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A longitudinal study relating carpeting with sick building syndrome
Environrncnt International, Vol. 15, pp. 129 - 135, 1989 Printed in the U.S.A. All rights reserved.
0160-4120/89 $3.00 +.00 Copyright ©1989 Pergamon Press plc
A LONGITUDINAL STUDY RELATING CARPETING WITH SICK BUILDING SYNDROME Dan NorbSck and Margareta Torg6n Departmentof OccupationalMedicine,UniversityHospital.S-751 85 Uppsala,Sweden E1 87-346 (Received30 October 1987; Accepted 18 January 1989) A longitudinal questionnaire study was performed among personnel in two Swedish primary schools with wall-to-wall carpets and four schools with hard floor covering. The study groups consisted of all primary schools equipped with wall-to-wall carpets in the town of Uppsala, plus a random sample of two newer and two elderly primary schools with hard floor covering. In an initial cross-sectional study, the wall-to-wail carpet group reported an enhanced prevalence of ¢y¢ and airway symptoms, face rashes, headache, abnormal tiredness and a sensation of being electrostatically charged in comparison with personnel in schools with hard floor covering. Since the enhanced prevalence of symptoms in the wall-to-wall carpets versus the hard floor covering group was also observed among persons without signs of atopy it was concluded that wall-to-wall carpets are not exclusively a problem for the sensitive atopic individual. The type of ventilation system (mechanical ventilation versus natural ventilation) had no significant effect on the symptom frequencies. After the removal of the wa11-to-wall carpets, many of the reported symptoms decreased to a level similar to the group without previous or present exposure to such carpets. However, the frequency of airway symptoms remained enhanced among the wall-to-wall carpet group.
INTRODUCTION
of proteins in wall-to-wall carpets as compared to hard floor covering (Anderson et al. 1982; Gravesten et al. 1983; Gravesten et al. 1986; Gravesten 1987). In addition, higher levels of microorganisms in the air above such carpets as compared to hard floor covering has also been demonstrated (Rotter 1974; Anderson et al. 1982; Gravesten et al. 1986; Gravesten 1987). However, in an epidemiological investigation of hospital infections, no association between carpets in hospitals and infections could be demonstrated (Anderson et al. 1982). In some countries, dry shampoos have frequently been used to clean wall-to-wall carpets. These shampoos may cause both allergic contact dermatitis (Taylor and Hindson 1982) and airway irritation (Kreiss, et al. 1982; Anonymous 1983; Schmitt 1985). In dwellings in the USA, both accumulation of house mites
In office environments, hospitals and public institutions, wall-to-wall carpets are sometimes used to create a more intimate atmosphere or to reduce the noise level. However, both health authorities and scientists have focused on possible exposures and health effects of such carpets. Discussion initially concerned carpeting in hospitals and possible accumulation of bacteria in the carpets (Shaffer 1966; Anderson 1969; Rotter, 1974; Rylander et al. 1974; Bethe 1978). As a result of this debate, the Swedish health authorities recommended a limitation of the use of wall-to-wall carpets in public indoor environments (National Swedish Board of Health and Welfare 1979). Since then, several investigations have shown an accumulation of both bacteria, molds and total amount 129
130
in wall-to-wall carpets and exposure to freshly cleaned carpets has been investigated in connection with a search for the etiological cause of Kawasaki syndrome, a pediatric vasculitis (Rogers, et al. 1985; Glode et al. 1986). Besides the chemical and microbiological exposure factors related to carpeting, wall-to-wall carpets are also related to a higher exposure to static electricity than other non-textile floor coverings (Ibsen et al. 1981; G0the et al. 1989). During the last decade, there has been an increasing interest in the indoor environment as a cause of a syndrome of irritative and general symptoms known as the sick building syndrome (SBS). This syndrome involves various symptoms such as eye, skin and upper airway irritation, headache and fatigue (Akimenko et al. 1986). In the Danish Town Hall Study, an association between a large area of fleecy surfaces per cubic meter of air in the work places, and a higher prevalence of the sick building syndrome could be demonstrated (ValbjCrn and Skov 1987). In another Danish report, fatigue was found among 5 of 12 individuals working in a building with poorly cleaned wall-towall carpets. Two positive prick tests and four cases of positive precipitating antibodies was demonstrated against extracts of dust collected from the carpets (Nex¢ et al. 1983). In two other Danish studies of schools pupils in Copenhagen, an increased frequency of allergic symptoms was found among pupils in schools with textiles as floor covering in comparison with pupils in schools with hard floor covering (Ibsen et al. 1981; Hansen et al. 1987). Although several publications have been dealing with possible health problems or exposures related to wall-to-wall carpets, no longitudinal epidemiological studies on the effect of wall- to-wall carpets on the prevalence of the sick building syndrome are found in the literature. In this study, the effect of carpeting on the frequency of such symptoms was first studied in a cross-sectional questionnaire study performed during 1982 among primary school personnel. After the removal of the wall-to-wall carpets from the schools, the study was extended to a longitudinal study by readministering the questionnaire four years after. MATERIAL AND METHODS
Information was gathered during 1982 on the type of floor coating and on the building age of all primary schools (N=14) in a major Swedish city (Uppsala). The survey revealed that two of the 14 schools had wall-to-wall carpets in the classrooms as well as in the corridors. The wall-to-wall carpets in the two
D. Norbick and M. Torg6n
schools were level-looped and as old as the schools (8-10 years). The cleaning routine for the wall-towall carpets comprised vacuum cleaning during the daytime. No dry shampoos or other chemical cleaners were used on the carpets. In the other schools, hard plastic floor coatings wore used in general and wallto-wall carpets were rare. The study group consisted of all personnel in the two schools with wall-to-wall carpets, plus a random sample of two newer and two older primary schools with hard floor coatings. The two older schools wore stone buildings without forced ventilation. The two newer schools and the wall-to-wall carpet schools were one-floor brick buildings equipped with forced mechanical ventilation without air conditioning. All six schools in the study were built before the so-called energy crisis in 1974. In the first phase, a cross-sectional study was performed in 1982 among all personnel (N=205) in the six selected schools. The prevalence of symptoms in the schools was recorded by a self-administered questionnaire. The questionnaire contained questions on symptoms as well as on environmental factors and individual factors such as smoking habits, atopy, sick leave and work satisfaction. Work satisfaction was measured by the use of an analogue rating scale (Bond and Lader 1974). To avoid influencing the longitudinal study, the result of the cross sectional study results were not reported to the participants. To study if the difference in ventilation system type influenced the result, the symptom score was calculated for each individual. Then the average number of symptoms in hard floor covering schools with natural ventilation and forced mechanical ventilation was compared. During the period 1982-86, the wall-to-wall carpets were gradually removed from the schools. During 1986, the questionnaire study was repeated among those in the initial study group still at work in the primary schools in the city (N=141). To detect selection effects that could influence the result of the longitudinal study, the average number of symptoms among those still at work in the primary schools during 1986 was compared with the average number of symptoms among those not at work in these schools during 1986. This comparison was done both in the wall-to-wall carpet group and the hard floor covering group. Comparisons of symptom frequencies in exposed and nonexposed groups were done by fourfold contingency tables and 2-tailed g 2 p-values. Differences in the average symptom score between groups wore tested by using Mann-Whitney ranking test or Wilcoxon
Carpeting related to sick building syndrom
131
matched-pairs signed ranks test, using two-tailed pvalues (Armitage 1980).
