Bin Zhao

Tsinghua University | TH · Department of Building Science, School of Architecture

Background Epidemiological studies have reported the associations between nitrogen dioxide (NO2) and pediatric asthma incidence, but unable to ascertain indoor NO2 sources. We estimated the pediatric asthma incidence and corresponding economic losses attributable to NO2 from indoor and outdoor sources in urban areas in China. Methods Exposure to NO...

Indoor particulate matter (PM) and black carbon (BC) are associated with adverse cardiopulmonary effect. However, the cumulative and interactive effects of the mixture of size-fractioned PMs and BC on cardiopulmonary function are not well understood, and its underlying biological mechanisms remain unclear. This repeated-measure study was conducted...

Air pollution and unsuitable climatic conditions both limit the application of natural ventilation (NV). The combined effects of climate change and air pollution on NV's potential are unknown, particularly in China, where the atmospheric environment has improved greatly since 2014, but temperatures have increased with global warming. The purpose of...

Human surfaces have a significant influence on indoor air due to their interaction with ozone. The oxidation products of unsaturated fatty acids and triglycerides have not been systematically studied. In this investigation, the kinetic model (KM-SUB-Skin-Clothing) was used to simulate the interaction of ozone and human skin lipids, including squale...

Evidence is accumulating that the increasing incidence of type 2 diabetes and obesity is correlated with exposure to certain phthalates, which brings growing concern to the public health of China. However, the extent to which phthalate restrictions will alleviate these health concerns remains unclear. Here, we employed a sequential modeling approac...

The WHO AQGs 2021 incorporates more stringent guidelines for air pollution, which now include both ambient and indoor air quality. We discuss the challenges to meeting the AQGs for indoor air. We suggest a cocktail-like treatment solution that combines efforts from a multidiscipline field of policy, technology, and education.

Portable air cleaners (PACs) can remove airborne SARS-CoV-2 exhaled by COVID-19 infectors indoor. However, effectively locating PAC to reduce the infection risk is still poorly understood. Here, we propose a simple model by regressing an equation of seven similarity criteria based on CFD-modeled results of a scenario matrix of 128 cases for office...

The World Health Organization (WHO) Air Quality Guidelines (AQG) 2021 for PM2.5 is tightened to be 5 μg/m3. We firstly estimated deaths attributable to human exposure to PM2.5 (DAHP) to be 455 thousand (372-527) in urban China in 2019, of which indoor sources contributed 253 thousand (207-294) deaths. The economic losses related to PM2.5 from indoo...

Global warming could change building ventilation by altering window opening behavior, which may threaten public health as the average occupant spends over 80% of their time indoors. Here, by considering outdoor temperature as the main driving force and integrating the impact of operating air-conditioner, we constructed the climate-zone-specific rel...

Ambient fine particulate matter (diameters <2.5 µm; PM2.5) and nitrogen dioxide (NO2) pollution are responsible for substantial health burdens in China, contributing to a considerable proportion of global mortality. Simultaneously, the proportion of indoor smoking and cooking-induced PM2.5 and NO2 pollution lacks robust exposure assessment findings...

Even people mostly stay indoors, they are constantly exposed to outdoororiginated particles. Outdoor particles can penetrate into indoor environments via the building envelope through ventilation and air infiltration. Penetration factor is the ratio of outdoor particles entering the indoor environments through the building’s envelope, and infiltrat...

Fine particulate matter (PM2.5) pollution is of national concern in China. Indoor PM2.5 concentrations may contribute significantly to human exposure because people spend most of their time indoors. In this study, we systematically reviewed the level of indoor PM2.5 concentrations in residences, offices, and schools in China. We looked for correspo...

In countries suffering from heavy ambient air pollution, ventilation is a problem, as ventilation intakes outdoor air pollutants, such as particulate matter with an aerodynamic diameter less than 2.5 um (PM2.5), while removing indoor air pollutants. Thus, it is important to identify appropriate ventilation-purification strategies to build healthy i...

Understanding the cost-effectiveness of possible interventions to reduce air pollution levels is crucial to developing sustainable mitigation and adaption strategies. Although people spend more than 80% of their time indoors, the role of air purifiers in mitigating personal exposure to indoor PM2.5 of outdoor origin has not yet been quantified, esp...

