Occurrence and Risk Assessment of Personal PM2.5-Bound Phthalates Exposure for Adults in Hong Kong.

We performed personal PM2.5 monitoring involving 56 adult residents in Hong Kong. Additionally, paired personal and residential indoor fine particle (PM2.5) samples were collected from 26 homes and from 3 fixed monitoring locations (i.e., outdoor samples). Six PM2.5-bound phthalate esters (PAEs)-including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBP), di(2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DnOP)-were measured using a thermal desorption-gas chromatography/mass spectrometer method. Average ∑6PAEs (i.e., summation of six PAE congeners) concentrations in personal PM2.5 exposure (699.4 ng/m3) were comparable with those in residential indoors (646.9 ng/m3), and both were slightly lower than the outdoor levels. DEHP was the most abundant PAE congener (80.3%-85.0%) and found at the highest levels in different exposure categories, followed by BBP, DnBP, and DnOP. Strong correlations were observed between DEHP with DnBP (rs: 0.81-0.90; p < 0.01), BBP (rs: 0.81-0.90; p < 0.01), and DnOP (rs: 0.87-0.93; p < 0.01) in each exposure category. However, no apparent intercorrelations were shown for PAE congeners. Higher indoor concentrations and a stronger correlation between DMP and DEP were found compared with outdoor concentrations. Principal component analysis affirmed heterogeneous distribution and notable variations in PAE sources across different exposure categories. The average daily intakes of ∑6PAEs and DEHP via inhalation were 0.14-0.17 and 0.12-0.16 µg/kg-day for adults in Hong Kong. A time-weighted model was used to estimate PAE exposures incorporating residential indoor and outdoor exposure and time activities. The inhalation cancer risks attributable to measured and estimated personal exposure to DEHP exceeded the U.S. EPA's benchmark (1 × 10-6). The results provide critical information for mitigation strategies, suggesting that PAEs from both ambient and indoor sources should be considered when exploring the inhalation health risks of PAEs exposure.

Validity of using ambient concentrations as surrogate exposures at the individual level for fine particle and black carbon: A systematic review and meta-analysis.

Exposure measurement error is an important source of bias in epidemiological studies. We assessed the validity of employing ambient (outdoor) measurements as proxies of personal exposures at individual levels focusing on fine particles (PM2.5) and black carbon (BC)/elemental carbon (EC) on a global scale. We conducted a systematic review and meta-analysis and searched databases (ISI Web of Science, Scopus, PubMed, Ovid MEDLINE®, Ovid Embase, and Ovid BIOSIS) to retrieve observational studies in English language published from 1 January 2006 until 5 May 2021. Correlation coefficients (r) between paired ambient (outdoor) concentration and personal exposure for PM2.5 or BC/EC were standardized as effect size. We used random-effects meta-analyses to pool the correlation coefficients and investigated the causes of heterogeneity and publication bias. Furthermore, we employed subgroup and meta-regression analyses to evaluate the modification of pooled estimates by potential mediators. This systematic review identified thirty-two observational studies involving 1744 subjects from ten countries, with 28 studies for PM2.5 and 11 studies for BC/EC. Personal PM2.5 exposure is more strongly correlated with ambient (outdoor) concentrations (0.63, 95% confidence interval [CI]: 0.57-0.68) than personal BC/EC exposure (0.49, 95% CI: 0.38-0.59), with significant differences in r (0.14, 95% CI: 0.03-0.25; p < 0.05). The results demonstrated that the health status of participants was a significant modifier of pooled correlations. In addition, the personal to ambient (P/A) ratio for PM2.5 and average ambient BC/EC levels were potential effect moderators of the pooled r. The funnel plots and Egger's regression test indicated inevident publication bias. The pooled estimates were robust through sensitivity analyses. The results support the growing consensus that the validity coefficient of proxy measures should be addressed when interpreting results from epidemiological studies to better understand how strong health outcomes are affected by different levels of PM2.5 and their components.

Efficacy of air filtration and education interventions on fine particulate matter among rural Native American homes heated with wood stoves: Results from the EldersAIR randomized trial.

