutations of the vegetable oils closely followed by LO. PO was less mutagenic, but still induced stronger effects than DF. While TPM and SOF were strongly correlated with the content of polyunsaturated fatty acids in the vegetable oils, mutagenicity had a significant correlation with the amount of total unsaturated fatty acids. This study supports the hypothesis that numbers of double bounds in unsaturated fatty acids of vegetable oils combusted in diesel engines influence the amount of emitted particles and the mutagenicity of the exhaust. Further investigations have to elucidate the causal relationship.