Showing papers by "Lidia Morawska published in 2009"

The mechanism of breath aerosol formation.

Abstract: Background: Aerosol production during normal breathing is often attributed to turbulence in the respiratory tract. That mechanism is not consistent with a high degree of asymmetry between aerosol production during inhalation and exhalation. The objective was to investigate production symmetry during breathing. Methods: The aerosol size distribution in exhaled breath was examined for different breathing patterns including normal breathing, varied breath-holding periods, and contrasting inhalation and exhalation rates. The aerosol droplet size distribution measured in the exhaled breath was examined in real time using an aerodynamic particle sizer. Results and Conclusions: The dependence of the particle concentration decay rate on diameter during breath holding was consistent with gravitational settling in the alveolar spaces. Also, deep exhalation resulted in a four- to sixfold increase in concentration, and rapid inhalation produced a further two- to threefold increase in concentration. In contra...

Particle emission factors during cooking activities

Abstract: Exposure to particles emitted by cooking activities may be responsible for a variety of respiratory health effects. However, the relationship between these exposures and their subsequent effects on health cannot be evaluated without understanding the properties of the emitted aerosol or the main parameters that influence particle emissions during cooking. Whilst traffic-related emissions, stack emissions and ultrafine particle concentrations (UFP, diameter < 100 nm) in urban ambient air have been widely investigated for many years, indoor exposure to UFPs is a relatively new field and in order to evaluate indoor UFP emissions accurately, it is vital to improve scientific understanding of the main parameters that influence particle number, surface area and mass emissions. The main purpose of this study was to characterise the particle emissions produced during grilling and frying as a function of the food, source, cooking temperature and type of oil. Emission factors, along with particle number concentrations and size distributions were determined in the size range 0.006-20 m using a Scanning Mobility Particle Sizer (SMPS) and an Aerodynamic Particle Sizer (APS). An infrared camera was used to measure the temperature field. Overall, increased emission factors were observed to be a function of increased cooking temperatures. Cooking fatty foods also produced higher particle emission factors than vegetables, mainly in terms of mass concentration, and particle emission factors also varied significantly according to the type of oil used.

An investigation into the characteristics and formation mechanisms of particles originating from the operation of laser printers.

Abstract: While current research has demonstrated that the operation of some laser printers results in emission of high concentrations of ultrafine particles, fundamental gaps in knowledge in relation to the emissions still remain. In particular, there have been no answers provided to questions such as the following: (1) What is the composition of the particles? (2) What are their formation mechanisms? (3) Why are some printers high emitters, while others are low? Considering the widespread use of printers and human exposure to these particles, understanding the process of particle formation is of critical importance. This study, using state-of-the-art instrumental methods, has addressed these three points. We present experimental evidence that indicates that intense bursts of particles are associated with temperature fluctuations and suggest that the difference between high and low emitters lies in the speed and sophistication of the temperature control. We have also shown, for the first time, that the particles are volatile and are of secondary nature, being formed in the air from VOC originating from both the paper and hot toner. Some of the toner is initially deposited on the fuser roller, after which the organic compounds evaporate and then form particles, through one of two main reaction pathways: homogeneous nucleation or secondary particle formation involving ozone.