Indoor ozone can react with unsaturated compounds like human skin lipids and form harmful oxidation products. In this study, we collected skin wipes used on the foreheads and forearms of 31 Chinese volunteers, and measured the concentrations of the top 15 saturated fatty acids (SFAs), top 15 unsaturated fatty acids (UFAs), top 15 unsaturated trigly...

Epidemiological studies have reported significant associations of outdoor NO2 with daily mortality. These studies used ambient NO2 concentrations as a proxy of personal exposure of outdoor-originated NO2 (PEO NO2), which may lead to biased health effect estimates. This study was aiming to explore whether modified outdoor NO2 exposure can reduce thi...

Most epidemiological studies usually employ ambient air pollutant concentrations as a proxy of personal exposure to air pollutants originating outdoors, which could lead to a biased estimation of health effects. Herein, we modeled infiltration and exposure factors as the modifications of personal exposure to ambient PM2.5, PM10, O3, NO2, and SO2 fo...

Ultrafine particles (UFPs) are of concern because of their high pulmonary deposition efficiency. However, present control measures are generally targeted at fine particles (PM2.5), with little effect on UFPs. The health effects of UFPs at different PM2.5 concentrations may provide a basic for controlling UFPs but remain unclear in polluted areas. S...

A growing number of cases have proved the possibility of airborne transmission of the coronavirus disease 2019 (COVID-19). Ensuring an adequate ventilation rate is essential to reduce the risk of infection in confined spaces. In this study, we estimated the association between the infection probability and ventilation rates with the Wells–Riley equ...

Most respiratory infectious diseases may be spread by human exhaled droplets and droplet nuclei. The once-in-a-century coronavirus disease 2019 (COVID-19) pandemic has shown that the airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cannot be ignored. Understanding the movement and transmission of human exhaled d...

Ambient ultrafine particles (UFPs: particles of diameter less than 100 nm) cause significant adverse health effects. As people spend most time indoors, the outdoor-to-indoor transport of UFPs plays a critical role in the accuracy of personal exposure assessments. Herein, a strategy was proposed to measure and analyze the infiltration factor (Finf)...

Size-dependent filtration efficiencies of face masks and respirators for removing SARS-CoV-2-laden aerosols - Yumeng Liu, Bin Zhao

China has been experiencing a sharp increase in outdoor ozone concentration. The deposition velocity of ozone onto human surfaces strongly affects the indoor ozone concentration, and the production of oxidation products. In this study, we measured the deposition velocity of ozone onto human surfaces in six Chinese residential rooms, each housing 1–...

Using air purifier as a supplementary protective measure in dental clinics during the COVID-19 pandemic - Bin Zhao, Na An, Chen Chen

Studies have proved that outdoor nitrogen dioxide (NO2) has adverse health effects for people. Nowadays, most people spend much more time indoors than outdoors, and the indoor NO2 concentration is affected by a variety of indoor and outdoor factors. In order to fully understand the relationship between indoor and outdoor NO2 concentrations, which i...

Air pollution is currently a huge threat to human health, which leads to heavy demand for efficient air filters for filtration. Among which, ultrafine particles (UFPs, diameter less than 100 nm) can especially result in more severe health diseases. Here, a scalable metal-organic framework (MOF)-based nanofiber filter for high-efficiency particles r...

While PM2.5 (particles with aerodynamic diameter less than 2.5 µm) concentrations in China are beginning to decline because of pollution abatement measures, ozone (O3) concentrations continue to rise. In this study, we have used a Monte Carlo approach to estimate breathing-rate adjusted (BRA) population exposure to ozone and its oxidation products...

Background: A growing number of epidemiological cases are proving the possibility of airborne transmission of coronavirus disease 2019 (COVID-19). Ensuring adequate ventilation rate is essential to reduce the risk of infection in confined spaces. Methods: We obtained the quantum generation rate by a COVID-19 infector with a reproductive number base...

Air pollution is a worldwide problem, especially for China which is one of the countries with the worst PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm) pollution in the world. A wealth of studies proved that PM2.5 pollution can lead to diseases such as cerebrovascular, respiratory and cardiopulmonary diseases. Considerin...

Chinese cooking methods can produce a large amount of hazardous cooking oil fume, which may include masses of organic carbon. This study collected PM2.5 samples of cooking emissions from five most common Chinese cooking methods (stir-, pan-, deep-frying, steaming, and boiling). Organic carbon (OC) and elemental carbon (EC) in PM2.5 were analyzed us...

