Outdoor Levels Research Articles

Environmental house calls can reduce symptoms of chemical intolerance: a demonstration of personalized exposure medicine.

The goals of this investigation were to 1) identify and measure exposures inside homes of individuals with chemical intolerance (CI), 2) provide guidance for reducing these exposures, and 3) determine whether our environmental house calls (EHCs) intervention could reduce both symptoms and measured levels of indoor air contaminants. CI is an international public health and clinical concern, but few resources are available to address patients' often disabling symptoms. Numerous studies show that levels of indoor air pollutants can be two to five (or more) times higher than outdoor levels. Fragranced consumer products, including cleaning supplies, air fresheners, and personal care products, are symptom triggers commonly reported by susceptible individuals. A team of professionals trained and led by a physician/industrial hygienist and a certified indoor air quality specialist conducted a series of 5 structured EHCs in 37 homes of patients reporting CI. We report three case studies demonstrating that an appropriately structured home intervention can teach occupants how to reduce indoor air exposures and associated symptoms. Symptom improvement, documented using the Quick Environmental Exposure and Sensitivity Inventory Symptom Star, corresponded with the reduction of indoor air volatile organic compounds, most notably fragrances. These results provide a deeper dive into 3 of the 37 cases described previously in Perales et al. (2022). We address the long-standing dilemma that worldwide reports of fragrance sensitivity have not previously been confirmed by human or animal challenge studies. Our ancient immune systems' 'first responders', mast cells, which evolved 500 million years ago, can be sensitized by synthetic organic chemicals whose production and use havegrown exponentially since World War II. We propose that these chemicals, which include now-ubiquitous fragrances, trigger mast cell degranulation and inflammatory mediator release in the olfactory-limbic tract, thus altering cerebral blood flow and impairing mood, memory, and concentration (often referred to as 'brain fog'). The time has come to translate these research findings into clinical and public health practice.

A study on indoor air quality at daycare centers using IoT environmental sensors

ABSTRACT Indoor air quality (IAQ) is a major concern at daycare centers, due to the weaker immune system of children. Although IAQ is typically measured in accordance with the ISO-16000 standard, environmental sensors have recently become widely used due to their ability to consistently monitor air quality at a lower cost. In this study, We installed IoT sensors indoors and outdoors at ten daycare centers to measure PM(PM2.5, PM10), CO2, temperature, and humidity, as well as window opening-closing sensors to identify ventilation behavior. Indoor PM concentrations were consistently lower than outdoor levels, increasing from 7:00 AM, peaking between 9:00 AM and 12:00 PM, and decreasing during nap time (12:00 PM to 2:00 PM). CO2 levels were generally higher indoors than outdoors, peaking at 2:00 PM before decreasing. Windows were opened more frequently at 7:00 AM, 8:30 AM, and 3:00 PM. The correlation analysis revealed that significant factors influencing CO2 concentration were window opening duration. Ventilation rates per person at the daycare centers ranged from 1.77 to 10.69 m3/h, below both Korean and ASHRAE guidelines. The results of this study can provide valuable insights for developing strategies to improve indoor air quality in daycare centers that depend on window ventilation.

The effect of particle size, meteorological parameters, and building airtightness on particulate matters infiltration

Introduction: The present study analyzed the infiltration behavior of size- fractionated particles and the influencing parameters. Materials and methods: The studies were carried out in two apartments under varying conditions of airtightness, utilizing real-time surveillance of Particulate Matters (PM0.3, PM1.0, PM2.5, PM10), along with air exchange rates and meteorological factors. The seasonal variations of the indoor dissemination of particulate matters have been also discussed. Results: The analysis of correlations indicated a strong dependency of indoor Particulate Matter (PM) concentrations on outdoor levels. However, the penetration patterns varied across different particle sizes. The highest contribution to outdoor PM10 was observed for PM 2.5-10 while indoors, the predominant particle size was among the finer categories, PM0.3-1.0. Moreover, window air-tightening appeared to decrease the overall effective leakage area of the building envelope, which in turn slightly lowered the ratio of indoor to outdoor PMs as well as the infiltrability for particles of all sizes. However, this intervention did not alter the distribution of particles within indoor environments.The most penetrated particles were observed in the size range 0.3-1.0 µm and then PM<0.3 µm, and the least in the size range 2.5-10 µm. Conclusion: Particle dimensions and external sources primarily influenced the degree of particle infiltration, significantly overshading the impact of weather-related factors. The relationship between indoor and outdoor particulate matter was diminished by the airtightness of windows, particularly for larger particles. No notable difference was observed in the infiltrability and indoor distribution of particles of varying sizes between the winter and fall seasons.

