A time-series study of sick building syndrome: chronic, biotoxin-associated illness from exposure to water-damaged buildings

Abstract

The human health risk for chronic illnesses involving multiple body systems following inhalation exposure to the indoor environments of water-damaged buildings (WDBs) has remained poorly characterized and the subject of intense controversy. The current study assessed the hypothesis that exposure to the indoor environments of WDBs with visible microbial colonization was associated with illness. The study used a cross-sectional design with assessments at five time points, and the interventions of cholestyramine (CSM) therapy, exposure avoidance following therapy, and reexposure to the buildings after illness resolution. The methodological approach included oral administration of questionnaires, medical examinations, laboratory analyses, pulmonary function testing, and measurements of visual function. Of the 21 study volunteers, 19 completed assessment at each of the five time points. Data at Time Point 1 indicated multiple symptoms involving at least four organ systems in all study participants, a restrictive respiratory condition in four participants, and abnormally low visual contrast sensitivity (VCS) in 18 participants. Serum leptin levels were abnormally high and alpha melanocyte stimulating hormone (MSH) levels were abnormally low. Assessments at Time Point 2, following 2 weeks of CSM therapy, indicated a highly significant improvement in health status. Improvement was maintained at Time Point 3, which followed exposure avoidance without therapy. Reexposure to the WDBs resulted in illness reacquisition in all participants within 1 to 7 days. Following another round of CSM therapy, assessments at Time Point 5 indicated a highly significant improvement in health status. The group-mean number of symptoms decreased from 14.9±0.8 S.E.M. at Time Point 1 to 1.2±0.3 S.E.M., and the VCS deficit of approximately 50% at Time Point 1 was fully resolved. Leptin and MSH levels showed statistically significant improvement. The results indicated that CSM was an effective therapeutic agent, that VCS was a sensitive and specific indicator of neurologic function, and that illness involved systemic and hypothalamic processes. Although the results supported the general hypothesis that illness was associated with exposure to the WDBs, this conclusion was tempered by several study limitations. Exposure to specific agents was not demonstrated, study participants were not randomly selected, and double-blinding procedures were not used. Additional human and animal studies are needed to confirm this conclusion, investigate the role of complex mixtures of bacteria, fungi, mycotoxins, endotoxins, and antigens in illness causation, and characterize modes of action. Such data will improve the assessment of human health risk from chronic exposure to WDBs.

Introduction

The phrase “sick building syndrome” (SBS) has been used in reference to nonspecific health complaints thought to be associated with occupancy of certain buildings. The symptoms of SBS included any combination of sensory irritation, cough, wheezing, headache, cognitive disturbances, depression, light sensitivity, gastrointestinal distress, fatigue, weakness, pains, and other flu-like symptoms for which there have often been no objective signs [79], [112], [123]. The presence of symptoms was associated with exposure to specific indoor environments, and cases usually reported at least partial symptom resolution when removed from exposure. Occurrences of SBS were attributed to a variety of causes, including the emission of volatile organic compounds from building materials, pesticides, tobacco smoke, lighting, air exchange or circulation rates, and carbon monoxide, carbon dioxide, temperature, and humidity levels [141]. SBS complaints were tentatively attributed to microbial amplification, the visible colonization of microbes on surfaces in water-damaged buildings (WDBs), with increased frequency in recent years [2], [3], [47], [61], [73], [74], [83], [107], [124], [131], [140], [144]. Evidence indicated that the indoor air contained complex mixtures of fungi, bacteria, mycotoxins, endotoxins, antigens, and biologically produced volatile organic compounds to which building occupants were exposed through inhalation [11], [32], [51], [64], [93], [94], [109], [131], [134], [150], [152], [153], [154]. There was general acceptance of the hypothesis that chronic exposure to the air in WDBs is associated with allergic and irritant effects on pulmonary function [31]. Ample evidence indicated that asthma and hypersensitivity pneumonitis in children [10], [13], [67], [88], [102], [117] and adults [6], [15], [50], [52], [62], [65], [95], [121], [150], [159], [161] were associated with atopy and inflammation triggered by exposure to biologic contaminants in indoor air. Additional evidence indicated that dampness and fungi in schools were associated with respiratory distress in children [18], [42], [46], [98], [99], [108], [110], [132], [146], although some evidence indicated that toxic, rather than allergic, processes were involved [87], [147], [148]. Fungal mycotoxins were the suspected cause of pulmonary hemorrhage/hemosiderosis in infants [49], [59], [60], [89], [114], [122], [149], [154], [158]. Stachybotrys chartarum (a.k.a. S. atra) strains with high hemolytic activity were isolated from the indoor air and the bronchoalveolar fluid of children with pulmonary hemorrhage [54], [153], [154]. The Centers for Disease Control and Prevention (CDC) initially confirmed [27], [28], but later questioned, the association of mycotoxin inhalation and infant hemosiderosis [30]. Even more controversial [31] was the hypothesis that toxins inhaled in WDBs are associated with a multiple-system syndrome [45], [69], [92], [143], although the need for research that better characterized this potential human health risk has been well recognized [1], [2], [3], [20], [33], [37], [38], [47], [51], [58], [61], [75], [83], [100], [107], [124], [129], [131], [140], [145]. The scientific literature on the association between multiple-system symptoms and inhalation exposure to toxigenic microbes in WDBs is reviewed below, and a new study is described that attempted to overcome some of the methodological limitations identified in the previous studies.

