Impact of residential nitrogen dioxide exposure on personal exposure: an international study

Indoor ozone: Concentrations and influencing factors

Because people spend most of their time indoors, much of their exposure to ozone occurs in buildings, which are partially protective against outdoor ozone. Measurements in approximately 2000 indoor environments (residences, schools, and offices) show a central tendency for average indoor ozone concentration of 4-6 ppb and an indoor to outdoor concentration ratio of about 25%. Considerable variability in this ratio exists among buildings, as influenced by seven building-associated factors: ozone removal in mechanical ventilation systems, ozone penetration through the building envelope, air-change rates, ozone loss rate on fixed indoor surfaces, ozone loss rate on human occupants, ozone loss by homogeneous reaction with nitrogen oxides, and ozone loss by reaction with gas-phase organics. Among these, the most important are air-change rates, ozone loss rate on fixed indoor surfaces, and, in densely occupied spaces, ozone loss rate on human occupants. Although most indoor ozone originates outdoors and enters with ventilation air, indoor emission sources can materially increase indoor ozone concentrations. Mitigation technologies to reduce indoor ozone concentrations are available or are being investigated. The most mature of these technologies, activated carbon filtration of mechanical ventilation supply air, shows a high modeled health-benefit to cost ratio when applied in densely occupied spaces.

Adsorption Kinetics of NO2 Gas on Pt/Cr-TiO2/Pt-Based Sensors

Metal oxides are excellent candidates for the detection of various gases; however, the issues such as the limited operating temperature and selectivity are the most important ones requiring the comprehensive understanding of gas adsorption kinetics on the sensing layer surfaces. To this context, the present study focuses mainly on the fabrication of a Pt/Cr-TiO2/Pt type sensor structure that is highly suitable in reducing the operating temperature (from 400 to 200 °C), extending the lower limit NO2 gas concentration (below 10 ppm) with fast response (37 s) and recovery (24 s) times. This illustrates that the sensor performance is not only solely dependent on the nature of sensing material, but also, it is significantly enhanced by using such a new kind of electrode geometry. Moreover, Cr doping into TiO2 culminates in altering the sensor response from n- to p-type and thus contributes to sensor performance enhancement by detecting low NO2 concentrations selectively at reduced operating temperatures. In addition, the NO2 surface adsorption kinetics are studied by fitting the obtained sensor response curves with Elovich, inter-particle diffusion, and pseudo first-order and pseudo second-order adsorption models. It is found that a pseudo first-order reaction model describes the best NO2 adsorption kinetics toward 7–170 ppm NO2 gas at 200 °C. Finally, the sensing mechanism is discussed on the basis of the obtained results.

Modeling residential indoor concentrations of PM2.5 , NO2 , NOx , and secondhand smoke in the Subpopulations and Intermediate Outcome Measures in COPD (SPIROMICS) Air study

Increased outdoor concentrations of fine particulate matter (PM_2.5 ) and oxides of nitrogen (NO₂ , NO_x ) are associated with respiratory and cardiovascular morbidity in adults and children. However, people spend most of their time indoors and this is particularly true for individuals with chronic obstructive pulmonary disease (COPD). Both outdoor and indoor air pollution may accelerate lung function loss in individuals with COPD, but it is not feasible to measure indoor pollutant concentrations in all participants in large cohort studies. We aimed to understand indoor exposures in a cohort of adults (SPIROMICS Air, the SubPopulations and Intermediate Outcome Measures in COPD Study of Air pollution). We developed models for the entire cohort based on monitoring in a subset of homes, to predict mean 2-week-measured concentrations of PM_2.5 , NO₂ , NO_x , and nicotine, using home and behavioral questionnaire responses available in the full cohort. Models incorporating socioeconomic, meteorological, behavioral, and residential information together explained about 60% of the variation in indoor concentration of each pollutant. Cross-validated R² for best indoor prediction models ranged from 0.43 (NO_x ) to 0.51 (NO₂ ). Models based on questionnaire responses and estimated outdoor concentrations successfully explained most variation in indoor PM_2.5 , NO₂ , NO_x , and nicotine concentrations.

Multizone airflow and pollution simulations of indoor emission sources

A health impact assessment of the indoor pollution was performed for various indoor sources: oven for heating, cooking, photocopy machine and smoke cigarettes. The mortality levels and hospital admissions associated with exposure to PM2.5 and NO₂ concentrations have been calculated. We have modelled a two level house in Madrid city center where the office and the living floors are in the same building. The people follow a predefined activity patterns (time profiles) in the outdoor and indoor environments. In this experiment, we have performed a full year simulation using the EnergyPlus model to obtain the following parameters: building energy use, thermal behavior, airflow and indoor air quality simultaneously. Outdoor air quality and meteorological conditions were provided by the output of running the very well-known model WRF/Chem. The health impacts of the indoor emitting sources are higher in the warm months due to the operation of the air conditioning system. The largest impact on health is produced by the emissions that are released during cooking. The results also show a high correlation between indoor and outdoor concentrations when indoor emissions are not considered.

A Simple Technique Based on Digital Images for Determination of Nitrogen Dioxide in Ambient Air

The lockdown to prevent the coronavirus spread resulted in an immediate reduction in gas concentration worldwide. This fact shows the importance of nitrogen dioxide as a pollutant gas directly associated with human activities. For indoor exposure, NO₂ has been associated with effects on the respiratory system. In outdoor environments, ozone reaches a maximum after NO₂ peaks, and acid rain arises with NO₂ oxidation to forms nitric acid. Therefore, monitoring the NO₂ concentration in atmospheric air can help prevent respiratory diseases and lower the concentration of other atmospheric pollutants. The experiment proposed in this article uses a low-cost passive sampler for the NO₂ collection. An innovative and straightforward technique to determine the gas concentration through a gel-dyed formation and based on digital image analysis RGB colors channel are split by the software ImageJ. Results of digital image analysis and spectrophotometry were statistically agreed at a 95% confidence level. The advantages of the technique include low cost, the ready availability of components, ease of use, and sensitivity. The achievable resolution of nitrogen dioxide concentrations is 9 ppb for 24-h sampling.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11270-021-05031-4.

Nitrogen dioxide exposures from LPG stoves in a cleaner-cooking intervention trial

BACKGROUND

Liquefied petroleum gas (LPG) stoves have been promoted in low- and middle-income countries (LMICs) as a clean energy alternative to biomass burning cookstoves.

OBJECTIVE

We sought to characterize kitchen area concentrations and personal exposures to nitrogen dioxide (NO₂) within a randomized controlled trial in the Peruvian Andes. The intervention included the provision of an LPG stove and continuous fuel distribution with behavioral messaging to maximize compliance.

METHODS

We measured 48-hour kitchen area NO₂ concentrations at high temporal resolution in homes of 50 intervention participants and 50 control participants longitudinally within a biomass-to-LPG intervention trial. We also collected 48-hour mean personal exposures to NO₂ among a subsample of 16 intervention and 9 control participants. We monitored LPG and biomass stove use continuously throughout the trial.

RESULTS

In 367 post-intervention 24-hour kitchen area samples of 96 participants' homes, geometric mean (GM) highest hourly NO₂ concentration was 138 ppb (geometric standard deviation [GSD] 2.1) in the LPG intervention group and 450 ppb (GSD 3.1) in the biomass control group. Post-intervention 24-hour mean NO₂ concentrations were a GM of 43 ppb (GSD 1.7) in the intervention group and 77 ppb (GSD 2.0) in the control group. Kitchen area NO₂ concentrations exceeded the WHO indoor hourly guideline an average of 1.3 h per day among LPG intervention participants. GM 48-hour personal exposure to NO₂ was 5 ppb (GSD 2.4) among 35 48-hour samples of 16 participants in the intervention group and 16 ppb (GSD 2.3) among 21 samples of 9 participants in the control group.

DISCUSSION

In a biomass-to-LPG intervention trial in Peru, kitchen area NO₂ concentrations were substantially lower within the LPG intervention group compared to the biomass-using control group. However, within the LPG intervention group, 69% of 24-hour kitchen area samples exceeded WHO indoor annual guidelines and 47% of samples exceeded WHO indoor hourly guidelines. Forty-eight-hour NO₂ personal exposure was below WHO indoor annual guidelines for most participants in the LPG intervention group, and we did not measure personal exposure at high temporal resolution to assess exposure to cooking-related indoor concentration peaks. Further research is warranted to understand the potential health risks of LPG-related NO₂ emissions and inform current campaigns which promote LPG as a clean-cooking option.

Prenatal exposure to VOCs and NOx and lung function in preschoolers

BACKGROUND

Several studies have shown that exposure to air pollutants affects lung growth and development and can result in poor respiratory health in early life.

METHODS

We included a subsample of 772 Mexican preschoolers whose mothers participated in a Prenatal Omega-3 fatty acid Supplements, GRowth, And Development birth cohort study with the aim to evaluate the impact of prenatal exposure to volatile organic compounds and nitrogen oxides on lung function measured by oscillation tests. The preschoolers were followed until 5 years of age. Anthropometric measurements and forced oscillation tests were performed at 36, 48, and 60 months of age. Information on sociodemographic and health characteristics was obtained during follow up. Prenatal exposure to volatile organic compounds and nitrogen oxides was evaluated using a land use regression models and the association between them was tested using a lineal regression and longitudinal linear mixed effect models adjusting for potential confounders.

