Emissions of four pollutants (NOx, CO, particle mass (PM), and ultrafine particles (UFPs)) were estimated during aircraft activity at Copenhagen airport. The emissions were estimated for 5 discrete aircraft phases (taxi out, taxi in, take off, climb out, approach/landing) as well as Auxiliary Power Units (APUs) and handling which remain insufficiently characterized in the scientific literature. A Gaussian dispersion model (ISC3-ST) was applied to obtain pollutant dispersion in the vicinity of the airport. Dispersion models are widely used to simulate pollutant concentrations at various airports with most studies dealing with criteria pollutants (NOx, CO, PM). This study evaluated the impact from aviation activities including an emerging pollutant like UFPs. Besides criteria pollutants, assessing the UFPs concentrations at ground level and in the vicinity of airports is critical for evaluating human exposure. Numerical simulations showed that elevated NOx concentrations exceeded the regulated hourly values in the vicinity of the airport facilities. High UFPs concentrations were also modelled close to the airport with daily average values at 100,000 particles/cm3 at the airfield area and values close to 10,000 particles/cm3 at distances close to one kilometer downwind from the airport. Contrary, reduced contribution from aircraft LTO cycles to the ground-level CO and PM was found, with concentrations being lower than the air quality threshold values. These results underline that NOx and UFPs are significant contributors to exposure for both airport workers and residents living close to the airport while CO and PM are more relevant only for the former.

Cardiovascular exercise is a popular activity that aims to improve physical fitness and overall health, however practicing outdoors enhances pollutant inhalation. The main objective was to estimate the dose received by inhalation of airborne particles during cardiovascular exercise in urban environments. Dosimetry simulations used particle mass concentrations (PM2.5, PM2.5-10) to estimate the deposited dose in the human respiratory tract that assumed a young and healthy adult male and female train at variable activity intensities. Hourly dose rates were substantially increased with activity intensity due to increased inhaled volumes, with a 9.5-fold increase from rest (60 bpm) to high-intensity exercise (170 bpm). PM levels played also a crucial role as increased concentrations were linked with increased deposition rates. Heating, and Sahara events comprised the most burdened cases with unfavorable conditions for exercise. Higher % nasal contribution for female trainees was the reason for higher deposition in the anterior nose compared to male trainees. Linking these results with a health risk showed that females have an increased risk related to a health outcome in the upper respiratory tract whereas male trainees have increased risk for a health impact in the lungs. Overall, health risk analysis verified the negative impact of elevated PM concentrations and the enhanced risk accompanied by increased intensity for experienced trainees. To prevent negative health outcomes, trainees are recommended to practice in areas with reduced particulate pollution (e.g suburban areas) and during times of the day where concentrations are expected to be lower.

Αirborne microplastics (MPs) comprise an important exposure pathway to humans and an emerging health hazard. Published MP concentrations and size distributions were applied to a dosimetry model to determine their deposition and clearance in the human respiratory tract (HRT). Inhaled MPs deposited primarily in the extra-thoracic region with smaller MPs accumulated in the tracheobronchial and alveolar regions. The retained mass after exposure of one day was estimated to range from 5.2 × 10-4 to 9.48 μg based on different exposure concentrations. Moreover, after one day, approximately 60 % of the deposited MP mass was transferred from the respiratory tract to the oesophagus, 28 % was retained in the respiratory tract, 0.4 % passed into the blood, and a very small amount was transferred to the lymph nodes. Evaluating the long-term response of the dose accumulated in the HRT was governed by a steady-state condition where the accumulated dose reached a fixed value. Constant exposure conditions drove this observation yet in real world MP exposure is not constant and varies across environments and individuals. Analysis of different environments showed that higher dose is received indoors due to the higher measured MP concentrations. Further research is needed to unravel the impact of varying exposure conditions and inclusion of targeted MPs clearance kinetics to improve human body response to MP intake.

Floor mopping is a cleaning activity that provokes the release of various chemicals indoors. This study is aimed at estimating the emission rates of indoor particles and total volatile organic compounds (VOCs) using a chamber setting. Eight commercial cleaning products with different perfumes (lemon, lavender, jasmine, ocean fresh, green apple, and green soap) and categorized into two groups (chlorines and all-purpose cleaners) were tested. Fine particle concentrations (< 300 nm) were increased with all products, but nanoparticle formation was observed during bleach mopping and mopping with the lemon-perfumed cleaner. Emission rates were one order of magnitude higher with the lemon-perfumed cleaner (10(12) particles/h), followed by bleach mopping (10(11) particles/h) and the rest of the cleaners (10(10) particles/h). Likewise, significant emissions were obtained for VOCs, with higher emissions corresponding to the cleaners (1.2-3.4 mg/h) and especially the lemon product (5.2 mg/h), while for bleach mopping, emissions ranged between 1.2 and 3.8 mg/h again with higher emissions for the lemon-perfumed chlorine. Contrarily, PM2.5 preserved a minimal increase with primary emissions lying between 57 and 290 mu g/h, although a significant impact was identified during formation events. Using a higher concentration solution for mopping enhanced emissions of both particles and VOCs, emphasizing that careful dosage is needed to avoid increased rates. The current study demonstrates that the type and fragrances of cleaning products are critical in influencing emissions, with lemon-scented products potentially leading to more detrimental indoor exposure.

