Yuexia Sun

Can commonly-used fan-driven air cleaning technologies improve indoor air quality? A literature review

Abstract Air cleaning techniques have been applied worldwide with the goal of improving indoor air quality. The effectiveness of applying these techniques varies widely, and pollutant removal efficiency is usually determined in controlled laboratory environments which may not be realized in practice. Some air cleaners are largely ineffective, and some produce harmful by-products. To summarize what is known regarding the effectiveness of fan-driven air cleaning technologies, a state-of-the-art review of the scientific literature was undertaken by a multidisciplinary panel of experts from Europe, North America, and Asia with expertise in air cleaning, aerosol science, medicine, chemistry and ventilation. The effects on health were not examined. Over 26,000 articles were identified in major literature databases; 400 were selected as being relevant based on their titles and abstracts by the first two authors, who further reduced the number of articles to 160 based on the full texts. These articles were reviewed by the panel using predefined inclusion criteria during their first meeting. Additions were also made by the panel. Of these, 133 articles were finally selected for detailed review. Each article was assessed independently by two members of the panel and then judged by the entire panel during a consensus meeting. During this process 59 articles were deemed conclusive and their results were used for final reporting at their second meeting. The conclusions are that: (1) None of the reviewed technologies was able to effectively remove all indoor pollutants and many were found to generate undesirable by-products during operation. (2) Particle filtration and sorption of gaseous pollutants were among the most effective air cleaning technologies, but there is insufficient information regarding long-term performance and proper maintenance. (3) The existing data make it difficult to extract information such as Clean Air Delivery Rate (CADR), which represents a common benchmark for comparing the performance of different air cleaning technologies. (4) To compare and select suitable indoor air cleaning devices, a labeling system accounting for characteristics such as CADR, energy consumption, volume, harmful by-products, and life span is necessary. For that purpose, a standard test room and condition should be built and studied. (5) Although there is evidence that some air cleaning technologies improve indoor air quality, further research is needed before any of them can be confidently recommended for use in indoor environments.

On associations between housing characteristics, dampness and asthma and allergies among children in Northeast Texas

A cross-sectional study on the home environment and children’s health in Northeast Texas was carried out in 2008–2009. Two thousand eight hundred and nineteen (2,819) parents of children (1–8 years) reported their housing characteristics, home interior surface materials, dampness and children’s health status. The response rate was 71%. Health outcomes studied were wheeze, dry cough, rhinitis, eczema in the last 12 months and diagnosed asthma and hay fever. Dampness was significant risk factor for wheeze and rhinitis with adjusted odds ratio (AOR) 1.3–1.7. Mould/damp spot, condensation and suspected moisture problems were more commonly reported in buildings with flat roof and pier/beam foundation in hot and humid Northeast Texas. Compared to single family houses, trailers were associated with more dampness, consequently a significant increased prevalence of asthma (AOR 1.5 with 95% confidence interval (CI) 1.0–2.3), rhinitis (AOR 1.4, 95% CI 1.0–2.0) and hay fever (AOR 1.5, 95% CI 1.1–2.1). Central air-conditioning system, which re-circulates indoor air, was associated with less dampness problems. However, an increment trend of allergic symptoms was found in homes with air-conditioning system, especially for rhinitis (AOR 1.6, 95% CI 1.1–2.2). Carpet as floor covering and laminated panel as wall covering were associated with rhinitis (AOR 1.6, 95% CI 1.0–2.5) and wheezing (AOR 4.7, 95% CI 1.8–12.7), respectively.

