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Airborne particles, bacteria and fungi consist main determinants of indoor air quality. In this study, these characteristics were investigated in two exhibition halls of the Historical Museum of Crete, in comparison with the outdoor environment. In Zacharias Portalakis (ZP) hall, three air purifiers were operating during museum opening hours, as opposed to El Greco (EG) hall. A significant part of ultrafine (2.5–10 were associated with human occupancy in both halls, indicating transportation from visitors and resuspension as possible sources. Average airborne bacterial concentration was also lower in ZP than in EG hall, assessed by both molecular and culture-dependent methods. The bacterial and fungal communities of both indoor halls were distinct from the outdoor counterpart. Micrococcus and Staphylococcus, in terms of bacteria, and Alternaria and Malassezia, in terms of fungi, were the most abundant genera indoors, most of them being human-related. Hierarchical clustering of indoor samples indicated that EG hall bacteria were similar to ZP hall bacteria collected on the same day, but varied between different sampling dates. This observation, together with the bacterial beta-diversity analysis, implied that both indoor halls probably shared common bacterial source(s), while the respective fungal pattern of the two indoor halls was found significantly separated. The outdoor air contribution in EG and ZP hall bacterial profile presented a comparable fluctuation pattern; this was not observed for fungi, probably indicating the complexity of potential sources for different fungal taxa.

Homogeneous nucleation is an important source of new particles in the atmosphere worldwide. The resulting newly formed stable nuclei can grow to larger sizes and affect air quality and climate. Unexpected significant spatial variability of the nucleation frequency has been observed in Greece in the only previous relative study: very high frequency in Thessaloniki, intermediate in Eastern Crete and low in Patras (Patoulias et al., 2018). Our hypothesis is that Greece may be an excellent natural laboratory to investigate the factors affecting nucleation and to understand the reasons behind this surprising variability.Extensive continuous aerosol size distribution measurements took place during two summers (2020 and 2021) as part of the PANACEA project in 11 different locations: Patras, Xanthi, Ioannina, Finokalia, Athens, Thessaloniki, Sifnos, Chania, Costa Navarino (NEO), Lesvos and Mt. Helmos. The instrumentation used included a number of scanning mobility particle sizers (SMPS) for the measurement of the particles and a suite of gas monitors for measuring SO2, NOx, NH3 and CO in selected sites. A particle size magnifier (PSM) was deployed in the Patras site during the 2021 campaign, providing valuable information regarding nanoparticles with diameter down to 1 nm.The observations suggest that indeed the nucleation frequency during summer in Greece varies from close to zero in the southwestern parts of the country to more than 70% in the northern central and eastern regions. The analysis of the measurements in the various sites shows that the proximity to coal-fired power plants is a major factor affecting the nucleation frequency. North-eastern and northern airmasses passing over such locations in the Balkans and Western Turkey where strongly associated with nucleation. Also, the emissions of ammonia during summer, suggest that it exhibits similar spatial gradients with the observed nucleation frequency and may be controlling nucleation in Greece. The corresponding measurements in each site, were also used to estimate the corresponding particle growth and formation rates and the condensation and coagulation sinks.The detailed analysis of the measurements in Patras, Western Greece, suggests that nucleation was infrequent in this location (12%), but particles that were formed a few hours earlier over central Greece are often transported to this area after they have grown to sizes of 20-30 nm. The air mass history suggested that new particle formation often took place in the vicinity of an area 100-150 km northeast of Patras, with significant agricultural activity and therefore, high emissions of ammonia and amines. The relatively high emissions of biogenic volatile organic compounds in Western Greece where Patras is located, did not appear to assist in the local formation of new particles.

Summarization: This study presents for the first time comprehensive measurements of the particle number size distribution (10 nm to 10 μm) together with next-generation sequencing analysis of airborne bacteria inside a dental clinic. A substantial enrichment of the indoor environment with new particles in all size classes was identified by both activities to background and indoor/outdoor (I/O) ratios. Grinding and drilling were the principal dental activities to produce new particles in the air, closely followed by polishing. Illumina MiSeq sequencing of 16S rRNA of bioaerosol collected indoors revealed the presence of 86 bacterial genera, 26 of them previously characterized as potential human pathogens. Bacterial species richness and concentration determined both by qPCR, and culture-dependent analysis were significantly higher in the treatment room. Bacterial load of the treatment room impacted in the nearby waiting room where no dental procedures took place. I/O ratio of bacterial concentration in the treatment room followed the fluctuation of I/O ratio of airborne particles in the biology-relevant size classes of 1–2.5, 2.5–5, and 5–10 μm. Exposure analysis revealed increased inhaled number of particles and microorganisms during dental procedures. These findings provide a detailed insight on airborne particles of both biotic and abiotic origin in a dental clinic. Presented on: Indoor Air

Summarization: PM10 concentration and its elemental content were measured inside a university classroom where painting and sketching activities took place. The primary goal was to investigate the impact of these activities to (1) indoor PM10 concentrations, (2) identify PM10 levels in the presence/absence of the activities and (3) investigate the corresponding impact on its elemental content. As such, indoor online measurements and 24-h gravimetric measurements took place at short-term fixed periods. Outdoor PM10 concentrations were also available. It was found that PM10 levels were substantially increased during the occupied hours with average PM10 during activity ranged between 19 and 171 μg/m3, whereas during background periods it ranged between 12 and 66 μg/m3. Moreover, indoor concentrations during the activity were usually higher compared to outdoor levels, but the opposite behavior was found for background periods. Regarding the elemental content, positive correlations of heavy metals (Cu, Zn, Pb, Ba) found predominantly in the coarser fraction were associated with the use of painting powders. On the other hand, metals like Cr, Mn, Fe and Ni were primarily associated with anthropogenic sources, while the crustal origin of Ti, Mg and Al dominated indoors for particles > 1 μm. Other correlations between elements in the submicron fraction suggested origin from soil and anthropogenic sources as well as aged painting-originated particles. In summary, the present study demonstrated the significant impact of painting/sketching activities to indoor PM10 levels. Direct emissions from the use of powders as well as resuspension activities of the occupants were identified as the major indoor sources that provoked elevated concentrations. Παρουσιάστηκε στο: International Journal of Environmental Science and Technology

