Airborne endotoxin is associated with respiratory illness in the first 2 years of life

Indoor air quality in remote first nations communities in Ontario, Canada

A recent study of the health of Indigenous children in four First Nations Communities in remote northwestern Ontario found that 21% of children had been admitted to hospital for respiratory infections before age 2 years. Here we report a detailed analysis of the housing conditions in these communities. We employed a variety of statistical methods, including linear regression, mixed models, and logistic regression, to assess the correlations between housing conditions and loadings of biocontaminants (dust mite allergens, fungal glucan, and endotoxin) and indoor concentrations of PM2.5, CO2, benzene, and formaldehyde. The houses (n = 101) were crowded with an average of approximately 7 people. Approximately 27% of the homes had sustained CO2 concentrations above 1500 ppm. Most homes had more than one smoker. Commercial tobacco smoking and the use of non-electric heating (e.g., wood, oil) were associated with increased fine particle concentrations. Over 90% of the homes lacked working Heat Recovery Ventilators (HRVs), which was associated with increased fine particle concentrations and higher CO2. Of the 101 homes, 12 had mold damage sufficient to increase the relative risk of respiratory disease. This resulted from roof leaks, through walls or around the windows due to construction defects or lack of maintenance. A similar percentage had mold resulting from condensation on windows. Endotoxin loadings were much higher than any previous study in Canada. This work provides evidence for the need for more effort to repair existing houses and to ensure the HRVs are properly installed and maintained.

Physicochemical characterization and oxidative potential of size fractionated Particulate Matter: Uptake, genotoxicity and mutagenicity in V-79 cells

For many years, the impact of Particulate Matter (PM) in the ambient air has been one of the major concerns for the environment and human health. The consideration of the heterogeneity and complexity of different size fractions is notably important for the assessment of PM toxicological effects. The aim of the study was to present a comprehensive size-composition-morphology characterization and to assess the oxidative potential, genotoxicity, and mutagenicity of the atmospheric PM fractions, collected by using MOUDI near a busy roadside in Lucknow, India. Physicochemical characterization of ambient coarse particles (1.8-10 µm), fine particles (0.32-1.8 µm), quasi-ultrafine (0.1-0.32 µm) and ultrafine particles (≤0.1 µm) along with SRM 1649b was done using TEM, SEM, DLS, NTA, ICP-MS, and IC in parallel with the estimation of exogenous Reactive Oxygen Species (ROS) by acellular assays. In this study, two different acellular assays, dithiothreitol (DTT) and the CM-H₂DCFDA assay, indicated stronger mass-normalized bioactivity for different size ranges. Enrichment factor analysis indicated that the different size fractions were highly enriched with elements of anthropogenic origin as compared to elements of crustal origin. The endotoxin concentration in different size fractions was also estimated. Cellular studies demonstrated significant uptake, cytotoxicity, ultrastructural changes, cellular ROS generation, and changes in the different phases of the cell cycle (Sub G1, G1, S, G2/M) exposed to different size fractions. The Comet assay and the Micronucleus assay were used to estimate genotoxicity. Mutagenic potential was revealed by the HGPRT gene forward mutation assay in V-97 cells. Conclusively, our results clearly indicate that the genotoxic and mutagenic potential of the coarse PM was greater than the other fractions, and interestingly, the ultrafine PM has higher bioactivity as compared to quasi-ultrafine PM.

Birth cohort studies using symptom diaries for assessing respiratory diseases–a scoping review

Background

Respiratory infections are the most frequent health problem in childhood leading to morbidity and socioeconomic burden. Studying symptoms of respiratory infections in home based settings requires dedicated prospective cohort studies using diaries. However, no information is available on which birth cohort studies using symptom diary data. A review of birth cohort studies with available symptom diary data, follow-up data, and bio samples is needed to support research collaborations and create potential synergies.

Methods

We conducted a scoping review of birth cohort studies using diaries for the collection of respiratory symptoms. The scoping review was conducted in accordance with the PRISMA Extension. We searched the electronic databases PubMed, Embase, Web of science and CINAHL (last search November 2020) resulting in 5872 records (based on title and abstract screening) eligible for further screening.

Results

We examined 735 records as full text articles and finally included 57 according to predefined inclusion criteria. We identified 22 birth cohort studies that collect(ed) data on respiratory symptoms using a symptom diary starting at birth. Numbers of participants ranged from 129 to 8677. Eight studies collected symptom diary information only for the first year of life, nine for the first two years or less and six between three and six years. Most of the cohorts collected biosamples (n = 18) and information on environmental exposures (n = 19).

Conclusion

Information on respiratory symptoms with daily resolution was collected in several birth cohorts, often including related biosamples, and these data and samples can be used to study full spectrum of infections, particularly including those which did not require medical treatment.

Poly-l-lysine-Functionalized Green-Light-Emitting Carbon Dots as a Fluorescence Turn-on Sensor for Ultrasensitive Detection of Endotoxin

Herein, we report a facile, ultrasensitive, and selective fluorescence turn-on sensing strategy based on green-light-emitting functional nanodots for the detection of bacterial lipopolysaccharide (LPS) endotoxin. In this protocol, first, the pure carbon dots (CDs) with a fairly high quantum yield were prepared by microwave-assisted pyrolysis of citric acid in the presence of urea. Subsequently, the carboxyl-group-rich surfaces of the CDs were allowed to conjugate with the poly-l-lysine (PLL) using an EDC-NHS amidization method to obtain the PLL-modified CDs (PLL-CDs). The LPS could specifically bind to the PLL at the PLL-CD surfaces, and this binding enabled an electron transfer from the phosphate groups of LPS to the carbon core through the PLL bridge, thus resulting in a fluorescence enhancement. Interestingly, this fluorescent turn-on sensor provided a detection limit of 68.3 fM in PBS (pH 7.4), which is the lowest ever reported among all of the synthetic assays for LPS detection. Furthermore, our fluorescent probe was able to show a remarkable selectivity toward LPS over a range of commonly known interfering substances. Thus, this study demonstrated the feasibility of using specific LPS binding to PLL to drive molecular recognition in aqueous medium and offered an effective fluorescence turn-on sensing strategy to detect bacterial endotoxin in diverse clinical and biological applications.

Indoor microbiome and risk of lower respiratory tract infections among children under-five years: A meta-analysis

We investigated whether exposure to microbiome within the indoor environment is associated with risk of lower respiratory tract infections (LRTI) among children under 5 years of age. Electronic scientific repositories; PubMed, Scopus, Web of Science, GreenFILE, EMBASE, and Cochrane library were searched and screened through July 2019 for published reports for inclusion in the meta-analysis. Studies were eligible for inclusion if they reported an adjusted measure of risk for LRTI associated with IM exposure, including the relative risk (RR) or odds ratio (OR) and confidence interval (CI). The pooled OR was computed using the inverse of variance method for weighting. Sensitivity analysis was used to evaluate the effect of individual studies, while heterogeneity was evaluated by I² statistics using RevMan 5.3. Seven studies were eligible for inclusion in our meta-analysis. Exposure to a higher concentration of IM was associated with an increased risk of LRTI [OR:1.20 (1.11, 1.33), P < .0001]. The risk was stronger with exposure to total fungal concentration [OR:1.27 (1.13, 1.44), P < .0001] than visible molds [OR:1.20 (1.07, 1.34, P = .001]. Under-five children exposed to higher IM concentration are likely at increased risk of LRTI. Interventions addressing IM exposure should be considered in the management of LRTI among under-five children.

