The effect of ventilation strategies of child care centers on indoor air quality and respiratory health of children in Singapore

This paper reports the effects of ventilation strategies on indoor air quality (IAQ) and respiratory health of children within 104 child care centers (CCCs) in a hot and humid climate. The CCCs were categorized by ventilation strategies: natural (NV), air-conditioned and mechanically ventilated (ACMV), air-conditioned using split units (AC), and hybrid (NV and AC operated intermittently). The concentration levels of IAQ parameters in NV CCCs are characterized by the influence of the outdoors and good dilution of indoor pollutants. The lower ventilation rates in air-conditioned CCCs result in higher concentrations of occupant-related pollutants but lower outdoor pollutant ingress. This study also revealed lower prevalence for most asthma and allergy, and respiratory symptoms in children attending NV CCCs. In multivariate analyses controlled for the effects of confounders, the risk of current rhinitis among children is significantly higher if they attend mechanically ventilated CCCs compared to NV CCCs. Air-conditioned CCCs were also associated with higher adjusted prevalence ratio of severe phlegm and cough symptoms and lower respiratory illness. Finally, children attending CCCs with hybrid ventilation are at high risk for almost all the respiratory symptoms studied. PRACTICAL IMPLICATIONS: This large field study indicates that different ventilation strategies employed by child care centers can cause significant variations in the indoor air quality and prevalence of asthma, allergies and respiratory symptoms of attending children. The higher prevalence rates of allergic and respiratory symptoms among young children, whose immune system is still under-developed, in child care centers, whether fully or partially air-conditioned, suggest that ventilation and plausible growth and propagation mechanisms of allergens and infectious agents be further investigated.     

Two Moldy Day-care Centers: a Follow-up Study of Respiratory Symptoms and Infections

Abstract The aim was to study the respiratory symptoms among children exposed to indoor air molds in a day-care environment in Finland. Two day-care centers with a mold problem and two reference day-care centers were included in the study and the health data of the children were collected with a follow-up study of two periods. A total of 229 children 3-7 years old attended the day-care centers. During the first follow-up period, the children in the two day-care centers with mold problems had a significantly increased risk of sore throat, purulent and non-purulent nasal discharge, nasal congestion, hoarseness and common cold. During the second follow-up period, a significantly increased risk of purulent nasal discharge, nasal congestion, hoarseness and cough was observed. Upper respiratory tract symptoms, at least once during the study period, were more prevalent among the children attending mold-problem day-care centers. The mold-exposed children had such symptoms repeatedly or the symptoms were prolonged. In conclusion, in the mold-problem day-care centers, overall morbidity for respiratory symptoms and for common cold increased in comparison with the reference day-care centers.     

Day care center characteristics and children's respiratory health

Day care centers provide an important exposure arena with potential harmful health effects for children. This study has linked health effect data from a survey among 942 3-5-year-old Oslo children with information on day care center characteristics collected during inspection of the 175 day care centers these children attended. The aim of the study was to estimate associations between dampness problems and other building characteristics and several respiratory health outcomes. Dampness problems (sign of molds, water leakage, damage to floor/wall) were observed in 51% of the day care centers. In multiple logistic regression analyses none of the studied symptoms and diseases (nightly cough, blocked or runny nose without common cold, wheeze, heavy breathing or chest tightness, the common cold, tonsillitis/pharyngitis, otitis media, bronchitis, pneumonia, asthma, and allergic rhinitis) were systematically associated with dampness problems or type of ventilation in day care centers. None of the studied indicators of day care center exposures were found to have a clear effect on day care children's respiratory health. Even so this study does not rule out negative health effects of day care center exposures. The study demonstrates that population-based studies of these relations are demanding with regard to assessment of exposure and health outcomes. PRACTICAL IMPLICATIONS: Simple and easy-to-register indicators of exposures like dampness problems and type of ventilation assessed in 175 day care centers were not related to respiratory health among 3-5-year-old Norwegian children attending the day care centers. The study does not rule out negative health effects of day care center exposures, but demonstrates methodological challenges needed to be addressed in studies of health effects of the day care environment.     

