Contribution Of Indoor Sources Research Articles

Variability and health impact of air pollutants and bioaerosols in multi-functional indoor environments with mechanical ventilation system

The condition of indoor environments significantly impacts human daily life and health, where exposure to harmful substances affects the resilience of occupants. To understand the dynamics of indoor air quality and its implications for occupant health thus this study evaluated air pollutant concentration (TVOC, NO2, O3, CO, CO2, PM10, PM2.5, and PM1) and bioaerosol in mechanically ventilated offices, laboratories, corridors, a library and a mechanical workshop. Simultaneous measurements of all air pollutants were performed for 24 h, including non-working hours, while bioaerosol was sampled for fungal identification and quantified via the colony counting method. High concentrations of PM10, PM2.5, PM1, O3 and bioaerosol were found in the mechanical workshop, where these pollutants were strongly related to humidity (p < 0.05) and indoor source contributions. Other air pollutants such as TVOC had the highest concentrations in the office areas during working hours with an average concentration of 361 ± 14.8 μg m−3, while for CO, the highest concentration was observed in the laboratories for both working hours (442 ± 26.0 ppb) and 24 h average concentration (438 ± 22.1 ppb). Dominant species identified in bioaerosol were Aspergillus sp., Geotrichum sp., Fusarium sp., and Penicillium sp., where the exposure to bioaerosol was found to be of low risk to all workers as the hazard quotient (HQ) was <1 for all multi-functional indoor environments. The results from this study suggest that indoor air pollutants and bioaerosol concentrations have a variety of characteristics and source contributions, especially from human activities and indoor sources.

Effectiveness of eco-feedback in improving the indoor air quality in residential buildings: Mitigation of the exposure to airborne particles

Indoor air quality, a major concern for human health, is strongly influenced by occupants' behavior but people are not aware about how their everyday behavior affects their exposure to pollutants. In the present paper we tried to cope with the gap of knowledge between lack of awareness and the understanding of how occupants’ behaviors affect the environment. To this end we performed an evaluation of the IAQ awareness of 100 families through questionnaire surveys and an investigation of an “eco-feedback” strategy based on awareness-raising campaigns. In particular, information and experimental campaigns were conducted in 10 homes allowing the evaluation of its effectiveness in the short-term. Results showed that the occupants are not properly aware of the IAQ in their homes and of their exposure to airborne particles including the possible contribution of indoor sources. Anyway, the eco-feedback strategy adopted resulted successful both in terms of promoting behavioral changes of the occupants and reducing the concentration levels while airborne particle emitting sources (i.e. cooking) were in operation. Indeed, the exposure to airborne particles while cooking measured after the information campaign resulted lower than the baseline exposure with median relative reductions of 47% and 59% for PM10 and particle number concentration, respectively. The outcomes of the study could be of great interest for scientists involved in designing eco-feedback campaigns and indoor airborne particle monitoring since, for the first time, the potential effect of an eco-feedback strategy on indoor air quality was shown.

Quantifying indoor PM2.5 levels and its sources in schools: What role does location, chalk use, and socioeconomic equity play ?

This study examines children's exposure to PM2.5 in the classroom environment of spatially and administratively distributed schools. For this purpose, we monitored PM2.5 levels inside and outside 40 classrooms in public and private schools located in urban and rural settings, while exploring the magnitude of indoor sources and correlations between the indoor and outdoor environment. A high correlation between indoor and outdoor PM2.5 levels across most schools was evident (Spearman correlation = 0.82). The usage of chalkboards as well as the re-suspension of settled particles due to indoor activities, high occupancy, and infrequent classroom cleaning increased indoor exposure. Concentrations of indoor PM2.5 (20–180 μg/m3, and a mean of 62 μg/m3) showed differences between urban and rural as well as between private and public schools. Some rural schools exhibited greater exposure than urban schools, depending on their immediate surrounding environment and their internal PM2.5 sources. IAQ simulation results indicated that internal sources may be as high 15.9 mg/h. Schools using chalkboards tended to have higher net PM2.5 sources as compared to schools that had shifted to whiteboards. Among the chalk-based classrooms, the mean net indoor source emission rate for public schools (4.8 mg/h) was significantly higher (>2.5 folds) than that determined for their private counterparts (1.8 mg/h). The consideration of urban versus rural settings, socioeconomic differences, as well as the quantification of the contribution of indoor sources are of significance in the context of improved management of IAQ in schools and protecting school-aged children.