Household airborne endotoxin associated with asthma and allergy in elementary school-age children: a case-control study in Kaohsiung, Taiwan

To evaluate the association between the presence of asthma and allergy, and airborne endotoxin in homes of school-age children in Kaohsiung City, Taiwan, with a case-control study design by matching the age and class exposure. Data collection of home visits included an interviewer-administered questionnaire and air sampling of participants' homes for endotoxin, bacteria, and fungi, as well as temperature and relative humidity measurements. Endotoxin was detected in all air samples with a median value of 0.67 EU m^-3. In the adjusted logistic regression model, household airborne endotoxin was associated with higher prevalence of asthma and allergy; OR = 4.88 (95% CI 1.16-20.55) for Q3 (between 0.67 and 1.97 EU m ^-3) vs. Q1 (< 0.31 EU m ^-3), with statistical significance. Airborne fungi were associated with higher prevalence of asthma and allergy; OR = 4.47 (95% CI 1.13-17.69) for Q3 (between 314 and 699 CFU m ^-3) vs. Q1 (< 159 CFU m ^-3) in adjusted logistic regression models. Airborne endotoxin and fungi were significantly associated with children's asthma and allergy.

Generation of Viable Bacterial and Fungal Aerosols during Biomass Combustion

Biomass combustion is known to be one of the main contributors to air pollution. However, the influence of biomass burning on the distribution of viable bacterial and fungal aerosols is uncertain. This study aimed to examine survivability of bacteria and fungi in the post-combustion products, and to investigate the aerosolization of viable cells during combustion of different types of organic materials. Laboratory experiments included a small-scale combustion of organic materials contaminated with microorganisms in order to determine the survivability of microbes in the combustion products and the potential aerosolization of viable cells during combustion. Field experiments were completed during intentional and prescribed biomass burning events in order to investigate the aerosolization mechanisms that are not available at the laboratory scale. Laboratory experiments did not demonstrate aerosolization of microorganisms during biomass combustion. However, the relatively high survival rate of bacteria in the combustion products ought to be accounted for, as the surviving microorganisms can potentially be aerosolized by high velocity natural air flows. Field investigations demonstrated significant increase in the bioaerosol concentration above natural background during and after biomass combustion.

Indoor ozone and particulate matter modify the association between airborne endotoxin and schoolchildren's lung function

BACKGROUND

To date, the effect of household airborne pollutants on the association between airborne endotoxin and lung function of schoolchildren is unknown.

OBJECTIVES

The objective of this study is to evaluate whether indoor air pollutants such as carbon monoxide (CO), carbon dioxide (CO₂), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), particulate matter with aerodynamic diameter <10 and 2.5 μm (PM₁₀, PM_2.5) can modify the association between airborne endotoxin and school children's lung function in a heavy industrial city in Taiwan.

METHODS

We recruited 120 elementary school-age children in Kaohsiung City, Taiwan. Aerosol samples were collected on a filter membrane for 24 h period and then analyzed for endotoxin. Air pollutants were measured for 24 h in living rooms while school children's lung function was measured. The modification of air pollutants on the relationship between airborne endotoxin and children's lung function was estimated after adjusting the gender, age, height, weight, and case-control status.

RESULTS

We found that both O₃ and PM₁₀ concentrations significantly modified the relationships between airborne endotoxin and school children's lung function. Among children living in homes with O₃ ≥ 0.01 ppm or PM₁₀ ≥ 62 μg/m³, airborne endotoxin was negatively associated with lung functions, whereas among those living in homes with O₃ < 0.01 ppm or PM₁₀ < 62 μg/m³, airborne endotoxin was positively associated with lung functions.

CONCLUSIONS

The indoor air pollutant concentration of O₃ and PM₁₀ modifies the association between airborne endotoxin and school children's lung function.

Jumping on the bed and associated increases of PM10, PM2.5, PM1, airborne endotoxin, bacteria, and fungi concentrations

Jumping on the bed is a favorite behavior of children; however, no study has investigated the increased air pollutants resulting from jumping on the bed. Therefore, we aimed to investigate the elevated concentrations of particulate matter (PM) and bioaerosols from jumping on the bed and making the bed. Simulation of jumping on the bed and making the bed was performed at sixty schoolchildren's houses in Taiwan. PM₁₀, PM_2.5, PM₁ (PM with aerodynamic diameter less than 10, 2.5, and 1 μm, respectively) and airborne bacteria, fungi and endotoxin concentrations were simultaneously measured over simulation and background periods. Our results show the increase of PM₁₀, PM_2.5, PM₁, airborne bacteria and fungi through the behavior of jumping on the bed (by 414 μg m-3, 353 μg m-3, 349 μg m-3, 6569 CFU m-3 and 978 CFU m-3, respectively). When making the bed, the PM₁₀, PM_2.5, PM₁, airborne bacteria and fungi also significantly increased by 4.69 μg m-3, 4.09 μg m-3, 4.15 μg m-3, 8569 CFU m-3, and 779 CFU m-3, respectively. Airborne endotoxin concentrations significantly increased by 21.76 EU m-3 following jumping on the bed and making the bed. Moreover, when jumping on the bed, higher PM_2.5 and PM₁ concentrations in houses with furry pets rather than no furry pets, and less airborne fungi in apartments than in townhouses were found. For making the bed, lower airborne fungi was found in houses using essential oils rather than no essential oils using. The airborne endotoxin concentrations were positively associated with furry pets and smokers in the homes and negatively correlated to the home with window opening with a statistical significance during the periods of jumping on the bed and making the bed. In conclusion, significant increases of PM and bioaerosols during jumping on the bed and making the bed may need to be concerned.

Factors affecting ambient endotoxin and particulate matter concentrations around air vents of subway stations in South Korea

Levels of airborne endotoxins and particulate matter less than 10 μm and 2.5 μm in diameter (PM) were measured in the air vents of subway stations in Seoul, South Korea, and factors affecting both pollutants were analyzed. The measurements were completed from March 2016 to February 2017 for eight air vents situated at the ground level around the subway stations. A total of 166 air samples were collected and analyzed using the kinetic limulus amebocyte lysate assay. Endotoxin levels ranged from not detected to 1.986 EU m^-3, with a mean of 0.227 EU m^-3. The results showed significantly different PM levels from the measurements reported by AIRKOREA as part of the comprehensive air quality index. This can be attributed to different sampling sites in the same area. Endotoxin levels tended to be higher in fall compared to summer. Airborne bacteria levels showed a pattern similar to the endotoxin levels, but no significant association was reported between them. The levels of endotoxins around air vents with a glass cover and streets that allowed smoking were significantly higher than those not containing a walled barrier and streets in which smoking was prohibited. Multivariate regression analysis showed that the factors affecting endotoxin levels comprised air vents with a glass cover (coefficient = 0.106, p = 0.014) and season (coefficient = 0.062, p < 0.0001). Therefore, installing barriers on the air vents and prohibiting smoking in streets to which the vents open may be effective ways to lessen exposure to airborne endotoxin levels around air vents.