BACKGROUND: Native Americans living in rural areas often rely upon wood stoves for home heating that can lead to elevated indoor concentrations of fine particulate matter (PM2.5). Wood stove use is associated with adverse health outcomes, which can be a particular risk in vulnerable populations including older adults. OBJECTIVES: We assessed the impact of portable air filtration units and educational approaches that incorporated elements of traditional knowledge on indoor and personal PM2.5 concentrations among rural, Native American elder households with wood stoves. METHODS: EldersAIR was a three-arm, pre-post randomized trial among rural households from the Navajo Nation and Nez Perce Tribe in the United States. We measured personal and indoor PM2.5 concentrations over 2-day sampling periods on up to four occasions across two consecutive winter seasons in elder participant homes. We assessed education and air filtration intervention efficacy using linear mixed models. RESULTS: Geometric mean indoor PM2.5 concentrations were 50.5 % lower (95 % confidence interval: -66.1, -27.8) in the air filtration arm versus placebo, with similar results for personal PM2.5. Indoor PM2.5 concentrations among education arm households were similar to placebo, although personal PM2.5 concentrations were 33.3 % lower for the education arm versus placebo (95 % confidence interval: -63.2, 21.1). SIGNIFICANCE: The strong partnership between academic and community partners helped facilitate a culturally acceptable approach to a clinical trial intervention within the study communities. Portable air filtration units can reduce indoor PM2.5 that originates from indoor wood stoves, and this finding was supported in this study. The educational intervention component was meaningful to the communities, but did not substantially impact indoor PM2.5 relative to placebo. However, there is evidence that the educational interventions reduced indoor PM2.5 in some subsets of the study households. More study is required to determine ways to optimize educational interventions within Native American communities.

Efficacy of Air Filtration and Education Interventions on Indoor Fine Particulate Matter and Child Lower Respiratory Tract Infections among Rural U.S. Homes Heated with Wood Stoves: Results from the KidsAIR Randomized Trial.

BACKGROUND: Millions of rural U.S. households are heated with wood stoves. Wood stove use can lead to high indoor concentrations of fine particulate matter [airborne particles ≤2.5µm in aerodynamic diameter (PM2.5)] and is associated with lower respiratory tract infection (LRTI) in children. OBJECTIVES: We assessed the impact of low-cost educational and air filtration interventions on childhood LRTI and indoor PM2.5 in rural U.S. homes with wood stoves. METHODS: The Kids Air Quality Interventions for Reducing Respiratory Infections (KidsAIR) study was a parallel three-arm (education, portable air filtration unit, control), post-only randomized trial in households from Alaska, Montana, and Navajo Nation (Arizona and New Mexico) with a wood stove and one or more children <5 years of age. We tracked LRTI cases for two consecutive winter seasons and measured indoor PM2.5 over a 6-d period during the first winter. We assessed results using two analytical frameworks: a) intervention efficacy on LRTI and PM2.5 (intent-to-treat), and b) association between PM2.5 and LRTI (exposure-response). RESULTS: There were 61 LRTI cases from 14,636 child-weeks of follow-up among 461 children. In the intent-to-treat analysis, children in the education arm [odds ratio (OR)=0.98; 95% confidence interval (CI): 0.35, 2.72] and the filtration arm (OR=1.23; 95% CI: 0.46, 3.32) had similar odds of LRTI vs. control. Geometric mean PM2.5 concentrations were similar to control in the education arm (11.77% higher; 95% CI: -16.57, 49.72) and air filtration arm (6.96% lower; 95% CI: -30.50, 24.55). In the exposure-response analysis, odds of LRTI were 1.45 times higher (95% CI: 1.02, 2.05) per interquartile range (25 µg/m3) increase in mean indoor PM2.5. DISCUSSION: We did not observe meaningful differences in LRTI or indoor PM2.5 in the air filtration or education arms compared with the control arm. Results from the exposure-response analysis provide further evidence that biomass air pollution adversely impacts childhood LRTI. Our results highlight the need for novel, effective intervention strategies in households heated with wood stoves. https://doi.org/10.1289/EHP9932.

