Health risk assessment for traffic policemen exposed to polycyclic aromatic hydrocarbons (PAHs) in Tianjin, China

In China, traffic policemen have to stand for several hours a day at the road intersections with high vehicle flows. To assess their exposure to airborne carcinogenic polycyclic aromatic hydrocarbons (PAHs) during their working time, a preliminary study was conducted to measure the personal exposure level to PAHs. And a probabilistic incremental lifetime cancer risk (ILCR) model together with the benzo[a]pyrene (BaP) toxic equivalents (BaP(eq)) method was used to conduct health risk assessment. Personal exposure monitors (PEM) were carried by traffic policemen to collect PM10 samples during their daily work in Tianjin, China. Meanwhile, PM100 samples were collected at the roadsides and on campus of Nankai University as comparison. PAHs species were quantitatively analyzed by GC/MS. Experimental results showed that the concentrations of total PAHs, BaP and BaP(eq) were much higher at the road intersections (867.5, 26.2, 82.4 ng m(-3)), where the traffic policemen stand during their work time, than those at the roadsides (46.6, 1.5, 5.7 ng m(-3)), and on campus (19.5, 0.7, 2.4 ng m(-3)). According to the risk assessment results, the occupational risk falls within the range from 10(-6) to 10(-3). On the basis of sensitivity analysis results, further research should be directed to give better characterization of the yearly concentration distribution of PAHs and the cancer slope factor (CSF) of BaP in order to improve the accuracy of the health risk assessment.     

Real‐Time Estimation of Pollution Emissions and Dispersion from Highway Traffic

Traffic‐related air pollution is a serious problem with significant health impacts in both urban and suburban environments. Despite an increased realization of the negative impacts of air pollution, assessing individuals' exposure to traffic‐related air pollution remains a challenge. Obtaining high‐resolution estimates are difficult due to the spatial and temporal variability of emissions, the dependence on local atmospheric conditions, and the lack of monitoring infrastructure. This presents a significant hurdle to identifying pollution concentration hot spots and understanding the emission sources responsible for these hot spots, which in turn makes it difficult to reduce the uncertainty of health risk estimates for communities and to develop policies that mitigate these risks. We present a novel air pollution estimation method that models the highway traffic state, highway traffic‐induced air pollution emissions, and pollution dispersion, and describe a prototype implementation for the San Francisco Bay Area. Our model is based on the availability of real‐time traffic estimates on highways, which we obtain using a traffic dynamics model and an estimation algorithm that augments real‐time data from both fixed sensors and probe vehicles. These traffic estimates combined with local weather conditions are used as inputs to an emission model that estimates pollutant levels for multiple gases and particulates in real‐time. Finally, a dispersion model is used to assess the spread of these pollutants away from the highway source. Maps generated using the output of the dispersion model allow users to easily analyze the evolution of individual pollutants over time, and provides transportation engineers and public health officials with valuable information that can be used to minimize health risks.     

Inhalation exposure of traffic police officers to polycyclic aromatic hydrocarbons (PAHs) during the winter in Beijing, China

This study concerns the use of personal samplers to evaluate the exposure of traffic police to polycyclic aromatic hydrocarbons (PAHs) during the winter of 2005 in Beijing. We measured the samples collected for gas and particulate phases PAHs with the same technique used for an earlier study during the summer of 2004, and evaluated exposure risk based on the calculated benzo(a)pyrene equivalent concentrations (BaP(eq)) of both summer and winter. The mean exposure concentrations of gaseous and particulate phase PAHs in the winter are 4300+/-2900 ng/m(3) and 750+/-1000 ng/m(3), respectively, significantly higher than those measured simultaneously at control sites and also considerably higher than the values measured during the summer. The exposure PAH profiles for police and the control subjects are similar with predominant naphthalene in gaseous phase and dominant fluoranthene, pyrene, anthracene and naphthalene in particulate phase. Large daily variations occur both in summer and winter, because of the changes in the weather conditions especially wind speed and relative humidity which tend to disperse and scavenge PAHs in air. In the winter, the average BaP(eq) value for traffic police is 82.1 ng/m(3), which is significantly higher than those for the control subjects and the national standard of 10 ng/m(3) for ambient air. Particulate phase PAHs contribute more than 90% of the total exposure risk in the winter. Annually, weighted-average probabilities of exceeding the national standard (10 ng/m(3)) are 69.3% and 20.6% for the police and the controls, respectively.     

