Passive Vaping from Sub-Ohm Electronic Cigarette Devices.

To investigate passive vaping due to sub-ohm electronic cigarettes (e-cigs), aerosol number size distribution measurements (6 nm-10 µm) were performed during volunteer-vaping sessions. E-liquids, with vegetable glycerin (VG) and propylene glycol (PG), with a VG/PG ratio of 50/50 (with nicotine) and 80/20 (without nicotine), were vaped with a double-coil, single aerosol exit hole at 25-80 W electric power, corresponding to 130-365 kW m-2 heat fluxes and with an octa-coil, four aerosol exit holes atomizers, at 50-150 W electric power, corresponding to 133-398 kW m-2 heat fluxes. At the lowest heat flux, lower particle number concentrations (NTot) were observed for the nicotine-liquid than for the nicotine-free liquid, also due to its higher content of PG, more volatile than VG. For the octa-coil atomizer, at 265 and 398 kW m-2, NTot decreased below the first-generation e-cig, whereas volume concentrations greatly increased, due to the formation of super micron droplets. Higher volume concentrations were observed for the 80/20 VG/PG liquid, because of VG vaporization and of its decomposition products, greater than for PG. For the double coil atomizer, increasing the electric power from 40 W (208 kW m-2) to 80 W (365 kW m-2) possibly led to a critical heat flow condition, causing a reduction of the number concentrations for the VG/PG 50/50 liquid, an increase for the 80/20 VG/PG liquid and a decrease of the volume concentrations for both of them. Coherently, the main mode was at about 0.1 µm on both metrics for both liquids. For the other tests, two main modes (1 and 2 µm) were observed in the volume size distributions, the latter becoming wider at 100 and 150 W (265 and 398 kW m-2), suggesting the increased emission of light condensable decomposition products. The lower aerosol emissions observed at 150 W than at 100 W suggest the formation of gas-phase decomposition products. The observation of low-count high-volume aerosols addresses the relevance of the volume metric upon measuring the second-hand concentration of the aerosols released by sub-ohm e-cigarettes.

Size resolved aerosol respiratory doses in a Mediterranean urban area: From PM10 to ultrafine particles.

In the framework of the 2017 "carbonaceous aerosol in Rome and Environs" (CARE) experiment, particle number size distributions have been continuously measured on February 2017 in downtown Rome. These data have been used to estimate, through MPPD model, size and time resolved particle mass, surface area and number doses deposited into the respiratory system. Dosimetry estimates are presented for PM10, PM2.5, PM1 and Ultrafine Particles (UFPs), in relation to the aerosol sources peculiar to the Mediterranean basin and to the atmospheric conditions. Particular emphasis is focused on UFPs and their fraction deposited on the olfactory bulb, in view of their possible translocation to the brain. The site of PM10 deposition within the respiratory system considerably changes, depending on the aerosol sources and then on its different size distributions. On making associations between health endpoints and aerosol mass concentrations, the relevant coarse and fine fractions would be more properly adopted, because they have different sources, different capability of penetrating deep into the respiratory system and different toxicological implications. The separation between them should be set at 1 µm, rather than at 2.5 µm, because the fine fraction is considerably less affected by the contribution of the natural sources. Mass dose is a suitable metric to describe coarse aerosol events but gives a poor representation of combustion aerosol. This fraction of particles, made of UFPs and of accumulation mode particles (mainly with size below 0.2 µm), is of high health relevance. It elicited the highest oxidative activity in the CARE experiment and is properly described by the particle surface area and by the number metrics. Such metrics are even more relevant for the UFP doses deposited on the olfactory bulb, in consideration of the role recognized to oxidative stress in the progression of neurodegenerative diseases. Such metrics would be more appropriate, rather than PMx mass concentrations, to correlate neurodegenerative pathologies with aerosol pollution.

Impact of Electronic Alternatives to Tobacco Cigarettes on Indoor Air Particular Matter Levels.