Airborne endotoxin concentrations in indoor and outdoor particulate matter and their predictors in an urban city

Endotoxins are an important biological component of particulate matter and have been associated with adverse effects on human health. There have been some recent studies on airborne endotoxin concentrations. We collected fine (PM_2.5 ) and coarse (PM_10-2.5 ) particulate matter twice on weekdays and weekends each for 48 hour, inside and outside 55 homes in an urban city in Japan. Endotoxin concentrations in both fractions were measured using the kinetic Limulus Amebocyte Lysate assay. The relationships between endotoxin concentrations and household characteristics were evaluated for each fraction. Both indoor and outdoor endotoxin concentrations were higher in PM_2.5 than in PM_10-2.5 . In both PM_2.5 and PM_10-2.5 , indoor endotoxin concentrations were higher than outdoor concentrations, and the indoor endotoxin concentrations significantly correlated with outdoor concentrations in each fraction (R² =0.458 and 0.198, respectively). Indoor endotoxin concentrations in PM_2.5 were significantly higher in homes with tatami or carpet flooring and in homes with pets, and lower in homes that used air purifiers. Indoor endotoxin concentrations in PM_10-2.5 were significantly higher in homes with two or more children and homes with tatami or carpet flooring. These results showed that the indoor endotoxin concentrations were associated with the household characteristics in addition to outdoor endotoxin concentrations.

Influence of exposure to coarse, fine and ultrafine urban particulate matter and their biological constituents on neural biomarkers in a randomized controlled crossover study

BACKGROUND

Epidemiological studies have reported associations between air pollution and neuro-psychological conditions. Biological mechanisms behind these findings are still not clear.

OBJECTIVES

We examined changes in blood and urinary neural biomarkers following exposure to concentrated ambient coarse, fine and ultrafine particles.

METHODS

Fifty healthy non-smoking volunteers, mean age 28years, were exposed to coarse (2.5-10μm, mean 213μg/m³) and fine (0.15-2.5μm, mean 238μg/m³) concentrated ambient particles (CAPs), and filtered ambient and/or medical air. Twenty-five participants were exposed to ultrafine CAP (mean size 59.6nm, range 47.0-69.8nm), mean (136μg/m³) and filtered medical air. Exposures lasted 130min, separated by ≥2weeks, and the biological constituents endotoxin and β-1,3-d-glucan of each particle size fraction were measured. Blood and urine samples were collected pre-exposure, and 1-hour and 21-hour post-exposure to determine neural biomarker levels. Mixed-model regressions assessed associations between exposures and changes in biomarker levels.

RESULTS

Results were expressed as percent change from daily pre-exposure biomarker levels. Exposure to coarse CAP was significantly associated with increased urinary levels of the stress-related biomarkers vanillylmandelic acid (VMA) and cortisol when compared with exposure to filtered medical air [20% (95% confidence interval: 1.0%, 38%) and 64% (0.2%, 127%), respectively] 21hours post-exposure. However exposure to coarse CAP was significantly associated with decreases in blood cortisol [-26.0% (-42.4%, -9.6%) and -22.4% (-43.7%, -1.1%) at 1h and 21h post-exposure, respectively]. Biological molecules present in coarse CAP were significantly associated with blood biomarkers indicative of blood brain barrier integrity. Endotoxin content was significantly associated with increased blood ubiquitin C-terminal hydrolase L1 [UCHL1, 11% (5.3%, 16%) per ln(ng/m³+1)] 1-hour post-exposure, while β-1,3-d-glucan was significantly associated with increased blood S100B [6.3% (3.2%, 9.4%) per ln(ng/m³+1)], as well as UCHL1 [3.1% (0.4%, 5.9%) per ln(ng/m³+1)], one-hour post-exposure. Fine CAP was marginally associated with increased blood UCHL1 when compared with exposure to filtered medical air [17.7% (-1.7%, 37.2%), p=0.07] 21hours post-exposure. Ultrafine CAP was not significantly associated with changes in any blood and urinary neural biomarkers examined.

CONCLUSION

Ambient coarse particulate matter and its biological constituents may influence neural biomarker levels that reflect perturbations of blood-brain barrier integrity and systemic stress response.

Predictors and respiratory depositions of airborne endotoxin in homes using biomass fuels and LPG gas for cooking

Recent studies have highlighted the presence of endotoxin in indoor air and its role in respiratory morbidities. Burning of household fuels including unprocessed wood and dried animal dung could be a major source of endotoxin in homes. We measured endotoxin levels in different size fractions of airborne particles (PM10, PM2.5, and PM1), and estimated the deposition of particle-bound endotoxin in the respiratory tract. The study was carried out in homes burning solid biomass fuel (n=35) and LPG (n=35). Sample filters were analyzed for endotoxin and organic carbon (OC) content. Household characteristics including temperature, relative humidity, and carbon dioxide levels were also recorded. Multivariate regression models were used to estimate the contributing factors for airborne endotoxin. Respiratory deposition doses were calculated using a computer-based model. We found a higher endotoxin concentration in PM2.5 fractions of the particle in both LPG (median: 110, interquartile range (IQR) 100-120 EU/m³) and biomass (median: 350, IQR: 315-430 EU/m³) burning homes. In the multivariate-adjusted model, burning of solid biomass fuel (β: 67; 95% CI: 10.5-124) emerged as the most significant predictor followed by OC (β: 4.7; 95% CI: 2.7-6.8), RH (β: 1.6; 95% CI: 0.76-2.4), and PM2.5 (β: 0.45; 95% CI: 0.11-0.78) for airborne endotoxin (P<0.05). We also observed an interaction between PM organic carbon content and household fuel in predicting the endotoxin levels. The model calculations showed that in biomass burning homes, total endotoxin deposition was higher among infants (59%) than in adult males (47%), of which at least 10% of inhaled endotoxin is deposited in the alveolar region of the lung. These results indicate that fine particles are significant contributors to the deposition of endotoxin in the alveolar region of the lung. Considering the paramount role of endotoxin exposure, and the source and timing of exposure on respiratory health, additional studies are warranted to guide evidence-based public health interventions.

Urban Enhancement of PM10 Bioaerosol Tracers Relative to Background Locations in the Midwestern United States

Bioaerosols are well-known immune-active particles that exacerbate respiratory diseases. Human exposures to bioaerosols and their resultant health impacts depend on their ambient concentrations, seasonal and spatial variation, and co-pollutants, which are not yet widely characterized. In this study, chemical and biological tracers of bioaerosols were quantified in respirable particulate matter (PM10) collected at three urban and three background sites in the Midwestern United States across four seasons in 2012. Endotoxins from gram negative bacteria (and a few gram positive bacteria), water-soluble proteins, and tracers for fungal spores (fungal glucans, arabitol and mannitol) were ubiquitous and showed significant seasonal variation and dependence on temperature. Fungal spores were elevated in spring and peaked in summer, following the seasonal growing cycle, while endotoxins peaked in autumn during the row crop harvesting season. Paired comparisons of bioaerosols in urban and background sites revealed significant urban enhancements in PM10, fungal glucans, endotoxins and water-soluble proteins relative to background locations, such that urban populations have a greater outdoor exposure to bioaerosols. These bioaerosols contribute, in part, to the urban excesses in PM10. Higher bioaerosol mass fractions in urban areas relative to background sites indicate that urban areas serve as a source of bioaerosols. Similar urban enhancements in water-soluble calcium and its correlation with bioaerosol tracers point towards wind-blown soil as an important source of bioaerosols in urban areas.