Wildfires are integral parts of ecosystems but at the same time they consist a threat for manmade and natural environments. Variability in the area burned by wildfires has been largely attributed to weather and climate drivers, hence fire danger indices such as the Canadian Fire Weather Index (FWI) uses solely climate variables. The FWI uses four climate variables (precipitation, temperature, wind and relative humidity), to estimate two sub-indices, one for the wildfire initial spread danger - the initial spread index, and one that accounts for the longer-term drought effects on the fire danger - the buildup index, from which the FWI is finally assessed. Here, we establish correlations between the individual climate variables, FWI and its subindices, with observed GFED monthly burned area, for each one of the 14 GFED pyrographic region, at a global scale. The correlations are established on aggregated by the size of burned area data, to reduce the effect of other smaller scale climate effects, as well as other socioeconomic factors such as fire suppression activities, etc. The established correlations are then used to estimate the relative sensitivity of the area burned, to each climate variable and FWI component. The analysis is repeated for different burned area land use types, i.e. forest areas, non-forest areas as well as their combination. Our results indicate the relative importance of the four climate variables, as well as the two sub-indices of FWI index, for each GFED region. The results highlight the significance of temperature and relative humidity to the variability of area burned, in many regions, globally. This work contributes to a better understanding of the climate drivers of global wildfire activity. This work is supported by CLIMPACT - National Research Network on Climate Change and its Impacts project, financed by the Public Investment Program of Greece and supervised by General Secretariat for Research and Technology (GSRT); and by the Leverhulme Centre for Wildfires, Environment, and Society through the Leverhulme Trust, grant number RC-2018-023.

This study investigated the suitability of outdoor particulate matter data obtained from a fixed monitoring station in estimating the personal deposited dose. Outdoor data were retrieved from a station located within the urban area of Lisbon and simulations were performed involving school children. Two scenarios were applied: one where only outdoor data were used assuming an outdoor exposure scenario, and a second one where an actual exposure scenario was adopted using the actual microenvironment during typical school days. Personal PM10 and PM2.5 dose (actual exposure scenario) was 23.4% and 20.2% higher than the ambient (outdoor exposure scenario) PM10 and PM2.5 doses, respectively. The incorporation of the hygroscopic growth in the calculations increased the ambient dose of PM10 and PM2.5 by 8.8% and 21.7%, respectively. Regression analysis between the ambient and personal dose showed no linearity with R2 at 0.07 for PM10 and 0.22 for PM2.5. On the other hand, linear regression between the ambient and school indoor dose showed no linearity (R2 = 0.01) for PM10 but moderate (R2 = 0.48) for PM2.5. These results demonstrate that ambient data must be used with caution for the representativeness of a realistic personal dose of PM2.5 while for PM10 the ambient data cannot be used as a surrogate of a realistic personal dose of school children.

PM

Summarization: Investigation of the personal dose caused by air pollution in children is important due to their vulnerability. Exposure to PM10 and its components, particularly certain metals, may pose significant health risks therefore many studies have focused on measuring the ambient indoor/outdoor PM10 concentrations in school environments. However, little research has aimed at assessing the resultant personal dose. Hence, this study applied a dosimetry model (ExDoM2) to predict the personal dose received by students in five primary schools in Lisbon, Portugal. The calculations were performed for PM10 and PM10-bound metals, and the exposed subjects were assumed to be 10-year-old nose breathers. A realistic exposure scenario involving three different settings (the indoor home, indoor school and outdoor school microenvironments) was implemented for an exposure period of one week (Monday–Sunday). Although the students spent only 24% of their total time inside a school (vs. 73% at home), this environment contributed 44% on average to the weekly deposited dose of PM10, providing further evidence that indoor exposure at schools is a major contributor to the total dose. The modeling results showed that the cumulative deposited doses in the respiratory tract (RT) reached as high as 2,004 μg, 0.16 μg, 0.65 μg, 0.58 μg and 0.06 μg for PM10, Cr, Mn, Pb and Ni, respectively, after one week. Presented on: Aerosol and Air Quality Research

Summarization: PM10 levels were determined at different locations in a coastal site in the eastern Mediterranean to assess the relative contribution of local versus regional sources. Two campaigns were conducted: during the first, PM10 was monitored at three urban locations (kerbside/traffic/background) at different sampling periods, whereas during the second one, PM10 was simultaneously measured at two locations (urban/suburban). Both campaigns have shown that African dust transport was a major carrier of coarse particles. Daily PM10 concentrations of 547 μg m−3 and 234 μg m−3 were measured during the first and the second campaigns, respectively, both of them associated with severe dust storms. However, some dust episodes influenced lesser PM10 levels. The contribution from dust episodes to the measured concentration was estimated at 2–527 μg m−3 during the first campaign and 4–218 μg m−3 during the second campaign. Classification into dusty and non-dusty days has shown that local anthropogenic sources also influence ambient PM10 concentrations; however, few exceedances of the daily limit of 50 μg m−3 occurred during both campaigns. Particularly, it was found that domestic heating during cold months was a major contributor to PM10 levels followed by emissions from traffic with higher contribution of the latter during summer months (high touristic season) as well as non-traffic emissions (road dust resuspension). Hourly average PM10 concentration during the second campaign has shown that traffic-related emissions and/or road dust resuspension were associated with up to 40 μg m−3 whereas during wintertime late evening hours, PM10 concentration from heating reached up to 60 μg m−3 at the central urban location. Παρουσιάστηκε στο: Air Quality, Atmosphere and Health

Summarization: Residential settings are of utmost importance for human exposure, as it is where people spend most of their time. Residential wood combustion is a widespread practice known as a source of indoor particulate matter (PM). Nevertheless, research on the risks of exposure associated with this source is scarce, and a better understanding of respiratory deposition of smoke particles is needed. The dosimetry model ExDoM2 was applied to determine the deposited dose of inhalable particulate matter (PM10) from residential biomass combustion in the human respiratory tract (HRT) of adults and children. The dose was estimated using PM10 exposure concentrations obtained from a field campaign carried out in two households during the operation of an open fireplace and a woodstove. Simultaneously, PM10 levels were monitored outside to investigate the outdoor dose in a rural area strongly impacted by biomass burning emissions. Indoors, the 8-h average PM10 concentrations ranged from 88.3 to 489 μg m−3 and from 69.4 to 122 μg m−3 for the operation of the fireplace and the woodstove, respectively, while outdoor average PM10 concentrations ranged from 17.3 to 94.2 μg m−3. The highest amount of the deposited particles was recorded in the extrathoracic region (68–79%), whereas the deposition was much lower in the tracheobronchial tree (5–6%) and alveolar–interstitial region (16–21%). The total dose received while using the fireplace was more than twofold the one received in the room with a woodstove and more than 10 times higher than in the absence of the source. Overall, indoor doses were higher than the ones received by a subject exposed outdoors, especially at the alveolar–interstitial region. After 24 h of exposure, it was estimated that approximately 35 to 37% of the particles deposited in the HRT were transferred to the gastrointestinal tract, while approximately 2.0–2.5% were absorbed into the blood. The results from exposure and dose of indoor particles gathered in this work suggest that homeowners should be encouraged to upgrade the wood burning technology to reduce the PM levels inside their residences. This study also provides biologically relevant results on the lung deposition of particles from residential biomass burning that can be used as a reference for future research. Presented on: Environmental Science and Pollution Research

