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Monitoring of symptoms in estimating the effect of intervention in the sick building syndrome: A field study
Environment International, Vol. 15, pp. 159 - 162, 1989 Printed in the U.S.A. All righu reserved.
0160-4120/89 $3.00 +.00 Copyright ©1989 Pergamon Press plc
MONITORING OF SYMPTOMS IN ESTIMATING THE EFFECT OF INTERVENTION IN THE SICK BUILDING SYNDROME: A FIELD STUDY Loif Hansen Danish Labour InspectionService, Copenhagen, Denmark E187-433 (Received5 November 1987; Accepted 5 May 2989).
Employees in six day-care institutions were asked to fill out a simple questionnaire before and one year after technical changes were made in their buildings. The institutions were defined as sick buildings, based on a prevalence (exceeding 40%) of irritative symptoms and general symptoms among the employees. Based on the technical measurements there were no obvious reasons for the complaints. It was decided, however, to remove man-made mineral-acoustic ceilings and to install mechanical ventilation. One year later there was a significant reduction in the prevalence of symptoms (irritative and general symptoms related to the sick building syndrome) among the employees. The study indicates that systematic monitoring of employees' symptoms before and after corrective action is an important indicator of the benefit of the actions and might be used routinely by architects, engineers, and local authorities in dealing with indoor climate problems. Follow-up studies might give more knowledge of the causes of sick building syndrome.
INTRODUCTION
architects, engineers, and authorities in cases where major changes are planned in buildings. These follow-up studies should include a health surveillance. The aim of this field study was twofold: 1. To determine if corrective changes in six buildings had an effect on the prevalence of irritative or general symptoms among employees. 2. To develop a health surveillance method to be used by engineers, local authorities, and occupational health services routinely in estimating the effect of changes in buildings with SBS. The method should be simple and prospective. The persons suffering from SBS should be their own control. Data should be quantified. A "healthy-worker effect" should be evaluated, and information-bias/placebo effect should be diminished or evaluated.
The sick building syndrome (SBS) is characterized by occupants of a building having a greater frequency of symptoms. Upon medical examination there are often few or no abnormalities (Akimenko et al. 1986). Epidemiological studies have focused on irritation of the mucous membranes (eyes, nose, skin, or throat) and general symptoms (headache, abnormal fatigue, or malaise) (Skov and Valbjern 1987). Various exposures have been related to SBS, but technical measurements of the exposures arc in many cases of limited value. Corrective actions based on technical measurements do not always put a stop to the complaints (Hanssen and Redahl 1984). Many studies concerning technical control of exposures and ventilation effectiveness have been done, but only seldom are corrective actions combined with a systematic registration of the symptoms among the occupants/employees (Nex¢ ¢t al. 1984; Jaakkala and Heinonen 1987). As recommended by Akimcnko et al. (1986), there is a need for follow-up studies that can be used by
MATERIALS AND METHODS
Six day-care institutions for children (ages 2 to 10 years) were included in the study. All the institutions belonged to the same local urban region. The sick buildings were defined as buildings with a frequency 159
160
Leif Han,~en
of more than 40% of irritative work-related symptoms (irritation of the eyes, nose, skin, or throat) and general work-related symptoms (headache, fatigue, or malaise) among the 62 employees (50 females and 12 males; mean age 27 years). A short questionnaire was used to register symptoms among employees. The questionnaires were introduced and distributed in the institutions and returned in sealed envelopes. The study was performed in May 1982 and May 1983. The same questionnaire was used during both registrations. Questions about lifestyle, alcohol consumption, and private and social problems were not included, since it is unlikely that on a group-basis these factors would change when each person was his own control one year after the initial registration. The questions included in the symptom registration were: When you are at work, do you have the following symptoms: itching, dryness, or irritation of the eyes; blocked or runny nose or irritation.; irritation or sensations of dryness in the throat; irritation or dryness of the skin; skin rash; feelings of heavy headedness; headache; abnormal tiredness; nausea or dizziness. Possible answers to the individual questions were: "No"; "Yes, but less than once a week"; "Yes, once or twice a week"; "Yes, three or four days a week"; "Yes, daily." The intervention was the removal of the (acoustic) man-made mineral-fibers (MMMF) ceilings and the installation of mechanical ventilation (outside air without recirculation or humidification). The mechanical ventilation was designed to give a ventilation rate of three times per hour.
