Klas Nordström

Uppsala University, Uppsala, Uppsala, Sweden

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Publications (12)18.78 Total impact

  • Dan Norbäck, Klas Nordström, Zhuohui Zhao
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    ABSTRACT: PURPOSE: To study the effects of a CO(2) demand-controlled ventilation system (variable flow) in computer classrooms on perceived air quality and sick building syndrome. METHODS: University students (27 % women) participated in a blinded study. Two classrooms had variable flow (mean 5.56 ac/h); two others had constant ventilation flow (mean 5.07 ac/h). After one week, ventilation conditions were shifted. The students reported symptoms/perceptions during the last hour on rating scales. Temperature, air humidity, CO(2), PM10 and number concentration of particles were measured simultaneously. Cat (Fel d 1), dog (Can f 1), horse (Equ cx) and house dust mites (Der f 1 and Der p 1) allergens were measured in dust. Those participating twice in the same classroom (N = 61) were analysed longitudinally. RESULTS: Mean CO(2) was 784 ppm (9 % of time >1,000 ppm) with variable flow and 809 ppm with constant flow conditions (25 % of time >1,000 ppm). Mean temperature (22.6 °C), PM10 (18 μg/m(3)) and number concentration (1,860 pt/cm(3)) were unchanged. The median levels of cat, dog, horse and Der f 1 allergens were 10,400 ng/g, 4,900 ng/g, 13,700 U/ng and 260 ng/g dust, respectively. There were slightly less headache (p = 0.003), tiredness (p = 0.007) and improved perceived air quality (p = 0.02) with variable flow. CONCLUSIONS: Use of a CO(2)-controlled ventilation system, reducing elevated levels of CO(2), may slightly reduce headache and tiredness and improve perceived air quality. The high levels of pet allergens, due to track in of allergens from the home and possible accumulation due to electrostatic forces, illustrate a need for improved cleaning.
    International Archives of Occupational and Environmental Health 03/2012; · 2.10 Impact Factor
  • Dan Norbäck, Klas Nordström
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    ABSTRACT: To study the effects of ventilation and temperature changes in computer classrooms on symptoms in students. Technical university students participated in a blinded study. Two classrooms had higher air exchange (4.1-5.2 ac/h); two others had lower (2.3-2.6 ac/h) air exchange. After 1 week, ventilation conditions were interchanged between the rooms. The students reported symptoms during the last hour, on a seven-step rating scale. Room temperature, relative air humidity (RH) carbon dioxide (CO(2)), PM10 and ultra-fine particles (UFP) were measured simultaneously (1 h). Illumination, air velocity, operative temperature, supply air temperature, formaldehyde, NO(2) and O(3) were measured. Multiple logistic regression was applied in cross-sectional analysis of the first answer (N = 355). Those participating twice (N = 121) were analysed longitudinally. Totally 31% were females, 2.9% smokers and 3.8% had asthma. Mean CO(2) was 993 ppm (674-1,450 ppm), temperature 22.7 degrees C (20-25 degrees C) and RH 24% (19-35%). Lower and higher air exchange rates corresponded to a personal outdoor airflow of 7 l/s*p and 10-13 L/s*P, respectively. Mean PM10 was 20 microg/m(3) at lower and 15 microg/m(3) at higher ventilation flow. Ocular, nasal and throat symptoms, breathlessness, headache and tiredness were significantly more common at higher CO(2) and temperature. After mutual adjustment, ocular (OR = 1.52 per 1 degrees C), nasal (OR = 1.62 per 1 degrees C) and throat symptoms (OR = 1.53 per 1 degrees C), headache (OR = 1.51 per 1 degrees C) and tiredness (OR = 1.54 per 1 degrees C) were significantly associated with temperature; headache was associated only with CO(2) (OR = 1.19 per 100 ppm CO(2)). Longitudinal analysis demonstrated that increased room temperature was related to tiredness (P < 0.05). Computer classrooms may have CO(2) above 1,000 ppm and temperatures above 22 degrees C. Increased temperature and CO(2) may affect mucosal membrane symptoms, headaches and tiredness. Room temperature was most important. CO(2) associations may partly be temperature effects.
