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.

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.

Indoor particulate matter in rural, wood stove heated homes.

Ambient particulate matter (PM) exposures have adverse impacts on public health, but research evaluating indoor PM concentrations in rural homes in the United States using wood as fuel for heating is limited. Our objectives were to characterize indoor PM mass and particle number concentrations (PNCs), quantify infiltration of outdoor PM into the indoor environment, and investigate potential predictors of concentrations and infiltration in 96 homes in the northwestern US and Alaska using wood stoves as the primary source of heating. During two forty-eight hour sampling periods during the pre-intervention winter of a randomized trial, we assessed PM mass (<2.5µm) and PNCs (particles/cm(3)) in six size fractions (0.30-0.49, 0.50-0.99, 1.00-2.49, 2.5-5.0, 5.0-10.0, 10.0+µm). Daily mean (sd) PM2.5 concentrations were 28.8 (28.5)µg/m(3) during the first sampling period and 29.1 (30.1)µg/m(3) during the second period. In repeated measures analyses, household income was inversely associated with PM2.5 and smaller size fraction PNCs, in particular. Time of day was a significant predictor of indoor and outdoor PM2.5 concentrations, and infiltration efficiency was relatively low (Finf (sd)=0.27 (0.20)). Our findings demonstrate relatively high mean PM concentrations in these wood burning homes and suggest potential targets for interventions for improving indoor air quality and health in rural settings.

Impacts of air cleaners on indoor air quality in residences impacted by wood smoke.

Residential wood combustion is an important source of ambient air pollution, accounting for over 25% of fine particulate matter (PM2.5) emissions in Canada. In addition to these ambient contributions, wood smoke pollutants can enter the indoor environment directly when loading or stoking stoves, resulting in a high potential for human exposure. A study of the effectiveness of air cleaners at reducing wood smoke-associated PM2.5 of indoor and outdoor origin was conducted in 31 homes during winter 2009-10. Day 1, the residents' wood burning appliance operated as usual with no air cleaner. Days 2 and 3, the wood burning appliance was not operational and the air cleaner was randomly chosen to operate in "filtration" or "placebo filtration" mode. When the air cleaner was operating, total indoor PM2.5 levels were significantly lower than on placebo filtration days (p = 0.0001) resulting in a median reduction of 52%. There was also a reduction in the median PM2.5 infiltration factor from 0.56 to 0.26 between these 2 days, suggesting the air cleaner was responsible for increased PM2.5 deposition on filtration days. Our findings suggest that the use of an air cleaner reduces exposure to indoor PM2.5 resulting from both indoor and ambient wood smoke sources.

A rural community intervention targeting biomass combustion sources: effects on air quality and reporting of children's respiratory outcomes.

OBJECTIVE: Improvements in urban air quality are largely driven by controls on industrial and mobile source emissions, but such factors may have limited influence on many rural environments where biomass combustion (eg, wood stoves) serves as the primary source of fine particulate matter (PM(2.5)). The authors tracked changes in children's respiratory health during a wood stove intervention in a rural mountain valley community heavily impacted by wood smoke-derived PM(2.5). METHODS: Community-wide impacts on children's health were assessed by prospectively collecting surveys from parents of school children during four winter periods in Libby, Montana. Generalised estimating equations with a logit link were used to estimate the effect of reduction in ambient PM(2.5) on wheeze prevalence and other reported symptoms and infections. RESULTS: Over 1100 wood stoves were replaced with new lower emission wood stoves or other heating sources. Ambient PM(2.5) was 27.6% lower in the winters following the changeout programme compared with baseline winters. There was a 26.7% (95% CI 3.0% to 44.6%) reduced odds of reported wheeze for a 5 µg/m(3) decrease in average winter PM(2.5). Lower ambient PM(2.5) was also associated with reduced odds for reported respiratory infections, including cold (25.4% (95% CI 7.6% to 39.7%)), bronchitis (54.6% (95% CI 24.2% to 72.8%)), influenza (52.3% (95% CI 42.5% to 60.5%)) and throat infection (45.1% (95% CI 29.0% to 57.6%)). CONCLUSION: This wood stove intervention provided a unique opportunity to prospectively observe health benefits resulting from a targeted air pollution reduction strategy in a rural community.

Base camp personnel exposure to particulate matter during wildland fire suppression activities.