RESULTS
The characteristics of the buildings are given in Table I. The response rate among employees in the firstregistration was 89%. In the second registration a year later the response rate was 72%, including five persons who had not responded during the firstregistration. The employees (15) who responded in the firstregistration but not the second were traced. Most of them (10) had left the institutions. None of these persons indicated during personal interviews that the indoor climate was the cause for their leaving the institutions. The prevalence of the symptoms for the six institutions before and after interventions is given in Table 2. Only data for symptoms more frequent than three days or more a week are given. In the second registration five persons who did not respond during the firstregistration are included. Statistical analyses (ZZtest) were applied to the replies. The symptoms for eyes, nose, throat, head feels heavy, and fatigue were significantly less after one year. For symptoms related to skin, headache, and nausea/dizziness, the differences were not significant, but the trends were in the same downward direction. Including only persons responding twice (40 persons), in order to correct a possible "healthy worker's effect," differences were still significant (p <0.01) for symptoms from eyes, nose, head feels heavy, and fatigue. In Table 3, the relative changes in frequency of symptoms are given. Only persons responding twice are included. The figures in Table 3 cannot be corn-
Table 1. Technical characteristics of the buildings before intervention. Walls: brick-stone
Age: 5 to I0 years Floor: linoleum Ceilings: Man-made mineral-fiber plates (water-based glue) No water damage Preliminary technical measurements: Carbon dioxide: 40 - 270 mL]L Temperature: 18.5 - 19.5°C Ventilation rate: 0.7 - 1.5 per hour Estimated fresh air: 6.3 m 3 per hour per person (including children) Organic dust: 0.33 mg/m 3 MIvIMF counts: 14000 fibers/m 3 (one institution)
Intervention in the sick building syndrom
161
Table 2. Work-related symptoms among employees. Symptom
Before intervention
A f t e r intervention
May 1982
M a y 1983
N = 55
N = 45
Percentage
Percentage
P-value chi-square test
Eyes
42*
4
< 0.001
Nose
53
22*
< 0.01
Throat
40
16"
< 0.01
Skin
43 38
Headache
15"
Fatigue
41 12
35 li 9 14 4
N.S.
Head feels heavy
Nausea/dizziness
< 0.01 N.S. < 0.01 N.S.
*one non responder to the question (2%) * * t h r e e non responders to the question (7%)
pared with the figures in Table 2 since all changes in symptom frequency are included in Table 3. Also, persons with symptoms less frequent than three days a week are included. Statistic analyses (Sign test) showed a significant decline in the symptoms one year later. The beneficial effect of the intervention was confirmed by interviews of security representatives of the employees, who stated that the indoor climate had improved. This information was given before the employees knew the results of the study. DISCUSSION
The reduction of symptoms could be a placeboeffect/information-bias, since the employees know of
the corrective actions (and wanted them). Since the second registration took place one year after the intervention, it is unlikely, however, that a placeboeffect would last that long. From a scientific point of view, however, it cannot be excluded. A blind procedure, where the employees do not know of corrective actions, is seldom feasible in real life. This study showed a decline in the prevalence of irritative and general symptoms one year after the intervention. It is not possible to evaluate which part of the intervention (removal of the MMMF ceilings or installation of mechanical ventilation) was more important. As long as SBS is not better defined, it is necessary to monitor symptoms in evaluating the benefits of intervention. Technical measurements alone before and
Table 3. Percentage of employees with a decline or an increase in symptomsone year after intervention (N=40). Symptom
Less frequent
More frequent
p
Eyes
63
5
< 0.001
Nose
b,8
5
< 0.001
Throat
53
18
< 0.05
Skin
35
10
< 0.05
H e a d feels heavy
58
5
< 0.001
Headache
48
5
< 0.001
Fatigue
50
3
< 0.001
Nausea/dizziness
43
8
< 0.0l
162
after intervention are not sufficient when the mechanism behind SBS is unknown. Most studies of SBS are cross-sectional studies in which technical measurements are linked to the prevalence of symptoms. These studies have the disadvantage of problems with confounder-control (age, sex, smoking habits, life-style, social problems, and "healthy worker's effect"). A prospective study has many advantages because the study-group is the same before and after corrective actions. Is a simple registration of symptoms (irritative and general) among the occupants/employees in sick buildings more useful than studies (on a cross-sectional. basis) including intensive medical and technical measurements? For persons suffering from SBS the important thing is that the symptoms disappear or at least diminish. It is a distressing fact that billions of dollars are spent on corrective actions, but that an evaluation of the effect of the symptoms is seldom performed. A systematic registration of the kind of intervention implying a decline in symptoms will make it possible to suggest a new hypothesis regarding the mechanism behind SBS. This new hypothesis must then be tested in further studies that include both detailed technical measurements and medical surveys. In this study, the severity of symptoms cannot be evaluated from the questionnaires, since only the prevalence of the symptoms is registered. Persons with severe symptoms should always be examined by a physician because a serious disease can be mistaken for SBS. In most cases of SBS, however, there are none or few objective clinical abnormalities, and it is unnecessary to perform intensive medical examinations.
