As part of a program to study occupational respiratory
disease in the nonindustrial environment, we investigated
building-related respiratory health in the employees of a
large 20-story office building in the northeastern United
States. Since the mid-1990s, the building had leaked through
the roof, around windows, and through sliding doors of
terraces. The upper floors had suffered the most water damage
and mold contamination. During investigation of these
problems, the building was found to be operating at a negative
pressure with respect to the outdoors, which could exacerbate
water incursion through the building envelope. Furthermore,
there had been plumbing leaks on many floors which had damaged
interior walls. The first major construction activity related
to water incursion began in 2000, with repair of roof copings
and brick caulking. From 2000 to 2002, cubicle partitions and
carpets were cleaned, wetted carpet and stained wallboard
replaced, wallpaper and underlying mold removed from
bathrooms, upgrades to the air handling system made, and
windows caulked. In 2002, permanent repairs on the building
exterior, including roof replacement, began to prevent water
incursion.
Building occupants had reported health conditions that they
considered building related. Symptom onset spanned several
years, with an increase in symptoms and frequency of
complaints beginning in the fall of 2000. Sentinel cases of
postoccupancy-onset asthma, hypersensitivity pneumonitis (HP),
and sarcoidosis had been diagnosed, and the persons affected
had been relocated to another facility. HP is an
immune-regulated granulomatous disease that has been
associated with fungal contamination, and it has been found to
coexist with asthma in damp office buildings (Arnow et al.
1978; Kreiss 1989; Hoffman et al. 1993; Jarvis and Morey
2001). Sarcoidosis is an immune-regulated granulomatous
disease of unknown etiology.
In this article we report evidence of excesses of
respiratory symptoms and physician diagnosis of asthma in the
occupants of the water-damaged building as well as
verification of self-reported respiratory illness with
objective testing. We also describe the burden of illness in
terms of absences, use of breathing medications, and
health-related quality of life.
Study design and population. In
September 2001, we offered a questionnaire to all 1,327
employees working in the building. The questionnaire was
administered to groups of approximately 50 employees at a
time, using schedules prepared by management. During each
group session, National Institute for Occupational Safety and
Health (NIOSH) staff described the purpose of the survey and
the consent process and read the questions aloud from overhead
transparencies as the participants completed them. By
completing the questionnaire, the participants were indicating
consent to take part in the survey. The questionnaire
comprised sections on demographics; symptoms (upper and lower
respiratory, systemic, headache, and difficulty concentrating)
in the last 4 weeks and 12 months, and in relation to being in
the building; physician diagnosis of asthma, HP, and
sarcoidosis, with dates of diagnosis; smoking history; and
work history in the building. The completed questionnaires
were electronically scanned into a database and hand-checked
for quality control.
We used the September questionnaire to identify a group of
employees who had worked in the building for at least 1 year
and who met either an epidemiologic case definition for lower
respiratory illness or a comparison group definition. The
respiratory case definition was three or more of five lower
respiratory symptoms (wheeze/whistling in the chest, chest
tightness, shortness of breath, coughing, awakening by attack
of breathing difficulty) occurring weekly over the past month;
or at least two of three symptoms consistent with HP
(shortness of breath when hurrying on level ground or walking
up a slight hill, fever and chills, flulike achiness or achy
joints) occurring weekly over the past month; or current
asthma with postoccupancy physician diagnosis, or
physician-diagnosed HP or sarcoidosis. The comparison group
definition was none of the respiratory case lower respiratory
or HP-like symptoms in the past year and none of the
respiratory case diagnoses.
We invited the 202 employees who met the case definition
and the 154 employees who met the comparison group definition
to participate in a questionnaire and medical testing survey
in June 2002. During the site visit, an additional 15
employees asked to take part in the survey. All participants
provided written informed consent (approved by the NIOSH Human
Subjects Review Board). We used results of the June
questionnaire to reclassify participants into the respiratory
case or comparison groups. Participants who reported lower
respiratory or systemic symptoms but who did not meet the
criteria of a respiratory case formed a third, "fewer
symptoms" group.
Questionnaire. Participants
completed an interviewer-administered computer-based
questionnaire. The June 2002 questionnaire included sections
on demographics, work history, health and symptom history,
physician diagnoses, smoking, home environment, and job stress
and satisfaction as used in the U.S. Environmental Protection
Agency (EPA) Building Assessment Survey and Evaluation (BASE)
study (U.S. EPA 1994), and health-related quality of life from
the SF-12 (Medical Outcomes Study, Short Form; Ware et al.