Wildland fire base camps commonly house thousands of support personnel for weeks at a time. The selection of the location of these base camps is largely a strategic decision that incorporates many factors, one of which is the potential impact of biomass smoke from the nearby fire event. Biomass smoke has many documented adverse health effects due, primarily, to high levels of fine particulate matter (PM(2.5)). Minimizing particulate matter exposure to potentially susceptible individuals working as support personnel in the base camp is vital. In addition to smoke from nearby wildland fires, base camp operations have the potential to generate particulate matter via vehicle emissions, dust, and generator use. We monitored particulate matter at three base camps during the fire season of 2009 in Washington, Oregon, and California. During the sampling events, 1-min time-weighted averages of PM(2.5) and particle counts from three size fractions (0.3-0.5 microns, 0.5-1.0 microns, and 1.0-2.5 microns) were measured. Results showed that all PM size fractions (as well as overall PM(2.5) concentrations) were higher during the overnight hours, a trend that was consistent at all camps. Our results provide evidence of camp-based, site-specific sources of PM(2.5) that could potentially exceed the contributions from the nearby wildfire. These exposures could adversely impact wildland firefighters who sleep in the camp, as well as the camp support personnel, who could include susceptible individuals. A better understanding of the sources and patterns of poor air quality within base camps would help to inform prevention strategies to reduce personnel exposures.

Amphibole asbestos in tree bark--a review of findings for this inhalational exposure source in Libby, Montana.

In June 2009, the U.S. Environmental Protection Agency (EPA) designated the town of Libby, Montana, a public health emergency--the first and only time the EPA has made such a determination under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). From about 1920 until 1990, the leading source of vermiculite ore for the United States and the world was from a mine near Libby. This vermiculite ore was contaminated with fibrous and asbestiform amphibole in veins throughout the deposit. Today, areas surrounding the abandoned vermiculite processing/mining facilities and much of the town of Libby are contaminated with these asbestos fibers, contributing to an outbreak of asbestos-related diseases in the Libby population. Trees in Libby and in forested areas surrounding the abandoned mine have accumulated amphibole asbestos fibers on their bark surface, providing for inhalational exposures. Several studies have been conducted to further understand this exposure pathway. To address exposures to the public, Libby amphibole (LA) was measured in personal breathing zone and Tyvek surface wipe samples collected during firewood harvesting simulations, as well as in the ash and emissions of woodstoves when amphibole-contaminated firewood was combusted. Occupational studies simulating wildland firefighting and routine U.S. Department of Agriculture (USDA) Forest Service activities have also been conducted in the forested areas surrounding the abandoned mine, demonstrating the potential for inhalational exposures during common regional workplace activities. We present a review of the findings of this emerging environmental health concern impacting not only the residents of Libby but applicable to other populations living near asbestos-contaminated areas.

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.

Assessing the impact of a wood stove replacement program on air quality and children's health.

Many rural mountain valley communities experience elevated ambient levels of fine particulate matter (PM*) in the winter, because of contributions from residential wood-burning appliances and sustained temperature inversion periods during the cold season. A wood stove change-out program was implemented in a community heavily affected by wood-smoke-derived PM2.5 (PM < or = 2.5 microm in aerodynamic diameter). The objectives of this study were to evaluate the impact of this intervention program on ambient and indoor PM2.5 concentrations and to identify possible corresponding changes in the frequency of childhood respiratory symptoms and infections and illness-related school absences. Over 1100 old wood stoves were replaced with new EPA-certified wood stoves or other heating sources. Ambient PM2.5 concentrations were 30% lower in the winter after the changeout program, compared with baseline winters, which brought the community's ambient air within the PM2.5 standards of the U.S. Environmental Protection Agency (U.S. EPA). The installation of a new wood stove resulted in an overall reduction in indoor PM2.5 concentrations in a small sample of wood-burning homes, but the effects were highly variable across homes. Community-level reductions in wood-smoke-derived PM2.5 concentration were associated with decreased reports of childhood wheeze and of other childhood respiratory health conditions. The association was not limited to children living in homes with wood stoves nor does it appear to be limited to susceptible children (e.g., children with asthma). Community-level reductions in wood-smoke-derived PM2.5 concentration were also associated with lower illness-related school absences among older children, but this finding was not consistent across all age-groups. This community-level intervention provided a unique opportunity to prospectively observe exposure and outcome changes resulting from a targeted air pollution reduction strategy.