Leif Hansen
With regard to the development of a health surveillance method, this study is only a pilot study. The questions and the methods must be tested further. There is a need for developing standardized health surveillance programs that can be used routinely in dealing with indoor air climate problems. The questionnaire used in this study might be such a surveillance tool, but it must be further tested and standardized. If used routinely, a simple computer program can be developed. Some problems must not be ignored: if the health surveillance program includes only a few persons (buildings with less than ten occupants/employees), statistical analysis cannot be informative. Personal interviews before and after intervention might be a better alternative. Another alternative is to use persons with hyperreactive airways (e.g., asthma) as indicator-persons (Nex¢ et al. 1984). REFERENCES Akimenko, V.V.; Andersen, I.; Lewobitz, M.D.; Lindvall, I". The sick building syndrome: evaluations and conclusions for health science and technology. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate, Swedish Council for Building Research, Stockholm, 6:87-97; 1986. Hanssen, S.O.; Redahl, E. An office environment --problems and improvements. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate, Swedish Council for Building Research, Stockholm, 3:303-305; 1984. ~[aakkala, J.K.; Heinonen, O.P. Mechanical ventilation in an office building and sick building syndrome: a short trial.Proceedings of the 4th International Conference on Indoor Air Quality and Climate, Institute for Water, Soil and Air Hygiene, Berlin, 2:454-548; 1987. Nex¢, E.; Skov, P.; Gravesen, S. Extreme fatigue and malaise a syndrome caused by badly cleaned wall-to-wall carpets. Ecol. Disease. 2:415-418; 1984. Skov, P.; Valbjern, O. The sick building syndrome in the office environment. Proceedings of the 4th International Conference on Indoor Air Quality and Climate, Institute for Water, Soil and Air Hygiene, Berlin 2:439-443; 1987.
0160-4120/89 $3.00 +.00 Copyright ©1989 Pergamon Press plc
MONITORING OF SYMPTOMS IN ESTIMATING THE EFFECT OF INTERVENTION IN THE SICK BUILDING SYNDROME: A FIELD STUDY Loif Hansen Danish Labour InspectionService, Copenhagen, Denmark E187-433 (Received5 November 1987; Accepted 5 May 2989).
Employees in six day-care institutions were asked to fill out a simple questionnaire before and one year after technical changes were made in their buildings. The institutions were defined as sick buildings, based on a prevalence (exceeding 40%) of irritative symptoms and general symptoms among the employees. Based on the technical measurements there were no obvious reasons for the complaints. It was decided, however, to remove man-made mineral-acoustic ceilings and to install mechanical ventilation. One year later there was a significant reduction in the prevalence of symptoms (irritative and general symptoms related to the sick building syndrome) among the employees. The study indicates that systematic monitoring of employees' symptoms before and after corrective action is an important indicator of the benefit of the actions and might be used routinely by architects, engineers, and local authorities in dealing with indoor climate problems. Follow-up studies might give more knowledge of the causes of sick building syndrome.
INTRODUCTION
architects, engineers, and authorities in cases where major changes are planned in buildings. These follow-up studies should include a health surveillance. The aim of this field study was twofold: 1. To determine if corrective changes in six buildings had an effect on the prevalence of irritative or general symptoms among employees. 2. To develop a health surveillance method to be used by engineers, local authorities, and occupational health services routinely in estimating the effect of changes in buildings with SBS. The method should be simple and prospective. The persons suffering from SBS should be their own control. Data should be quantified. A "healthy-worker effect" should be evaluated, and information-bias/placebo effect should be diminished or evaluated.
