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The last two decades have witnessed rapid urbanization and economic growth accompanied by severe indoor air pollution of volatile organic compounds (VOCs) in China. However, indoor VOC pollution across China has not been well characterized and documented. This study is a systematic review of field measurements of eight target VOCs (benzene, toluene, xylenes, acetaldehyde, p-dichlorobenzene, butadiene, trichloroethylene, and tetrachloroethylene) in residences, offices, and schools in China from 2000 to 2021. The results show that indoor pollution of benzene, toluene, and xylenes has been more serious in China than in other countries. Spatiotemporal distribution shows lower indoor VOC levels in east and south-east regions and a declining trend from 2000 to 2021. Moving into a dwelling more than 1 year after decoration and improving ventilation could significantly reduce exposure to indoor VOCs. Reducing benzene exposure is urgently needed because it is associated with greater health risks (4.5 × 10

In this paper, a three-dimensional non-isothermal computational model for predicting indoor SVOC distribution is proposed, considering the effects of turbulence diffusion and suspended particles. The realizable k-e model is introduced for turbulent flow simulation in a room. The Euler-Euler method is adopted to deal with the gas-particle two-phase flow coupled problem. Inertia slip velocity and irreversible first-order absorption boundary are employed for more accurate prediction of particle motion. The simulated curve of outlet gas-phase di-2-ethylhexyl phthalate (DEHP) concentration with emission time is verified by available experimental data. The emission process of DEHP in a 15 m2 room in Beijing during 100 days with or without air cleaner is simulated by the developed model considering air leak through window and door gaps. It is found that if the air cleaner keeps on all the time during 100 days the gas-phase DEHP concentration in the room will tend to be uniform, while the emission process is far from equilibrium without an air cleaner even the emission lasts 100 days. Results also suggest that floor heating, decrease of particle concentration, weaken of heat transfer, enhancement of mass transfer, and air infiltration in window gap contribute to decrease DEHP concentration.

Exposure to volatile organic compounds (VOCs) indoors is thought to be associated with several adverse health effects. However, we still lack concentration-response (C-R) relationships between VOC levels in civil buildings and various health outcomes. For this paper, we conducted a systematic review and meta-analysis of observational studies to summarize related associations and C-R relationships. Four databases were searched to collect all relevant studies published between January 1980 and December 2017. A total of 39 studies were identified in the systematic review, and 32 of these were included in the meta-analysis. We found that the pooled relative risk (RR) for leukemia was 1.03 (95% CI: 1.01-1.05) per 1 μg/m

Negative ion air purifiers (NIAPs), as a less costly alternative to the HEPA filtration, have been increasingly deployed in China and potentially elsewhere. While reducing indoor concentrations of fine particulate matter (PM2.5 ), NIAPs generate massive amounts of negative ions that may be of health concern. We performed week-long interventions with NIAPs in the dormitories of 56 healthy college students living in Beijing. In a randomized order, each student underwent a true and a sham NIAP session. Cardiorespiratory outcomes were measured before and after each session. The use of true NIAPs reduced indoor PM2.5 concentrations significantly, while notably increased negative ion levels. Increases in PM2.5 and negative ion (NI) exposure were independently associated with increased urinary concentration of malondialdehyde, a biomarker of systemic oxidative stress, resulting in a null net effect of NIAP on malondialdehyde. Likewise, no significant net effects of NIAPs were observed for other outcomes indicative of lung function, vascular tone, arterial stiffness, and inflammation. Our findings suggest that negative ions, possibly along with their reaction products with the room air constituents, adversely affect health. The downsides do not support the use of NIAPs as a health-based mitigation strategy to reduce PM2.5 exposure, especially in residences with PM2.5 concentrations that are not extremely high.