New particle formation and growth at a remote, sub-tropical coastal location

Abstract: . A month-long intensive measurement campaign was conducted in March/April 2007 at Agnes Water, a remote coastal site just south of the Great Barrier Reef on the east coast of Australia. Particle and ion size distributions were continuously measured during the campaign. Coastal nucleation events were observed in clean, marine air masses coming from the south-east on 65% of the days. The events usually began at ~10:00 local time and lasted for 1–4 h. They were characterised by the appearance of a nucleation mode with a peak diameter of ~10 nm. The freshly nucleated particles grew within 1–4 h up to sizes of 20–50 nm. The events occurred when solar intensity was high (~1000 W m−2) and RH was low (~60%). Interestingly, the events were not related to tide height. The volatile and hygroscopic properties of freshly nucleated particles (17–22.5 nm), simultaneously measured with a volatility-hygroscopicity-tandem differential mobility analyser (VH-TDMA), were used to infer chemical composition. The majority of the volume of these particles was attributed to internally mixed sulphate and organic components. After ruling out coagulation as a source of significant particle growth, we conclude that the condensation of sulphate and/or organic vapours was most likely responsible for driving particle growth at sizes greater than 10 nm during the nucleation events. Although there was a possibility that the precursor vapours responsible for particle formation and growth had continental sources, on the balance of available data we would suggest that the precursors were most likely of marine/coastal origin. Furthermore, a unique and particularly strong nucleation event was observed during northerly wind. The event began early one morning (08:00) and lasted almost the entire day resulting in the production of a large number of ~80 nm particles (average modal concentration during the event was 3200 cm−3). The Great Barrier Reef was the most likely source of precursor vapours responsible for this event.

Ultrafine particles in indoor air of a school: possible role of secondary organic aerosols.

Abstract: The aim of this work was to investigate ultrafine particles (<0.1 microm) in primary school classrooms, in relation to the classroom activities. The investigations were conducted in three classrooms during two measuring campaigns, which together encompassed a period of 60 days. Initial investigations showed that under the normal operating conditions of the school there were many occasions in all three classrooms where indoor particle concentrations increased significantly compared to outdoor levels. By far the highest increases in the classroom resulted from art activities (painting, gluing, and drawing), at times reaching over 1.4 x 10(5) particle cm(-3). The indoor particle concentrations exceeded outdoor concentrations by approximately 1 order of magnitude, with a count median diameter ranging from 20 to 50 nm. Significant increases also occurred during cleaning activities, when detergents were used. GC-MS analysis conducted on 4 samples randomly selected from about 30 different paints and glues, as well as the detergent used in the school, showed that d-limonene was one of the main organic compounds of the detergent, however, it was not detected in the samples of the paints and the glue. Controlled experiments showed that this monoterpene, emitted from the detergent, reacted with O(3) (at outdoor ambient concentrations ranging from 0.06 to 0.08 ppm) and formed secondary organic aerosols. Further investigations to identify other liquids that may be potential sources of the precursors of secondary organic aerosols were outside the scope of this project, however, it is expected that the problem identified by this study could be more widely spread, since most primary schools use liquid materials for art classes, and all schools use detergents for cleaning. Further studies are therefore recommended to better understand this phenomenon and also to minimize exposure of school children to ultrafine particles from these indoor sources.

Particle and Gaseous Emissions from Commercial Aircraft at Each Stage of the Landing and Takeoff Cycle

Abstract: A novel technique was used to measure emission factors for commonly used commercial aircraft including a range of Boeing and Airbus airframes under real world conditions. Engine exhaust emission factors for particles in terms of particle number and mass (PM2.5), along with those for CO2, and NOx were measured for over 280 individual aircraft during the various modes of landing/takeoff (LTO) cycle. Results from this study show that particle number, and NOx emission factors are dependant on aircraft engine thrust level. Minimum and maximum emissions factors for particle number, PM2.5, and NOx emissions were found to be in the range of 4.16×1015-5.42×1016 kg-1, 0.03-0.72 g.kg-1, and 3.25-37.94 g.kg-1 respectively for all measured airframes and LTO cycle modes. Number size distributions of emitted particles for the naturally diluted aircraft plumes in each mode of LTO cycle showed that particles were predominantly in the range of 4 to 100 nm in diameter in all cases. In general, size distributions exhibit similar modality during all phases of the LTO cycle. A very distinct nucleation mode was observed in all particle size distributions, except for taxiing and landing of A320 aircraft. Accumulation modes were also observed in all particle size distributions. Analysis of aircraft engine emissions during LTO cycle showed that aircraft thrust level is considerably higher during taxiing than idling suggesting that International Civil Aviation Organization (ICAO) standards need to be modified as the thrust levels for taxi and idle are considered to be the same (7% of total thrust) [1].

