Sick building syndrome in relation to domestic exposure in Sweden

Sick building syndrome in relation to domestic exposure in Sweden

Sick building syndrome in relation to domestic exposure in Sweden

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Most studies on sick building syndrome (SBS) are cross-sectional and have dealt with symptoms among office workers. There are very few longitudinal cohort studies and few studies on SBS in relation to domestic exposures. The aim of this study was to investigate changes in SBS symptoms during the follow-up period and also to investigate changes in different types of indoor exposures at home and relate them to SBS symptoms in a population sample of adults from Sweden. We also wanted to investigate if there was any seasonal or regional variation in associations between exposure and SBS. Methods: A random sample of 1,000 people of the general population in Sweden (1991) was sent a self administered questionnaire. A follow-up questionnaire was sent in 2001. Results: An increased risk for onset of any skin symptoms (risk ratio (RR) 2.32, 1.37–3.93), mucosal symptoms (RR 3.17, 1.69–5.95) or general symptoms (RR 2.18, 1.29–3.70) was found for those who had dampness or moulds in the dwelling during follow-up. In addition people living in damp dwellings had a lower remission of general symptoms and skin symptoms. Conclusions: Dampness in the dwelling is a risk factor for new onset of SBS symptoms. Focus on indoor environment improvements in dwellings can be beneficial both for the inhabitants and the general population. Reducing dampness in buildings is an important factor for reducing SBS symptoms in the general population.

Key Words: Asthma, building dampness, cohort study moulds, indoor environment, sick building syndrome (SBS)

Introduction

Sick building syndrome (SBS) is a set of non-specific

symptoms occurring in a particular building and the

symptoms normally improve or disappear when

people are away from the building. Such non-specific

symptoms are common in the general population [1]

and even more common among people living in

buildings with indoor air problems. The syndrome

has been defined empirically on the basis of case

reports in which the occupants of a specific building

described similar symptoms that were attributed to

indoor climate problems [2]. Various factors, such as

wall-to-wall carpeting, type of ventilation system,

high room temperature, low supply of outdoor air,

and low air humidity have been shown to influence

the prevalence of SBS symptoms [3–5]. Female

gender and history of allergic disorder have been

shown in many studies to be important risk factors

for SBS symptoms [3–6]. In buildings with a CO2 level<800 ppm the risk for SBS symptoms decreased [7] and SBS symptoms can be more common at

personal airflow rates below 10 l/s [8].

Building dampness is a common indoor exposure,

and has been shown to be related to an increased

prevalence of both asthmatic symptoms and SBS

[9–11]. In a review by Bornehag et al. (2001), it was

concluded that dampness in buildings is a risk factor

and there are associations between both self-reported

and observed dampness and symptoms [9]. The

dampness approximately doubles the risk of health

effects [9,10]. Building dampness in Swedish multi-

family residential buildings has been reported to be

related to a pronounced increase of symptoms com-

patible with SBS symptoms [12].

One common indoor source of volatile organic

compounds (VOC) is emissions from fresh paint.

Correspondence: B Sahlberg, Department of Occupational and Environmental Medicine, Uppsala University Hospital and Uppsala University, SE-751 85

Uppsala, Sweden. Tel: þ46 186 113869. Fax: þ46 185 19978. E-mail: Bo.Sahlberg@medsci.uu.se

(Accepted 7 September 2009)

� 2010 the Nordic Societies of Public Health DOI: 10.1177/1403494809350517

Two recent studies have shown that 26%–32% of the

Swedish population have had the interior of their

dwelling painted during the last year [1,13].

Nowadays most indoor paint in Sweden is water

based [13] and emissions from fresh indoor paint in

the dwelling may cause airway symptoms [13] and

eye irritation [1,14]. In addition, tobacco smoking is

related to many diseases such as chronic obstructive

pulmonary disease (COPD), lung cancer and ischae-

mic heart disease [15]. Some SBS symptoms,

e.g. general symptoms, are also related to tobacco

smoking [16] and some studies have shown that

exposure to environmental tobacco smoke (ETS)

contributes to the occurrence of SBS symptoms [17].

Most studies on SBS are cross-sectional and have

dealt with symptoms among office workers. There

are hardly any longitudinal cohort studies [18,19]

and few studies on SBS in relation to domestic

exposures [1,6,20–22]. Moreover only a few studies

deal with risk factors for SBS symptoms in the

general population [1,19]. To our knowledge there

are no longitudinal studies on SBS symptoms in

relation to home environmental factors. Since a

cross-sectional study does not give strong evidence

on causal relations, there is a need for longitudinal

studies on SBS, especially in the general population.