Atmospheric dust is an important contributor to atmospheric particulate matter (PM) and a significant factor to air quality degradation worldwide. In this study, we assess atmospheric dust as an air quality hazard to the world population. Near-surface dust concentrations are quantified through the synergy of the “LIdar climatology of Vertical Aerosol Structure” (LIVAS) atmospheric dust data record, established based on Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol profiles, and European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 information on planetary boundary layer (PBL). The health risk to the global population is estimated using empirically derived epidemiological exposure–response relationships that approximate the association between PM concentrations and adverse health outcomes. Our findings reveal elevated health risks in regions affected by major desert sources or over densely populated and highly industrialized regions. Approximately nine-out-of-ten (~91% or ~6.8 billion people) of the global population experience total dust concentrations below the World Health Organization (WHO) annual-mean PM10 guideline. However, a substantially larger proportion of approximately one-out-of-three (~33.5% or ~2.5 billion people) is exposed to submicrometer-mode dust concentrations exceeding the respective PM2.5 recommended threshold. The study highlights atmospheric dust as an important air quality hazard and demonstrates the value of satellite observations for assessing trustworthy health risks and supporting environmental policies.

Ensuring good indoor air quality in schools is essential for healthy child development. Airborne microplastics (MP) pollution has attracted increasing attention in recent years due to the potential negative impact on human health, especially in indoor environments where people spend approximately 90% of their time. The present study is one of the first to combine real classroom airborne microplastic measurements with respiratory deposition and clearance modelling, enabling a health-relevant evaluation of lung-deposited dose in children. We collected total suspended particles from indoor air in 5 primary schools (n = 25) across the urban area of Barcelona to assess MP concentrations and composition. Quantitative analysis was performed by pyrolysis coupled to gas chromatography high-resolution mass spectrometry, a size-unrestricted technique targeting ten polymer types. Total MP concentrations ranged from 64.9 ± 24.3 to 178.7 ± 47.7 ng/m3 with a mean value of 99.7 ± 44.4 ng/m3. Nylon 6,6 and nitrile butadiene rubber (NBR) were detected in all the samples, with NBR showing the highest concentrations (36.8 ± 14.1 to 109.6 ± 23.6 ng/m3). To evaluate potential health implications, the ExDoM2 dosimetry model based on the International Commission on Radiological Protection framework was applied to estimate respiratory deposition and clearance in children. On average, 32 ± 8 particles were deposited during an 8-h school day, corresponding to a mass dose of 254 ± 68 ng. After 24 h, 60-67% of the deposited mass was cleared to the gastrointestinal tract via mucociliary transport, and less than 1% was estimated to reach the bloodstream. These results highlight the relevance of inhalation exposure to MP in school environments and the necessity of additional research during critical developmental stages.

Two air quality monitoring devices (Bluesky, PurpleAir) equipped with low-cost sensors were investigated as particle monitoring devices and for personal exposure assessment and dose characterization. Raw sensor concentrations were corrected based on concentrations measured by reference instruments and for relative humidity levels. The dose received in the human respiratory tract was quantified through dosimetry simulations assuming exposure to the ambient environment. The corrected sensor concentrations exhibited a substantial improvement during wintertime which suggested better performance of the devices when the environment was significantly enriched with fine particles (heating emissions). Bluesky followed successfully PM10 trends when different sources were investigated (Sahara, heating, marine, mixed conditions) but high bias (22.1 mu g/m3) during Sahara implied its inability to measure accurately PM10 concentrations. i.e. coarser particles. On the contrary, PurpleAir preserved proportional relationship during heating (r = 0.96) but failed to catch PM2.5 variations during Sahara (r = -0.55) and mixed urban conditions (r = -0.40). Comparison of sensor and referenced daily deposited doses was non-negligible with absolute errors ranging between 16.8 and 133.1 mu g for Bluesky and between 17.4 and 36.7 mu g for PurpleAir, yet reduced errors were obtained during wintertime as a direct result of better sensor response. Environmental conditions investigation demonstrated the inability of both sensors to be used for dose characterization during Sahara events but reduced or even minimized bias was found in the other conditions. This study emphasizes that successful personal exposure assessment by low-cost sensors should rely on accurate particle mass measurements to provide equivalent to reference deposited doses under the varying exposure conditions.

