The prevalence and incidence of sick building syndrome in Chinese pupils in relation to the school environment: a two-year follow-up study

There are few incidence studies on sick building syndrome (SBS). We studied two-year change of SBS in Chinese pupils in relation to parental asthma/allergy (heredity), own atopy, classroom temperature, relative humidity (RH), absolute humidity (AH), crowdedness, CO?, NO?, and SO?. A total of 1993 participated at baseline, and 1143 stayed in the same classrooms after two years. The prevalence of mucosal and general symptoms was 33% and 28% at baseline and increased during follow-up (P < 0.001). Twenty-seven percent reported at least one symptom improved when away from school. Heredity and own atopy were predictors of SBS at baseline and incidence of SBS. At baseline, SO? was associated with general symptoms (OR=1.10 per 100 μg/m3), mucosal symptoms (OR=1.12 per 100 μg/m3), and skin symptoms (OR=1.16 per 100 μg/m3). NO? was associated with mucosal symptoms (OR=1.13 per 10 μg/m3), and symptoms improved when away from school (OR=1.13 per 10 μg/m3). Temperature, RH, AH, and CO? were negatively associated with prevalence of SBS. Incidence or remission of SBS was not related to any exposure, except a negative association between SO? and new skin symptoms. In conclusion, heredity and atopy are related to incidence and prevalence of SBS, but the role of the measured exposures for SBS is more unclear. PRACTICAL IMPLICATIONS: We found high levels of CO? indicating inadequate ventilation and high levels of SO? and NO?, both indoors and outdoors. All schools had natural ventilation, only. Relying on window opening as a tool for ventilation in China is difficult because increased ventilation will decrease the level of CO? but increase the level of NO? and SO? indoors. Prevalence studies of sick building syndrome (SBS) might not be conclusive for causal relationships, and more longitudinal studies on SBS are needed both in China and other parts of the world. The concept of mechanical ventilation and air filtration should be introduced in the schools, and when planning new schools, locations close to heavily trafficked roads should be avoided.     

How much does Environmental Tobacco Smoke Contribute to the Building Symptom Index?

Environmental tobacco smoke (ETS) has been identified as one of the factors associated with the symptoms of the sick building syndrome (SBS). We investigated the role of ETS in an office building during the phased introduction of a smoking ban. Over a two-year period we measured symptoms using a validated questionnaire, environmental nicotine levels and salivary cotinine as a biological marker of nicotine absorption in a stratified systemic sample of 375 office employees (91% response rate). In addition, 26 persons from a non-smoking office were studied as a control group. This report describes the findings derived from a cross-sectional analysis of the initial baseline data. Amongst the validated nonsmokers, symptoms increased with increasing nicotine exposure from ETS (r= 0.165 p < 0. 01), supporting the role of ETS in the SBS. Smokers reported significantly fewer symptoms than non-smokers, as has been found before, but were exposed to higher levels of airborne nicotine as expected. We suggest that this factor, along with the misclassification of smoking status, may have obscured an association between ETS exposure and the SBS in previous studies. An analysis of the findings after implementation of the smoking ban should provide further information on how much of the SBS is attributable to ETS in this study population.     

Associations between indoor CO2 concentrations and sick building syndrome symptoms in U.S. office buildings: an analysis of the 1994-1996 BASE study data

Higher indoor concentrations of air pollutants due, in part, to lower ventilation rates are a potential cause of sick building syndrome (SBS) symptoms in office workers. The indoor carbon dioxide (CO2) concentration is an approximate surrogate for indoor concentrations of other occupant-generated pollutants and for ventilation rate per occupant. Using multivariate logistic regression (MLR) analyses, we evaluated the relationship between indoor CO2 concentrations and SBS symptoms in occupants from a probability sample of 41 U.S. office buildings. Two CO2 metrics were constructed: average workday indoor minus average outdoor CO2 (dCO2, range 6-418 ppm), and maximum indoor 1-h moving average CO2 minus outdoor CO2 concentrations (dCO2MAX). MLR analyses quantified dCO2/SBS symptom associations, adjusting for personal and environmental factors. A dose-response relationship (p < 0.05) with odds ratios per 100 ppm dCO2 ranging from 1.2 to 1.5 for sore throat, nose/sinus, tight chest, and wheezing was observed. The dCO2MAX/SBS regression results were similar.     