number of symptoms between the wall-to-wall carpet group and the hard floor covering group could be demonstrated even if atopic individuals were excluded (p <0.05). No significant difference in the average number of symptoms among employees in hard floor covering schools with forced ventilation and hard floor covering schools with natural ventilation could be demonstrated (p >0.05). In the longitudinal study, 129 out of 141 individuals still at work in the primary schools in the city participated (91%). Four individuals who still worked in rooms with wall-to-wall carpets during 1986 and seven individuals who had moved from work rooms without wall-to-wall carpets during the period from 1982 to 86 to work rooms with such carpets were excluded from the statistical analyses. The longitudinal study revealed that the frequencies of symptoms from the eyes and skin, headache and tiredness among those earlier exposed to wallto-wall carpets decreased. The frequencies were not significantly different from the frequencies among personnel
RESULTS
Certain demographical data for the subpopulations included in the study are presented in Table 1. Selected variables that could differentiate the proportion of sensitive individuals in the various groups are presented in Table 2. In the initial cross-sectional study 192 out of 205 individuals participated in the study (94%). Those 59 persons with wall-to-wall carpets in their workrooms reported a significantly enhanced prevalence of eye irritation, swollen eyelids, rashes in the face, headache and abnormal tiredness in comparison with persons with no such carpets in their workrooms (Table 3). This initial study also showed a correlation between the presence of wall-to-wall carpets in the workroom and the sensation of being eleetrostatieally charged (Table 4). A significant difference in the average
Table I. Selected demographic data for the subpopulstions included in the total material (M=arithmetic mean value, SO=standard deviation).
Type of group
Wall-to-wall carpet 1982 Hard floor covering 1982
Age (M+ SO)
N
Proportion of females
Proportion of smokers
59 133
42+ 11 43+ 11
51/59 (86Z) 103/133 (77Z)
9/59 (15Z) 22/133 (17Z)
37 81
44+ 10 46+ 9
30/37 (81I) 62/81 (77Z)
4/37 ( l l Z ) 11/80 (14I)
Previous wall-to-wall carpet 1986 Permanent hard floor covering 1986
Table 2. Selected variables among the subpopulations included in the total material (M=arithmetic mean value, SO=standard deviation).
Type of group
Wall-to-wall carpet 1982 Hard floor covering 1982 Previous wall-to-wall carpet 1986 Permanent hard floor coverln8 1986
N
3ob satisfaction(Z) (M+ SO)
59 133
78+ 18 71+ 22
7.4+ 10.2 5.2+ 7.8
12/59 (20Z) 22/133 (17Z)
37 81
75+ 18 69+ 24
4.4+ 4.8 8.0+ 20.2
6/37 (16~) 13181 (16Z)
Sick-leave- Proportion (days/year) of atopic (14+ SO) individuals b
• Self-reported sick leave days due to airway illness. b Individuals with a history of asthma, hayfcver, or eczema in childhood.
132
D. Norbick and M. Torg6n
Table 3. Symptom frequencies (1982) among school personnel with wail-to-wall carpets in their workroom, and school personnel with hard floor covering (NS=non-significant, p > 0.05). Wall-to-wall carpet group
Hard floor covering group
Type of symptom
Cases/total number (Z)
Cases/total number (Z)
Eye Irrltatlo~ Swollen eyelids
18/59 (31~) 10159 (17~)
18/133 (14Z) 0.006 4/133 ( 3 Z ) <0.001
Nasal catarrh Blocked-up nose
6/58 (10Z) 13/58 (22Z)
17/132 (13Z) 25]132 (19Z)
Dryness in the t h r o a t Sore throat Irritative cough
29/58 (50Z) 16[59 (27Z) 14]58 (24Z)
24/132 (18~) <0.001 12/133 ( g Z ) <0.001 10[133 ( 8 Z ) 0.001
p"
NS 78
Headache 22/59 (371) Abnormal tiredness 32/59 (541) Sensation of getting a cold 27[58 (47Z) Nausea 2[59 (3Z)
26/132 (201) 41[131 (34Z) 29/133 (22Z) 7]133 (SZ)
0.009 0.003 <0.001 NS
Facial itching Facial rash Itching on the hands Rashes on the hands Eczema
5[133 (41) 5[133 ( 4 1 ) 121133 (gz) 61133 (5Z) 20[131 (15Z)
NS 0.03 NS NS NS
5[59 ( 8 I ) 7/59 (12I) 7[58 (12~) 5/59 (gz) 8]59 (14Z)
• Two-tailed p-value calculated by Z2-test. Table 4. Reported exposure to static electricity among the subpopulations included in the total material.
Type of group
N
Wall-to-wall carpet 1982 Hard floor covering 1982 Previous wall-to-wall carpet 1986 Permanent hard floor covering 1986
ProportLon of personnel reporting exposure to static electricity"
59 133
23[59 151132
(39Z) b (111)
37 81
6/37 3181
(16I) = (4I)
• Often experiencing static elecricity at contact with metal devices, such as radiators or water taps. b Significant deviation from hard floor covering group 1982 (p < O.OOl). Significant deviation from permanent hard floor covering group 1986 (p < 0.05 ).
without previous or present exposure to wall-to-wall carpets. However, the frequency of airway symptoms remained high among the wall-to-wall carpet group, even years after the removal of the carpets (Table 5).
