Consistent pattern of elevated symptoms in air-conditioned office buildings: a reanalysis of epidemiologic studies.

Published studies of the relation between type of building ventilation system and work-related symptom prevalence in office workers have been contradictory. A reanalysis was performed of six studies meeting specific eligibility criteria, combining published data with unpublished information obtained from study authors. Five eligible studies were from the United Kingdom, and one was from Denmark. Standardized categories of building ventilation type were created to allow comparison of effects across studies. Within each study, prevalence odds ratios (PORs) were calculated for symptoms in each ventilation category relative to a baseline category of naturally ventilated buildings. Air-conditioned buildings were consistently associated with increased prevalence of work-related headache (POR = 1.3-3.1), lethargy (POR = 1.4-5.1), and upper respiratory/mucus membrane symptoms (POR = 1.3-4.8). Humidification was not a necessary factor for the higher symptom prevalence associated with air-conditioning. Mechanical ventilation without air-conditioning was not associated with higher symptom prevalence. The consistent associations found between type of building ventilation and reported symptom prevalence have potentially important public health and economic implications.     

Building sickness syndrome in healthy and unhealthy buildings: an epidemiological and environmental assessment with cluster analysis

OBJECTIVES—Building sickness syndrome remains poorly understood. Aetiological factors range from temperature, humidity, and air movement to internal pollutants, dust, lighting, and noise factors. The reported study was designed to investigate whether relations between symptoms of sick building syndrome and measured environmental factors existed within state of the art air conditioned buildings with satisfactory maintenance programmes expected to provide a healthy indoor environment.
METHODS—Five buildings were studied, three of which were state of the art air conditioned buildings. One was a naturally ventilated control building and one a previously studied and known sick building. A questionnaire was administered to the study population to measure the presence of building related symptoms. This was followed by a detailed environmental survey in identified high and low symptom areas within each building. These areas were compared for their environmental performance.
RESULTS—Two of the air conditioned buildings performed well with a low prevalence of building related symptoms. Both of these buildings out performed the naturally ventilated building for the low number of symptoms and in many of the environmental measures. One building (C), expected to perform well from a design viewpoint had a high prevalence of symptoms and behaved in a similar manner to the known sick building. Environmental indices associated with symptoms varied from building to building. Consistent associations between environmental variables were found for particulates (itchy eyes, dry throat, headache, and lethargy) across all buildings. There were persisting relations between particulates and symptoms (headache, lethargy, and dry skin) even in the building with the lowest level of symptoms and of measured airborne particulates (building B). There were also consistent findings for noise variables with low frequency noise being directly associated with symptoms (stuffy nose, itchy eyes, and dry skin) and higher frequency noise being relatively protective across all buildings.
CONCLUSIONS—This is the first epidemiological study of expected state of the art, air conditioned buildings. These buildings can produce an internal environment better than that of naturally ventilated buildings for both reported symptoms and environmental variables. The factors associated with symptoms varied widely across the different buildings studied although consistent associations for symptoms were found with increased exposure to particulates and low frequency noise.


Keywords: building sickness syndrome; particulates; low frequency noise     

The feasibility of using a double blind experimental cross-over design to study interventions for sick building syndrome.

Methodological problems have limited scientific investigation of the causes of and solutions for sick building syndrome. The feasibility of using an experimental double blind cross-over study to resolve many of these methodological problems was assessed in a pilot study. The experimental intervention was to vary the amount of outdoor air from 10 cubic feet per minute per person (cfmpp) to 20 cfmpp or 50 cfmpp by central manipulation of the building heating, ventilation and air-conditioning (HVAC) system. Over 6 consecutive study weeks, 2 trials of rates were administered in random order. Study subjects and investigators of the study were blinded to intervention sequence. Unblinding, office environment rating and symptom occurrence were measured weekly. Of 305 eligible workers, 254 participated. Problems were encountered in delivering the lowest dose of ventilation due to building leakage. The prevalence of symptoms diminished steadily over the 6 study weeks, time trends which could be controlled by recommended design modifications. Blinding to the intervention was successfully maintained. Weekly non-response did not introduce a response bias but reduced the number of subjects available for analysis by one-third for each trial. We conclude that this design, with certain modifications, is feasible to evaluate many proposed interventions for sick building syndrome.     