Per-Person and Whole-Building VOC Emission Factors in an Occupied School with Gas-Phase Air Cleaning.

Using real-time measurements of CO2 and volatile organic compounds (VOCs) in the air handler of an occupied middle school, we quantified source strengths for 249 VOCs and apportioned the source to the building, occupants and their activities, outdoor air, or recirculation air. For VOCs quantified in this study, there is a source to the outdoors of 8.6 ± 1.8 g/h in building exhaust air, of which 5.9 ± 1.7 g/h can be attributed to indoor sources (the building and occupants and their activities). The corresponding whole-building area emission factor from indoor sources is 1020 ± 300 μg/(m2 h), including reactive VOCs like isoprene and monoterpenes (33 ± 5.1 and 29 ± 5.7 μg/(m2 h), respectively). Per-person emission factors are calculated for compounds associated with occupants and their activities, e.g., monoterpenes are emitted at a rate of 280 ± 80 μg/(person h). The air handler included carbon scrubbing, reducing supply air concentrations of 125 compounds by 38 ± 19% (mean ± std. dev.) with a net removal of 2.4 ± 0.4 g/h of organic compounds from the building. This carbon scrubber reduces steady-state indoor concentrations of organics by 65 μg/m3 and the contribution of indoor sources of VOCs to the outdoor environment by ∼40%. These data inform the design and operation of buildings to reduce human exposure to VOCs inside buildings. These data indicate the potential for gas-phase air cleaning to improve both indoor air quality and reduce VOC emissions from buildings to the outdoor environment.

Invited Perspective: Moving from Characterizing to Addressing Racial/Ethnic Disparities in Air Pollution Exposure.

Invited Perspective: Moving from Characterizing to Addressing Racial/Ethnic Disparities in Air Pollution Exposure.

Assessment of children's exposure to carbonaceous matter and to PM major and trace elements

Particulate matter (PM) pollution is one of the major environmental concerns due to its harmful effects on human health. As children are particularly vulnerable to particle exposure, this study integrates the concentration of PM chemical compounds measured in the micro-environments (MEs) where children spend most of their time to assess the daily exposure and inhaled dose. PM samples were analysed for organic and elemental carbon and for major and trace elements. Results showed that the MEs that contribute most to the children's daily exposure (80%) and inhaled dose (65%) were homes and schools. Results indicated that the high contribution of particulate organic matter (POM) indoors indicate high contributions of indoor sources to the organic fraction of the particles. The highest concentrations of PM chemical compounds and the highest Indoor/Outdoor ratios were measured in schools, where the contribution of mineral elements stands out due to the resuspension of dust caused by the students and to the chalk used in blackboards. The contribution of the outdoor particles to inhaled dose (24%) was higher than to the exposure (12%), due to the highest inhalation rates associated with the activities performed outdoor. This study indicates the importance of indoor air quality for the children's exposure and health.

Characterizing outdoor infiltration and indoor contribution of PM2.5 with citizen-based low-cost monitoring data

Epidemiological research on the adverse health outcomes due to PM2.5 exposure frequently relies on measurements from regulatory air quality monitors to provide ambient exposure estimates, whereas personal PM2.5 exposure may deviate from ambient concentrations due to outdoor infiltration and contributions from indoor sources. Research in quantifying infiltration factors (Finf), the fraction of outdoor PM2.5 that infiltrates indoors, has been historically limited in space and time due to the high costs of monitor deployment and maintenance. Recently, the growth of openly accessible, citizen-based PM2.5 measurements provides an unprecedented opportunity to characterize Finf at large spatiotemporal scales. In this analysis, 91 consumer-grade PurpleAir indoor/outdoor monitor pairs were identified in California (41 residential houses and 50 public/commercial buildings) during a 20-month period with around 650000h of paired PM2.5 measurements. An empirical method was developed based on local polynomial regression to estimate site-specific Finf. The estimated site-specific Finf had a mean of 0.26 (25th, 75th percentiles: [0.15, 0.34]) with a mean bootstrap standard deviation of 0.04. The Finf estimates were toward the lower end of those reported previously. A threshold of ambient PM2.5 concentration, approximately 30μg/m3, below which indoor sources contributed substantially to personal exposures, was also identified. The quantified relationship between indoor source contributions and ambient PM2.5 concentrations could serve as a metric of exposure errors when using outdoor monitors as an exposure proxy (without considering indoor-generated PM2.5), which may be of interest to epidemiological research. The proposed method can be generalized to larger geographical areas to better quantify PM2.5 outdoor infiltration and personal exposure.