Urban Enhancement of PM10 Bioaerosol Tracers Relative to Background Locations in the Midwestern United States

Bioaerosols are well-known immune-active particles that exacerbate respiratory diseases. Human exposures to bioaerosols and their resultant health impacts depend on their ambient concentrations, seasonal and spatial variation, and co-pollutants, which are not yet widely characterized. In this study, chemical and biological tracers of bioaerosols were quantified in respirable particulate matter (PM₁₀) collected at three urban and three background sites in the Midwestern United States across four seasons in 2012. Endotoxins from gram negative bacteria (and a few gram positive bacteria), water-soluble proteins, and tracers for fungal spores (fungal glucans, arabitol and mannitol) were ubiquitous and showed significant seasonal variation and dependence on temperature. Fungal spores were elevated in spring and peaked in summer, following the seasonal growing cycle, while endotoxins peaked in autumn during the row crop harvesting season. Paired comparisons of bioaerosols in urban and background sites revealed significant urban enhancements in PM₁₀, fungal glucans, endotoxins and water-soluble proteins relative to background locations, such that urban populations have a greater outdoor exposure to bioaerosols. These bioaerosols contribute, in part, to the urban excesses in PM₁₀. Higher bioaerosol mass fractions in urban areas relative to background sites indicate that urban areas serve as a source of bioaerosols. Similar urban enhancements in water-soluble calcium and its correlation with bioaerosol tracers point towards wind-blown soil as an important source of bioaerosols in urban areas.

Seasonal variation in airborne endotoxin levels in indoor environments with different micro-environmental factors in Seoul, South Korea

This study evaluated the variation over a year in airborne endotoxin levels in the indoor environment of five university laboratories in Seoul, South Korea, and examined the micro-environmental factors that influenced endotoxin levels. These included temperature, relative humidity, CO2, CO, illumination, and wind velocity. A total of 174 air samples were collected and analyzed using the kinetic limulus amebocyte lysate assay. Endotoxin levels ranged from <0.001 to 8.90EU/m(3), with an overall geometric mean of 0.240EU/m(3). Endotoxin levels showed significantly negative correlation with temperature (r=-0.529, p<0.001), CO2 (r=-0.213, p<0.001) and illumination (r=-0.538, p<0.001). Endotoxin levels tended to be higher in winter. Endotoxin levels in laboratories with rabbits were significantly higher than those of laboratories with mice. Multivariate regression analysis showed that the environmental factors affecting endotoxin levels were temperature (coefficient=-0.388, p<0.001) and illumination (coefficient=-0.370, p<0.001). Strategies aimed at reducing airborne endotoxin levels in the indoor environments may be most effective if they focus on illumination.

Health effects of carbon-containing particulate matter: focus on sources and recent research program results

Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue.

Effects of ambient coarse, fine, and ultrafine particles and their biological constituents on systemic biomarkers: a controlled human exposure study

BACKGROUND

Ambient coarse, fine, and ultrafine particles have been associated with mortality and morbidity. Few studies have compared how various particle size fractions affect systemic biomarkers.

OBJECTIVES

We examined changes of blood and urinary biomarkers following exposures to three particle sizes.

METHODS

Fifty healthy nonsmoking volunteers, mean age of 28 years, were exposed to coarse (2.5-10 μm; mean, 213 μg/m3) and fine (0.15-2.5 μm; mean, 238 μg/m3) concentrated ambient particles (CAPs), and filtered ambient and/or medical air. Twenty-five participants were exposed to ultrafine CAP (< 0.3 μm; mean, 136 μg/m3) and filtered medical air. Exposures lasted 130 min, separated by ≥ 2 weeks. Blood/urine samples were collected preexposure and 1 hr and 21 hr postexposure to determine blood interleukin-6 and C-reactive protein (inflammation), endothelin-1 and vascular endothelial growth factor (VEGF; vascular mediators), and malondialdehyde (lipid peroxidation); as well as urinary VEGF, 8-hydroxy-deoxy-guanosine (DNA oxidation), and malondialdehyde. Mixed-model regressions assessed pre- and postexposure differences.

RESULTS

One hour postexposure, for every 100-μg/m3 increase, coarse CAP was associated with increased blood VEGF (2.41 pg/mL; 95% CI: 0.41, 4.40) in models adjusted for O3, fine CAP with increased urinary malondialdehyde in single- (0.31 nmol/mg creatinine; 95% CI: 0.02, 0.60) and two-pollutant models, and ultrafine CAP with increased urinary 8-hydroxydeoxyguanosine in single- (0.69 ng/mg creatinine; 95% CI: 0.09, 1.29) and two-pollutant models, lasting < 21 hr. Endotoxin was significantly associated with biomarker changes similar to those found with CAPs.

CONCLUSIONS

Ambient particles with various sizes/constituents may influence systemic biomarkers differently. Endotoxin in ambient particles may contribute to vascular mediator changes and oxidative stress.

Indicators of airborne fungal concentrations in urban homes: understanding the conditions that affect indoor fungal exposures

Indoor fungal exposure can compromise respiratory health. Low-income urban areas are of concern because of high asthma and allergy rates and housing disrepair. Understanding the conditions that affect indoor fungal exposures is important for assessing health risks and for developing mitigation strategies. We examined the types and concentrations of airborne fungi inside and outside of homes in low-income areas of Syracuse, NY as well as the effect of snow cover on fungal levels. At 103 homes, air samples for viable fungi were collected, occupants were interviewed and homes were inspected for visible mold, musty odors, water problems and other factors. Multivariable logistic regression was used to relate high fungal levels to home conditions. Predominant indoor fungi included Cladosporium, Penicillium, Aspergillus, Alternaria and hyaline unknowns. Basidiomycetes and an uncommon genus Acrodontium were also found frequently due to analysis methods developed for this project. With snow cover, outdoor total fungal levels were depressed and indoor concentrations were three times higher than outdoor on average with a maximum of 29 times higher. Visible mold was related to elevated levels of Penicillium (OR 4.11 95% CI 1.37-14.0) and bacteria (OR 3.79 95% CI 1.41-11.2). Musty, moldy odors were associated with elevated concentrations of total fungi (OR 3.48 95% CI 1.13-11.6) and basidiomycetes. Cockroaches, an indicator of moisture, were associated with elevated levels of Penicillium (OR 3.66 95% CI 1.16-13.1) and Aspergillus (OR 4.36 95% CI 1.60-13.4). Increasing relative humidity was associated with higher concentrations of Penicillium, yeasts and basidiomycetes. Visible mold, musty odors, indoor humidity and cockroaches are modifiable factors that were important determinants of indoor fungal exposures. Indoor air investigators should interpret indoor:outdoor fungal ratios cautiously when snow cover is present.

Role of infections in the induction and development of asthma: genetic and inflammatory drivers

Genetic and environmental factors interact to initiate and even maintain the course of asthma. As one of the highly risky environmental factors, infections in predisposed individuals can promote asthma development and exacerbations and/or prolong symptoms. This review will describe our current understanding of the genetic markers of innate immunity in the induction and development of asthma, the diverse roles of infections in modulating allergic inflammation, host susceptibility to infections and subsequent acute exacerbations in an allergic setting, and the therapeutic or preventive implications of existing knowledge. Current challenges and future directions in basic and clinical research of asthma are also discussed.