    International Archives of Occupational and Environmental Health 10/2008; 82(1):21-30. · 2.10 Impact Factor
  • D Norbäck, K Nordström
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    ABSTRACT: The effects of ventilation in computer classrooms were studied with university students (n = 355) in a blinded study, 31% were women and 3.8% had asthma. Two classrooms had a higher air exchange (4.1-5.2 ac/h); two others had a lower air exchange (2.3-2.6 ac/h). After 1 week, ventilation conditions were shifted. The students reported environmental perceptions during the last hour. Room temperature, RH, CO2, PM10 and ultra-fine particles were measured simultaneously. Mean CO2 was 1185 ppm at lower and 922 ppm at higher air exchange. Mean temperature was 23.2 degrees C at lower and 22.1 degrees C at higher air exchange. After mutual adjustment (temperature, RH, CO2, air exchange), measured temperature was associated with a perception of higher temperature (P < 0.001), lower air movement (P < 0.001), and poorer air quality (P < 0.001). Higher air exchange was associated with a perception of lower temperature (P < 0.001), higher air movement (P = 0.001), and better air quality (P < 0.001). In the longitudinal analysis (n = 83), increased air exchange caused a perception of lower temperature (P = 0.002), higher air movement (P < 0.001), better air quality (P = 0.001), and less odor (P = 0.02). In conclusion, computer classrooms have CO2 levels above 1000 ppm and temperatures above 22 degrees C. Increased ventilation from 7 l/s per person to 10-13 l/s per person can improve thermal comfort and air quality. PRACTICAL IMPLICATIONS: Computer classrooms are crowded indoor environments with a high thermal load from both students and computer equipment. It is important to control room temperature either by air conditioning, sun shields, or sufficiently high ventilation flow. A high ventilation flow is also crucial to achieving good perceived air quality. Personal ventilation flow should be at least 10 l/s. Possible loss of learning ability due to poor indoor air quality in university buildings deserves more attention.
    Indoor Air 04/2008; 18(4):293-300. · 3.30 Impact Factor
  • Dan Norbäck, Klas Nordström
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    ABSTRACT: An abstract is unavailable. This article is available as HTML full text and PDF.
    World Allergy Organization Journal 10/2007;
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    ABSTRACT: Asthma symptoms in adults in relation to the indoor environment. To study the relationships between current asthma symptoms (wheeze or attacks of breathlessness) and the indoor environment and dampness in hospitals. A study among personnel (n = 87) in four geriatric hospitals in winter. Indoor air pollutants, dampness in the concrete floor, and allergens in settled dust were measured. Multiple logistic regression analysis was applied, adjusting for age, sex, atopy, and dampness in the participants' own dwellings. Current asthma symptoms were reported by 17%, and 8% had doctor's diagnosed asthma. Asthma symptoms were more common (adjusted odds ratio = 8.6; 95% confidence interval 1.3-56.7) in two buildings with signs of dampness-related degradation of di(ethylhexyl)-phthalate (DEHP) in polyvinyl chloride (PVC) floor material, detected as presence of 2-ethyl-1-hexanol (2-32 microg/m3) in indoor air (CAS nr 104-76-7). Asthma symptoms were related to higher relative humidity in the upper concrete floor construction, and ammonia in the floor. The newest hospital, built by an anthroposophic society, had low levels of dampness and few asthma symptoms (4%). Cat (Fel d1) and dog allergens (Can f1) were found in dust from all buildings (geometric mean 340 ng/g and 2490 ng/g, respectively). House dust mite allergens (Derp1, Derf1, or Derm1) were found in 75% of all samples (geometric mean 130 ng/g). There was no relationship between allergen levels and asthma symptoms. Asthma symptoms may be related to increased humidity in concrete floor constructions and emission of 2-ethyl-1-hexanol, an indicator of dampness-related alkaline degradation of plasticiser DEHP. Moreover, geriatric hospitals can be contaminated by significant amounts of cat, dog and mite allergens.
    The International Journal of Tuberculosis and Lung Disease 12/2000; 4(11):1016-25. · 2.76 Impact Factor
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    ABSTRACT: Air humidification is sometimes used to reduce dryness symptoms in temperate climates, but the biological mechanism behind this effect is not well understood. We have investigated the effect of air humidification on physiological signs from the eyes and nose, other medi cal symptoms and on perceived air quality. An experi mental study was performed in two units of a well-venti lated geriatric hospital in southern Sweden. Blinded cen tral steam air humidification in one of the units during 6 weeks raised the relative air humidity to 43% RH (Janu ary-March 1997), while the other unit with 35% RH served as control. All staff (N = 32) working the day shift were invited to undergo a medical investigation per formed in the hospital units. It included measurement of tear film stability, acoustic rhinometry, nasal lavage and completing a medical questionnaire. The investigation was repeated at both units after 6 weeks and 26 subjects participated on both occasions (81 %). The technical mea surements were room temperature, relative air humidity
    Indoor and Built Environment 01/2000; 9(1):28-34.