RESULTS

Overall, the mean (standard deviation) of the measurements of respiratory system resistance and respiratory system reactance at 6, 8, and 10 Hz during the follow-up period was 11.3 (2.4), 11.1 (2.4), 10.3 (2.2) and -5.2 (1.6), -4.8 (1.7), and -4.6 hPa s L^-1 (1.6), respectively. We found a significantly positive association between respiratory resistance (β_Rrs6  = 0.011; 95%CI: 0.001, 0.023) (P < .05) and prenatal exposure to nitrogen dioxide and a marginally negatively association between respiratory reactance (β_Xrs6  = -11.40 95%CI: -25.26, 1.17 and β_Xrs8  = -11.91 95%CI: -26.51, 1.43) (P = .07) and prenatal exposure to xylene.

CONCLUSION

Prenatal exposure to air pollutants was significantly associated with the alteration of lung function measured by oscillation tests in these preschool children.

Concurrently Measured Concentrations of Atmospheric Mercury in Indoor (household) and Outdoor Air of Basel, Switzerland

Indoor air pollution can be a major health risk because urban populations spend up to 90% of their time in closed rooms. Gaseous elemental mercury (GEM) has not been measured as routinely as other indoor air pollutants due to the high costs and limited mobility of active Hg analyzers. However, household GEM concentrations may exceed Hg air quality guidelines as a result of potential indoor GEM sources like broken Hg thermometers. Here we deploy novel low-cost mercury passive air samplers (MerPAS) in 27 households (7 days) and at 14 outdoor locations (29-31 days) in Basel, Switzerland. Average Hg concentrations ranged from 2.0 to 10.8 ng m^-3 indoors and from 1.8 to 2.5 ng m^-3 outdoors. These results reveal that households are a net source of Hg to the urban atmosphere and exceed outdoor Hg levels by a factor of 2 on average. We estimated an average weekly intake rate of 0.01 μg of Hg/kg of body weight for adult residents in Basel, which is usually lower than Hg exposure of people with dental amalgam fillings. Our campaign demonstrates that air monitoring programs can easily be complemented by straightforward Hg measurements using MerPAS.

A hybrid kriging/land-use regression model with Asian culture-specific sources to assess NO2 spatial-temporal variations

Kriging interpolation and land use regression (LUR) have characterized the spatial variability of long-term nitrogen dioxide (NO₂), but there has been little research on combining these two methods to capture small-scale spatial variation. Furthermore, studies predicting NO₂ exposure are almost exclusively based on traffic-related variables, which may not be transferable to Taiwan, a typical Asian country with diverse local emission sources, where densely distributed temples and restaurants may be important for NO₂ levels. To advance the exposure estimates in Taiwan, a hybrid kriging/LUR model incorporates culture-specific sources as potential predictors. Based on 14-year NO₂ observations from 73 monitoring stations across Taiwan, a set of interpolated NO₂ values were generated through a leave-one-out ordinary kriging algorithm, and this was included as an explanatory variable in the stepwise LUR procedures. Kriging interpolated NO₂ and culture-specific predictors were entered in the final models, which captured 90% and 87% of NO₂ variation in annual and monthly resolution, respectively. Results from 10-fold cross-validation and external data verification demonstrate robust performance of the developed models. This study demonstrates the value of incorporating the kriging-interpolated estimates and culture-specific emission sources into the traditional LUR model structure for predicting NO₂, which can be particularly useful for Asian countries.

Characterization of Indoor Air Quality on a College Campus: A Pilot Study

Recent construction trends on college campuses have demonstrated a shift to designing buildings with features focused on sustainability. However, few studies have investigated indoor air quality in institutions of higher education, particularly in sustainably designed buildings. The objective of this study was to evaluate the association of building and occupancy on indoor air quality within and between higher education buildings. We measured particulate matter, formaldehyde, carbon dioxide, and nitrogen oxides in LEED certified, retrofitted, and conventional building types on a college campus. Three size fractions of particulate matter were measured in each building. We conducted multi-zonal, 48-h measurements when the buildings were occupied and unoccupied. Outdoor particulate matter was significantly higher (PM2.5 = 4.76, PM4 = 17.1, and PM100 = 21.6 µg/m³) than in classrooms (PM2.5 = 1.7, PM4 = 4.2, and PM100 = 6.7 µg/m³) and common areas (PM2.5 = 1.3, PM4 = 4.2, and PM100 = 4.8 µg/m³; all p < 0.001). Additionally, concentrations of carbon dioxide and particulate matter were significantly higher (p < 0.05) during occupied sampling. The results suggest that occupancy status and building zone are major predictors of indoor air quality in campus buildings, which can, in turn, increase the concentration of contaminants, potentially impacting occupant health and performance. More research is warranted to reveal building features and human behaviors contributing to indoor exposures.

Community Noise and Air Pollution Exposure During the Development of a Multi-Well Oil and Gas Pad

Unconventional oil and gas development (UOGD) in the United States is increasingly being conducted on multiwell pads (MWPs) and in residential areas. We measured air pollution, noise, and truck traffic during four distinct phases of UOGD: drilling, hydraulic fracturing, flowback, and production. We monitored particulate matter (PM_2.5), black carbon (BC), A-weighted (dBA), and C-weighted (dBC) noise using real-time instruments on 1 and 5 min time scales, and truck traffic for 4-7 days per phase at a large 22-well pad sited in a residential area of Weld County, Colorado. Hydraulic fracturing, which requires frequent truck trips to move supplies and diesel engines to power the process, had the highest median air pollution levels of PM_2.5 and BC and experienced the greatest number of heavy trucks per hour compared to other phases. Median air pollution was lowest during drilling at this MWP, possibly because an electric drill rig was used. The equivalent continuous noise level ( L_eq) exceeded guidelines of 50 dBA and 65 dBC for A-weighted and C-weighted noise, respectively, during all development phases. Our data show that these multiple stressors are present around the clock at these sites, and this work provides baseline measurements on likely human exposure levels near similarly sized MWPs.

Prenatal Exposure to Nitrogen Oxides and its Association with Birth Weight in a Cohort of Mexican Newborns from Morelos, Mexico

Background

The Child-Mother binomial is potentially susceptible to the toxic effects of pollutants because some chemicals interfere with placental transfer of nutrients, thus affecting fetal development, and create an increased the risk of low birth weight, prematurity and intrauterine growth restriction.

Objective

To evaluate the impact of prenatal exposure to nitrogen oxides (NO_x) on birth weight in a cohort of Mexican newborns.

Methodology

We included 745 mother-child pair participants of the POSGRAD cohort study. Information on socio-demographic characteristics, obstetric history, health history and environmental exposure during pregnancy were readily available and the newborns’ anthropometric measurements were obtained at delivery. Prenatal NO_x exposure assessment was evaluated using a Land-Use Regression predictive models considering local monitoring from 60 sites on the State of Morelos. The association between prenatal exposure to NO_x and birth weight was estimated using a multivariate linear regression models.

Results

The average birth weight was 3217 ± 439 g and the mean of NO_x concentration was 21 ppb (Interquartile range, IQR = 6.95 ppb). After adjusting for maternal age and other confounders, a significant birthweight reduction was observed for each IQR of NO_x increase (ß = –39.61 g, 95% CI: –77.00; –2.21; p = 0.04).

Conclusions

Our results provides evidence that prenatal NO_x exposure has a negative effect on birth weight, which may influence the growth and future development of the newborn.

24-h Nitrogen dioxide concentration is associated with cooking behaviors and an increase in rescue medication use in children with asthma

Exposure to nitrogen dioxide (NO₂), a byproduct of combustion, is associated with poor asthma control in children. We sought to determine whether gas-fueled kitchen appliance use is associated with 24-h indoor NO₂ concentrations and whether these concentrations are associated with asthma morbidity in children. Children aged 5-12 years old with asthma were eligible. Mean 24-h NO₂ concentration was measured in the kitchen over a four-day sampling period and gas stove use was captured in time activity diaries. The relationship between stove and oven use and daily NO₂ concentration was analyzed. Longitudinal analysis assessed the effect of daily NO₂ exposure on symptoms, inhaler use, and lung function. Multivariate models were adjusted for age, sex, season, and maternal education. Thirty children contributed 126 participant days of sampling. Mean indoor 24-h NO₂ concentration was 58(48)ppb with a median (range) of 45(12-276)ppb. All homes had gas stoves and furnaces. Each hour of kitchen appliance use was associated with an 18ppb increase in 24-h NO₂ concentration. In longitudinal multivariate analysis, each ten-fold increase in previous-day NO₂ was associated with increased nighttime inhaler use (OR = 4.9, p = 0.04). There were no associations between NO₂ and lung function or asthma symptoms. Higher previous-day 24-h concentration of NO₂ is associated with increased nighttime inhaler use in children with asthma.