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.

Wood smoke risk assessment: defining the questions.

Risk assessment provides a framework for combining and evaluating scientific data on source-to-health effects for contaminants that could potentially affect the health of human populations. It utilizes an integrated approach to hazard identification, dose response, exposure assessment, and risk characterization. Since the range of potential exposure scenarios is considerable, given the complexity of wood-smoke sources and emissions, there is a need for defining the critical characteristics for the key parameters leading to adverse health outcomes. During the International Biomass Smoke and Health Effects (IBSHE) conference at the University of Montana (August 2007), the breakout group entitled "Risk Assessment: Defining the Questions" was tasked with evaluating the current state of the science in regard to risk assessment involving biomass smoke exposure. As a result of these discussions, important data gaps and future research questions were identified that are reported in this article.

Fine particulate matter source apportionment following a large woodstove changeout program in Libby, Montana.

Before a community-wide woodstove changeout program, a chemical mass balance (CMB) source apportionment study was conducted in Libby, MT, during the winter of 2003-2004 to identify the sources of fine particulate matter (PM2.5) within the valley. Results from this study showed that residential woodstoves were the major source, contributing approximately 80% of the ambient PM2.5 throughout the winter months. In an effort to lower the ambient PM2.5, a large woodstove changeout program was conducted in Libby from 2005 to 2007 in which nearly 1200 old woodstoves were changed out with cleaner burning models. During the winter of 2007-2008, a follow-up CMB source apportionment study was conducted to evaluate the effectiveness of the changeout. Results from this study showed that average winter PM2.5 mass was reduced by 20%, and woodsmoke-related PM2.5 (as identified by the CMB model) was reduced by 28% when compared with the pre-changeout winter of 2003-2004. These results suggest that a woodstove changeout can be an effective tool in reducing ambient levels of PM2.5 in woodstove-impacted communities.

A comparison of 1978 and 2006 peak pollen seasons and sampling methods in Missoula, Montana.

A study was conducted in Missoula, Montana to compare local pollen counts from 1978 with those measured nearly 30 years later in 2006 using two different measurement techniques (Durham gravimetric sampler and a Burkard volumetric sampler). Trends in peak pollen times measured during the spring, summer and autumn, respectively, were compared between the two years by Pearson's correlation and frequency of occurrence of plant genus. Meteorological conditions were also examined during each of the two study periods.In comparing the two years, there was a statistically significant linear association between the different counts for the months of April through August, with similar levels of pollen types for any given month. The five predominant pollen types (based on counts) identified in each study were Pinus, Poaceae, Populus, Alnus, and Betula for 2006 and Pinus, Poaceae, Populus, Acer and Artemisia for 1978. In summary most of the genera displayed similar peak pollination timing between the two years, suggesting that results from the Durham (gravimetric) and Burkard (volumetric) sampling methods are comparable when reporting relative frequency of occurrence.

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.

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.

Urinary levoglucosan as a biomarker of wood smoke exposure: observations in a mouse model and in children.

BACKGROUND: Biomass smoke is an important source of particulate matter (PM), and much remains to be discovered with respect to the human health effects associated with this specific PM source. Exposure to biomass smoke can occur in one of two main categories: short-term exposures consist of periodic, seasonal exposures typified by communities near forest fires or intentional agricultural burning, and long-term exposures are chronic and typified by the use of biomass materials for cooking or heating. Levoglucosan (LG), a sugar anhydride released by combustion of cellulose-containing materials, is an attractive candidate as a biomarker of wood smoke exposure. OBJECTIVES: In the present study, Balb/c mice and children were assessed for LG in urine to determine its feasibility as a biomarker. METHODS: We performed urinary detection of LG by gas chromatography/mass spectrometry after intranasal instillations of LG or concentrated PM (mice) or biomass exposure (mice or humans). RESULTS: After instillation, we recovered most of the LG within the first 4 hr. Experiments using glucose instillation proved the specificity of our system, and instillation of concentrated PM from wood smoke, ambient air, and diesel exhaust supported a connection between wood smoke and LG. In addition, LG was detected in the urine of mice exposed to wood smoke. Finally, a pilot human study proved our ability to detect LG in urine of children. CONCLUSIONS: These results demonstrate that LG in the lungs is detectable in the urine of both mice and humans and that it is a good candidate as a biomarker of exposure to biomass smoke.