JEM Spotlight: Environmental monitoring of airborne nanoparticles

Abstract: The aim of this work was to review the existing instrumental methods to monitor airborne nanoparticles in different types of indoor and outdoor environments in order to detect their presence and to characterise their properties. Firstly the terminology and definitions used in this field are discussed, which is followed by a review of the methods to measure particle physical characteristics including number, concentration, size distribution and surface area. An extensive discussion is provided on the direct methods for particle elemental composition measurements, as well as on indirect methods providing information on particle volatility and solubility, and thus in turn on volatile and semivolatile compounds of which the particle is composed. A brief summary of broader considerations related to nanoparticle monitoring in different environments concludes the paper.

Temperature enhanced effects of ozone on cardiovascular mortality in 95 large US communities, 1987-2000: Assessment using the NMMAPS data.

Abstract: A few studies examined interactive effects between air pollution and temperature on health outcomes. In this study, the authors aimed to examine whether temperature modified effects of ozone on cardiovascular mortality in 95 large US cities. The authors separately used a nonparametric regression model and a parametric regression model to explore interactive effects of temperature and ozone on cardiovascular mortality between May and October of the years from 1987 to 2000. The authors used a Bayesian meta-analysis to pool estimates. The nonparametric and parametric regression models both showed that temperature enhanced effects of ozone on mortality, but the effect modification varied across regions. A 10-ppb increment in average ozone concentration at 3 previous days was associated with 0.41% (95% posterior interval [PI]: -0.19%, 0.93%), 0.27% (95% PI: -0.44%, 0.87%), and 1.68% (95% PI: 0.07%, 3.26%) increases in daily cardiovascular mortality corresponding to low, moderate, and high levels of temperature in all 95 US cities, respectively. The authors concluded that temperature modified effects of ozone, particularly in the northern regions.

Development of a particle number and particle mass vehicle emissions inventory for an urban fleet

Abstract: Motor vehicles are major emitters of gaseous and particulate matter pollution in urban areas, and exposure to particulate matter pollution can have serious health effects, ranging from respiratory and cardiovascular disease to mortality. Motor vehicle tailpipe particle emissions span a broad size range from 0.003 to 10@mm, and are measured as different subsets of particle mass concentrations or particle number count. However, no comprehensive inventories currently exist in the international published literature covering this wide size range. This paper presents the first published comprehensive inventory of motor vehicle tailpipe particle emissions covering the full size range of particles emitted. The inventory was developed for urban South-East Queensland by combining two techniques from distinctly different disciplines, from aerosol science and transport modelling. A comprehensive set of particle emission factors were combined with transport modelling, and tailpipe particle emissions were quantified for particle number (ultrafine particles), PM"1, PM"2"."5 and PM"1"0 for light and heavy duty vehicles and buses. A second aim of the paper involved using the data derived in this inventory for scenario analyses, to model the particle emission implications of different proportions of passengers travelling in light duty vehicles and buses in the study region, and to derive an estimate of fleet particle emissions in 2026. It was found that heavy duty vehicles (HDVs) in the study region were major emitters of particulate matter pollution, and although they contributed only around 6% of total regional vehicle kilometres travelled, they contributed more than 50% of the region's particle number (ultrafine particles) and PM"1 emissions. With the freight task in the region predicted to double over the next 20 years, this suggests that HDVs need to be a major focus of mitigation efforts. HDVs dominated particle number (ultrafine particles) and PM"1 emissions; and LDV PM"2"."5 and PM"1"0 emissions. Buses contributed approximately 1-2% of regional particle emissions.