Characterization of façade sound insulation by impulse response measurements for various source position formats: a case study

The sound insulation of a building's façade is important for estimating the indoor levels in relation to the outdoor levels. The measurement of the sound insulation (i.e., outdoor-to-indoor level difference) is significantly affected by the methodology employed. In this study, an impulse response measurement methodology is incorporated, alleviating uncertainties associated with the measurement's chain. The effect of loudspeaker position on sound insulation is investigated with respect to three source position formats (horizontal, inclined, and linear), each consisting of three source positions. The appropriate length of the excitation signal is verified using the impulse-to-noise ratio (INR) indicator. Focusing on the outdoor-to-indoor level differences, corresponding to the energy captured in each external receiver (placed very close to windows) and across all the internal receivers per source position, significant differences were found. This indicates the impact of both the distance and angle of incidence between the outdoor receiver and the sound source position. In terms of the average outdoor-to-indoor level difference among the three source formats, the linear format shows slightly lower values compared to the horizontal and inclination source formats, which are similar to each other, but follows the main trend.

Outdoor light at night, air pollution and risk of incident type 2 diabetes

BackgroundAir pollution and outdoor light at night (LAN) have been reported to be related to type 2 diabetes (T2D). However, their interaction with risk of T2D remains uncertain. Therefore, our study aimed to explore the relationship between outdoor LAN, air pollution and incident T2D. MethodsOur study included a cohort of 24,147 subjects recruited from 2015 to 2018 in Ningbo, China. Land use regression models were used to evaluate particulate matter with a diameter ≤2.5 μm (PM2.5), ≤10 μm (PM10) and nitrogen dioxide (NO2). Satellite images data with a spatial resolution of 500m was used to estimate outdoor LAN levels. T2D new cases were identified by medical records based on health information system. Cox proportional hazards models were used to estimate Hazard ratios (HRs) and 95% confidence intervals (CIs). Moreover, we investigated the multiplicative and additive interactions between air pollution and outdoor LAN. ResultsDuring 108,908 person-years of follow-up period, 1016 T2D incident cases were identified. The HRs (95% CIs) were 1.22 (1.15, 1.30) for outdoor LAN, 1.20 (1.00, 1.45) for PM2.5, 1.23 (1.11, 1.35) for PM10 and 1.19 (1.04, 1.37) for NO2 in every interquartile range increase, respectively. Furthermore, significant interactions were observed between outdoor LAN and NO2. ConclusionsOur findings indicated that air pollution and outdoor LAN were positively associated with T2D. Moreover, we observed an interaction between outdoor LAN and NO2 suggesting that stronger associations for outdoor LAN and T2D in areas with higher levels of NO2, and for NO2 and T2D in areas with higher levels of outdoor LAN.

Assessment of air quality in the Philadelphia, Pennsylvania subway.