1996). We included questions on the use of beta-agonist and
corticosteroid inhalers, over-the-counter breathing
medications, and other asthma medications in the previous 4
weeks, as well as oral corticosteroid use in the previous 12
months, adapted from an asthma-severity score module (Blanc et
al. 1996). To help with recall, participants were asked to
bring to their testing session a list of the medications that
they were taking for breathing problems.
Spirometry. Qualified technicians
followed standard guidelines for spirometry (American Thoracic
Society 1995). We compared the test results to expected values
for a healthy, nonsmoking person of the same age, height, sex,
and race using spirometry reference values and 95% normal
confidence intervals (CIs) generated from the third National
Health and Nutrition Examination Survey (NHANES III)
(Hankinson et al. 1999). Abnormal test results were
categorized as having a pattern of obstruction, restriction,
or a "mixed" pattern of both airways obstruction and a low
forced vital capacity (FVC) (American Thoracic Society 1995).
We defined airways obstruction as a low forced expiratory
volume in 1 sec (FEV1) to FVC ratio
(FEV1/FVC%) with low FEV1. We defined
restriction as a low FVC and normal FEV1/FVC%.
Methacholine challenge testing.
To detect bronchial hyperresponsiveness (BHR),
we performed methacholine challenge testing (MCT) using
standardized techniques (Crapo et al. 2000) with 0.125, 0.5,
2, 8, and 32 mg/mL methacholine. Five breaths of nebulized
methacholine were administered for each dose, with
FEV1 measured 30 and 90 sec later. If
FEV1 dropped > 20% of the baseline value, no
further methacholine was given. We report methacholine dose as
PC20, which is the provocative concentration of
methacholine that causes an interpolated 20% decline in
FEV1 from the baseline. We defined BHR as a
PC20 of ≤ 4.0 mg/mL, and borderline BHR as a
PC20 between 4.1 and 16.0 mg/mL (Crapo et al.
2000).
Bronchodilator testing. In
subjects with baseline FEV1 < 70% of the
predicted value, MCT was not performed, but a bronchodilator
test was performed to detect any reversible
bronchoconstriction. Two puffs of a beta-agonist were
administered via metered dose inhaler and were followed by
spirometry. We defined reversibility as a 12% and 200 mL
FEV1 improvement after bronchodilator
administration (American Thoracic Society 1991).
Allergen skin prick testing. We
applied extracts of seven common indoor and outdoor allergens
and three mold mixes using the GreerPIK system (Greer
Laboratories, Lenoir, NC): dust mite mix (Dermatophagoides
farinae and D. pteronyssinus), German cockroach
(Blattella germanica), cat hair, seven grass mix,
ragweed mix, common weed mix, Eastern eight tree mix,
Dematiaceae mix (outdoor molds: Alternaria
tenuis, Cladosporium herbarum, Helminthosporium sativum,
Pullularia pullulans, Spondylocladium atrovirens, Curvularia
spicifera), Aspergillus mix, and Penicillium
mix. The negative control was 50% glycerin in water, and
histamine served as a positive control. For each
wheal, the mean diameter (average of the length and width) at
15 min was calculated. We defined a positive reaction as an
average diameter at least 3 mm larger than the negative
control and > 25% of the average diameter of the positive
control. For the purposes of this study, atopy was defined as
at least one positive skin test on allergy testing, using a
total of seven common antigen extracts (excluding the mold
mixes).
Data analysis. We compared the
prevalence rates of respiratory symptoms and self-reported
medical diagnoses observed in the building occupants during
the September 2001 survey to the U.S. adult prevalence rates
obtained from NHANES III [National Center for Health
Statistics (NCHS) 1996], the 2001 data for Connecticut from
the Behavioral Risk Factor Surveillance System (BRFSS)
(National Center for Chronic Disease Prevention and Health
Promotion Behavioral Risk Factor Surveillance System 2001),
and data for occupants of 41 office buildings with no known
indoor environmental problems (Apte et al. 2000). For
comparisons with NHANES III, we used indirect standardization
for race (black, Hispanic, white), sex, age (17-39 years of
age versus 40-69 years of age), and cigarette smoking status
(current, former, or never smoker). For comparisons with
BRFSS, we standardized for sex. We derived 95% CIs using a
method that assumes that the observed data are from a Poisson
distribution (Kahn 1989).