On-road ultrafine particle concentration in the M5 East road tunnel, Sydney, Australia

Abstract: The human health effects following exposure to ultrafine (<100nm) particles (UFPs) produced by fuel combustion, while not completely understood, are generally regarded as detrimental. Road tunnels have emerged as locations where maximum exposure to these particles may occur for the vehicle occupants using them. This study aimed to quantify and investigate the determinants of UFP concentrations in the 4km twin-bore (eastbound and westbound) M5 East tunnel in Sydney, Australia. Sampling was undertaken using a condensation particle counter (CPC) mounted in a vehicle traversing both tunnel bores at various times of day from May through July, 2006. Supplementary measurements were conducted in February, 2008. Over three hundred transects of the tunnel were performed, and these were distributed evenly between the bores. Additional comparative measurements were conducted on a mixed route comprising major roads and shorter tunnels, all within Sydney. Individual trip average UFP concentrations in the M5 East tunnel bores ranged from 5.53 × 104 p cm-3 to 5.95 × 106 p cm-3. Data were sorted by hour of capture, and hourly median trip average (HMA) UFP concentrations ranged from 7.81 × 104 p cm-3 to 1.73 × 106 p cm-3. Hourly median UFP concentrations measured on the mixed route were between 3.71 × 104 p cm-3 and 1.55 × 105 p cm-3. Hourly heavy diesel vehicle (HDV) traffic volume was a very good determinant of UFP concentration in the eastbound tunnel bore (R2 = 0.87), but much less so in the westbound bore (R2 = 0.26). In both bores, the volume of passenger vehicles (i.e. unleaded gasoline-powered vehicles) was a significantly poorer determinant of particle concentration. When compared with similar studies reported previously, the measurements described here were among the highest recorded concentrations, which further highlights the contribution road tunnels may make to the overall UFP exposure of vehicle occupants.

Increase in particle number emissions from motor vehicles due to interruption of steady traffic flow

Abstract: We assess the increase in particle number emissions from motor vehicles driving at steady speed when forced to stop and accelerate from rest. Considering the example of a signalized pedestrian crossing on a two-way single-lane urban road, we use a complex line source method to calculate the total emissions produced by a specific number and mix of light petrol cars and diesel passenger buses and show that the total emissions during a red light is significantly higher than during the time when the light remains green. Replacing two cars with one bus increased the emissions by over an order of magnitude.

An investigation of nucleation events in a coastal urban environment in the Southern Hemisphere

Abstract: . Ambient aerosols play an important role in atmospheric processes affecting the human and natural environments. They affect air quality, reduce visibility, and induce climate change by directly scattering and/or absorbing the incoming solar radiation (Charlson et al., 1992; Kim et al., 2006), or indirectly by acting as cloud condensation nuclei (Hobbs, 1993). Aerosol particles are emitted from a variety of anthropogenic and natural sources either directly into the atmosphere or as secondary particles by gas-to-particle formation process. There is growing interest in studying and analysing the mechanisms of formation of secondary particles. The development of new instruments during the 1990s to measure the particle size distribution of nanoparticles ( It has been shown that the probability of nucleation was increased by elevated sulphur dioxide (SO2) concentrations (Stanier et al., 2004). This gas is mainly emitted from anthropogenic sources such as the combustion of sulphur-containing fossil fuel (Stern, 2005). Therefore, aerosol nucleation in the atmosphere would be expected to be enhanced by human activities (see also Curtius (2006) for discussion). In urban air, morning nucleation events have been found to be consistent with peaks in traffic (Jeong et al., 2004). In contrast, in coastal environments, higher concentrations of nucleation mode particles have been observed during entries of clean air rather than of polluted air (O'Dowd et al., 2002). This is also confirmed by a Finish study (Spracklen et al., 2006), which found that particle concentrations in remote continental regions are dominated by nucleated particles whereas in polluted continental regions are dominated by primary particles. This paper aims to analyse the frequency of and the atmospheric conditions favourable for nucleation events at coastal urban location in Brisbane, Australia, with a focus on the contribution of vehicle emissions. Monitoring was conducted during four campaigns of two weeks duration each, and a campaign of four weeks duration, covering a total period of 13 months. The objective was to investigate which meteorological conditions enhanced the probability of nucleation and to investigate any patterns in gaseous concentrations leading to the events to determine whether the local traffic was a major source of secondary particles in the study area.

