Solid Selective Catalytic Reduction: A Promising Approach towards Reduction of NOx Emission from Exhaust of CI Engines

The rising rate of pollution in urban areas has become a worldwide concern in recent years. Diesel engines are considered one of the largest contributors to environmental pollution caused by exhaust emissions, and they are responsible for several health problems as well. Diesel engines contain carbon monoxide, carbon dioxide, unburned hydrocarbons, and oxides of nitrogen. The reduction of Nitric oxides (NOx) emission from diesel engine exhaust is currently being researched by automotive manufacturers. After much research, selective catalytic reduction (SCR) technology was discovered to be effective in reducing nitrogen oxide emission from diesel engine exhaust. This paper is an attempt to explore the problems associated with the use of selective catalytic reduction (SCR) and compares selective catalytic reduction (SCR) with the latest technology named solid selective catalytic reduction (SSCR) for efficient reduction of NOx emission from the exhaust of diesel engines. The issue of contamination, malfunctioning, and freezing of diesel exhaust fluid (DEF) at low temperatures are the major problems associated with the application of SCR. It is observed that by controlling the quantity of ammonia slip, SSCR can give better performance in the reduction of NOx emission from the exhaust of diesel engines.

Deferoxamine Treatment Improves Antioxidant Cosmeceutical Formulation Protection against Cutaneous Diesel Engine Exhaust Exposure

Skin is one of the main targets of the outdoor stressors. Considering that pollution levels are rising progressively, it is not surprising that several cutaneous conditions have been associated with its exposure. Among the pollutants, diesel engine exhaust (DEE) represents one of the most toxic, as it is composed of a mixture of many different noxious chemicals generated during the compression cycle, for ignition rather than an electrical spark as in gasoline engines. The toxic chemicals of most concern in DEE, besides the oxides of nitrogen, sulfur dioxide and various hydrocarbons, are metals that can induce oxidative stress and inflammation. The present study aimed to evaluate the effects of topical application, singularly or in combination, of the iron-chelator deferoxamine and a commercially available formulation, CE Ferulic, in up to 4-day DEE-exposed skin. DEE induced a significant increase in the oxidative marker 4-hydroxy-nonenal (4HNE) and matrix-metallopeptidase-9 (MMP-9), the loss of cutaneous-barrier-associated proteins (filaggrin and involucrin) and a decrease in collagen-1, while the formulations prevented the cutaneous damage in an additive manner. In conclusion, this study suggests that iron plays a key role in DEE-induced skin damage and its chelation could be an adjuvant strategy to reinforce antioxidant topical formulations.

Application of Single-Particle Mass Spectrometer to Obtain Chemical Signatures of Various Combustion Aerosols

A single-particle mass spectrometer (SPMS) with laser ionization was constructed to determine the chemical composition of single particles in real time. The technique was evaluated using various polystyrene latex particles with different sizes (125 nm, 300 nm, 700 nm, and 1000 nm); NaCl, KCl, MgCO3, CaCO3, and Al2O3 particles with different chemical compositions; an internal mixture of NaCl and KCl; and an internal mixture of NaCl, KCl, and MgCl2 with different mixing states. The results show that the SPMS can be useful for the determination of chemical characteristics and mixing states of single particles in real time. The SPMS was then applied to obtain the chemical signatures of various combustion aerosols (diesel engine exhaust, biomass burning (rice straw), coal burning, and cooking (pork)) based on their single-particle mass spectra. Elemental carbon (EC)-rich and EC-organic carbon (OC) particles were the predominant particle types identified in diesel engine exhaust, while K-rich and EC-OC-K particles were observed among rice straw burning emissions. Only one particle type (ash-rich particles) was detected among coal burning emissions. EC-rich and EC-OC particles were observed among pork burning particles. The single-particle mass spectra of the EC or OC types of particles differed among various combustion sources. The observed chemical signatures could be useful for rapidly identifying sources of atmospheric fine particles. In addition, the detected chemical signatures of the fine particles may be used to estimate their toxicity and to better understand their effects on human health.

OCCUPATIONAL CANCER BURDEN: THE CONTRIBUTION OF EXPOSURE TO PROCESS-GENERATED SUBSTANCES AT THE WORKPLACE

Occupational exposure to respirable crystalline silica, diesel engine exhaust emissions and welding fumes are widespread risk factors for lung cancer, and account for approximately half of the occupational lung cancer burden. If employers succeed in controlling workplace exposures to these process-generated substances, the fraction of lung cancers attributable to occupational exposures could be reduced dramatically.

Current diesel engine exhaust exposure in the Ontario construction industry

Introduction: Diesel engine exhaust (DEE) is a known carcinogen and a common occupational exposure in Canada, particularly within construction. The use of diesel-powered equipment in the construction industry is widespread, but little is known about DEE exposures and occupational disease in this work setting. The objective of this study was to characterize and identify key determinants of DEE exposure at construction sites in Ontario. Methods: Diesel particulate matter (DPM) measurements were taken from workers employed on seven infrastructure construction worksites in Ontario. Full-shift personal air samples were collected from workers using a constant-flow pump and SKC aluminum cyclone with 37-mm quartz fibre filters in an open-faced cassette. Samples were analyzed for elemental carbon (EC), a surrogate of DEE exposure, following NIOSH method 5040. Exposures were compared to recommended health-based limits, including the Dutch Expert Committee on Occupational Safety (DECOS) limit (1.03µg/m3 respirable EC) and the Finnish Institute of Occupational Health (FIOH) recommendation (5µg/m3 respirable EC). A determinants of exposure model was constructed. Results: In total, 126 DPM samples were collected, ranging from <0.47-52.58µg/m3 with a geometric mean (GM) of 4.23µg/m3 (geometric standard deviation (GSD)=3.05). Overall, 44.8% of samples exceeded the FIOH limit, mostly within underground worksites (93.5%), and 88.8% exceeded the DECOS limit. Underground workers (GM=13.20µg/m3, GSD=1.83) had exposures approximately 4-times higher than below grade workers (GM=3.56µg/m3, GSD=1.94) and 9-times higher than aboveground workers (GM=1.49µg/m3, GSD=1.75). Work grade, enclosed cabs, and seasonality were identified as the major determinants of exposure. Conclusions: This study provides a better understanding of current DPM exposure in Canadian construction. Most exposures were above recommended health-based limits, signifying a need to further reduce DPM levels in construction. These results can inform a hazard reduction strategy including a new occupational exposure limit and targeted intervention/control measures to reduce DPM exposure and the burden of occupational cancer.