Previous case reports and research studies have associated damp building environments and indoor microbial amplification with a multiple-system syndrome. However, the associations have generally been viewed as weak due to several methodological limitations. An early report by Croft et al. [40] described multiple-system symptoms in individuals living in a water-damaged home where S. chartarum was identified. Repeated medical evaluations, not well described in the report, failed to detect medical or laboratory abnormalities. The diagnosis of mycotoxicosis was made following trichothecene mycotoxin extraction from fungal swab samples, some symptom subsidence after removal from the home, and the lack of symptom recurrence during reoccupancy of the remediated building. Criticisms concerning the lack of exposure demonstration [145] were addressed in a recent report by Croft et al. [41]. Novel procedures were used to extract trichothecenes from the urine of four cases with multiple-system symptoms and exposure to buildings exhibiting microbial colonization. Extracted mycotoxins injected into weanling rats caused severe degeneration in the central nervous system and lung scarring. Although supportive of an association, methodological limitations inherent in case reports precluded firm establishment of an association.

Many studies have demonstrated the presence of Stachybotrys [5], [11], [72] and other fungal genera, including Aspergillus, Penicillium, Cladosporium, Chaetomium, Ulocladium, and Alternaria [35], [55], [72], [109], [134] in dust, on building materials and in the air of WDBs. Only weak associations were observed between fungal species identified on surfaces and in air [35], presumably because the time course of fungal-spore release to air is irregular. The rate of spore release to air is influenced by many factors, including microbial genera, surface hydrologic conditions, air currents and velocities, and interspecies competition [108]. Additional studies identified mycotoxins in dust or fungal samples [5], [55], [72], [118], [139], [152], [153]. The search for biomarkers of fungal exposure showed that much of the general population has IgG and/or IgE antibodies to fungi, but these markers were not diagnostic of disease, and have not discriminated between occupants of contaminated and uncontaminated buildings [1], [11], [38], [150]. Total spore counts [132] and levels of β(1→3)Glucan, a marker of biomass, showed statistically significant correlations with indoor pollutants, such as endotoxins, allergens, and fungi [66]. Although most of these studies did not examine relationships to the symptoms of building occupants, a literature review reported associations between β(1→3)Glucan levels, symptom prevalence, and measures of inflammation [131]. Both in vitro [76], [84], [101], [115] and rodent [93], [94], [119], [120], [125], [156] studies have demonstrated the ability of bacteria and fungi commonly found in WDBs or their toxins to elicit cytotoxicity and an inflammatory response, often in dose–response fashion [84], [93], [94], [101], [115], [119], [120]. Inflammatory responses to bacteria most often involved tumor necrosis factor alpha, interleukin 6, interleukin 1 beta, and nitric oxide [76], [84], [93], [115], whereas fungi or their metabolites most often induced tumor necrosis factor alpha, interleukin 6, and interleukin 2 [84], [94], [101], [156]. The observations that β(1→3)Glucan levels were correlated with symptom prevalence and inflammation, and that many bacteria and fungi elicited similar proinflammatory cytokine responses indicated that SBS in occupants of WDBs may be induced by the total biological load in inhaled air through a combination of toxic and immunologic processes.

