Fungal exposure of children at homes and schools: a health perspective

Indoor exposure levels of bacteria and fungi in residences, schools, and offices in China: A systematic review

Microbes in buildings have attracted extensive attention from both the research community and the general public due to their close relationship with human health. However, there still lacks comprehensive information on the indoor exposure level of microbes in China. This study systematically reviews exposure levels, the community structures, and the impact factors of airborne bacteria and fungi in residences, schools, and offices in China. We reviewed the major literature databases between 1980 and 2019 and selected 55 original studies based on a set of criteria. Results show that the concentration of indoor bacteria varies from 72.5 to 7500 CFU/m³ , with a median value of 1000 CFU/m³ , and the concentration of fungi varies from 12 to 9730 CFU/m³ , with a median value of 526 CFU/m³ . The concentration level of microbes varies in different climate zones, with higher bacterial concentrations in the severe cold zone, and higher fungal concentrations in the hot summer and warm winter zone. Among different buildings, classrooms have the highest average bacteria and fungi levels. This review reveals that a unified assessment system based on health effects is needed for evaluating the exposure levels of bacteria and fungi.

Current asthma in schoolchildren is related to fungal spores in classrooms

BACKGROUND

The presence of visible mold in households is associated with asthma. However, the role of "classroom fungus" in the development of childhood asthma, as well as the fungal species that may lead to asthma, remains controversial. This nationwide school survey was conducted to investigate the correlation between fungal spores in classrooms and asthma in schoolchildren.

METHODS

From April to May 2011, a cross-sectional survey was conducted to assess allergic/asthmatic conditions in schoolchildren aged 6 to 15 years old in 44 schools across Taiwan. Personal histories and current asthmatic conditions were collected using a modified International Study of Asthma and Allergies in Childhood questionnaire. Fungal spores in classroom were collected using a Burkard Personal Air Sampler and counted under light microscopy. Three-level hierarchical modeling was used to determine the complex correlation between fungal spores in classrooms and childhood asthma.

RESULTS

The survey was completed by 6,346 out of 7,154 parents (88.7%). The prevalences of physician-diagnosed asthma, current asthma, and asthma with symptoms reduced on holidays or weekends (ASROH) were 11.7%, 7.5%, and 3.1%, respectively. The geometric mean spore concentrations of total fungi, Aspergillus/Penicillium, and basidiospores were 2,181, 49, and 318 spores/m3. Aspergillus/Penicillium and basidiospores were significantly correlated with current asthma and ASROH after adjusting for personal and school factors. Of those with current asthma, 41% reported relief of symptoms during weekends.

CONCLUSIONS

Classroom Aspergillus/Penicillium and basidiospores are significantly associated with childhood asthma and ASROH. Government health policy should explore environmental interventions for the elimination of fungal spores in classrooms to reduce the prevalence of childhood asthma.

Endotoxin, ergosterol, fungal DNA and allergens in dust from schools in Johor Bahru, Malaysia- associations with asthma and respiratory infections in pupils

There are few studies on associations between respiratory health and allergens, fungal and bacterial compounds in schools in tropical countries. The aim was to study associations between respiratory symptoms in pupils and ethnicity, chemical microbial markers, allergens and fungal DNA in settled dust in schools in Malaysia. Totally 462 pupils (96%) from 8 randomly selected secondary schools in Johor Bahru, Malaysia, participated. Dust was vacuumed from 32 classrooms and analysed for levels of different types of endotoxin as 3-hydroxy fatty acids (3-OH), muramic acid, ergosterol, allergens and five fungal DNA sequences. Multiple logistic regression was applied. Totally 13.1% pupils reported doctor’s diagnosed asthma, 10.3% wheeze and 21.1% pollen or pet allergy. Indian and Chinese children had less atopy and asthma than Malay. Carbon dioxide levels were low (380–690 ppm). No cat (Fel d1), dog (Can f 1) or horse allergens (Ecu cx) were detected. The levels of Bloomia tropicalis (Blo t), house dust mite allergens (Der p 1, Der f 1, Der m 1) and cockroach allergens (Per a 1 and Bla g 1) were low. There were positive associations between levels of Aspergillus versicolor DNA and daytime breathlessness, between C14 3-OH and respiratory infections and between ergosterol and doctors diagnosed asthma. There were negative (protective) associations between levels of C10 3-OH and wheeze, between C16 3-OH and day time and night time breathlessness, between cockroach allergens and doctors diagnosed asthma. Moreover there were negative associations between amount of fine dust, total endotoxin (LPS) and respiratory infections. In conclusion, endotoxin at school seems to be mainly protective for respiratory illness but different types of endotoxin could have different effects. Fungal contamination measured as ergosterol and Aspergillus versicolor DNA can be risk factors for respiratory illness. The ethnical differences for atopy and asthma deserve further attention.