Application of land use regression to regulatory air quality data in Japan

A land use regression (LUR) model has been used successfully for predicting traffic-related pollutants, although its application has been limited to Europe and North America. Therefore, we modeled traffic-related pollutants by LUR then examined whether LUR models could be constructed using a regulatory monitoring network in Shizuoka, Japan. We used the annual-mean nitrogen dioxide (NO₂) and suspended particulate matter (SPM) concentrations between April 2000 and March 2006 in the study area. SPM accounts for particulate matter with an aerodynamic diameter less than 8 μm (PM₈). Geographic variables that are considered to predict traffic-related pollutants were classified into four groups: road type, traffic intensity, land use, and physical component. Using geographical variables, we then constructed a model to predict the monitored levels of NO₂ and SPM. The mean concentrations of NO₂ and SPM were 35.75 μg/m³ (standard deviation of 11.28) and 28.67 μg/m³ (standard deviation of 4.73), respectively. The final regression model for the NO₂ concentration included five independent variables. R² for the NO₂ model was 0.54. On the other hand, the regression model for the SPM concentration included only one independent variable. R² for the SPM model was quite low (R² = 0.11). The present study showed that even if we used regulatory monitoring air quality data, we could estimate NO₂ moderately well. This result could encourage the wide use of LUR models in Asian countries.     

Carcinogenic effects of some polycyclic aromatic hydrocarbons on the Japanese medaka and guppy in waterborne exposures

In this paper, we review studies on the carcinogenic effects of two polycyclic aromatic hydrocarbons (PAHs), benzo(a)pyrene (BaP) and 7,12-dimethylbenz(a)anthracene (DMBA), on the Japanese medaka (Oryzias latipes) and the guppy (Poecilia reticulata). Exposure media were prepared by adding PAHs to water, with and without dimethylformamide (DMF) as a carrier, and passing this solution through various sized filters. The low exposure medium was a 0.45 micron filtrate without DMF that contained less than 5 micrograms L-1 PAH. The intermediate medium was a DMF-mediated 0.45 micron filtrate which contained 30-50 micrograms L-1 of PAH. The high medium was a DMF-mediated glass-fibre filtrate which contained 150-250 micrograms L-1 of PAH. Young fish specimens (6-10 d old) were given a 6 h exposure once weekly for 2 to 4 wk. Both BaP and DMBA induced hepatic neoplasms in the two species, with the medaka being more sensitive than the guppy, and DMBA being a stronger carcinogen than BaP. Liver neoplasms almost exclusively developed after exposure to BaP and the neoplasms were limited to the high concentration exposure, whereas DMBA caused a substantial number of extrahepatic neoplasms as well as hepatic ones, especially in the medaka. Furthermore, all three concentrations of DMBA induced hepatic neoplasms in the medaka and all but the low concentration induced neoplasms in the guppy. These studies demonstrate the carcinogenic effects of two waterborne PAHs on two small fish species following brief exposures to very low concentrations, and support the contention that environmental PAHs can contribute to the occurrence of cancer in wild fishes.     

