Particle number emission rates of aerosol sources in 40 German households and their contributions to ultrafine and fine particle exposure

Indoor Emissions Contributed the Majority of Ultrafine Particles in Chinese Urban Residences

Ultrafine particle (UFP) pollution should be controlled to reduce its effects on health. The design of control measures is limited owing to the uncertainty of source contributions in Chinese residences, where indoor UFP pollution is more severe than in Western residences. Herein, a source-specific, time-dependent UFP concentration model was developed by applying an infiltration factor model incorporating coagulation effects. A Monte Carlo framework with the UFP concentration model was employed to estimate the probabilistic distribution of source contributions in Chinese residences. The input parameter distributions were determined based on our survey and previous studies. The annually averaged indoor UFP concentration was estimated at (2.75 ± 1.71) × 104 #/cm3, ranging from 2.35 × 103 to 1.27 × 105 #/cm3 outside the kitchen, and at (5.48 ± 3.08) × 104 #/cm3, ranging from 2.90 × 103 to 1.94 × 105 #/cm3 in the kitchen. Indoor sources contributed more to indoor UFPs, accounting for 61% in the nonkitchen and 80% in the kitchen, surpassing their contribution to indoor PM2.5 in Chinese residences. Meanwhile, the indoor UFP emission contributions were higher than those in the United States, Canada, and Germany, owing to higher emissions from cooking and cigarette smoking. These results will aid in elucidating human exposure to UFPs and in designing more targeted control measures.

Indoor Exposure and Regional Inhaled Deposited Dose Rate during Smoking and Incense Stick Burning-The Jordanian Case as an Example for Eastern Mediterranean Conditions

Tobacco smoking and incense burning are commonly used in Jordanian microenvironments. While smoking in Jordan is prohibited inside closed spaces, incense burning remains uncontrolled. In this study, particle size distributions (diameter 0.01-25 µm) were measured and inhaled deposited dose rates were calculated during typical smoking and incense stick-burning scenarios inside a closed room, and the exposure was summarized in terms of number and mass concentrations of submicron (PN_Sub) and fine particles (PM_2.5). During cigarette smoking and incense stick-burning scenarios, the particle number concentrations exceeded 3 × 10⁵ cm^-3. They exceeded 5 × 10⁵ cm^-3 during shisha smoking. The emission rates were 1.9 × 10¹⁰, 6.8 × 10¹⁰, and 1.7 × 10¹⁰ particles/s, respectively, for incense, cigarettes, and shisha. That corresponded to about 7, 80, and 120 µg/s, respectively. Males received higher dose rates than females, with about 75% and 55% in the pulmonary/alveolar during walking and standing, respectively. The total dose rates were in the order of 10¹²-10¹³ #/h (10³-10⁴ µg/h), respectively, for PN_Sub and PM_2.5. The above reported concentrations, emissions rates, and dose rates are considered seriously high, recalling the fact that aerosols emitted during such scenarios consist of a vast range of toxicant compounds.

Aerosol concentrations and size distributions during clinical dental procedures

Background

Suspected aerosol-generating dental instruments may cause risks for operators by transmitting pathogens, such as the SARS-CoV-2 virus. The aim of our study was to measure aerosol generation in various dental procedures in clinical settings.

Methods

The study population comprised of 84 patients who underwent 253 different dental procedures measured with Optical Particle Sizer in a dental office setting. Aerosol particles from 0.3 to 10 μm in diameter were measured. Dental procedures included oral examinations (N = 52), restorative procedures with air turbine handpiece (N = 8), high-speed (N = 6) and low-speed (N = 30) handpieces, ultrasonic scaling (N = 31), periodontal treatment using hand instruments (N = 60), endodontic treatment (N = 12), intraoral radiographs (N = 24), and dental local anesthesia (N = 31).

Results

Air turbine handpieces significantly elevated <1 μm particle median (p = 0.013) and maximum (p = 0.016) aerosol number concentrations as well as aerosol particle mass concentrations (p = 0.046 and p = 0.006) compared to the background aerosol levels preceding the operation. Low-speed dental handpieces elevated >5 μm median (p = 0.023), maximum (p = 0.013) particle number concentrations,> 5 μm particle mass concentrations (p = 0.021) and maximum total particle mass concentrations (p = 0.022). High-speed dental handpieces elevated aerosol concentration levels compared to the levels produced during oral examination.

Conclusions

Air turbine handpieces produced the highest levels of <1 μm aerosols and total particle number concentrations when compared to the other commonly used instruments. In addition, high- and low-speed dental handpieces and ultrasonic scalers elevated the aerosol concentration levels compared to the aerosol levels measured during oral examination. These aerosol-generating procedures, involving air turbine, high- and low-speed handpiece, and ultrasonic scaler, should be performed with caution.