Sick Building Syndrome: Cleanliness is Next to Healthiness

There is evidence that sick building syndrome (SBS) is caused, in part, by indoor surface pollution (ISP): contaminants such as dust, fibres and micro-organisms, deposited on or in surfaces in buildings. A study is described which clarifies the relative importance of a number of possible causes of SBS in a single building. The building, which had a high initial prevalence of SBS symptoms, was used in a doubleblind controlled intervention study with weekly symptom questionnaires. The four interventions were: ventilation system cleaning, air filtration, hot-water extraction cleaning of chairs and carpets, plus high grade filter vacuuming and dusting, and dust mite treatment (application of liquid nitrogen). Only the last two interventions brought about a reduction in symptoms. It is concluded that cleaning which effectively reduces ISP can reduce SBS symptoms. This may be related to the presence of dust mites in furnishings. Improved cleaning may entail better cleaning specifications and/or consideration of requirements for cleaning when selecting and positioning office furniture. If ISP and the temporary local pollution levels created by it are a problem, then monitoring of ambient conditions (by instruments or by human assessors) will not adequately represent the conditions to which occupants are exposed     

Sick building syndrome—A case study in a multistory centrally air-conditioned building in the Delhi City

Recently, airtight envelope system has become popular in the design of office buildings to reduce heating and cooling loads. Maintaining allowable indoor air quality (IAQ) for such airtight buildings totally depends on mechanical ventilation systems. Subsequently, poor operation of the ventilation system in such office buildings causes ineffective removal of polluted indoor air, and displays a sign of “sick building syndrome” (SBS). User's perception is an important parameter for evaluating IAQ. A questionnaire study was carried out to investigate the prevalence of the SBS at a multistory centrally air-conditioned Airport Authority of India (AAI) building in the New Delhi city. Quantification of the perceptions of the users regarding IAQ was done by converting their responses to a SBS score. The quantified answers were then subjected to statistical analysis. Qualitative analysis of the questionnaire was carried out to evaluate relationships between SBS score and carbon dioxide (CO₂) and other parameters related to building and work environment. Quantitative analysis of IAQ was also conducted by monitoring indoor concentrations of four pollutants, namely, nitrogen dioxide (NO₂), sulphur dioxide (SO₂), suspended particulate matter (SPM) and carbon monoxide (CO). Concentrations of pollutants were complying with IAQ standards as given by ASHRAE and WHO. The SBS was higher on the third floor as compared to other floors and the control tower. The main symptoms prevailing were headache (51%), lethargy (50%), and dryness in body mucous (33%). The third floor and the control tower were affected by infiltration, mainly from entrance doors. A direct relation between the average SBS score and CO₂ concentration was found, i.e., the average SBS score increased with CO₂ concentration and vice versa, clearly signifying the usefulness of SBS score in IAQ.     

The effects of outdoor air supply rate in an office on perceived air quality, sick building syndrome (SBS) symptoms and productivity

Perceived air quality, Sick Building Syndrome (SBS) symptoms and productivity were studied in a normally furnished office space (108 m3) ventilated with an outdoor airflow of 3, 10 or 30 L/s per person, corresponding to an air change rate of 0.6, 2 or 6 h-1. The temperature of 22 degrees C, the relative humidity of 40% and all other environmental parameters remained unchanged. Five groups of six female subjects were each exposed to the three ventilation rates, one group and one ventilation rate at a time. Each exposure lasted 4.6 h and took place in the afternoon. Subjects were unaware of the intervention and remained thermally neutral by adjusting their clothing. They assessed perceived air quality and SBS symptoms at intervals, and performed simulated normal office work. Increasing ventilation decreased the percentage of subjects dissatisfied with the air quality (P < 0.002) and the intensity of odour (P < 0.02), and increased the perceived freshness of air (P < 0.05). It also decreased the sensation of dryness of mouth and throat (P < 0.0006), eased difficulty in thinking clearly (P < 0.001) and made subjects feel generally better (P < 0.0001). The performance of four simulated office tasks improved monotonically with increasing ventilation rates, and the effect reached formal significance in the case of text-typing (P < 0.03). For each two-fold increase in ventilation rate, performance improved on average by 1.7%. This study shows the benefits for health, comfort and productivity of ventilation at rates well above the minimum levels prescribed in existing standards and guidelines. It confirms the results of a previous study in the same office when the indoor air quality was improved by decreasing the pollution load while the ventilation remained unchanged.     