To estimate incidence density rates of physician-diagnosed
adult-onset asthma, for each participant we calculated
person-time at risk for two time periods: from 16 years of age
to building occupancy and from building occupancy to the
September 2001 survey date. For subjects with
physician-diagnosed adult-onset asthma, time at risk ended on
the date of diagnosis. Time at risk for each participant was
summed to give person-years at risk. Participants with
childhood asthma did not contribute any time at risk.
We used SAS software (version 8.02; SAS Institute Inc.
Cary, NC) to analyze the data. Chi-square tests were used in
statistical analysis of two-way classification tables. We used
the Cochran-Mantel-Haenszel test in analysis of differences
between proportions after adjustment for smoking, and we used
the Cochran-Armitage test in analysis for linear trends in
proportions. We used the SAS GLM procedure to model number of
days lost and Duncan's multiple range test for multiple means
comparisons.
September 2001 Survey
Table 1.
![Table 1](Asthma_from_leaky_building_files/tab1sm.jpg)
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Table 2.
![Table 2](Asthma_from_leaky_building_files/tab2sm.jpg)
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Table 3.
![Table 3](Asthma_from_leaky_building_files/tab3sm.jpg)
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Table 4.
![Table 4](Asthma_from_leaky_building_files/tab4sm.jpg)
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Participation. Participation was
67% (888/1,327) in the cross-sectional questionnaire study.
Participants were predominantly white, in their mid-forties,
former or never smokers, who had been working in the building
for about 6 years (Table 1). We had demographic and
participation information on the 689 employees working for one
of the two building tenant organizations. These employees had
a mean age of 45 years, and 74% were white, 19% were black,
and 53% were female. There was 76% participation among these
employees. Comparison between participants and nonparticipants
showed no differences in mean age or race. There were
proportionately more females among participants than among
nonparticipants (57% vs. 40%, p < 0.01).
Excess respiratory symptoms and
physician-diagnosed asthma. In comparisons with
the U.S. adult population, prevalence ratios ranged from 2.2
to 2.5 for wheezing, lifetime asthma, and current asthma
(p < 0.05; Table 2). Nasal and eye symptoms were
more prevalent in the building occupants than
lower-respiratory symptoms, but were less elevated compared to
U.S. adults (prevalence ratios 1.5 and 1.6, respectively,
p < 0.05). The building occupants reported wheeze,
nasal, or eye symptoms that improved when they were away from
work at 3.4 times the rate of the U.S. population (p
< 0.05). Compared to the state adult population, prevalence
ratios were 1.4 (95% CI, 1.2-1.6) for lifetime asthma, and 1.5
(95% CI, 1.3-1.9) for current asthma. A majority (60-70%) of
participants with wheeze, chest tightness, shortness of
breath, or cough in the last 4 weeks reported an improvement
in symptoms when away from the building. Prevalence ratios for
work-related lower respiratory symptoms compared to U.S.
office workers were elevated and ranged from 2.7 to 4.7
(p < 0.05; Table 3).
Adult onset asthma prevalence and
incidence. The prevalence of adult-onset asthma
was 12% (103/865). A comparison to the U.S. adult population
gave a prevalence ratio of 3.3 (95%, CI 2.7-4.0). Two-thirds
(66/103) of the adult-onset asthma occurred after occupancy of
the building. An analysis of adult-onset asthma incidence
density was conducted based on 19,173 person-years at risk
before building occupancy and 4,564 person-years at risk after
building occupancy. We found incidences of 1.9 per 1,000
person-years in the period before building occupancy and 14.5
per 1,000 person-years in the period after building occupancy.
The incidence rate ratio was 7.5, indicating a large increase
in asthma incidence in the period after building occupancy.
Asthma symptom severity and
exacerbation. The participants with
postoccupancy-onset, physician-diagnosed asthma had a higher
mean value for the sum of cough, wheeze, chest tightness, and
shortness of breath occurring once or more per week in the
last 4 weeks than any other participants (p <
0.05). There was also a significant trend (p <
0.01) in prevalence of lower respiratory symptoms that
improved when away from the building: 52% of those with
postoccupancy-onset asthma, 41% of those with adult
preoccupancy-onset asthma, 27% of those with childhood asthma,
and 23% of those with no physician-diagnosed asthma (Table 4).
HP and sarcoidosis. Eight
participants reported HP, five with postoccupancy-onset and
one with preoccupancy-onset HP (two people did not give
diagnosis dates). Sarcoidosis was reported by six
participants, three with postoccupancy onset, and two with
preoccupancy onset (one person did not give a date of
diagnosis). Fever and chills were reported as occurring once
or more in the last 4 weeks by 9%, flulike achiness or achy
joints by 22%, and excessive fatigue by 29% of participants. A
work-related pattern was noted by 22% of those with fever and
chills, by 30% of those with flulike achiness or achy joints,
and by 52% of those with excessive fatigue.