Exhaust ventilation in attached garages improves residential indoor air quality

Previous research has shown that indoor benzene levels in homes with attached garages are higher than homes without attached garages. Exhaust ventilation in attached garages is one possible intervention to reduce these concentrations. To evaluate the effectiveness of this intervention, a randomized crossover study was conducted in 33 Ottawa homes in winter 2014. VOCs including benzene, toluene, ethylbenzene, and xylenes, nitrogen dioxide, carbon monoxide, and air exchange rates were measured over four 48-hour periods when a garage exhaust fan was turned on or off. A blower door test conducted in each garage was used to determine the required exhaust fan flow rate to provide a depressurization of 5 Pa in each garage relative to the home. When corrected for ambient concentrations, the fan decreased geometric mean indoor benzene concentrations from 1.04 to 0.40 μg/m³ , or by 62% (P<.05). The garage exhaust fan also significantly reduced outdoor-corrected geometric mean indoor concentrations of other pollutants, including toluene (53%), ethylbenzene (47%), m,p-xylene (45%), o-xylene (43%), and carbon monoxide (23%) (P<.05) while having no impact on the home air exchange rate. This study provides evidence that mechanical exhaust ventilation in attached garages can reduce indoor concentrations of pollutants originating from within attached garages.

Air pollution and unintentional injury deaths in South Korea

This study aimed to assess the association between exposure to air pollution and unintentional injury deaths in South Korea. Data regarding all unintentional injury deaths (17,566) in seven metropolitan cities from 2002 to 2008 were collected. Using a time-stratified case-crossover study, conditional logistic regression and subgroup analyses were performed after stratification by age, gender, and season. To evaluate immediate and delayed effects of air pollutants, we used both single lag and distributed lag models. The risk was expressed as an odds ratio (OR) per one interquartile range (IQR) of each air pollutant. During the study period, the median (IQR) levels of air pollutants were 0.005 (0.004-0.007) ppm for sulfur dioxide (SO₂), 0.02 (0.02-0.03) ppm for nitrogen dioxide (NO₂), 0.03 (0.02-0.04) ppm for ozone (O₃), 48.3 (34.9-67.0) μg/m(3) for particulate matter ≤10 μm in aerodynamic diameter (PM₁₀), and 0.36 (0.1-0.6) ppm for carbon monoxide (CO). All air pollutants, with the exception of PM₁₀ and O₃, were significantly associated with an increased risk of unintentional injury deaths; the maximum risk was observed in the distributed lag 1 model for SO₂ (OR, 1.119; 95% confidence interval, 1.022-1.226), NO₂ (1.208; 1.043-1.400), and CO (1.012; 1.000-1.024). After stratification of the subjects by age, SO₂, NO₂, and CO were significantly associated with increased risk of unintentional injury deaths among subjects aged 60 years or older in the distributed lag 1 model, while O₃ and PM₁₀ were associated with increased risk among subjects aged 40 to 59 years. However, in subjects younger than 40 years of age, we found no significant associations for any of the air pollutants. Our study suggested evidence for a short-term association between air pollutants and unintentional injury deaths, even at low pollutants levels.

A cross-sectional study of the association between ventilation of gas stoves and chronic respiratory illness in U.S. children enrolled in NHANESIII

BACKGROUND

Gas stoves emit pollutants that are respiratory irritants. U.S. children under age 6 who live in homes where gas stoves are used for cooking or heating have an increased risk of asthma, wheeze and reduced lung function. Yet few studies have examined whether using ventilation when operating gas stoves is associated with a decrease in the prevalence of respiratory illnesses in this population.

METHODS

The Third National Health and Nutrition Examination Survey was used to identify U.S. children aged 2-16 years with information on respiratory outcomes (asthma, wheeze, and bronchitis) who lived in homes where gas stoves were used in the previous 12 months and whose parents provided information on ventilation. Logistic regression models evaluated the association between prevalent respiratory outcomes and ventilation in homes that used gas stoves for cooking and/or heating. Linear regression models assessed the association between spirometry measurements and ventilation use in children aged 8-16 years.

RESULTS

The adjusted odds of asthma (Odds Ratio [OR] = 0.64; 95% confidence intervals [CI]: 0.43, 0.97), wheeze (OR = 0.60, 95% CI: 0.42, 0.86), and bronchitis (OR = 0.60, 95% CI: 0.37, 0.95) were lower among children whose parents reported using ventilation compared to children whose parents reported not using ventilation when operating gas stoves. One-second forced expiratory volume (FEV1) and FEV1/FVC ratio was also higher in girls who lived in households that used gas stoves with ventilation compared to households that used gas stoves without ventilation.

CONCLUSIONS

In homes that used gas stoves, children whose parents reported using ventilation when operating their stove had higher lung function and lower odds of asthma, wheeze, and bronchitis compared to homes that never used ventilation or did not have ventilation available after adjusting for other risk factors. Additional research on the efficacy of ventilation as an intervention for ameliorating respiratory symptoms in children with asthma is warranted.

A Continuous Flow System for the Measurement of Ambient Nitrogen Oxides [NO + NO2] Using Rhodamine B Hydrazide as a Chemosensor

A new chemosensor has been used to monitor atmospheric nitrogen oxides [NO + NO₂] at parts per billion (ppb) level. It is based on the catalytic reaction of nitrogen oxides with rhodamine B hydrazide (RBH) to produce a colored compound through the hydrolysis of the amide bond of the molecule. A simple colorimeter has been used to monitor atmospheric nitrogen dioxide at ppb level. The air samples were purged through a sampling cuvette containing RBH solution using peristaltic pump. The proposed method has been successfully applied to monitor the ambient nitrogen dioxide levels at traffic junction points within the city limits and the results obtained are compared with the standard Griess-Ilosvay method.

Personal exposure of primary school children to BTEX, NO₂ and ozone in Eskişehir, Turkey: relationship with indoor/outdoor concentrations and risk assessment

Personal exposures of 65 primary school children to benzene, toluene, ethyl benzene, xylenes (BTEX), nitrogen dioxide (NO2) and ozone (O3) were measured during 24h by using organic vapor monitors and tailor-made passive samplers. Two schools were selected to represent students living in more polluted (urban) and less polluted (sub-urban) areas in the city of Eskişehir, Turkey. The pollutant concentrations were also measured in indoor and outdoor environments during the personal sampling to investigate the contribution of each micro-environment on measured personal concentrations. Socio-demographic and personal time-activity data were collected by means of questionnaires and half-hour-time resolution activity diaries. Personal exposure concentrations were found to be correlated with indoor home concentrations. Personal, indoor and outdoor concentrations of all studied pollutants except for ozone were found to be higher for the students living at the urban traffic site. Ozone, on the other hand, had higher concentrations at the sub-urban site for all three types of measurements (personal, indoor and outdoor). Analysis of the questionnaire data pointed out to environmental tobacco smoke, use of solvent based products, and petrol station nearby as factors that affect personal exposure concentrations. Cancer and non-cancer risks were estimated using the personal exposure concentrations. The mean cancer risk for the urban school children (1.7×10(-5)) was found to be higher than the sub-urban school children (0.88×10(-5)). Children living with smoking parents had higher risk levels (1.7×10(-5)) than children living with non-smoking parents (1.08×10(-5)). Overall, the risk levels were <1×10(-4). All hazard quotient values for BTEX for the non-cancer health effects were <1 based on the calculations EPA's Risk Assessment Guidance for Superfund (RAGS) part F.

A simulation model of building intervention impacts on indoor environmental quality, pediatric asthma, and costs

BACKGROUND

Although indoor environmental conditions can affect pediatric asthmatic patients, few studies have characterized the effect of building interventions on asthma-related outcomes. Simulation models can evaluate such complex systems but have not been applied in this context.

OBJECTIVE

We sought to evaluate the impact of building interventions on indoor environmental quality and pediatric asthma health care use, and to conduct cost comparisons between intervention and health care costs and energy savings.

METHODS

We applied our previously developed discrete event simulation model (DEM) to simulate the effect of environmental factors, medication compliance, seasonality, and medical history on (1) pollutant concentrations indoors and (2) asthma outcomes in low-income multifamily housing. We estimated health care use and costs at baseline and subsequent to interventions, and then compared health care costs with energy savings and intervention costs.

RESULTS

Interventions, such as integrated pest management and repairing kitchen exhaust fans, led to 7% to 12% reductions in serious asthma events with 1- to 3-year payback periods. Weatherization efforts targeted solely toward tightening a building envelope led to 20% more serious asthma events, but bundling with repairing kitchen exhaust fans and eliminating indoor sources (eg, gas stoves or smokers) mitigated this effect.

CONCLUSION

Our pediatric asthma model provides a tool to prioritize individual and bundled building interventions based on their effects on health and costs, highlighting the tradeoffs between weatherization, indoor air quality, and health. Our work bridges the gap between clinical and environmental health sciences by increasing physicians' understanding of the effect that home environmental changes can have on their patients' asthma.