Long-term personal exposure to traffic-related air pollution among school children, a validation study

Several recent studies suggest an association between long-term exposure to traffic-related air pollution and health. Most studies use indicators of exposure such as outdoor air pollution or traffic density on the street of residence. Little information is available about the validity of these measurements as an estimate of long-term personal exposure to traffic-related air pollution. In this pilot study, we assessed outdoor and personal exposure to traffic-related air pollution in children living in homes on streets with different degree of traffic intensity. The personal exposure of 14 children aged 9-12 years to 'soot', NO(x) (NO and NO(2)) was assessed in Amsterdam between March and June 2003. Each child's personal exposure was monitored during four repeated 48-h periods. Concurrently, in- and outdoor NO(x) measurements were carried out at the school and at the home of each participating child. Measurements were supplemented by a questionnaire on time activity patterns and possible indoor sources. Flow-controlled battery operated pumps in a made-to-fit backpack were used to sample personal exposure to 'soot', determined from the reflectance of PM(2.5) filters. Exposure to NO(x) was assessed using Ogawa passive samplers. Children living near busy roads were found to have a 35% higher personal exposure to 'soot' than children living at an urban background location, despite that all children attended the same school that was located away from busy roads. Smaller contrasts in personal exposure were found for NO (14%), NO(2) (15%) and NO(x) (14%). This finding supports the use of 'living near a busy road' as a measure of exposure in epidemiological studies on the effects of traffic-related air pollution in children.     

Mutagenicity and polycyclic aromatic hydrocarbons analysis of ambient airborne particles collected in Athens, Greece

Samples of airborne particulates from the Athens atmosphere were examined for mutagenicity and various polycyclic aromatic hydrocarbons (PAH). Extracts induced linear, dose-related increases in TA98 His+ revertants in the Ames/Salmonella assay and contained average benzo[a]pyrene (BaP) levels of 3.9 ng/m3 of air. The levels of revertants/m3 of the samples showed a linear relation to their BaP and benzo[b]-(BbF) + benzo[k]-fluoranthene (BkF) concentrations and were higher in areas with dense traffic than in industrial areas. It is suggested that the atmosphere of Athens favours the formation of secondary direct-acting mutagens due to the oxidation and nitration of PAH by ozone and nitrogen oxides, which are more abundant in the late spring months.     

Polycyclic aromatic hydrocarbons inside and outside of apartments in an urban area

In the context of environmental monitoring in Berlin polycyclic aromatic hydrocarbon (PAH) concentrations in air and household dust were measured inside 123 residences (and simultaneously in a sub group in the air outside the windows). The aim of this study was to determine exposure to PAHs in the environment influencing by several factors, for instance, motor vehicle traffic in a populous urban area. Indoor air samplings were carried out in two periods (winter and spring/summer) in smokers and non-smokers apartments. Benzo(a)pyrene (BaP) median values were 0.65 ng m(-3) (winter) and 0.27 ng m(-3) (spring/summer) in smokers' apartments and 0.25 ng m(-3) (winter) and 0.09 ng m(-3) (spring/summer) in the apartments of non-smokers. The median BaP content in ambient air was 0.10 ng m(-3) (maximum: 1.1 ng/m(-3)) with an indoor-outdoor mean concentration ratio of 0.9 in non-smoker households and 5.4 in smoker apartments. In household dust we obtained median values of 0.3 mg kg(-1) (range: 0.1-1.4 mg kg(-1)). We found a significant relation between indoor and outdoor values. Approximately 75% of the variance of indoor air values was caused by the corresponding BaP concentrations in the air outside the apartment windows. Otherwise a significant correlation between indoor air and household dust values cannot be found. Therefore, according to our results, it is suggested that the indoor PAH concentration in non-smoker apartments could be attributed mainly to vehicular emissions.     