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    ABSTRACT: To study the relationships between dampness in concrete floors and building design on the one hand, and symptoms and medical signs of the eyes and nose in hospital workers, on the other. Four hospitals for geriatrics were selected to represent buildings with different ages and design, irrespective of symptom prevalence. The first building was built in 1925. The second, built in 1985, was known to have dampness in the floor. Conventional building techniques were used in the third building, built in 1993, and the last building was built in 1994, and was specially designed to include high ceilings, and minimal use of fluorescent lighting and interior plastic materials. The interior surfaces were painted with water-based beeswax glazing. All staff (n=95) working day shifts were invited to take part in a medical examination of the eyes and nose including acoustic rhinometry and nasal lavage, and a medical questionnaire, and 93% participated. Measurements of temperature, relative air humidity, air flow, illumination, volatile organic compounds (VOCs), molds, and bacteria were carried out in all buildings, together with measurements of formaldehyde, respirable dust, carbon monoxide (CO), carbon dioxide (CO(2)), nitrogen dioxide (NO(2)) and ozone. Statistical analyses were performed by bivariate analysis, and linear, ordinal, and logistic multiple regressions, adjusting for age, gender, tobacco smoking, atopy, and the perceived psychosocial work environment. Dampness in the upper concrete floor surface (75-84%), ammonia under the floor [3 parts per million (ppm)], and 2-ethyl-1-hexanol in the air were detected in the two buildings built in 1985 and 1993. Increased occurrences of ocular and nasal symptoms, an increased concentration of lysozyme in nasal lavage, and decreased tear film stability were found in the subjects working in the damp buildings. Those in the specially designed building had fewer ocular and nasal symptoms, and increased tear film stability. All buildings had low levels of formaldehyde, molds, bacteria, ozone, and NO(2). The lowest total concentration of VOCs, and the highest concentration of specific VOCs of microbial origin, were found in the building with special design. The study provides new evidence of the role of dampness-related alkaline degradation of di-(2-ethylhexyl) phthalate (DEHP) in polyvinyl chloride (PVC) building material. Emissions related to degradation of DEHP due to dampness in the floor, indicated by increased 2-ethyl-1-hexanol in the air, seem to increase both the secretion of lysozyme from the nasal mucosa and the occurrence of ocular and nasal symptoms. The indoor environment of the specially designed building with high ceilings and no fluorescent lighting or interior plastics seemed to have a positive influence on the nasal and ocular mucous membranes.
    International Archives of Occupational and Environmental Health 11/1999; 72(7):451-61. · 2.10 Impact Factor
  • K. Nordström, D. Norbäck, G. Wieslander
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    ABSTRACT: This investigation studied subjective indoor air quality (IAQ) in hospitals in relation to building dampness and the type of construction. Building dampness is known to be an important contributor to perception of the indoor environment. Dampness in floor construction is known to cause chemical degradation of polyvinyl chloride floor coatings, but few epidemiological studies on this topic have been published. Another topic of interest is the dif ferent IAQ in buildings constructed with different build ing materials and to different architectural designs. We looked at four geriatric hospital buildings of different age and design chosen without regard to the level of com plaints. The first was built in 1925 and redecorated in 1955. The second, built in 1985, had known dampness in the floor construction. The other two, built in 1993 and 1995, were constructed to conventional and 'alternative' building designs, respectively. Eighty-eight, from a total of 95 staff, answered a questionnaire on subjective IAQ. Indoor measurements of room temperature, relative air humidity, air flow rate, illumination, moulds, bacteria, formaldehyde and other volatile compounds, respirable dust, carbon monoxide, carbon dioxide, nitrogen dioxide and ozone were performed in all buildings. Statistical analysis was performed by multiple logistic regression, adjusting for a possible influence of building age, age of the subjects, gender, tobacco smoke and atopy. Damp ness in the upper concrete floor surface (75-84%), am monia under the floor (3 ppm), and 2-ethyl-1-hexanol in the air were detected in the two buildings built in 1985 and 1993. Complaints on air dryness and stuffy air were significantly commoner in these damp buildings. The subjects in the buildings constructed to an 'alternative' design had significantly fewer complaints about stuffy air, dry air and static electricity as compared to the other buildings. The average room temperature was similar (22.0-23.0°C) in all buildings. All buildings had low lev els of formaldehyde, moulds and bacteria. In conclusion, building dampness in the floor construction may in crease the sensation of air dryness and stuffy air. In con trast, the high proportion of satisfied inhabitants in the alternative-design building shows that it is possible to construct a new building with good subjective IAQ.
    Indoor and Built Environment 01/1999; 8(1):49-57.