Characteristics and health risks of personal exposure to particle-bound PAHs for Hong Kong adult residents: From ambient pollution to indoor exposure.

Research on individual level polycyclic aromatic hydrocarbons (PAHs) exposure is scarce. Moreover, the independent contribution of ambient- and indoor-origin PAHs to personal exposure remains poorly studied. We performed simultaneous ambient, residential indoor, and personal exposure measurements in a panel of healthy adults to investigate particle-bound PAHs, focusing on their carcinogenic congeners (cPAHs). Average PAH concentrations were much higher in ambient and residential indoor than personal exposure, with distinct seasonal variations. We employed chrysene as a tracer to investigate residential indoor and personal PAHs exposure by origin. Personal cPAH exposure was largely attributable to ambient-origin exposures (95.8%), whereas a considerable proportion of residential indoor PAHs was likely attributable to indoor emissions (33.8%). Benzo[a]pyrene equivalent (BaPeq) concentrations of cPAH accounted for 95.2%-95.6% of total carcinogenic potential. Uncertainties in estimated PAHs (and BaPeq) exposure and cancer risks for adults were calculated using the Monte Carlo simulation. Cancer risks attributable to ambient, residential indoor, and personal cPAH inhalation exposures ranged from 4.0 × 10-6 to 1.0 × 10-5 . A time-activity weighted model was employed for personal PAH exposure estimations. Estimated cPAH exposures demonstrate high cancer risks for adults in Hong Kong, suggesting that exposure to indoor-generated PAHs should be of great concern to the general population.

Indoor fine particulate matter and demographic, household, and wood stove characteristics among rural US homes heated with wood fuel.

Household heating using wood stoves is common practice in many rural areas of the United States (US) and can lead to elevated concentrations of indoor fine particulate matter (PM2.5 ). We collected 6-day measures of indoor PM2.5 during the winter and evaluated household and stove-use characteristics in homes at three rural and diverse study sites. The median indoor PM2.5 concentration across all homes was 19 µg/m3 , with higher concentrations in Alaska (median = 30, minimum = 4, maximum = 200, n = 10) and Navajo Nation homes (median = 29, minimum = 3, maximum = 105, n = 23) compared with Montana homes (median = 16, minimum = 2, maximum = 139, n = 59). Households that had not cleaned the chimney within the past year had 65% higher geometric mean PM2.5 compared to those with chimney cleaned within 6 months (95% confidence interval [CI]: -1, 170). Based on a novel wood stove grading method, homes with low-quality and medium-quality stoves had substantially higher PM2.5 compared to homes with higher-quality stoves (186% higher [95% CI: 32, 519] and 161% higher; [95% CI:27, 434], respectively). Our findings highlight the need for, and complex nature of, regionally appropriate interventions to reduce indoor air pollution in rural wood-burning regions. Higher-quality stoves and behavioral practices such as regular chimney cleaning may help improve indoor air quality in such homes.

Toxicological effects of personal exposure to fine particles in adult residents of Hong Kong.

Toxicological studies have demonstrated the associations between fine particle (PM2.5) components and various cytotoxic endpoints. However, few studies have investigated the toxicological effects of source-specific PM2.5 at the individual level. To investigate the potential impact of source-specific PM2.5 on cytotoxic effects, we performed repeated personal PM2.5 monitoring of 48 adult participants in Hong Kong during the winter and summer of 2014-2015. Quartz filters were analyzed for carbonaceous aerosols and water-soluble ions in PM2.5. Teflon filters were collected to determine personal PM2.5 mass and metal concentrations. The toxicological effects of personal PM2.5 exposure-including cytotoxicity, inflammatory response, and reactive oxygen species (ROS) production-were measured using A549 cells in vitro. Personal PM2.5 samples collected in winter were more effective than those collected in summer at inducing cytotoxicity and the expression of proinflammation cytokine IL-6. By contrast, summer personal PM2.5 samples induced high ROS production. We performed a series of statistical analyses, Spearman correlation and a source apportionment approach with a multiple linear regression (MLR) model, to explore the sources contributing most significantly to personal PM2.5 bioreactivity. Secondary inorganic species and transition metals were discovered to be weak-to-moderately associated with cytotoxicity (rs: 0.26-0.55; p < 0.01) and inflammatory response (rs: 0.26-0.44; p < 0.05), respectively. Carbonaceous aerosols (i.e., organic and elemental carbon; rs: 0.23-0.27; p < 0.05) and crustal material (Mg and Ca) was positively associated with ROS generation. The PMF-MLR models revealed that tailpipe exhaust and secondary sulfate contributed to ROS generation, whereas secondary nitrate was the major contributor to PM2.5 cytotoxicity and inflammation. These results improve and variate the arguments for practical policies designed to mitigate the risks posed by air pollution sources and to protect public health.

