Wildfire and African dust aerosol oxidative potential, exposure and dose in the human respiratory tract.

Exposure to wildfire smoke and dust can severely affect air quality and health. Although particulate matter (PM) levels and exposure are well-established metrics linking to health outcomes, they do not consider differences in particle toxicity or deposition location in the respiratory tract (RT). Usage of the oxidative potential (OP) exposure may further shape our understanding on how different pollution events impact health. Towards this goal, we estimate the aerosol deposition rates, OP and resulting OP deposition rates in the RT for a typical adult Caucasian male residing in Athens, Greece. We focus on a period when African dust (1-3 of August 2021) and severe wildfires at the northern part of the Attika peninsula and the Evia island, Greece (4-18 of August 2021) affected air quality in Athens. During these periods, the aerosol levels increased twofold leading to exceedances of the World Health Organization (WHO) [15(5) µg m-3] PM10 (PM2.5) air quality standard by almost 100 %. We show that the OP exposure is 1.5-times larger during the wildfire smoke events than during the dust intrusion, even if the latter was present in higher mass loads - because wildfire smoke has a higher specific OP than dust. This result carries two important implications: OP exposure should be synergistically used with other metrics - such as PM levels - to efficiently link aerosol exposure with the resulting health effects, and, certain sources of air pollution (in our case, exposure to biomass burning smoke) may need to be preferentially controlled, whenever possible, owing to their disproportionate contribution to OP exposure and ability to penetrate deeper into the human RT.

Variations, seasonal shifts and ambient conditions affecting airborne microorganisms and particles at a southeastern Mediterranean site.

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 Representativeness of Outdoor Particulate Matter Concentrations for Estimating Personal Dose and Health Risk Assessment of School Children in Lisbon.

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.

Mass concentrations and elemental analysis of PM2.5 and PM10 in a coastal Mediterranean site: A holistic approach to identify contributing sources and varying factors.

PM10 and PM2.5 were measured at a suburban coastal Mediterranean site. Daily mass concentrations were generally lower than the WHO air quality limits but showed significant diurnal and seasonal variations, with intensive African dust events and residential heating emissions during wintertime causing the higher % increase of ambient concentrations (32% and 59% respectively). However, analysis of the elemental content revealed intrinsic characteristics. Statistically significant seasonal variability was found for S with higher concentrations during warm seasons directly associated with the formation of secondary sulfates. Increased S was the driving reason for the significant depletion of both Cl and Br. On the other hand, elevated K during wintertime was attributed to biomass burning. Analysis of the mineral content of airborne particles showed that typical soil-derived particles were significantly increased during dust events (Mg, Al, Si, K, Ca, Ti, Mn, Fe) although the corresponding mass concentrations preserved relative low levels (<30 µg m-3). It was also found that dust events contributed to P, S, V, Zn, Sr and Pb with elemental ratios including Si (Si/Al, Si/Fe, Si/Ca) and Ca/Al serving as good markers for African dust. Heavy metals were found to have both direct and indirect influence on PM2.5 and PM10. PM2.5 were primarily enriched with metals produced from motor vehicles (Cu, Zn, Pb) and ships (V, Ni), whilst, PM10 enriched indirectly with Cr, Zn, Br and Pb due to road dust. At the end, source appointment has shown that the dominant contributing factor was mineral dust for both metrics (>30%) but significant contributions arose from secondary sulfates and traffic, (aged) sea salt, biomass burning (only for PM2.5) and road dust (only for PM10). Overall, this work provides a novel insight on the characteristics and chemical profile of atmospheric particles in a suburban environment largely affected by local, regional and long-range sources.

Lung-deposited dose of particulate matter from residential exposure to smoke from wood burning.

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.

Airborne particles and microorganisms in a dental clinic: Variability of indoor concentrations, impact of dental procedures, and personal exposure during everyday practice.

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.

Analysis of spatial factors, time-activity and infiltration on outdoor generated PM2.5 exposures of school children in five European cities.

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.

Personal deposited dose and its influencing factors at several Greek sites: an analysis in respect to seasonal and diurnal variations.

