THE ROLE OF VENTILATION AND HVAC SYSTEMS FOR HUMAN HEALTH IN NONINDUSTRIAL INDOOR ENVIRONMENTS. A SUPPLEMENTARY REVIEW BY EUROVEN GROUP

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1 Proceedings: Indoor Air 2002 THE ROLE OF VENTILATION AND HVAC SYSTEMS FOR HUMAN HEALTH IN NONINDUSTRIAL INDOOR ENVIRONMENTS. A SUPPLEMENTARY REVIEW BY EUROVEN GROUP P Wargocki 1*, J Sundell 1, W Bischof 2, G Brundrett 3, PO Fanger 1, F Gyntelberg 4, SO Hanssen 5, P Harrison 6, A Pickering 7, O Seppänen 8 and P Wouters 9 1 International Centre for Indoor Environment and Energy, Technical University of Denmark 2 FriedrichSchillerUniversität Jena, Germany 3 United Kingdom 4 Bispebjerg Hospital, Denmark 5 Norwegian University of Science and Technology 6 MRC Institute for Environment and Health, United Kingdom 7 Wythenshawe Hospital, United Kingdom 8 Helsinki University of Technology, Finland 9 Belgian Building Research Institute, Belgium ABSTRACT A continuation of the earlier work of the multidisciplinary group of European scientists, EUROVEN, is presented. The group has previously concluded that increased ventilation rates in indoor nonindustrial environments are strongly associated with improved comfort and health and may be associated with increased productivity, and that airconditioning systems may increase the risk of sick building syndrome (SBS) symptoms. Taking these findings into account, the group has elaborated 35 hypotheses on the role of ventilation and HVAC systems in non industrial indoor environments with regard to human health; 108 peerreviewed papers have been reviewed among which 74 supported or refuted the hypotheses. The group concluded that increasing outdoor air supply rates is necessary for dilution/removal of pollutants generated indoors (including allergens), and that improper design, functioning and maintenance of ventilation and airconditioning systems, as well their intermittent operation, may be potential reasons for health problems of people staying indoors. INDEX TERMS HVAC; Offices; Residences; Ventilation; Review; EUROVEN INTRODUCTION To create a multidisciplinary forum for an adequate communication of scientific results between different disciplines, the European Multidisciplinary Scientific Network on indoor Environment and Health concerning associations between ventilation and health, EUROVEN, was established in the year 2000 by scientists with expertise in medicine, epidemiology, toxicology and engineering. They reviewed the peerreviewed scientific literature concerning ventilation and health in nonindustrial indoor environments and following the plenary discussions, used the results of the review to formulate a consensus statement. As a result of the work in the year 2000, the group concluded that ventilation is strongly associated with comfort (perceived air quality) and health (Sick Building Syndrome (SBS) symptoms, inflammation, infections, asthma, allergy, shortterm sick leave), and that an association between ventilation and productivity (performance of office work) is indicated (Wargocki et al., 2002). Additionally, the group concluded that increasing outdoor air supply rates in * Contact author pw@mek.dtu.dk 33

2 Proceedings: Indoor Air 2002 nonindustrial environments improves perceived air quality; that outdoor air supply rates below 25 L/s per person increase the risk of SBS symptoms, increase shortterm sick leave and decrease productivity among occupants of office buildings; and that ventilation rates above 0.5 h 1 in homes reduce infestation of house dust mites in Nordic countries. Finally the group concluded that the literature indicates that in buildings with airconditioning systems there may be an increased risk of SBS symptoms compared with naturally or mechanically ventilated buildings. Taking these conclusions into account, the group continued its work in the year 2001, the objective being to search for scientific evidence on the possible causes for the observed associations, in particular to discuss why people have fewer health and comfort effects in well ventilated buildings, and what the reasons are behind the association between airconditioning and health effects. This paper describes the results of this work. METHODS Hypotheses describing the role of ventilation and HVAC systems for human health in indoor non industrial environments were elaborated during a plenary meeting of the EUROVEN group. The literature supporting or refuting the hypotheses was gathered by searching through databases and selecting papers from peerreviewed scientific journals. Abstracts from several thousand papers were screened, and 108 papers were selected for the final review by the 9 scientists, members of EUROVEN. Each selected paper was reviewed by 2 scientists and was classified independently by each reviewer as providing sufficient information to support or refute any of the elaborated hypotheses, or as inconclusive or irrelevant. During the plenary meeting, the EUROVEN group decided on the final classification and used it to formulate a consensus statement. RESULTS Of the 108 papers reviewed, 74 papers were judged to support or refute any of the elaborated hypotheses (Table 1). Of the 35 hypotheses elaborated, 17 were addressed by the reviewed papers (Table 2) and 18 were not (Table 3). As many as 26 papers suggested that the HVAC system creates environments favourable for survival and reproduction of biological agents that can be introduced indoors. Twelve papers showed that ventilation introduces air pollutants originating within the HVAC system. Ten papers indicated that ventilation introduces outdoor air pollutants, but at the same time 6 papers suggested the opposite. According to 10 papers, existing filters reduce the concentration of particulate matter indoors, but in 3 papers the opposite was reported. According to 10 papers, the lack of maintenance of HVAC systems, and according to 6 improper operation of HVAC systems, are important factors that may result in an increased prevalence of symptoms. DISCUSSION The main results of the review are not original: increasing outdoor air supply rates removes/dilutes indoor pollutants, and improper maintenance and functioning of HVAC systems are potential causes of SBS symptoms. However, they provide a scientific support to facts that are well known by the ventilation community. Still, it is surprising to note that in spite of these obvious reasons, many occupants of numerous nonindustrial buildings with HVAC systems suffer from various health and comfort problems (e.g., Bluyssen et al., 1996; Fisk et al., 1993). The present results thus form a scientificbased incentive to improve the procedures according to which HVAC systems should be designed, operated and maintained. It is surprising that very little or nearly no information was available in the scientific literature reviewed as regards recirculation, draught and noise, all known from practice and experience to be likely causes of discomfort for occupants in nonindustrial indoor environments. 34