Endotoxins in indoor air and settled dust in primary schools in a subtropical climate

Endotoxins can significantly affect the air quality in school environments. However, there is currently no reliable method for the measurement of endotoxins, and there is a lack of reference values for endotoxin concentrations to aid in the interpretation of measurement results in school settings. We benchmarked the "baseline" range of endotoxin concentration in indoor air, together with endotoxin load in floor dust, and evaluated the correlation between endotoxin levels in indoor air and settled dust, as well as the effects of temperature and humidity on these levels in subtropical school settings. Bayesian hierarchical modeling indicated that the concentration in indoor air and the load in floor dust were generally (<95th percentile) <13 EU/m(3) and <24,570 EU/m(2), respectively. Exceeding these levels would indicate abnormal sources of endotoxins in the school environment and the need for further investigation. Metaregression indicated no relationship between endotoxin concentration and load, which points to the necessity for measuring endotoxin levels in both the air and settled dust. Temperature increases were associated with lower concentrations in indoor air and higher loads in floor dust. Higher levels of humidity may be associated with lower airborne endotoxin concentrations.

Indoor and outdoor particulate matter and endotoxin concentrations in an intensely agricultural county

The objectives of this study were to characterize rural populations' indoor and outdoor exposure to particulate matter (PM)(10), PM(2.5), and endotoxin and identify factors that influence these concentrations. Samples were collected at 197 rural households over five continuous days between 2007 and 2011. Geometric mean (GM) indoor PM(10) (21.2 μg/m(3)) and PM(2.5) (12.2 μg/m(3)) concentrations tended to be larger than outdoor PM(10) (19.6 μg/m(3)) and PM(2.5) (8.2 μg/m(3)) concentrations (PM(10) P=0.086; PM(2.5) P<0.001). Conversely, GM outdoor endotoxin concentrations (1.93 EU/m(-3)) were significantly larger than indoor (0.32 EU/m(3); P<0.001). Compared with measurements from previous urban studies, indoor and outdoor concentrations of PM(10) and PM(2.5) in the study area tended to be smaller, whereas ambient endotoxin concentrations measured outside rural households were 3-10 times larger. Contrary to our initial hypothesis, seasonality did not have a significant effect on mean ambient PM(10) concentrations; however, endotoxin concentrations in the autumn were almost seven times larger than winter. Excluding home cleanliness, the majority of agricultural and housing characteristics evaluated were found to be poorly associated with indoor and outdoor particulate and endotoxin concentrations.

Indoor dust and air concentrations of endotoxin in urban and rural environments

SIGNIFICANCE AND IMPACT OF THE STUDY

Rural dairy farming is associated with high exposure to indoor endotoxins as compared to rural nonfarming houses and urban houses. The time spent on the mattress (7 h for an adult) and of the proximity of the contaminated source should be taken into account with the other causes of exposure. Studies in European children from a farming background have shown that these children have a reduced risk of asthma and atopic sensitization compared to their urban counterparts. It has been suggested that this might be due to exposure to high levels of endotoxin in the farming environment. The aim of this study was to compare indoor endotoxin concentrations in air and dust samples from randomly selected urban and rural dwellings. In the rural area, endotoxins were analysed in farmhouses and nonfarmhouses as well as housing characteristics, lifestyle factors and agricultural practices likely to influence air and dust endotoxin levels. Endotoxin levels were significantly higher in floor (6600 ± 6100 vs 3600 ± 5600 and 3800 ± 17,000 ng g⁻¹; P < 0·001) and mattress dust (2900 ± 4100 vs 1100 ± 2400 and 800 ± 2600 ng g⁻¹; P < 0·001) from farmhouses compared to other rural and urban homes. However, no difference was observed between endotoxin concentrations in the air of urban and rural houses, and airborne endotoxin levels did not correlate to dust levels. Lack of ventilation and direct entry into the house were correlated with an increase in dust endotoxin levels. These results confirm that dairy farming is associated with high exposure to endotoxins in indoor dust samples. No difference was observed between indoor airborne concentrations between urban and rural houses. These results suggest that measuring endotoxin in dust is the most relevant method to assess endotoxin exposure.

Inflammatory and degranulation effect of yellow sand on RBL-2H3 cells in relation to chemical and biological constituents

Recent studie pointed out that allergic diseases have increased during the Asian dust storm event (ADSE) in Japan. Daily observations and the atmospheric concentrations of yellow sand (YS) aerosol have been increasing. In this study, YS samples collected from three sites of Japan during ADSE in 2009-2010 were used. The particles were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence-energy dispersive spectrometer (XRF-EDS). We investigate ability of YS extract on enhancing the chemical mediator release and cytokine production from rat basophilic leukemia (RBL-2H3) cells. The dust particles at Fukuoka and Tsukuba were abundant in aluminum (Al), iron (Fe), potassium (K) and titan (Ti) than those at Naha. Concentration of the trace endotoxin and Cryptomeria japonica pollen allergen (Cry j 1) were measured in YS extract. After exposure of RBL-2H3 cells to YS extract, the β-hexosaminidase (β-hex) release, tumor necrosis factor-alpha (TNF-α) production were enhanced in RBL-2H3 cells. This process depends on endotoxin, Cry j 1 and other allergen present in the YS extract. YS water extract also show a strong cytotoxic effect on the cells. This data suggest that low levels of endotoxin and Cry j 1 in YS may cause allergy during the ADSE.

Contribution of solid fuel, gas combustion, or tobacco smoke to indoor air pollutant concentrations in Irish and Scottish homes

  There are limited data describing pollutant levels inside homes that burn solid fuel within developed country settings with most studies describing test conditions or the effect of interventions. This study recruited homes in Ireland and Scotland where open combustion processes take place. Open combustion was classified as coal, peat, or wood fuel burning, use of a gas cooker or stove, or where there is at least one resident smoker. Twenty-four-hour data on airborne concentrations of particulate matter<2.5 μm in size (PM2.5), carbon monoxide (CO), endotoxin in inhalable dust and carbon dioxide (CO2), together with 2-3 week averaged concentrations of nitrogen dioxide (NO2) were collected in 100 houses during the winter and spring of 2009-2010. The geometric mean of the 24-h time-weighted-average (TWA) PM2.5 concentration was highest in homes with resident smokers (99 μg/m3--much higher than the WHO 24-h guidance value of 25 μg/m3). Lower geometric mean 24-h TWA levels were found in homes that burned coal (7 μg/m3) or wood (6 μg/m3) and in homes with gas cookers (7 μg/m3). In peat-burning homes, the average 24-h PM2.5 level recorded was 11 μg/m3. Airborne endotoxin, CO, CO2, and NO2 concentrations were generally within indoor air quality guidance levels.

PRACTICAL IMPLICATIONS

Little is known about indoor air quality (IAQ) in homes that burn solid or fossil-derived fuels in economically developed countries. Recent legislative changes have moved to improve IAQ at work and in enclosed public places, but there remains a real need to begin the process of quantifying the health burden that arises from indoor air pollution within domestic environments. This study demonstrates that homes in Scotland and Ireland that burn solid fuels or gas for heating and cooking have concentrations of air pollutants generally within guideline levels. Homes where combustion of cigarettes takes place have much poorer air quality.