The sick building syndrome (SBS) is characterized by occupants of a building having a greater frequency of symptoms. Upon medical examination there are often few or no abnormalities (Akimenko et al. 1986). Epidemiological studies have focused on irritation of the mucous membranes (eyes, nose, skin, or throat) and general symptoms (headache, abnormal fatigue, or malaise) (Skov and Valbjern 1987). Various exposures have been related to SBS, but technical measurements of the exposures arc in many cases of limited value. Corrective actions based on technical measurements do not always put a stop to the complaints (Hanssen and Redahl 1984). Many studies concerning technical control of exposures and ventilation effectiveness have been done, but only seldom are corrective actions combined with a systematic registration of the symptoms among the occupants/employees (Nex¢ ¢t al. 1984; Jaakkala and Heinonen 1987). As recommended by Akimcnko et al. (1986), there is a need for follow-up studies that can be used by
MATERIALS AND METHODS
Six day-care institutions for children (ages 2 to 10 years) were included in the study. All the institutions belonged to the same local urban region. The sick buildings were defined as buildings with a frequency 159
160
Leif Han,~en
of more than 40% of irritative work-related symptoms (irritation of the eyes, nose, skin, or throat) and general work-related symptoms (headache, fatigue, or malaise) among the 62 employees (50 females and 12 males; mean age 27 years). A short questionnaire was used to register symptoms among employees. The questionnaires were introduced and distributed in the institutions and returned in sealed envelopes. The study was performed in May 1982 and May 1983. The same questionnaire was used during both registrations. Questions about lifestyle, alcohol consumption, and private and social problems were not included, since it is unlikely that on a group-basis these factors would change when each person was his own control one year after the initial registration. The questions included in the symptom registration were: When you are at work, do you have the following symptoms: itching, dryness, or irritation of the eyes; blocked or runny nose or irritation.; irritation or sensations of dryness in the throat; irritation or dryness of the skin; skin rash; feelings of heavy headedness; headache; abnormal tiredness; nausea or dizziness. Possible answers to the individual questions were: "No"; "Yes, but less than once a week"; "Yes, once or twice a week"; "Yes, three or four days a week"; "Yes, daily." The intervention was the removal of the (acoustic) man-made mineral-fibers (MMMF) ceilings and the installation of mechanical ventilation (outside air without recirculation or humidification). The mechanical ventilation was designed to give a ventilation rate of three times per hour.
RESULTS
The characteristics of the buildings are given in Table I. The response rate among employees in the firstregistration was 89%. In the second registration a year later the response rate was 72%, including five persons who had not responded during the firstregistration. The employees (15) who responded in the firstregistration but not the second were traced. Most of them (10) had left the institutions. None of these persons indicated during personal interviews that the indoor climate was the cause for their leaving the institutions. The prevalence of the symptoms for the six institutions before and after interventions is given in Table 2. Only data for symptoms more frequent than three days or more a week are given. In the second registration five persons who did not respond during the firstregistration are included. Statistical analyses (ZZtest) were applied to the replies. The symptoms for eyes, nose, throat, head feels heavy, and fatigue were significantly less after one year. For symptoms related to skin, headache, and nausea/dizziness, the differences were not significant, but the trends were in the same downward direction. Including only persons responding twice (40 persons), in order to correct a possible "healthy worker's effect," differences were still significant (p <0.01) for symptoms from eyes, nose, head feels heavy, and fatigue. In Table 3, the relative changes in frequency of symptoms are given. Only persons responding twice are included. The figures in Table 3 cannot be corn-
Table 1. Technical characteristics of the buildings before intervention. Walls: brick-stone
Age: 5 to I0 years Floor: linoleum Ceilings: Man-made mineral-fiber plates (water-based glue) No water damage Preliminary technical measurements: Carbon dioxide: 40 - 270 mL]L Temperature: 18.5 - 19.5°C Ventilation rate: 0.7 - 1.5 per hour Estimated fresh air: 6.3 m 3 per hour per person (including children) Organic dust: 0.33 mg/m 3 MIvIMF counts: 14000 fibers/m 3 (one institution)
Intervention in the sick building syndrom
161
Table 2. Work-related symptoms among employees. Symptom
Before intervention
A f t e r intervention
May 1982
M a y 1983
N = 55
N = 45
Percentage
Percentage
P-value chi-square test
Eyes
42*
4
< 0.001
Nose
53
22*
< 0.01
Throat
40
16"
< 0.01
Skin
43 38
Headache
15"
Fatigue
41 12
35 li 9 14 4
N.S.
Head feels heavy
Nausea/dizziness
< 0.01 N.S. < 0.01 N.S.