Subways are popular and efficient modes of transportation in cities. However, people are exposed to high levels of particulate matter (PM) in subways. Subway air quality in the United States has been investigated in a few cities, but data is lacking on simultaneous measurement of several pollutants, especially ultrafine particles (UFP) and black carbon (BC), in combination with different size fractions of PM. The goals of this study are to assess air quality in a belowground subway and compare it with outdoor ambient levels, to examine temporal variability of PM in the subway, and to analyze the correlation between PM and BC. Particulate matter of varying sizes (PM1, PM2.5, PM10), UFP, and BC were measured using DustTrak, nanoparticle detector, and micro aethalometer, respectively. Measurements were made at the belowground subway platform and the aboveground street level at 15th Street subway station in Philadelphia during summer 2022. Belowground mean PM1, PM2.5, and PM10 were 112.2 ± 61.3 µg/m3, 120 ± 65.5 µg/m3, and 182.1 ± 132 µg/m3, respectively, which were 5.4, 5.7, and 7.6 times higher than the respective aboveground street levels. The UFP lung deposited surface area (LDSA) (59.4 ± 36.2 µm2/cm3) and BC (9.5 ± 5.4 μg/m3) belowground were 1.7 times and 10.7 times higher than the aboveground. The pollutant concentration varied from day-to-day on both the locations. A higher positive correlation was found between the belowground BC and PM2.5 (r = 0.51, p < 0.05) compared to the aboveground (r = 0.16, p < 0.05). This study showed high levels of particulate matter exposure at a belowground subway station in Philadelphia. Particulate matter levels were about 5 to 8 times higher at belowground subway station than the corresponding aboveground street level. Higher levels were also observed for UFP lung deposited surface area (LDSA), while black carbon levels showed the highest concentration at the belowground level by a factor of ten compared to the aboveground level. The study shows the need for air quality management at belowground subways to reduce particulate matter exposure for the commuters.

Evaluating Indoor Air Quality in Schools: Is the Indoor Environment a Haven during High Pollution Episodes?

Pollution data were collected at five schools in Hong Kong using low-cost, sensor-based monitors both indoors and outdoors during two consecutive high pollution episodes. The pollutants monitored included NO2, O3, PM2.5, and PM10, which were also used as input to a health risk communication protocol known as Air Quality Health Index (AQHI). CO2 was also measured simultaneously. The study aimed to assess the relationship between indoor pollutant concentrations and AQHI levels with those outdoors and to evaluate the efficacy of building operating practices in protecting students from pollution exposure. The results indicate that the regular air quality monitoring stations and outdoor pollutant levels at schools exhibit similar patterns. School AQHI levels indoors were generally lower than those outdoors, with PM10 levels showing a larger proportional contribution to the calculated values indoors. NO2 levels in one school were in excess of outdoor values. CO2 monitored in classrooms commonly exceeded indoor guidelines, suggesting poor ventilation. One school that employed air filtration had lower indoor PM concentrations compared to other schools; however, they were still similar to those outdoors. O3 levels indoors were consistently lower than those outdoors. This study underscores the utility of on-site, sensor-based monitoring for assessing the health impacts of indoor and community exposure to urban air pollutants. The findings suggest a need for improved ventilation and more strategic air intake placement to enhance indoor air quality.

Impact of Outdoor Air Pollutants Exposure on the Severity and Outcomes of Community-Acquired Pneumonia in Gabes Region, Tunisia.

Background Acute community-acquired pneumonia (CAP) is considered the leading cause of infectious death worldwide. Air pollution and prolonged exposure to airborne contaminants have been implicated in various respiratory conditions, including asthma and chronic obstructive pulmonary disease (COPD). However, the specific impact of air pollution on pneumonia, particularly CAP, remains underexplored. Given the rising levels of urban air pollution and its potential health ramifications, our study aimed to examine the association between exposure to outdoor air pollution and severity as well as the outcomes of pneumonia cases requiring hospitalization. Methodology A cohort analytical study with retrospective data collection was carried out in the pulmonology department of the Gabès University Hospital between January and October 2022. We compared levels of particulate matter less than or equal to 10µm in aerodynamic diameter (PM10),sulfur dioxide (SO2),ozone (O3), moisture and ambient temperature with severity and outcomes ofpneumonia requiring hospitalization. The choice of these specific pollutants and environmental factors was based on their established impact on respiratory health and their prevalence in the study region. Results Increased sulfur dioxide (SO2) levels were associated with increased use of non-invasive ventilation (NIV) (r = 0.400). Higher levels of particulate matter (PM10) were significantly associated with the development of lung abscesses. Similarly, increased humidity and ambient temperature were strongly correlated with the development of lung abscesses. Increased air SO2 levels were correlated with a higher CURB65 score (r = 0.299). High outdoor SO2 levels and increasing moisture content were associated with increased Pneumonia Severity Index (PSI) score (r = 0.303 and = 0.310, respectively). Higher levels of PM10 were associated with an increased risk of pleural effusion, a serious complication of pneumonia. Finally, higher ambient temperatures were correlated with more extensive opacities on chest X-rays (r = 0.706), suggesting the severity of pneumonia. Conclusion This study highlights the significant associations between environmental factors and various clinical parameters in pneumonia patients. The findings underscore the importance of considering environmental exposures, such as air quality and weather conditions, in understanding and managing the severity of pneumonia.