Characteristics and toxicological effects of commuter exposure to black carbon and metal components of fine particles (PM2.5) in Hong Kong.

Epidemiological studies have demonstrated significant associations between traffic-related air pollution and adverse health outcomes. Personal exposure to fine particles (PM2.5) in transport microenvironments and their toxicological properties remain to be investigated. Commuter exposures were investigated in public transport systems (including the buses and Mass Transit Railway (MTR)) along two sampling routes in Hong Kong. Real-time sampling for PM2.5 and black carbon (BC), along with integrated PM2.5 sampling, were performed during the warm and cold season of 2016-2017, respectively. Commuter exposure to BC during 3-hour commuting time exhibited a wider range, from 3.4 to 4.6 µg/m3 on the bus and 5.5 to 8.7 µg/m3 in MTR cabin (p < .05). PM2.5 mass and major chemical constituents (including organic carbon (OC), elemental carbon (EC), and metals) were analyzed. Cytotoxicity, including cellular reactive oxygen species (ROS) production, was determined in addition to acellular ROS generation. PM2.5 treatment promoted the ROS generation in a concentration-dependent manner. Consistent diurnal variations were observed for commuter exposure to BC and PM2.5 components, along with cellular and acellular ROS generation, which marked with two peaks during the morning (08:00-11:00) and evening rush hours (17:30-20:30). Commuter exposures in the MTR system were characterized by higher levels of PM2.5 and elemental components (e.g., Ca, Cr, Fe, Zn, Ba) compared to riding the bus, along with higher cellular and acellular ROS production (p < .01). These metals were attributed to different sources: rail tracks, wheels, brakes, and crustal origin. Weak to moderate associations were shown for the analyzed transition metals with PM2.5-induced cell viability and cellular ROS. Multiple linear regression analysis revealed that Ni, Zn, Mn, Fe, Ti, and Co attributed to cytotoxicity and ROS generation. These findings underscore the importance of commuter exposures and their toxic effects, urging effective mitigating strategies to protect human health.

Indoor, outdoor, and personal exposure to PM2.5 and their bioreactivity among healthy residents of Hong Kong.

Direct evidence about associations between fine particles (PM2.5) components and the corresponding PM2.5 bioreactivity at the individual level is limited. We conducted a panel study with repeated personal measurements involving 56 healthy residents in Hong Kong. Fractional exhaled nitric oxide (FeNO) levels were measured from these subjects. Out of 56 subjects, 27 (48.2%) participated in concurrent outdoor, indoor, and personal PM2.5 monitoring. Organic carbon (OC), elemental carbon (EC), particle bound-polycyclic aromatic hydrocarbons (PAHs), and phthalates were analyzed. Alteration in cell viability, lactic dehydrogenase (LDH), interleukin-6 (IL-6), and 8-isoprostane by 50 µg/mL PM2.5 extracts was determined in A549 cells in vitro. Moderate heterogeneities were shown in PM2.5 exposures and the corresponding PM2.5 bioreactivity across different sample types. Associations between the analyzed components and PM2.5 bioreactivity were assessed using the multiple regression models. Toxicological results revealed that indoor and personal exposure to OC as well as PAH compounds and their derivatives (e.g., Alkyl-PAHs, Oxy-PAHs) induced cell viability reduction and increase in levels of LDH, IL-6, and 8-isoprostane. Overall, OC in personal exposure played a dominant role in PM2.5-induced bioreactivity. Subsequently, we examined the associations of FeNO with IL-6 and 8-isoprostane levels using mixed-effects models. The results showed that per interquartile change in IL-6 and 8-isoprostane were associated with a 6.4% (p < 0.01) and 11.1% (p < 0.01) increase in FeNO levels, respectively. Our study explored the toxicological properties of chemical components in PM2.5 exposure, which suggested that residential indoors and personal OC and PAHs should be of great concern for human health. These findings indicated that further studies in inflammation and oxidative stress-related illnesses due to particle exposure would benefit from the assessment of in vitro PM2.5 bioreactivity.