Associations of gestational and early life exposures to ambient air pollution with childhood respiratory diseases in Shanghai, China: A retrospective cohort study

BACKGROUND Associations of ambient air pollutants with respiratory health are inconsistent. OBJECTIVES We analyzed the associations of gestational and early life exposures to air pollutants with doctor-diagnosed asthma, allergic rhinitis, and pneumonia in children. METHODS We selected 3358 preschool children who did not alter residences after birth from a cross-sectional study in 2011-2012 in Shanghai, China. Parents reported childrens respiratory health history, home environment, and family lifestyle behaviors. We collected daily concentrations of sulphur dioxide (SO2), nitrogen dioxide (NO2), and particulate matter with an aerodynamic diameter ≤10μm (PM10) during the childs total lifetime (2006-2012) for each district where the children lived. We analyzed the associations using logistic regression models. RESULTS After adjusting for covariates and the other studied pollutants, we found that exposure to NO2 (increment of 20μg/m(3)) during the first year of life was significantly associated with asthma [odds ratio (OR)=1.77; 95% confidence interval (CI): 1.29-2.43] and allergic rhinitis (OR=1.67; 95% CI: 1.07-2.61). Exposure to NO2 during gestation, the first two and three years, and over total lifetimewas all consistently associated with increased odds of allergic rhinitis. Quartiles of NO2 concentration during different exposure periods showed a slight dose-response relationship with the studied diseases. These diseases had significant associations with pollutant mixtures that included NO2, but had no significant association with exposures to SO2 and PM10 individually or in mixtures. CONCLUSIONS Gestational and early life exposures to ambient NO2 are risk factors for childhood respiratory diseases.

Early Daycare Attendance Increase the Risk for Respiratory Infections and Asthma of Children

Objectives: To study the impact of daycare attendance on airways infections and “allergic” symptoms of children aged 1–8 years in Northeast Texas. Methods: Self-administrated questionnaires were distributed to parents through Women, Infants and Children offices, daycare centers, elementary schools, clinic centers, hospitals, and churches. The health outcomes consisted of “allergic” symptoms, and respiratory tract disorders. Questions on child care included; type of daycare settings (proxy for the number of children in daycare), time spent at daycare centers per week, and age of entry to a daycare center. Results: A total of 3766 children participated in this study, giving a response rate of 71%. Daycare attendance was associated with more frequent respiratory tract infections and “allergic” symptoms, compared to home care. A dose–response relationship between time spent at daycare centers and prevalence of respiratory tract disorders and asthma and allergies was observed. Earlier age exposure at daycare centers was a risk factor for rhinitis up to 7–8 years. Conclusions: Daycare attendance had a substantial negative influence on health status of children aged 1–8 years in Northeast Texas.

Associations of gestational and early life exposures to ambient air pollution with childhood atopic eczema in Shanghai, China

Whether ambient air pollution is associated with childhood atopic eczema is controversial. In this paper, we selected 3358 preschool children who had not altered residences since pregnancy from a cross-sectional study during 2011-2012 in Shanghai, China, and obtained parent-reported data regarding childhood atopic eczema using an improved ISAAC questionnaire. We recorded daily concentrations of SO2, NO2, and PM10 throughout the childs lifetime (2006-2012), and calculated period-averaged concentrations for each district where the child lived to represent the childs exposure levels of these pollutants during different periods. In the multiple logistic regression analyses adjusted for potential confounders as well as for the other pollutants in the same periods, childhood atopic eczema was significantly associated with increments of NO2 in the approximate interquartile range (20μg/m3) during gestational period (adjusted OR, 95% CI for eczema lifetime-ever: 1.80, 1.29-2.49; for eczema in the year prior to the survey: 2.32, 1.57-3.43) and during the first year of life (2.00, 1.40-2.84; 2.16, 1.43-3.28). Exposure to elevated NO2 in the first two years, three years and total lifetime, as well as exposure to mixtures containing NO2 in each of these periods, were consistently associated with increased likelihood of childhood eczema. The highest odds ratios were found between exposure to a mixture of SO2 and NO2 during total lifetime (increment: 35μg/m3) and childhood eczema (adjusted OR, 95% CI: 2.80, 1.75-4.48; 3.50, 1.98-6.19). No significant associations were found between childhood eczema and ambient SO2 and PM10 individually or in mixtures. This study indicates that gestational and lifetime exposures to ambient NO2 are risk factors for atopic eczema in childhood. Exposure to ambient SO2 and PM10 may enhance the effect of NO2 exposure on childhood eczema.

