Polycyclic aromatic hydrocarbons are a class of semi-volatile organic carbons that are emitted from both natural and anthropogenic sources therefore are ubiquitous in nature. Their main sources are both fossil and biomass fuels as well as other feedstocks used in chemical and combustion processes. Mostly the combustion processes are PAH depletion processes rather than PAH generating processes. PAHs are emitted from both stationary and mobile sources at varying levels depending on the operation conditions such as fuels, feedstock, and control devices in use as well as process parameters for example combustion temperatures.After emission from sources, the fates of PAHs in the atmosphere include partitioning between gas and particulate phases, particle size distribution, long range transport, dry and wet deposition on to water bodies, soil, vegetation and other receptor surfaces as well as resuspension from receptor surfaces back to the atmosphere. These processes are controlled by their physiochemical properties. Additionally, it is through these processes that human beings are exposed to PAHs via inhalation, ingestion and dermal contact.Dry deposition is the major process through which PAHs from the atmosphere are made available to receptor surfaces including the human respiratory system. From studies with cumulative fractions of dry deposition and size distribution for particulate PAHs, it is evident that the coarse particles are majorly responsible for the highest fraction of deposition fluxes. This is especially true for the high molecular weight PAHs, since the low molecular weight PAHs are majorly in the gas phase, which have lower dry deposition velocities. On the other hand, the highest risk for human being comes in the form of fine particles, whose mean aerodynamic diameter is below 2.5 µm. This is because the particle bound content results and particle size distributions of PAHs indicate that the fine particles have the most PAH content owing to their large surface areas and high organic carbon content. For the wet deposition of PAHs, more research is recommended for measurement of scavenging ratios of individual PAHs, since there is a scarcity of studies focusing on this issue.PAH mutagenic activity and exposure risk of humans can be estimated using the deposition rates, toxicity levels based on benzo(a)pyrene, or biomarkers such as urinary 1-hydroxypyrene. Other parameters that have been used to evaluate the risks of various exposure groups include inhalation exposure levels (IEL), incremental lifetime cancer risk (ILCR), and estimation of maximum consumption time (t max ). Highway toll workers, back carbon workers and food vendors in night markets are among susceptible groups identified using these biomarkers and exposure parameters.To reduce exposure to human beings, PAH emissions need to be controlled at the sources. Control and reduction of PAH emissions from various sources involves largely altering the fuel and feedstock characteristics, using air pollution control devices and/or adjustin...

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Kaohsiung County, in southern Taiwan, has both highly industrial and rural areas. In this study, the characteristics of PCDD/Fs in the ambient air of Kaohsiung (urban), Meinong (rural) and Xiaogang (heavy industrial zone) in 2014 and 2015 were modeled based on the prevailing meteorological conditions and the measured ambient air concentrations of PM 2.5 , PM 10 and TSP. The yearly average PM 2.5 concentrations in the ambient air of the three areas were in the range of 23 to 31 µg m -3 , all above the National Air Quality Standard of Taiwan (15 µg

This overview attempts to outline what we currently know about the PCDD/F emission inventories and the source categories therein. Besides the best available control techniques, suggestions are offered on how to reduce the PCDD/F emission factors and emission quantity of some important PCDD/F emission sources. The PCDD/F combustion sources can be classified as either stationary or mobile or minimally/uncontrolled combustion sources. The major stationary sources of PCDD/Fs are metal production processes, waste incineration, heat and power plants, and fly ash treatment plant. Crematories, vehicles, residential boilers and stoves are of key concern due to their proximity to residential areas and their relatively lower lying stacks and exhaust gases, which may result in great impact to their surrounding environment.Moreover, we offered our perspectives on how to improve the quality and representative of the PCDD/F emission factors to attain PCDD/F inventories which correspond more to reality. These points of view include: (1) PCDD/F contributions during start-up procedures of MSWIs should be considered, (2) the sampling times of stack flue gases for EAFs and secondary metal smelters should correspond to whole smelting process stages, (3) longer flue gas sampling time should be executed for power plants, (4) direct exhaust samplings from tailpipes for mobile sources, (5) development of an open burn testing facility that can reflect the real open burning conditions, and (6) long-term sampling techniques like AMESA are suggested to used exclusively for the most contributed PCDD/F stationary sources.

Fine particulate matters (PM 2.5 ) has been identified as one of the major air pollutants in urban areas, which are responsible for the adverse effects on public health and the deterioration of visibility. New PM 2.5 air quality standards were promulgated in Taiwan on 14 th May 2012, as well as the standard sampling and analytical method for atmospheric PM 2.5 (NIEA A205.11C) on 24 th April 2012. In this study, the atmospheric levels and characteristics of PM 2.5 in Tainan during 2013 were evaluated by measuring the mass concentration of PM 2.5 and analyzing the water-soluble ionic, carbon, and metal components. Additionally, a Chemical Mass Balance (CMB) receptor model was used to identify possible sources of PM 2.5 and their contributions. Based on results of this study, the current PM 2.5 levels in Tainan in spring and winter (41-49 µg m -3 ) were substantially higher than the yearly average PM 2.5 air quality standards (15 µg m -3 ). According to chemical composition analysis, secondary aerosols (NH 4 + , NO 3 -, and SO 4 2-) contributed approximately 50% and 60% of PM 2.5 mass in spring and winter respectively; but were responsible about 40% by mass in summer at both Tainan and Xinying stations. From the results of CMB model, the main contribution sources to the PM 2.5 in Tainan are traffic emissions (31.5%), ammonium sulfate (25.5%), ammonium nitrate (12.5%), and crustal elements (11%). Consequently, to improve PM 2.5 of Tainan City, the priority control pollutants (or sources) are primary PM 2.5 (open burning, construction sites and road dust by vehicles), NO x (diesel vehicle emissions), and SO x (fuels).