A further analysis of the material demonstrated a nonhealthy worker selection effect in the wall-towall carpet group, Table 6. Employees with earlier work in wall-to-wall carpeted work premises who
Carpeting related to sick building syndrom
133
Table 5. Symptom frequencies (1986) among school personnel previously exposed to wall-to-wail carpets in their workroom and school personnel with hard floor covering in their workrooms (NSfnon-significant, p >0.05).
Type of symptom
Prevlously Wall-to-wall Carpet group
Permanent Hard floor covering group
Cases/total number (Z)
Cases/total number (Z)
Eye i r r i t a t i o n Swollen e y e l i d s
7137 (19Z) 4137 ( 1 1 I )
Nasal catarrh Blocked-up nose
p"
11181 (14Z) 7181 (gz)
NS NS
3137 (8Z) 6137 (16g)
5180 (6Z) 9181 (11Z)
NS NS
13137 (35I) 7137 (19Z) 9/37 (24Z)
13181 (16Z) 3180 ( 4 Z ) 6180 ( 8 Z )
0.02 0.007 0.01
Headache 11137 (30Z) Abnormal tiredness 15137 (41Z) Sensation of getting a cold 14137 (38Z) Nausea 3/37 (8Z)
14/80 (18g) 29180 (36Z) 14180 (181) 5180 (6Z)
NS NS 0.02 NS
Dryness in the throat Sore throat Irrltative cough
Facial itching F a c i a l rash Itching on the hands Rashes on the hands Eczema
2137 3137
(SZ) (8Z)
4180 4/81
(5I) (5Z)
5137 (14Z)
5181
(6Z)
5137 (lhZ) 5137 (16Z)
5181 (6Z) 16/81 (20Z)
NS NS NS NS NS
• Two-tailed p-value calculated by z-square test.
Table 6. Symptom score (0 to 16 symptoms) among certain subgroups in the total material (ML=arithmetic mean value, SD=standard deviation).
Type of group
N
Symptom score 1982 (M+ SD)
Symptom score 1985 (M+ SD)
Wall-to-wall carpet group at work 1986 Wall-to-wall carpet group not at work 1985
37 22
4.4+ 2.8 2.5+ 2.8"
2.9+ 2.4 b
Hard floor covering group at work 1986 Hard floor covering group not at work 1986
81 52
1.8+ 2.4 2.2+ 2.0
1.7+ 2.3
• Significant deviation from wall-to-wall group at work 1986 (p=O.O07, Mann-Whitney ranking test). b Significant deviation from wall-to-wall carpet group 1982 (pffiO.O02, Wilcoxon matched pairs signed ranks-test).
134
were still at work in Uppsala's primary schools during 1986 had an average number of symptoms in the 1982 study greater than those employees with earlier work in wall-to-wall carpet schools who were not at work in primary schools during 1986 (p <0.05). The same comparison was made among those employees who had worked in work sites with hard floor covering during 1982, but no selection effect could be demonstrated in the hard floor covering group (p > 0.05). DISCUSSION AND CONCLUSION
In this study, wall-to-wall carpets were found to be related to an enhanced frequency of certain symptoms (eye, airway and skin irritation, headache and fatigue). These symptoms are of the same type as those symptoms described as the sick building syndrome (Akimenko et al. 1986). Although no other epidemiological studies on the particular effect of carpeting on the sick building syndrome are found in the literature, an association between wall-to-wall carpets and skin symptoms on the face has earlier been demonstrated in patient material of office workers with medical symptoms suspected to be related to paper handling, mainly carbonless copying paper (Norb/lck et al. 1983). Abnormal tiredness related to a badly cleaned wall-towall carpet has earlier been described in a Danish report (Nex¢ et al. 1983). Although the Danish Town Hall study (Valbjcrn and Skov 1987) did not differentiate between fleecy material on the floor and fleecy material on the walls, the result from this study is in agreement with our investigation result. It was not within the scope of this questionnaire study to identify factors causing the enhanced prevalence of symptoms among the wall-to-wall carpet group. However, available background information leads us to conclude that certain exposure factors are less probable causes of the symptoms reported. Since the carpets were relatively old (8 to 10 years) and no dry shampoo or other chemical cleaners were used on the carpets, chemical emission from cleaners or from the carpet itself is a less probable cause of the symptoms. As appears from the literature, house dust mites are found in dwellings in damp areas, and not in indoor work environments in dry areas. In the city of Uppsala, the relative indoor air humidity regularly stays below an absolute humidity of 4 g/kg (20% relative humidity at 22°C) for several months during the winter. According to a Danish study, house dust mites need an absolute humidity above 7 g/kg to survive (Korsgaard 1983). Therefore, allergy to house dust mites can also be considered as an improbable cause of the symptoms in this particular study.
D. Norbick and M. Torg6n
Since the carpets were old and in schools, they most probably accumulated both indoor dust and outdoor dirt from the childrens' shoes. Dust in old carpets could contain both organic and inorganic compounds, heavy metals, proteins and various types of dead or live microorganisms. Although dust or dirt accumulated in the carpets is a probable factor related to the symptoms in this study, it was not possible to specify the causative factor(s) in the carpet dust. In this study, an association was shown between textile floor coverings and the inconvenience of being electrostatically charged. An association between wall-to-wall carpets and exposure to static electricity has been described earlier in the literature (Ibsen et al. 1981; GOthe et al. 1989). Concerning the possible relation between static electricity and the sick building syndrome, there is conflicting information in the literature. At video display terminal work, where electrostatic fields also may be generated, both enhanced dust accumulation (Olsen 1981) and dermatological symptoms on the face have been observed (Linden and Rolfsen 1981; Liden and Wahlberg 1985). In two recent Swedish studies, individuals who often experienced electrostatic shocks in indoor environments without carpeting reported an enhanced prevalence of fatigue (Michel et al. 1989) as well as an enhanced prevalence of sick building syndrome (Norbltck et al. 1987). In a British study, no such association could be demonstrated (Burge et al. 1987). In two other studies in which the degree of electrostatic charge was measured among office workers, one study revealed a significant association between the degree of charge and the prevalence of symptoms associated with the sick building syndrome (Valbjcrn and Skov 1987). In the other study, no such association could be demonstrated (G6the et al. 1989). Regardless of the causative factors, wall-to-wall carpets in work places can induce symptoms of the sick building syndrome type, and the removal of such carpets from work environments seems to have a positive effect on some but not all of the symptoms. The decrease of many symptoms after the removal of the carpets demonstrated in this study could not be explained by selection effects (the healthy worker effect). On the contrary, some of the persistent enhanced prevalence of some of the symptoms in the wall-to-wall carpet group as compared to the hard floor covering group could be explained by selection (a nonhealthy worker effect).