Several studies have investigated complaints of SBS in populations occupying WDBs, but none have provided evidence sufficient to conclude that illness was firmly associated with exposure to biological agents. Johanning et al. [91] collected data using a self-administered symptom questionnaire and laboratory analyses from a cohort working in a water-damaged and fungal-infested building, and a control group. The prevalence of multiple-system symptoms differed between groups, and was positively correlated to the duration of employment in the exposed group. A small but statistically significant group difference in a biomarker of the immune system was also observed. The main shortcomings of the study were the lack of (1) data concerning fungal exposure in the control group; (2) evidence eliminating potentially confounding factors, such as preexisting illnesses and other exposures; (3) control for potential bias in the self-administered questionnaire data; (4) statistical control for multiple comparisons; and (5) a robust, objective finding. Similar shortcomings were present in another case-control study that identified large differences in questionnaire-reported symptoms between occupants of three water-damaged and fungal-contaminated buildings, and workers from two control buildings [77]. Neuropsychological tests provided objective evidence of effects in two studies by demonstrating cognitive and emotional profiles in exposed cases similar to those from patients with mild traumatic brain injury [9], [70]. However, the other limitations discussed above were not addressed.

Two cross-sectional studies with intervention overcame several of the limitation discussed above, but lacked objective indicators of effect [53], [144]. Ebbehoj et al. [53] reported that visible inspection and surface sampling in an office building identified evidence of high moisture and microbial growth with Trichoderma and Phoma fungi as the dominant genera. Mean multiple-system symptom scores in study participants were 66%, and variability in peak expiratory flow rate was 20%. Following building remediation, no visible evidence of microbial contamination was present. However, symptom scores decreased only to 33%, and sampling revealed the continued presence of microbes. Following extensive cleaning, microbial levels decreased, and symptom scores declined to 4%. Variability in peak flow rate dropped to 15%. The intervention and time-series components of this study added power to the experimental design by enabling study participants to serve as their own controls, thereby controlling many potentially confounding factors. The main study deficiency was the lack of a robust and objective indicator to support the reports of symptoms involving nonrespiratory systems. A health assessment was conducted by the National Institute of Occupational Safety and Health after workers in a water-damaged office building complained of health effects [144]. Moderate to high levels of Aspergillus sp., Penicillium sp., and bacteria were found in bulk and surface samples. Stachybotrys sp. were identified in only 5% of samples cultured in Czapek agar. The prevalence of multiple-system symptoms, primarily neurologic and respiratory, was significantly higher prior to removal from the building than 6 months after removal. The lack of objective indicators of effect in these studies continued to prevent firm establishment of an association between indoor microbial exposure and adverse health effects.

An investigation of chronic respiratory and flu-like symptoms among construction workers at the Denver International Airport also lacked a robust, objective indicator of illness [57]. The rate of cases, defined as having at least two lower respiratory complaints and one systemic symptom, was 34% among randomly selected workers and 2% in controls who had not worked at the airport. Length of employment was a statistically significant risk factor for illness. An exposure assessment identified alkaline dust in the work environment of cases, and widely distributed airborne Penicillium in the airport. In addition to the lack of an objective indicator for a systemic effect, the ability to draw definitive conclusions from the study was hampered by the lack of exclusion for potentially confounding factors, and the unavailability of information about alkaline dust and Penicillium exposures among controls.

Several other cross-sectional studies supported the hypothesis that exposure to microbes in excessively damp buildings is associated with a multiple-system syndrome, but lacked the objective indication of effect in a nonpulmonary system, and the experimental-design power needed to reach the level of scientific certainty. A British study reported positive associations between SBS symptom prevalence rates and the levels of viable airborne fungi and bacteria within office buildings [74]. A Swedish study surveyed occupants in more than 14,000 residences in 609 multifamily buildings, and yielded a 77% response rate [56]. Over 28% of respondents reported at least one of four signs of dampness, and all dampness indicators were associated with significantly increased rates of multiple-system symptoms after statistical adjustments for several socio-demographic factors. In dwellings with all four dampness indicators, highly elevated odds ratios were reported for ocular, nasal, throat, and dermal symptoms, as well as for cough, headache, and tiredness. Results from a one-year study of 98 workers in four Bostonian office buildings were recently reported [32]. Concurrent surface sampling and questionnaire administration at 6-week intervals positively associated total fungal concentrations in floor or chair dust with reports of eye irritation, a group of nonspecific symptoms, asthma, and upper respiratory symptoms. However, fungal concentrations were also associated with low job satisfaction, office crowding, and lack of office cleanliness. Another cross-sectional study observed relationships between SBS symptoms and prior physician diagnoses of dust or mold allergy [104]. A statistical cluster analysis defined problematic areas in which potentially etiologic microbes were identified.