3 Table 1. Bibliographic references of the papers used to formulate the final consensus statement Id Journal name Year Vol pp Id Journal name Year Vol pp Id Journal name Year Vol pp 1 Environ Health Perspec Ann Allergy Ind Air Curr Microbiol Allergy Ind Air J Ind Microbiol Appl Occup Environ Hyg Ind Air Am J Epidemiol J Allergy Clin Immunol Experientia Suppl Ind Air Allergy Occup Environ Med Am Ind Hyg Assoc J Energy Build Environ Int Curr Microbiol Am J Public Health Arch Environ Health Appl Occup Environ Hyg Ind Air Ind Air Environ Int Energy Build Bull Physiopathol Respir (Nancy) Igiene Moderna J Hosp Infec Ind Air Ind Air Build Environ Environ Int ASHRAE Trans (1) JAPCA Atmos Environ Am J Public Health Environ Int Ind Air ASHRAE Trans (2) Mycopathologia Ind Air Atmos Environ J Allergy Clin Immunol JAPCA Ind Air Atmos Environ J Ind Microbiol Ind Air J Allergy Clin Immunol Am Ind Hyg Assoc J Environ Int JAPCA Atmos Environ ASHRAE Trans Ind Air J Expo Anal Environ (1) Epidemiol 20 Clin Exp Allergy Atmos Environ Environ Int Build Environ JAPCA Ind Air Appl Environ Microbiol Occup Environ Med Ind Air Ann Intern Med Ind Air JAPCA Ind Air Ind Air Clin Exp Allergy Am J Infect Control Ind Air Proceedings: Indoor Air

4 Table 2. Summary of the review indicating papers supporting or refuting the hypotheses elaborated Hypothesis HVAC systems provide a refuge (environment favourable for survival and reproduction) for biological agents which may be introduced into the indoor environment Total number of papers [paperids according to Table 1] Papers supporting Papers refuting 26 [ [1054] ] Ventilation introduces outdoor air pollutants into the indoor environment 10 [ ] 6 [ ] Ventilation dilutes/removes air pollutants generated indoors 15 [ ] Ventilation introduces the air pollutants originating within HVAC systems into the indoor 12 [ [39] environment ] Existing filters reduce the concentration of particulate matter indoors 10 [ [71053] 63] Lack of proper maintenance of HVAC systems results in increased source strength or/and more 10 [ complaints among building occupants 67] The human factor (e.g., designer, manager, occupant) is very important for proper operation of 6 [ ] 0 ventilation (e.g., intermittent or continuous) Products of chemical reactions in the HVAC system (between e.g., ozone and VOCs) are more 3 [466272] 1 [69] harmful than the original substances and cause elevated prevalence of symptoms Allergen levels (which are proxys for asthma and allergy symptoms) are elevated by lowered 3 [202730] 0 ventilation Dry air due to high ventilation rates increases electrostatic shocks, dry eyes, rough skin, brittle nails 2 [5657] 1 [55] and hair, dry throat discomfort but at the same time the air is perceived fresher HVAC systems act as a sink for the collection of organic compounds and a source for their redistribution 2 [25] 0 The more complex the HVAC system the greater the number of problems 1 [19] 1 [47] HVAC systems have a negative impact on occupant health and wellbeing because they create noise 1 [47] 1 [14] and vibration Recirculation of indoor air has a negative impact on occupant health and wellbeing 1 [4959] 1 [32] Mechanically ventilated buildings are less balanced than naturally ventilated buildings 1 [12] 0 Airconditioning creates lower allergen levels 1 [40] 0 Heat recovery systems transfer pollutants from exhaust air to supply air and increase the indoor air pollutant concentration by decreasing the cleaning effect of ventilation air 0 1 [5] Proceedings: Indoor Air