Contribution of indoor and outdoor nitrogen dioxide to indoor air quality of wayside shops

Indoor nitrogen dioxide (NO₂) concentration is an important factor for personal exposure despite the wide distribution of its sources. Exposure to NO₂ may produce adverse health effects. The aims of this study were to characterize the indoor air quality of wayside shops using multiple NO₂ measurements, and to estimate the contribution of outdoor NO₂ sources such as vehicle emission to indoor air quality. Daily indoor and outdoor NO₂ concentrations were measured for 21 consecutive days in wayside shops (5 convenience stores, 5 coffee shops, and 5 restaurants). Contributions of outdoor NO₂ sources to indoor air quality were calculated with penetration factors and source strength factors by indoor mass balance model in winter and summer, respectively. Most wayside shops had significant differences in indoor and outdoor NO₂ concentrations both in winter and in summer. Indoor NO₂ concentrations in restaurants were twice more than those in convenience stores and coffee shops in winter. While outdoor NO₂ contributions in indoor convenience stores and coffee shops were dominant, indoor NO₂ contributions were dominant in restaurants. These could be explained that indoor NO₂ sources such as gas range and smoking mainly affect indoor concentrations comparing to outdoor sources such as vehicle emission. The indoor mass balance model by multiple measurements suggests that quantitative contribution of outdoor air on indoor air quality might be estimated without measurements of ventilation, indoor generation and decay rate.

The effects of indoor environmental exposures on pediatric asthma: a discrete event simulation model

BACKGROUND

In the United States, asthma is the most common chronic disease of childhood across all socioeconomic classes and is the most frequent cause of hospitalization among children. Asthma exacerbations have been associated with exposure to residential indoor environmental stressors such as allergens and air pollutants as well as numerous additional factors. Simulation modeling is a valuable tool that can be used to evaluate interventions for complex multifactorial diseases such as asthma but in spite of its flexibility and applicability, modeling applications in either environmental exposures or asthma have been limited to date.

METHODS

We designed a discrete event simulation model to study the effect of environmental factors on asthma exacerbations in school-age children living in low-income multi-family housing. Model outcomes include asthma symptoms, medication use, hospitalizations, and emergency room visits. Environmental factors were linked to percent predicted forced expiratory volume in 1 second (FEV1%), which in turn was linked to risk equations for each outcome. Exposures affecting FEV1% included indoor and outdoor sources of NO2 and PM2.5, cockroach allergen, and dampness as a proxy for mold.

RESULTS

Model design parameters and equations are described in detail. We evaluated the model by simulating 50,000 children over 10 years and showed that pollutant concentrations and health outcome rates are comparable to values reported in the literature. In an application example, we simulated what would happen if the kitchen and bathroom exhaust fans were improved for the entire cohort, and showed reductions in pollutant concentrations and healthcare utilization rates.

CONCLUSIONS

We describe the design and evaluation of a discrete event simulation model of pediatric asthma for children living in low-income multi-family housing. Our model simulates the effect of environmental factors (combustion pollutants and allergens), medication compliance, seasonality, and medical history on asthma outcomes (symptom-days, medication use, hospitalizations, and emergency room visits). The model can be used to evaluate building interventions and green building construction practices on pollutant concentrations, energy savings, and asthma healthcare utilization costs, and demonstrates the value of a simulation approach for studying complex diseases such as asthma.

Individual exposure to NO2 in relation to spatial and temporal exposure indices in Stockholm, Sweden: the INDEX study

Epidemiology studies of health effects from air pollution, as well as impact assessments, typically rely on ambient monitoring data or modelled residential levels. The relationship between these and personal exposure is not clear. To investigate personal exposure to NO(2) and its relationship with other exposure metrics and time-activity patterns in a randomly selected sample of healthy working adults (20-59 years) living and working in Stockholm. Personal exposure to NO(2) was measured with diffusive samplers in sample of 247 individuals. The 7-day average personal exposure was 14.3 µg/m(3) and 12.5 µg/m(3) for the study population and the inhabitants of Stockholm County, respectively. The personal exposure was significantly lower than the urban background level (20.3 µg/m(3)). In the univariate analyses the most influential determinants of individual exposure were long-term high-resolution dispersion-modelled levels of NO(2) outdoors at home and work, and concurrent NO(2) levels measured at a rural location, difference between those measured at an urban background and rural location and difference between those measured in busy street and at an urban background location, explaining 20, 16, 1, 2 and 4% (R(2)) of the 7-day personal NO(2) variation, respectively. A regression model including these variables explained 38% of the variation in personal NO(2) exposure. We found a small improvement by adding time-activity variables to the latter model (R(2) = 0.44). The results adds credibility primarily to long-term epidemiology studies that utilise long-term indices of NO(2) exposure at home or work, but also indicates that such studies may still suffer from exposure misclassification and dilution of any true effects. In contrast, urban background levels of NO(2) are poorly related to individual exposure.

Simulating indoor concentrations of NO(2) and PM(2.5) in multifamily housing for use in health-based intervention modeling

Residents of low-income multifamily housing can have elevated exposures to multiple environmental pollutants known to influence asthma. Simulation models can characterize the health implications of changing indoor concentrations, but quantifying the influence of interventions on concentrations is challenging given complex airflow and source characteristics. In this study, we simulated concentrations in a prototype multifamily building using CONTAM, a multizone airflow and contaminant transport program. Contaminants modeled included PM(2.5) and NO(2) , and parameters included stove use, presence and operability of exhaust fans, smoking, unit level, and building leakiness. We developed regression models to explain variability in CONTAM outputs for individual sources, in a manner that could be utilized in simulation modeling of health outcomes. To evaluate our models, we generated a database of 1000 simulated households with characteristics consistent with Boston public housing developments and residents and compared the predicted levels of NO(2) and PM(2.5) and their correlates with the literature. Our analyses demonstrated that CONTAM outputs could be readily explained by available parameters (R(2) between 0.89 and 0.98 across models), but that one-compartment box models would mischaracterize concentrations and source contributions. Our study quantifies the key drivers for indoor concentrations in multifamily housing and helps to identify opportunities for interventions.

PRACTICAL IMPLICATIONS

Many low-income urban asthmatics live in multifamily housing that may be amenable to ventilation-related interventions such as weatherization or air sealing, wall and ceiling hole repairs, and exhaust fan installation or repair, but such interventions must be designed carefully given their cost and their offsetting effects on energy savings as well as indoor and outdoor pollutants. We developed models to take into account the complex behavior of airflow patterns in multifamily buildings, which can be used to identify and evaluate environmental and non-environmental interventions targeting indoor air pollutants which can trigger asthma exacerbations.

Moving environmental justice indoors: understanding structural influences on residential exposure patterns in low-income communities

OBJECTIVES

The indoor environment has not been fully incorporated into the environmental justice dialogue. To inform strategies to reduce disparities, we developed a framework to identify the individual and place-based drivers of indoor environment quality.

METHODS

We reviewed empirical evidence of socioeconomic disparities in indoor exposures and key determinants of these exposures for air pollutants, lead, allergens, and semivolatile organic compounds. We also used an indoor air quality model applied to multifamily housing to illustrate how nitrogen dioxide (NO(2)) and fine particulate matter (PM(2.5)) vary as a function of factors known to be influenced by socioeconomic status.

RESULTS

Indoor concentrations of multiple pollutants are elevated in low-socioeconomic status households. Differences in these exposures are driven by the combined influences of indoor sources, outdoor sources, physical structures, and residential activity patterns. Simulation models confirmed indoor sources' importance in determining indoor NO(2) and PM(2.5) exposures and showed the influence of household-specific determinants.

CONCLUSIONS

Both theoretical models and empirical evidence emphasized that disparities in indoor environmental exposure can be significant. Understanding key determinants of multiple indoor exposures can aid in developing policies to reduce these disparities.

Short-term association between ambient air pollution and risk of hospitalization for acute myocardial infarction: results of the cardiovascular risk and air pollution in Tuscany (RISCAT) study

Air pollutant levels have been widely associated with increased hospitalizations and mortality from cardiovascular disease. In this study, the authors focused on pollutant levels and triggering of acute myocardial infarction (AMI). Data on AMI hospitalizations, air quality, and meteorologic conditions were collected in 6 urban areas of Tuscany (central Italy) during 2002-2005. Levels of particulate matter with an aerodynamic diameter ≤10 μm (PM(10)) (range of 4-year mean values, 28.15-40.68 μg/m(3)), nitrogen dioxide (range, 28.52-39.72 μg/m(3)), and carbon monoxide (range, 0.86-1.28 mg/m(3)) were considered, and increases of 10 μg/m(3) (0.1 mg/m(3) for carbon monoxide) were analyzed. A time-stratified case-crossover approach was applied. Area-specific conditional regression models were fitted, adjusting for time-dependent variables. Stratified analyses and analyses in bipollutant models were performed. Pooled estimates were derived from random-effects meta-analyses. Among 11,450 AMI hospitalizations, the meta-analytical odds ratio at lag(2) (2-day lag) was 1.013 (95% confidence interval (CI): 1.000, 1.026) for PM(10), 1.022 (95% CI: 1.004, 1.041) for nitrogen dioxide, and 1.007 (95% CI: 1.002, 1.013) for carbon monoxide. More susceptible subgroups were elderly persons (age ≥75 years), females, and older patients with hypertension and chronic obstructive pulmonary disease. This study adds to evidence for a short-term association between air pollutants and AMI onset, also evident at low pollutant levels, suggesting a need to focus on more vulnerable subjects.