Portable air cleaners are increasingly used in polluted areas in an attempt to reduce human exposure; however, there has been limited work characterizing their effectiveness at reducing exposure. With this in mind, we recruited forty-three children with asthma from suburban Shanghai and deployed air cleaners (with HEPA and activated carbon filters) in their bedrooms. During both 2-week filtration and non-filtration periods, low-cost PM2.5 and O3 air monitors were used to measure pollutants indoors, outdoors, and for personal exposure. Indoor PM2.5 concentrations were reduced substantially with the use of air cleaners, from 34 ± 17 to 10 ± 8 µg/m3 , with roughly 80% of indoor PM2.5 estimated to come from outdoor sources. Personal exposure to PM2.5 was reduced from 40 ± 17 to 25 ± 14 µg/m3 . The more modest reductions in personal exposure and high contribution of outdoor PM2.5 to indoor concentrations highlight the need to reduce outdoor PM2.5 and/or to clean indoor air in multiple locations. Indoor O3 concentrations were generally low (mean = 8±4 ppb), and no significant difference was seen by filtration status. The concentrations of pollutants and the air cleaner effectiveness were highly variable over time and across homes, highlighting the usefulness of real-time air monitors for understanding individual exposure reduction strategies.

During 2010-2012, we surveyed 40,010 3- to 6-year-old children in seven Chinese cities (Beijing, Taiyuan, Urumqi, Shanghai, Nanjing, Changsha, and Chongqing). Their parents reported information on household renovation, including the timing of renovation and the choice of materials for walls and floors in the child's room, and the incidence of their child's rhinitis. Multivariate and two-level (city-child) logistic regression analyses yielding adjusted odds ratios (AOR) with 95% confidence intervals were performed. Sensitivity analyses stratifying data for location and economic level were also performed. About 48.0% of the children had ever had allergic rhinitis, 41.2% had current allergic rhinitis, and 9.0% had had doctor-diagnosed rhinitis. Exposure to household renovation during early lifetime (birth to 1-year-old) had an AOR of 1.43 (1.04-1.9) for allergic rhinitis. The incidence of allergic rhinitis was significantly different in children exposed to different floor and wall covering materials. Floor or wall covering material composed of organic materials significantly increased the risk of childhood allergic rhinitis compared with tile flooring or lime wall covering. Oil paint had an AOR of 1.66 (1.28-2.14) for diagnosed rhinitis compared with lime wall covering. Adding new furniture the year before pregnancy was associated with an AOR of 1.18 (1.10-1.27) and 1.18 (1.11-1.25) for lifetime and current rhinitis. Solid wood or tiles/ceramic as floor materials, and using wallpaper, oil paint, or emulsion panels as wall materials were risk factors for doctor-diagnosed rhinitis. Sensitivity analyses showed that children living in southern or higher economic level China cities were more likely to have allergic rhinitis with household renovation.

A questionnaire survey on dermal symptoms and home environment was performed in eight Chinese cities (40 279 participants). Data on city level temperature, precipitation, PM10 , NO2, and gross domestic product (GDP) per capita were collected. In total, 2.2% had eczema, 2.4% facial erythema (FE) and 2.6% seborrheic dermatitis symptoms (SD). Higher temperature was associated with eczema (OR = 1.09). Higher GDP per capita was related to less SD. Higher PM10 was related to SD. Suburban living was protective for eczema (OR = 0.77) (vs. urban). Living in old buildings (built before 1991) was related to eczema (OR = 1.42). Living near heavily trafficked roads was related to FE (OR = 1.33) and SD (OR = 1.35). Having new furniture was related to all symptoms (OR = 1.26-1.47). Burning mosquito coils (OR = 1.37-1.57) and incense (OR = 1.33-1.37) were associated with eczema, FE, or SD. Presence of cockroaches and rats/mice was associated with FE or SD (OR = 1.31-1.40). Using air conditioner, daily cleaning and frequently exposing bedding to sunshine were protective (OR = 0.60-0.83). In conclusion, higher temperature, higher PM10 , urban living, living near heavily trafficked roads, old buildings, new furniture, burning mosquito coils and incense, and presence of cockroaches/rats/mice increased the risk of eczema, FE, or SD. Higher GDP, air conditioner, daily cleaning, and exposing bedding to sunshine were protective.

We surveyed 40 010 three- to six-year-old children in seven Chinese cities (Beijing, Taiyuan, Urumqi, Shanghai, Nanjing, Changsha, and Chongqing) during 2010-2012 so as to investigate possible links between home renovation and childhood eczema. Their parents responded to questions on home renovation and childhood eczema. Multivariate and two-level (city-child) logistic regression analyses yielding odds ratios with 95% confidence intervals were performed. Sensitivity analyses stratifying data for region, climate, and income level were also performed. The prevalences of childhood eczema in children with different floor and wall covering materials were significantly different and were significantly higher with home renovation during early lifetime. Exposure to synthetic materials significantly increased the risk of childhood eczema by 20%-25%. The risks (AOR, 95% CI) of current eczema among children in families with solid wood flooring and oil paint wall covering were 1.25 (1.04-1.49) and 1.35 (1.14-1.60), respectively. Home renovation during pregnancy was related to children's lifetime and current eczema.