Ultrafine particles (UFPs) are produced by human activities in outdoor and indoor environments. It is important to control indoor UFPs for their health effects on human and long duration that people spend indoors. Filtration is important in mechanical ventilation system for UFP removal to reduce human exposure to UFPs. The filtration efficiency for...

China has been facing rapidly growing energy use and severe outdoor air pollution, such as fine particles (PM2.5) and ozone (O3) in recent years. Ambient air could emigrate to indoor environments through openings of buildings, influencing the concentrations of indoor PM2.5, O3, and volatile organic compounds (VOCs) as well as the energy consumption...

China is experiencing severe PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 μm) pollution. Controlling indoor PM2.5 concentration is critical to reduce personal exposure to PM2.5 as people spend most of their time indoors. A two-dimensional Monte Carlo model was applied to estimate the PM2.5 population exposure distribution...

Cooking is an important source of particulate matters (PM) in Chinese residences. Exposure to fine particles (PM2.5) in cooking oil fume (COF) emitted during cooking can lead to adverse health effects. Keeping the kitchen doors open might be conducive to improving air quality in kitchen, nonetheless, cooking activities would still elevate the parti...

Background Ionization air purifiers, which purify particulate matter (PM) by producing vast number of negative air ions (NAI), are widely used. Recent study implied that ionization air purification could bring respiratory benefits but deterioration of heart rate variability (HRV). However, its underlying molecular mechanisms remain unclear. Object...

Spraying during dental practices can generate quantity of droplets, which transform into droplet nuclei and suspend in the air of clinic in the form of aerosol. Either droplets or aerosols may carry microorganisms and cause air contamination in the hospital, posing potential threat to the health of clinical healthcare staff and patients. The presen...

Indoor air quality (IAQ) plays a significant role in human health, and CO2 has a long history of use as an IAQ indicator. Formaldehyde is one of the most ubiquitous indoor pollutants with proven adverse health effects. However, formaldehyde sensors are generally expensive, and they are not as accurate as CO2 sensors. Thus, it is important to determ...

This study aimed to assess the fine particulate pollution and propose an effective control strategy to mitigate the fine particulate pollution inside entrance booths. The air exchange rate and indoor/outdoor ratios of fine particles (particles with an aerodynamic diameter of less than 2.5 μm: PM2.5) of an entrance booth mockup were measured, the re...

In the present study, we developed a chemical dynamic model to describe the infiltration of size‐resolved ammonium nitrate aerosols from outdoor to indoor environments. This model considered the penetration factor, deposition rate, and the reversible reaction process, which was quantified by the diffusive molar flux on the surface of ammonium nitra...

Residential Chinese cooking can lead to severe exposure to carcinogenic fine particles (PM2.5) from cooking-oil fumes. Keeping the kitchen door open is conducive to improving air quality in the kitchen, but it can result in further diffusion of PM2.5 emissions into adjacent rooms. In this study, PM2.5 exposure concentrations were measured in the ki...

Indoor air pollution is associated with numerous adverse health outcomes. Air purifiers are widely used to reduce indoor air pollutants. Ionization air purifiers are becoming increasingly popular for their low power consumption and noise, yet its health effects remain unclear. This randomized, double-blind crossover study is conducted to explore th...

Ultrafine particles (UFPs) are hazardous air pollutants produced by human activities in outdoor and indoor environments. Filtration in mechanical ventilation systems or air purifiers is an effective technology for the removal of outdoor- or indoor-origin particles, to reduce human exposure to UFPs in indoor environments, where people spend the majo...

Summary Background Human exposure to multiphase semi-volatile organic compounds (SVOCs) via multiple routes has been associated with health risks. Residential air cleaning interventions remove SVOCs adsorbed on airborne particles, which subsequently affects indoor concentrations of SVOCs in other phases. We aimed to investigate the effect of reside...

To assess the factors influencing indoor exposure from outdoor PM2.5-bounded elemental carbon (EC), we developed a Monte Carlo framework to investigate the ambient exposure factor (the ratio of exposure concentration to ambient concentration) of PM2.5-bounded EC. The framework integrates outdoor PM2.5-bounded EC concentrations, the probability of w...