The deposited dose in the human respiratory tract and its influencing factors were investigated for 8 urban/suburban locations within Greek cities. A dosimetry model (ExDoM2) was implemented assuming a 24-h exposure scenario to ambient PM10 whereby regional deposition rates were obtained. Simulations were performed considering three cases (Sahara dust, cold, and warm periods) with seasonal and diurnal variations examining the relative sources and other influencing factors in each case. Health risk indexes such as the relative risk and attributable fraction were also estimated. Overall, higher daily deposited dose was obtained for all urban compared with suburban locations (p < 0.05) and for cold compared with the warm periods (252-820 µg for cold period and 300-686 µg for warm period) for all locations. This finding was associated with increased deposition rate on cold period during evening/night hours, as a result of significant heating emissions. Besides that, most of the urban locations showed relative comparable deposition rates during the day, compared with the daily mean, for the two periods (cold and warm), indicating that urban-associated sources such as exhaust emissions and road dust resuspension contribute similarly to the deposited dose irrespectively of the season. Finally, the highest deposited dose was obtained during Sahara dust events ranged from 1881 to 4648 µg.

Evaluation of nanoparticle emissions from a laser printer in an experimental chamber and estimation of the human particle dose.

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).

Manikin-based size-resolved penetrations of CE-marked filtering facepiece respirators.

The purpose of this manikin-based study was to determine the percentage penetrations of nine CE-marked filtering facepiece respirator models (two samples from each) from filtering classes FFP1, FFP2, and FFP3 and to demonstrate by an independent measurement method the disadvantages and shortcomings of the currently valid European Norm (EN 149:2001) for filtering facepieces. All of the filtering facepieces were evaluated size-selectively in an experimental chamber using charge-neutralized monodisperse ammonium sulfate in 9 sizes ranging from 20-400 nm of count median diameter (CMD) under flowrate of 95 L/min. The results were then compared to the previous study concerning penetrations of 47-mm diameter filters cut from the filtering material of identical filtering facepieces. Although these two experimental methods for measuring penetrations of filtering materials from filtering facepieces are in good agreement (R2 = 0.91), the results show within-respirator variations in all three filtering classes (5.5-19.3% for all FFRs in FFP1, 2.8-8.5% in FFP2, and 0.1-2.8% in FFP3). The most penetrating particle size (MPPS) in this study was found to be in the range of 25-65 nm (CMD), which is in agreement with the range of 30-60 nm found in the previous study. Moreover, 7 out of 9 FFR models reached higher penetrations from manikin-based respirator measurements than during measurements of filters from the respective respirators. Furthermore, penetration levels increased up to ∼50% when the respirator was not sealed around the face of the manikin, indicating that the real protection level provided by these filtering facepieces may be even lower if the respirator does not fit perfectly. Considering that poor filtration efficiency and poor fit may increase under real work conditions, the particle penetration is even higher than was found in this study. Therefore, the CE-marked respirators examined in this study may not be efficient in providing the expected level of protection for workers exposed to nanoparticles.

Development and application of a dosimetry model (ExDoM2) for calculating internal dose of specific particle-bound metals in the human body.

The objective of the current study was to develop a dosimetry model (ExDoM2) for calculating internal dose of specific particle-bound metals (As, Pb, Cd, Cr and Mn) in the human body. The ExDoM2 is a revised version of a respiratory tract model (ExDoM) incorporating a new particle clearance mechanism in the respiratory tract model and a Physiologically-Based PharmacoKinetic (PBPK) model. The revised respiratory tract model was used to calculate the deposition, clearance and retention of particles in the human respiratory tract and the mass transferred to the oesophagus (gastrointestinal tract) and blood. The PBPK module was used to analyze the distribution of metals (As, Pb, Cd, Cr and Mn) from the blood circulation system to other organs or tissues like liver, kidneys, heart, brain, muscle and bone. The model was applied to calculate the internal human dose for an adult Caucasian male exposed to particulate mass matter (PM), PMPb, PMCd, PMMn and PMCr in an urban area (Athens, Greece). The analysis showed that at the end of the exposure (one day exposure scenario) to PMPb, the major accumulation occurs in the bone, blood and muscle, whereas as regards PMCd the major accumulation occurs in the other tissues, like kidney and liver. In addition, for PMMn, the major accumulation occurs in the other tissues and lungs, whereas as regards PMCr the major accumulation occurs in the gastrointestinal (GI) tract and lungs. Therefore, ExDoM2 is an important feature in studying deposition of particles in the human body.

A methodology for the determination of fugitive dust emissions from landfill sites.

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%.

Assessing PM10 source reduction in urban agglomerations for air quality compliance.