A regression-based method for mapping traffic-related air pollution: application and testing in four contrasting urban environments

Accurate, high-resolution maps of traffic-related air pollution are needed both as a basis for assessing exposures as part of epidemiological studies, and to inform urban air-quality policy and traffic management. This paper assesses the use of a GIS-based, regression mapping technique to model spatial patterns of traffic-related air pollution. The model--developed using data from 80 passive sampler sites in Huddersfield, as part of the SAVIAH (Small Area Variations in Air Quality and Health) project--uses data on traffic flows and land cover in the 300-m buffer zone around each site, and altitude of the site, as predictors of NO2 concentrations. It was tested here by application in four urban areas in the UK: Huddersfield (for the year following that used for initial model development), Sheffield, Northampton, and part of London. In each case, a GIS was built in ArcInfo, integrating relevant data on road traffic, urban land use and topography. Monitoring of NO2 was undertaken using replicate passive samplers (in London, data were obtained from surveys carried out as part of the London network). In Huddersfield, Sheffield and Northampton, the model was first calibrated by comparing modelled results with monitored NO2 concentrations at 10 randomly selected sites; the calibrated model was then validated against data from a further 10-28 sites. In London, where data for only 11 sites were available, validation was not undertaken. Results showed that the model performed well in all cases. After local calibration, the model gave estimates of mean annual NO2 concentrations within a factor of 1.5 of the actual mean (approx. 70-90%) of the time and within a factor of 2 between 70 and 100% of the time. r2 values between modelled and observed concentrations are in the range of 0.58-0.76. These results are comparable to those achieved by more sophisticated dispersion models. The model also has several advantages over dispersion modelling. It is able, for example, to provide high-resolution maps across a whole urban area without the need to interpolate between receptor points. It also offers substantially reduced costs and processing times compared to formal dispersion modelling. It is concluded that the model might thus be used as a means of mapping long-term air pollution concentrations either in support of local authority air-quality management strategies, or in epidemiological studies.     

Uncertainty and variability in risk from trophic transfer of contaminants in dredged sediments.

The risks associated with bioaccumulative contaminants must be considered when evaluating dredged material disposal alternatives. The bioaccumulation of organochlorines and other contaminants by higher trophic level organisms represents one of the most significant sources of uncertainty in risk assessment. Both population variability (e.g. true population heterogeneity in body weight, lipid content, etc.) and uncertainty (e.g. measurement error) in trophic transfer can lead to large errors in predicted risk values for ecological receptors. This paper describes and quantitatively evaluates sources of uncertainty and variability in estimating the risk to an ecological receptor (osprey) from the trophic transfer of polychlorinated biphenyls (PCBs) in sediments from the New York-New Jersey (NY-NJ) Harbor. The distribution of toxicity quotients is obtained using a food chain model for the osprey and specifying distributions for input parameters, which are disaggregated to represent either uncertainty or variability. PCB concentrations in sediment and water are treated as predominantly uncertain, whereas lipid content in fish, feeding preferences, and fish weight are assumed to contribute primarily to population variability in PCB accumulation. The analysis shows that point estimates of reasonable maximum exposure (RME) exceed the uncertainty bounds on the 95th percentile of variability. The analysis also shows that uncertainties in the sediment and water contaminant concentrations contribute more to the range of risk estimates than does the variability in the population exposure parameters. The separation of uncertainty and variability in food chain models can help to support management decisions regarding dredged material disposal by providing a quantitative expression of the confidence in ecological risk estimates. A rationale is provided for the distinction between uncertain and variable parameters based on management goals and data availability.     

Household air pollution and personal exposure risk of polycyclic aromatic hydrocarbons among rural residents in Shanxi,China

Polycyclic aromatic hydrocarbons (PAHs) are a group of pollutants of widespread concerns. Gaseous and size‐segregated particulate‐phase PAHs were collected in indoor and outdoor air in rural households. Personal exposure was measured and compared to the ingestion exposure. The average concentrations of 28 parent PAHs and benzo(a)pyrene (BaP) were 9000 ± 8390 and 131 ± 236 ng/m³ for kitchen, 2590 ± 2270 and 43 ± 95 ng/m³ for living room, and 2800 ± 3890 and 1.6 ± 0.7 ng/m³ for outdoor air, respectively. The mass percent of high molecular weight (HMW) compounds with 5–6 rings contributed 1.3% to total 28 parent PAHs. Relatively higher fractions of HMW PAHs were found in indoor air compared to outdoor air. Majorities of particle‐bound PAHs were found in the finest PM_0.25, and the highest levels of fine PM_0.25‐bound PAHs were in the kitchen using peat and wood as energy sources. The 24‐h personal PAH exposure concentration was 2100 ± 1300 ng/m³. Considering energies, exposures to those using wood were the highest. The PAH inhalation exposure comprised up to about 30% in total PAH exposure through food ingestion and inhalation, and the population attributable fraction (PAF) for lung cancer in the region was 0.85%. The risks for inhaled and ingested intakes of PAHs were 1.0 × 10^?5 and 1.1 × 10^?5, respectively.     