June 2002 Survey
Table 5.
![Table 5](Asthma_from_leaky_building_files/tab5sm.jpg)
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Table 6.
![Table 6](Asthma_from_leaky_building_files/tab6sm.jpg)
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Table 7.
![Table 7](Asthma_from_leaky_building_files/tab7sm.jpg)
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Figure 1.
Quality-of-life comparisons among symptom
groups. **p < 0.01, Cochran-Armitage
trend test. |
Figure 2.
Quality of life in the respiratory case group
and the fewer symptoms group, stratified by
work-relatedness of symptoms. *p < 0.05
and **p < 0.01, Chi-square test. |
Figure 3.
Allergy skin test results by asthma diagnosis.
*p < 0.05 and **p < 0.01,
Chi-square test. |
Participation. There were 248
participants in the June 2002 survey. Participation was higher
among the invited employees meeting the respiratory case
definition in September 2001 (142/202; 70%) than among the
comparison group invitees (91/154; 59%). Based on the June
2002 questionnaire results, there were 140 participants in the
respiratory case group, 63 participants in the fewer symptoms
group, and 44 participants in the comparison group. One
participant had missing questionnaire information and could
not be classified. A little more than half of those
asymptomatic in September 2001 reported symptoms 9 months
later, with 17% achieving respiratory case status, and 38%
falling into the fewer symptoms group. In contrast, a majority
(81%) of those meeting the respiratory case definition in
September 2001 still met this definition 9 months later, 17%
fell into the intermediate group, and 2% became asymptomatic.
The demographics of the June 2002 participants stratified by
respiratory status are given in Table 5. There were more
females and more current smokers in the respiratory case
group.
Lung function tests, breathing medication use,
and reported respiratory health. Respiratory
cases had the highest proportions of abnormal breathing tests
and breathing medication use; the fewer symptoms group had the
next highest; and the comparison group had the lowest
proportions of these two outcomes (Tables 6 and 7). Test
results indicated more obstruction than restriction, and the
respiratory cases had a trend for a higher prevalence of
obstruction than the other participants. BHR was higher in the
two groups with symptoms than in the comparison group, but
this finding was not significantly different. We found very
little breathing medication use reported by the comparison
group as compared to almost half of the respiratory cases.
Analyses on the never-smokers showed similar trends, with a
prevalence of abnormal lung function tests and medication use
combined of 71% for respiratory cases, 30% for participants
with fewer symptoms, and 12% for the comparison group.
Quality of life. We compared
responses to health-related quality-of-life questions among
the three symptom status groups. We found statistically
significant trends for increasing impairment in health-related
quality of life with increasing severity of respiratory
symptoms. The largest differences were seen for reported
physical limitations (Figure 1). Within the respiratory case
and the fewer symptoms groups, we found statistically
significant poorer health-related quality of life in relation
to the presence of work-related symptoms, except for general
health status (Figure 2). Similar results were found for
health-related quality of life and postoccupancy symptom
onset, except that statistical differences were seen for
limitations in climbing stairs, physical health-limiting
accomplishments, and physical health limiting the kind of
activities.
Job stress/dissatisfaction. There
were no statistical differences among symptom status groups
for responses on job satisfaction or how often a person was
required to work hard. Being very or somewhat satisfied with
their job was reported by 87% of respiratory cases, 90% of the
group with fewer symptoms and 93% of the comparison group.
Being required to work hard frequently or very often was
reported by 51% of respiratory cases, 62% of the intermediate
group, and 45% of the comparison group.
Work days lost. The number of
days off work in the last 12 months due to respiratory
problems was significantly associated with symptom status
(p < 0.01). The respiratory cases had missed a
mean of 6.9 days as compared to 1.7 days for the group with
fewer symptoms and 2.0 days for the asymptomatic group. We
found that 34% of respiratory cases had ≥ 6 days of
respiratory sick leave, compared to 11% of the fewer symptoms
group and 4.7% of the asymptomatic comparison group
(p < 0.01). In contrast, there was no
statistically significant difference between the three groups
for nonrespiratory sick leave. The respiratory cases lost a
mean of 4.5 days, the group with fewer symptoms lost 7.5 days,
and the asymptomatic group lost 4.1 days due to nonrespiratory
conditions.