Association of ventilation rates and CO2 concentrations with health and other responses in commercial and institutional buildings

This paper reviews current literature on the associations of ventilation rates and carbon dioxide concentrations in non-residential and non-industrial buildings (primarily offices) with health and other human outcomes. Twenty studies, with close to 30,000 subjects, investigated the association of ventilation rates with human responses, and 21 studies, with over 30,000 subjects, investigated the association of carbon dioxide concentration with these responses. Almost all studies found that ventilation rates below 10 Ls-1 per person in all building types were associated with statistically significant worsening in one or more health or perceived air quality outcomes. Some studies determined that increases in ventilation rates above 10 Ls-1 per person, up to approximately 20 Ls-1 per person, were associated with further significant decreases in the prevalence of sick building syndrome (SBS) symptoms or with further significant improvements in perceived air quality. The carbon dioxide studies support these findings. About half of the carbon dioxide studies suggest that the risk of sick building syndrome symptoms continued to decrease significantly with decreasing carbon dioxide concentrations below 800 ppm. The ventilation studies reported relative risks of 1.5-2 for respiratory illnesses and 1.1-6 for sick building syndrome symptoms for low compared to high low ventilation rates.     

Perceptions in the U.S. building industry of the benefits and costs of improving indoor air quality

How building stakeholders (e.g. owners, tenants, operators, and designers) understand impacts of Indoor Air Quality (IAQ) and associated energy costs is unknown. We surveyed 112 stakeholders across the United States to ascertain their perceptions of their current IAQ and estimates of benefits and costs of, as well as willingness to pay for, IAQ improvements. Respondents' perceived IAQ scores correlated with the use of high‐efficiency filters but not with any other IAQ‐improving technologies. We elicited their estimates of the impacts of a ventilation–filtration upgrade (VFU), that is, doubling the ventilation rate from 20 to 40 cfm/person (9.5 to 19 l/s/person) and upgrading from a minimum efficiency reporting value 6 to 11 filter, and compared responses to estimates derived from IAQ literature and energy modeling. Minorities of respondents thought the VFU would positively impact productivity (45%), absenteeism (23%), or health (39%). Respondents' annual VFU cost estimates (mean = $257, s.d. = $496, median = $75 per person) were much higher than ours (always <$32 per person), and the only yearly cost a plurality of respondents said they would pay for the VFU was $15 per person. Respondents holding green building credentials were not more likely to affirm the IAQ benefits of the VFU and were less likely to be willing to pay for it.     

Association of ventilation system type with SBS symptoms in office workers

This paper provides a synthesis of current knowledge about the associations of ventilation system types in office buildings with sick building syndrome (SBS) symptoms and discusses potential explanations for the associations. Most studies completed to date indicate that relative to natural ventilation, air conditioning, with or without humidification, was consistently associated with a statistically significant increase in the prevalence of one or more SBS symptoms, by approximately 30 to 200%. In two of three analyses from a single study (assessments), symptom prevalences were also significantly higher in air-conditioned buildings than in buildings with simple mechanical ventilation and no humidification. The available data also suggest, with less consistency, an increase in risk of symptoms with simple mechanical ventilation relative to natural ventilation. Insufficient information was available for conclusions about the potential increased risk of SBS symptoms with humidification or recirculation of return air. The statistically significant associations of mechanical ventilation and air conditioning with SBS symptoms are much more frequent than expected from chance and also not likely to be a consequence of confounding by several potential personal, job, or building-related confounders. Multiple deficiencies in HVAC system design, construction, operation, or maintenance, including some which cause pollutant emissions from HVAC systems, may contribute to the increases in symptom prevalences but other possible reasons remain unclear.     