*one non responder to the question (2%) * * t h r e e non responders to the question (7%)
pared with the figures in Table 2 since all changes in symptom frequency are included in Table 3. Also, persons with symptoms less frequent than three days a week are included. Statistic analyses (Sign test) showed a significant decline in the symptoms one year later. The beneficial effect of the intervention was confirmed by interviews of security representatives of the employees, who stated that the indoor climate had improved. This information was given before the employees knew the results of the study. DISCUSSION
The reduction of symptoms could be a placeboeffect/information-bias, since the employees know of
the corrective actions (and wanted them). Since the second registration took place one year after the intervention, it is unlikely, however, that a placeboeffect would last that long. From a scientific point of view, however, it cannot be excluded. A blind procedure, where the employees do not know of corrective actions, is seldom feasible in real life. This study showed a decline in the prevalence of irritative and general symptoms one year after the intervention. It is not possible to evaluate which part of the intervention (removal of the MMMF ceilings or installation of mechanical ventilation) was more important. As long as SBS is not better defined, it is necessary to monitor symptoms in evaluating the benefits of intervention. Technical measurements alone before and
Table 3. Percentage of employees with a decline or an increase in symptomsone year after intervention (N=40). Symptom
Less frequent
More frequent
p
Eyes
63
5
< 0.001
Nose
b,8
5
< 0.001
Throat
53
18
< 0.05
Skin
35
10
< 0.05
H e a d feels heavy
58
5
< 0.001
Headache
48
5
< 0.001
Fatigue
50
3
< 0.001
Nausea/dizziness
43
8
< 0.0l
162
after intervention are not sufficient when the mechanism behind SBS is unknown. Most studies of SBS are cross-sectional studies in which technical measurements are linked to the prevalence of symptoms. These studies have the disadvantage of problems with confounder-control (age, sex, smoking habits, life-style, social problems, and "healthy worker's effect"). A prospective study has many advantages because the study-group is the same before and after corrective actions. Is a simple registration of symptoms (irritative and general) among the occupants/employees in sick buildings more useful than studies (on a cross-sectional. basis) including intensive medical and technical measurements? For persons suffering from SBS the important thing is that the symptoms disappear or at least diminish. It is a distressing fact that billions of dollars are spent on corrective actions, but that an evaluation of the effect of the symptoms is seldom performed. A systematic registration of the kind of intervention implying a decline in symptoms will make it possible to suggest a new hypothesis regarding the mechanism behind SBS. This new hypothesis must then be tested in further studies that include both detailed technical measurements and medical surveys. In this study, the severity of symptoms cannot be evaluated from the questionnaires, since only the prevalence of the symptoms is registered. Persons with severe symptoms should always be examined by a physician because a serious disease can be mistaken for SBS. In most cases of SBS, however, there are none or few objective clinical abnormalities, and it is unnecessary to perform intensive medical examinations.
Leif Hansen
With regard to the development of a health surveillance method, this study is only a pilot study. The questions and the methods must be tested further. There is a need for developing standardized health surveillance programs that can be used routinely in dealing with indoor air climate problems. The questionnaire used in this study might be such a surveillance tool, but it must be further tested and standardized. If used routinely, a simple computer program can be developed. Some problems must not be ignored: if the health surveillance program includes only a few persons (buildings with less than ten occupants/employees), statistical analysis cannot be informative. Personal interviews before and after intervention might be a better alternative. Another alternative is to use persons with hyperreactive airways (e.g., asthma) as indicator-persons (Nex¢ et al. 1984). REFERENCES Akimenko, V.V.; Andersen, I.; Lewobitz, M.D.; Lindvall, I". The sick building syndrome: evaluations and conclusions for health science and technology. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate, Swedish Council for Building Research, Stockholm, 6:87-97; 1986. Hanssen, S.O.; Redahl, E. An office environment --problems and improvements. Proceedings of the 3rd International Conference on Indoor Air Quality and Climate, Swedish Council for Building Research, Stockholm, 3:303-305; 1984. ~[aakkala, J.K.; Heinonen, O.P. Mechanical ventilation in an office building and sick building syndrome: a short trial.Proceedings of the 4th International Conference on Indoor Air Quality and Climate, Institute for Water, Soil and Air Hygiene, Berlin, 2:454-548; 1987. Nex¢, E.; Skov, P.; Gravesen, S. Extreme fatigue and malaise a syndrome caused by badly cleaned wall-to-wall carpets. Ecol. Disease. 2:415-418; 1984. Skov, P.; Valbjern, O. The sick building syndrome in the office environment. Proceedings of the 4th International Conference on Indoor Air Quality and Climate, Institute for Water, Soil and Air Hygiene, Berlin 2:439-443; 1987.