Effectiveness of Air Filtration in Reducing PM2.5 Exposures at a School in a Community Heavily Impacted by Air Pollution

Reducing children’s exposure to air pollution is a priority among California communities heavily impacted by air pollution exposures. We conducted an observational air quality study at a school to investigate the effectiveness of improved Heating, Ventilation, and Cooling (HVAC) system filters and portable air cleaners (PACs) in reducing children’s exposure to fine particulate matter (PM2.5) under real-world classroom conditions. This study included five classrooms, three of which had PACs. Halfway through the study period, high-efficiency HVAC filters were installed in all five classrooms. Continuous measurements of outdoor and in-classroom PM2.5 concentrations were used to evaluate filtration effectiveness. The air filtration strategies, alone and in combination, demonstrated 14–56% reductions in indoor PM2.5 concentrations compared to outdoor levels. There were significant improvements in filtration resulting from HVAC filter upgrades in the two classrooms without PACs (11% and 22% improvement, p &lt; 0.001). Upgrading HVAC filters in classrooms with PACs did not significantly improve filtration effectiveness, suggesting that utilizing both strategies simultaneously may not meaningfully improve air quality under these circumstances. CO2 data, as a proxy for ventilation, helped demonstrate that the observed filtration effectiveness was likely impacted by the variable HVAC system use and open doors.

Oxidant concentrations and photochemistry in a vehicle cabin.

Indoor air quality (IAQ) in vehicles can be important to people's health, especially for those whose occupations require them to spend extensive time in vehicles. To date, research on vehicle IAQ has primarily focused on direct emissions as opposed to chemistry happening in vehicle cabins. In this work, we conducted time-resolved measurements of the oxidants and oxidant precursors ozone (O3), nitric oxide (NO), nitrogen dioxide (NO2), and nitrous acid (HONO) inside the cabin of a 2012 Toyota Rav4 under varying ventilation conditions (i.e., car off, car on with passive ventilation, car on with mechanical ventilation via the recirculating fan, and car on with mechanical ventilation via the direct fan). Ozone levels inside the vehicle were significantly lower than outdoors under most conditions, and were approximately half the outdoor levels when the direct fan was in operation. Nitric oxide and NO2 concentrations were very low both inside the vehicle and outdoors. Nitrous acid levels in the vehicle were lower than reported values in other indoor environments, though much higher than expected outdoor levels. We also investigated the potential for photochemical production of radicals in the vehicle. Time- and wavelength-resolved solar irradiance spectra were collected, and steady state hydroxyl radical (OH) and nitrate radical (NO3) concentrations were calculated. Steady state OH concentrations were predicted to be similar to those in air masses in residences illuminated by sunlight, suggesting the importance of HONO photolysis in vehicles. Conversely, nitrate radicals (NO3) were not considered significant indoor oxidants in our study due to rapid titration by NO. Overall, our findings emphasize the importance of both air exchange and photochemistry in shaping the composition of air inside vehicles.