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    ABSTRACT: Building dampness in the floor construction is known to cause chemical degradation of polyvinyl chloride floor coatings, but few epidemiological studies on this topic have been published. Another topic of interest is the different symptoms in different buildings constructed with different building materials and with different architectural designs. The term Sick Building Syndrome (SBS) is sometimes used to describe irritation to the eyes, skin, and upper airways, headache and fatigue in relation to the indoor environment. The aim of our investigation was to study symptoms in relation to building dampness and type of building in geriatric hospitals. Four hospitals for geriatrics were selected to represent buildings with different ages and design, irrespectively of symptom prevalence. All staff (n = 95) were requested to answer a medical questionnaire, 88 (93%) participated. Measurements of room temperature, relative air humidity, air flow rate, illumination, moulds, bacteria, formaldehyde and other volatile compounds, respirable dust, carbon monoxide, carbon dioxide, nitrogen dioxide and ozone were carried out in all buildings. Statistical analyses were performed by bivariate analysis, and multiple logistic regression, adjusting for possible influence of building age, age of the subjects, gender, tobacco smoke, atopy and the perceived psychosocial work environment. Dampness in the upper concrete floor surface (75–84%), ammonia under the floor [3 parts per million (3 ppm)], and 2-ethyl-1-hexanol in the air were detected in two buildings built in 1985 and 1993. Increased occurrence of ocular, nasal and throat symptoms, and dry facial skin were found in the damp buildings. Those in the specially designed building had fewer of these symptoms. In conclusion, the study provides new evidence on possible health effects of dampness-related alkaline degradation of di(2-ethyl-hexyl) phthalate (DEPH) in PVC-building material. Emissions related to degradation of DEPH due to dampness in the floor construction, detected by an increase of 2-ethyl-1-hexanol in the air, seems to increase the occurrence of ocular, nasal, throat and facial skin symptoms. The indoor environment of one specially designed building with a high ceiling and avoidance of fluorescent lighting and interior plastic materials, seemed to have a positive influence on well-being. Our results support the view that building dampness should be avoided, and shows that it is possible to construct a new building where the inhabitants have few symptoms. Copyright © 1999 John Wiley & Sons, Ltd.
    Journal of Environmental Medicine 01/1999; 1(3):127-135.
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    K Nordström, D Norbäck, R Akselsson
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    ABSTRACT: Sick building syndrome (SBS) involves symptoms such as irritation to the eyes, skin, and upper airways, headache, and fatigue. The relations between such symptoms and both personal and environmental factors were studied in 225 female hospital workers, working in eight hospital units in the south of Sweden. Symptoms of SBS and personal factors were measured by means of a standardised self administered questionnaire. The technical investigation comprised a building survey and measurements of room temperature, supply air temperature, air humidity, and exhaust air flow. The prevalence of symptoms differed from one unit to another. The mean value of weekly complaints of fatigue was 30%, of eye irritation 23%, and of dry facial skin 34%. Eye irritation was related to work stress, self reported exposure to static electricity, and was also more common in buildings with a high ventilation flow and a high noise level (55 dB(A)) from the ventilation system. Nasal symptoms were related to asthma and hay fever only. Throat symptoms were more common in smokers, subjects with asthma or hay fever, new buildings, and in buildings with a high ventilation flow. Facial skin irritation was related to a lack of control of the work conditions, and was more common in new buildings, and buildings with a high ventilation flow and ventilation noise. General symptoms, such as headache and fatigue, were related to current smoking, asthma or hay fever, work dissatisfaction, and static electricity. As the prevalence of symptoms was high, there is a need to improve the indoor environment as well as the psychosocial environment in hospitals. These improvements could include a reduction of ventilation noise, minimised smoking, and improvements in the psychosocial climate. Further research is needed to identify indoor climatic factors that cause the increased prevalence of symptoms of SBS in new buildings.
    Occupational and Environmental Medicine 04/1995; 52(3):170-6. · 3.22 Impact Factor
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    K Nordström, D Norbäck, R Akselsson
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    ABSTRACT: 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.
    Occupational and Environmental Medicine 11/1994; 51(10):683-8. · 3.22 Impact Factor
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    Klas Nordström, Dan Norbäck, Roland Akselsson
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    ABSTRACT: Sumario: The sick building syndrome (SBS) involves non-specific symptoms such as irritation to the eyes, skin, and upper airways, headache, and fatigue. In recent years, several epidemiological or experimental investigations on such symptoms have been published. This study had two aims. The main aim of this study was to evaluate the effect of steam air humidification on SBS and perceived air quality during the heating season. The second aim was to study possible effects of air humidification on selected physical, chemical, and microbiological exposures in the buildings