Passenger evaluation of the optimum balance between fresh air supply and humidity from 7-h exposures in a simulated aircraft cabin

A 21-seat section of an aircraft cabin with realistic pollution sources was built inside a climate chamber capable of providing fresh outside air at very low humidity. Maintaining a constant 200 l/s rate of total air supply, i.e. recirculated and make-up air, to the cabin, experiments simulating 7-h transatlantic flights were carried out at four rates of fresh outside air supply--1.4, 3.3, 4.7, and 9.4 l/s per person (3, 7, 10, and 20 cfm/person)--resulting in humidity levels, ranging from 7% to 28% relative humidity (RH). Four groups of 16-18 subjects acted as passengers and crew and were each exposed to the four simulated flight conditions. During each flight the subjects completed questionnaires three times to provide subjective ratings of air quality and of symptoms commonly experienced during flight. Physiological tests of eye, nose, and skin function were administered twice. Analysis of the subjective assessments showed that increasing RH in the aircraft cabin to 28% RH by reducing outside flow to 1.4 l/s per person did not reduce the intensity of the symptoms that are typical of the aircraft cabin environment. On the contrary, it intensified complaints of headache, dizziness, and claustrophobia, due to the increased level of contaminants. PRACTICAL IMPLICATIONS: The investigation shows that increasing aircraft cabin humidity by decreasing the ventilation flow rate of fresh outside air would not decrease reports of discomfort made by cabin occupants.     

Ventilation and health in non-industrial indoor environments: report from a European multidisciplinary scientific consensus meeting (EUROVEN)

Scientific literature on the effects of ventilation on health, comfort, and productivity in non-industrial indoor environments (offices, schools, homes, etc.) has been reviewed by a multidisciplinary group of European scientists, called EUROVEN, with expertise in medicine, epidemiology, toxicology, and engineering. The group reviewed 105 papers published in peer-reviewed scientific journals and judged 30 as conclusive, providing sufficient information on ventilation, health effects, data processing, and reporting, 14 as providing relevant background information on the issue, 43 as relevant but non-informative or inconclusive, and 18 as irrelevant for the issue discussed. Based on the data in papers judged conclusive, the group agreed that ventilation is strongly associated with comfort (perceived air quality) and health [Sick Building Syndrome (SBS) symptoms, inflammation, infections, asthma, allergy, short-term sick leave], and that an association between ventilation and productivity (performance of office work) is indicated. The group also concluded that increasing outdoor air supply rates in non-industrial environments improves perceived air quality; that outdoor air supply rates below 25 l/s per person increase the risk of SBS symptoms, increase short-term sick leave, and decrease productivity among occupants of office buildings; and that ventilation rates above 0.5 air changes per hour (h-1) in homes reduce infestation of house dust mites in Nordic countries. The group concluded additionally that the literature indicates that in buildings with air-conditioning systems there may be an increased risk of SBS symptoms compared with naturally or mechanically ventilated buildings, and that improper maintenance, design, and functioning of air-conditioning systems contributes to increased prevalence of SBS symptoms.     

Sick building syndrome and perceived indoor environment in relation to energy saving by reduced ventilation flow during heating season: a 1 year intervention study in dwellings