Hazard assessment of chemical air contaminants measured in residences

Identifying air pollutants that pose a potential hazard indoors can facilitate exposure mitigation. In this study, we compiled summary results from 77 published studies reporting measurements of chemical pollutants in residences in the United States and in countries with similar lifestyles. These data were used to calculate representative mid-range and upper-bound concentrations relevant to chronic exposures for 267 pollutants and representative peak concentrations relevant to acute exposures for five activity-associated pollutants. Representative concentrations are compared to available chronic and acute health standards for 97 pollutants. Fifteen pollutants appear to exceed chronic health standards in a large fraction of homes. Nine other pollutants are identified as potential chronic health hazards in a substantial minority of homes, and an additional nine are identified as potential hazards in a very small percentage of homes. Nine pollutants are identified as priority hazards based on the robustness of measured concentration data and the fraction of residences that appear to be impacted: acetaldehyde; acrolein; benzene; 1,3-butadiene; 1,4-dichlorobenzene; formaldehyde; naphthalene; nitrogen dioxide; and PM(2.5). Activity-based emissions are shown to pose potential acute health hazards for PM(2.5), formaldehyde, CO, chloroform, and NO(2).

PRACTICAL IMPLICATIONS

This analysis identifies key chemical contaminants of concern in residential indoor air using a comprehensive and consistent hazard-evaluation protocol. The identification of a succinct group of chemical hazards in indoor air will allow for successful risk ranking and mitigation prioritization for the indoor residential environment. This work also indicates some common household activities that may lead to the acute levels of pollutant exposure and identifies hazardous chemicals for priority removal from consumer products and home furnishings.

Modelling inhalation exposure to combustion-related air pollutants in residential buildings: Application to health impact assessment

Buildings in developed countries are becoming increasingly airtight as a response to stricter energy efficiency requirements. At the same time, changes are occurring to the ways in which household energy is supplied, distributed and used. These changes are having important impacts on exposure to indoor air pollutants in residential buildings and present new challenges for professionals interested in assessing the effects of housing on public health. In many circumstances, models are the most appropriate way with which to examine the potential outcomes of future environmental and/or building interventions and policies. As such, there is a need to consider the current state of indoor air pollution exposure modelling. Various indoor exposure modelling techniques are available, ranging from simple statistical regression and mass-balance approaches, to more complex multizone and computational fluid dynamics tools that have correspondingly large input data requirements. This review demonstrates that there remain challenges which limit the applicability of current models to health impact assessment. However, these issues also present opportunities for better integration of indoor exposure modelling and epidemiology in the future. The final part of the review describes the application of indoor exposure models to health impact assessments, given current knowledge and data, and makes recommendations aimed at improving model predictions in the future.

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.

Long-term exposure to indoor air pollution and wheezing symptoms in infants

Long-term exposure to air pollution is suspected to cause recurrent wheeze in infants. The few previous studies have had ambiguous results. The objective of this study was to estimate the impact of measured long-term exposure to indoor air pollution on wheezing symptoms in infants. We monitored wheezing symptoms in diaries for a birth cohort of 411 infants. We measured long-term exposure to nitrogen oxides (NO(x)), NO(2), formaldehyde, PM(2.5) and black smoke in the infants' bedrooms and analyzed risk associations during the first 18 months of life by logistic regression with the dichotomous end-point 'any symptom-day' (yes/no) and by standard linear regression with the end-point 'number of symptom-days'. The results showed no systematic association between risk for wheezing symptoms and the levels of these air pollutants with various indoor and outdoor sources. In conclusion, we found no evidence of an association between long-term exposure to indoor air pollution and wheezing symptoms in infants, suggesting that indoor air pollution is not causally related to the underlying disease. Practical Implications Nitrogen oxides, formaldehyde and fine particles were measured in the air in infants' bedrooms. The results showed no evidence of an association between long-term exposure and wheezing symptoms in the COPSAC birth cohort.

Activity pattern and personal exposure to nitrogen dioxide in indoor and outdoor microenvironments

People are exposed to air pollution from a range of indoor and outdoor sources. Concentrations of nitrogen dioxide (NO(2)), which is hazardous to health, can be significant in both types of environments. This paper reports on the measurement and analysis of indoor and outdoor NO(2) concentrations and their comparison with measured personal exposure in various microenvironments during winter and summer seasons. Furthermore, the relationship between NO(2) personal exposure in various microenvironments and including activities patterns were also studied. Personal, indoor microenvironments and outdoor measurements of NO(2) levels were conducted using Palmes tubes for 60 subjects. The results showed significant differences in indoor and outdoor NO(2) concentrations in winter but not for summer. In winter, indoor NO(2) concentrations were found to be strongly correlated with personal exposure levels. NO(2) concentration in houses using a gas cooker was higher in all rooms than those with an electric cooker during the winter campaign, whereas there was no significant difference noticed in summer. The average NO(2) levels in kitchens with a gas cooker were twice as high as those with an electric cooker, with no significant difference in the summer period. A time-weighted average personal exposure was calculated and compared with measured personal exposures in various indoor microenvironments (e.g. front doors, bedroom, living room and kitchen); including non-smokers, passive smokers and smoker. The estimated results were closely correlated, but showed some underestimation of the measured personal exposures to NO(2) concentrations. Interestingly, for our particular study higher NO(2) personal exposure levels were found during summer (14.0+/-1.5) than winter (9.5+/-2.4).

Human Exposure: Indoor and Outdoor

Human exposure to air pollution is highly variable, reflecting the strong spatial and temporal variability of air pollutant concentrations in urban environments. A wide variety of outdoor and indoor sources contribute to acute and chronic exposures to respirable particles, carbon monoxide, nitrogen oxides, sulfur dioxide, ozone, volatile organic compounds and polycyclic aromatic hydrocarbons. Ambient air quality measurements and dispersion model simulations are commonly used to estimate population exposure to air pollutants in cities. In addition, time-activity micro-environmental and other dynamic time-space models can be used to characterise the personal exposure of individuals or population subgroups. People in developed countries typically spend 90% of their time indoors, and impact of indoor sources, such as tobacco smoking, gas cooking, construction and furnishing materials, and household chemicals (e.g. paints, adhesives, cleaning products, etc.), on personal exposure can become dominant. Recent exposure surveys have shown that personal exposure is typically higher than both indoor and outdoor concentrations of traffic-related pollutants such as benzene. In most cases, this is due to peak personal exposures occurring within transient (e.g. commuting) and other highly polluted micro-environments (e.g. petrol stations, garages, etc.). In developing countries, domestic fuel combustion (e.g. biomass burning for cooking and heating) has been identified as a major factor contributing to elevated exposure of the population to respirable particles, carbon monoxide, polycyclic aromatic hydrocarbons, nitrogen oxides and sulfur dioxide.

Factors influencing relationships between personal and ambient concentrations of gaseous and particulate pollutants

Previous exposure studies have shown considerable inter-subject variability in personal-ambient associations. This paper investigates exposure factors that may be responsible for inter-subject variability in these personal-ambient associations. The personal and ambient data used in this paper were collected as part of a personal exposure study conducted in Boston, MA, during 1999-2000. This study was one of a group of personal exposure panel studies funded by the U.S. Environmental Protection Agency's National Exposure Research Laboratory to address areas of exposure assessment warranting further study, particularly associations between personal exposures and ambient concentrations of particulate matter and gaseous co-pollutants. Twenty-four-hour integrated personal, home indoor, home outdoor and ambient sulfate, elemental carbon (EC), PM(2.5), ozone (O(3)), nitrogen dioxide (NO(2)) and sulfur dioxide were measured simultaneously each day. Fifteen homes in the Boston area were measured for 7 days during winter and summer. A previous paper explored the associations between personal-indoor, personal-outdoor, personal-ambient, indoor-outdoor, indoor-ambient and outdoor-ambient PM(2.5), sulfate and EC concentrations. For the current paper, factors that may affect personal exposures were investigated, while controlling for ambient concentrations. The data were analyzed using mixed effects regression models. Overall personal-ambient associations were strong for sulfate during winter (p<0.0001) and summer (p<0.0001) and PM(2.5) during summer (p<0.0001). The personal-ambient mixed model slope for PM(2.5) during winter but was not significant at p=0.10. Personal exposures to most pollutants, with the exception of NO(2), increased with ventilation and time spent outdoors. An opposite pattern was found for NO(2) likely due to gas stoves. Personal exposures to PM(2.5) and to traffic-related pollutants, EC and NO(2), were higher for those individuals living close to a major road. Both personal and indoor sulfate and PM(2.5) concentrations were higher for homes using humidifiers. The impact of outdoor sources on personal and indoor concentrations increased with ventilation, whereas an opposite effect was observed for the impact of indoor sources.