The number of respiratory sick days was similar for
symptomatic participants regardless of whether the onset was
pre- or postoccupancy. A large effect was seen for having
respiratory symptoms that improved away from the building.
Respiratory cases with work-related respiratory symptoms had
more respiratory sick days than those with symptoms that did
not improve away from the building (9.4 vs. 2.4, p
< 0.01). In the group with fewer symptoms, those with
work-related respiratory symptoms had more respiratory sick
leave than those with symptoms with no work-related pattern
(3.7 vs. 1.1, p < 0.05).
We estimated sick days over the past year for respiratory
conditions and total sick leave for building occupants by
applying the mean work days missed for the three symptom
groups to the number of participants in those categories from
the September 2001 questionnaire (816 participants had
adequate data). Respiratory health problems accounted for 34%
of sick leave days (2,490/7,402). The respiratory case group
represented 25% of the September 2001 participants but
contributed 56% (1,401/2,490) of the respiratory sick leave
days. Using the mean of 2 days of respiratory sick leave
reported by the comparison group as a non-building-related
baseline for building occupants gives an estimated 858 days of
excess respiratory sick leave (2,490-1,632). Thus, up to 12%
(858/7,402) of the preceding 12 months of employee sick leave
days might have been attributable to building-related effects.
Breathing medication use. We
looked at the prevalence of the use of asthma-controller
medications (inhaled corticosteroids, cromolyn, nedocromil,
oral antileukotrienes) and reliever medications (short-acting
beta-agonists and ipratropium bromide) in the last 4 weeks in
participants with physician-diagnosed asthma for comparison
with a national sample of 1,788 U.S. adults with current
asthma (Adams et al. 2002; Fuhlbrigge et al. 2002) using
two-sample tests of proportions. Use of an asthma controller
was reported by 39% of our study group versus 21% of U.S.
asthma cases overall (p < 0.01). The prevalence of
39% asthma-controller use was marginally higher (p =
0.07) than the value of 29% reported for U.S. cases with
severe persistent symptoms in the last 4 weeks. Reliever use
was reported by 50% of our group versus 63% of U.S. cases
(p < 0.05).
Skin prick allergy tests. Over
half of the participants met the definition for atopy. There
was no statistical difference in the prevalence of atopy among
the respiratory case group, the group with fewer symptoms, and
the comparison group. However, preoccupancy-onset asthma was
associated with a higher prevalence of atopy (p <
0.05). The results of individual skin prick allergen tests
showed that persons with preoccupancy-onset asthma had a
higher prevalence of positive reactions to cat, dust mites,
and weed mix (p < 0.01) as well as to cockroach
allergens (p < 0.05). We found that the
postoccupancy-onset asthma cases had the lowest reaction to
the mold mixes (p = 0.05; Figure 3).
Physician-diagnosed asthma and respiratory symptoms
occurred in excess among our study participants and was
confirmed by an excessive rate of airway obstruction and BHR.
Studies of building occupants with known health concerns are
subject to reporting bias. In our study, in addition to
reported symptoms and physician diagnoses, we examined
measures of respiratory disease, including medication use and
medical tests. Two-thirds of those classified as respiratory
cases based on symptoms or physician diagnoses had objective
pulmonary function abnormalities or used prescription
medications for breathing difficulties (given with the goal of
normalizing lung function). The higher rate of lung function
abnormalities and breathing medication use in the participants
reporting respiratory symptoms validates the symptom reports.
The majority (60-70%) of participants with respiratory
symptoms reported a work-related pattern, implying a
building-related exposure. The 7% overall prevalence of
work-related wheeze was higher than the 2-4% in studies of
nonproblem buildings (Apte et al. 2000) and higher than the
2-6% found in studies of problem buildings (Malkin et al.
1996). In the 9-month interval between the building-wide
questionnaire survey and the nested case-control survey, more
than half (55%) of the comparison group chosen because they
had no lower respiratory or systemic symptoms in September
2001 had become symptomatic, including 17% who were classified
as respiratory cases. Improvement was rare in September 2001
cases (17%), suggesting a continued effect of building
occupancy on respiratory health. Some of this response pattern
may be attributable to overreporting due to general concern
about water incursions and sentinel cases with health effects,
but such concerns had been present since before the September
2001 survey.