Carpeting related to sick building syndrom
REFERENCES Akimenko, V.V.; Andersen, I.; Lebowitz, M.D.; Lindvall, T. The "sick" building syndrome. In: Berglund, B.; Berglund, U.; Lindvall, T.; Sundell, J., eds. Indoor air, evaluations and conclusions for health sciences and technology. Stockholm: Swedish Council for Building Research; D13: 1986:p. 87-97. 6 vol. Anderson, R.L. Biological evaluation of carpeting. Appl. Microbiol. 18:180-187; 1969. Anderson, R.L.; Mackel, D.C.; Stoler, B.S.; Mallison, G.F. Carpeting in hospitals: an epidemiological evaluation. J. Clin. Microbiol. 15:408-415; 1982. Anonymous. Respiratory illness associated with carpet cleaning at a hospital clinic - Virginia. Morbidity and Mortality Weekly Report 32:378, 383-384; 1983. Armitage, P. Statistical methods in medical research. Oxford: Blackwell Scientific Publications; 1980. Bond, A.; Lader, M. The use of analogue rating scales in rating subjective feelings. Brit. J. Med. Psychol. 47:211-218; 1974. Bethe, M. Teppichbtden in 6ffentlichen Gebauden --ja oder nein7 (Wall-to-wall carpets in public buildings - - yes or noT). Das ~)ffentliche Gesundheitswesen 40:679-688; 1978. Burge, S.; Hedge, A.; Wilson, S.; Bass, J.H.; Robertson, A. Sick building syndrome: A study of 4373 office workers. Ann. Occup. Hyg. 31:493-504; 1987. Glode, M.; Brogden, R.; Joffe, L.S.; Adinoff, A.; Leung, D.Y.M.; Burns, J.C.; Arlian, L.G. Kawasaki syndrome and house dust mite exposure. Pediatr. Infect. Dis. 5:644-648; 1986. Gravesten, S. Microbiological studies on carpets versus hard floors in non-industrial occupations. In: Seifert, B.; Esdorn, H.; Fischer, M.; Riiden, H.; Wegner, J., eds. Indoor air'87. Vol 1: Volatile organic compounds, combustion gases, particles and fibers, microbiological agents. Berlin: Institute for Water, Soil, and Air Hygiene; 1987:p. 668-672. Gravesten, S.; Larsen, L.; Gyntelberg, F.; Skov, P. Demonstration of microorganisms and dust in schools and offices - - an observational study of non-industrialbuildings. Allergy 41:520-525; 1986. Gravesten, S.; Larsen, L.; Skov, P. Aerobiology of schools and public institutions - - p a r t of a study. Ecol. Dis. 2:411-413; 1983. G6the, C.J.; Ancker, K.; Bjurstr6m, R.; Holm, S.; Langworth, S. Electric potential differences against the surroundings and discomforts in indoor environments. Ann. Occup. Hyg. (in press). Hansen, L.; Bach, E.; Ibsen, E.K.; Karsten, ~)sterballe, O. Carpeting in schools as an indoor pollutant. In: Seifert, B.; Esdoru, H.; Fischer, M.; RQden, H.; Wegner, J., eds. Indoor air'87. Vol. 2: Environmental tobacco smoke, multicomponent studies, radon, sick buildings, odours and irritants, hyperreactivities and allergies. Berlin: Institute for Water, Soil, and Air Hygiene; 1987:p. 727-731. Ibsen, K.K.; Valbjcru, O.; Nielsen, A. The indoor environmentand symptoms of disease. Assessment of the conditions in schools in Copenhagen. Ugeskr Laeger 143:1919-1923; 1981. (in Danish with abstract in English) Korsgaard, J. House-dust mites and absolute indoor humidity. Allergy 38:85-92; 1983.