Wood stove interventions and child respiratory infections in rural communities: KidsAir rationale and methods.

BACKGROUND: Acute lower respiratory tract infections (LRTIs) account for >27% of all hospitalizations among US children under five years of age. Residential burning of biomass for heat leads to elevated indoor levels of fine particulate matter (PM2.5) that often exceed current health based air quality standards. This is concerning as PM2.5 exposure is associated with many adverse health outcomes, including a greater than three-fold increased risk of LRTIs. Evidence-based efforts are warranted in rural and American Indian/Alaska Native (AI/AN) communities in the US that suffer from elevated rates of childhood LRTI and commonly use wood for residential heating. DESIGN: In three rural and underserved settings, we conducted a three-arm randomized controlled, post-only intervention trial in wood stove homes with children less than five years old. Education and household training on best-burn practices were introduced as one intervention arm (Tx1). This intervention was evaluated against an indoor air filtration unit arm (Tx2), as well as a control arm (Tx3). The primary outcome was LRTI incidence among children under five years of age. DISCUSSION: To date, exposure reduction strategies in wood stove homes have been either inconsistently effective or include factors that limit widespread dissemination and continued compliance in rural and economically disadvantaged populations. As part of the "KidsAIR" study described herein, the overall hypothesis was that a low-cost, educational intervention targeting indoor wood smoke PM2.5 exposures would be a sustainable approach for reducing children's risk of LRTI in rural and AI/AN communities.

Estimation of personal exposure to fine particles (PM2.5) of ambient origin for healthy adults in Hong Kong.

Personal exposure and ambient fine particles (PM2.5) measurements for 13 adult subjects (ages 19-57) were conducted in Hong Kong between April 2014 and June 2015. Six to 21 personal samples (mean = 19) per subject were obtained throughout the study period. Samples were analyzed for mass by gravimetric analysis, and 19 elements (from Na to Pb) were analyzed using X-Ray Fluorescence. Higher subject-specific correlations between personal and ambient sulfur (rs = 0.92; p < 0.001) were found as compared to PM2.5 mass (rs = 0.79; p < 0.001) and other elements (0.06 < rs < 0.86). Personal vs. ambient sulfur regression yielded an average exposure factor (Fpex) of 0.73 ±â€¯0.02, supporting the use of sulfur as a surrogate to estimate personal exposure to PM2.5 of ambient origin (Ea). Ea accounted for 41-82% and 57-73% of total personal PM2.5 exposures (P) by season and by subject, respectively. The importance of both Ea and non-ambient exposures (Ena, 11.2 ±â€¯5.6 µg/m3; 32.5 ±â€¯10.9%) are noted. Mixed-effects models were applied to estimate the relationships between ambient PM2.5 concentrations and their corresponding exposure variables (Ea, P). Higher correlations for Ea (0.90; p < 0.001) than for P (0.58; p < 0.01) were found. A calibration coefficient < 1 suggests an attenuation of 22% (ranging 16-28%) of the true effect estimates when using average ambient concentrations at central monitoring stations as surrogates for Ea. Stationary ambient data can be used to assess population exposure only if PM exposure is dominated by Ea.

Determinants of personal exposure to fine particulate matter (PM2.5) in adult subjects in Hong Kong.