Air recirculation and sick building syndrome: a blinded crossover trial.

OBJECTIVE. This study tested the hypothesis that recirculated air in mechanically ventilated buildings causes symptoms commonly referred to as the sick building syndrome and perceptions of poor indoor air quality. METHODS. A blinded, four-period crossover trial was carried out in two identical buildings, contrasting 70% return air (index phase) with 0% of return air (reference phase). Each period lasted 1 work-week. The study population comprised 75 workers who had reported symptoms related to the work environment or perceptions of poor indoor air quality. Participants reported their ratings of symptoms, their perceptions, and related information in a daily diary. The outcome criteria included aggregative symptom scores for mucosal irritation, skin reaction, allergic reaction, and general symptoms formed of ratings of component symptoms. Perceptions of unpleasant odor, stuffiness, or dustiness were additional outcome criteria. RESULTS. All 75 participants returned their diaries. For no symptoms did the scores differ between the two phases more than could be expected by chance. Mean rating of unpleasant odor was significantly smaller during the index phase, but mean ratings of dustiness and stuffiness did not differ materially between the two phases. CONCLUSIONS. Our results suggest that 70% recirculated air, when accompanied by an adequate intake of outdoor air, can be used without causing adverse effects.     

Prevalence of the sick building syndrome symptoms in office workers before and after being exposed to a building with an improved ventilation system.

OBJECTIVE: To find if the prevalence of symptoms associated with sick building syndrome decreased among office workers after moving to a building with improved ventilation (after controlling for potential confounders). METHODS: Workers in five buildings in 1991 all moved in 1992 into a single building with improved design, operation, and maintenance of the ventilation system. All buildings had sealed windows with mechanical ventilation, air conditioning, and humidification. Workers completed a self administered questionnaire during normal working hours in February 1991 and February 1992. The questionnaire encompassed symptoms of the eyes, nose and throat, respiratory system, skin, fatigue, headache, and difficulty concentrating, personal, psychosocial, and work related factors. During normal office hours of the same week environmental variables were measured. RESULTS: The study population comprised 1390 workers in 1991 and 1371 workers in 1992 who represented more than 80% of the eligible population. The prevalence of most symptoms decreased when workers moved to the new building: skin (54%), respiratory system (53%), nose and throat (46%), fatigue (44%), headache (37%), eyes (23%). These findings were all significant and remained generally similar after controlling for personal, psychosocial, and work related factors. Furthermore, more than 60% of workers symptomatic in 1991 were asymptomatic in 1992 for all types of symptoms. In contrast, less than 15% of workers were asymptomatic in 1991 but symptomatic in 1992 for all types of symptoms. CONCLUSION: In this study, the prevalence of most symptoms usually associated with the sick building syndrome decreased by 40% to 50% after workers were transferred to a building with an improved ventilation system. The results show that it is possible to diminish the prevalence of symptoms associated with the sick building syndrome among office workers occupying a building with mechanical ventilation, air conditioning, and sealed windows.     

上海市卢湾区办公楼宇职业办公人群不良建筑综合征调查

[目的]研究办公楼宇职业办公人群不良建筑综合征（sick building syndrome,SBS）与办公环境之间的关系及其主要影响因素。[方法]以是否使用集中式空调为标准将办公楼分组,对办公楼环境进行检测并调查其中办公人群,用个人5项症状（即眼干燥或疼痛,鼻塞、喉干燥或疼痛、头痛和疲倦感5项症状都出现的出现数并结合离开办公室症状消除作为判断依据）进行判别并分析其与环境指标之间的关系。[结果]使用集中式空调办公楼的主要环境影响因素是氨、噪声、湿度和新风量,不使用集中式空调办公楼的主要环境影响因素是甲醛、氨、噪声、温度、照度;使用集中武空调办公楼与不使用集中式空调办公楼办公人群的SBS症状检出率分别为13．2％与10．2％,疲倦、眼干燥或疼痛、皮肤干燥、头痛、喉干分别位居各类症状的前5位。[结论]办公环境温度、环境湿度、新风量3项指标与办公楼宇SBS人群存在相关关系,是办公环境SBS的主要影响因素。     

Office equipment and supplies: a modern occupational health concern?