Atmospheric particles are a major environmental health risk. Assessments of air pollution related health burden are often based on outdoor concentrations estimated at residential locations, ignoring spatial mobility, time-activity patterns, and indoor exposures. The aim of this work is to quantify impacts of these factors on outdoor-originated fine particle exposures of school children. We apply nested WRF-CAMx modelling of PM

Emission inventories for particulate matter (PM2.5 and PM2.5-10) from natural sources were created for the Athens and Thessaloniki metropolitan areas and the greater area of Volos for the period 2010–2013. The inventories include primary windblown dust emissions from agricultural and vacant lands, primary sea salt particles emissions from the breaking of waves at the Sea Shore-surf zone and the bursting of bubbles from oceanic whitecaps - Open Ocean, and emissions of BVOCs (Biogenic Volatile Organic Compounds), precursor to PM. The objective of this work was to study the seasonal variation of natural PM emissions in the areas of interest and their spatial allocation. Weighting factors, specific to each pollutant, source and area, were calculated for the disaggregation of annual emissions to monthly and daily values and their allocation on high resolution grids. There was no significant seasonal variation observed in the natural PM emissions while BVOCs emissions were increased during the warm period due to the enhanced solar radiation and temperature. The results of the calculations were compared to values of the period 2000–2010 and it was found that natural BVOCs emissions during the period 2010–2013 were enhanced compared to 2000–2010 whereas natural PM emissions have lowered. Moreover, the analysis focused on the effects from possible future changes in land cover and environmental conditions to the temporal and spatial variation of natural emissions over the areas using specific scenarios.

The aim of this study is to examine the ability of two modelling systems, a global and a regional, to reproduce the influence of Etesian winds on the ozone zonal distribution over Eastern Mediterranean. Specifically, the results of the global MACC (Monitoring Atmospheric Composition and Climate) reanalysis model (Integrated Forecast System - MOZART (IFS-MOZART)) and an ensemble of MACC regional air quality models (ENS) are compared versus observed data from three background monitoring stations in Central and Eastern Mediterranean (i.e. Gharb (ARB) - Malta, Finokalia (FIN) (Crete) - Greece and Agia Marina (CAO) - Cyprus). Two distinct group of days characterized by different wind flows are used for the evaluation assessment for a 5-month period (May to September) for two years (2011 − 2012). During the selected period, the Etesians are the predominant winds that blow from northern directions over the Aegean Sea, affecting ozone levels. The observed mean ozone concentrations at Eastern Mediterranean stations are about 5 ppbv higher during Etesian days than during non-selected days whereas at the Central Mediterranean station (ARB), the difference between the two groups of days is small. Furthermore, the Eastern Mediterranean stations present generally higher observed ozone levels than the Central Mediterranean station with these differences intensifying during Etesian days. The evaluation results suggest that although the two modelling systems underestimate surface ozone concentrations systematically, they can capture to a certain extend the effect of the Etesian winds on the ozone zonal distribution. Specifically, FIN station which is directly under the influence of the Etesian winds presents higher simulated ozone values compared to the other two stations in agreement with the observations. For both modelling systems, the statistical evaluation metrics are better for the Central Mediterranean station, but there is a considerable improvement for the regional modelling system indicating that the ENS reproduces better the observed ozone values and zonal distribution in comparison to the IFS-MOZART.

Measurements of airborne particulate matter mass concentration, mass size distribution, chemical speciation and microbial levels were performed in two museums and a library in Greece over a two-year period. The three cultural heritage sites were located in different environments [coastal (Heraklion), urban (Athens) and mountainous (Zagori)], and their collections consist mainly of organic materials. Particulate mass size distribution measurements (PM10) (cut-off diameters at 10, 9, 5.8, 4.7, 3.3, 2.1, 1.1, 0.7 and 0.4 μm) were performed inside the museums in conjunction with measurements of viable, cultivable microorganisms in air (heterotrophic bacteria, autotrophic chemolithotrophic bacteria, bacteria with metabolizing capabilities for exhibited organic materials, gelatin hydrolyzing bacteria, acid producing bacteria and fast growing fungi). The particulate matter measurements showed a variability, which was related to outdoor particle concentrations, indoor environmental conditions, infiltration rates and to indoor activities. The PM2.1 fraction of the PM10 mass had a value close to 0.6 indicating a significant outdoor origin. Chemical analysis (ions, carbonaceous material and metals) of particulate matter revealed that ions and organic carbon comprised the major part of the particle mass. Elevated concentrations of Fe, Al-rich and soluble particles were measured indoors in the three sites. An enrichment of bacteria with metabolizing capabilities for bone, parchment, woolen fabric, gelatin, and cellulose was encountered indoors in the cultural heritage sites studied as well as inside closed showcases. An indication of seasonal variations of the airborne microbial load was observed in the three cultural heritage collections. In addition, there were differences in the measured microbial load, indoors, inside the showcases and outdoors.

The objective of the current study was to calculate the deposited dose rate in the human respiratory tract arising from particle number (PN) and particle mass (PM) measurements. A main objective was the investigation of deposition pattern and characteristics of the two metrics in the human respiratory tract. The dose rate was estimated for residents at a suburban background location (Chania, Greece). The total dose rate showed two peaks, one in the morning (1.6 × 109 particles/h at 7:00-8:00) and the other one at night (2.1 × 109 particles/h at 21:00-22:00), during the warm period, while the cold period showed two peaks, morning (2.0 × 109 particles/h at 9:00-10:00) and afternoon (3.6 × 109 particles/h at 18:00-19:00). The peaks during the warm period were associated with traffic emissions, whereas the peaks during the cold period were associated with both heating and traffic emissions. A higher dose rate of PN10 was found in the alveolar region while for PM10 it was found in the extrathoracic region. These findings are linked with increased contribution of ultrafine and coarse particles to PN10 (65%-78% and 54%-62% for cold and warm periods, respectively) and PM10 (63% and 55% for cold and warm periods, respectively) concentrations, respectively. The current study showed the importance to use both number and mass aerosol metrics for determining the human exposure and regional dose and their related health effects. The novelty of the current study is the simultaneous measurements of the two particles metrics and the full particle size distributions to make accurate estimates of regional deposited dose.