Personal monitoring for fine particulate matter (PM2.5) was conducted for adults (48 subjects, 18-63years of age) in Hong Kong during the summer and winter of 2014-2015. All filters were analyzed for PM2.5 mass and constituents (including carbonaceous aerosols, water-soluble ions, and elements). We found that season (p=0.02) and occupation (p<0.001) were significant factors affecting the strength of the personal-ambient PM2.5 associations. We applied mixed-effects models to investigate the determinants of personal exposure to PM2.5 mass and constituents, along with within- and between-individual variance components. Ambient PM2.5 was the dominant predictor of (R2=0.12-0.59, p<0.01) and the largest contributor (>37.3%) to personal exposures for PM2.5 mass and most components. For all subjects, a one-unit (2.72µg/m3) increase in ambient PM2.5 was associated with a 0.75µg/m3 (95% CI: 0.59-0.94µg/m3) increase in personal PM2.5 exposure. The adjusted mixed-effects models included information extracted from individual's activity diaries as covariates. The results showed that season, occupation, time indoors at home, in transit, and cleaning were significant determinants for PM2.5 components in personal exposure (R2ß=0.06-0.63, p<0.05), contributing to 3.0-70.4% of the variability. For one-hour extra time spent at home, in transit, and cleaning an average increase of 1.7-3.6% (ammonium, sulfate, nitrate, sulfur), 2.7-12.3% (elemental carbon, ammonium, titanium, iron), and 8.7-19.4% (ammonium, magnesium ions, vanadium) in components of personal PM2.5 were observed, respectively. In this research, the within-individual variance component dominated the total variability for all investigated exposure data except PM2.5 and EC. Results from this study indicate that performing long-term personal monitoring is needed for examining the associations of mass and constituents of personal PM2.5 with health outcomes in epidemiological studies by describing the impacts of individual-specific data on personal exposures.

Randomized Trial of Interventions to Improve Childhood Asthma in Homes with Wood-burning Stoves.

BACKGROUND: Household air pollution due to biomass combustion for residential heating adversely affects vulnerable populations. Randomized controlled trials to improve indoor air quality in homes of children with asthma are limited, and no such studies have been conducted in homes using wood for heating. OBJECTIVES: Our aims were to test the hypothesis that household-level interventions, specifically improved-technology wood-burning appliances or air-filtration devices, would improve health measures, in particular Pediatric Asthma Quality of Life Questionnaire (PAQLQ) scores, relative to placebo, among children living with asthma in homes with wood-burning stoves. METHODS: A three-arm placebo-controlled randomized trial was conducted in homes with wood-burning stoves among children with asthma. Multiple preintervention and postintervention data included PAQLQ (primary outcome), peak expiratory flow (PEF) monitoring, diurnal peak flow variability (dPFV, an indicator of airway hyperreactivity) and indoor particulate matter (PM) PM2.5. RESULTS: Relative to placebo, neither the air filter nor the woodstove intervention showed improvement in quality-of-life measures. Among the secondary outcomes, dPFV showed a 4.1 percentage point decrease in variability [95% confidence interval (CI)=-7.8 to -0.4] for air-filtration use in comparison with placebo. The air-filter intervention showed a 67% (95% CI: 50% to 77%) reduction in indoor PM2.5, but no change was observed with the improved-technology woodstove intervention. CONCLUSIONS: Among children with asthma and chronic exposure to woodsmoke, an air-filter intervention that improved indoor air quality did not affect quality-of-life measures. Intent-to-treat analysis did show an improvement in the secondary measure of dPFV. TRIAL REGISTRATION: ClincialTrials.gov NCT00807183. https://doi.org/10.1289/EHP849.

Chemical characterization and sources of personal exposure to fine particulate matter (PM2.5) in the megacity of Guangzhou, China.