The Helsinki Office Environment Study, a population-based cross-sectional study was carried out in Finland in 1991 among 2,678 workers in 41 randomly selected office buildings. The aim was to evaluate the relations between work with office equipment and supplies and the occurrence of eye, nasopharyngeal, skin, and general symptoms (often denoted as sick building syndrome (SBS)), chronic respiratory symptoms, and respiratory infections. Work with self-copying paper was significantly related to weekly work-related eye, nasopharyngeal, and skin symptoms, headache and lethargy, as well as to the occurrence of wheezing, cough, mucus production, sinusitis, and acute bronchitis. Photocopying was related to nasal irritation, and video display terminal work to eye symptoms, headache, and lethargy.     

Exposure to varying levels of contaminants and symptoms among workers in two office buildings.

OBJECTIVES: We hypothesized that exposure to contaminants would be associated with symptoms reported by office workers. METHODS: In two mechanically ventilated office buildings in. Montreal, the outdoor air supply was manipulated for 6 weeks, while symptoms were reported and environmental parameters were measured at multiple sites. RESULTS: Contaminant concentrations varied considerably, in part related to experimental changes in outdoor air supply. Eye symptoms were reported with higher dust and with higher concentrations of nitrogen dioxide. Mucosal symptoms were increased with higher TVOCs, higher nitrogen dioxide, and higher total contaminant load. Systemic symptoms were associated with higher dust levels. CONCLUSIONS: Symptoms reported by the workers were associated with increased concentrations of several contaminants and a summary measure of all contaminants.     

Indoor biological contaminants and symptoms of sick building syndrome in office buildings in Mauritius

This study was carried out to investigate possible relationship between bio-contaminants and symptoms of sick building syndrome among office workers in Mauritius. Viable microbial colonies were collected using a Casella slit sampler in 23 selected indoor office buildings. A questionnaire survey as well as a walk through investigation was undertaken. Physico-chemical measurements were also monitored in the selected offices. Results of this study showed that number of indoor bacterial bioaerosol concentrations ranged between 3 and 1110 CFU/m(3) while fungal counts were 0-196 CFU/m(3). However, most of the buildings showed absence of dust mites. In conclusions fungal contamination was found to be associated with the onset of sick building syndrome symptoms among workers in office buildings in Mauritius.     

Indicators of moisture and ventilation system contamination in U.S. office buildings as risk factors for respiratory and mucous membrane symptoms: analyses of the EPA BASE data

We assessed associations between indicators for moisture in office buildings and weekly, building-related lower respiratory and mucous membrane symptoms in office workers, using the U.S. EPA BASE data, collected in a representative sample of 100 U.S. office buildings. We estimated the strength of associations between the symptom outcomes and moisture indicators in multivariate logistic regression models as odds ratios (ORs) and 95% confidence intervals (CI), controlling for potential confounding factors and adjusting for correlation among workers in buildings. This analysis identified associations between building-related symptoms and several indicators of moisture or contamination in office buildings. One set of models showed almost a tripling of weekly building-related lower respiratory symptoms in association with lack of cleaning of the drip pans under air-conditioning cooling coils (OR [CI] = 2.8 (1.2-6.5)). Other models found that lack of cleaning of either drip pans or cooling coils was associated with increased mucous membrane symptoms (OR [CI] = 1.4 (1.1-1.9)). Slightly increased symptoms were also associated with other moisture indicators, especially mucous membrane symptoms and past water damage to building mechanical rooms (OR [CI] = 1.3 (1.0-1.7)). Overall, these findings suggest that the presence of moisture or contamination in ventilation systems or occupied spaces in office buildings may have adverse respiratory or irritant effects on workers. The analysis, however, failed to confirm several risks identified in a previous study, such as condition of drain pans or outdoor air intakes, and other hypothesized moisture risks. Studies with more rigorous measurement of environmental risks and health outcomes will be necessary to define moisture-related risks in buildings.     