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Kreiss, K.; Gonzales, M.G.; Conright, K.L.; Scheere, A.R. Respiratory irritation due to carpet shampoo: two outbreaks. Environ. Int. 8:337-341; 1982. Liden, C.; Wahlberg, J.E. Does visual display terminal work provoke rosacea? Contact Dermatitis 13:235-241; 1985. Linden, V.; Rolfsen, S. Video computer terminals and occupational dermatitis. Scand. J. Work. Environ. Health 7:62-67; 1981. Michel, I.; Norbick, D.; Edling, C. An epidemiologic study of the relation between symptoms of fatigue, dental amalgam and other factors. Swedish Dent. J 13:33-38; 1989. Nexo, E.; Skov, P.G.; Gravesen, S. Extreme fatigue and malaisea syndrome caused by badly cleaned wall-to-wall carpets? Ecol. Dis. 2:415-418; 1983. Norbick, D.; Michel, I. Vilka faktorer kan ftrklara upplevelsen av besvir i "sjuka hus"? (Which factors can explain the experience of discomforts in "sick buildings"?) Hygiea 96:140; 1987. (in Swedish). Norback, D.; Wieslander, G.; Gtthe, C.J. Carbonless copy paper and discomforts at office work. Arbete och Hilsa 37:6-24; 1983. (in Swedish with abstract in English). The Swedish National Board of Health and Welfare. Socialstyrelsens rekommendatinnom begrinsningav anvindningenav heltickande textilmattor i vissa lokaler (The recommendation by the Swedish National Board of Health and Welfare on the limitation of the use of wall-to-wall textile carpets in certain premises). Stockholm: Socialstyrelsens ftffattningssamling SOSFS (M) 91:1979. (in Swedish). Olsen, W.C. Electric field enhanced aerosol exposure in visual display unit environments. Chr. Michelsen Institute, CMI No 803604-1; 1981. Rogers, M.F.; Kochel, R.L.; Hurwitz, E. S.; Jillon, C. A.; Hanrahan, J.P.; Schonberger, L.B. Kawasaki syndrome: Is exposure to rug shampoo important? Am. J. Dis. Child 139:777-779; 1985. Rotter, M. (1974) Untersuchungenfiberdie Beeinflussungdes Luftkeimgehaltes dutch Teppichbtden (The effect of carpeting on the amount of airborne bacteria). Sozial und Priiventivmedizin 19:321328; 1974. Rylander, R.; Myrbick, K.E.; Verner-Carlson, B.; ~)hrstr6m, M. Bacteriological investigation of wall-to-waU carpeting. Am. J. Public Health 64:163-168; 1974 Schmitt, H.J. Reizungender Atemwegenach Anwendungyon Teppichshampoo (Irritation of the airways following the use of a carpet shampoo). Off. Gesundheitswes. 47:458; 1985. Shaffer, J.G. Microbiology of hospital carpeting. Health Laboratory Science 3:73-85; 1966. Taylor, A.E.M.; Hindson, C. Facial dermatitis from allyl phenoxyacetate in a dry carpet shampoo. Contact Dermatitis 8:70; 1982. Valbjorn, O.; Skov, P. Influence of indoor climate on the sick building syndrome prevalence. In: Seifert, B.; Esdorn, H.; Fischer, M.; Rfiden, H.; Wegner, J., eds. Indoor air'87, vol 2: environmental tobacco smoke, multicomponent studies, radon, sick buildings, odours and irritants, hyperreactivities and allergies. Berlin: Institute for Water, Soil, and Air Hygiene; 1987:p. 593 -597.
0160-4120/89 $3.00 +.00 Copyright ©1989 Pergamon Press plc
A LONGITUDINAL STUDY RELATING CARPETING WITH SICK BUILDING SYNDROME Dan NorbSck and Margareta Torg6n Departmentof OccupationalMedicine,UniversityHospital.S-751 85 Uppsala,Sweden E1 87-346 (Received30 October 1987; Accepted 18 January 1989) A longitudinal questionnaire study was performed among personnel in two Swedish primary schools with wall-to-wall carpets and four schools with hard floor covering. The study groups consisted of all primary schools equipped with wall-to-wall carpets in the town of Uppsala, plus a random sample of two newer and two elderly primary schools with hard floor covering. In an initial cross-sectional study, the wall-to-wail carpet group reported an enhanced prevalence of ¢y¢ and airway symptoms, face rashes, headache, abnormal tiredness and a sensation of being electrostatically charged in comparison with personnel in schools with hard floor covering. Since the enhanced prevalence of symptoms in the wall-to-wall carpets versus the hard floor covering group was also observed among persons without signs of atopy it was concluded that wall-to-wall carpets are not exclusively a problem for the sensitive atopic individual. The type of ventilation system (mechanical ventilation versus natural ventilation) had no significant effect on the symptom frequencies. After the removal of the wa11-to-wall carpets, many of the reported symptoms decreased to a level similar to the group without previous or present exposure to such carpets. However, the frequency of airway symptoms remained enhanced among the wall-to-wall carpet group.
INTRODUCTION
of proteins in wall-to-wall carpets as compared to hard floor covering (Anderson et al. 1982; Gravesten et al. 1983; Gravesten et al. 1986; Gravesten 1987). In addition, higher levels of microorganisms in the air above such carpets as compared to hard floor covering has also been demonstrated (Rotter 1974; Anderson et al. 1982; Gravesten et al. 1986; Gravesten 1987). However, in an epidemiological investigation of hospital infections, no association between carpets in hospitals and infections could be demonstrated (Anderson et al. 1982). In some countries, dry shampoos have frequently been used to clean wall-to-wall carpets. These shampoos may cause both allergic contact dermatitis (Taylor and Hindson 1982) and airway irritation (Kreiss, et al. 1982; Anonymous 1983; Schmitt 1985). In dwellings in the USA, both accumulation of house mites
In office environments, hospitals and public institutions, wall-to-wall carpets are sometimes used to create a more intimate atmosphere or to reduce the noise level. However, both health authorities and scientists have focused on possible exposures and health effects of such carpets. Discussion initially concerned carpeting in hospitals and possible accumulation of bacteria in the carpets (Shaffer 1966; Anderson 1969; Rotter, 1974; Rylander et al. 1974; Bethe 1978). As a result of this debate, the Swedish health authorities recommended a limitation of the use of wall-to-wall carpets in public indoor environments (National Swedish Board of Health and Welfare 1979). Since then, several investigations have shown an accumulation of both bacteria, molds and total amount 129
130