Summarization: The aim of this study was to evaluate the nanoparticle emissions from a laser printer in a chamber in conjunction with emissions from printers in a print room (PR) and to characterize the processes that lead to increased nanoparticle concentrations, as well as to estimate the human particle dose of the printers’ users. Measurements were conducted in a small stainless steel environmental chamber under controlled conditions, where the evolution of particle size distributions (PSDs) with time and printed pages was studied in detail. Printer was generating nanoparticles (vast majority ˂ 50 nm with mode on ~ 15 nm) primarily during cold startup. Previously, 1-week sampling was also done in a PR at the Technical University of Crete, where the tested laser printer is installed along with three other printers. Similarly, as it was observed in the chamber study, printers’ startup on any given day was characterized by a sharp increase in particle number (PN) concentrations. Average measured PN concentrations during printing hours in PR (5.4 × 103 #/cm3) is similar to the one observed in chamber measurements (6.7 × 103 #/cm3). The ExDoM2 dosimetry model was further applied to calculate the deposition of particles in the human respiratory tract. More precisely, the increase in particle dose for an adult Caucasian male was 14.6- and 24.1-fold at printers’ startup, and 1.2- and 5.2-fold during printing in the PR and experimental chamber, respectively, compared to the exposure dose at background concentrations (BCs). Presented on: Environmental Science and Pollution Research

The eastern Mediterranean region is strongly influenced by long-range transported particulate matter such as desert dust from northern Africa. To investigate the dynamics of Saharan dust events and their origin, satellite images from the MODIS spectroradiometer of NASA’s satellites Terra and Aqua, and back trajectories analysis of the HYSPLIT model were combined together with continuous ground-based field data. Field PM10 and PM2.5 measurements were performed in the period 2003–2013 at the Akrotiri monitoring station on the island of Crete (Greece). Furthermore, the mineralogical composition of a small number of samples was determined by X-ray powder diffraction, whereas elemental particle composition analysis was performed on the dust samples collected using the ICP-MS technique for a series of elements. The annual average percentage of days with Sahara dust outbreaks in the region of western Crete (Akrotiri station) was 9.3% for the period 2003–2013. Excluding the PM10 exceedances caused by Sahara dust events, the average PM10 monthly concentrations are decreased by 20.5% during the 8-month period November–June, with higher PM10 concentration reduction (29.9%) in the period February–April. Mineralogical analysis showed that illite was the most abundant mineral identified in all samples, followed by quartz and calcite. Gypsum was detected only in the dry sample. Moreover, the elemental particle composition analysis showed that collected dust originated from Africa deserts.

Summarization: The present work deals with the resuspension of small nondeformable particles from multilayer deposits in a turbulent boundary layer. A kinetic force-balance approach was adopted to model particle motion at the point of detachment, whereby intermolecular interactions were modeled by the Lennard-Jones potential. The rate of change of the number of particles was estimated for each discrete layer based on existing kinetic models. In particular, the kinetic equations of Lazaridis and Drossinos (1998), LD, and Friess and Yadigaroglu (2001), FY, were implemented and compared using lattice arranged deposits. The influence of exposure time and friction velocity was investigated through the obtained resuspension rates. It was found that the single-layer resuspension rates were substantially affected by the layer position within the deposit as well as considerably influenced by both the exposure time and the friction velocity. Moreover, the numerical results demonstrate that the LD kinetic estimates higher resuspension rates compared to the FY kinetic only for short exposures to the flow, predominantly due to a different expression for the fraction of exposed particles. In addition, the present study recognized the time dependence (i.e., a short-term vs. long-term regime) of the resuspension rate observed both experimentally (Wu et al., 1992; Wang et al., 2012) and by model predictions (Lazaridis and Drossinos, 1998; Friess and Yadigaroglu, 2001; Reeks and Hall, 2001) and confirmed the inverse dependence of the resuspension rate with time in long-term regime. Two regimes were also identified while evaluating the resuspension rate for a range of friction velocities, viz., a low-friction regime in which the resuspension rate increases with friction and a high-friction regime in which the opposite behaviour was observed. Presented on: Aerosol and air quality research

Summarization: Atmospheric particles are a major environmental health risk. Assessments of air pollution related health burden are often based on outdoor concentrations estimated at residential locations, ignoring spatial mobility, time-activity patterns, and indoor exposures. The aim of this work is to quantify impacts of these factors on outdoor-originated fine particle exposures of school children. We apply nested WRF-CAMx modelling of PM2.5 concentrations, gridded population, and school location data. Infiltration and enrichment factors were collected and applied to Athens, Kuopio, Lisbon, Porto, and Treviso. Exposures of school children were calculated for residential and school outdoor and indoor, other indoor, and traffic microenvironments. Combined with time-activity patterns six exposure models were created. Model complexity was increased incrementally starting from residential and school outdoor exposures. Even though levels in traffic and outdoors were considerably higher, 80–84% of the exposure to outdoor particles occurred in indoor environments. The simplest and also commonly used approach of using residential outdoor concentrations as population exposure descriptor (model 1), led on average to 26% higher estimates (15.7 μg/m3) compared with the most complex model (# 6) including home and school outdoor and indoor, other indoor and traffic microenvironments (12.5 μg/m3). These results emphasize the importance of including spatial mobility, time-activity and infiltration to reduce bias in exposure estimates. Presented on: Science of the Total Environment

Real-time PM10 mass concentrations were monitored inside the trains and in several platforms of red and blue lines in Athens metro system during two measurement campaigns. Furthermore, measurements of PM1, PM2.5, and PM10 concentrations were conducted on a fixed site on a subway platform of blue line (Nomismatokopio) and the majority of particles were in the fine mode. PM10 concentrations were measured inside the metro trains along the entire route of the two metro lines during commuting hours, and the average PM10 concentration was 132.2 ± 34.0 μg/m3 in the red line and 138.0 ± 35.6 μg/m3 in the blue line. Measurements were also conducted in eight platforms and higher concentrations were observed in stations located in the center of Athens, under heavily trafficked streets. An exposure and dose assessment model, ExDoM2, was implemented in order to calculate the deposition, dose, and retention of aerosol particles in the respiratory tract (RT), the gastrointestinal (GI) tract, and their absorption to blood. The model was applied to study the human dose of three different subjects, a person with sedentary employment commuting by metro 1 h per day, a metro worker with sedentary activity, and a metro worker with light exercise activity. The dose varies in the different regions of the RT with the highest dose in the extrathoracic region. The dose in the RT after commuting by metro for 1 h was 125.4 μg that corresponds to 36.3% of the total personal daily dose (worst-case scenario, no indoor sources).