Clinical significance

Aerosol generating dental instruments, especially air turbine, should be used with adequate precautions (rubber dam, high-volume evacuation, FFP-respirators), because aerosols can cause a potential risk for operators and substitution of air turbine for high-speed dental handpiece in poor epidemic situations should be considered to reduce the risk of aerosol transmission.

A holistic modeling framework for estimating the influence of climate change on indoor air quality

The IPCC 2021 report predicts rising global temperatures and more frequent extreme weather events in the future, which will have different effects on the regional climate and concentrations of ambient air pollutants. Consequently, changes in heat and mass transfer between the inside and outside of buildings will also have an increasing impact on indoor air quality. It is therefore surprising that indoor spaces and occupant well-being still play a subordinate role in the studies of climate change. To increase awareness for this topic, the Indoor Air Quality Climate Change (IAQCC) model system was developed, which allows short and long-term predictions of the indoor climate with respect to outdoor conditions. The IAQCC is a holistic model that combines different scenarios in the form of submodels: building physics, indoor emissions, chemical-physical reaction and transformation, mold growth, and indoor exposure. IAQCC allows simulation of indoor gas and particle concentrations with outdoor influences, indoor materials and activity emissions, particle deposition and coagulation, gas reactions, and SVOC partitioning. These key processes are fundamentally linked to temperature and relative humidity. With the aid of the building physics model, the indoor temperature and humidity, and pollutant transport in building zones can be simulated. The exposure model refers to the calculated concentrations and provides evaluations of indoor thermal comfort and exposure to gaseous, particulate, and microbial pollutants.

Effect of energy renovation and occupants' activities on airborne particle concentrations in Swedish rental apartments

Exposure to airborne particles causes detrimental health effects, hence their assessment in indoor environments, where people spend most of the time, is important. The influence of energy renovation and occupants' activities on airborne particle concentrations was assessed in seven occupied Swedish residences. Ultrafine particle (UFP, <100 nm) number concentrations, PM2.5 (<2.5 μm) and black carbon (BC, <900 nm) mass concentrations were simultaneously measured inside and outside before, after renovation, and during follow-up. The average indoor UFP number concentrations increased from 6200 (±4070) cm^-3 before renovation to 12,700 (±6040) cm^-3 during the follow up, as the number of indoor activities doubled. Indoor UFP number concentrations depended mainly on frequency and type of occupants' activities in studied residences (e.g., cooking, candle burning). The average indoor PM2.5 concentration decreased from 8.6 (±5.8) μg m^-3 before renovation to 2.5 (±1.3) μg m^-3 during follow up, as the activities that generated PM2.5 decreased, and infiltration of outdoor particles could have been decreased due to renovation measures. However, the indication of infiltration decrease during the follow up, assessed on the basis of indoor to outdoor ratios during non-activity times (with no influence of occupants' activities), was not observed after the renovation and should be treated with caution. In this study indoor PM2.5 and BC were influenced by activities and outdoor concentrations. Reduction of exposure to indoor UFP, might be obtained by optimization of kitchen exhaust flows. An improved design of supply air inlets in mechanical exhaust ventilation systems may reduce PM2.5 infiltration. Occupants' logbook records, needed for identification of sources contributing to particle exposure, proved useful but not always accurate compared to technical measurements of activities and UFP concentrations. Development of simple and reliable activity detection systems is needed to complement logbooks and allow accurate assessment of source contribution to particle exposure in homes and associated health effects.

Aerosol dynamics modeling of sub-500 nm particles during the HOMEChem study

We spend most of our time in built environments. The cumulative exposure to particulate matter (PM) occurring in these built environments can potentially be comparable to or even exceed that occurring outdoors. Therefore, it is critical to understand the sources, dynamics, and fate of PM in built environments. This work focuses on aerosol dynamics modeling (including coagulation, deposition, and exfiltration) of sub-500 nm particles measured inside a test house during the HOMEChem campaign while performing prescribed cooking activities. Deposition characteristics of the test house, emission rates and factors, and the fate of particles are presented. Number emission rates calculated for two different heat sources (stove and hot plate) and the various meals cooked on them were highest for sub-10 nm particles. Coagulation and deposition contributed comparably to the particle number concentration decay. Most of the PM (90% number-based and 70% mass-based) deposited within the house while the remaining fraction left the test house volume via exfiltration. Simulation results show that while increased air exchange rate reduces indoor PM mass concentration, it can lead to increased number concentration. An increase from 0.5 to 5 ACH (comparable to the equivalent air change rate from running a well-dimensioned portable air cleaner) would result in a 70% reduction in PM mass-based exposure while a further increase from 5 to 20 ACH would only result in an additional 21% reduction.