Concurrent ambient and personal measurements of fine particulate matter (PM2.5) were conducted in eight districts of Guangzhou during the winter of 2011. Personal-to-ambient (P-C) relationships of PM2.5 chemical components were determined and sources of personal PM2.5 exposures were evaluated using principal component analysis and a mixed-effects model. Water-soluble inorganic ions (e.g., SO42-, NO3-, NH4+, C2O42-) and anhydrosugars (e.g., levoglucosan, mannosan) exhibited median personal-to-ambient (P/C) ratios < 1 accompanied by strong P-C correlations, indicating that these constituents in personal PM2.5 were significantly affected by ambient sources. Conversely, elemental carbon (EC) and calcium (Ca2+) showed median P/C ratios greater than unity, illustrating significant impact of local traffic, indoor sources, and/or personal activities on individual's exposure. SO42- displayed very low coefficient of divergence (COD) values coupled with strong P-C correlations, implying a uniform distribution of SO42- in the urban area of Guangzhou. EC, Ca2+, and levoglucosan were otherwise heterogeneously distributed across individuals in different districts. Regional air pollution (50.4 ± 0.9%), traffic-related particles (8.6 ± 0.7%), dust-related particles (5.8 ± 0.7%), and biomass burning emissions (2.0 ± 0.2%) were moderate to high positive sources of personal PM2.5 exposure in Guangzhou. The observed positive and significant contribution of Ca2+ to personal PM2.5 exposure, highlighting indoor sources and/or personal activities, were driving factors determining personal exposure to dust-related particles. Considerable discrepancies (COD values ranging from 0.42 to 0.50) were shown between ambient concentrations and personal exposures, indicating caution should be taken when using ambient concentrations as proxies for personal exposures in epidemiological studies.

Reducing indoor air pollutants with air filtration units in wood stove homes.

BACKGROUND: Biomass burning has been shown to be a major source of poor indoor air quality (IAQ) in developing and higher income countries across the world. Specifically, wood burning for cooking and heating contributes to high indoor concentrations of fine (particles with aerodynamic diameters<2.5µm; PM2.5) and coarse (particles with aerodynamic diameters <10µm and >2.5µm; PMc) particulate matter. Endotoxin, predominantly found within the coarse fraction of airborne particulate matter, is associated with proinflammatory effects and adverse outcomes among susceptible populations. The aim of this study was to assess the efficacy of air filter interventions in reducing indoor PM2.5, PMc, and PMc-associated endotoxin concentrations in homes using a wood stove for primary heating. RESULTS: Homes (n=48) were randomized to receive in-room air filtration units with either a high efficiency filter (i.e. active) or a lower efficiency fiberglass filter (i.e., placebo). The active filter intervention showed a 66% reduction in indoor PM2.5 concentrations (95% CI: 42.2% to 79.7% reduction) relative to the placebo intervention. Both the active and the placebo filters were effective in substantially reducing indoor concentrations of PMc (63.3% and 40.6% average reduction for active and placebo filters, respectively) and PMc-associated endotoxin concentrations (91.8% and 80.4% average reductions, respectively). CONCLUSIONS: These findings support the use of high efficiency air filtration units for reducing indoor PM2.5 in homes using a wood stove for primary heating. We also discovered that using lower efficiency, lower cost filter alternatives can be effective for reducing PMc and airborne endotoxin in homes burning biomass fuel.

Efficacy of interventions targeting household air pollution from residential wood stoves.

Wood is commonly used for residential heating, but there are limited evidence-based interventions for reducing wood smoke exposures in the indoor environment. The Asthma Randomized Trial of Indoor Wood Smoke (ARTIS) study was designed to assess the efficacy of residential interventions to reduce indoor PM exposure from wood stoves. As part of a three-arm randomized placebo-controlled trial, two household-level interventions were evaluated: wood stove changeouts and air filtration units. Exposure outcomes included indoor measures such as continuous PM2.5, particle counts, and carbon monoxide. Median indoor PM2.5 concentration was 17.5 µg/m3 in wood-burning homes prior to interventions. No significant reductions in PM2.5 concentrations were observed in the 40 homes receiving the placebo filter intervention. Sixteen homes received the wood stove changeout and showed no significant changes in PM2.5 or particle counts. PM2.5 concentrations were reduced by 68% in the filter intervention homes. Relative to placebo, air filtration unit homes had an overall PM2.5 reduction of 63% (95% CI: 47-75%). Relative to the wood stove changeout, the filtration unit intervention was more efficacious and less expensive, yet compliance issues indicated a need for the evaluation of additional strategies for improving indoor air quality in homes using wood stoves.

Characterization of ambient-generated exposure to fine particles using sulfate as a tracer in the Chinese megacity of Guangzhou.