The contribution of cooking appliances and residential traffic proximity to aerosol personal exposure

PurposeIndoor and outdoor factors affect personal exposure to air pollutants. Type of cooking appliance (i.e. gas, electricity), and residential location related to traffic are such factors. This research aims to investigate the effect of cooking with gas and electric appliances, as an indoor source of aerosols, and residential traffic as outdoor sources, on personal exposures to particulate matter with an aerodynamic diameter lower than 2.5 μm (PM2.5), black carbon (BC), and ultrafine particles (UFP).MethodsForty subjects were sampled for four consecutive days measuring personal exposures to three aerosol pollutants, namely PM2.5, BC, and UFP, which were measured using personal sensors. Subjects were equally distributed into four categories according to the use of gas or electric stoves for cooking, and to residential traffic (i.e. houses located near or away from busy roads).Results/conclusionCooking was identified as an indoor activity affecting exposure to aerosols, with mean concentrations during cooking ranging 24.7–50.0 μg/m3 (PM2.5), 1.8–4.9 μg/m3 (BC), and 1.4 × 104–4.1 × 104 particles/cm3 (UFP). This study also suggest that traffic is a dominant source of exposure to BC, since people living near busy roads are exposed to higher BC concentrations than those living further away from traffic. In contrast, the contribution of indoor sources to personal exposure to PM2.5 and UFP seems to be greater than from outdoor traffic sources. This is probably related to a combination of the type of building construction and a varying range of activities conducted indoors. It is recommended to ensure a good ventilation during cooking to minimize exposure to cooking aerosols.

Particle number emission rates of aerosol sources in 40 German households and their contributions to ultrafine and fine particle exposure.

More representative data on source-specific particle number emission rates and associated exposure in European households are needed. In this study, indoor and outdoor particle number size distributions (10-800nm) were measured in 40 German households under real-use conditions in over 500days. Particle number emission rates were derived for around 800 reported indoor source events. The highest emission rate was caused by burning candles (5.3×1013 h-1 ). Data were analyzed by the single-parameter approach (SPA) and the indoor aerosol dynamics model approach (IAM). Due to the consideration of particle deposition, coagulation, and time-dependent ventilation rates, the emission rates of the IAM approach were about twice as high as those of the SPA. Correction factors are proposed to convert the emission rates obtained from the SPA approach into more realistic values. Overall, indoor sources contributed~56% of the daily-integrated particle number exposure in households under study. Burning candles and opening the window leads to seasonal differences in the contributions of indoor sources to residential exposure (70% and 40% in the cold and warm season, respectively). Application of the IAM approach allowed to attribute the contributions of outdoor particles to the penetration through building shell and entry through open windows (26% and 15%, respectively).

Development and Validation of a Controlled Pressure Method Test Protocol for Vapor Intrusion Pathway Assessment.

Controlled pressure method (CPM) testing is a building-specific diagnostic tool for vapor intrusion (VI) pathway assessment which offers advantages over traditional pathway assessment approaches. By manipulating the building pressure conditions, the CPM creates the worst-case VI impact and provides rapid insight into the type of vapor source(s). The primary barrier to general acceptance and use of this tool is the need for definitive guidance on test design parameters, such as the indoor-outdoor pressure difference (or exhaust fan flow rate), CPM test duration, exhaust fan location, and air sampling location(s) and conditions. This study focused on a systematic evaluation of each of these factors, which then led to the formulation of proposed CPM testing guidelines. The results suggest that CPM tests should be conducted with both negative and positive pressure indoor-outdoor differentials of about 10-15 Pa, and the tests should last for at least nine indoor air exchanges for negative pressure difference testing and four indoor air exchanges for positive pressure difference testing. Although exhaust fan intake sampling is sufficient to provide critical information to assess impacts during negative pressure testing, adding room-specific indoor air sampling to both negative and positive pressure difference testing can provide insight into vapor entry locations and indoor source contributions.