An investigation of nucleation events in a coastal urban environment

Abstract: Ambient aerosols play an important role in atmo- spheric processes affecting the human and natural environ- ments. They affect air quality, reduce visibility, and induce climate change by directly scattering and/or absorbing the incoming solar radiation (Charlson et al., 1992; Kim et al., 2006), or indirectly by acting as cloud condensation nuclei (Hobbs, 1993). Aerosol particles are emitted from a variety of anthropogenic and natural sources either directly into the atmosphere or as secondary particles by gas-to-particle for- mation process. There is growing interest in studying and analysing the mechanisms of formation of secondary particles. The devel- opment of new instruments during the 1990s to measure the particle size distribution of nanoparticles (<50 nm) has en- abled scientists to observe the formation and growth of new particles (see Kulmala et al. (2004) for review). Nucleation

Deposition of combustion aerosols in the human respiratory tract: Comparison of theoretical predictions with experimental data considering nonspherical shape

Abstract: Total deposition of petrol and diesel combustion aerosols and environmental tobacco smoke (ETS) particles in the human respiratory tract for nasal breathing conditions was computed for 14 nonsmoking volunteers, considering the specific pulmonary function parameters of each volunteer and the specific size distribution for each inhalation experiment. Theoretical predictions were 34.6% for petrol smoke, 24.0% for diesel smoke, and 18.5% for ETS particles. Compared to the experimental results, predicted deposition values were consistently smaller than the measured data (41.4% for petrol smoke, 29.6% for diesel smoke, and 36.2% for ETS particles). The apparent discrepancy between experimental data on total deposition and modeling results may be reconciled by considering the nonspherical shape of the test aerosols by diameter-dependent dynamic shape factors to account for differences between mobility-equivalent and volume-equivalent or thermodynamic diameters. While the application of dynamic shape factors is able to explain the observed differences for petrol and diesel combustion particles, additional mechanisms may be required for ETS particle deposition, such as the size reduction upon inspiration by evaporation of volatile compounds and/or condensation-induced restructuring, and, possibly, electrical charge effects.

Comparison of ultrafine particle release from hardcopy devices in emission test chambers and office rooms

Abstract: The release of ultrafine particles (UFP) from laser printers and office equipment was analyzed using a particle counter (FMPS; Fast Mobility Particle Sizer) with a high time resolution, as well as the appropriate mathematical models. Measurements were carried out in a 1 m³ chamber, a 24 m³ chamber and an office. The time-dependent emission rates were calculated for these environments using a deconvolution model, after which the total amount of emitted particles was calculated. The total amounts of released particles were found to be independent of the environmental parameters and therefore, in principle, they were appropriate for the comparison of different printers. On the basis of the time-dependent emission rates, “initial burst” emitters and constant emitters could also be distinguished. In the case of an “initial burst” emitter, the comparison to other devices is generally affected by strong variations between individual measurements. When conducting exposure assessments for UFP in an office, the spatial distribution of the particles also had to be considered. In this work, the spatial distribution was predicted on a case by case basis, using CFD simulation.

Ultrafine particles in indoor air of a school : possible role of secondary organic aerosols

Abstract: The aim of this work was to investigate ultrafine particles (< 0.1 μm) in primary school classrooms, in relation to the classrooms activities. The investigations were conducted in three classrooms during two measuring campaigns, which together encompassed a period of 60 days. Initial investigations showed that under the normal operating conditions of the school there were many occasions in all three classrooms where indoor particle concentrations increased significantly compared to outdoor levels. By far the highest increases in the classroom resulted from art activities (painting, gluing and drawing), at times reaching over 1.4 x 105 particle cm-3. The indoor particle concentrations exceeded outdoor concentrations by approximately one order of magnitude, with a count median diameter ranging from 20-50 nm. Significant increases also occurred during cleaning activities, when detergents were used. GC-MS analysis conducted on 4 samples randomly selected from about 30 different paints and glues, as well as the detergent used in the school, showed that d-limonene was one of the main organic compounds of the detergent, however, it was not detected in the samples of the paints and the glue. Controlled experiments showed that this monoterpene, emitted from the detergent, reacted with O3 (at outdoor ambient concentrations ranging from 0.06-0.08ppm) and formed secondary organic aerosols. Further investigations to identify other liquids which may be potential sources of the precursors of secondary organic aerosols, were outside the scope of this project, however, it is expected that the problem identified by this study could be more widely spread, since most primary schools use liquid materials for art classes, and all schools use detergents for cleaning. Further studies are therefore recommended to better understand this phenomenon and also to minimize school children exposure to ultrafine particles from these indoor sources.