Predicting personal nitrogen dioxide exposure in an elderly population: integrating residential indoor and outdoor measurements, fixed-site ambient pollution concentrations, modeled pollutant levels, and time-activity patterns

Predicting chronic exposure to air pollution at the intra-urban scale has been recognized as a priority area of research for environmental epidemiology. Exposure assessment models attempt to predict and proxy for individuals' personal exposure to ambient air pollution, and there are no studies to date that explicitly attempt to compare and cross-validate personal exposure concentrations with pollutants modeled at the intra-urban level using methods such as interpolated surfaces and land-use regression (LUR) models. This study aimed to identify how well personal exposure to NO(2) (nitrogen dioxide) can be predicted from ambient exposure measurements and intra-urban exposure estimates using LUR and what other factors contribute to predicting variations in personal exposure beyond measured pollutant levels within home. Personal, indoor and outdoor NO(2) were measured in a population of older adults (>65 yr old) living in Hamilton, Canada. Our results show that personal NO(2) was most strongly associated with contemporaneously collected indoor and outdoor concentrations of NO(2). Predicted NO(2) exposures from intra-urban LUR models were not associated with personal NO(2), whereas interpolated surfaces of particulates and ozone were modestly associated. Combinations of variables that best predicted personal NO(2) variability were derived from time-activity diaries, interpolated surfaces of ambient particulate pollutants, and a city wide temporally matched average of NO(2). The nonsignificant associations between personal NO(2) and the modeled ambient NO(2) concentrations suggest that observed associations between NO(2) generated by LUR models and health effects are probably not produced by NO(2), but by other pollutants that follow a similar spatial pattern.

An examination of interventions to reduce respiratory health and injury hazards in homes of low-income families

We evaluated whether combining asthma trigger reduction with housing structural repairs, device disbursement and education in low-income households with children would improve self-reported respiratory health and reduce housing-related respiratory health and injury hazards (convenience sample of n=67 homes with 63 asthmatic and 121 non-asthmatic children). At baseline, a visual assessment of the home environment and a structured occupant interview were used to examine 29 potential injury hazards and 7 potential respiratory health hazards. A home-specific intervention was designed to provide the children's parents or caretakers with the knowledge, skills, motivation, supplies, equipment, and minimum housing conditions necessary for a healthy and safe home. The enrolled households were primarily Hispanic and owned their homes. On average, 8 injury hazards were observed in the homes at baseline. Four months following intervention, the average declined to 2.2 hazards per home (p<0.001), with 97% of the parents reporting that their homes were safer following the interventions. An average of 3.3 respiratory health hazards were observed in the homes at baseline. Four months following intervention, the average declined to 0.9 hazards per home (p<0.001), with 96% of parents reporting that the respiratory health of their asthmatic children improved. A tailored healthy homes improvement package significantly improves self-reported respiratory health and safety, reduces respiratory health and injury hazards, and can be implemented in concert with a mobile clinical setting.

Sources of nitrogen dioxide (NO2) in New Zealand homes: findings from a community randomized controlled trial of heater substitutions

Houses in New Zealand have inadequate space heating and a third of households use unflued gas heaters. As part of a large community intervention trial to improve space heating, we replaced ineffective heaters with more effective, non-polluting heaters. This paper assesses the contribution of heating and household factors to indoor NO2 in almost 350 homes and reports on the reduction in NO2 levels due to heater replacement. Homes using unflued gas heaters had more than three times the level of NO2 in living rooms [geometric mean ratio (GMR) = 3.35, 95% CI: 2.83-3.96, P < 0.001] than homes without unflued gas heaters, whereas homes using gas stove-tops had significantly elevated living room NO2 levels (GMR = 1.42, 95% CI: 1.05-1.93, P = 0.02). Homes with heat pumps, flued gas heating, or enclosed wood burners had significantly lower levels of NO2 in living areas and bedrooms. In homes that used unflued gas heaters as their main form of heating at baseline, the intervention was associated with a two-third (67%) reduction in NO2 levels in living rooms, when compared with homes that continued to use unflued gas heaters. Reducing the use of unflued gas heating would substantially lower NO2 exposure in New Zealand homes.

PRACTICAL IMPLICATIONS

Understanding the factors influencing indoor NO2 levels is critical for the assessment and control of indoor air pollution. This study found that homes that used unflued gas combustion appliances for heating and cooking had higher NO2 levels compared with homes where other fuels were used. These findings require institutional incentives to increase the use of more effective, less polluting fuels, particularly in the home environment.

Traffic-related air pollution and respiratory symptoms among asthmatic children, resident in Mexico City: the EVA cohort study

Background

Taffic-related air pollution has been related to adverse respiratory outcomes; however, there is still uncertainty concerning the type of vehicle emission causing most deleterious effects.

Methods

A panel study was conducted among 147 asthmatic and 50 healthy children, who were followed up for an average of 22 weeks. Incidence density of coughing, wheezing and breathing difficulty was assessed by referring to daily records of symptoms and child's medication. The association between exposure to pollutants and occurrence of symptoms was evaluated using mixed-effect models with binary response and poisson regression.

Results

Wheezing was found to relate significantly to air pollutants: an increase of 17.4 μg/m³ (IQR) of PM_2.5 (24-h average) was associated with an 8.8% increase (95% CI: 2.4% to 15.5%); an increase of 34 ppb (IQR) of NO₂ (1-h maximum) was associated with an 9.1% increase (95% CI: 2.3% to16.4%) and an increase of 48 ppb (IQR) in O₃ levels (1 hr maximum) to an increase of 10% (95% CI: 3.2% to 17.3%). Diesel-fueled motor vehicles were significantly associated with wheezing and bronchodilator use (IRR = 1.29; 95% CI: 1.03 to 1.62, and IRR = 1.32; 95% CI: 0.99 to 1.77, respectively, for an increase of 130 vehicles hourly, above the 24-hour average).

Conclusion

Respiratory symptoms in asthmatic children were significantly associated with exposure to traffic exhaust, especially from natural gas and diesel-fueled vehicles.

Spatial variations in estimated chronic exposure to traffic-related air pollution in working populations: a simulation

Background

Chronic exposure to traffic-related air pollution is associated with a variety of health impacts in adults and recent studies show that exposure varies spatially, with some residents in a community more exposed than others. A spatial exposure simulation model (SESM) which incorporates six microenvironments (home indoor, work indoor, other indoor, outdoor, in-vehicle to work and in-vehicle other) is described and used to explore spatial variability in estimates of exposure to traffic-related nitrogen dioxide (not including indoor sources) for working people. The study models spatial variability in estimated exposure aggregated at the census tracts level for 382 census tracts in the Greater Vancouver Regional District of British Columbia, Canada. Summary statistics relating to the distributions of the estimated exposures are compared visually through mapping. Observed variations are explored through analyses of model inputs.

Results

Two sources of spatial variability in exposure to traffic-related nitrogen dioxide were identified. Median estimates of total exposure ranged from 8 μg/m³ to 35 μg/m³ of annual average hourly NO₂ for workers in different census tracts in the study area. Exposure estimates are highest where ambient pollution levels are highest. This reflects the regional gradient of pollution in the study area and the relatively high percentage of time spent at home locations. However, for workers within the same census tract, variations were observed in the partial exposure estimates associated with time spent outside the residential census tract. Simulation modeling shows that some workers may have exposures 1.3 times higher than other workers residing in the same census tract because of time spent away from the residential census tract, and that time spent in work census tracts contributes most to the differences in exposure. Exposure estimates associated with the activity of commuting by vehicle to work were negligible, based on the relatively short amount of time spent in this microenvironment compared to other locations. We recognize that this may not be the case for pollutants other than NO_2. These results represent the first time spatially disaggregated variations in exposure to traffic-related air pollution within a community have been estimated and reported.

Conclusion

The results suggest that while time spent in the home indoor microenvironment contributes most to between-census tract variation in estimates of annual average exposures to traffic-related NO₂, time spent in the work indoor microenvironment contributes most to within-census tract variation, and time spent in transit by vehicle makes a negligible contribution. The SESM has potential as a policy evaluation tool, given input data that reflect changes in pollution levels or work flow patterns due to traffic demand management and land use development policy.

Air pollution, airway inflammation, and lung function in a cohort study of Mexico City schoolchildren

BACKGROUND

The biological mechanisms involved in inflammatory response to air pollution are not clearly understood.

OBJECTIVE

In this study we assessed the association of short-term air pollutant exposure with inflammatory markers and lung function.

METHODS

We studied a cohort of 158 asthmatic and 50 nonasthmatic school-age children, followed an average of 22 weeks. We conducted spirometric tests, measurements of fractional exhaled nitric oxide (Fe(NO)), interleukin-8 (IL-8) in nasal lavage, and pH of exhaled breath condensate every 15 days during follow-up. Data were analyzed using linear mixed-effects models.

RESULTS

An increase of 17.5 microg/m(3) in the 8-hr moving average of PM(2.5) levels (interquartile range) was associated with a 1.08-ppb increase in Fe(NO) [95% confidence interval (CI), 1.01-1.16] and a 1.07-pg/mL increase in IL-8 (95% CI 0.98-1.19) in asthmatic children and a 1.16 pg/ml increase in IL-8 (95% CI, 1.00-1.36) in nonasthmatic children. The 5-day accumulated average of exposure to particulate matter <2.5 microm in aerodynamic diamter (PM(2.5)) was significantly inversely associated with forced expiratory volume in 1 sec (FEV(1)) (p=0.048) and forced vital capacity (FVC) (p=0.012) in asthmatic children and with FVC (p=0.021) in nonasthmatic children. Fe(NO) and FEV(1) were inversely associated (p=0.005) in asthmatic children.