The objective of this work was to study PM(10) and PM(2.5) concentration data available from monitoring stations in two large urban agglomerations in Greece and to estimate the emissions reduction required for compliance with the EU Air Quality Standards (AQS) for particulate matter. The cities studied are namely the Athens and Thessaloniki Metropolitan Areas (AMA and TMA, respectively). PM(10) concentrations during the period 2001-2010 have been evaluated for 15 air quality monitoring stations in the two urban areas. It was found that the concentrations of PM(10) during the period studied constantly exceeded the threshold values at the traffic and industrial stations in TMA and most of the traffic sites in AMA. Most of the occurrences of non-attainment to the daily AQSs were observed during the winter period at all stations (more pronounced for TMA stations). The reduction in current emission source strength to meet the air quality goal was calculated by the rollback equation using PM(10) day-averaged concentrations over the selected period at each station. Among the lognormal and Weibull distributions, the lognormal distribution was found to best fit the frequency distributions of PM(10) concentrations at the selected stations. The results showed that the minimum reduction required in order to meet the AQS in the AMA ranges from approximately 20 to 38% and up to 11% for traffic and background stations, respectively. Reductions in the range of 31% for traffic and 44% for industrial areas in TMA are also required. The same methodology was applied to PM(2.5) concentrations in the AMA and showed that emission reductions up to 31% are necessary in order to meet the 2020 EU AQS. Finally, continuous concentration data of organic (OC) and elementary carbon (EC) in PM(2.5) were used to study the possibility of achieving specific emission attenuation objectives in AMA.

Treatment of unpleasant odors in municipal wastewater treatment plants.

The purpose of this paper to present a case study on how to address the odor problem from secondary sources within a municipal wastewater treatment plant (WWTP) by first identifying the locations of the problem and second by evaluating alternative treatment technologies. The WWTP of Chania is a typical 100,000 equivalent inhabitants-facility in a warm semi-arid environment which is located close to residential areas. The installation of a chemical scrubber to control major odor sources within the plant did not succeed in eliminating complaints by nearby residents, and additional measures were required. In this case study we identify all major secondary sources of odor within the plant and evaluate the effectiveness of the different technologies that were employed to address this problem (cover installation, gas and liquid phase oxidation, activated carbon/permanganate absorption, FeCl(3) addition). In particular, we found that installation of covers and reduction of turbulence at two key locations within the WWTP was the best strategy to combat unpleasant odors. Furthermore, when the central chemical scrubber was near capacity the installation of an auxiliary system of activated carbon absorption coupled to permanganate oxidation was deemed to be a safe approach. However, despite the very high removal efficiency (>99.5%) of the unit, the addition of FeCl(3) in the liquid phase was required in order to achieve complete deodorization (below the human odor threshold level).

Aerosols and environmental pollution.

The number of publications on atmospheric aerosols has dramatically increased in recent years. This review, predominantly from a European perspective, summarizes the current state of knowledge of the role played by aerosols in environmental pollution and, in addition, highlights gaps in our current knowledge. Aerosol particles are ubiquitous in the Earth's atmosphere and are central to many environmental issues; ranging from the Earth's radiative budget to human health. Aerosol size distribution and chemical composition are crucial parameters that determine their dynamics in the atmosphere. Sources of aerosols are both anthropogenic and natural ranging from vehicular emissions to dust resuspension. Ambient concentrations of aerosols are elevated in urban areas with lower values at rural sites. A comprehensive understanding of aerosol ambient characteristics requires a combination of measurements and modeling tools. Legislation for ambient aerosols has been introduced at national and international levels aiming to protect human health and the environment.

Characterization and dispersion modeling of odors from a piggery facility.

Piggeries are known for their nuisance odors, creating problems for workers and nearby residents. Chemical substances that contribute to these odors include sulfurous organic compounds, hydrogen sulfide, phenols and indoles, ammonia, volatile amines, and volatile fatty acids. In this work, daily mean concentrations of ammonia (NH3) and hydrogen sulfide (H2S) were measured by hand-held devices. Measurements were taken in several places within the facility (farrowing to finishing rooms). Hydrogen sulfide concentration was found to be 40 to 50 times higher than the human odor threshold value in the nursery and fattening room, resulting in strong nuisance odors. Ammonia concentrations ranged from 2 to 18 mL m(-3) and also contributed to the total odor nuisance. Emission data from various chambers of the pig farm were used with the dispersion model AERMOD to determine the odor nuisance caused due to the presence of H2S and NH3 to receptors at various distances from the facility. Because just a few seconds of exposure can cause an odor nuisance, a "peak-to-mean" ratio was used to predict the maximum odor concentrations. Several scenarios were examined using the modified AERMOD program, taking into account the complex terrain around the pig farm.

Inorganic and carbonaceous components in indoor/outdoor particulate matter in two residential houses in Oslo, Norway.