Summarization: The objective of the current study was to measure the particle mass concentration, mass size distribution, and metal composition of airborne particles in a waste management facility located at Chania (Crete, Greece). Measurements were performed at two locations of the waste management facility. High particulate matter (PM10) concentrations were observed at the indoor site of manual waste sorting. In particular, the average concentration of PM10 was equal to 217 μg/m3 during working hours, while during non-working hours was equal to 60 μg/ m3. The particle mass size distributions were unimodal reflecting the resuspension of coarse particles. Furthermore, the deposited dose of particles and particle-bound metals and their retention in the human respiratory tract was determined using a dosimetry model (ExDoM2). The ExDoM2 model was applied for an adult male worker (06:30–14:30) at the indoor site of a manual waste sorting. The daily working deposited dose of PM10 ranged from 1677 to 3028 μg, while the daily working deposited dose of particle-bound metals ranged from 22 to 39 μg. The highest daily working deposited dose in the respiratory tract is calculated for iron mass (PΜFe) and the daily working deposited dose for PΜFe ranged from 18 to 33 μg. Παρουσιάστηκε στο: Journal of Material Cycles and Waste Management

A field study was performed to identify the size distribution characteristics of viable, cultivable airborne microorganisms (heterotrophic bacteria, fungi, and total coliforms) at a municipal wastewater treatment facility, and their association with inhalable particulate matter (PM1, PM2.5, and PM10), as well as hydrogen sulfide concentrations and ambient meteorological parameters. The highest concentrations of cultivable, airborne heterotrophic bacteria, total coliforms, mass and number concentration of particulate matter, as well as hydrogen sulfide were observed at the aerated grit removal chambers at the pretreatment stage (3 to 2030 times higher than the values of the background ambient air). In contrast, the mean concentrations of cultivable, airborne mesophilic fungi at the aerated grit chambers were 0.6 time lower than the background site, where fungi presented the most abundant taxonomic group in the ambient air. Although the highest concentrations of the airborne fungi were determined at aerodynamic diameters between 2.1 and 3.3 μm, a nearly equal distribution of the mean concentrations of the cultivable, airborne heterotrophic bacteria were observed in the six different size fractions at the primary settling tanks and in the ambient air. Interestingly, their size distribution profiles at the aerated grit chambers were different and showed a maximum aerodynamic diameter at the size range from 3.3 to 4.7 μm, similar to that of the cultivable, airborne total coliforms. In general, low positive or no significant linear relationships could be found between the cultivable airborne heterotrophic bacteria, total coliforms, or fungi at the two wastewater treatment stages and the ambient background microbial community.

Throughout the years, the performance of the FFRs has been the topic of extensive studies, resulting mainly in the characterization of aerosol penetration through filters using aerosols that are thought to be similar to those encountered in workplaces. There are limited number of studies in the literature reporting CE-marked respirator performance, and there is a need to perform a penetration evaluation of CE-marked respirators through all 3 filtering classes: FFP1 (80%), FFP2 (94%), and FFP3 (99%). In this study, the percentage penetrations and the most penetrating particle size (MPPS) of 47 mm filters cut out from 13 different CE-marked respirator half masks (2 samples of each FFR) were evaluated size-selectively using nine sizes of charge-neutralized monodisperse aerosol, which ranged from 20 to 400 nm (CMD). Comparison of the penetrations at MPPS from all the examined filters showed that the percentage penetration ranged 3.2–16.3% (FFP1), 2.4–34.3% (FFP2), and 0.02–3.3% (FFP3). Experimental data also revealed that the penetration difference between 2 samples from the same respirator was in most cases up to 6.8%, and between 2 identical respirators up to 2.5%. The MPPS was found to be between 30 and 60 nm (CMD) in all measurements. By comparing the obtained results to the European Standard we conclude that the standard method underestimates particle penetration (especially for particles < 100 nm) due to the usage of non neutralized, polydisperse test aerosol, detection methods burdened with measurement artifacts, and the assumption that the MPPS is at ≈ 600 nm (MMD) as the criterion for filtering facepieces to pass the penetration test.

A resuspension model based on the Lennard–Jones intermolecular potential is applied to a monolayer deposit of spherical particles. The model considers the interactions between a particle and a surface under the influence of an external turbulent airflow. The particle–surface interaction was modelled with and without particle deformation due to elastic flattening. The resuspension rate was calculated by a kinetic force-balance approach whereby particle detachment occurs when the instantaneous joint contribution of the lift and drag forces exceeds the total adhesive force of the particle–surface system. Enhanced aerodynamic particle removal driven by the moment of the lift and drag forces was determined. Model predictions suggest that inclusion of the moment of the aerodynamic forces provides a suitable model for particle detachment (initiated by rolling). The importance of elastic deformation was found to depend on adhesive forces, characteristics of the substrate surface (surface roughness) and pa...

Summarization: Measurements of the ambient viable microbe concentrations and of the microbial deposits on surfaces were performed in the Historical Museum of Crete over a period of two years. The levels of the airborne microbes in the museum rooms showed considerable variability, which was mainly related to the indoor activity (such as the number of visitors); indoor environmental conditions, including the air exchange rate; and exhibits’ chemical compositions and storage conditions as well as the conservation treatments and cleaning techniques to which they had been subjected. An enrichment of acid-producing bacteria, heterotrophic bacteria, and autotrophic chemolithotrophic bacteria was encountered indoors, but a considerable decrease in the viable microbes, ranging from 5.5% to 76%, was detected after the deployment of photocatalytic ionizers at the different measurement sites inside the museum. These ionizers mainly improved the air quality by reducing acid-producing bacteria, which potentially contribute to deterioration in cultural heritage objects. The microbial colonization on 24 different painting materials and surfaces collected into model artwork essays, which had not received any preservation treatment, was examined for an exposure period of 18 months. The bacterial depositions on the paintings gradually colonized, depending on the material and the surface, resulting in concentrations of 10–300,000 CFU cm–2. Although airborne fungi were observed in the exhibition rooms (at an average yearly concentration of 143 ± 115 CFU m–3), no fungal growth was detected on the majority of the painting materials in the model essays. Only the tempera, charcoal, wax pastel, and carton board displayed fungal colonization, which occurred very slowly and produced low concentrations of 70–200 CFU cm–2. Presented on: Aerosol and Air Quality Research

The objective of the current study is the determination of the personal exposure and dose of ambient particulate matter-bound metals in human tissues at five European cities. The accumulation in human body of lead (Pb), arsenic (As) and cadmium (Cd), in five European cities (Athens, Seville, Rome, Frankfurt and Zabrze) was calculated using an exposure and dose assessment model, ExDoM, and a pharmacokinetic model, PBPK. The study subjects are adult Caucasian nonsmoker males. It was calculated that the highest dose of particulate matter is received from a resident of Seville, due to the higher ambient PM10 levels in the city compared to the other sites. First, the current study showed that the European Union thresholds of particle-bound Pb, Cd and As concentrations were not exceeded in the cities under study. As regard the dose of Pb and As the higher dose is calculated for Athens and Seville, respectively. The highest dose of Cd is found at Zabrze, due to the high industrial activity in the city. It was calculated that after one day of exposure, the highest accumulation of Pb occurred in blood, muscles and bones. Furthermore, the highest deposition of Cd occurred in the lungs and intestines and for As in the lung and muscles. The heavy metals intake, calculated in this study, was very low in comparison with the recommended WHO levels for heavy metals intake from all types of exposure (inhalation, ingestion).