Characterisation and quantification of the sources of PM10 during air pollution episodes in the UK

Data for concentrations of PM(10) and gaseous pollutants from sites in the UK Automatic Urban and Rural Network have been examined during periods of elevated concentrations of PM(10). The ratios of concentrations of PM(10) to those of the other pollutants were used to determine the most probable source of the additional particles. The hypothesis is that because the concentrations of PM(10) were divided by those of the other pollutants, the ratio should decrease when PM(10) and the other pollutants have a common source. Conversely, the ratio should increase when the sources are different. During episodes where road traffic was the most probable source of the additional particles, the ratios of concentrations of PM(10) to carbon monoxide and oxides of nitrogen did decrease, but the comparable ratios for sulphur dioxide and ozone increased. In contrast, during episodes known to have been caused by construction activity, all these ratios increased. This is taken to show that the basic hypothesis is valid. For prolonged episodes, it was possible to use data averaged over the total duration of the episode for the purposes of source identification. For sporadic construction, or other short-duration episodes, it was necessary to use time series data. The data have also been used to calculate the differences between hourly average concentrations of pollutants measured during episodes and long-term hourly average concentrations. These have been used to model the additional PM(10) during air pollution episodes associated with construction activities and road traffic emissions. This confirms the lack of relationship between PM(10) and other pollutants during construction works. During episodes arising from road traffic emissions, there was good agreement between measured and modelled additional concentrations of PM(10) when an appropriate factor, F, related to the contribution of road traffic emissions to PM(10) at different site types was applied. The values used were 0.2 (Suburban), 0.3 (Urban Background/Urban Centre), and 0.5 (Roadside), representing 20%, 30%, and 50% contributions from road traffic, respectively.     

Filtration effectiveness of HVAC systems at near‐roadway schools

Concern for the exposure of children attending schools located near busy roadways to toxic, traffic‐related air pollutants has raised questions regarding the environmental benefits of advanced heating, ventilation, and air‐conditioning (HVAC) filtration systems for near‐road pollution. Levels of black carbon and gaseous pollutants were measured at three indoor classroom sites and at seven outdoor monitoring sites at Las Vegas schools. Initial HVAC filtration systems effected a 31–66% reduction in black carbon particle concentrations inside three schools compared with ambient air concentrations. After improved filtration systems were installed, black carbon particle concentrations were reduced by 74–97% inside three classrooms relative to ambient air concentrations. Average black carbon particle concentrations inside the schools with improved filtration systems were lower than typical ambient Las Vegas concentrations by 49–96%. Gaseous pollutants were higher indoors than outdoors. The higher indoor concentrations most likely originated at least partially from indoor sources, which were not targeted as part of this intervention.     

A numerical investigation of the impact of low boundary walls on pedestrian exposure to air pollutants in urban street canyons

A previous investigation into methods of exposure reduction for the pedestrian in the urban commuter environment highlighted the impact of a low boundary wall on the dispersion of air pollutants from adjacent traffic sources. The impact of low boundary walls on the dispersion of air pollutants in street canyons has been brought forward in this investigation to examine them, in more generic terms, with a view to highlighting exposure reduction strategies for pedestrians. 3D Computational Fluid Dynamics (CFD) models were used to examine this effect for varying wind speeds and directions in different street canyon geometries. The results of this investigation show that a low boundary wall located at the central median of the street canyon creates a significant reduction in pedestrian exposure on the footpath. Reductions of up to 40% were found for perpendicular wind directions and up to 75% for parallel wind directions, relative to the same canyon with no wall. The magnitude of the exposure reduction was also found to vary according to street canyon geometry and wind speed.     