A detailed analysis of indoor/outdoor physicochemical aerosol properties has been performed. Aerosol measurements were taken at two dwellings, one in the city center and the other in the suburbs of the Oslo metropolitan area, during summer/fall and winter/spring periods of 2002-2003. In this paper, emphasis is placed on the chemical characteristics (water-soluble ions and carbonaceous components) of fine (PM2.5) and coarse (PM2.5-10) particles and their indoor/outdoor relationship. Results demonstrate that the carbonaceous species were dominant in all fractions of the PM10 particles (cut off size: 0.09-11.31 microm) during all measurement periods, except winter 2003, when increased concentrations of water-soluble inorganic ions were predominant because of sea salt transport. The concentration of organic carbon was higher in the fine and coarse PM10 fractions indoors, whereas elemental carbon was higher indoors only in the coarse fraction. In regards to the carbonaceous species, local traffic and secondary organic aerosol formation were, probably, the main sources outdoors, whereas indoors combustion activities such as preparation of food, burning of candles, and cigarette smoking were the main sources. In contrast, the concentrations of water-soluble inorganic ions were higher outdoors than indoors. The variability of water-soluble inorganic ion concentrations outdoors was related to changes in emissions from local anthropogenic sources, long-range transport of particles, sea salt emissions, and resuspension of roadside and soil dusts. In the indoor environment the infiltration of the outdoor air indoors was the major source of inorganic ions.

Quantification of landfill emissions to air: a case study of the Ano Liosia landfill site in the greater Athens area.

Fugitive pollutant emissions from municipal solid waste landfills have the potential to cause annoyance and health impacts in the surrounding residential areas. The overall objective of this research was to perform an assessment of fugitive pollutant emissions and a dispersion analysis downwind of a specific landfill site. The study was performed at the closed Ano Liosia landfill site which is located in the greater Athens area. The human exposure from priority to health-risk pollutants emitted from landfill, such as vinyl chloride and benzene, was estimated by the landfill gas emission LandGEM 2.01 software combined with the atmospheric long-term dispersion model ISC3-LT. The emission and meteorological conditions under which the models were applied referred to the worst-case scenario. This scenario was used for the evaluation of the maximum human exposure assessed beyond the Ano Liosia landfill towards the residential areas. The above scenario provides the minimum downwind distance of the health-risk zone which is calculated to be equal to 1.5 km from the landfill. Within this distance the assessed air pollutant concentration for several air pollutants was significantly above the World Health Organization reference lifetime exposure health criteria. Finally, the applied methodology was used in the Ano Liosia landfill, where atmospheric concentrations of pollutants measured in the field were compared with model predictions.

Requirements for developing a regional monitoring capacity for aerosols in Europe within EMEP.

The European Monitoring and Evaluation Programme (EMEP) has been established to provide information to Parties to the Convention on Long Range Transboundary Air Pollution on deposition and concentration of air pollutants, as well as on the quantity and significance of long-range transmission of pollutants and transboundary fluxes. To achieve its objectives with the required scientific credibility and technical underpinning, a close integration of the programme's main elements is performed. These elements are emission inventories, chemical transport modelling, and the monitoring of atmospheric chemistry and deposition fluxes, which further are integrated towards abatement policy development. A critical element is the air pollution monitoring that is performed across Europe with a focus not only on health effect aspects and compliance monitoring, but also on process studies and source receptor relationships. Without a strong observational basis a predictive modelling capacity cannot be developed and validated. Thus the modelling success strongly depends on the quality and quantity of available observations. Particulate matter (PM) is a relatively recent addition to the EMEP monitoring programme, and the network for PM mass observations is still evolving. This article presents the current status of EMEP aerosol observations, followed by a critical evaluation in view of EMEP's main objectives and its model development requirements. Specific recommendations are given for improving the PM monitoring programme within EMEP.

Measurements of particulate matter within the framework of the European Monitoring and Evaluation Programme (EMEP) I. First results.

Particulate matter (PM) monitoring presents a new challenge to the transboundary air pollution strategies in Europe. Evidence for the role of long-range transport of particulate matter and its significant association with a wide range of adverse health effects has urged for the inclusion of particulate matter within the European Monitoring and Evaluation Programme (EMEP) framework. Here we review available data on PM physico-chemical characteristics within the EMEP framework. In addition we identify future research needs for the characterisation of the background PM in Europe that include detailed harmonised measurements of mass, size and chemical composition (mass closure) of the ambient aerosol.