High pneumonia lifetime-ever incidence in Beijing children compared with locations in other countries, and implications for national PCV and Hib vaccination

Objectives To compare the proportion of Beijing children who have ever had pneumonia (%Pneumonia) to those in other locations, and to estimate by how much national vaccine coverage with Pneumococcal Conjugate Vaccine (PCV) and Haemophilus Influenzae Type b (Hib) could reduce Beijing %Pneumonia. Methods %Pneumonia was obtained for each age group from 1 to 8 years inclusive from 5,876 responses to a cross-sectional questionnaire. Literature searches were conducted for world-wide reports of %Pneumonia. Previous vaccine trials conducted worldwide were used to estimate the pneumococcal (S. pneumoniae) and Hib (H. influenzae) burdens and %Pneumonia as well as the potential for PCV and Hib vaccines to reduce Beijing children’s %Pneumonia. Findings The majority of pneumonia cases occurred by the age of three. The cumulative %Pneumonia for 3–8 year-old Beijing children, 26.9%, was only slightly higher than the 25.4% for the discrete 3 year-old age group, similar to trends for Tianjin (China) and Texas (USA). Beijing’s %Pneumonia is disproportionally high relative to its Gross National Income (GNI) per capita, and markedly higher than %Pneumonia in the US and other high GNI per capita countries. Chinese diagnostic guidelines recommend chest X-ray confirmation while most other countries discourage it in favor of clinical diagnosis. Literature review shows that chest X-ray confirmation returns far fewer pneumonia diagnoses than clinical diagnosis. Accordingly, Beijing’s %Pneumonia is likely higher than indicated by raw numbers. Vaccine trials suggest that national PCV and Hib vaccination could reduce Beijing’s %Pneumonia from 26.9% to 19.7% and 24.9% respectively. Conclusion National PCV and Hib vaccination programs would substantially reduce Beijing children’s pneumonia incidence.

Thermodynamic analysis of desiccant wheel coupled to high-temperature heat pump system

A high-temperature heat pump coupled with a desiccant wheel system possesses superiority among the various hybrid desiccant cooling systems due to its compact configuration and especially its ability to make full use of both heating and cooling from the condenser and evaporator of the high-temperature heat pump to achieve the function of self-regeneration. This study investigates the performance of high-temperature heat pump coupled with a desiccant wheel system using the exergy analysis method; the performance is also compared with the hybrid desiccant cooling system with an electric heater. Two improved configurations for the proposed system are also suggested that are beneficial for irreversibility reduction. The results show that high-temperature heat pump coupled with a desiccant wheel system gets rid of the large exergy destruction of the electric heater and then obtains an exergy efficiency that is 19% higher than the hybrid desiccant cooling system. The improved configuration for the proposed system integrating the isothermal dehumidification of a two-stage desiccant wheel and matched heat exchangers is in favor of reducing the exergy input. It is found that the exergy input is decreased by 30.3%, and the cooling exergy efficiency is increased by 46.9%.

Dampness problems in Tianjin dwellings: A cross-sectional study of associations with building characteristics and lifestyles:

This study investigated the association of building characteristics and occupant behaviours with building dampness indicators. Data were from a cross-sectional study in urban Tianjin and rural Cangzhou, China, from 2013 to 2014. We studied two fundamental types of Chinese dwellings: bungalows typical of rural locales and apartments in low- and high-rise buildings typical of urban settings. Occupants of bungalows reported more dampness indicators than apartment dwellers. Risk factors for one or more dampness indicators included natural ventilation without fans, older dwellings and coal stove or Kang heating system (a brick bed installed in the bedroom for heating and sleeping). All these factors were typical of bungalows, which generally used older building technologies including non-insulated external walls, wooden frame windows, electric fans for cooling and no exhaust fan ventilation. Occupant behaviours that decreased the risk for dampness indicators included frequent window opening and daily cleaning, regardless of the type of dwelling. Indoor dampness was highly correlated with mouldy and humid odour, and paradoxically (although not a new finding) with the perception of air dryness.