Impacts of daily household activities on indoor particulate and NO2 concentrations; a case study from oxford UK

This study explores indoor air pollutant (PM1, PM2.5 and NO2) concentrations over a 15-week period during the COVID-19 pandemic in a typical suburban household in Oxford, UK. A multi-room intensive monitoring study was conducted in a single dwelling using 10 air quality sensors measuring real-time pollutant concentrations at 10 second intervals to assess temporal and spatial variability in PM1, PM2.5 and NO2 concentrations, identify pollution-prone areas, and investigate the impact of residents' activities on indoor air quality. Significant spatial variations in PM concentrations were observed within the study dwelling, with highest hourly concentrations (769.0 & 300.9 μg m−3 for PM2.5, and PM1, respectively) observed in the upstairs study room, which had poor ventilation. Cooking activities were identified as a major contributor to indoor particulate pollution, with peak concentrations aligning with cooking events. Indoor NO2 levels were typically higher than outdoor levels, particularly in the kitchen where a gas-cooking appliance was used. There was no significant association observed between outdoor and indoor PM concentrations; however, a clear correlation was evident between kitchen PM emissions and indoor levels. Similarly, outdoor NO2 had a limited influence on indoor air quality compared to kitchen activities. Indoor sources were found to dominate for both PM and NO2, with higher Indoor/Outdoor (I/O) ratios observed in the upstairs bedroom and the kitchen. Overall, our findings highlight the contribution of indoor air pollutant sources and domestic activities to indoor air pollution exposure, notably during the COVID-19 pandemic when people were typically spending more time in domestic settings. Our novel findings, which suggest high levels of pollutant concentrations in upstairs (first floor) rooms, underscore the necessity for targeted interventions. These interventions include the implementation of source control measures, effective ventilation strategies and occupant education for behaviour change, all aimed at improving indoor air quality and promoting healthier living environments.

Energy efficiencies model for thermal comfort in urban applications

Improving people's standard of living has increased their requirements for the environment. Increasing air temperature in urban areas due to urban heat islands (UHI) has been a global concern since industrialization. Apart from suitable facilities and landscapes, a comfortable outdoor thermal environment can improve the efficiency of urban space use. Ensuring outdoor comfort is an integral part of the design agenda where the UHI phenomenon plays a significant role. A study has been conducted on a residential building campus to analyze the effect of these heat island countermeasures (individual and combined) with the help of the simulation tool Grasshopper. A 3D reference model of a small residential campus is developed. The outdoor thermal comfort level is studied for this case, and Universal Thermal Climate Index (UTCI) is evaluated. Further, several UHI mitigation strategies such as wall and roof reflectivity, vegetation, plantation, pavement configuration, and shading are applied to find their effect on the micro-climate and outdoor thermal comfort. Based on the simulation outcomes, urban geometry is identified as the most influential design factor in decreasing the urban heat island effect and outdoor thermal comfort. The study's principal objective is to develop a simulation framework including all mitigation strategies and find the best case for UHI reduction.

Polymer-composite triboelectric nanogenerators with hook-shaped electrode for wind energy harvesting

Triboelectric nanogenerators (TENGs) based on the composite of polystyrene (PS) and silver nanowires (Ag-nWs) have been investigated. With open-circuit voltage, short-circuit current and power density of ∼200 V, ∼15 μA and ∼395 mW/m2 respectively in the contact separation mode, these TENGs exhibit highly reliable performance. To harvest the wind energy, a novel hook-shape geometry of the top fluttering electrode is demonstrated which is constructed using light-weight rectangular aluminum foil and is fixed at both ends. With PS:Ag-nW composite film, the hook-shaped-electrode TENG (HSE-TENG) provided an average VOC of 15 V, ISC of 0.75 μA and a power density of 18.33 mW/m2 at a wind speed of 5.5 m/s. Under high outdoor temperature and humidity levels, HSE-TENG demonstrated a high degree of response stability. In addition, the proposed TENG is affixed on the top surface of a moving vehicle, where it has been demonstrated to scavenge the energy from the experienced wind force. This study indicates that material strategies and device design approaches can be amalgamated to achieve high performance and operational robustness together for a specific application regime.