Total personal exposures can differ from the concentrations measured at stationary ambient monitoring sites. To provide further insight into factors affecting exposure to particles, chemical tracers were used to separate total personal exposure into its ambient and non-ambient components. Simultaneous measurements of ambient and personal exposure to fine particles (PM2.5) were conducted in eight districts of Guangzhou, a megacity in South China, during the winter of 2011. Considerable significant correlations (Spearman's Rho, rs) between personal exposures and ambient concentrations of sulfate (SO42-; rs>0.68) were found in contrast to elemental carbon (EC; rs>0.37). The average fraction of personal SO42- to ambient SO42- resulting in an adjusted ambient exposure factor of α=0.72 and a slope of 0.73 was determined from linear regression analysis when there were minimal indoor sources of SO42-. From all data pooled across the districts, the estimated average ambient-generated and non-ambient-generated exposure to PM2.5 were 55.3µg/m3 (SD=23.4µg/m3) and 18.1µg/m3 (SD=29.1µg/m3), respectively. A significant association was found between ambient-generated exposure and ambient PM2.5 concentrations (Pearson's r=0.51, p<0.001). As expected, the non-ambient generated exposure was not related to the ambient concentrations. This study highlights the importance of both ambient and non-ambient components of total personal exposure in the megacity of Guangzhou. Our results support the use of SO42- as a tracer of personal exposure to PM2.5 of ambient origin in environmental and epidemiological studies.

Measured Pulmonary and Systemic Markers of Inflammation and Oxidative Stress Following Wildland Firefighter Simulations.

OBJECTIVE: A controlled human exposure study was conducted to investigate the impact of inhalational exposures to wood smoke PM2.5 on measured concentrations of airway and systemic inflammatory biomarkers. METHODS: Mimicking wildland firefighter activities, 10 participants were exposed to three doses of wood smoke PM2.5 (filtered-air, 250 µg/m, and 500 µg/m) while exercising on a treadmill. Exhaled breath condensate (EBC) and blood plasma samples were obtained pre-, immediately post-, and 1-hour postexposure. 8-isoprostane, pH, and myeloperoxidase were measured in EBC, while H2O2, surfactant protein D, and pentraxin-3 (PTX3) were measured in both EBC and plasma. RESULTS: Only pH, 8-isoprostane, and PTX3 displayed significant changes when comparing pre- and postexposures. CONCLUSIONS: Markers of inflammation and oxidative stress, including PTX3, pH, and 8-isoprostane in EBC and/or plasma, are sensitive to wood smoke inhalation, with further investigations warranted.

Air Toxics Under the Big Sky: Examining the Effectiveness of Authentic Scientific Research on High School Students' Science Skills and Interest.

Air Toxics Under the Big Sky is an environmental science outreach/education program that incorporates the Next Generation Science Standards (NGSS) 8 Practices with the goal of promoting knowledge and understanding of authentic scientific research in high school classrooms through air quality research. A quasi-experimental design was used in order to understand: 1) how the program affects student understanding of scientific inquiry and research and 2) how the open inquiry learning opportunities provided by the program increase student interest in science as a career path. Treatment students received instruction related to air pollution (airborne particulate matter), associated health concerns, and training on how to operate air quality testing equipment. They then participated in a yearlong scientific research project in which they developed and tested hypotheses through research of their own design regarding the sources and concentrations of air pollution in their homes and communities. Results from an external evaluation revealed that treatment students developed a deeper understanding of scientific research than did comparison students, as measured by their ability to generate good hypotheses and research designs, and equally expressed an increased interest in pursuing a career in science. These results emphasize the value of and need for authentic science learning opportunities in the modern science classroom.

The Clean Air and Healthy Homes Program: A Model for Authentic Science Learning.

The Clean Air and Healthy Homes Program (CAHHP) is a science education outreach program that involves students in research of their own design related to indoor and outdoor air pollution and links with respiratory health. The program, which provides equipment, lesson plans, and support to middle and high school classrooms and professional development for teachers, is an excellent model of how to engage students in relevant and authentic science research and learning. This article describes the current program, how it promotes authentic science learning in secondary science education, and the positive impact it has had on student learning and attitudes.'