The estimated incidence of physician-diagnosed, adult-onset
asthma among the study participants (1.9 per 1,000
person-years) before building occupancy was within the range
of other estimates for adults, for example, 2.1 per 1,000
person-years (McWhorter et al. 1989), 3.8 per 1,000
person-years (Sama et al. 2003), and about 1 per 1,000
person-years (Reed 1999). In contrast, after building
occupancy, incidence rose 7.5 times to 14.5 per 1,000
person-years, consistent with the symptoms that developed in
the previously asymptomatic comparison group.
The burden of respiratory problems in this population was
reflected in substantial respiratory sick leave attributable
to building occupancy (estimated at 12% of total). The
presence of work-related respiratory symptoms was positively
associated with respiratory sick leave, but time of symptom
onset was not, suggesting that having a work-related pattern
to respiratory symptoms was a larger determinant of
respiratory sick leave than whether the symptoms arose before
or after building occupancy.
The proportion of our study respiratory cases with ≥ 6 days
of respiratory sick leave was 34%. In comparison, a population
study of 1,788 adults with asthma in the United States found
that 11% of participants had ≥ 6 days of sick leave in the
past year related to their asthma (Fuhlbrigge et al. 2002). In
our study, respiratory cases had a mean of 6.9 respiratory
sick days, compared to 4.4 annual work absences because of
breathing problems among Canadian asthmatics (Ungar and Coyte
2000). In the Canadian study more productivity was lost due to
a decrease in level of functioning at work on days when
breathing problems were worse than usual than due to days off
work. Although we have no estimate of productivity loss due to
a decrease in functioning at work for our study participants,
the high prevalence of work-related symptom exacerbation
suggests a substantial decrease in productivity might have
occurred. High respiratory morbidity was also indicated by the
high use of asthma-controller medication and the decreased
prevalence of quick-relief medications. This pattern of
medication use is consistent with persistent asthma associated
with daily work-related exacerbation.
We found strong associations between respiratory symptom
status and lower health-related quality of life, confirming
the social burden of respiratory morbidity in building
occupants. In contrast, we found no relation between job
stress, job satisfaction, or perceived work burdens with
symptom status; this is consistent with the findings of
another investigation of building-related respiratory disease
(Jarvis and Morey 2001) and reduces the likelihood that
disgruntled employees in a problem building exaggerate their
symptoms.
The specific etiology and mechanisms of the respiratory
disease in this building remain undefined. The skin prick test
results for immediate hypersensitivity responses to common
aeroallergens were unexpected. Preoccupancy-onset asthma was
associated with atopy, as anticipated [National Asthma
Education and Prevention Program (NAEPP) 1997; Peden 2000].
However, postoccupancy-onset asthma cases had much lower
prevalence of IgE-mediated allergen skin-test positivity
(atopy). Perhaps the airway inflammation was not driven by an
IgE mechanism. It is possible that nonbiologic irritant
exposures were present, and furthermore, although molds have
allergenic properties (Lander et al. 2001), the development of
asthma in damp/moldy conditions may not be IgE mediated
(Douwes et al. 2003; Savilahti et al. 2001).
The rarity of clusters of HP in the general population
points to a work-related etiology for the cluster in the
building occupants. The recent Institute of Medicine report on
damp indoor spaces and health found sufficient evidence for an
association between mold or other agents in damp indoor
environments and upper respiratory tract symptoms, cough,
wheeze, asthma symptoms in sensitized persons, and HP in
susceptible persons (Institute of Medicine 2004). The cluster
of sarcoidosis raises concern that this granulomatous lung
disease was misdiagnosed HP (Forst and Abraham 1993) or has
overlapping environmental causes (Kucera et al. 2003).
The major limitation of the present study is the possible
influence of participation bias. We had a 67% participation in
our September 2001 survey, and differences in health status of
participants and nonparticipants could have led to
overestimation of symptom and asthma prevalence, particularly
since women were more likely to be participants. Using the
most conservative approach, we compared minimum possible
prevalences among the entire building population to the
external reference populations. We still found excesses of
asthma and symptoms in comparison to the U.S. population and
to office workers in buildings not known to have indoor
environmental problems (data not shown), but we found no
differences in asthma prevalence in comparison to the state
population. Counterbalancing possible response bias among
those occupants who participated in our study is our finding
of gradients of nonsubjective tests and reported medication
use in relation to symptom intensity.
In conclusion, the present study contributes to the growing
literature that water-damaged buildings can be associated with
work-related respiratory disease. This investigation documents
the considerable respiratory illness, adverse effects on
quality of life, and absenteeism that have placed personal,
social, and economic burdens on many employees and their
employers. Building-related respiratory disease warrants
increased public health, medical research, and policy
attention.