© 2015 The Authors. Conventional subway systems are characterized by high particulate matter (PM) concentrations. To relate PM exposure to adverse health effects it is important to determine the dose of the inhaled particles in the human respiratory tract (HRT). Therefore, the total and regional doses of particles for a healthy adult male using the dosimetry model ExDoM in the subway system were estimated. The overall dose was determined using the average exposure PM2.5 concentrations obtained from an extensive campaign in the Barcelona subway system, including measurements on the platforms and inside the trains. Despite the lower PM2.5 concentrations inside the trains with respect to those on station platforms, the highest dose was observed inside the trains due to longer exposure time, evidencing the importance of the exposure period in the estimation of the particle dose. Overall, during a subway commuting travel, roughly 80% of the inhaled mass of subway PM2.5 was deposited in the HRT. The highest amount of the inhaled particles was deposited in the extrathoracic region (68%), whereas the deposition was much smaller in the tracheobronchial tree (4%) and alveolar-interstitial region (10%). Individual's daily exposure to PM2.5 and dose were estimated, considering a typical time-activity pattern of an adult male who lives in Barcelona and commutes by subway. While a subject typically spends approx. 3% of the day in the subway system, this microenvironment may account for up to 47% of the total PM2.5 daily dose. These results might be similarly high for other commuting modes due to the reported high PM exposure levels. The dose is mainly dependent on the particle size and exposure concentrations.

Summarization: Ozone measurements have been performed in the period 2003–2009 at Akrotiri (suburban) and Finokalia (coastal) monitoring stations on the island of Crete, Greece. The main objectives were to investigate the concentration levels of ozone in the region of Crete, its spatial and temporal variability, the effect of air mass origin and local sources on ozone levels, and the frequency of exceedances of the EU limits for ozone concentrations in the area. The observed mean values for Akrotiri and Finokalia stations were 44.5 ± 8.5 and 49.1 ± 10.6 ppbv, respectively. Ozone concentrations were higher during the 8-month period between March and October (52.3 ± 6.8 and 53.0 ± 7.4 ppbv for Akrotiri and Finokalia station, respectively) whereas, in the period November–February, the concentrations were lower (37.7 ± 4.7 and 39.1 ± 6.9 ppbv, respectively). The above values indicate that there is not a west-east gradient of ozone concentration in the studied area. At both stations, AOT40 limit values were higher than the limit set by the European Union (Directive 2008/50/EC). Exceedances of the EU target value were encountered during 88 and 67 % of the time in Akrotiri and Finokalia stations, respectively. Differences on the diurnal patterns and daily ozone maxima between the two stations were attributed to the different characteristics of the two stations and to the effect of local pollution sources to Akrotiri station. The average value of the amplitude of the daily cycle (calculated as the difference between maximum and minimum values) in the case of Akrotiri was 8.3 ppbv, and it was about two times the corresponding value in Finokalia (4.7 ppbv), which is an indication of the effect of the anthropogenic emission produced in the city of Chania to the Aktotiri station environment. At Finokalia, the maximum values were observed 2–4 h later than those at Akrotiri. During springtime, the difference in the maximum values appearance was close to 4 h, with the maximum at Akrotiri at 16:00 (LT) and at Finokalia at about 20:00 (LT). This time difference supports the transfer of gaseous precursors and already formed ozone molecules toward Finokalia. Presented on

Proper Hospital healthcare Waste Management (HCWM) is imperative for ensuring public health and environmental protection. In this context, three Prefectural hospitals of Mytilene, Agrinio, and Messolonghi, were studied with respect to planning and management of infectious wastes, cost, training of the white Staff involved, security measures to be taken, and also knowledge related to the implementation of the existing National and European Community, legislation. It was found that the existing legislative procedures were broadly applied. However deviations were reported and it was recognized that serious difficulties in the implementation of the legislation throughout the process i.e. from the phase of separation throughout the processing phase did exist. These deviations frequently originated from conflicts in the directions given by the legislation Joint [Governmental Gazette B1537/8-5-2012]. In order to achieve better implementation of HCWM, recommendations are proposed here. &nbsp

Air pollution is one of the major environmental problems that influence people's health. Exposure to harmful particulate matter (PM) occurs both outdoors and indoors, but while people spend most of their time indoors, the indoor exposures tend to dominate. Moreover, higher PM concentrations due to indoor sources and tightness of indoor environments may substantially add to the outdoor originating exposures. Empirical and real-time assessment of human exposure is often impossible; therefore, indoor aerosol modeling (IAM) can be used as a superior method in exposure and health effects studies. This paper presents a simple approach in combining available aerosol-based modeling techniques to evaluate the real-time exposure and respiratory tract deposited dose based on particle size. Our simple approach consists of outdoor aerosol data base, IAM simulations, time-activity pattern data-base, physical–chemical properties of inhaled aerosols, and semi-empirical deposition fraction of aerosols in the respiratory tract. These modeling techniques allow the characterization of regional deposited dose in any metric: particle mass, particle number, and surface area. The first part of this presentation reviews recent advances in simple mass-balance based modeling methods that are needed in analyzing the health relevance of indoor exposures. The second part illustrates the use of IAM in the calculations of exposure and deposited dose. Contrary to previous methods, the approach presented is a real-time approach and it goes beyond the exposure assessment to provide the required information for the health risk assessment, which is the respiratory tract deposited dose. This simplified approach is foreseen to support epidemiological studies focusing on exposures originating from both indoor and outdoor sources.