Use of a robotic sampling platform to assess young children's exposure to indoor bioaerosols

Indoor exposures to allergens, mold spores, and endotoxin have been suggested as etiological agents of asthma; therefore, accurate determination of those exposures, especially in young children (6-36 months), is important for understanding the development of asthma. Because use of personal sampling equipment in this population is difficult, and in children <1 year of age impossible, we developed a personal sampling surrogate: the Pretoddler Inhalable Particulate Environmental Robotic (PIPER) sampler to better estimate their exposures. During sampling, PIPER simulates the activity patterns, speed of motion, and the height of the breathing zones of young children, and mechanically resuspends the deposited dust just as a young child does during running and crawling. The concentrations of allergens, mold spores, and endotoxin measured by PIPER were compared to those measured using traditional stationary air sampling method in 75 homes in central New Jersey, United States. Endotoxin was detected in all homes with median concentrations of 1.0 and 0.55 EU/m(3) for PIPER and stationary sampler, respectively. The difference in median concentrations obtained using the two methods was statistically significant for homes with carpeted floors (P = 0.0001) in the heating season. For such homes, the average ratio of endotoxin concentration measured by PIPER to the stationary sampler was 2.96 (95% CI 2.29-3.63). Fungal spores were detected in all homes, with median fungal concentrations of 316 and 380 spores/m(3) for PIPER and stationary sampler, respectively. For fungi, the difference between the two sampling methods was not statistically significant. For both sampling methods, the total airborne mold levels were statistically significantly higher in the non-heating season than in the heating season. Allergens were detected in ~15% of investigated homes. The data indicate that the traditional stationary air-sampling methods may substantially underestimate personal exposures to endotoxin, especially due to resuspension of dust from carpeted floor surfaces. A personal sampling surrogate, such as PIPER, is a feasible approach to estimate personal exposures in young children. PIPER should be seriously considered as the sampling platform for future exposure studies in young children.

PRACTICAL IMPLICATIONS

This study investigated potential indoor bioaerosol exposure of young children using a Pretoddler Inhalable Particulate Environmental Robotic (PIPER) sampler platform. The results show that the traditional stationary air-sampling methods can substantially underestimate personal exposures to resuspended material, and that a personal sampling surrogate, such as PIPER, offers a feasible surrogate for measuring personal inhalation exposures of young children.

Indoor environment and children's health: recent developments in chemical, biological, physical and social aspects

Much research is being carried out into indoor exposure to harmful agents. This review focused on the impact on children's health, taking a broad approach to the indoor environment and including chemical, microbial, physical and social aspects. Papers published from 2006 onwards were reviewed, with regards to scientific context. Most of publications dealt with chemical exposure. Apart from the ongoing issue of combustion by-products, most of these papers concerned semi volatile organic compounds (such as phthalates). These may be associated with neurotoxic, reprotoxic or respiratory effects and may, therefore, be of particular interest so far as children are concerned. In a lesser extent, volatile organic compounds (such as aldehydes) that have mainly respiratory effects are still studied. Assessing exposure to metals is still of concern, with increasing interest in bioaccessibility. Most of the papers on microbial exposure focused on respiratory tract infections, especially asthma linked to allergens and bio-aerosols. Physical exposure includes noise and electromagnetic fields, and articles dealt with the auditory and non auditory effects of noise. Articles on radiofrequency electromagnetic fields mainly concerned questions about non-thermal effects and papers on extremely low-frequency magnetic fields focused on the characterization of exposure. The impact of the indoor environment on children's health cannot be assessed merely by considering the effect of these different types of exposure: this review highlights new findings and also discusses the interactions between agents in indoor environments and also with social aspects.

Respiratory and allergic health effects of dampness, mold, and dampness-related agents: a review of the epidemiologic evidence

OBJECTIVES

Many studies have shown consistent associations between evident indoor dampness or mold and respiratory or allergic health effects, but causal links remain unclear. Findings on measured microbiologic factors have received little review. We conducted an updated, comprehensive review on these topics.

DATA SOURCES

We reviewed eligible peer-reviewed epidemiologic studies or quantitative meta-analyses, up to late 2009, on dampness, mold, or other microbiologic agents and respiratory or allergic effects.

DATA EXTRACTION

We evaluated evidence for causation or association between qualitative/subjective assessments of dampness or mold (considered together) and specific health outcomes. We separately considered evidence for associations between specific quantitative measurements of microbiologic factors and each health outcome.

DATA SYNTHESIS

Evidence from epidemiologic studies and meta-analyses showed indoor dampness or mold to be associated consistently with increased asthma development and exacerbation, current and ever diagnosis of asthma, dyspnea, wheeze, cough, respiratory infections, bronchitis, allergic rhinitis, eczema, and upper respiratory tract symptoms. Associations were found in allergic and nonallergic individuals. Evidence strongly suggested causation of asthma exacerbation in children. Suggestive evidence was available for only a few specific measured microbiologic factors and was in part equivocal, suggesting both adverse and protective associations with health.

CONCLUSIONS

Evident dampness or mold had consistent positive associations with multiple allergic and respiratory effects. Measured microbiologic agents in dust had limited suggestive associations, including both positive and negative associations for some agents. Thus, prevention and remediation of indoor dampness and mold are likely to reduce health risks, but current evidence does not support measuring specific indoor microbiologic factors to guide health-protective actions.

Predictors of airborne endotoxin concentrations in inner city homes

Few studies have assessed in home factors which contribute to airborne endotoxin concentrations. In 85 inner city Baltimore homes, we found no significant correlation between settled dust and airborne endotoxin concentrations. Certain household activities and characteristics, including frequency of dusting, air conditioner use and type of flooring, explained 36-42% of the variability of airborne concentrations. Measurements of both airborne and settled dust endotoxin concentrations may be needed to fully characterize domestic exposure in epidemiologic investigations.

The Human Lung Microbiome

The human lower respiratory tract is considered sterile in normal healthy individuals (Flanagan et al., 2007; Speert, 2006) despite the fact that every day we breathe in multiple microorganisms present in the air and aspirate thousands of organisms from the mouth and nasopharynx. This apparent sterility is maintained by numerous interrelated components of the lung physical structures such as the mucociliary elevator and components of the innate and adaptive immune systems (discussed below) (reviewed in (Diamond et al., 2000; Gerritsen, 2000)). However, it is possible that the observed sterility might be a result of the laboratory practices applied to study the flora of the lungs. Historically, researchers faced with a set of diseases characterized by a changing and largely cryptic lung microbiome have lacked tools to study lung ecology as a whole and have concentrated on familiar, cultivatable candidate pathogens.