Investigation of different approaches to reduce allergens in asthmatic children's homes--the Breath of Fresh Air Project, Cornwall, United Kingdom

During 2001 to 2004, a study was conducted to assess the indoor environmental and health impact of installing allergen-reducing interventions in the homes of asthmatic children. Based on the results of a pilot study, to determine an intervention that would provide improved symptom scores and a reduction in house dust mite allergen (Der p 1), mechanical ventilation and heat recovery (MVHR) systems were installed in 16 homes. Environmental and respiratory health assessments were conducted before and after the installation of the MVHR systems. The results indicated that the installation of MVHR systems reduced Der p 1 concentrations in living room carpets and mattresses. There were significant reductions in symptom scores for breathlessness during exercise, wheezing, and coughing during the day and night. Although, there was not a parallel control group for the main study, the lack of change in the pilot study control group (who did not receive an intervention), indicated that the changes in symptom scores were in part to do with the intervention. Larger scale trials are needed to determine the efficacy of MVHR systems in homes to improve indoor air quality and reduce asthma symptoms.     

Association between ventilation rates in 390 Swedish homes and allergic symptoms in children

The aim of the study was to test the hypothesis that a low-ventilation rate in homes is associated with an increased prevalence of asthma and allergic symptoms among children. A total of 198 cases (with at least two of three symptoms: wheezing, rhinitis, eczema) and 202 healthy controls, living in 390 homes, were examined by physicians. Ventilation rates were measured by a passive tracer gas method, and inspections were carried out in the homes. About 60% of the multi-family houses and about 80% of the single-family houses did not fulfill the minimum requirement regarding ventilation rate in the Swedish building code (0.5 air changes per hour, ach). Cases had significantly lower ventilation rates than controls and a dose-response relationship was indicated. PRACTICAL IMPLICATIONS: A low-ventilation rate of homes may be a risk factor for allergies among children. Families with allergic children should be given the advice to have good ventilation in the home. In investigations, of associations between environmental factors and allergies, the air change rate in homes has to be considered.     

Experimental investigation of reduced-mixing personal ventilation jets

This paper presents an investigation of the design and performance characteristics of personalized ventilation (PV) systems that, in combination with general ventilation, deliver high quality air to the breathing zone (BZ) with no more clean air supply than indicated by ANSI/ASHRAE 62.1-2004, while satisfying acceptable ergonomic and aesthetic considerations. Under these conditions, the energy used for conditioning the clean air will not exceed that of a conventional ventilation system. We introduce a novel PV nozzle that achieves high BZ air quality with a small fraction of the clean air indicated by the ANSI/ASHRAE Standard. Tracer gas experimental results presented in this paper demonstrate the advantages of the novel nozzle relative to conventional PV nozzles. The results show that, at a PV clean air supply of only 2.4 l/s, the new nozzle achieves a BZ ventilation effectiveness close to 7 versus less than 2 for a conventional nozzle delivering the same amount of clean air. A companion paper presents a computational analysis of the same concept, validated against the experimental results of the present paper.     

Do classroom ventilation rates in California elementary schools influence standardized test scores? Results from a prospective study

Limited evidence has associated lower ventilation rates (VRs) in schools with reduced student learning or achievement. We analyzed longitudinal data collected over two school years from 150 classrooms in 28 schools within three California school districts. We estimated daily classroom VRs from real‐time indoor carbon dioxide measured by web‐connected sensors. School districts provided individual‐level scores on standard tests in Math and English, and classroom‐level demographic data. Analyses assessing learning effects used two VR metrics: average VRs for 30 days prior to tests, and proportion of prior daily VRs above specified thresholds during the year. We estimated relationships between scores and VR metrics in multivariate models with generalized estimating equations. All school districts had median school‐year VRs below the California VR standard. Most models showed some positive associations of VRs with test scores; however, estimates varied in magnitude and few 95% confidence intervals excluded the null. Combined‐district models estimated statistically significant increases of 0.6 points (P = 0.01) on English tests for each 10% increase in prior 30‐day VRs. Estimated increases in Math were of similar magnitude but not statistically significant. Findings suggest potential small positive associations between classroom VRs and learning.     