Source Apportionment and Influencing Factor Analysis of Residential Indoor PM2.5 in Beijing.

In order to identify the sources of indoor PM2.5 and to check which factors influence the concentration of indoor PM2.5 and chemical elements, indoor concentrations of PM2.5 and its related elements in residential houses in Beijing were explored. Indoor and outdoor PM2.5 samples that were monitored continuously for one week were collected. Indoor and outdoor concentrations of PM2.5 and 15 elements (Al, As, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Pb, Se, Tl, V, Zn) were calculated and compared. The median indoor concentration of PM2.5 was 57.64 μg/m3. For elements in indoor PM2.5, Cd and As may be sensitive to indoor smoking, Zn, Ca and Al may be related to indoor sources other than smoking, Pb, V and Se may mainly come from outdoor. Five factors were extracted for indoor PM2.5 by factor analysis, explained 76.8% of total variance, outdoor sources contributed more than indoor sources. Multiple linear regression analysis for indoor PM2.5, Cd and Pb was performed. Indoor PM2.5 was influenced by factors including outdoor PM2.5, smoking during sampling, outdoor temperature and time of air conditioner use. Indoor Cd was affected by factors including smoking during sampling, outdoor Cd and building age. Indoor Pb concentration was associated with factors including outdoor Pb and time of window open per day, building age and RH. In conclusion, indoor PM2.5 mainly comes from outdoor sources, and the contributions of indoor sources also cannot be ignored. Factors associated indoor and outdoor air exchange can influence the concentrations of indoor PM2.5 and its constituents.

Contributions of indoor and outdoor sources to airborne polycyclic aromatic hydrocarbons indoors

Exposure to airborne polycyclic aromatic hydrocarbons (PAHs) leads to adverse health outcomes of human beings. Both indoor and outdoor sources contribute to airborne PAHs concentration indoors. In this study, a theoretical model considering the kinetic partition process between gas- and particle-phases PAHs was developed to analyze contributions of indoor and outdoor sources to indoor airborne PAHs. Seasonal contributions of indoor and outdoor sources to indoor pyrene (Pyr) and benzo[a]pyrene (BaP) were estimated in a typical Beijing residence as a model application for the closed-window, open-window and normal ventilation scenarios. For Pyr, the seasonal contribution of the indoor source to indoor concentration is 50.6%, 69.0%, 70.6% and 51.2% in spring, summer, autumn and winter. For BaP, the seasonal contribution of the indoor source to indoor concentration is 27.7%, 39.7%, 34.8% and 17.1% from spring to winter. The modeled results are in good agreement with the implications derived from the previously measured I/O ratios in other studies. Sensitivity analysis was conducted for indoor and outdoor source strengths and air exchange rates. It turned out that the contribution of the indoor source to indoor Pyr and BaP substantially increases with the increase of the indoor source strength and decreases with the increases of the air exchange rate. The model can be simply utilized to quantitatively predict the contributions of indoor and outdoor sources, which has directive significance in making the appropriate controlling measures of indoor airborne PAHs.

Challenges in estimating health effects of indoor exposures to outdoor particles: Considerations for regional differences

Ambient air pollution is a leading environmental risk factor causing substantial losses of life and significant morbidity. Concentration-response (CR) functions used globally to estimate such effects are largely based on ambient epidemiology, using centrally monitored outdoor air quality as an exposure indicator and various indices of population health as an outcome. Similar common understanding is mostly missing regarding indoor exposures. Less studied are health impact modifying factors such as particle size, infiltration, time-activity and population differences. In this discussion paper we aim at looking at one of these, infiltration.The sensitivity of overall personal exposure to indoor exposures was quantified by a simple probabilistic time-activity model to calculate fractional exposures for indoor, outdoor and in traffic time-activity. To demonstrate the potential regional differences in epidemiological C-R relationships we re-analysed the ESCAPE results for natural-cause mortality, focusing on geographical grouping of the cohorts: pooled estimates were calculated for the Nordic, Central European and Southern European cohorts.When comparing the relative differences in the regional hazard ratio increments, the Central European value (7%) is 1.75 times higher than the Nordic one, and Southern European value (12%) 3 times higher, respectively. While towards the expected direction when aiming to explain these differences at least partly with differences in PM2.5 infiltration, the differences are not statistically significant and only the Central European and the all cohorts combined estimates reach borderline statistical significance. As the analysis of PM2.5 infiltration factors by similar regions yielded only 10–15% differences, it seems possible that that the available data could also accommodate other regional factors, such as those originating from regional differences in population and contribution of indoor sources of PM, time-activity, behaviour, or compositional differences in the particulate matter.