NO, NO2, and O3 were measured for 1 year at a suburban site in the southeast Mediterranean. NO preserved no seasonality, but significant seasonal variations were obtained for NO2 and O3. These pollutants exhibited inverse trends with higher NO2 levels measured during wintertime, whilst higher O3 levels were measured during summertime. Photochemistry was the primary reason for the opposing variations in both pollutants, although O3 levels were frequently increased due to O3-rich plumes travelling from northeast Europe, highlighting the impact of regional contributions in the measured concentrations. Nevertheless, anthropogenic sources were identified and contributed to both NO and NO2. Diurnal variations analysis showed that NO increased usually in the early morning and was linked with primary emissions from traffic. NO2 increased simultaneously with NO in the early morning, and besides primary vehicle emissions, it was associated with secondary formation from the emitted NO. Moreover, a significant contribution from domestic heating emissions on NO2 was identified in the late evening during wintertime. Overall, a relative burden of weekdays was associated with NO (morning rush hours) and NO2 (morning rush hours, evening), whereas weekends were burdened by O3 due to the weekend effect. Comparison with European Union air quality standards showed that NO2 was considerably lower than the limit values, but a significant number of exceedances were identified for O3, especially during the warmer months. This finding suggested the relative burden of the study site from O3. In conclusion, NO at the study site was influenced by primary traffic emissions, whereas NO2 had both primary and secondary contributions, and together with photochemistry, both pollutants governed O3 diurnal and seasonal cycles.

According to the United Nations (UN) more than 55 % of the global population resided in urban areas in 2018, a number projected to increase to an estimated 60 % of the world's population by 2030. As urbanization accelerates, degradation of air quality becomes an increasing environmental pressure to human welfare and health. To date, epidemiological studies reveal a strong connection between airborne dust and adverse health effects. This study investigates the fine-mode and coarse-mode dust particulate matter levels within the planetary boundary layer (PBL) over major cities and megacities of the world (population > 5 million), leveraging on the European Space Agency (ESA) – “LIdar climatology of Vertical Aerosol Structure” (LIVAS) multiyear satellite-based dust climate data record. Results show that current dust levels exceed World Health Organization (WHO) annual-mean air quality guidelines (AQGs) for PM2.5 and PM10 in 49.4 % and 87.7 % of the cities considered, respectively, exposing ∼ 700 million people to hazardous dust concentrations. Moreover, according to the outcomes of the study, this number is expected to increase to ∼ 850 million individuals (∼ 22 % increase) by 2030s, though due to the general declining dust tendencies the health hazard is projected to be diminished in severity. Particularly affected are cities in the regions of Middle East, Indian subcontinent, East Asia, North Africa, and the Sahel. Epidemiological models are employed to estimate associated health risks. The study provides an informative mitigation and adaptation tool to support observational-based policymaking, air quality management, and public health planning to protect human health in the context of accelerating urbanization.

The regional deposited dose of ultrafine particles in the respiratory tract and their transport to the olfactory region was investigated through an existing particle dosimetry model (Exposure Dose Model 2, ExDoM2). The original dosimetry model was adapted to include a methodology that uses numerical modelling for the transport of ultrafine particles from the nose to the olfactory region. The mass dose to the oesophagus, blood, and lymph nodes was also calculated. Four different cases were studied: heating, traffic, nucleation events and background levels. The results showed that deposition in the olfactory region decreased with increasing particle size (from 0.40 % to 0.12 %). The majority of particles were estimated to penetrate into the thoracic region with 36 % of particles within the size range 14-33 nm deposited in the alveolar-interstitial region, followed by the tracheobronchial (21 %), the extrathoracic (11 %) and olfactory (<0.5 %) regions. In addition, a comparison between the mass, surface, and number doses indicated different governing sources such as a higher number dose was obtained during nucleation (10.5 x 10(8) particles), while higher mass (9.4 x 10(-2) mu g) and surface (7.1 x 10(12) nm(2)) dose was obtained during heating periods. Simulations also indicated that after clearance, 56.9 % of ultrafine particles were found in the alveolar region, a finding that is linked to their small size and low clearance rate of this region. Nevertheless, the dose per unit surface area and the dose per cell in the olfactory region were higher than in the alveolar-interstitial region.