Ventilation in Scandinavian buildings is commonly performed by means of a constant flow ventilation fan. By using a regulated fan, it is possible to make a seasonal adjustment of outdoor ventilation flow. Energy saving can be achieved by reducing the mechanical ventilation flow during the heating season, when natural ventilation driven by temperature differences between outdoor and indoor is relatively high. This ventilation principle has been called 'seasonally adapted ventilation (SAV)'. The aim was to study if a 25-30% reduction of outdoor ventilation flow during heating season influenced sick building syndrome (SBS) and the perception of the indoor environment. This was done in a 1-year cross-over intervention study in 44 subjects in a multi-family building. During the first heating season (November to April), one part of the building (A) got a reduced flow during the heating season [0.4-0.5 air exchanges per hour (ACH)] while the other part (B) had constant flow (0.5-0.8 ACH). The next heating season, part A got constant flow, while part B got reduced ventilation flow. Reduced ventilation increased the relative air humidity by 1-3% in the living room (mean 30-37% RH), 1-5% in the bathroom (mean 48-58% RH) during heating season. The room temperature increased 0.1-0.3 degrees C (mean 20.7-21.6 degrees C), mean carbon dioxide (CO2) concentration in the bedroom increased from 920 to 980 p.p.m. at reduced flow. The indoor air quality was perceived as poorer at reduced outdoor airflow, both in the bedroom and in the apartment as a whole. There was a significant increase of stuffy odor (P = 0.05) at reduced outdoor airflow and the indoor air quality was perceived as poorer, both in the bedroom (P = 0.03) and in the apartment as a whole (P = 0.04). No significant influence on SBS symptoms or specific perceptions such as odors, draught, temperature, air dryness or stuffy air could be detected. In conclusion, reducing the ventilation flow in dwellings to a level below the current Swedish ventilation standard (0.5 ACH) may cause a perception of impaired air quality. Technical measurements could only demonstrate a minor increase of indoor temperature, relative air humidity, and bedroom CO2 concentration. This illustrates that it is important to combine technical measurements with a longitudinal evaluation of occupant reactions, when evaluating energy-saving measures. PRACTICAL IMPLICATIONS: It is important to combine technical measurements with a longitudinal evaluation of occupant reactions, when evaluating energy-saving measures. Reduction of outdoor airflow in dwellings below the current ventilation standard of 0.5 ACH may lead to a perception of impaired air quality, despite only a minor increase of bedroom CO2-concentration.     

Ventilation rates and health: multidisciplinary review of the scientific literature

The scientific literature through 2005 on the effects of ventilation rates on health in indoor environments has been reviewed by a multidisciplinary group. The group judged 27 papers published in peer-reviewed scientific journals as providing sufficient information on both ventilation rates and health effects to inform the relationship. Consistency was found across multiple investigations and different epidemiologic designs for different populations. Multiple health endpoints show similar relationships with ventilation rate. There is biological plausibility for an association of health outcomes with ventilation rates, although the literature does not provide clear evidence on particular agent(s) for the effects. Higher ventilation rates in offices, up to about 25 l/s per person, are associated with reduced prevalence of sick building syndrome (SBS) symptoms. The limited available data suggest that inflammation, respiratory infections, asthma symptoms and short-term sick leave increase with lower ventilation rates. Home ventilation rates above 0.5 air changes per hour (h(-1)) have been associated with a reduced risk of allergic manifestations among children in a Nordic climate. The need remains for more studies of the relationship between ventilation rates and health, especially in diverse climates, in locations with polluted outdoor air and in buildings other than offices. PRACTICAL IMPLICATIONS: Ventilation with outdoor air plays an important role influencing human exposures to indoor pollutants. This review and assessment indicates that increasing ventilation rates above currently adopted standards and guidelines should result in reduced prevalence of negative health outcomes. Building operators and designers should avoid low ventilation rates unless alternative effective measures, such as source control or air cleaning, are employed to limit indoor pollutant levels.     

The Helsinki Office Environment Study: Air Change in Mechanically Ventilated Buildings

Abstract The objective of this study was to assess the magnitude and balance of mechanical ventilation in the rooms of Helsinki metropolitan office buildings with different types of ventilation systems. A random sample of 50 office buildings was selected from the Building Registry. Of these buildings, the 33 that have a mechanical ventilation system were included in this study. Most office buildings in the Helsinki metropolitan area have a ducted supply and exhaust system and hot water radiator heating. Air recirculation is used in about half of the buildings which have a mechanical supply and exhaust system. The average exhaust airflow was 1.2 L/s, m² (SD 0.73) or 17.2 L/s per person (SD 11.6). The variation of the airflows was found to be very high among the buildings, and among the rooms within the buildings. Therefore, even though the ventilation rates on average comply with the Finnish building code, it was found that many people were working in offices with airflows which were either too low or unnecessarily high.     

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.     