Assessment of the indoor air quality in copy centres at Aveiro, Portugal

This study presents continuous measurements of size-segregated particulate matter, total volatile organic compounds, ozone, formaldehyde, comfort parameters (temperature and relative humidity), CO and CO2 at two copy centres (A and B) in Aveiro, Portugal. PM10 samples collected with low-volume samplers were used to determine the carbonaceous content (organic and elemental carbon) by a thermo-optical technique. Mean PM10 levels of 55.8 ± 7.50 μg m−3 and 51.3 ± 9.35 μg m−3 were obtained in copy centres A and B, respectively. The 24-h indoor PM10 concentration at both copy centres exceeded the protection limit established by the Portuguese legislation. Around 60 % of the PM10 were composed of particles with sizes below 2.5 μm. On average, organic carbon accounted for 27.6 % (copy centre A) and 18.6 % (copy centre B) of the PM10 mass indoors, whereas a lower mass fraction of 11.5 % was found for both outdoor spaces. The much higher indoor levels of organic carbon suggest significant contribution by indoor sources. The ozone level increased in both copy centres when the photocopiers started to work. Mean ozone levels (0.055 ± 0.005 and 0.048 ± 0.006 ppm in copy centres A and B, respectively) during business hours may exceed the standard recommended for workplaces (0.05 ppm), representing a cause of possible adverse health effects on employees. The indoor-to-outdoor ozone concentration ratios were greater than 1 in both centres, indicating an important contribution of indoor sources. Formaldehyde levels remained always below the World Health Organisation guideline for indoor air (0.1 mg m−3). Total concentrations of volatile organic compounds were also relatively low, in general ranging from around 190 to 300 ppb. The indoor-to-outdoor concentration ratios were in the range between 0.70 and 0.76. Results showed that operation of laser printers can lead to high particulate matter and ozone concentration indoors. Pollutants associated with printing equipment have potential to cause adverse health effects if exposures are sufficiently high. Precautions should be taken to minimise the risks of exposed workers.

A Randomized Cross-over Air Filtration Intervention Trial for Reducing Cardiovascular Health Risks in Residents of Public Housing near a Highway.

Exposure to traffic-generated ultrafine particles (UFP; particles <100 nm) is likely a risk factor for cardiovascular disease. We conducted a trial of high-efficiency particulate arrestance (HEPA) filtration in public housing near a highway. Twenty residents in 19 apartments living <200 m from the highway participated in a randomized, double-blind crossover trial. A HEPA filter unit and a particle counter (measuring particle number concentration (PNC), a proxy for UFP) were installed in living rooms. Participants were exposed to filtered air for 21 days and unfiltered air for 21 days. Blood samples were collected and blood pressure measured at days 0, 21 and 42 after a 12-hour fasting period. Plasma was analyzed for high sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), tumor necrosis factor alpha-receptor II (TNF-RII) and fibrinogen. PNC reductions ranging from 21% to 68% were recorded in 15 of the apartments. We observed no significant differences in blood pressure or three of the four biomarkers (hsCRP, fibrinogen, and TNF-RII) measured in participants after 21-day exposure to HEPA-filtered air compared to measurements after 21-day exposure to sham-filtered air. In contrast, IL-6 concentrations were significantly higher following HEPA filtration (0.668 pg/mL; CI = 0.465–0.959) compared to sham filtration. Likewise, PNC adjusted for time activity were associated with increasing IL-6 in 14- and 21-day moving averages, and PNC was associated with decreasing blood pressure in Lags 0, 1 and 2, and in a 3-day moving average. These negative associations were unexpected and could be due to a combination of factors including exposure misclassification, unsuccessful randomization (i.e., IL-6 and use of anti-inflammatory medicines), or uncontrolled confounding. Studies with greater reduction in UFP levels and larger sample sizes are needed. There also needs to be more complete assessment of resident time activity and of outdoor vs. indoor source contributions to UFP exposure. HEPA filtration remains a promising, but not fully realized intervention.