5 Table 3. List of hypotheses not addressed in the reviewed literature Hypothesis Papers supporting Ventilation increases the oxygen levels in the occupied indoor environment High ventilation rates could eliminate the need for recirculation High ventilation rates reduce ventilation effectiveness Increased ventilation rates reduce risks of upper and lower airways infections Chronic bronchitis is increased (due to draughts) or decreased (due to pollutants) by ventilation Ischaemic heart disease is caused by increased ventilation rates due to transport of pollutants from outdoors or decreased by removing pollutants from the indoor environment Increased ventilation decreases survival of viruses and bacteria The less individual control over ventilation the more complaints among building occupants HVAC systems act as a physical sink for the collection and redistribution of respirable particles and fibres HVAC systems have a negative impact on occupant health and wellbeing due to elevated air velocity (draught) Higher air velocities in mechanically ventilated rooms cause faster drying of mucous membranes, eyes and skin which increases the prevalence of mucous membrane, eyes and skin symptoms Thermal environment is more poorly controlled with airconditioning systems compared with natural ventilation, due to HVAC malfunctions and lack of individual control, resulting in uncomfortable temperatures and temperature fluctuations that further elevate the prevalence of symptoms Poorly balanced ventilation systems (both as regards the airflow and the air distribution) increase the prevalence of symptoms and discomfort Bad reputation of AC buildings increases the prevalence of discomfort and SBS symptoms through overreporting and the psychological effect Buildings with sealed windows have an increased prevalence of symptoms and discomfort Buildings with HVAC systems are generally newer than naturally ventilated buildings, and thereby emission rates from building materials are higher, increasing the indoor air concentration and causing exposure to higher concentrations Human expectations are higher in buildings with HVAC systems than in naturally ventilated buildings Buildings with HVAC systems can have a prior critical indoor environment (size, number of people, loads) compared with naturally ventilated buildings; problems are thus caused beforehand Papers refuting Proceedings: Indoor Air

6 Proceedings: Indoor Air 2002 One possible reason could be that the papers describing the effects of these factors are mainly published in conference proceedings, technical reports, or journals with no peerreview process, which by default were not included in this literature review. Another reason could originate in the search process for the literature to be included in the review. It was required by default that the paper should report on a direct link between ventilation and its effect, such as e.g. increased air velocity, draught or noise. Many papers discussing the negative effects of noise and draught on human comfort may not have provided such a link, and therefore could be overlooked during the selection process. The EUROVEN group acknowledges that there are numerous papers describing measurements of emissions from different building products in small chambers under different ventilation conditions, which support the hypothesis that ventilation dilutes/removes air pollutants generated indoors. They were not all included in the present review. Only a few papers exemplifying the results of such experiments were included (Sollinger et al., 1993 [paperid 68]; Tichenor and Guo, 1991 [paperid 70]). The same applies to numerous field studies in which measurements of carbon dioxide, as an indicator of human occupancy, at different ventilation rates were carried out. The group acknowledges the results of studies of this nature but only few were included in the present review as an example (Daneault et al., 1992 [paperid 13]; Lee et al., 1999 [paperid 38]). CONCLUSIONS AND IMPLICATIONS The group reached the following consensus: Increasing outdoor air supply rates in indoor non industrial environments dilutes and/or removes pollutants generated indoors, and reduces the levels of allergens. Potential causes of adverse health effects due to HVAC systems comprise: poor maintenance, poor hygiene of the HVAC systems; intermittent operation of the HVAC systems; lack of moisture control; lack of control of HVAC system materials and used filters. Other causes may include recirculation, draught, noise and fibres but there is little information on these issues in the scientific peerreviewed literature. These results imply that there is a need to change and improve the HVAC maintenance procedures, HVAC design, and the way the HVAC systems are currently operated. The present work indicates the gaps in knowledge and the areas requiring further research. ACKNOWLEDGEMENTS The present work has been supported by the European Commission in the framework of programmes and actions in the health and consumer protection sectors SANCO through Grant Agreement No SI (2000CVG2604) to the National Institute of Public Health in Sweden. REFERENCES Bluyssen P M, de Oliveira Fernandes E, Groes L, et al European indoor air quality audit project in 56 office buildings. Indoor Air. Vol. 6, pp Daneault S, Beausoleil M, and Messing K Air quality during the winter in Quebec daycare centers. American Journal of Public Health. Vol. 82, pp Fisk W J, Mendell M J, Daisey J M, et al Phase 1 of the California healthy building study. Indoor Air. Vol. 4, pp Lee SC, Chan LY, and Chiu MY Indoor and outdoor air quality investigation at 14 public places in Hong Kong. Environment International. Vol. 25, pp Sollinger S, Levsen K, and Wuensch G Indoor air pollution by organic emissions from textile floor coverings. Climate chamber studies under dynamic conditions. Atmospheric Environment. Vol. 27B, pp Tichenor BA, and Guo Z The effect of ventilation on emission rates of wood finishing materials. Environment International. Vol. 17, pp Wargocki P, Sundell J, Bischof W, et al Ventilation and Health in Nonindustrial Indoor Environments. Report from a European Multidisciplinary Scientific Consensus Meeting. Indoor Air. Vol. 12, (in press). 38