Study of indoor radon levels in high-rise air-conditioned office buildings

A series of measurements were conducted to study the indoor radon pollution in air-conditioned high-rise office buildings. Continuous monitoring of indoor radon levels in nine air-conditioned premises located in six office buildings in Hong Kong was conducted from August 1996 to February 1998. Each of the tests lasted for at least 48 hours. The measurement covered both day time monitoring while the air-conditioning was on and night time monitoring while the air-conditioning was off. The indoor radon level followed inversely the operation pattern of the mechanical ventilation systems in the buildings. During office hours when the mechanical ventilation was on, the indoor radon level decayed and after the mechanical ventilation was off during non-office hours, the radon level increased. The average indoor radon level during office hours on the nine premises varied from 87 Bq/m3 to 296 Bq/m3, and the indoor averaged radon levels over both day time and night time periods without mechanical ventilation were about 25 percent higher. The air infiltration rate and the radon emission characteristics from the building materials were estimated from the radon build-up curves which were observed after the mechanical ventilation was off. The radon decay curve observed after the mechanical ventilation system was turned on was used to calculate the total fresh air intake rate. Average radon emanation rates of the building materials in the six buildings varied from 0.0019 to 0.0033 Bq/m2s. It has been found that building infiltration rate accounted for about 10-30 percent of the total building ventilation rate in the buildings depending on building tightness.     

Prevalence of irritative symptoms in a nonproblem air-conditioned office building

Objectives: To assess the prevalence of work-related complaints and symptoms in employees in an air-conditioned office building (Building AC) in a mild climatic area (Italy). No discomfort had previously been reported. Methods: A total of 198 employees in Building AC and 281 controls working in three naturally ventilated buildings (Building NV) answered a questionnaire investigating work-related complaints and symptoms. Results: A significantly higher percentage of workers in Building AC reported a lack of comfort in the working environment as compared with the controls (30.6% versus 18.9%). The most common complaints were strong lighting, high temperature, and dry, dusty, and/or stuffy air. The prevalence of ocular, upper airway, and cutaneous symptoms was significantly higher (29.8% versus 14.9%, 25.3% versus 9.6%, and 14.1% versus 3.6%, respectively). No significant difference was observed in respiratory or general symptoms. Logistic regression analysis showed that working with video display units and photocopiers influenced ocular symptoms; upper airway and cutaneous symptoms were influenced by female gender and working in the air-conditioned building. Conclusions: In an apparently healthy air-conditioned office building, complaints and symptoms are reported more often than in a naturally ventilated edifice, but the prevalence is lower than that usually observed in sick buildings. Symptoms are influenced by individual and work-related characteristics. Received: 17 September 1997 / Accepted: 26 February 1998     

Sick building syndrome: psychological, somatic, and environmental determinants

The authors aimed to examine potential relationships between work-related symptoms attributed to sick building syndrome (SBS) and certain psychological, somatic, and environmental factors. The multidisciplinary, cross-sectional study comprised 171 female subjects working in air-conditioned and naturally ventilated nonindustrial office buildings. The authors collected information concerning symptoms related to SBS and made assessments of quality of life by using appropriate questionnaires. They assessed the women's levels of emotional stability or neuroticism using the Cornell Index. They determined skin and airway reactivity markers and indoor microclimate data by using standardized methods. The study showed that the subjects had a high prevalence of fatigue (60.2%), sore and dry eyes (57.9%), and headache (44.4%), as well as a generally high score according to the SBS Index. Neuroticism and subjectively estimated physical health as well as the type of building ventilation significantly contributed to the prediction of the SBS Index, explaining 15% of the variance.     