Although these studies associated indoor microbial contamination with a multiple-system syndrome, scientific certainty required that several study limitations be overcome. First, potential study participants should be screened for exclusion due to confounding factors using a standard tool to assess medical and lifestyle history, as well as occupational, residential, and avocational exposures to toxic substances. Second, the study should include a comprehensive medical evaluation and differential diagnosis techniques to identify illnesses unrelated to building exposure, but capable of causing SBS symptoms. Third, the potential for bias and imprecision in self-reported symptoms, particularly in self-administered questionnaires, must be reduced. An interview of study participants by a single, highly trained and practiced medical researcher using a standard set of questions designed to assess symptoms and illness duration is needed to reduce bias and increase precision. Fourth, because indoor exposures to microbes are generally acknowledged to have the potential to affect the respiratory system, but are only hypothesized to affect other systems, a robust indicator of effect in another system is needed. Fifth, better control of unidentified but potentially confounding factors in study participants is needed. One approach is to use an experimental design that allows participants to serve as their own controls, as in the time series with intervention design used by Ebbehoj et al. [53] and described above. Sixth, a still more powerful experimental design, often used in animal studies, would include illness remission during intervention, followed by illness reacquisition upon reexposure without therapy. This approach has not been feasible due to the lack of an effective and rapid therapeutic intervention. Use of these methodological and design elements would improve the ability of a study to firmly associate SBS with exposure to biologic agents.

Another critical methodological consideration is exposure assessment. Microbial growth on surfaces in WDBs is often a complex mixture of fungal and bacterial species. The studies reviewed above demonstrated a wide variety of predominant organisms in WDBs. Although many species were known to be toxigenic, it is generally acknowledged that a comprehensive list of bioactive components, including mycotoxins, endotoxins, and antigens, does not exist at this time. It is impossible, therefore, to quantify all bioactive components on building surfaces, in building air, or in biological tissue. Air sampling is particularly problematic because the release of spores to air is irregular, as discussed above [111]. The relationship between exposure to mixtures and health effects is obscured by the potential for synergistic interactions between bioactive components, such as the synergistic effect of Streptomyces californicus and S. chartarum or fungal toxins on the production of proinflammatory cytokines [85]. Because of these limitations, it is inappropriate to conclude that exposure levels to any single species or component, or even groups, is too low for exposure to that environment to cause SBS symptoms in building occupants. In many studies of illness in occupants of WDBs, an appropriate hypothesis is that chronic exposure to the water-damaged environment is associated with illness. Exposure assessment should include visual observation of the environment, and characterization of water-damaged surfaces and microbial amplification. Identification of organisms and components should be done to the extent practical. Confirmation of the hypothesis should be based on the experimental design elements discussed above. Animal studies will be needed to test additional hypotheses concerning microbial causation of illness, and to assess the relative potency of individual organisms, components, and mixtures.

Pilot data indicating that the paradigm of biotoxin-associated illness may generalize to SBS associated with WDBs [78] provided impetus for the current study. Both acute and chronic biotoxin-associated illnesses were previously ascribed to cases diagnosed with Possible Estuary Associated Syndrom (PEAS; [135], [137]), a condition with onset following exposure to estuaries where the toxigenic dinoflagellates, Pfiesteria sp. [29], were associated with massive fish kills [21] and human illness [68], [71]. The cases were characterized by multiple-system symptoms, a deficit in visual contrast sensitivity (VCS) indicating neurologic impairment [81], elevated levels of proinflammatory cytokines, and the absence of alternative explanations of illness [135], [137]. Cases were treated with cholestyramine (CSM; Questran), a nonabsorbable polymer with anion exchange capacity, known to eliminate a variety of toxins and drugs by interrupting their enterohepatic recirculation with bile [8], [94]. Symptoms resolved as VCS normalized during 2 weeks of CSM therapy in both acute and chronic cases [135], [137]. A double-blinded, placebo-controlled, crossover clinical trial demonstrated that symptom resolution and VCS recovery occurred only during CSM therapy [135]. PEAS cases showed no relapse without reexposed to Pfiesteria-inhabited estuaries. When reexposed, recovery again promptly followed CSM therapy [137]. VCS measurements provided an objective indication of neurologic function in illness acquisition and recovery in this condition otherwise characterized only by nonspecific symptoms. The efficacy of CSM therapy supported the hypothesis of biotoxin-induced illness. Pilot data collected from SBS cases occupying WDBs demonstrated relationships between multiple-system symptoms, VCS alterations, and response to CSM therapy similar to those observed in PEAS cases [78], indicating that biotoxin-associated illness may underlie this condition.

The current study addressed the general hypothesis that SBS is associated with exposure to WDBs. Specific hypotheses concerning symptoms, VCS, and hormones were tested to assess the validity of the general hypothesis. The cross-sectional study design included environmental assessments, medical and laboratory evaluations of participants' health status at five time points, and the interventions of CSM therapy, removal from exposure and reexposure. The study design and procedures were selected to address many of the limitations identified in previous studies.