Aim

The aim of this study was to investigate changes of

SBS and different types of indoor exposures at home

over a 10-year follow-up period (1991–2001) in a

population sample of adults from Sweden. Moreover

we studied the onset of SBS in relation to personal

factors at baseline and home exposure during the

follow up. We also wanted to investigate if there was

any seasonal or regional variation between indoor

exposures and SBS symptoms.

Material and methods

Study population

The study population consisted of a random sam-

ple of 1,000 persons in the general population aged

20–65 years in 1991. The sampling was done by

Statistics Sweden, which is a central government

authority for official statistics and other government

statistics, and in this capacity also has the responsi-

bility for coordinating and supporting the Swedish

system for official statistics. In order to study sea-

sonal effects, the sample was further divided into

four sub-samples (250 subjects in each). The subjects

in each sub-sample received the standardized

self-administered questionnaire during one of the

four seasons (September 1991 to August 1992). The

response rate was 70%. A follow-up questionnaire

was sent after 10 years (September 2001 to August

2002) to all subjects who participated in the first

study (n¼ 695), following the same division into seasonal sub-groups as in the first study. The

response rate in the follow-up was 61% (n¼ 427).

Assessment of symptoms and personal factors

The questionnaire contained questions on age, sex,

hay-fever and smoking habits. Current smokers were

defined as those participants in the interview who

reported smoking, smoking more than one cigarette

per day, and reported ceasing smoking less than a

year ago. The questionnaire contained questions

requiring ‘‘yes’’ or ‘‘no’’ answers on 16 different

SBS symptoms used in earlier investigations [1].

In Table I the SBS symptoms are listed. The recall

period was three months. Work-related symptoms

were not addressed in this study. There was one

question asking whether the symptoms disappeared

or improved when being away from the workplace or

the home environment. However, this information

was not used in this study, which covers symptoms

regardless of the subject’s opinion on causes.

The prevalence of symptoms was calculated for

each of the 16 symptoms. The symptoms were

classified as eye, nasal, throat, facial dermal, or

general symptoms, and the prevalence of subjects

with at least one symptom in each group was

calculated. The prevalence of subjects with at least

one mucous membrane symptom (eye irritation,

swollen eyelids, nasal obstruction, dryness in throat,

sore throat, or irritating cough), dermal symptoms or

general symptoms was calculated.

Assessment of information on the dwelling

The questionnaire requested information on building

age, type of building, type of ventilation system, air

humidification, presence of wall-to-wall carpets, and

four different signs of microbial growth, malodours

or building moisture during the last 12 months. The

questions on building dampness have been validated

in a previous study [23]. The validation was made by

comparing self-reported building dampness by the

inhabitant in the dwelling, with observations on signs

of building dampness made by an occupational

hygienist visiting the dwellings. If the presence of at

least one observed sign of building dampness was

used as the gold standard, sensitivity was 74% and

specificity was 71%. The questionnaire used in the

follow up contained three additional questions on any

Sick building syndrome and domestic exposure: cohort study in Sweden 233

building dampness, any indoor painting, and any

wall-to-wall carpeting in any of the dwellings the

participants had lived in during the 10-year follow-up

period. These questions were used to study associa-

tions with onset of SBS.

Statistical methods

Changes in prevalence of health parameters or

building characteristics were tested by the

McNemar test. For each person, the weekly occur-

rence of any mucosal, dermal or general symptom

was calculated both in the beginning and at the end of

the follow-up period. Onset of any mucosal symptom

was defined as presence of at least one mucosal

symptom at the end of the follow-up period, but

absence of any mucosal symptom in the beginning.

Onset of any dermal or any general symptom was

defined in a similar way. Remission of symptoms

was defined as presence of symptoms (mucosal,

dermal or general) in the beginning and absence of

the particular type of symptom at the end of the

follow up. Multivariate statistical analysis was per-

formed by multiple binominal regression, calculating

relative risk (RR) with 95% confidence interval (CI)

for onset or remission of each type of symptom

group. When studying onset of symptoms, partici-

pants with the particular type of symptoms at base-

line were excluded. When studying remission of

symptoms, only participants with the particular

symptom at baseline were included. In the binomial

models control was made for possible confounding

by keeping age at baseline, gender, current smoking

at baseline, and hay fever at baseline together with the

three home-exposure variables.

In addition, associations between dampness during

the follow-up and onset of symptoms was studied in

different sub-groups separately, stratifying for sex,

hay fever at baseline, smoking at baseline, region at

baseline (southern, mid and northern Sweden), and

the four seasons. In all statistical analyses, two-tailed

tests and a 5% level of significance was applied.

All analyses were done with SAS� system version 9.1.