Influence of personal characteristics, job-related factors and psychosocial factors on the sick building syndrome. Danish Indoor Climate Study Group

The influence of personal characteristics, life-style, job-related factors, and psychosocial work factors on symptoms of the sick building syndrome was investigated in Greater Copenhagen, Denmark. The buildings were not characterized beforehand as "sick" or "healthy." Of the 4369 employees sent a questionnaire, 3507 returned them. Multivariate logistic regression analyses of the multifactorial effects on the prevalence of work-related mucosal irritation and work-related general symptoms among the office workers showed that sex, job category, work functions (handling of carbonless paper, photocopying, work at video display terminals), psychosocial factors of work (dissatisfaction with superiors or colleagues and quantity of work inhibiting job satisfaction) were associated with work-related mucosal irritation and work-related general symptoms, but these factors could not account for the differences between the buildings as to the prevalence of the symptoms. The building factor (i.e., the indoor climate) was strongly associated with the prevalence of the symptoms.     

Sick building symptoms in office workers: a follow-up study before and one year after changing buildings

Influences of physical and psychosocial work environments andpersonal factors on sick building syndrome symptoms were investigatedin 167 clerical workers before and one year after moving froma naturally ventilated building to an artificially ventilatedbuilding. Female gender and work on visual display units wereindependently associated with most symptoms in the baselinesurvey and with the incident (new) symptoms in the follow-upsurvey. After changing buildings, the prevalences of eye, skinand fatigue symptoms increased significantly. Cold and discomfortdue to stuffiness were independently associated with incidenteye and respiratory symptoms. Reported domestic workloads weregreater for women, but did not account for any gender differencesin symptom prevalence.     

Effect of air humidification on the sick building syndrome and perceived indoor air quality in hospitals: a four month longitudinal study.

The sensation of dryness and irritation is essential in the sick building syndrome (SBS), and such symptoms are common in both office and hospital employees. In Scandinavia, the indoor relative humidity in well ventilated buildings is usually in the range 10-35% in winter. The aim of this study was to evaluate the effect of steam air humidification on SBS and perceived air quality during the heating season. The study base consisted of a dynamic population of 104 hospital employees, working in four new and well ventilated geriatric hospital units in southern Sweden. Air humidification raised the relative air humidity to 40-45% in two units during a four months period, whereas the other two units served as controls with relative humidity from 25-35%. Symptoms and perceived indoor air quality were measured before and after the study period by a standardised self administered questionnaire. The technical measurements comprised room temperature, air humidity, static electricity, exhaust air flow, aerosols, microorganisms, and volatile organic compounds in the air. The most pronounced effect of the humidification was a significant decrease of the sensation of air dryness, static electricity, and airway symptoms. After four months of air humidification during the heating season, 24% reported a weekly sensation of dryness in humidified units, compared with 73% in controls. No significant changes in symptoms of SBS or perceived air quality over time were found in the control group. The room temperature in all units was between 21-23 degrees C, and no significant effect of air humidification on the air concentration of aerosols or volatile organic compounds was found. No growth of microorganisms was found in the supply air ducts, and no legionella bacteria were found in the supply water of the humidifier. Air humidification, however, significantly reduced the measured personal exposure to static electricity. It is concluded that air humidification during the heating season in colder climates can decrease symptoms of SBS and perception of dry air.     

Objective assessment of ocular and respiratory alterations in employees in a sick building