in wall-to-wall carpets and exposure to freshly cleaned carpets has been investigated in connection with a search for the etiological cause of Kawasaki syndrome, a pediatric vasculitis (Rogers, et al. 1985; Glode et al. 1986). Besides the chemical and microbiological exposure factors related to carpeting, wall-to-wall carpets are also related to a higher exposure to static electricity than other non-textile floor coverings (Ibsen et al. 1981; G0the et al. 1989). During the last decade, there has been an increasing interest in the indoor environment as a cause of a syndrome of irritative and general symptoms known as the sick building syndrome (SBS). This syndrome involves various symptoms such as eye, skin and upper airway irritation, headache and fatigue (Akimenko et al. 1986). In the Danish Town Hall Study, an association between a large area of fleecy surfaces per cubic meter of air in the work places, and a higher prevalence of the sick building syndrome could be demonstrated (ValbjCrn and Skov 1987). In another Danish report, fatigue was found among 5 of 12 individuals working in a building with poorly cleaned wall-towall carpets. Two positive prick tests and four cases of positive precipitating antibodies was demonstrated against extracts of dust collected from the carpets (Nex¢ et al. 1983). In two other Danish studies of schools pupils in Copenhagen, an increased frequency of allergic symptoms was found among pupils in schools with textiles as floor covering in comparison with pupils in schools with hard floor covering (Ibsen et al. 1981; Hansen et al. 1987). Although several publications have been dealing with possible health problems or exposures related to wall-to-wall carpets, no longitudinal epidemiological studies on the effect of wall- to-wall carpets on the prevalence of the sick building syndrome are found in the literature. In this study, the effect of carpeting on the frequency of such symptoms was first studied in a cross-sectional questionnaire study performed during 1982 among primary school personnel. After the removal of the wall-to-wall carpets from the schools, the study was extended to a longitudinal study by readministering the questionnaire four years after. MATERIAL AND METHODS
Information was gathered during 1982 on the type of floor coating and on the building age of all primary schools (N=14) in a major Swedish city (Uppsala). The survey revealed that two of the 14 schools had wall-to-wall carpets in the classrooms as well as in the corridors. The wall-to-wall carpets in the two
D. Norbick and M. Torg6n
schools were level-looped and as old as the schools (8-10 years). The cleaning routine for the wall-towall carpets comprised vacuum cleaning during the daytime. No dry shampoos or other chemical cleaners were used on the carpets. In the other schools, hard plastic floor coatings wore used in general and wallto-wall carpets were rare. The study group consisted of all personnel in the two schools with wall-to-wall carpets, plus a random sample of two newer and two older primary schools with hard floor coatings. The two older schools wore stone buildings without forced ventilation. The two newer schools and the wall-to-wall carpet schools were one-floor brick buildings equipped with forced mechanical ventilation without air conditioning. All six schools in the study were built before the so-called energy crisis in 1974. In the first phase, a cross-sectional study was performed in 1982 among all personnel (N=205) in the six selected schools. The prevalence of symptoms in the schools was recorded by a self-administered questionnaire. The questionnaire contained questions on symptoms as well as on environmental factors and individual factors such as smoking habits, atopy, sick leave and work satisfaction. Work satisfaction was measured by the use of an analogue rating scale (Bond and Lader 1974). To avoid influencing the longitudinal study, the result of the cross sectional study results were not reported to the participants. To study if the difference in ventilation system type influenced the result, the symptom score was calculated for each individual. Then the average number of symptoms in hard floor covering schools with natural ventilation and forced mechanical ventilation was compared. During the period 1982-86, the wall-to-wall carpets were gradually removed from the schools. During 1986, the questionnaire study was repeated among those in the initial study group still at work in the primary schools in the city (N=141). To detect selection effects that could influence the result of the longitudinal study, the average number of symptoms among those still at work in the primary schools during 1986 was compared with the average number of symptoms among those not at work in these schools during 1986. This comparison was done both in the wall-to-wall carpet group and the hard floor covering group. Comparisons of symptom frequencies in exposed and nonexposed groups were done by fourfold contingency tables and 2-tailed g 2 p-values. Differences in the average symptom score between groups wore tested by using Mann-Whitney ranking test or Wilcoxon
Carpeting related to sick building syndrom
131
matched-pairs signed ranks test, using two-tailed pvalues (Armitage 1980).
number of symptoms between the wall-to-wall carpet group and the hard floor covering group could be demonstrated even if atopic individuals were excluded (p <0.05). No significant difference in the average number of symptoms among employees in hard floor covering schools with forced ventilation and hard floor covering schools with natural ventilation could be demonstrated (p >0.05). In the longitudinal study, 129 out of 141 individuals still at work in the primary schools in the city participated (91%). Four individuals who still worked in rooms with wall-to-wall carpets during 1986 and seven individuals who had moved from work rooms without wall-to-wall carpets during the period from 1982 to 86 to work rooms with such carpets were excluded from the statistical analyses. The longitudinal study revealed that the frequencies of symptoms from the eyes and skin, headache and tiredness among those earlier exposed to wallto-wall carpets decreased. The frequencies were not significantly different from the frequencies among personnel
RESULTS
Certain demographical data for the subpopulations included in the study are presented in Table 1. Selected variables that could differentiate the proportion of sensitive individuals in the various groups are presented in Table 2. In the initial cross-sectional study 192 out of 205 individuals participated in the study (94%). Those 59 persons with wall-to-wall carpets in their workrooms reported a significantly enhanced prevalence of eye irritation, swollen eyelids, rashes in the face, headache and abnormal tiredness in comparison with persons with no such carpets in their workrooms (Table 3). This initial study also showed a correlation between the presence of wall-to-wall carpets in the workroom and the sensation of being eleetrostatieally charged (Table 4). A significant difference in the average
Table I. Selected demographic data for the subpopulstions included in the total material (M=arithmetic mean value, SO=standard deviation).
Type of group
Wall-to-wall carpet 1982 Hard floor covering 1982
Age (M+ SO)
N
Proportion of females
Proportion of smokers
59 133
42+ 11 43+ 11
51/59 (86Z) 103/133 (77Z)
9/59 (15Z) 22/133 (17Z)
37 81
44+ 10 46+ 9
30/37 (81I) 62/81 (77Z)
4/37 ( l l Z ) 11/80 (14I)
Previous wall-to-wall carpet 1986 Permanent hard floor covering 1986
Table 2. Selected variables among the subpopulations included in the total material (M=arithmetic mean value, SO=standard deviation).
Type of group
Wall-to-wall carpet 1982 Hard floor covering 1982 Previous wall-to-wall carpet 1986 Permanent hard floor coverln8 1986
N
3ob satisfaction(Z) (M+ SO)
59 133
78+ 18 71+ 22
7.4+ 10.2 5.2+ 7.8
12/59 (20Z) 22/133 (17Z)
37 81
75+ 18 69+ 24
4.4+ 4.8 8.0+ 20.2
6/37 (16~) 13181 (16Z)
Sick-leave- Proportion (days/year) of atopic (14+ SO) individuals b
• Self-reported sick leave days due to airway illness. b Individuals with a history of asthma, hayfcver, or eczema in childhood.