Particulate matter (PM) number size distribution and mass concentration along with total volatile organic compounds (TVOC) were measured during emissions from painting materials inside an indoor microenvironment. The emission sources were derived from oil painting medium and turpentine used for painting. Two sets of measurements (10 experiments) were conducted in a laboratory room of 54 m3. New particle formation events were observed in all 10 experiments. The nucleation events lasted on average less than one hour with an average growth rate 33.9 ± 9.1 nm/h and average formation rate 21.1 ± 8.7 cm−3s−1. After the end of the nucleation event, a condensational growth of indoor particles followed with average growth rate 11.6 ± 2.8 nm/h and duration between 1.4 and 4.1 h. High concentrations up to 3.24 ppm were measured for the indoor TVOC concentrations during the experiments. Simultaneous mass and number size concentration measurements were performed outdoors where no new particle formation event was observed. It is the first time that high nucleation rates indoors were observed in conjunction with high TVOC concentrations originating from painting materials which resulted to high exposure concentration levels of particle number concentration.

This study focuses on the development of a methodology for the determination of the contribution of fugitive dust emissions from landfill sites to ambient PM10 concentrations and the subsequent exposure to working personnel. Fugitive dust emissions in landfills mainly originate from resuspension due to truck traffic on paved and unpaved roads and from wind-blown dust from landfill cover soil. The results revealed that exposure to PM10, originating from fugitive dust emissions in the landfill site, was exceeding the health protection standards (50 μg m(-3)). The higher average daily PM10 concentration (average value) for weekdays was equal to 275 μg m(-3) and was computed for the areas nearby the unpaved road located inside the landfill facilities that lead to the landfill cell. The percentage contributions of road and wind-blown dust to the PM10 concentrations on weekdays were equal to 76 and 1%, respectively. The influence of the background concentration is estimated close to 23%.

Mass and number concentration of particulate matter (PM10) was measured during walking experiments inside a laboratory. In total 20 walking experiments were conducted in a period of 3 months. Particle number concentration was measured in the size range of 0.02–1 μm, while, mass concentration was measured in the range 0.1–10 μm. The PM10 mass increased during the activity, by average 84%, whereas, the walking activity had no impact on particle number concentration. Human induced resuspension rates were examined under different dust loadings. The different dust loadings used (25, 15, 5, 1 g/m2) in order to evaluate the impact of surface loading on the indoor PM10 mass concentration and on the resuspension rate. Walking style was the same in all experiments. Moreover, the experiments involved two different walking patterns inside the laboratory (rectangular and line). The impact of different speed was also examined. The average resuspension rate was calculated to be equal to 10−2–10−3 hr−1. No impact on resuspension rate was observed for different walking patterns or walking speed. On the other hand, the measured mass concentration inside the room was increased when using higher dust loading on the floor, although the estimated resuspension rate found independent on the initially deposited surface dust loading.

Bacteria activation and cloud condensation nuclei (CCN) formation have been studied in the atmosphere using the classical theory of heterogeneous nucleation. Simulations were performed for the binary system of sulfuric acid/water using laboratory-determined contact angles. Realistic model simulations were performed at different atmospheric heights for a set of 140 different bacteria. Model simulations showed that bacteria activation is a potentially favorable process in the atmosphere which may be enhanced at lower temperatures. CCN formation from bacteria nuclei is dependent on ambient atmospheric conditions (temperature, relative humidity), bacteria size, and sulfuric acid concentration. Furthermore, a critical parameter for the determination of bacteria activation is the value of the intermolecular potential between the bacteria&rsquo, s surface and the critical cluster formed at their surface. In the classical nucleation theory, this is parameterized with the contact angle between substrate and critical cluster. Therefore, the dataset of laboratory values for the contact angle of water on different bacteria substrates needs to be enriched for realistic simulations of bacteria activation in the atmosphere.

A two-week campaign was performed in a naturally ventilated apartment to quantify indoor sources and to estimate the total inhaled mass of particulate matter (PM). DustTrak photometers were used to record PM2.5 concentrations continuously. Indoor activities were recorded in a detailed time–activity diary. The results showed that short episodic indoor sources influenced the indoor PM concentration for several hours and significantly affected daily average PM2.5 concentrations, indoor/outdoor ratios and indoor/outdoor correlation coefficients. Activities leading to increased PM concentrations occurred in 9% of the total time monitored, and accounted for 68% of the total PM concentration. Among the many indoor activities recorded, smoking and hair spraying were the strongest sources of fine aerosol. The outcomes of cooking episodes were the most variable in terms of duration and aerosol levels. The calculated inhaled mass corresponded to the source strength but not to the duration of the source activity. The total mass of aerosol potentially inhaled by an adult individual during the time outside the episodes was 1367 µg and during the episodes 2895 µg. During one hour, one person potentially inhaled approximately 36 µg and 294 µg of aerosol for the non-episode and the episode periods, respectively.

Summarization: Indoor/outdoor aerosol size distribution was measured in four European cities (Oslo–Norway, Prague–Czech Republic, Milan–Italy and Athens–Greece) during 2002 in order to examine the differences in the characteristics of the indoor/outdoor modal structure and to evaluate the effect of indoor sources to the aerosol size distributions. All the measurement sites were naturally ventilated and were occupied during the campaigns by permanent residents or for certain time periods by the technical staff responsible for the instrumentation. Outdoor particle number (PN) concentrations presented the higher values in Milan and Athens (median values 1.4 × 104 # cm–3 and 2.9 × 104 # cm–3 respectively) as a result of elevated outdoor emissions and led to correspondingly higher indoor values compared to Oslo and Prague. In absence of indoor activities, the indoor concentrations followed the fluctuations of the outdoor concentrations in all the measurement sites. Indoor activities (cooking, smoking, etc.) resulted in elevated indoor PN concentrations (maximum values ranging between 1.7 × 105 # cm–3 and 3.2 × 105 # cm–3) and to I/O ratios higher than one. The I/O ratios were size dependant and for periods without indoor activities, they presented the lowest values for particles < 50 nm (0.51 ± 0.15) and the ratios increased with fine particle size (0.79 ± 0.12 for particles between 100–200 nm). The analysis of the modal structure showed that the indoor aerosol size distribution characteristics differ from the outdoors under the effect of indoor sources. The percentage of unimodal size distributions increased during indoor emissions, compared to periods without indoor sources, along with the number concentration of Aitken mode particles, indicating emissions in specific size ranges according to the type of the indoor source. Presented on: Aerosol and air quality research

The objective of this work was to identify Sahara dust intrusions and quantify their contribution to annual and daily PM10 concentrations over the Athens Metropolitan Area (AMA) during the period 2001–2010. Additionally, extreme PM10 values attributed to large forest fires and volcanic emissions or the synergy of the above with African dust intrusions have been identified. It was found that the concentrations of PM10 during the period studied exceeded the European Union’s Air Quality Standard (EU AQS) value at most of the traffic urban (TU) stations. Most of the extreme values were attributed to dust events or large forest fires. The contribution from African dust to PM10 concentrations on days with events and exceedances of the EU AQS was approximately 50% at TU stations and 72% at the background suburban stations (BS). Most of the African dust events contributed about 5 μg/m 3 to 34 μg/m 3 to the daily PM10 concentrations, whereas the average contribution to annual PM10 concentrations was approximately 8.6 ± 1.8 μg/m 3 i.e., 22.2 ± 7.5%. During the decade, no clear interannual relationship was observed between the African dust contribution and the frequency and intensity of events. The more frequent and severe episodes occurred during spring, while less frequent and less severe episodes occurred during summer. After the extraction of the African dust load the annual and daily AQS was exceeded in 2010 at only one TU station. The average annual contribution of African dust to the exceedances was approximately 36% at TU stations and 58% at BS stations.