Semivolatile organic compounds (SVOCs) are present in many indoor materials. SVOC emissions can be characterized with a critical parameter, y0 , the gas-phase SVOC concentration in equilibrium with the source material. To reduce the required time and improve the accuracy of existing methods for measuring y0 , we developed a new method which uses solid-phase microextraction (SPME) to measure the concentration of an SVOC emitted by source material placed in a sealed chamber. Taking one typical indoor SVOC, di-(2-ethylhexyl) phthalate (DEHP), as the example, the experimental time was shortened from several days (even several months) to about 1 day, with relative errors of less than 5%. The measured y0 values agree well with the results obtained by independent methods. The saturated gas-phase concentration (ysat ) of DEHP was also measured. Based on the Clausius-Clapeyron equation, a correlation that reveals the effects of temperature, the mass fraction of DEHP in the source material, and ysat on y0 was established. The proposed method together with the correlation should be useful in estimating and controlling human exposure to indoor DEHP. The applicability of the present approach for other SVOCs and other SVOC source materials requires further study.

UNLABELLED The initial emittable concentration of volatile organic compounds (VOC) is a key parameter not only in evaluating the 'green' degree of building materials but also in modeling their emission characteristics. Although the impact of temperature on initial emittable concentration is important, it has not been reported in the literature. Using the multi-emission/flush regression method we developed, the impact of temperature on the initial emittable concentration of formaldehyde in medium density board has been experimentally studied. It is observed that the initial emittable concentration increases significantly with increasing temperature. When the temperature rises by 25.4°C, it increases by about 507%. However, the initial emittable concentration at room temperature is far less than the value measured by the perforator method recommended by the Chinese National Standard GB/T 17657-1999, which measures the total concentration of formaldehyde in medium density board. This means most of formaldehyde in the building material cannot emit out at room temperature. The results will be very helpful in estimating the emission characteristics of building materials at different temperatures as well as for developing green building materials. PRACTICAL IMPLICATIONS Knowledge of initial emittable concentration is important for VOC emission prediction. According to our experimental study, the initial emittable concentration is heavily dependent on temperature, and this factor should be considered in dealing with heating or cooling process of building materials. The significant difference between the initial emittable concentration and total concentration suggests that the total concentration seems not appropriate for judging the pollution level of building materials.

A general model has been developed for analyzing the removal of volatile organic compounds (VOCs) by photocatalytic oxidation (PCO) reactors, taking into consideration of the photocatalytic (surface) reaction and the convective mass transfer coefficients including allowance for their spatial dependence. On this basis, a novel insight into VOC removal performance of PCO reactors is presented. The key parameter for evaluating PCO reactor VOC removal performance is the number of the mass transfer unit (NTU(m)), which is shown to be a simple linear product of three dimensionless parameters: the ratio of the reaction area to the cross-sectional area of the flow channel (A*), the Stanton number of mass transfer (St(m)), and the reaction effectiveness (eta). The A* represents the geometric and structural characteristic of a PCO reactor. The St(m) shows the synergistic degree of alignment between the fluid and mass flow fields, and reflects the convective mass transfer rate of the reactor. The eta, describes the relative intensity between the PCO reaction rate and the mass transfer rate. By using the relationship and the parameters, the influence of various factors on the VOC removal performance, the bottleneck for improving the performance and design of a PCO reactor can be determined. Three examples are used to illustrate the application of our proposed model. It is found that the VOC removal bottleneck is the reaction rate for honeycomb type reactor, while mass transfer rate for light-in-tube type reactor. With six fins the fractional conversion of a light-in-tube reactor increases about 70% relative to the one without any fins.Indoor air quality problem caused by volatile organic compounds (VOCs) have annoyed people for many years. Photocatalytic oxidation (PCO) appears to be a promising technique for destroying VOCs in indoor air. With the model and the novel insight presented in this paper, the influence of various factors on the VOC removal performance can be determined. And the bottleneck for improving the performance of a PCO reactor can be easily identified. These are helpful for designing high performance PCO reactors and optimizing their operative performance.