The current study investigated the impact of Body Mass Index (BMI) on particle deposition and dose received in the human respiratory tract for three groups of exposed subjects (adult males, adult females and 10-year-old children). A dosimetry model, the Exposure Dose Model 2 (ExDoM2) was modified to take into account the subject’s BMI. BMI affects physiological parameters which in turn affect the deposition fraction and dose of particles in the respiratory tract. This study used literature data to incorporate the impact of BMI to physiological parameters. BMI influences particle deposition differently across different age groups and particle sizes. Higher BMI leads to higher particle deposition in children for all particle sizes while in adults BMI can either increase or decrease particle deposition depending on the particle size. Regarding particle dose, both mass dose of PM10 and number dose of ultrafine particles (UFPs) increased with increasing BMI due to the higher inhalation rates. These results highlight that obese subjects receive higher dose in the respiratory tract than health weight subjects. After particle clearance, the highest dose was observed in oesophagus with the dose increasing by 86.2

Cultural-based methods of bacteria and fungi and molecular identification of bacteria were combined with parallel continuous measurements of aerosol chemical composition, number size distribution, ice-nucleating concentration, and fluorescent particle size distribution and characteristics. Measurements took place at the Helmos Hellenic Atmospheric Aerosol and Climate Change Station (HAC)2, Greece, during the 2021 CALISHTO campaign. The objective was to characterize the microorganism levels at the (HAC)2 station and further investigate the associations between bioaerosols and aerosols in atmospheric processes that play a key role in the formation of ice crystals. Very low concentrations of viable, cultivable heterotrophic bacteria (4 ± 4 CFU/m3) were measured, whereas fast-growing fungi were not affected (182 ± 86 CFU/m3) by the environmental conditions at the station. The size distribution of heterotrophic bacteria was bimodal with peaks at fine (1.1-2.1 μm) and coarse size fractions (d > 7 μm), whereas airborne fungi exhibited a monomodal distribution (2.1-3.3 μm). Bacterial populations identified using 16S rRNA correlated well (r = 0.82) with the averaged concentrations of fluorescent particles (A and C channels). Strong correlations were obtained between total bacterial and particle volume concentrations of coarser fractions (>1 μm, 0.61-0.86), suggesting their strong presence in these sizes. No correlation was found with ice nuclei (INP) (r = -0.04) and low to medium negative correlations with the organics and ions (SO4 2-, NH4 +, NO3 -, Cl-) possibly due to their relatively lower sizes. In accordance with the culture-dependent analysis, relatively low total bacterial concentrations were determined by real-time PCR, with concentrations ranging from 33.4 to 117.2 GE/m3. High bacterial diversity was found with 123 bacterial Operational Taxonomy Units (OTUs) classified in 10 phyla, 16 classes, 56 families, and 78 genera. Origin of the air masses was a significant driver to bacterial communities. Enrichment of specific species such as and was observed during Saharan dust episodes, while in the presence of continental air masses, characteristic species such as Rhizobium sp., Corynebacterium sp., and had higher relative abundance. Our study provides a comprehensive analysis and quantification of the varying drivers and variability in microorganisms in high-altitude site.

New particle formation (NPF) events were investigated at a coastal suburban site (Chania, Greece) in eastern Mediterranean during May 2022-April 2023. The particle number size distribution was measured together with particulate matter (PM10) and gaseous pollutants (NO, NO2, O3). 16 NPF events (8 Class I and 8 Class II) were observed with higher occurrence on May (5 events), whereas no NPF event took place on winter months. On the other hand, 15 undefined events were identified with a higher number of events present in February. Increased frequency on warm months was associated with enhanced biogenic and photochemical activity. The average condensation sink, the formation and growth rate for all events was 0.007 s-1, 0.16 cm- 3 s-1 and 2.60 nmh- 1 respectively, without statistically significant differences between Class I and Class II events. The formation and growth rates were higher during the warm period. Nucleation particles (14 nm - 25 nm) preserved no seasonal variations but were significantly increased on periods with NPF activity. NPF activity was enhanced by the presence of condensable sinks that favored nanoparticle formation. Both the growth and the formation rates were positively correlated with solar radiation, temperature and wind speed. Two main factors were identified during NPF events: atmospheric conditions (solar radiation, temperature, wind speed and condensation sinks) and the urban environment (NO). NO2, O3 and PM10 were not associated with nucleation particles and NPF activity.