The chemical composition of fine particulate matter (PM2.5) emitted during cooking such as polycyclic aromatic hydrocarbons (PAHs), chemical elements (especially heavy metals), organic carbon (OC), and elemental carbon (EC) are of great concern to human health in China. We collected five duplicate sets of samples of cooking emissions from a Chinese...

Numerous research have explored the associations of outdoor or indoor fine particulate matter (PM2.5) and health effects, however, few studies compared the effects of indoor PM2.5 originated from outdoor (PM2.5,os) and indoor sources (PM2.5,is). To assess the associations of PM2.5,os and PM2.5,is with cardiopulmonary function in patients with chron...

Phthalates are ubiquitous pollutants in residential environments. Indoor airborne phthalate concentrations in Chinese residences are comparable to, or even higher than, those of western countries. However, the major sources of phthalates in Chinese residences are not well known. In this study, we measured the phthalates emission features of 23 flat...

Background: China has one of the highest PM2.5 (particulate matter with an aerodynamic diameter smaller than 2.5 um) pollution levels in the world. It might still be long before air quality reaches the National Class II standard of 35 ug/m3. Objective: We aim to estimate the potential reduction in premature mortality by reducing indoor PM2.5 levels...

Cooking is an important source of air pollutants in Chinese residences. Cooking emissions are influenced by many factors, among which oil temperature is one of the most influential. In this study, 15 typical Chinese dishes, prepared using oil-based cooking methods (stir-, pan- and deep-frying), were chosen. The experiment was repeated three times w...

The household second hand smoke problem is still severe in China due to the large number of smokers and the prevalence of smoking at home. We selected ten Chinese cigarettes, including seven best-selling products of different brands and three types of products of the same popular brand, to measure the emission rates of ultrafine particles (UFPs: pa...

Changes in the chemical constitution and sources of ambient PM2.5 following the infiltration of air into indoor environments were investigated. We collected PM2.5 samples from air inside and outside 31 rooms in Beijing residences during hazy episodes. We calculated the indoor‐to‐outdoor ratios and the correction (kⁱ) of each infiltration factor for...

Outdoor ozone has been proven to be strongly associated with both morbidity and mortality. The deposition of ozone on indoor surfaces is the main loss of ambient ozone migrating into indoor environments, which is critical for assessing human exposure to ozone. In this study, the surface removal rate due to ozone deposition on indoor surfaces in 14...

Cooking can release high concentrations of different air pollutants indoors, including particulate matter, polycyclic aromatic hydrocarbons (PAHs), and other gaseous pollutants such as volatile organic compounds (VOCs), oxides of carbon (COx ), and oxides of nitrogen (NOx ). Although some reviews have been conducted on emissions from cooking, they...

Many airborne infectious diseases can be transmitted via exhaled contaminants transported in the air. Direct exposure occurs when the exhaled jet from the infected person directly enters the breathing zone of the target person. Indirect exposure occurs when the contaminants disperse in the room and are inhaled by the target person. This paper prese...

Household air pollution generated from cooking is severe, especially for Chinese-style cooking. We measured the emission rates of multiple air pollutants including fine particles (PM2.5), ultrafine particles (UFPs), and volatile organic compounds (VOCs, including formaldehyde, benzene, and toluene) that were generated from typical Chinese cooking i...

Cooking is an important source of particulate matters in Chinese residences. In this study, 11 dishes of double cooked pork slices and 11 dishes of stir-fried chicken dices with hot chili were finished for 70 mins. Real-time concentrations of ultrafine and fine particles are monitored during and after cooking. The source strength was calculated bas...

Natural ventilation rate is an important parameter scaling the influence of outdoor air on in-door environment. In this study, a field measurement was conducted to understand the statis-tical distribution of natural ventilation rate in 28 residential buildings in Beijing, China. CO2 decay and nonlinear fitting methods were used. Some influential fa...

Occupants’ interactions with windows not only influence energy consumption but also influence indoor air quality of the buildings. There are many factors that affect occupants’ behaviors on windows opening and closing, such as the arrival of occupants, meteorological condition, indoor thermal environment and air quality. In this study, we tended to...

Sulfur and nickel have been widely used as tracers of outdoor PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 μm) in the United States and Europe; however, their feasibility as tracers has not been verified yet in China. We aim to verify whether sulfur or nickel could be used as a tracer element and, if not, to identify a suitable trac...