Results

The follow up study was restricted to those 427

people who participated in both the initial study and

the follow up-study. A comparison between partici-

pants (n¼ 427) and non-participants (n¼ 268) gave the following results: the non-participants did not

differ significantly from the participants with respect

to age, gender, hay fever, doctor’s diagnosed asthma,

or smoking habits at baseline. The initial mean age

was 42 years. The prevalence of asthma had numer-

ically increased and the prevalence of hay fever

had significantly increased (Table I). There were

no significant changes in chronic bronchitis. The

prevalence of current smoking had decreased and the

prevalence of ex-smokers had increased significantly

(Table I). The prevalence of mucosal symptoms

remained unchanged, and any general and any skin

symptoms had decreased. Among individual symp-

toms cold and headache had decreased (Table I).

Some improvements in the home environment

with regard to building dampness and indoor moulds

were observed. Visible indoor mould during the last

year had decreased. Also, mouldy odour and any sign

of building dampness had decreased. Other types of

odour, excluding mouldy odour, had decreased. The

proportion of dwellings with mechanical ventilation

either in living rooms or bedrooms had slightly

increased (Table II). The prevalence of any type of

building dampness had increased, but water leakage,

Table I. The prevalence of asthma, allergies, chronic bronchitis,

smoking habits and type of symptoms among participants in both

studies.

Prevalence (%)

1991

(n¼427) 2001

(n¼ 427) p-valuea

Asthma 7.8 9.7 0.18

Any type of allergy 27 27 1.00

Hay fever 12 16 0.04

Chronic bronchitis 6.9 6.2 0.56

Current smoker 28 19 0.002

Ex-smoker 22 32 <0.0001 Type of symptom

Eye irritation 16 19 0.27

Swollen eyelids 10 9 0.56

Nasal catarrh 12 11 0.61

Nasal obstruction 20 18 0.22

Dryness in the throat 18 17 0.46

Sore throat 8 6 0.08

Irritating cough 7 10 0.06

Any mucosalb 41 43 0.73

Headache 22 17 0.02

Tiredness 35 33 0.35

Sensation of getting a cold 23 16 0.0005

Nausea 6 7 0.32

Any generalc 48 42 0.02

Facial itching 9 6 0.11

Facial rash 8 8 1.00

Itching on the hands 9 8 0.78

Rashes on the hands 10 8 0.18

Eczema 13 9 0.06

Any skind 21 16 0.02

aDifferences tested by McNemar statistical test. bThe prevalence

of subjects with at least one symptom classified as mucosal. cThe

prevalence of subjects with at least one symptom classified as

general. dThe prevalence of subjects with at least one symptom

classified as skin.

234 B. Sahlberg et al.

sign of floor dampness and visible moulds had

decreased during the study period. A large propor-

tion (70%) had painted indoors during the follow-up

period and nearly a third of these had used solvent-

based paints. Furthermore 31% of the subjects had

lived in a dwelling with wall-to-wall carpet and a third

had lived in a dwelling with some type of building

dampness.

The cumulative incidence of subjects with new

onset of at least one symptom in each group was 12%

for skin symptoms, 28% for mucosal symptoms and

25% for general symptoms. For headache the cumu-

lative incidence was 10% and for tiredness it was

15%. An increased onset for any skin, mucosal or

general symptoms was found for those who had any

type of building dampness in the dwelling during

follow up. We did not find any relations between

onset of any symptoms and indoor painting, either

for any type of paint or for use of solvent-based

paints. Among personal factors hay fever at baseline

was related positively to onset of skin and mucosal

symptoms, and age was related to onset of mucosal

membrane symptoms (Table III). We also analyzed

the relationship between specific mucosal symptoms

such as eye, nose and throat and building factors and

personal factors. Onset of eye symptoms (RR 2.41,

1.38–4.35) and throat symptoms (RR 2.33, 1.10–

4.95) was significantly more common in damp

dwellings.

In the stratified analysis, we analyzed associations

between symptoms and dampness in the dwelling.

There was no consistent gender difference for the

association between onset of any type of symptoms

and dampness in the dwelling. Subjects with hay

fever had a numerically higher RR for onset of

general symptoms and skin symptoms, but confi-

dence intervals were overlapping. No regional or

seasonal differences for RR for onset of any symp-

toms in relation to dampness were observed.

Smokers at baseline had a consistently higher RR

for onset of general, skin and mucosal symptoms in

relation to dampness as compared to non smokers.

The RR was two to eight times higher for smokers,

but confidence intervals were partly overlapping.

Remission from general symptoms or skin symptoms

was less likely in subjects with dampness in the

dwelling, and remission from general symptoms was

less likely if the dwelling had been painted indoors

during follow up. Moreover, remission from skin

symptoms was less likely in subjects with hay fever at

baseline (Table IV).

Discussion

The main findings in this study were that the

people who had any type of building dampness

had a significantly higher incidence for general

symptoms, skin symptoms and mucosal symptoms.

Table III. Relationship between onset of weekly symptoms, building factors and personal factors.