The role of sulphates and organic vapours in new particle formation in a eucalypt forest

Abstract: The influence of biogenic particle formation on climate is a well recognized phe-nomenon. To understand the mechanisms underlying the biogenic particle formation,determining the chemical composition of the new particles and therefore the species 5 that drive the particle production is of utmost importance. Due to the very small amountof mass involved, indirect approaches are frequently used to infer the composition. Wepresent here the results of such an indirect approach by simultaneously measuringvolatile and hygroscopic properties of newly formed particles in a forest environment.We that the particles are composed of both sulphates and organics, with the amount of 10 sulphatecomponentstronglydependingontheavailablegas-phasesulphuricacid, andthe organic components being photo-oxidation products of most likely a monoterpene.Our findings confirm a two-step process through nucleation and cluster formation fol-lowed by simultaneous growth by condensation of sulphates and organics that take theparticles to climatically relevant sizes.

Environmental monitoring of airborne nanoparticles

Abstract: The aim of this work was to review the existing instrumental methods to monitor airborne nanoparticle in different types of indoor and outdoor environments in order to detect their presence and to characterise their properties. Firstly the terminology and definitions used in this field are discussed, which is followed by a review of the methods to measure particle physical characteristics including number concentration, size distribution and surface area. An extensive discussion is provided on the direct methods for particle elemental composition measurements, as well as on indirect methods providing information on particle volatility and solubility, and thus in turn on volatile and semivolatile compounds of which the particle is composed. A brief summary of broader considerations related to nanoparticle monitoring in different environments concludes the paper.

Variation in indoor particle number and PM2.5 concentrations in a radio station surrounded by busy roads before and after an upgrade of the HVAC system

Abstract: Indoor particle number and PM2.5 concentrations were investigated in a radio station surrounded by busy roads. Two extensive field measurement campaigns were conducted to determine the critical parameters affecting indoor air quality. The results indicated that indoor particle number and PM2.5 concentrations were governed by outdoor air, and significantly affected by the location of air intake and design of HVAC system. Prior to the upgrade of the HVAC system and relocation of the air intake, the indoor median particle number concentration was 7.4 ×103 particle/cm3 and the median PM2.5 concentration was 7µg/m3. After the relocation of air intake and the redesign of the HVAC system, the indoor particle number concentration was between 2.3×103 and 3.4×103 particle/cm3, with a median value of 2.7×103 particle/cm3; and the indoor PM2.5 concentration was in the range of 3 - 5µg/m3, with a median value of 4µg/m3. By relocating the air intake of the HVAC, the outdoor particle number and PM2.5 concentrations near the air intake were reduced by 35% and 55%, respectively. In addition, with the relocation of air intake and the redesign of the HVAC system, the particle number penetration rate was reduced from 42% to 14%, and the overall filtration efficiency of the HVAC system (relocation of air intake, pre-filter, AHU and particle losses in the air duct) increased from 58% to 86%. For PM2.5, the penetration rate after the upgrade was approximately 18% and the overall filtration efficiency was 82%. This study demonstrates that by using a comprehensive approach, including the assessment of outdoor conditions and characterisation of ventilation and filtration parameters, satisfactory indoor air quality can be achieved, even for those indoor environments facing challenging outdoor air conditions.