Effects of pollution from personal computers on perceived air quality, SBS symptoms and productivity in offices

In groups of six, 30 female subjects were exposed for 4.8 h in a low-polluting office to each of two conditions--the presence or absence of 3-month-old personal computers (PCs). These PCs were placed behind a screen so that they were not visible to the subjects. Throughout the exposure the outdoor air supply was maintained at 10 l/s per person. Under each of the two conditions the subjects performed simulated office work using old low-polluting PCs. They also evaluated the air quality and reported Sick Building Syndrome (SBS) symptoms. The PCs were found to be strong indoor pollution sources, even after they had been in service for 3 months. The sensory pollution load of each PC was 3.4 olf, more than three times the pollution of a standard person. The presence of PCs increased the percentage of people dissatisfied with the perceived air quality from 13 to 41% and increased by 9% the time required for text processing. Chemical analyses were performed to determine the pollutants emitted by the PCs. The most significant chemicals detected included phenol, toluene, 2-ethylhexanol, formaldehyde, and styrene. The identified compounds were, however, insufficient in concentration and kind to explain the observed adverse effects. This suggests that chemicals other than those detected, so-called 'stealth chemicals', may contribute to the negative effects. PRACTICAL IMPLICATIONS: PCs are an important, but hitherto overlooked, source of pollution indoors. They can decrease the perceived air quality, increase SBS symptoms and decrease office productivity. The ventilation rate in an office with a 3-month-old PC would need to be increased several times to achieve the same perceived air quality as in a low-polluting office with the PC absent. Pollution from PCs has an important negative impact on the air quality, not only in offices but also in many other spaces, including homes. PCs may have played a role in previously published studies on SBS and perceived air quality, where PCs were overlooked as a possible pollution source in the indoor environment. The fact that the chemicals identified in the office air and in the chamber experiments were insufficient to explain the adverse effects observed during human exposures illustrates the inadequacy of the analytical chemical methods commonly used in indoor air quality investigations. For certain chemicals the human senses are much more sensitive than the chemical methods routinely used in indoor air quality investigations. The adverse effects of PC-generated air pollutants could be reduced by modifications in the manufacturing process, increased ventilation, localized PC exhaust, or personalized ventilation systems.     

A study of perceived air quality and sick building syndrome in a field environment chamber served by displacement ventilation system in the tropics

This paper presents a study of Perceived Air Quality (PAQ) and Sick Building Syndrome (SBS) using tropically acclimatized subjects in a Field Environmental Chamber (FEC) served by Displacement Ventilation (DV) system. The FEC, 11.12 m (L)×7.53 m (W)×2.60 m (H), simulates a typical office layout. A total of 60 subjects, 30 males and 30 females, were engaged in sedentary office work for 3 h. Air velocity in the space near the subjects was kept at below 0.2 m/s. Relative Humidity (RH) at 0.6 m height and outdoor air provision were maintained at 50% and 10 l/s/p, respectively. Subjects were exposed to three vertical air temperature gradients, nominally 1, 3 and 5 K/m, between 0.1 and 1.1 m heights and three room air temperatures 20, 23 and 26 °C at 0.6 m height. The main objective of this study is to evaluate the influence of temperature gradient and room air temperature (at 0.6 m height) on PAQ and SBS in DV environment. It was found that temperature gradient had insignificant impact on PAQ and SBS. Dry air sensation, irritations and air freshness decreased with increase of room air temperature.     

Pilot study of the effects of ventilation and ventilation noise on sleep quality in the young and elderly

Three conditions were established to investigate the effects of ventilation and related ventilation noise on sleep quality: No mechanical ventilation/low noise (A); Mechanical ventilation /low noise (B); Mechanical ventilation/high noise (C). The interventions were achieved by idling a mechanical ventilation system or operating it in two different modes. Nine young people and nine older people were all exposed to each of the three conditions for a whole night's sleep, but data from only 15 subjects were analyzed as three young subjects apparently slept with open windows in condition A. Sleep quality was measured objectively with polysomnography (PSG), which monitored signals of electroencephalogram (EEG), bilateral electrooculogram (EOG), and chin electromyogram (EMG) continuously during the sleeping period. Saliva samples were collected before sleep at night and after waking in the morning, and the concentrations of cortisol and lysozyme in them were determined. Without mechanical ventilation, the indoor CO₂ level averaged about 1400 ppm during the night. Operating the mechanical ventilation decreased the indoor CO₂ to below 1000 ppm, which improved objectively measured sleep quality: wake time after sleep onset (WASO) decreased on average by 15 min (p < 0.05) and sleep efficiency (SE) increased on average by about 4% (p < 0.05). Increased ventilation noise level (50.8dB(A) vs. 34.7dB(A); 54.9dB(C) vs. 48dB(C)) did not significantly change SE or WASO but did change the duration of sleep stages: It decreased the duration of deep sleep by 11min (p < 0.05) and REM sleep by 17 min (p < 0.01) and increased the duration of light sleep by 17 min (p < 0.05). The ventilation noise significantly increased the concentration of lysozyme in the elderly (p < 0.05) although no significant effects on cortisol could be shown. These results confirm that a low ventilation rate has negative effects on sleep quality and that ventilation noise at or above 50dB(A) may disrupt sleep.     