Small-scale spatial variability of particle concentrations and traffic levels in Montreal: a pilot study

Little is known about the particulate exposure of populations living along major urban roads. The objective of this pilot study was to explore the small-scale spatial and temporal variability of the absorption coefficient of PM2.5 filters, as a surrogate for elemental carbon, in relation to levels of PM2.5, at residential sites with varying traffic densities in a large Canadian city. Concurrent 24-h measurements were performed at four residential sites during 7 weeks. A gradient existed across all four sites for the absorption coefficient of the filters (and NO2 levels). In contrast, the levels of PM2.5 were quite similar at all sites. The difference in the filter absorption coefficient of PM2.5 filters, between an urban background and a residential traffic site (with about 30000 vehicles/day), expressed as a percentage of the background site, was 40%. These results indicate that spatial variability in PM2.5 absorption coefficient can be observed with traffic intensity on a small scale within a North American city and suggests that regression modelling approaches similar to those used in European studies could be used to estimate exposure of the general population to traffic-related particles on a local scale in North America.     

Sputum induced cellularity in a group of traffic policemen

It has been demonstrated that a group of workers (e.g. waste handlers) daily exposed to a traffic related air pollution present airway inflammation in term of an increase of neutrophilic inflammation. The aim of our study was to determine the presence of airways inflammation detected by induced sputum in a population of traffic policemen (TP) in the city of Bari, compared to a group of healthy subjects (HS) without any occupational exposure to inhalation of traffic-related air pollution. Twelve non smokers, non atopics, healthy traffic policemen with a history of exposure to airway pollution and 12 HS underwent sputum induction. TP show a statistically significant increase in the percentage neutrophil cell count (median and IQ range) compared to the HS (65 and 13.5 vs. 40.5 and 9.5; p<0.01). In conclusion we have found that policemen chronically exposed to air pollution presented airway neutrophilic inflammation and the results of this pilot study could be strictly considered for the long term effect of a traffic pollution in airway inflammation and the lung function.     

Economic benefits of arsenic removal from ground water--a case study from West Bengal, India

Endocrine Disrupting Chemicals (EDCs) are of increasing concern because of their potential impacts on the environment, wildlife and human health. Pesticides and some pesticide metabolites are an important group of EDC, and exposure to them is a poorly quantified source of human and environmental exposure to such chemicals generally. Models for estimating human exposure to Endocrine Disrupting (ED) pesticides are an important risk management tool. Probabilistic models are now being used in addition to deterministic ones in all areas of risk assessment. These can provide more realistic exposure estimates, because they are better able to deal with variation and uncertainty more effectively and better inform risk management decisions. Deterministic models are still used and are of great value where exposure data are scarce. Models or groups of models that provide holistic human ED pesticide exposure estimates are required if the risk posed to humans by ED pesticides is to be better assessed. Much more research is needed to quantify different exposure routes such as exposure from agricultural spray drift and the medical use of pesticides to develop such models. Most available probabilistic models of human exposure were developed in the USA and require modification for use elsewhere. In particular, datasets equivalent to those used to create and apply the American models are required. This paper examines the known routes of human pesticide exposure with particular reference to ED pesticides and their quantification as unlike pesticides generally, many ED pesticides are harmful at very low doses, especially if exposure occurs during sensitive stages of development, producing effects that may not manifest for many years or that affect descendants via epigenetic changes. It also summarises available deterministic and probabilistic models commonly used to calculate human exposure. The main requirement if such models are to be used in the UK is more quantitative data on the sources and pathways of human ED pesticide exposure.     