An aerosol study was carried out in a test room measuring particulate matter (PM) with an aerodynamic diameter smaller than 10, 4, 2.5 and 1 µm (PM10, PM4, PM2.5, PM1) before and during the use of electronic alternatives to tobacco cigarettes (EATC) IQOS®, GLO®, JUUL®, with different kinds of sticks/pods, as well as during the smoking of a conventional tobacco cigarette. The aerosol was mainly in the PM1 size range (>95%). All studied EATCs caused lower indoor PM1 concentrations than conventional tobacco cigarettes. Nevertheless, they determined a worsening of indoor-PM1 concentration that ranged from very mild for JUUL®-depending on the pod used-to considerably severe for IQOS® and GLO®. Median values ranged from 11.00 (Iqos3 and Juul2) to 337.5 µg m-3 (Iqos4). The high variability of particle loadings was attributed both to the type of stick/pod used and to the different way of smoking of volunteers who smoked/vaped during the experiments. Moreover, during vaping IQOS® and GLO® indoor PM1 concentrations reach levels by far higher than outdoor concentrations that range from 14 to 21 µg m-3, especially during the exhalation of the smoke. From these results emerge an urgent need of a legislative regulation limiting the use of such devices in public places.

Air quality assessment in different environmental scenarios by the determination of typical heavy metals and Persistent Organic Pollutants in native lichen Xanthoria parietina.

The study was aimed to evaluate the ability of native lichen Xanthoria (X.) parietina to biomonitor and bioaccumulate some heavy metals (As, Cd, Co, Cr, Ni, Pb), PAHs, PCDDs, PCDFs, PCBs and PBDEs and to evaluate the use of the native X. parietina as a multi-tracer tool for scenarios characterized by different anthropogenic pressures. Samples of native X. parietina were collected in six different sites (two green, two residential and two industrial areas, respectively) and analyzed for the target compounds. The results show that X. parietina was a useful tool for the biomonitoring of air quality in the selected areas, and was able to bioaccumulate all the studied metals and POPs. In particular, the total concentrations dry weight (dw) ranged between 8.1 and 103.4 mg kg-1 for metals, from 113 × 103 to 183 × 103 ng kg-1 for PAHs, from 868 to 7685 ng kg-1 for PCBs, from 14.3 to 113.8 ng kg-1 for PCDDs/Fs (∑TEq = 0.9-7.1), and from 194 to 554 ng kg-1 for PBDEs. Besides, in general, the levels of analytes recovered in the different samples of lichen show an increasing trend from green to industrial sites, especially for PCBs (mean values equal to 1218, 4253 and 7192 ng kg-1 respectively for green, residential and industrial areas). The statistical approach, based on Pearson's correlation and principal component analysis tests, showed that one of the industrial sites was well-separated from the others, that resulted grouped due to some similarities.

Ultrafine particles and PM2.5 in the air of cities around the world: Are they representative of each other?

Can mitigating only particle mass, as the existing air quality measures do, ultimately lead to reduction in ultrafine particles (UFP)? The aim of this study was to provide a broader urban perspective on the relationship between UFP, measured in terms of particle number concentration (PNC) and PM2.5 (mass concentration of particles with aerodynamic diameter < 2.5 µm) and factors that influence their concentrations. Hourly average PNC and PM2.5 were acquired from 10 cities located in North America, Europe, Asia, and Australia over a 12-month period. A pairwise comparison of the mean difference and the Kolmogorov-Smirnov test with the application of bootstrapping were performed for each city. Diurnal and seasonal trends were obtained using a generalized additive model (GAM). The particle number to mass concentration ratios and the Pearson's correlation coefficient were calculated to elucidate the nature of the relationship between these two metrics. Results show that the annual mean concentrations ranged from 8.0 × 103 to 19.5 × 103 particles·cm-3 and from 7.0 to 65.8 µg·m-3 for PNC and PM2.5, respectively, with the data distributions generally skewed to the right, and with a wider spread for PNC. PNC showed a more distinct diurnal trend compared with PM2.5, attributed to the high contributions of UFP from vehicular emissions to PNC. The variation in both PNC and PM2.5 due to seasonality is linked to the cities' geographical location and features. Clustering the cities based on annual median concentrations of both PNC and PM2.5 demonstrated that a high PNC level does not lead to a high PM2.5, and vice versa. The particle number-to-mass ratio (in units of 109 particles·µg-1) ranged from 0.14 to 2.2, >1 for roadside sites and <1 for urban background sites with lower values for more polluted cities. The Pearson's r ranged from 0.09 to 0.64 for the log-transformed data, indicating generally poor linear correlation between PNC and PM2.5. Therefore, PNC and PM2.5 measurements are not representative of each other; and regulating PM2.5 does little to reduce PNC. This highlights the need to establish regulatory approaches and control measures to address the impacts of elevated UFP concentrations, especially in urban areas, considering their potential health risks.