Pet keeping in childhood and asthma and allergy among children in Tianjin area, China

This study aims to find out the relationship between pet keeping in childhood and asthma and allergy among children aged 0–8 years old in Tianjin, China. Parental or guardians reports of 7360 children were analyzed. 1490 (21.6%) families kept pets at the time of the survey (current), among them 4.0% cats, and 14.7% dogs. For the first year of life of children (early), 1196 (18.4%) families kept pets, and among them 3.2% cats, and 13.7% dogs. Exposure to a pet in early childhood significantly increased the risk of current wheeze, current dry cough, and diagnosed rhinitis. 17.9% of parents reported an avoidance behavior, i.e., had removed or refrained a pet due to asthma or allergy in the family. After adjustment for avoidance behavior, the negative effect of pet keeping on children’s health became even more obvious, with e.g. an AOR of 3.37 (1.58–7.19) for diagnosed asthma, 3.60 (2.07–6.27) for diagnosed rhinitis, 1.92 (1.31–2.81) for diagnosed eczema. A dose-response relationship between pet keeping at current and current wheeze, current eczema and diagnosed eczema was found. In conclusion, pet exposure in early life of children in Tianjin is a risk factor for asthma and allergies among children aged 0–8 years old.

Lifetime-ever pneumonia among pre-school children across China – Associations with pre-natal and post-natal early life environmental factors

Background: Biomass burning is associated with childhood pneumonia but few studies exist on other indoor factors. Aim: To study pneumonia in relation to pre‐natal and post‐natal exposure among children across China. Methods: Children (3–6 y) (n = 39,782) from randomized day care centres in seven cities in China. Information on pneumonia and pre‐natal and post‐natal exposure to home environment factors were assessed by a parental questionnaire. Life‐time outdoor temperature and GDP per capita were assessed on city level. Associations were calculated by multilevel logistic regression adjusting for fourteen co‐variates. Results: Totally 32.0% had ever had pneumonia diagnosed by a physician. Children of farmer mothers (OR = 0.65), with breastfeeding (OR = 0.91) and living in rural (OR = 0.85) or suburban (OR = 0.90) areas had less pneumonia. Buying new furniture one year before conception (OR = 1.11) and after first year of life (OR = 1.10) increased the risk. Redecoration one year before conception (OR = 1.20), during pregnancy (OR = 1.18) and after first year of life (OR = 1.17) increased pneumonia risk. Children with mould (OR = 1.17), window pane condensation (WPC) (OR = 1.20) and mould odour (OR = 1.15) at home at birth only had a higher risk of pneumonia. Similar associations were seen for dampness and mould in the current home. Children in the oldest and newest homes had less pneumonia. Cockroaches (OR = 1.08), mosquitos or flies in the current home (OR = 1.18), an exhaust fan in the bathroom (OR = 1.10) and higher economic development level, measured as GDP per capita on city level (OR 1.11 per 10,000 RMB/year) were associated with childhood pneumonia. Conclusions: Perinatal and postnatal exposure to mould, mould odour and window pane condensation at home can be early life risk factors for childhood pneumonia in China. Moreover, pre‐natal and post‐natal exposure to chemical emissions from new furniture and renovation could increase the risk of childhood pneumonia. Breastfeeding, farm exposure, and living in rural or suburban areas could be protective. HighlightsChildhood pneumonia can be influenced by prenatal and perinatal indoor exposure.Mould and window condensation at birth is a risk factor for childhood pneumonia.Prenatal exposure to redecoration and new furniture can increase the risk.Cockroaches, mosquitos and flies are other risk factors in the home environment.Farm exposure, breastfeeding and suburban or rural environment can be protective.