Exposure assessment in Beijing, China: biological agents, ultrafine particles, and lead

In this study, air samples were taken using a BioSampler and gelatin filters from six sites in Beijing: office, hospital, student dormitory, train station, subway, and a commercial street. Dust samples were also collected using a surface sampler from the same environments. Limulus amoebocyte lysate (LAL) and Glucatell assays were used to quantify sample endotoxin and (1,3)-β-d-glucan concentration levels, respectively. Enzyme-linked immunosorbent assay (ELISA) was used to measure the dust mite allergens (Der p 1 and Der f 1). Ultrafine particle and lead concentrations in these sampling sites were also measured using P-Trak and atomic absorption spectrometer, respectively. Analysis of variance (ANOVA) and linear regression analysis were used to analyze the concentration data. Higher culturable bacteria (12,639 CFU/m3) and fungi (1,806 CFU/m3) concentrations were observed for the train station and the subway system, respectively. For the rest of sampling sites, their concentrations were comparable to those found in western countries, ranging from 990 to 2,276 CFU/m3 for bacteria, and from 119 to 269 CFU/m3 for fungi. ANOVA analysis indicated that there were statistically significant differences between the culturable bacterial and fungal concentration levels obtained for different sites (p value=0.0001 and 0.0047). As for dust allergens, endotoxin, and (1,3)-β-D-glucan, their concentrations also seemed to be comparable to those found in the developed countries. Airborne allergen concentrations ranged from 16 to 68 ng/m3. The dust-borne allergen concentration was observed to range from 0.063 to 0.327 ng/mg. As for endotoxin, the highest airborne concentration of 25.24 ng/m3 was observed for the commercial street, and others ranged from 0.0427 to 0.1259 ng/m3. And dust-borne endotoxin concentration ranged from 58.83 to 6,427.4 ng/mg. For (1,3)-β-D-glucan, the airborne concentration ranged from 0.02 to 1.2 ng/m3. Linear regression analyses showed that there existed poor correlations between those in airborne and dust-borne states (R2=0.002~0.43). In our study, the lowest ultrafine particle concentration about 5,203 pt/cm3 was observed in office and the highest was observed at the train station, up to 32,783 pt/cm3. Lead concentration was shown to range from 80 to 170 ng/mg with the highest also observed at the train station. The information provided in this work can be used to learn the general situation of relevant health risks in Beijing. And the results here suggested that when characterizing exposure both airborne and dust-borne as well as the environments should be considered.

Visually observed mold and moldy odor versus quantitatively measured microbial exposure in homes

The main study objective was to compare different methods for assessing mold exposure in conjunction with an epidemiologic study on the development of children's asthma. Homes of 184 children were assessed for mold by visual observations and dust sampling at child's age 1 (Year 1). Similar assessment supplemented with air sampling was conducted in Year 7. Samples were analyzed for endotoxin, (1-3)-β-D-glucan, and fungal spores. The Mold Specific Quantitative Polymerase Chain Reaction assay was used to analyze 36 mold species in dust samples, and the Environmental Relative Moldiness Index (ERMI) was calculated. Homes were categorized based on three criteria: 1) visible mold damage, 2) moldy odor, and 3) ERMI. Even for homes where families had not moved, Year 7 endotoxin and (1-3)-β-d-glucan exposures were significantly higher than those in Year 1 (p<0.001), whereas no difference was seen for ERMI (p=0.78). Microbial concentrations were not consistently associated with visible mold damage categories, but were consistently higher in homes with moldy odor and in homes that had high ERMI. Low correlations between results in air and dust samples indicate different types or durations of potential microbial exposures from dust vs. air. Future analysis will indicate which, if any, of the assessment methods is associated with the development of asthma.

Residential fungal growth and incidence of acute respiratory illness during the first two years of life

BACKGROUND

Whether or not indoor mold growth causes acute childhood respiratory illness is controversial.

OBJECTIVE

To determine the influence of indoor fungus on the incidence of acute respiratory illness episodes during the first two years of life.

METHODS

Fungal indicators were measured in homes of children followed by daily symptom diaries and twice monthly telephone contact up to two years.

PARTICIPANTS

357 children born in Prince Edward Island, Canada.

RESULTS

Generally, fungal contamination was not excessive with a geometric mean mold surface area (MSA) of 1012cm(2) (geometric standard deviation (GSD) 24.2). The annual mean illness episodes per child were 6.85 (Standard Deviation (SD) 2.80). The incidence of respiratory illness episodes was not significantly related to any of the mold indicators: Analysis of variance (ANOVA) derived F-statistic (p values) was 0.14 (0.7090) for mold surface area.

CONCLUSIONS

In homes not selected by degree of fungal contamination, fungal burden was generally not excessive and was not found to be a risk factor for acute respiratory illness episodes during the first two years of life.

Temporal and spatial patterns of ambient endotoxin concentrations in Fresno, California

BACKGROUND

Endotoxins are found in indoor dust generated by human activity and pets, in soil, and adsorbed onto the surfaces of ambient combustion particles. Endotoxin concentrations have been associated with respiratory symptoms and the risk of atopy and asthma in children.

OBJECTIVE

We characterized the temporal and spatial variability of ambient endotoxin in Fresno/Clovis, California, located in California's Central Valley, to identify correlates and potential predictors of ambient endotoxin concentrations in a cohort of children with asthma [Fresno Asthmatic Children's Environment Study (FACES)].

METHODS

Between May 2001 and October 2004, daily ambient endotoxin and air pollutants were collected at the central ambient monitoring site of the California Air Resources Board in Fresno and, for shorter time periods, at 10 schools and indoors and outdoors at 84 residences in the community. Analyses were restricted to May-October, the dry months during which endotoxin concentrations are highest.

RESULTS

Daily endotoxin concentration patterns were determined mainly by meteorologic factors, particularly the degree of air stagnation. Overall concentrations were lowest in areas distant from agricultural activities. Highest concentrations were found in areas immediately downwind from agricultural/pasture land. Among three other measured air pollutants [fine particulate matter, elemental carbon (a marker of traffic in Fresno), and coarse particulate matter (PMc)], PMc was the only pollutant correlated with endotoxin. Endotoxin, however, was the most spatially variable.

CONCLUSIONS

Our data support the need to evaluate the spatial/temporal variability of endotoxin concentrations, rather than relying on a few measurements made at one location, in studies of exposure and and respiratory health effects, particularly in children with asthma and other chronic respiratory diseases.

Influence of indoor factors in dwellings on the development of childhood asthma

Asthma has become the most common, childhood chronic disease in the industrialized world, and it is also increasing in developing regions. There are huge differences in the prevalence of childhood asthma across countries and continents, and there is no doubt that the prevalence of asthma was strongly increasing during the past decades worldwide. Asthma, as a complex disease, has a broad spectrum of potential determinants ranging from genetics to life style and environmental factors. Environmental factors are likely to be important in explaining the regional differences and the overall increasing trend towards asthma's prevalence. Among the environmental conditions, indoor factors are of particular interest because people spend more than 80% of their time indoors globally. Increasing prices for oil, gas and other sources of primary energy will further lead to better insulation of homes, and ultimately to reduced energy costs. This will decrease air exchange rates and will lower the dilution of indoor air mass with ambient air. Indoor air quality and potential health effects will therefore be an area for future research and for gaining a better understanding of asthma epidemics. This strategic review will summarize the current knowledge of the effects of a broad spectrum of indoor factors on the development of asthma in childhood in Western countries based on epidemiological studies. In conclusion, several epidemiological studies point out, that indoor factors might cause asthma in childhood. Stronger and more consistent findings are seen when exposure to these indoor factors is assessed by surrogates for the source of the actual toxicants. Measurement-based exposure assessments for several indoor factors are less common than using surrogates of the exposure. These studies, however, mainly showed heterogeneous results. The most consistent finding for an induction of asthma in childhood is related to exposure to environmental tobacco smoke, to living in homes close to busy roads, and in damp homes where are visible moulds at home. The causing agents of the increased risk of living in damp homes remained uncertain and needs clarification. Exposure to pet-derived allergens and house dust mites are very commonly investigated and thought to be related to asthma onset. The epidemiological evidence is not sufficient to recommend avoidance measures against pet and dust mites as preventive activities against allergies. More research is also needed to clarify the potential risk for exposure to volatile and semi-volatile organic compounds due to renovation activities, phthalates and chlorine chemicals due to cleaning.