Where Do Ultrafine Particles and Nano-Sized Particles Come From?

This paper presents an overview of the literature studies on the sources of ultrafine particles (UFPs), nanomaterials (NMs), and nanoparticles (NPs) occurring in indoor (occupational and residential) and outdoor environments. Information on the relevant emission factors, particle concentrations, size, and compositions is provided, and health relevance of UFPs and NPs is discussed. Particular attention is focused on the fraction of particles that upon inhalation deposit on the olfactory bulb, because these particles can possibly translocate to brain and their possible role in neurodegenerative diseases is an important issue emerging in the recent literature.

Evaluation of the Submicron Particles Distribution Between Mountain and Urban Site: Contribution of the Transportation for Defining Environmental and Human Health Issues.

Transportation is one of the main causes of atmospheric pollution, especially in downtown big cities. Researchers usually point their attention to gaseous and/or particulate matter pollutants. This paper investigated the role of submicron particles, particularly the fraction ranging between 5-560 nm, in aerosol chemistry for identifying the contribution of autovehicular traffic and investigating the doses deposited in the human respiratory tract. Measurements carried out by two Fast Mobility Particle Sizer (FMPS, TSI) analyzers were simultaneously performed at two different sampling sites (an urban and a mountain site) during workdays and weekends in July. The total particle number (2-2.5 times higher in the urban site), the aerosol size distribution (different modes during the day), and the ultrafine/non-ultrafine particle ratios (ranging between 2-4 times between two sites) were investigated and discussed in relationship to the high autovehicular traffic in Rome and the almost null anthropogenic emissions at the mountain site, as well as the differing contributions of both to the "fresh nucleation" and to "aged aerosol". Furthermore, the regional cumulative number doses deposited in the human respiratory tract were studied for both sites: The difference between the urban/mountain site was very high (up to 15 fold), confirming the pollutant role of transportation.

Evidences of copper nanoparticle exposure in indoor environments: Long-term assessment, high-resolution field emission scanning electron microscopy evaluation, in silico respiratory dosimetry study and possible health implications.

A variety of appliances operated by brush electric motors, widely used in indoor environments, emit nanoparticles (NPs). Due to electric arc discharge during the operation of such motors, some NPs contain copper (Cu). Their dimensions are the same of those found in brain tissue samples by other authors who speculated their possible translocation to brain through olfactory bulb. Cu has been reported to play an important role in the etiopathogenesis of Alzheimer's disease. Thus, the present study was performed to 1. estimate by means of Multiple-Path Particle Dosimetry model the doses of NPs released by electric appliances that can potentially deposit on the olfactory bulb; 2. investigate the morphology and the composition of particles emitted by some electric appliances daily used in indoor environments; 3. monitor for a long time period the Cu contamination of indoor environments due to this kind of appliances. About 106-107 NPs deposit on the olfactory bulb during the operation (1.5-6 min) of such appliances, with a major contribution due to 10-20 nm NPs. HR-FESEM characterization confirmed the presence of such NPs, that were observed both as individual particles (20-40 nm) and aggregated to form particles in the µm sizes range. XEDS microanalysis revealed the presence of Cu together with other elements. Relevant daily contamination of indoor environments due to these appliances has been confirmed by monitoring throughout a year the Cu content of PM10 samples collected both indoor and outdoor private dwellings. Cu was present in great part as an insoluble form. This means that, following protracted exposure, Cu NPs of such origin may undergo tissue accumulation. This is cause of concern because general population is chronically exposed to such Cu nanoparticles in indoor environments and in view of the role assigned to Cu in the development of neurological disorders.

Environmental Electronic Vape Exposure from Four Different Generations of Electronic Cigarettes: Airborne Particulate Matter Levels.