Measurement of black carbon exposure in urban classrooms during rush hours

Traffic-related air pollutants are predominantly emitted in urban environments; therefore, analyzing their impact on indoor air quality (IAQ) is important. Effectively managing IAQ is vital, given the extensive duration individuals, particularly students, spend indoors. This study conducted a quantitative assessment of black carbon (BC) and indoor and outdoor particulate matter (PM2.5, particles with diameter ≤2.5 μm) concentrations in five South Korean classrooms to determine the root cause and effects of traffic-related air pollutants on indoor environments. The research specifically focused on indoor BC levels during rush hours, that is, periods marked by increased traffic volume. The analysis revealed that the mean indoor and outdoor BC concentrations in the five classrooms were measured at 1.03 (95% CI: 0.69, 1.36) and 1.38 (95% CI: 0.79, 1.96) μg/m3, respectively, while the mean PM2.5 concentrations were measured at 17.07 (95% CI: 12.92, 13.62) and 29.89 (95% CI: 10.88, 48.89) μg/m3, respectively. The indoor-to-outdoor (I/O) ratio of BC in the five classrooms during the occupied period was 0.77 (95% CI: 0.69, 0.84) and 0.62 (95% CI: 0.51, 0.72) for PM2.5. During the unoccupied period, the I/O ratio of BC was 0.68 (95% CI: 0.63, 0.72) and 0.53 (95% CI: 0.42, 0.63) for PM2.5. The rise in urban traffic increased the BC outdoor level by 47% and the PM2.5 concentration by 13%. Classrooms situated closer to roadways had higher BC levels than those located at a greater distance. During rush hours, the BC concentration in the classroom closest to the major road was 2.03 (95% CI: 1.78, 2.27) μg/m3, while the furthest classroom recorded a concentration of 0.88 (95% CI: 0.79, 0.96) μg/m3. During commuting times, classroom BC concentrations increased by up to 5.86 μg/m3 owing to student door-opening activities, increasing the I/O ratio by approximately 20%. Consequently, the average BC concentration in classrooms during rush hours was approximately double that recorded during non-rush hours (0.73 μg/m3). These findings are instrumental in developing strategies to enhance IAQ in educational settings and guiding urban planning decisions regarding the location of schools.

Indoor air quality at the Arab governmental girls’ schools

Background A proper and adequate school environment is important for an effective learning process and maintaining the health of the students as they spend most of their time in schools. The physical school environment includes the physical structures; presence of chemicals and biological agents; and the surrounding environment, including air, water, and materials. This study aimed to evaluate the indoor air quality (IAQ) in governmental girls’ schools in the Kingdom of Saudi Arabia (KSA). Methods Seventeen girls’ schools were randomly selected in the Eastern Province of KSA. The indoor levels of PM10 and PM2.5, volatile organic compounds, CO, NO2, and CO2 were measured at different sites inside each school during four months of the year 2020. Results Levels of the six air pollutants were higher inside schools adjacent to roads with moderate traffic activity than schools with low and very low traffic activity. However, the mean level of CO2 inside the selected schools was higher than its outdoor level, suggesting the predominance of an indoor source of CO2. The levels of all measured air pollutants inside governmentally constructed school buildings were higher than those inside the rental type. Conclusion The average levels of air pollutants inside the selected schools were much lower than their air quality guidelines (AQGs), while some CO2 and NO2 levels exceeded their AQGs at some schools.

Air Quality Monitoring Using Low-Cost Sensors in Urban Areas of Jodhpur, Rajasthan.