A case study of sub-slab depressurization for a building located over VOC-contaminated ground

A sub-slab depressurization system for protecting indoor air quality in buildings located over VOC-contaminated ground is described. Included in the design is a means of assessing the performance of the protection measures during the lifetime of the building. A case study is presented of the sub-slab depressurization system implemented in two renovated historic buildings located at the site of an old gas works facility with extensive tar and PAH contamination in the soil. Measurements of under pressure under the slab and airflow rates in the sub-floor exhaust ventilation ducts from performance checks both immediately after the systems were installed and then 2 years later demonstrated that the protection measures in each building functioned as planned. VOC measurements in indoor air in the buildings during the two performance checks suggested that the air quality in the buildings was not adversely affected by the contamination in the soil.     

Indoor air pollution from biomass combustion and respiratory symptoms of women and children in a Zimbabwean village

Rural areas of developing countries are particularly reliant on biomass for cooking and heating. Women and children in these areas are often exposed to high levels of pollutants from biomass combustion that is associated with a range of respiratory symptoms. Domestic exposure to carbon monoxide (CO) and respirable particles (RSPs) in association with respiratory symptoms among women and children in Zimbabwe was investigated in 48 households. Health status and household characteristics were also recorded. In this study, indoor levels of CO and RSPs exceeded World Health Organization (WHO) air quality guidelines in over 95% of kitchens. The level of indoor air pollutants was associated with the area of kitchen windows and the length of cooking time combined with the level of fire combustion. Prevalence of respiratory symptoms was 94% for women and 77% for children. In addition, women reporting respiratory symptoms were exposed to higher levels of RSPs when compared with those reporting no respiratory symptoms. The study results indicated that levels of indoor air pollutants in rural Zimbabwe may contribute to respiratory symptoms in both women and children. PRACTICAL IMPLICATIONS: Levels of respirable particles and carbon monoxide in kitchens in rural Zimbabwe are unacceptably high and measures to reduce levels should be undertaken. Based on the study findings, recommendations for increasing the area of kitchen windows may be considered as a practical method of reducing indoor air pollutants in rural Zimbabwe.     

Natural ventilation of indoor spaces while minimizing heat losses: Theoretical and experimental investigation

Limiting heat losses during ventilation of indoor building spaces has become a basic aim for architects, particularly since the oil crisis of 1970. Much experience has been gained in terms of ventilation of indoor spaces. Nevertheless, due to the complex applications, attempts to create a theoretical base for solving the problems related to the issue are limited, especially determining the minimum ventilation period required within a designated space. In this paper we have approached this matter, both theoretically and experimentally. The conclusion we reached was that controlled ventilation of spaces through vent holes that successively open and close at regular time intervals can limit the excessive circulation of air masses, which in turn limits heat losses.     

Cross-Sectional Study On,The Health Effects Of Gas Cooking Stoves In Japan

In order to investigate the health effects of NO₂, emitted from gas cooking stoves, we compared the prevalence of several respiratory symptoms for people living in gas homes (homes with gas cooking stoves) with those for people living in electric homes (homes with electric cooking stoves) in Japan. The survey was conducted in September 1985, with a self-administered questionnaire. No statistically significant differences were found for several respiratory symptoms between electric homes and gas homes among both children (adjusted odds ratios: 0.64–1.80) and their parents (odds ratios: 0.39–0.94). This work represents a preliminary study in Japan. A longitudinal study should be conducted to further investigate the health effects associated with gas cooking stoves.     