Do questions reflecting indoor air pollutant exposure from a questionnaire predict direct measure of exposure in owner-occupied houses?

Home characteristic questions are used in epidemiological studies and clinical settings to assess potentially harmful exposures in the home. The objective of this study was to determine whether questionnaire-reported home characteristics can predict directly measured pollutants. Sixty home inspections were conducted on a subsample of the 2006 population-based Toronto Child Health Evaluation Questionnaire. Indoor/outdoor air and settled dust samples were analyzed. Mean Fel d 1 was higher (p < 0.0001) in homes with a cat (450.58 μg/g) versus without (22.28 μg/g). Mean indoor NO(2) was higher (p = 0.003) in homes with gas stoves (14.98 ppb) versus without (8.31 ppb). Self-reported musty odours predicted higher glucan levels (10554.37 μg/g versus 6308.58 μg/g, p = 0.0077). Der f 1 was predicted by the home's age, but not by reports of carpets, and was higher in homes with mean relative humidity > 50% (61.30 μg/g, versus 6.24 μg/g, p = 0.002). Self-reported presence of a cat, a gas stove, musty odours, mice, and the home's age and indoor relative humidity over 50% predicted measured indoor levels of cat allergens, NO(2), fungal glucan, mouse allergens and dust mite allergens, respectively. These results are helpful for understanding the significance of indoor exposures ascertained by self-reporting in large epidemiological studies and also in the clinical setting.

Airborne endotoxin concentrations in homes burning biomass fuel

BACKGROUND

About half of the world's population is exposed to smoke from burning biomass fuels at home. The high airborne particulate levels in these homes and the health burden of exposure to this smoke are well described. Burning unprocessed biological material such as wood and dried animal dung may also produce high indoor endotoxin concentrations.

OBJECTIVE

In this study we measured airborne endotoxin levels in homes burning different biomass fuels.

METHODS

Air sampling was carried out in homes burning wood or dried animal dung in Nepal (n = 31) and wood, charcoal, or crop residues in Malawi (n = 38). Filters were analyzed for endotoxin content expressed as airborne endotoxin concentration and endotoxin per mass of airborne particulate.

RESULTS

Airborne endotoxin concentrations were high. Averaged over 24 hr in Malawian homes, median concentrations of total inhalable endotoxin were 24 endotoxin units (EU)/m(3) in charcoal-burning homes and 40 EU/m(3) in wood-burning homes. Short cooking-time samples collected in Nepal produced median values of 43 EU/m(3) in wood-burning homes and 365 EU/m(3) in dung-burning homes, suggesting increasing endotoxin levels with decreasing energy levels in unprocessed solid fuels.

CONCLUSIONS

Airborne endotoxin concentrations in homes burning biomass fuels are orders of magnitude higher than those found in homes in developed countries where endotoxin exposure has been linked to respiratory illness in children. There is a need for work to identify the determinants of these high concentrations, interventions to reduce exposure, and health studies to examine the effects of these sustained, near-occupational levels of exposure experienced from early life.

Epidemiology of asthma: risk factors for development

This comprehensive review of the recent literature was undertaken to determine the current state of knowledge of the risk factors involved in the development of asthma in order to focus investigations in a proposed new longitudinal birth cohort study. The origins of asthma appear to lie in the prenatal and early postnatal period, and renewed investigations in this period with long-term close follow-up and objective phenotypic characterization will help to unravel the role of the multiple putative environmental factors in the development of asthma. It is only after understanding these effects that one can hope to design rational prevention studies for asthma.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Asthma and respiratory symptoms in hospital workers related to dampness and biological contaminants

The National Institute for Occupational Safety and Health investigated respiratory symptoms and asthma in relation to damp indoor environments in employees of two hospitals. A cluster of six work-related asthma cases from one hospital department, whose symptoms arose during a time of significant water incursions, led us to conduct a survey of respiratory health in 1171/1834 employees working in the sentinel cases hospital and a nearby hospital without known indoor environmental concerns. We carried out observational assessment of dampness, air, chair, and floor dust sampling for biological contaminants, and investigation of exposure-response associations for about 500 participants. Many participants with post-hire onset asthma reported diagnosis dates in a period of water incursions and renovations. Post-hire asthma and work-related lower respiratory symptoms were positively associated with the dampness score. Work-related lower respiratory symptoms showed monotonically increasing odds ratios with ergosterol, a marker of fungal biomass. Other fungal and bacterial indices, particle counts, cat allergen and latex allergen were associated with respiratory symptoms. Our data imply new-onset of asthma in relation to water damage, and indicate that work-related respiratory symptoms in hospital workers may be associated with diverse biological contaminants.

PRACTICAL IMPLICATIONS

In healthcare facilities with indoor dampness and microbial contamination, possible associations between such conditions and respiratory health effects should be considered. Good building maintenance and housekeeping procedures should lead to improvements in employee respiratory health.

Indoor airborne endotoxin assessment in homes of Paris newborn babies

The aims of this study were first to assess airborne endotoxin levels in the dwellings of 162 newborns living in Paris twice during a 1-year period, and second, to identify predictors for endotoxin concentrations using questionnaire data in relation to housing factors and living conditions. Air samples were collected on a glass fiber filter in polystyrene filter holders, using a pump at a flow rate of 3.5 l/min for 24 h placed in the main room of the home. Endotoxin levels were measured using a chromogenic kinetic Limulus Amoebocyte Lysate test. Geometric means (geometric standard deviation) of airborne endotoxin levels at two different visits were respectively 0.509 (4.289) EU/m3 and 0.557 (3.029) EU/m3. Airborne endotoxin levels were significantly increased: (i) in cold season (P = 0.024), with (ii) the presence of visible cockroaches in the previous 12 months at home (P < 0.001), (iii) increased number of inhabitants per square meter (P = 0.012), (iv) the high frequency of cleaning with the floor cloths (P = 0.0014), and (v) the low frequency of vacuuming (P = 0.0045). This study provided for the first time airborne endotoxin levels issued from repeated measurements in Paris dwellings. PRACTICAL IMPLICATIONS This analysis contributed to identify a few factors that determined indoor airborne endotoxin levels. However, the predictive model including housing factors and living conditions poorly estimated endotoxin levels. Consequently, multiple samples and longer sampling periods might improve the estimate of long-term airborne endotoxin exposure especially its variability, in cohort studies.

Quality of indoor residential air and health

About 90% of our time is spent indoors where we are exposed to chemical and biological contaminants and possibly to carcinogens. These agents may influence the risk of developing nonspecific respiratory and neurologic symptoms, allergies, asthma and lung cancer. We review the sources, health effects and control strategies for several of these agents. There are conflicting data about indoor allergens. Early exposure may increase or may decrease the risk of future sensitization. Reports of indoor moulds or dampness or both are consistently associated with increased respiratory symptoms but causality has not been established. After cigarette smoking, exposure to environmental tobacco smoke and radon are the most common causes of lung cancer. Homeowners can improve the air quality in their homes, often with relatively simple measures, which should provide health benefits.