Ocular,nasal, dermal and respiratory symptoms in relation to heating,ventilation, energy conservation,and reconstruction of older multi-family houses

The aim was to study relationships between symptoms compatible with the sick building syndrome, type of heating and ventilation system, energy saving, and reconstruction in older dwellings. In Stockholm, 4815 inhabitants in 231 multi-family buildings built before 1961 were randomly selected, of whom 3241 participated (77%). Symptoms and personal factors were assessed by a postal questionnaire. Independent information on building characteristics, and energy saving measures was gathered from the building owners. Multiple logistic regression analysis was applied to calculate odds ratios (OR) adjusting for age, gender, hay fever, current smoking, population density, type of ventilation, type of heating system, and ownership of the building. Subjects in buildings with a mechanical ventilation system had less ocular and nasal symptoms (OR = 0.29-0.85). Heating by electric radiators, and wood heating was associated with an increase of most symptoms (OR = 1.18-1.74). In total, 48% lived in buildings that had gone through at least one type of reconstruction or energy saving remedies during the latest 10 years, including exchange of heating or ventilation system, and sealing measures (exchange of windows, sealing of window frames, roof/attic insulation, and phasade insulation). Energy saving was associated with both a decrease and increase of different symptoms. Major reconstruction of the interior of the building was associated with an increase of most symptoms (OR = 1.09-1.90), and buildings with more than one sealing measure had an increase of ocular, nasal symptoms, headache and tiredness (OR = 1.22-2.49). In conclusion, major reconstruction of the interior, direct heated electric radiators, wood heating, and multiple sealing of buildings were associated with an increase of some symptoms. The study supports the view that mechanical ventilation in dwellings is beneficial from a health point of view.     

Relationship between selected indoor volatile organic compounds, so-called microbial VOC, and the prevalence of mucous membrane symptoms in single family homes

Microorganisms are known to produce a range of volatile organic compounds, so-called microbial VOC (MVOC). Chamber studies where humans were exposed to MVOC addressed the acute effects of objective and/or subjective signs of mucosal irritation. However, the effect of MVOC on inhabitants due to household exposure is still unclear. The purpose of this epidemiological study was to measure indoor MVOC levels in single family homes and to evaluate the relationship between exposure to them and sick building syndrome (SBS). All inhabitants of the dwellings were given a self-administered questionnaire with standardized questions to assess their symptoms. Air samples were collected and the concentrations of eight selected compounds in indoor air were analyzed by gas chromatography/mass spectrometry — selective ion monitoring mode (GC/MS-SIM). The most frequently detected MVOC was 1-pentanol at a detection rate of 78.6% and geometric mean of 0.60 μg/m³. Among 620 participants, 120 (19.4%) reported one or more mucous symptoms; irritation of the eyes, nose, airway, or coughing every week (weekly symptoms), and 30 (4.8%) reported that the symptoms were home-related (home-related symptoms). Weekly symptoms were not associated with any of MVOC, whereas significant associations between home-related mucous symptoms and 1-octen-3-ol (per log₁₀-unit: odds ratio (OR) 5.6, 95% confidence interval (CI): 2.1 to 14.8) and 2-pentanol (per log₁₀-unit: OR 2.3, 95% CI: 1.0 to 4.9) were obtained after adjustment for gender, age, and smoking. Associations between home-related symptoms and 1-octen-3-ol remained after mutual adjustment. However, concentrations of the selected compounds in indoors were lower than the estimated safety level in animal studies. Thus, the statistically significant association between 1-octen-3-ol may be due to a direct effect of the compounds or the associations may be being associated with other offending compounds. Additional studies are needed to evaluate these possibilities.