CONCLUSIONS

Exposure to PM(2.5) resulted in acute airway inflammation and decrease in lung function in both asthmatic and nonasthmatic children.

Predicting personal exposure of pregnant women to traffic-related air pollutants

As epidemiological studies report associations between ambient air pollution and adverse birth outcomes, it is important to understand determinants of exposures among pregnant women. We measured (48-h, personal exposure) and modeled (using outdoor ambient monitors and a traffic-based land-use regression model) NO, NO(2), fine particle mass and absorbance in 62 non-smoking pregnant women in Vancouver, Canada on 1-3 occasions during pregnancy (total N=127). We developed predictive models for personal measurements using modeled ambient concentrations and individual determinants of exposure. Geometric mean exposures of personal samples were relatively low (GM (GSD) NO=37 ppb (2.0); NO(2)=17 ppb (1.6); 'soot', as filter absorbance=0.8 10(-5) m(-1) (1.5); PM(2.2)=10 microg m(-3) (1.6)). Having a gas stove (vs. electric stove) in the home was associated with exposure increases of 89% (NO), 44% (NO(2)), 20% (absorbance) and 35% (fine PM). Interpolated concentrations from outdoor fixed-site monitors were associated with all personal exposures except NO(2). Land-use regression model estimates of outdoor air pollution were associated with personal NO and NO(2) only. The effects of outdoor air pollution on personal samples were consistent, with and without adjustment for other individual determinants (e.g. gas stove). These findings improve our understanding of sources of exposure to air pollutants among pregnant women and support the use of outdoor concentration estimates as proxies for exposure in epidemiologic studies.

Personal and ambient air pollution exposures and lung function decrements in children with asthma

BACKGROUND

Epidemiologic studies have shown associations between asthma outcomes and outdoor air pollutants such as nitrogen dioxide and particulate matter mass < 2.5 microm in diameter (PM(2.5)). Independent effects of specific pollutants have been difficult to detect because most studies have relied on highly correlated central-site measurements.

OBJECTIVES

This study was designed to evaluate the relationship of daily changes in percent-predicted forced expiratory volume in 1 sec (FEV(1)) with personal and ambient air pollutant exposures.

METHODS

For 10 days each, we followed 53 subjects with asthma who were 9-18 years of age and living in the Los Angeles, California, air basin. Subjects self-administered home spirometry in themorning, afternoon, and evening. We measured personal hourly PM(2.5) mass, 24-hr PM(2.5) elemental and organic carbon (EC-OC), and 24-hr NO(2), and the same 24-hr average outdoor central-site(ambient) exposures. We analyzed data with transitional mixed models controlling for personal temperature and humidity, and as-needed beta(2)-agonist inhaler use.

RESULTS

FEV(1) decrements were significantly associated with increasing hourly peak and daily average personal PM(2.5), but not ambient PM(2.5). Personal NO(2) was also inversely associated with FEV(1). Ambient NO(2) was more weakly associated. We found stronger associations among 37 subjects not taking controller bronchodilators as follows: Personal EC-OC was inversely associated with morning FEV(1); for an interquartile increase of 71 microg/m(3) 1-hr maximum personal PM(2.5), overall percent-predicted FEV(1) decreased by 1.32% [95% confidence interval (CI), -2.00 to -0.65%]; and for an interquartile increase of 16.8 ppb 2-day average personal NO(2), overall percent-predicted FEV(1) decreased by 2.45% (95% CI, -3.57 to -1.33%). Associations of both personal PM(2.5) and NO(2) with FEV(1) remained when co-regressed, and both confounded ambient NO(2).

CONCLUSIONS

Independent pollutant associations with lung function might be missed using ambient data alone. Different sets of causal components are suggested by independence of FEV(1) associations with personal PM(2.5) mass from associations with personal NO(2).

Indoor NO2 air pollution and lung function of professional cooks

Studies of cooking-generated NO2 effects are rare in occupational epidemiology. In the present study, we evaluated the lung function of professional cooks exposed to NO2 in hospital kitchens. We performed spirometry in 37 cooks working in four hospital kitchens and estimated the predicted FVC, FEV1 and FEF(25-75), based on age, sex, race, weight, and height, according to Knudson standards. NO2 measurements were obtained for 4 consecutive days during 4 different periods at 20-day intervals in each kitchen. Measurements were performed inside and outside the kitchens, simultaneously using Palm diffusion tubes. A time/exposure indicator was defined as representative of the cumulative exposure of each cook. No statistically significant effect of NO2 exposure on FVC was found. Each year of work as a cook corresponded to a decrease in predicted FEV1 of 2.5% (P = 0.046) for the group as a whole. When smoking status and asthma were included in the analysis the effect of time/exposure decreased about 10% and lost statistical significance. On predicted FEF(25-75), a decrease of 3.5% (P = 0.035) was observed for the same group and the inclusion of controllers for smoking status and asthma did not affect the effects of time/exposure on pulmonary function parameter. After a 10-year period of work as cooks the participants of the study may present decreases in both predicted FEV1 and FEF(25-75) that can reach 20 and 30%, respectively. The present study showed small but statistically significant adverse effects of gas stove exposure on the lung function of professional cooks.

Predicting residential indoor concentrations of nitrogen dioxide, fine particulate matter, and elemental carbon using questionnaire and geographic information system based data

Previous studies have identified associations between traffic-related air pollution and adverse health effects. Most have used measurements from a few central ambient monitors and/or some measure of traffic as indicators of exposure, disregarding spatial variability and/or factors influencing personal exposure-ambient concentration relationships. This study seeks to utilize publicly available data (i.e., central site monitors, geographic information system (GIS), and property assessment data) and questionnaire responses to predict residential indoor concentrations of traffic-related air pollutants for lower socioeconomic status (SES) urban households.As part of a prospective birth cohort study in urban Boston, we collected indoor and outdoor 3-4 day samples of nitrogen dioxide (NO(2)) and fine particulate matter (PM(2.5)) in 43 low SES residences across multiple seasons from 2003 - 2005. Elemental carbon concentrations were determined via reflectance analysis. Multiple traffic indicators were derived using Massachusetts Highway Department data and traffic counts collected outside sampling homes. Home characteristics and occupant behaviors were collected via a standardized questionnaire. Additional housing information was collected through property tax records, and ambient concentrations were collected from a centrally-located ambient monitor.The contributions of ambient concentrations, local traffic and indoor sources to indoor concentrations were quantified with regression analyses. PM(2.5) was influenced less by local traffic but had significant indoor sources, while EC was associated with traffic and NO(2) with both traffic and indoor sources. Comparing models based on covariate selection using p-values or a Bayesian approach yielded similar results, with traffic density within a 50m buffer of a home and distance from a truck route as important contributors to indoor levels of NO(2) and EC, respectively. The Bayesian approach also highlighted the uncertanity in the models. We conclude that by utilizing public databases and focused questionnaire data we can identify important predictors of indoor concentrations for multiple air pollutants in a high-risk population.

Predictors of concentrations of nitrogen dioxide, fine particulate matter, and particle constituents inside of lower socioeconomic status urban homes

Air pollution exposure patterns may contribute to known spatial patterning of asthma morbidity within urban areas. While studies have evaluated the relationship between traffic and outdoor concentrations, few have considered indoor exposure patterns within low socioeconomic status (SES) urban communities. In this study, part of a prospective birth cohort study assessing asthma etiology in urban Boston, we collected indoor and outdoor 3-4 day samples of nitrogen dioxide (NO2) and fine particulate matter (PM2.5) in 43 residences across multiple seasons from 2003 to 2005. Homes were chosen to represent low SES households, including both cohort and non-cohort residences in similar neighborhoods, and consisted almost entirely of multiunit residences. Reflectance analysis and X-ray fluorescence spectroscopy were performed on the particle filters to determine elemental carbon (EC) and trace element concentrations, respectively. Additionally, information on home characteristics (e.g. type, age, stove fuel) and occupant behaviors (e.g. smoking, cooking, cleaning) were collected via a standardized questionnaire. The contributions of outdoor and indoor sources to indoor concentrations were quantified with regression analyses using mass balance principles. For NO2 and most particle constituents (except outdoor-dominated constituents like sulfur and vanadium), the addition of selected indoor source terms improved the model's predictive power. Cooking time, gas stove usage, occupant density, and humidifiers were identified as important contributors to indoor levels of various pollutants. A comparison between cohort and non-cohort participants provided another means to determine the influence of occupant activity patterns on indoor-outdoor ratios. Although the groups had similar housing characteristics and were located in similar neighborhoods, cohort members had significantly higher indoor concentrations of PM2.5 and NO2, associated with indoor activities. We conclude that the effect of indoor sources may be more pronounced in high-density multiunit dwellings, and that future epidemiological studies in these populations should explicitly consider these sources in assigning exposures.