Air pollution poses a significant health hazard in urban areas across the globe, with India being one of the most affected countries. This paper presents environmental monitoring study conducted in Jodhpur, Rajasthan, India, to assess air quality in diverse urban environments. The study involved continuous indoor and outdoor air quality monitoring, focusing on particulate matter (PM2.5) levels, bioaerosols, and associated meteorological parameters. Laser sensor-based low-cost air quality monitors were utilized to monitor air quality and Anderson 6-stage Cascade Impactor & Petri Dish methods for bioaerosol monitoring. The study revealed that PM2.5 levels were consistently high throughout the year, highlighting the severity of air pollution in the region. Notably, indoor PM2.5 levels were often higher than outdoor levels, challenging the common notion of staying indoors during peak pollution. The study explored the spatial and temporal diversity of air pollution across various land-use patterns within the city, emphasizing the need for tailored interventions in different urban areas. Additionally, bioaerosol assessments unveiled the presence of pathogenic organisms in indoor and outdoor environments, posing health risks to residents. These findings underscore the importance of addressing particulate matter and bioaerosols in air quality management strategies. Despite the study's valuable insights, limitations, such as using low-cost air quality sensors and the need for long-term data collection, are acknowledged. Nevertheless, this research contributes to a better understanding of urban air quality dynamics and the importance of public awareness in mitigating the adverse effects of air pollution. In conclusion, this study underscores the urgent need for effective air quality management strategies in urban areas. The findings provide valuable insights for policymakers and researchers striving to address air pollution in rapidly urbanizing regions.

Short-Term Exposure to Air Pollution and the Incidence and Mortality of Stroke: A Meta-Analysis.

The relationship between short-term exposure to various air pollutants [particulate matter <10 μm (PM 10 ), particulate matter <2.5 μm (PM 2.5 ), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), carbon monoxide, and ozone (O 3 )] and the incidence and mortality of stroke remain unclear. We conducted a comprehensive search across databases, including PubMed, Web of Science, and others. A random-effects model was employed to estimate the odds ratios (OR) and their 95% CIs. Short-term exposure to PM 10 , PM 2.5 , NO 2 , SO 2 , and O 3 was associated with increased stroke incidence [per 10 μg/m 3 increase in PM 2.5 : OR = 1.005 (95% CI: 1.004-1.007), per 10 μg/m 3 increase in PM 10 : OR = 1.006 (95% CI: 1.004-1.009), per 10 μg/m 3 increase in SO 2 : OR = 1.034 (95% CI: 1.020-1.048), per 10 μg/m 3 increase in NO 2 : OR = 1.029 (95% CI: 1.015-1.043), and O 3 for per 10 μg/m 3 increase: OR: 1.006 (95% CI: 1.004-1.007)]. In addition, short-term exposure to PM 2.5 , PM 10 , SO 2, and NO 2 was correlated with increased mortality from stroke [per 10 μg/m 3 increase in PM 2.5 : OR = 1.010 (95% CI: 1.006-1.013), per 10 μg/m 3 increase in PM 10 : OR = 1.004 (95% CI: 1.003-1.006), per 10 μg/m 3 increase in SO 2 : OR = 1.013 (95% CI: 1.007-1.019) and per 10 μg/m 3 increase in NO 2 : OR = 1.012 (95% CI: 1.008-1.015)]. Reducing outdoor air pollutant levels may yield a favorable outcome in reducing the incidence and mortality associated with strokes.

Comparison of infiltration of different particle sizes and influencing parameters

The size fractional distribution of indoor and outdoor particles was investigated to understand how particle size, air change rate, building airtightness, and meteorological parameters affect particle infiltration behavior. The experiments were performed for two apartments, one without airtightness intervention and the other after sealing the window gaps. Although the correlation analysis showed that the indoor PM trend was highly dependent on outdoor conditions, different penetration behavior for different particle sizes was noticed. Despite the absence of indoor sources, the size fractional distribution of particles in the indoor and outdoor environment did not follow the same pattern. Moreover, airtightness somehow reduced the envelope effective leakage area and slightly decreased the indoor/outdoor ratio and infiltration factor for all particle sizes; however, it did not affect the relative infiltrability. The highest penetration rates were observed in the size range of 0.3–1.0 μm and the lowest rates were in the 2.5–10 μm range. Although with particles greater than 0.3 μm, the infiltration of fine particles was higher than that of coarse particles, the infiltrability of PM < 0.3 was slightly lower than PM0.3-1.0, probably due to the penetration dominated by the concentration gradient. Particle size, envelope airtightness, and outdoor source were the main factors that governed fractional particle infiltration, overshadowing the effect of meteorological parameters. Furthermore, window airtightness decreased the indoor-outdoor PM correlation, especially for coarser particles. It caused approximately a 1-h lag-time between the indoor and outdoor PM trend, a positive point in case of accidental increase of outdoor levels.