Electronic cigarettes (e-cigs) were introduced into the market in 2006 and their technological features have evolved substantially over time. Currently, there are four different generations of e-cigs that are broadly considered less harmful than the use of combusted tobacco products although passive exposure to aerosols often occurs in public spaces and indoor environments. The study aim was to evaluate the levels of airborne particulate matter (PM) emitted during the use of all the four generations of e-cigs, testing different use modalities. PM10, PM4, PM2.5 and PM1 were measured through a Dusttrak ™ II Aerosol Monitor, for a total of 20 independent experiments. All tested e-cigs devices produced PM during their use, and PM10 was almost made of PM1 size fraction. In addition, we observed a progressive increase in PM emission from the first to the fourth generation, and an upward trend of PM1 emitted by the fourth generation e-cig with an increase in the operating power. The results showed that, whatever the model adopted, passive vaping does occur. This finding supports the need for legislative interventions to regulate the e-cigs use in public places and other enclosed environments, in order to protect the health of any subject who is potentially exposed.

Second-hand aerosol from tobacco and electronic cigarettes: Evaluation of the smoker emission rates and doses and lung cancer risk of passive smokers and vapers.

Smoking activities still represent the main, and preventable, cause of lung cancer risk worldwide. For this reason, a number of studies were carried out to deepen and better characterize the emission of cigarette-generated mainstream aerosols in order to perform an a-priori evaluation of the particle doses and related lung cancer risks received by active smokers. On the contrary, a gap of knowledge still exists in evaluating the dose and risk received by passive smokers in indoor private micro-environments (e.g. homes). For this purpose, in the present paper, an experimental campaign was performed to evaluate the exposure to second-hand aerosol from conventional and electronic cigarettes and to estimate the consequent dose received by passive smokers/vapers and the related lung cancer risk. Measurements of exposure levels in terms of particle number, PM10 and black carbon concentrations, as well as particle size distributions, were performed in a naturally ventilated indoor environment during smoking activities of tobacco and electronic cigarettes. The particle emission rates of smokers and vapers, for the different aerosol metrics under investigation, were evaluated. Moreover, for a typical exposure scenario, the dose received by the passive smokers/vapers in a naturally ventilated indoor micro-environment was estimated through a Multiple-Path Particle Dosimetry (MPPD) model able to assess the particle dose received in the different tracts of the respiratory systems. Furthermore, on the basis of scientific literature data about mass fraction of carcinogenic compounds contained in cigarette-emitted particles (i.e. Heavy Metals, Benzo-a-pyrene and nitrosamines) and the estimated doses, the excess life cancer risk (ELCR) for passive smokers/vapers was evaluated. Cumulative respiratory doses for passive smokers were up to 15-fold higher than for passive vapers. The ELCR for second-hand smokers was five orders of magnitude larger than for second-hand vapers.

Is it the time to study air pollution effects under environmental conditions? A case study to support the shift of in vitro toxicology from the bench to the field.

Air pollution and particulate matter are recognised cause of increased disease incidence in exposed population. The toxicological processes underlying air pollution associated effects have been investigated by in vivo and/or in vitro experimentation. The latter is usually performed by exposing cells cultured under submerged condition to particulate matter concentration quite far from environmental exposure expected in humans. Here we report for the first time the feasibility of a direct exposure of air liquid interface cultured cells to environmental concentration of particulate matter. Inflammatory proteins release was analysed in cell medium while differential expression of selected genes was analysed in cells. Significant association of anti-oxidant genes was observed with secondary and aged aerosol, while cytochrome activation with primary and PAHs enriched ultrafine particles. The results obtained clearly show the opportunity to move from the lab bench to the field for properly understanding the toxicological effects also of ultrafine particles on selected in vitro models.

Reference Intervals for Urinary Cotinine Levels and the Influence of Sampling Time and Other Predictors on Its Excretion Among Italian Schoolchildren.

(1) Background: Environmental Tobacco Smoke (ETS) exposure remains a public health problem worldwide. The aims are to establish urinary (u-) cotinine reference values for healthy Italian children, to evaluate the role of the sampling time and of other factors on children's u-cotinine excretion. (2) Methods: A cross-sectional study was performed on 330 children. Information on participants was gathered by a questionnaire and u-cotinine was determined in two samples for each child, collected during the evening and the next morning. (3) Results: Reference intervals (as the 2.5th and 97.5th percentiles of the distribution) in evening and morning samples were respectively equal to 0.98⁻4.29 and 0.91⁻4.50 µg L-1 (ETS unexposed) and 1.39⁻16.34 and 1.49⁻20.95 µg L-1 (ETS exposed). No statistical differences were recovered between median values found in evening and morning samples, both in ETS unexposed and exposed. Significant predictors of u-cotinine excretions were ponderal status according to body mass index of children (ß = 0.202; p-value = 0.041 for evening samples; ß = 0.169; p-value = 0.039 for morning samples) and paternal educational level (ß = -0.258; p-value = 0.010; for evening samples; ß = -0.013; p-value = 0.003 for morning samples). (4) Conclusions: The results evidenced the need of further studies for assessing the role of confounding factors on ETS exposure, and the necessity of educational interventions on smokers for rising their awareness about ETS.