Indoor air quality in Latino homes in Boulder, Colorado

Indoor concentrations of airborne pollutants can be several times higher than those found outdoors, often due to poor ventilation, overcrowding, and the contribution of indoor sources within a home. Americans spend most of their time indoors where exposure to poor indoor air quality (IAQ) can result in diminished respiratory and cardiovascular health. This study measured the indoor air quality in 30 homes of a low-income Latino community in Boulder, Colorado during the summer of 2012. Participants were administered a survey, which included questions on their health conditions and indoor air pollution sources like cigarette smoke, heating fuel, and building materials. Twenty-four hour samples of fine particulate matter (PM2.5) from the indoor air were collected in each home; ambient PM2.5 samples were collected each day as well. Concurrent air samples were collected onto 47 mm Teflo and Tissuquartz filter at each location. Teflo filters were analyzed gravimetrically to measure PM2.5 and their extracts were used to determine levels of proteins and endotoxins in the fine fraction. The Tissuquartz filters were analyzed for elemental and organic carbon content (EC/OC). Results indicated that the indoor air contained higher concentrations of PM2.5 than the ambient air, and that the levels of OC were much higher than EC in both indoor and outdoor samples. This community showed no smoking in their homes and kept furry pets indoors at very low rates; therefore, cooking is likely the primary source of indoor PM. For responders with significant exposure to PM, it appeared to be primarily from occupational environments or childhood exposure abroad. Our findings indicate that for immigrant communities such as this, it is important to consider not only their housing conditions but also the relevant prior exposures when conducting health assessments.

Source attribution of personal exposure to airborne polycyclic aromatic hydrocarbon mixture using concurrent personal, indoor, and outdoor measurements

ObjectivesRelative importance of multiple indoor and outdoor venues on personal exposure concentrations to pro-carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) remains poorly understood. This is particularly challenging because many c-PAHs share sources and occur as a complex mixture. Accurate and precise apportionment of personal exposure according to exposure venues could aid in the understanding of human health effects due to a given source. Here, we partitioned indoor and personal exposure concentrations to seven c-PAHs and pyrene according to the indoor- and outdoor-origins. MethodsA simultaneous, integrated monitoring of personal, indoor and outdoor concentrations of nine PAHs was conducted in 75 homes for a consecutive 48-hour period across a two-year period in Kraków, Poland. Due to few known indoor sources for chrysene, we used this PAH species as a tracer for infiltration of outdoor PAHs. Personal and indoor concentrations of seven c-PAHs and pyrene were apportioned to home indoor, non-home indoor and outdoor origins. ResultsUsing Chrysenein/Chryseneout as proxy for an infiltration factor, Finf, infiltrated PAHs of outdoor origin are overall higher in concentration than those emitted from the indoor origin. Average contribution by the outdoor sources on B[a]A, B[b]F, and B[k]F were 92%, 79%, and 78% across all seasons, respectively. In contrast, in homes where a household member smoked, average contributions by the outdoor sources on B[ghi]P, B[a]P, D[ah]A, and IP were lower (i.e., 67%, 65%, 67%, and 66%, respectively). Season-averaged contributions by the outdoor sources on personal exposure to B[a]A, B[b]F, and B[k]F were 92%, 74%, and 77%, respectively. On the other hand, season-averaged home indoor source contributions on personal exposure to B[a]A, B[b]F, and B[k]F were estimated at 6%, 15%, and 19%, respectively. Similar contributions by season-averaged home indoor sources on personal exposure were estimated at 28% for B[ghi]P, 31% for B[a]P, 25% for D[ah]A, and 28% for IP. ConclusionOf the seven c-PAHs, B[a]A, B[b]F, and B[k]F are enriched in indoor and personal exposure concentrations from the outdoor coal-combustion. B[ghi]P, B[a]P, D[a,h]A, and IP, PAHs with some of the highest carcinogenic and mutagenic potencies, are considerably enriched by cigarette smoke in addition to the outdoor sources.