Assessment of Outdoor Background Radiation Level and its Radiological Hazards at Jimeta and Yola Towns of Adamawa State, Nigeria

The radiation from different types of radionuclides has both advantages and disadvantages. However, detailed research reveals that the drawbacks of several radionuclides far outweigh their advantages, particularly in regions with high concentrations, posing alarming impacts on human health. The study focuses on assessing outdoor background radiation levels in Jimeta and Yola towns, Adamawa State, Nigeria. Using a well-calibrated portable halogen-quenched Geiger Muller (GM) detector at 20 locations, measurements were taken at an elevation of 1.0m above ground level, with GPS tracking for accurate location. The research evaluates radiological health hazards and radiation effective doses to different body organs based on outdoor background exposure rates. Comparison with recommended permissible limits reveals that mean values for outdoor background exposure levels (0.016 mRh-1) and absorbed dose rates (147.46 nGyh-1) exceed safety limits (0.013 mRh-1, 84.0 nGyh-1) set by UNSCEAR and ICRP. The total excessive lifetime cancer risk (ELCR) ranged from 0.33× 10−3 to 2.61× 10−3 , with a mean value of 0.78 × 10−3 , close to the world average lifetime cancer limit (1.45× 10−3 ). Despite the mean annual effective dose equivalent (AEDE) (0.2219mSvy-1) being below the recommended limit of 1.00 mSvy-1 for general public exposure, and effective doses to various body organs remaining below 1.0 mSvy-1, the study indicates potential long-term health hazards such as cancer due to accumulated doses. Generally, the study shows that Jimeta and Yola Metroplis is relatively safe radiologically with little contamination which could be attributed to the geological formation and partly due to human activity such as market and car park for transport system in the area. However, the contamination will not pose any immediate radiological health effect on resident of the area but there is tendency for long –term health hazards in the future such as cancer due to doses accumulated. It is therefore recommended that regular radiation monitoring exercise should be conducted on the area from time to time in order to checkmate both the workers and the members of public from high radiation exposure.

Estimation of children's CO2 generation rates in naturally ventilated educational buildings

Indoor CO2 concentration serves as an indicator of indoor air quality, which is mainly influenced by occupants' CO2 generation rate, outdoor ventilation rate and outdoor CO2 levels. Determining the CO2 generation rate is fundamental to design effective ventilation systems that ensure good indoor air quality. The ASTM D6245 standard offers a method to estimate human CO2 generation based on sex, age, body mass, and activity level. However, due to the limited number of studies on CO2 generation rate for children and adolescents in daily scholarly activities, accurated values are difficult to estimate. This research uses a stochastic grey box modelling approach to estimate CO2 generation rates in naturally ventilated schools and compares it with the standard approach. This method can address the complexities and variations in real educational environments. The proposed model was verified through an experimental campaign including 32 classrooms with students aged 4, 10, 13 and 16 years. The model provided a detailed description of the indoor CO2 dynamics in 72% of the studied cases. Estimated CO2 generation rates were found to be in line with the expected standard value of between 1.0 MET to 2.0 MET activity levels (7.07–12.65 L/h for a 4-year-old, 9.63–13.29 L/h for a 10-year-old, 14.54–19.32 L/h for a 13-year-old, and 12.11–20.53 L/h for a 16-year-old). These findings not only bridge the gap in children's CO2 generation rates but also introduce a novel approach to assess human CO2 generation rates under uncontrolled conditions.