Second-hand smoke generated by combustion and electronic smoking devices used in real scenarios: Ultrafine particle pollution and age-related dose assessment.

Aerosol measurements were carried out in a model room where both combustion (conventional and hand-rolled cigarettes, a cigar and tobacco pipe) and non-combustion (e-cigarette and IQOS®) devices were smoked. The data were used to estimate the dose of particles deposited in the respiratory systems of individuals from 3months to 21years of age using the multiple-path particle dosimetry (MPPD) model. Regardless of the smoking device, the highest doses were received by infants, which reached 9.88×108particles/kg bw during a cigar smoking session. Moreover, 60% to 80% of the particles deposited in the head region of a 3-month-old infant were smaller than 100nm and could be translocated to the brain via the olfactory bulb. The doses due to second-hand smoke from electronic devices were significantly lower, below 1.60×108particles/kg bw, than those due to combustion devices. Dosimetry estimates were 50% to 110% higher for IQOS® than for e-cigarettes.

Temporal evolution of ultrafine particles and of alveolar deposited surface area from main indoor combustion and non-combustion sources in a model room.

Aerosol number size distributions, PM mass concentrations, alveolar deposited surface areas (ADSAs) and VOC concentrations were measured in a model room when aerosol was emitted by sources frequently encountered in indoor environments. Both combustion and non-combustion sources were considered. The most intense aerosol emission occurred when combustion sources were active (as high as 4.1×107particlescm-3 for two meat grilling sessions; the first with exhaust ventilation, the second without). An intense spike generation of nucleation particles occurred when appliances equipped with brush electric motors were operating (as high as 106particlescm-3 on switching on an electric drill). Average UFP increments over the background value were highest for electric appliances (5-12%) and lowest for combustion sources (as low as -24% for tobacco cigarette smoke). In contrast, average increments in ADSA were highest for combustion sources (as high as 3.2×103µm2cm-3 for meat grilling without exhaust ventilation) and lowest for electric appliances (20-90µm2cm-3). The health relevance of such particles is associated to their ability to penetrate cellular structures and elicit inflammatory effects mediated through oxidative stress in a way dependent on their surface area. The highest VOC concentrations were measured (PID probe) for cigarette smoke (8ppm) and spray air freshener (10ppm). The highest PM mass concentration (PM1) was measured for citronella candle burning (as high as 7.6mgm-3).

Electronic cigarettes: age-specific generation-resolved pulmonary doses.

Particle size-number distributions of aerosol from e-cigarettes (0 and 14 mg mL-1 nicotine) were compared with conventional cigarettes. Results were used to provide age-specific (9-21 years) dosimetry estimates applying the MMPD model. After a 2-s puff, total number doses (D Tot ) were highest for 9 years of age (6.01 × 1010-1.31 × 1011 particles) and lowest for 18 years of age (4.69 × 1010-1.06 × 1011 particles). Such doses represented about 19-45 and 25-100% of the relevant daily doses of not smoking individuals, respectively, in tracheobronchial (TB) and alveolar (A) regions. D Tot for the e-cigarettes were about double that for conventional cigarette. Deposition densities and daily volume of e-cigarette liquid deposited per unit surface area were maximum at lobar bronchi, highest for 9 years and lowest for 21 years age.

Pedestrians in Traffic Environments: Ultrafine Particle Respiratory Doses.

Particulate matter has recently received more attention than other pollutants. PM10 and PM2.5 have been primarily monitored, whereas scientists are focusing their studies on finer granulometric sizes due both to their high number concentration and their high penetration efficiency into the respiratory system. The purpose of this study is to investigate the population exposure to UltraFine Particles (UFP, submicrons in general) in outdoor environments. The particle number doses deposited into the respiratory system have been compared between healthy individuals and persons affected by Chronic Obstructive Pulmonary Disease (COPD). Measurements were performed by means of Dust Track and Nanoscan analyzers. Forty minute walking trails through areas with different traffic densities in downtown Rome have been considered. Furthermore, particle respiratory doses have been estimated for persons waiting at a bus stop, near a traffic light, or along a high-traffic road, as currently occurs in a big city. Large differences have been observed between workdays and weekdays: on workdays, UFP number concentrations are much higher due to the strong contribution of vehicular exhausts. COPD-affected individuals receive greater doses than healthy individuals due to their higher respiratory rate.