Vegetation, especially trees, is effective in reducing the concentration of particulate matter. Trees can efficiently capture particles, improve urban air quality, and may further decrease the introduction of outdoor particles to indoor air. The objective of this study is to investigate the effects of trees on particle distribution and removal arou...

Combustion processes related to industry, traffic, agriculture, and waste treatment and disposal increase the amount of outdoor ultrafine particles (UFPs), which have adverse effects on human health. Given that people spend the majority of their time indoors, it is critical to understand the penetration of outdoor UFPs through building cracks in or...

Window opening behavior has a vital influence on indoor air quality, thermal comfort, and energy consumption. In residential buildings, the window opening behavior of occupants may vary considerably owing to different indoor and outdoor environmental parameters and personal habits. In this study, we investigated the factors influencing the window o...

Computational fluid dynamics (CFD) is an important and effective tool to study the airflow field and contaminant distribution in aircraft cabins. The accuracy of numerical simulation using the CFD approach could be significantly affected by configurations of the inlet boundary conditions, turbulence model, etc. The core of this study was to assess...

Indoor airborne bioaerosols of outdoor origin play an important role in determining the exposure of humans to bioaerosols because people spend most of their time indoors. However, there are few studies focusing on indoor bioaerosols originating from outdoors. In this study, indoor versus outdoor size-resolved concentrations and particle asymmetry f...

Secondary organic aerosols (SOA) are products of the reaction of reactive organic gases (ROGs) and ozone. Most SOA are in the nanometer or submicron range, and thus SOA may be harmful to human health. Concentrations of ROGs may be high in newly decorated rooms, which may result in high SOA concentrations, especially during seasons with high ozone c...

Numerous epidemiological studies explored health risks attributed to outdoor particle pollution. However, a number of these studies routinely utilized ambient concentration as a surrogate for personal exposure to ambient particles. This simplification ignored the difference between indoor and outdoor concentrations of outdoor originated particles a...

Person to person droplets/particles or contaminant cross transmission is an important issue in ventilated environment, especially in the unidirectional ventilated protective isolation room (UVPIR) where the patient’s immune system is extremely low and easily infected. We simulated the dispersion process of the droplets with initial diameter of 100...

Wearable ionization air cleaners are compact in size and marketed for personal respiratory protection by removing air pollutants from users' breathing zone. In this study, ozone emission and particle removal rates of four wearable ionization air cleaners (namely, AC1 through AC4) were evaluated inside a 0.46 m3 stainless steel chamber. Continuous m...

Occupants’ interactions with windows influence both building energy consumption and exposure to airborne pollutants indoors. Occupants’ window opening behavior varies from region to region due to physical environmental factors and social reasons. China is now confronting severe atmospheric pollution, which may affect occupants’ window opening behav...

As one of the commonly found tracer gas to evaluate the air quality, high concentration of carbon dioxide (CO2) can cause exhaustion and drowsiness in enclosed spaces, especially those environments with very limited spaces, such as aircraft cabins. The phenomenon that CO2 concentration keeps high due to the eddy airflow in some certain zones is nam...

Infection is a major cause of death for the immunocompromised patients whose immune mechanisms are deficient. The most effective way of protecting these patients is the total environment protection such as protective isolation room (PIR). Unidirectional airflow ventilation is usually used in PIR. The supply air velocity in PIR can affect not only t...

Due to their low vapor pressure, semi-volatile organic compounds (SVOCs) can absorb onto other compartments in indoor environments, including settled dust. Incidental ingestion of settled dust-bound SVOCs contributes to the majority of daily non-dietary exposure to some SVOCs by human beings. With this pathway in mind, an integrated kinetic model t...

Indoor particles represent a combination of outdoor-originating particles, indoor-emitted particles and indoor secondary organic aerosol (SOA). It is important to distinguish the contributions of different particle sources to indoor PM2.5 (particulate matter with an aerodynamic diameter of 2.5 mm or less) because of the differences in concentration...

Following an extensive review of the literature, we further analyze the published data to examine the health effects of indoor exposure to particulate matter (PM) of outdoor origin. We obtained data on all-cause, cardiovascular, and respiratory mortality per 10 μg/m3 increase in outdoor PM10 or PM2.5; the infiltration factors for buildings; and est...