Summarization: Assessment of population exposure is very important for the evaluation of the adverse health effects of particulate matter (PM) ambient levels. In this work population exposure to PM10 and PM2.5 has been evaluated in outdoor environments in the Athens (AMA) and Thessaloniki (TMA) metropolitan areas during the period 2001–2010. The methodology used is based on combining spatiotemporally allocated PM10 and PM2.5 concentration fields with the geographical distribution of population. The results showed that the number of people living in the AMA exposed to PM10 and PM2.5 concentrations above the annual air quality standards (AQS), has dropped 18% since 2001 and 98% since 2008, respectively. Likewise, in 2010 8% less, compared to 2001, of the AMA population lived in areas where the daily AQS for PM10 was exceeded > 35 times a year. The results as regards TMA indicated a decrease in the number of people exposed to PM10 concentrations over the annual AQS value (78% decrease). However, the number of people living in areas with PM10 concentrations over the daily AQS for > 35 times in a year doubled since 2001. Finally, the spatial distribution of the normalised population load which reflects populated areas with concentrations above the daily AQS was evaluated. The hot spots for both AMA and TMA areas correspond to urban areas and areas with significant primary PM10 emissions. Presented on: Science of the Total Environment

This work focuses on the evaluation of the simulated ozone levels from the global MACC (Monitoring Atmospheric Composition and Climate) reanalysis and an ensemble of MACC regional air quality models with ozone measurements from three baseline stations in Central and Eastern Mediterranean Sea, located in Malta, Greece (island of Crete) and Cyprus. Τhis region and especially the Aegean Sea are under the influence of the Etesian winds that start blowing in late spring and stop in early autumn. The evaluation is performed by calculating statistical metrics for a period of two years (2011–2012) for both models separately for the selected Etesian days and the non-selected days. Moreover, in order to examine whether the stratosphere-troposphere ozone transport contributes to ozone concentrations, four different pressure levels (1013, 850, 700 and 500 hPa) from the global model are also assessed. The analysis reveals that both global reanalysis and the ensemble of regional models underestimate the near surface ozone levels. In general, the underestimation is lower at Malta and Cyprus stations during non-selected days. The ensemble of the regional models presents a better performance compared to the global reanalysis approach.

The biological loading of viable, cultivable airborne microbes (heterotrophic bacteria, actinobacteria and fungi) in 6 size fractions as well as the three different fractions of respirable particulate matter (PM1, PM2.5 and PM10) and their relationship to meteorological conditions were studied in the ambient air due to health-related interests. An Andersen six stage viable particle impactor and a MAS 100 sampler were used for microbial measurements. 82 measurements were performed at three different periods (41 days) at a suburban, residential site in the city of Chania (Crete, Greece) during the period from April 2008 to June 2009. The concentrations of the viable, cultivable airborne microbes (bioaerosols) as well as of the PM1, PM2.5 and PM10 were highly variable during the whole measurement period. Among the airborne microbes, fungi presented the most abundant taxonomic group in the ambient air. A characteristic profile of the mean size distribution of biological loading in different PM fractions was obtained for every measured microbial taxonomic group. Although, the highest concentrations of the airborne fungi and actinobacteria were determined at aerodynamic diameters between 2.1 and 3.3 μm, a nearly equal distribution of the mean concentrations of the airborne heterotrophic bacteria was observed in the six different size fractions. However, two small maxima were observed at the airborne heterotrophic bacteria distribution, one at the fraction with aerodynamic diameters between 1.1 and 2.1 μm, and at other at the coarse fraction with aerodynamic diameter larger than 7 μm. A considerable part of the airborne microbes Cycloheximide per mL of growth medium of bacteriwere resistant to drugs. Between 10 and 40 % of the viable, cultivable airborne microbes were resistant to low concentrations of drugs (5–10 μg of Streptomycin or a or fungi, respectively). Furthermore, multiple linear regression of the data showed that the variation in fungi concentrations depends on the variation in PM10 mass concentration, PM1 number concentration, relative humidity and solar radiation. Likewise, the concentration of heterotrophic bacteria was found proportional to the values of relative humidity and fungal concentration, whereas was negatively correlated to the solar radiation.

This study examines the impact of forest fires on natural biogenic volatile organic compounds (BVOCs) and windblown dust emissions over urban areas; specifically over the Athens larger urban zone for the reference year 2008. The area spans a continuum of urban–suburban–wild lands and suffers air quality problems with respect to particulate matter (PM) which are frequently exacerbated during the summer due also to forest fire events. Although the anthropogenic, natural and forest fire emissions in the area have been well documented in the past, the indirect effect of forest fires on natural emissions has not been estimated. A brief description of the area and the history of forest fires events during the period 2000–2008 are presented together with an emission inventory for particulate matter (PM2.5 and PM2.5–10) and non-methane VOC (NMVOC), precursor to PM, from anthropogenic and natural sources for the reference year 2008. The effect of large forest fires (over 40 ha) during the period 2000–2008 on natural emissions is examined with respect also to the spatial and temporal distribution and their relative contribution to total emissions over the area. Moreover, the effect of several parameters and assumptions used in natural emissions calculations pre and post-fire events is discussed. The results indicate that there is a trade-off between fire effects that can result in an increase in PM10 windblown dust emissions but decrease of BVOCs emissions due to vegetation reduction. The changes in natural BVOCs and PM10 emissions over the selected area are rather small, specifically 3.5% and 1.7%, respectively. Changes in the relative contribution of natural to total PM10 and NMVOC emissions in the area due to forest fires was also found small, approximately 0.5% and 0.7%, respectively. The contribution of anthropogenic emissions appears to dramatically outweigh the potential effects on air quality from natural emissions and their changes due to large forest fires. Therefore, more attention should be given to mitigating the anthropogenic emissions in the area for the purposes of promoting air quality.