PM10 mass concentrations were measured online for one year at the Akrotiri monitoring station in Chania (Greece). PM10 concentrations ranged from 7.3 to 287.5 µg m− 3 with highest concentrations measured in April, due to intense dust episodes. Overall, a total of 50 events days were identified with most episodes taking place during the first semester of the year. The majority of PM10 exceedances (80

Extensive continuous particle number size distribution measurements took place during two summers (2020 and 2021) at 11 sites in Greece for the investigation of the frequency and the spatial extent of new particle formation (NPF). The study area is characterized by high solar intensity and fast photochemistry and has moderate to low fine particulate matter levels during the summer. The average PM2.5 levels were relatively uniform across the examined sites. The NPF frequency during summer varied from close to zero in the southwestern parts of Greece to more than 60 % in the northern, central, and eastern regions. The mean particle growth rate for each station varied between 3.4 and 8 nm h−1, with an average rate of 5.7 nm h−1. At most of the sites there was no statistical difference in the condensation sink between NPF event and non-event days, while lower relative humidity was observed during the events. The high-NPF-frequency sites in the north and northeast were in close proximity to both coal-fired power plants (high emissions of SO2) and agricultural areas with some of the highest ammonia emissions in the country. The southern and western parts of Greece, where NPF was infrequent, were characterized by low ammonia emissions, while moderate levels of sulfuric acid were estimated (107 molec. cm−3) in the west. Although the emissions of biogenic volatile organic compounds were higher in western and southern sectors, they did not appear to lead to enhanced frequency of NPF. The infrequent events at these sites occurred when the air masses had spent a few hours over areas with agricultural activities and thus elevated ammonia emissions. Air masses arriving at the sites directly from the sea were not connected with atmospheric NPF. These results support the hypothesis that ammonia and/or amines limit new particle formation in the study area.

Gaseous pollutant concentrations were monitored for one year in urban (NO, NO2, O3, CO, and SO2) and suburban (NO, NO2, and O3) sites. Common characteristics were identified at both sites, such as higher concentrations during typical winter months for all pollutants except O3. Increased NO, NO2, CO and SO2 concentrations during wintertime were linked to residential heating emissions, with pairwise correlations showing CO as marker for the study site. O3 production was lower in wintertime but higher in summertime at both sites based on its seasonal cycle and the impact of sunlight. Furthermore, diurnal variations showed that traffic emissions during rush hours most profoundly affected CO and NO. Nevertheless, NOx were characteristically higher at the urban site based on the burdened environment, whereas O3 was higher at the suburban site due to the lower destruction rates. O3 was the dominant oxidant at both sites, with a linear regression between OX and NOx revealing a negative relationship. This observation suggested a dominant regional contribution to oxidant concentrations. In addition, abnormally high O3 concentrations in relation to the season were reported for the first time at the study sites. Elevated concentrations were measured in parallel with Sahara dust events indicating noteworthy atmospheric conditions that require further assessment. Other O3 burdened periods were driven by regional transport of polluted plumes from the northeast. Lastly, nocturnal increases in O3 were observed and associated with enhanced vertical mixing.

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.

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.

Airborne particles are known climate drivers whilst the impact of microorganisms is investigated with increasing interest. The particle number size distribution (0.012–10 μm), PM10 concentrations, bacterial communities and cultivable microorganisms (bacteria and fungi) were measured simultaneously throughout a yearly campaign at a suburban location at the city of Chania (Greece). Most of the bacteria identified belonged to Proteobacteria, Actinobacteriota, Cyanobacteria, and Firmicutes, with Sphingomonas having a dominant partition at the genus level. Statistically lower concentrations of all microorganisms and bacterial species richness during the warm season due to the direct impact of temperature and solar radiation suggested notable seasonality. On the other hand, statistically significant higher concentrations of particles <0.1 μm during the cold season was attributed to indirect seasonality with enrichment due to heating emissions. Analysis of wind direction data demonstrated that a land prevailing origin of air resulted in statistically higher microorganism concentrations, bacterial species richness and diversity, indicating the continental environment as a dominant contributor in shaping airborne microbial load (compared to a marine air origin). Likewise, statistically higher concentration of particles <0.1 μm were measured during a land prevailing air origin as a direct result of nanoparticle enrichment from anthropogenic activities. Long-range transport of both particles and biological components was evidenced by the increased concentrations of cultivable microorganisms (with a distinct contribution at sizes >1 μm), supermicron particles and bacterial species richness during Sahara dust events. Factorial analysis of the impact of 7 environmental parameters on bacterial communities profile has identified temperature, solar radiation, wind origin and Sahara dust as strong contributors. Increased correlations between airborne microorganisms and coarser particles (0.5–10 μm) suggested resuspension, especially during stronger winds and moderate ambient humidity, whereas, increased relative humidity during stagnant conditions acted as inhibitor for suspension.

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.