Indoor Climate and the Performance of Ventilation in Finnish Residences

The purpose of the study was to gather information about the actual ventilation and indoor air quality and to evaluate the differences between houses and apartments with different ventilation systems. A sample of 242 dwellings in the Helsinki metropolitan area was studied over periods of no weeks during the 1988-1989 heating season. The mean air-exchange rates had a high variation (average 0.52 l/h, range 0.07-1.55 l/h). The ASHRAE minimum value of 0.35 l/h was not achieved in 28% of the dwellings. The air-exchange rates were significantly her in the houses than in the apartments (averages 0.45/0.64 l/h, p < 0.001); in the natural ventilation systems they, were slightly her than in the mechanical systems. The average temperature in the bedrooms was approximately 22 °C (range 18–27 °C), slightly but significantly higher in the apartment than in the houses. The average dust depositions were higher in the balanced ventilation systems than in the other systems. The median radon concentration was 82 Bq/m³ (range 5-866 Bq/m³); the Finnish target value of 200 Bq/m³ was exceeded in 17% of the houses but in none of the apartment. The measurements indicate that the indoor air quality in Finnish dwellings is not always satisfactory with reference to human health and comfort.     

Indoor Climate and Indoor Air Quality in Residential Buildings

In buildings which were built within the last 15 to 20 years, or which have been retrofitted, and which do notfeature a mechanical ventilation system, air changes between 0.01 h^?1 and 0.5 h^?1 were measured while windows were closed. In the bedrooms of such buildings, when doors and windows were closed, CO₂ concentrations of up to 4300 ppm were measured whereby the 1500 ppm limit was often exceeded. Simulation calculations and diverse measurements using different door positions with simultaneously closed windows have shown that with the door open more than 10 cm, and a minimal air exchange in the whole of an apartment of 0.1 h^?1, a CO₂ concentration of I500 ppm was not or was only insignifiantly exceeded even after 10 hours. Investigations in a dwelling fined with a mechanical ventilation system have shown that air quality and the indoor climate parameters were in an optimal range.     

Respiratory responses to diverse indoor combustion air pollution sources

Diverse indoor combustion sources contribute to the indoor air environment. To evaluate the effect of these sources on human respiratory health, we examined associations between respiratory conditions and household factors in the 2360 children's fathers (mean = 38.4 years old) and associations between lung function and household factors in 463 primary school children (mean = 8.3 years old) from Wuhan, China. Factor analysis developed new uncorrelated 'factor' variables. Unconditional logistic regression models or linear regression models, controlling for important covariates, estimated the respiratory health effects. Coal smoke derived from home heating ('heating coal smoke') was associated with high adult reporting of persistent cough, persistent phlegm, and wheeze. Cooking coal smoke was associated with physician-diagnosed adult asthma and decreased forced vital capacity (FVC), and forced expiratory volume at 1 s (FEV(1)) in children. The presence of any home cigarette smoker was associated with more reports of persistent cough, persistent phlegm, cough with phlegm, and bronchitis. Our study suggests that in Wuhan, there may be independent respiratory health effects of different indoor combustion sources and their exposure factors for these study populations. PRACTICAL IMPLICATIONS: We conclude that multiple indoor air pollution sources could have adverse respiratory health effects on both children and middle-aged men in the city of Wuhan, China. These results may have implications for the Wuhan local government, the Chinese government, or other related organizations in efforts on protecting public health through regulation of indoor air pollution from indoor combustion sources.     

Demand-Controlled Ventilation – an Application to Auditoria

This paper is based on field measurements in auditoria, carried out in Norway and in Switzerland. In both cases carbon dioxide (CO₂ was chosen as the relevant indicator to establish ventilation demand. Investigations in Norway focus on the aspects of airflow, patterns, ventilation efficiency and air quality. Intensive monitoring and numerical calculations with the computer code KAMELEON were performed. The Swiss project places more emphasis on impacts of demand control on energy consumption and occupant response. The results of the fild measurements, of the questioning of occupants, as well as of simulations which were carried out with the simulation code TRNSYS are presented. Results show that demand control with CO₂, as indicator for ventilation demand can maintain an acceptable indoor climate while allowing substantial energy savings. These investigations were conducted as part of the IEA (International Energy Agency) research programme “Annex 18: Demand Controlled Ventilating Systems”.