Background Sick building syndrome (SBS) is a constellation of diffuse, “irritative” symptoms predominantly involving the eyes and the respiratory tract. To date, the effects of working in a “sick building” have not been adequately assessed using objective measures. We undertook the present study to determine whether objective alterations could be found in the eyes and respiratory tracts of employees working in an office building in which a high rate of SBS had been reported in the preceding year. Methods We studied 163 office workers: 87 workers from a modern, air-conditioned building (the sick building), and 76 employees employed in three traditional-style office buildings (the comparison buildings). After being surveyed for SBS symptoms, all subjects underwent a series of objective tests, including spirometry, a methacholine test, prick tests for aeroallergens, and submitted tear samples. In addition, Schirmer's test and the break-up time test were used to explore for potential ocular effects of sick building exposure. Results Employees in the sick building complained more frequently of ocular symptoms, upper-airway disturbances, and general and respiratory symptoms than did employees in the comparison buildings; prick tests were positive in 20% and 17.4%, respectively. Groups did not differ significantly on spirometry measures. Bronchial hyperreactivity to methacholine (PD15 = 16.348 μmol) was present in 20.5% of the sick building workers and in 16.2% of comparison buildings workers. Methacholine dose-response slope values were similar. Stability of tear film was significantly reduced (P< 0.01) in the employees in the sick building compared with employees in the comparison buildings. Conclusions Our results indicate that (1) atopy does not seem to influence the prevalence of SBS symptoms, and (2) the lower respiratory tract seems unaffected by exposure to a “sick building,” but (3) alterations in tear film stability do exist after such exposure. Am. J. Ind. Med. 34:79–88, 1998. © 1998 Wiley-Liss, Inc.     

广州市办公大楼集中空调通风系统卫生状况分析

目的了解广州市办公大楼集中空调通风系统卫生状况,为制定相应的防制对策提供依据。方法参照卫生部WS394—2012〈〈公共场所集中空调通风系统卫生规范》的要求,对广州市政府机构、商务大厦、政务中心等不同类型办公大楼的集中空调通风系统进行卫生状况调查。结果共调查办公大楼25家。商务大厦集中空调通风系统的卫生状况较差,空调送风中细菌总数合格率为48．00％、真菌总数合格率为66．OO％,细菌总数、真菌总数的最高浓度分别超出《卫生规范》中所规定限值的9倍、4倍以上。而政府机构和政务中心的卫生状况相对较好;空调送风中细菌总数合格率为59．20％、真菌总数合格率为76．00％,分别低于风管内表面细菌总数和真菌总数的合格率,差异有统计学意义（P〈0．05）,β-溶血性链球菌未检出;冷却水嗜肺军团菌检出率为48．00％,冷凝水嗜肺军团菌检出率为8．OO％。结论封闭式办公大楼集中空调通风系统卫生状况不容乐观,而针对封闭式大楼的办公环境制订一系列相应的国家卫生标准,应引起有关部门的重视和考虑,建议将办公大楼纳入公共场所卫生监督部门的监管范围。     

Influence of indoor climate on the sick building syndrome in an office environment. The Danish Indoor Climate Study Group

The influence of indoor climate factors on symptoms of the sick building syndrome was investigated in Greater Copenhagen, Denmark. Altogether, 2369 office workers in 14 buildings, where indoor climate measurements were made, filled out a questionnaire. Multivariate logistic regression analyses of the multifactorial effects on the prevalence of work-related mucosal irritation and work-related general symptoms among the office workers showed that the concentration of macromolecular organic floor dust, the floor covering, the number of workplaces in the office, the age of the building, the type of ventilation, and two easily recognizable factors, the shelf factor and the fleece factor, were associated with the prevalence of symptoms.     

Indoor endotoxin and glucan in association with airway inflammation and systemic symptoms.

Indoor bioaerosols (i.e., bacteria, fungi, endotoxin, and beta-1,3-glucan) were determined in daycare centers, office buildings, and domestic environments in the Taipei area. In addition, we used a questionnaire survey to determine associations between indoor dampness, bioaerosols, and airway inflammation and systemic symptoms. We demonstrated that the median levels of indoor bacteria and fungi were the highest in daycare centers, followed by those in homes and office buildings. Similar patterns were observed for endotoxin and beta-1,3-glucan. The prevalences of airway inflammation and systemic symptoms were higher for females in office buildings than for employees in daycare centers; all symptoms were more prevalent in females than males. With respect to the relationship between bioaerosol exposure and airway inflammation and systemic symptoms, we found a strong association between beta-1,3-glucan and lethargy/fatigue.