Housing characteristics and indoor concentrations of nitrogen dioxide and formaldehyde in Quebec City, Canada

Concentrations of nitrogen dioxide and formaldehyde were determined in a study of 96 homes in Quebec City, Canada, between January and April 2005. In addition, relative humidity, temperature, and air change rates were measured in homes, and housing characteristics were documented through a questionnaire to occupants. Half of the homes had ventilation rates below 7.5 L/s person. Nitrogen dioxide (NO2) and formaldehyde concentrations ranged from 3.3 to 29.1 microg/m3 (geometric mean 8.3 microg/m3) and from 9.6 to 90.0 microg/m3 (geometric mean of 29.5 microg/m3), respectively. The housing characteristics documented in the study explained approximately half of the variance of NO2 and formaldehyde. NO2 concentrations in homes were positively correlated with air change rates (indicating a significant contribution of outdoor sources to indoor levels) and were significantly elevated in homes equipped with gas stoves and, to a lesser extent, in homes with gas heating systems. Formaldehyde concentrations were negatively correlated with air change rates and were significantly elevated in homes heated by electrical systems, in those with new wooden or melamine furniture purchased in the previous 12 months, and in those where painting or varnishing had been done in the sampled room in the previous 12 months. Results did not indicate any significant contribution of indoor combustion sources, including wood-burning appliances, to indoor levels of formaldehyde. These results suggest that formaldehyde concentrations in Quebec City homes are caused primarily by off-gassing, and that increasing air change rates in homes could reduce exposure to this compound. More generally, our findings confirm the influence of housing characteristics on indoor concentrations of NO2 and formaldehyde.

Influence of short-term exposure to airborne Der p 1 and volatile organic compounds on skin barrier function and dermal blood flow in patients with atopic eczema and healthy individuals

BACKGROUND

Epidemiological studies indicate environmental pollutants to be involved in the increase in the prevalence of allergic diseases. In human exposure studies, volatile organic compounds (VOCs) have been shown to cause exacerbations of allergic asthma whereas, no data concerning atopic eczema (AE) are available.

OBJECTIVE

We investigated the effect of airborne VOCs on the skin of patients with AE and controls in the presence or absence of house dust mite allergen, Der p 1.

METHODS

In a double-blind crossover study, 12 adults with AE and 12 matched healthy volunteers were exposed on their forearms to Der p 1 and subsequently to a mixture of 22 VOCs (M22, 5 mg/m(3)) in a total body exposure chamber for 4 h. Transepidermal water loss (TEWL) and skin blood flow were measured in all subjects before, during and after exposure. Additionally, an atopy patch test (APT) with Der p 1 was applied to the skin after exposure.

RESULTS

A significant increase in transepidermal water loss was observed 48 h after exposure to VOCs as compared with exposure with filtered air in all individuals (mean difference: +34%; 95% Confidence Interval: 7-69%). Prior Der p 1 exposure resulted in a significant rise of dermal blood flow after 48 h in patients with AE but not in controls. Six out of seven patients showed enhanced atopy patch test (APT) reactions to HDM allergen after previous exposure to VOCs.

CONCLUSION

Our results show that exposure to VOCs - at concentrations commonly found in indoor environments - can damage the epidermal barrier and enhance the adverse effect of Der p 1 on sensitized subjects with AE. These findings may contribute to a better understanding of the mechanisms underlying the increase in prevalence and exacerbation of AE.

Ventilation in public housing: implications for indoor nitrogen dioxide concentrations

Although elevated nitrogen dioxide (NO2) exposures may exacerbate asthma, few studies have examined indoor NO2 levels in low-income, urban neighborhoods, where asthma prevalence is high. As part of the Healthy Public Housing Initiative, NO2 was measured in 77 homes within three Boston public housing developments, using Palmes tubes placed in the kitchen, living room, and outdoors. Air exchange rates (AERs) were assessed using a perfluorocarbon tracer technique. Overall NO2 levels were [mean (ppb)+/-s.d.]: kitchen (43+/-20, n=100), living room (36+/-17, n=102), outdoor (19+/-6, n=91). Indoor NO2 levels were significantly higher in the heating season (living room: 43 ppb vs. 26 ppb, kitchen: 50 ppb vs. 33 ppb), while AERs were significantly lower in the heating season (medians 0.49/h vs. 0.85/h). Significant univariate predictors of indoor concentrations include: outdoor NO2 levels, AERs, and occupancy. AERs and outdoor NO2 remained significant in multivariate models (P<0.05). A dummy variable for supplemental heating with gas stove was not significant (P=0.14), but had a large, positive coefficient. Indoor NO2 levels in this cohort are higher than those generally reported in residential US settings, associated in part with increased gas stove usage and decreased AERs during the heating season.

PRACTICAL IMPLICATIONS

Indoor air quality is mainly a function of outdoor concentrations, indoor sources, ventilation, and residential behavior. Indoor exposures to nitrogen dioxide and other combustion pollutants may be elevated within low-income housing developments due to the presence of multiple sources, poor ventilation, small apartment size, and behavioral responses to apartment conditions (e.g. supplemental heating with gas stove). This information may be used by housing authorities and other landlords to decrease potential environmental stressors, through interventions such as source substitution and improved ventilation, particularly for sensitive sub-populations such as asthmatics.

Association of indoor nitrogen dioxide exposure with respiratory symptoms in children with asthma

RATIONALE

Chronic exposure to indoor nitrogen dioxide (NO2) is a public health concern. Over half of U.S. households have a source of NO2, and experimental data suggest potential for adverse respiratory effects.

OBJECTIVE

To examine associations of indoor NO2 exposure with respiratory symptoms among children with asthma.

METHODS

NO2 was measured using Palmes tubes, and respiratory symptoms in the month before sampling were collected during home interviews of mothers of 728 children with active asthma. All were younger than 12 yr, lived at the sampled home for at least 2 mo, and had asthma symptoms or used maintenance medication within the previous year.

MEASUREMENTS

Respiratory symptoms (wheeze, persistent cough, shortness of breath, chest tightness).

RESULTS

Mean (SD) NO2 was 8.6 (9.1) ppb in homes with electric ranges and 25.9 (18.1) ppb in homes with gas stoves. In models stratified by housing type (a factor associated with socioeconomic status), gas stove presence and elevated NO2 were each significantly associated with respiratory symptoms, controlling for age, ethnicity, medication, mold/mildew, water leaks, and season of sampling. Among children in multifamily housing, exposure to gas stoves increased likelihood of wheeze (odds ratio [OR], 2.27; 95% confidence interval [95% CI], 1.15, 4.47), shortness of breath (OR, 2.33; 95% CI, 1.12, 5.06), and chest tightness (OR, 4.34; 95% CI, 1.76, 10.69), whereas each 20-ppb increase in NO2 increased both likelihood of any wheeze (OR, 1.52; 95% CI, 1.04, 2.21) or chest tightness (OR, 1.61; 95% CI, 1.04, 2.49), and days of wheeze (rate ratio (RR), 1.33; 95% CI, 1.05, 1.68) or chest tightness (RR, 1.51; 95% CI, 1.18, 1.91).

CONCLUSION

Exposure to indoor NO2 at levels well below the Environmental Protection Agency outdoor standard (53 ppb) is associated with respiratory symptoms among children with asthma in multifamily housing.

Personal exposure to PM2.5, black smoke and NO2 in Copenhagen: relationship to bedroom and outdoor concentrations covering seasonal variation

Epidemiological studies have found negative associations between human health and particulate matter in urban air. In most studies outdoor monitoring of urban background has been used to assess exposure. In a field study, personal exposure as well as bedroom, front door and background concentrations of PM(2.5), black smoke (BS), and nitrogen dioxide (NO(2)) were measured during 2-day periods in 30 subjects (20-33 years old) living and studying in central parts of Copenhagen. The measurements were repeated in the four seasons. Information on indoor exposure sources such as environmental tobacco smoke (ETS) and burning of candles was collected by questionnaires. The personal exposure, the bedroom concentration and the front door concentration was set as outcome variable in separate models and analysed by mixed effect model regression methodology, regarding subject levels as a random factor. Seasons were defined as a dichotomised grouping of outdoor temperature (above and below 8 degrees C). For NO(2) there was a significant association between personal exposure and both the bedroom, the front door and the background concentrations, whereas for PM(2.5) and BS only the bedroom and the front door concentrations, and not the background concentration, were significantly associated to the personal exposure. The bedroom concentration was the strongest predictor of all three pollution measurements. The association between the bedroom and front door concentrations was significant for all three measurements, and the association between the front door and the background concentrations was significant for PM(2.5) and NO(2), but not for BS, indicating greater spatial variation for BS than for PM(2.5) and NO(2). For NO(2), the relationship between the personal exposure and the front door concentration was dependent upon the "season", with a stronger association in the warm season compared with the cold season, and for PM(2.5) and BS the same tendency was seen. Time exposed to burning of candles was a significant predictor of personal PM(2.5), BS and NO(2) exposure, and time exposed to ETS only associated with personal PM(2.5) exposure. These findings imply that the personal exposure to PM(2.5), BS and NO(2) depends on many factors besides the outdoor levels, and that information on, for example, time of season or outdoor temperature and residence exposure, could improve the accuracy of the personal exposure estimation.