132
D. Norbick and M. Torg6n
Table 3. Symptom frequencies (1982) among school personnel with wail-to-wall carpets in their workroom, and school personnel with hard floor covering (NS=non-significant, p > 0.05). Wall-to-wall carpet group
Hard floor covering group
Type of symptom
Cases/total number (Z)
Cases/total number (Z)
Eye Irrltatlo~ Swollen eyelids
18/59 (31~) 10159 (17~)
18/133 (14Z) 0.006 4/133 ( 3 Z ) <0.001
Nasal catarrh Blocked-up nose
6/58 (10Z) 13/58 (22Z)
17/132 (13Z) 25]132 (19Z)
Dryness in the t h r o a t Sore throat Irritative cough
29/58 (50Z) 16[59 (27Z) 14]58 (24Z)
24/132 (18~) <0.001 12/133 ( g Z ) <0.001 10[133 ( 8 Z ) 0.001
p"
NS 78
Headache 22/59 (371) Abnormal tiredness 32/59 (541) Sensation of getting a cold 27[58 (47Z) Nausea 2[59 (3Z)
26/132 (201) 41[131 (34Z) 29/133 (22Z) 7]133 (SZ)
0.009 0.003 <0.001 NS
Facial itching Facial rash Itching on the hands Rashes on the hands Eczema
5[133 (41) 5[133 ( 4 1 ) 121133 (gz) 61133 (5Z) 20[131 (15Z)
NS 0.03 NS NS NS
5[59 ( 8 I ) 7/59 (12I) 7[58 (12~) 5/59 (gz) 8]59 (14Z)
• Two-tailed p-value calculated by Z2-test. Table 4. Reported exposure to static electricity among the subpopulations included in the total material.
Type of group
N
Wall-to-wall carpet 1982 Hard floor covering 1982 Previous wall-to-wall carpet 1986 Permanent hard floor covering 1986
ProportLon of personnel reporting exposure to static electricity"
59 133
23[59 151132
(39Z) b (111)
37 81
6/37 3181
(16I) = (4I)
• Often experiencing static elecricity at contact with metal devices, such as radiators or water taps. b Significant deviation from hard floor covering group 1982 (p < O.OOl). Significant deviation from permanent hard floor covering group 1986 (p < 0.05 ).
without previous or present exposure to wall-to-wall carpets. However, the frequency of airway symptoms remained high among the wall-to-wall carpet group, even years after the removal of the carpets (Table 5).
A further analysis of the material demonstrated a nonhealthy worker selection effect in the wall-towall carpet group, Table 6. Employees with earlier work in wall-to-wall carpeted work premises who
Carpeting related to sick building syndrom
133
Table 5. Symptom frequencies (1986) among school personnel previously exposed to wall-to-wail carpets in their workroom and school personnel with hard floor covering in their workrooms (NSfnon-significant, p >0.05).
Type of symptom
Prevlously Wall-to-wall Carpet group
Permanent Hard floor covering group
Cases/total number (Z)
Cases/total number (Z)
Eye i r r i t a t i o n Swollen e y e l i d s
7137 (19Z) 4137 ( 1 1 I )
Nasal catarrh Blocked-up nose
p"
11181 (14Z) 7181 (gz)
NS NS
3137 (8Z) 6137 (16g)
5180 (6Z) 9181 (11Z)
NS NS
13137 (35I) 7137 (19Z) 9/37 (24Z)
13181 (16Z) 3180 ( 4 Z ) 6180 ( 8 Z )
0.02 0.007 0.01
Headache 11137 (30Z) Abnormal tiredness 15137 (41Z) Sensation of getting a cold 14137 (38Z) Nausea 3/37 (8Z)
14/80 (18g) 29180 (36Z) 14180 (181) 5180 (6Z)
NS NS 0.02 NS
Dryness in the throat Sore throat Irrltative cough
Facial itching F a c i a l rash Itching on the hands Rashes on the hands Eczema
2137 3137
(SZ) (8Z)
4180 4/81
(5I) (5Z)
5137 (14Z)
5181
(6Z)
5137 (lhZ) 5137 (16Z)
5181 (6Z) 16/81 (20Z)
NS NS NS NS NS
• Two-tailed p-value calculated by z-square test.
Table 6. Symptom score (0 to 16 symptoms) among certain subgroups in the total material (ML=arithmetic mean value, SD=standard deviation).
Type of group
N
Symptom score 1982 (M+ SD)
Symptom score 1985 (M+ SD)
Wall-to-wall carpet group at work 1986 Wall-to-wall carpet group not at work 1985
37 22
4.4+ 2.8 2.5+ 2.8"
2.9+ 2.4 b
Hard floor covering group at work 1986 Hard floor covering group not at work 1986
81 52
1.8+ 2.4 2.2+ 2.0
1.7+ 2.3
• Significant deviation from wall-to-wall group at work 1986 (p=O.O07, Mann-Whitney ranking test). b Significant deviation from wall-to-wall carpet group 1982 (pffiO.O02, Wilcoxon matched pairs signed ranks-test).
134
were still at work in Uppsala's primary schools during 1986 had an average number of symptoms in the 1982 study greater than those employees with earlier work in wall-to-wall carpet schools who were not at work in primary schools during 1986 (p <0.05). The same comparison was made among those employees who had worked in work sites with hard floor covering during 1982, but no selection effect could be demonstrated in the hard floor covering group (p > 0.05). DISCUSSION AND CONCLUSION
In this study, wall-to-wall carpets were found to be related to an enhanced frequency of certain symptoms (eye, airway and skin irritation, headache and fatigue). These symptoms are of the same type as those symptoms described as the sick building syndrome (Akimenko et al. 1986). Although no other epidemiological studies on the particular effect of carpeting on the sick building syndrome are found in the literature, an association between wall-to-wall carpets and skin symptoms on the face has earlier been demonstrated in patient material of office workers with medical symptoms suspected to be related to paper handling, mainly carbonless copying paper (Norb/lck et al. 1983). Abnormal tiredness related to a badly cleaned wall-towall carpet has earlier been described in a Danish report (Nex¢ et al. 1983). Although the Danish Town Hall study (Valbjcrn and Skov 1987) did not differentiate between fleecy material on the floor and fleecy material on the walls, the result from this study is in agreement with our investigation result. It was not within the scope of this questionnaire study to identify factors causing the enhanced prevalence of symptoms among the wall-to-wall carpet group. However, available background information leads us to conclude that certain exposure factors are less probable causes of the symptoms reported. Since the carpets were relatively old (8 to 10 years) and no dry shampoo or other chemical cleaners were used on the carpets, chemical emission from cleaners or from the carpet itself is a less probable cause of the symptoms. As appears from the literature, house dust mites are found in dwellings in damp areas, and not in indoor work environments in dry areas. In the city of Uppsala, the relative indoor air humidity regularly stays below an absolute humidity of 4 g/kg (20% relative humidity at 22°C) for several months during the winter. According to a Danish study, house dust mites need an absolute humidity above 7 g/kg to survive (Korsgaard 1983). Therefore, allergy to house dust mites can also be considered as an improbable cause of the symptoms in this particular study.