Chemical and ecological effects of contaminated tunnel wash water runoff to a small Norwegian stream

Cleaning and washing of road tunnels are routinely performed and large volumes of contaminated wash water are often discharged into nearby recipients. In the present study, traffic related contaminants were quantified in tunnel wash water (the Nordby tunnel, Norway) discharged from a sedimentation pond to a nearby small stream, Årungselva. In situ size and charge fractionation techniques were applied to quantify traffic related metal species, while PAHs were quantified in total samples. All metals and several PAHs appeared at elevated concentrations in the discharged wash water compared with concentrations measured in Årungselva upstream the pond outlet, and to concentrations measured in the pond outlet before the tunnel wash event. In addition, several contaminants (e.g. Cu, Pb, Zn, fluoranthene, pyrene) exceeded their corresponding EQS. PAH and metals like Al, Cd, Cr, Cu, Fe and Pb were associated with particles and colloids, while As, Ca, K, Mg, Mo, Ni, Sb and Zn were more associated with low molecular mass species (< 10 kDa). Calculated enrichment factors revealed that many of the metals were derived from anthropogenic sources, originating most likely from wear of tires (Zn), brakes (Cu and Sb), and from road salt (Na and Cl). The enrichment factors for Al, Ba, Ca, Cr, Fe, K, Mg and Ni were low, suggesting a crustal origin, e.g. asphalt wear. Based on calculated PAH ratios, PAH seemed to originate from a mixture of sources such as wear from tires, asphalt and combustion. Finally, historical fish length measurement data indicates that the fish population in the receiving stream Årungselva may have been adversely influenced by the chemical perturbations in runoffs originating from the nearby roads and tunnels during the years, as the growth in summer old sea trout (Salmo trutta L.) in downstream sections of the stream is significantly reduced compared to the upstream sections.     

Exposure assessment of a cyclist to PM10 and ultrafine particles

Estimating personal exposure to air pollution is a crucial component in identifying high-risk populations and situations. It will enable policy makers to determine efficient control strategies. Cycling is again becoming a favorite mode of transport both in developing and in developed countries due to increasing traffic congestion and environmental concerns. In Europe, it is also seen as a healthy sports activity. However, due to high levels of hazardous pollutants in the present day road microenvironment the cyclist might be at a higher health risk due to higher breathing rate and proximity to the vehicular exhaust.In this paper we present estimates of the exposure of a cyclist to particles of various size fractions including ultrafine particles (UFP) in the town of Mol (Flanders, Belgium). The results indicate relatively higher UFP concentration exposure during morning office hours and moderate UFP levels during afternoon. The major sources of UFP and PM₁₀ were identified, which are vehicular emission and construction activities, respectively. We also present a dust mapping technique which can be a useful tool for town planners and local policy makers.     

A model for determination of motor vehicle emission factors from on-road measurements with a focus on submicrometer particles

The multiplicity of parameters that influence traffic-related emissions and that are often very difficult to measure or predict, makes the assessment of traffic emissions a very complicated process, strongly dependent on local conditions and usually associated with a high degree of error. The aim of this paper was to develop, calibrate and test a simple model for 'on-road' measurements of traffic emission factors as part of a major program focussed on the assessment of traffic contribution to fine and ultrafine emissions to the whole air shed and to local areas in south-east Queensland, Australia. A mathematical model developed was based on the mass balance concept for on-road assessment of traffic-related emission rates. The model requires fewer experimental data points as input and is more applicable to the common on-road testing situation, when no more than two monitors of a specific pollutant can be used. The model was tested and calibrated using experimental data on particle number concentration collected at a road-monitoring site using the scanning mobility particle sizer, and was applied to assess the emission factors of submicrometer particles emitted by traffic. The average emission factor obtained using the box model and the experimental data from road measurements was 1.75 x 10(14) particles km(-1) vehicle(-1), with a standard error of 67.6%. While the emission factor obtained was comparable with some results obtained from dynamometer studies and applied to the vehicle mix at the sampling site, they were significantly higher than the factors reported by other studies.