Indoor aerosols: from personal exposure to risk assessment

Motivated by growing considerations of the scale, severity, and risks associated with human exposure to indoor particulate matter, this work reviewed existing literature to: (i) identify state-of-the-art experimental techniques used for personal exposure assessment; (ii) compare exposure levels reported for domestic/school settings in different countries (excluding exposure to environmental tobacco smoke and particulate matter from biomass cooking in developing countries); (iii) assess the contribution of outdoor background vs indoor sources to personal exposure; and (iv) examine scientific understanding of the risks posed by personal exposure to indoor aerosols. Limited studies assessing integrated daily residential exposure to just one particle size fraction, ultrafine particles, show that the contribution of indoor sources ranged from 19% to 76%. This indicates a strong dependence on resident activities, source events and site specificity, and highlights the importance of indoor sources for total personal exposure. Further, it was assessed that 10-30% of the total burden of disease from particulate matter exposure was due to indoor-generated particles, signifying that indoor environments are likely to be a dominant environmental factor affecting human health. However, due to challenges associated with conducting epidemiological assessments, the role of indoor-generated particles has not been fully acknowledged, and improved exposure/risk assessment methods are still needed, together with a serious focus on exposure control.

Indoor Particle Levels in Small- and Medium-Sized Commercial Buildings in California

This study monitored indoor and outdoor particle concentrations in 37 small and medium commercial buildings (SMCBs) in California with three buildings sampled on two occasions, resulting in 40 sampling days. Sampled buildings included offices, retail establishments, restaurants, dental offices, and hair salons, among others. Continuous measurements were made for both ultrafine and fine particulate matter as well as black carbon inside and outside of the building. Integrated PM(2.5), PM(2.5-10), and PM(10) samples were also collected inside and outside the building. The majority of the buildings had indoor/outdoor (I/O) particle concentration ratios less than 1.0, indicating that contributions from indoor sources are less than removal of outdoor particles. However, some of the buildings had I/O ratios greater than 1, indicating significant indoor particle sources. This was particularly true of restaurants, hair salons, and dental offices. The infiltration factor was estimated from a regression analysis of indoor and outdoor concentrations for each particle size fraction, finding lower values for ultrafine and coarse particles than for submicrometer particles, as expected. The I/O ratio of black carbon was used as a relative measure of the infiltration factor of particles among buildings, with a geometric mean of 0.62. The contribution of indoor sources to indoor particle levels was estimated for each building.

Characteristics of Residential Indoor Carbonaceous Aerosols: A Case Study in Guangzhou, Pearl River Delta Region

Nine residences located in Guangzhou were selected to characterise indoor fine particles (PM2.5), organic carbon (OC) and elemental carbon (EC) during summer time. These nine residences were classified into 5 types, urban without smoker, urban with smoker, newly remodelled urban, roadside and suburban. The average indoor PM2.5 concentration was 47.4 µg/m3, consisting of 12.5 µg/m3 of OC and 4.4 µg/m3 of EC. OC and EC accounted for 24.6 % and 9.9 %, respectively, of the indoor PM2.5 mass. Higher PM2.5, OC and EC concentrations were observed in the urban residences with smokers and the roadside residence, suggesting the importance of indoor sources and outdoor penetration. The highest PM2.5 and OC concentrations were observed in one of the urban residences with a smoker due to the contribution of indoor sources and the poor condition of ventilation in the kitchen. The highest EC was observed in the roadside residence, indicating the penetration of outdoor traffic emissions. Urban residences without smokers and recently remodelled residences had similar PM2.5, OC and EC concentrations. The suburban residence had the lowest PM2.5 and OC concentrations, while the EC concentration was lower than roadside residence but similar to other urban residences. Eight carbonaceous fractions by thermal/optical reflectance (TOR) method, namely OC1, OC2, OC3, OC4, OP, EC1, EC2 and EC3, were also studied. OC2, OC3 and EC1 were the most abundant fractions. EC1 was found to be the carbonaceous fraction which was mainly from outdoor vehicular emissions. OC2 and OC3 were likely to be contributed by smoking and cooking emissions in indoor microenvironments.