D. Norbick and M. Torg6n
Since the carpets were old and in schools, they most probably accumulated both indoor dust and outdoor dirt from the childrens' shoes. Dust in old carpets could contain both organic and inorganic compounds, heavy metals, proteins and various types of dead or live microorganisms. Although dust or dirt accumulated in the carpets is a probable factor related to the symptoms in this study, it was not possible to specify the causative factor(s) in the carpet dust. In this study, an association was shown between textile floor coverings and the inconvenience of being electrostatically charged. An association between wall-to-wall carpets and exposure to static electricity has been described earlier in the literature (Ibsen et al. 1981; GOthe et al. 1989). Concerning the possible relation between static electricity and the sick building syndrome, there is conflicting information in the literature. At video display terminal work, where electrostatic fields also may be generated, both enhanced dust accumulation (Olsen 1981) and dermatological symptoms on the face have been observed (Linden and Rolfsen 1981; Liden and Wahlberg 1985). In two recent Swedish studies, individuals who often experienced electrostatic shocks in indoor environments without carpeting reported an enhanced prevalence of fatigue (Michel et al. 1989) as well as an enhanced prevalence of sick building syndrome (Norbltck et al. 1987). In a British study, no such association could be demonstrated (Burge et al. 1987). In two other studies in which the degree of electrostatic charge was measured among office workers, one study revealed a significant association between the degree of charge and the prevalence of symptoms associated with the sick building syndrome (Valbjcrn and Skov 1987). In the other study, no such association could be demonstrated (G6the et al. 1989). Regardless of the causative factors, wall-to-wall carpets in work places can induce symptoms of the sick building syndrome type, and the removal of such carpets from work environments seems to have a positive effect on some but not all of the symptoms. The decrease of many symptoms after the removal of the carpets demonstrated in this study could not be explained by selection effects (the healthy worker effect). On the contrary, some of the persistent enhanced prevalence of some of the symptoms in the wall-to-wall carpet group as compared to the hard floor covering group could be explained by selection (a nonhealthy worker effect).
Carpeting related to sick building syndrom
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Kreiss, K.; Gonzales, M.G.; Conright, K.L.; Scheere, A.R. Respiratory irritation due to carpet shampoo: two outbreaks. Environ. Int. 8:337-341; 1982. Liden, C.; Wahlberg, J.E. Does visual display terminal work provoke rosacea? Contact Dermatitis 13:235-241; 1985. Linden, V.; Rolfsen, S. Video computer terminals and occupational dermatitis. Scand. J. Work. Environ. Health 7:62-67; 1981. Michel, I.; Norbick, D.; Edling, C. An epidemiologic study of the relation between symptoms of fatigue, dental amalgam and other factors. Swedish Dent. J 13:33-38; 1989. Nexo, E.; Skov, P.G.; Gravesen, S. Extreme fatigue and malaisea syndrome caused by badly cleaned wall-to-wall carpets? Ecol. Dis. 2:415-418; 1983. Norbick, D.; Michel, I. Vilka faktorer kan ftrklara upplevelsen av besvir i "sjuka hus"? (Which factors can explain the experience of discomforts in "sick buildings"?) Hygiea 96:140; 1987. (in Swedish). Norback, D.; Wieslander, G.; Gtthe, C.J. Carbonless copy paper and discomforts at office work. Arbete och Hilsa 37:6-24; 1983. (in Swedish with abstract in English). The Swedish National Board of Health and Welfare. Socialstyrelsens rekommendatinnom begrinsningav anvindningenav heltickande textilmattor i vissa lokaler (The recommendation by the Swedish National Board of Health and Welfare on the limitation of the use of wall-to-wall textile carpets in certain premises). Stockholm: Socialstyrelsens ftffattningssamling SOSFS (M) 91:1979. (in Swedish). Olsen, W.C. Electric field enhanced aerosol exposure in visual display unit environments. Chr. Michelsen Institute, CMI No 803604-1; 1981. Rogers, M.F.; Kochel, R.L.; Hurwitz, E. S.; Jillon, C. A.; Hanrahan, J.P.; Schonberger, L.B. Kawasaki syndrome: Is exposure to rug shampoo important? Am. J. Dis. Child 139:777-779; 1985. Rotter, M. (1974) Untersuchungenfiberdie Beeinflussungdes Luftkeimgehaltes dutch Teppichbtden (The effect of carpeting on the amount of airborne bacteria). Sozial und Priiventivmedizin 19:321328; 1974. Rylander, R.; Myrbick, K.E.; Verner-Carlson, B.; ~)hrstr6m, M. Bacteriological investigation of wall-to-waU carpeting. Am. J. Public Health 64:163-168; 1974 Schmitt, H.J. Reizungender Atemwegenach Anwendungyon Teppichshampoo (Irritation of the airways following the use of a carpet shampoo). Off. Gesundheitswes. 47:458; 1985. Shaffer, J.G. Microbiology of hospital carpeting. Health Laboratory Science 3:73-85; 1966. Taylor, A.E.M.; Hindson, C. Facial dermatitis from allyl phenoxyacetate in a dry carpet shampoo. Contact Dermatitis 8:70; 1982. Valbjorn, O.; Skov, P. Influence of indoor climate on the sick building syndrome prevalence. In: Seifert, B.; Esdorn, H.; Fischer, M.; Rfiden, H.; Wegner, J., eds. Indoor air'87, vol 2: environmental tobacco smoke, multicomponent studies, radon, sick buildings, odours and irritants, hyperreactivities and allergies. Berlin: Institute for Water, Soil, and Air Hygiene; 1987:p. 593 -597.