Traffic aerosol lobar doses deposited in the human respiratory system.

Aerosol pollution in urban environments has been recognized to be responsible for important pathologies of the cardiovascular and respiratory systems. In this perspective, great attention has been addressed to Ultra Fine Particles (UFPs < 100 nm), because they efficiently penetrate into the respiratory system and are capable of translocating from the airways into the blood circulation. This paper describes the aerosol regional doses deposited in the human respiratory system in a high-traffic urban area. The aerosol measurements were carried out on a curbside in downtown Rome, on a street characterized by a high density of autovehicular traffic. Aerosol number-size distributions were measured by means of a Fast Mobility Particle Sizer in the range from 5.6 to 560 nm with a 1 s time resolution. Dosimetry estimates were performed with the Multiple-Path Particle Dosimetry model by means of the stochastic lung model. The exposure scenario close to traffic is represented by a sequence of short-term peak exposures: about 6.6 × 1010 particles are deposited hourly into the respiratory system. After 1 h of exposure in proximity of traffic, 1.29 × 1010, 1.88 × 1010, and 3.45 × 1010 particles are deposited in the head, tracheobronchial, and alveolar regions. More than 95 % of such doses are represented by UFPs. Finally, according to the greater dose estimated, the right lung lobes are expected to be more susceptible to respiratory pathologies than the left lobes.

Dynamic of submicrometer particles in urban environment.

Many studies show that particle toxicity increases with decreasing their size, emphasizing the role of submicrometric particles, in particular of ultrafine particles (<100 nm). In fact, particles greater than 2.5 µm are quickly removed through dry and wet deposition on the timescale of hours whereas submicrometer particles may reside in atmosphere for weeks, penetrate in indoor environment, and be long-range transported. High aerosol size resolution measurements are important for a correct assessment of the deposition efficiency in the human respiratory system, and time resolution is another important requisite. Starting from such considerations, time-resolved aerosol particle number size distributions have been measured in downtown Rome. Fast Mobility Particle Sizer (FMPS) and Scanning Mobility Particle Sizer (SMPS) measurements have been carried out at the INAIL's Pilot Station, located in downtown Rome, in an area characterized by high density of autovehicular traffic. The two instruments have allowed to investigate deeply the urban aerosol in the range of 5.6-560 and 3.5-117 nm, respectively. In particular, the FMPS measurements have confirmed the interpretation about the transition phenomena in the time interval of few seconds, timescale typically associated with the emission of gasoline and diesel engines. In downtown Rome, the hourly average size distribution is bimodal or trimodal with maxima at about 5-15, 20-30, and 70-100 nm. Particle formation in the nucleation mode was associated to freshly emitted autovehicular exhaust.

Sensitive multiresidue method by HS-SPME/GC-MS for 10 volatile organic compounds in urine matrix: a new tool for biomonitoring studies on children.

A HS-SPME method coupled with GC-MS analysis has been developed for simultaneously measuring the concentration of 10 volatile organic compounds (VOCs) (benzene, toluene, ethylbenzene, o-, m-, and p-xylene, methyl tert-butyl ether, ethyl tert-butyl ether, 2-methyl-2-butyl methyl ether, and diisopropyl ether) in urine matrix as a biomonitoring tool for populations at low levels of exposure to such VOCs. These compounds, potentially toxic for human health, are common contaminants of both outdoor and indoor air, as they are released by autovehicular traffic; some of them are also present in environmental tobacco smoke (ETS). Thus, the exposure to these pollutants cannot be neglected and should be assessed. The low limits of detection and quantification (LODs and LOQs <6.5 and 7.5 ng L(-1), respectively) and the high reproducibility (CVs <4 %) make the developed method suited for biomonitoring populations exposed at low levels such as children. Further, the method is cost-effective and low in time-consumption; therefore, it is useful for investigating large populations. It has been applied to children exposed to traffic pollution and/or ETS; the relevant results are reported, and the relevant implications are discussed.