Coarse and fine culturable fungal air concentrations in urban and rural homes in Egypt

The main objective of the present study was to assess culturable airborne fungal concentrations, and types in different seasons. Two-stage viable impactor samplers were used with malt extract agar medium as the collection media. Culturable airborne fungal concentrations were collected indoors and outdoors of 43 homes in urban and rural environments from November 2008 to October 2009 in Egypt. Fungal concentrations were significantly higher in the rural environment than the urban environment. The median indoor and outdoor total fungal concentrations were 608 and 675 CFU/m3 in the urban environment and 1,932 and 1,872 CFU/m3 in the rural environment, respectively. The greatest concentrations were found in the autumn and spring season. Indoor and outdoor concentrations were significantly correlated (P < 0.001). The highest concentrations were observed in the fungal size range of <8 µm (fine fraction). The indoor/outdoor (I/O) ratios were not statistically different between seasons. Alternaria, Aspergillus, Cladosporium, Penicillium and yeasts were the predominant genera indoors and outdoors, and the abundance of genera varied by season and region. This study is of a potential interest as little reported research on the indoor fungal air quality from Egypt.

Indoor fungal concentration in the homes of allergic/asthmatic children in Delhi, India

Allergy to fungi has been linked to a wide range of illnesses, including rhinitis and asthma. Therefore, exposure to fungi in home environment is an important factor for fungal allergy. The present study was aimed to investigate types of airborne fungi inside and outside the homes of asthmatic children and control subjects (nonasthmatic children). The dominant fungi were evaluated for their quantitative distribution and seasonal variation. The air samples were collected from indoors and immediate outdoors of 77 selected homes of children suffering from bronchial asthma/allergic rhinitis using Andersen volumetric air sampler. The isolated fungal genera/species were identified using reference literature, and statistical analysis of the dominant fungi was performed to study the difference in fungal concentration between indoor and immediate outdoor sites as well as in between different seasons. A total of 4423 air samples were collected from two indoor and immediate outdoor sites in a 1-year survey of 77 homes. This resulted in the isolation of an average of 110,091 and 107,070 fungal colonies per metric cube of air from indoor and outdoor sites, respectively. A total of 68 different molds were identified. Different species of Aspergillus, Alternaria, Cladosporium, and Penicillium were found to be the most prevalent fungi in Delhi homes, which constituted 88.6% of the total colonies indoors. Highest concentration was registered in autumn and winter months. Total as well as dominant fungi displayed statistically significant differences among the four seasons (p < 0.001). The largest number of isolations were the species of Aspergillus (>40% to total colony-forming units in indoors as well as outdoors) followed by Cladosporium spp. Annual concentration of Aspergillus spp. was significantly higher (p < 0.05) inside the homes when compared with outdoors. Most of the fungi also occurred at a significantly higher (p < 0.001) rate inside the homes when compared with immediate outdoors. Asthmatic children in Delhi are exposed to a substantial concentration of mold inside their homes as well as immediate outdoor air. The considerable seasonal distributions of fungi provide valuable data for investigation of the role of fungal exposure as a risk for respiratory disorders among patients suffering from allergy or asthma in Delhi.

A dose-dependent relationship between the severity of visible mold growth and IgE levels of pre-school-aged resident children in Taiwan

To demonstrate a dose-dependent relationship between severity of indoor visible mold growth and serum total IgE levels of resident children. A total of 97 children (4-7 years old) identified from previously established birth-cohort, with information pertaining to indoor environmental conditions after child's birth, were successfully recruited while sera were concurrently collected for total IgE and specific IgE analysis during clinical visits. Severity of visible mold growth at homes was scaled into three levels accordingly. A statistically significant dose-dependent relationship was found between severity of indoor visible mold growth and total serum IgE levels. The trend sustains after the model was adjusted for resident child's age, gender, pet-keeping history, number of siblings, atopic history of parents, presence of incense burning, and environmental tobacco smoking (ETS) at home. Further analysis of specific IgE to commonly examined fungal allergens did not substantiate the correlation. Rather, resident child's specific IgE to mite allergens, although without statistical significance, seemed to better associate with the ranked severity of indoor mold growth in this study. An adjuvant role of fungal exposure to enhance sensitization in indoor environment is therefore suggested in Taiwanese population with high prevalence of building dampness.

PRACTICAL IMPLICATIONS

The presence of indoor visible mold growth, potentially resulting in fungal exposure, was not associated directly with changing biomarker levels of allergic response in resident children, rather playing an adjuvant role to enhance sensitization. On the other hand, other allergens, such as mite allergen examined in this study, appeared to support a more plausible etiology for directly triggering the ultimate allergic symptoms and diseases of interest. Evidence as such may derive different priority-setting when designing preventive measures for managing indoor air quality.

Indoor airborne fungi and wheeze in the first year of life among a cohort of infants at risk for asthma

In studies worldwide, respiratory outcomes such as cough, wheeze and asthma have been consistently linked to mold exposure. Young children spend most of their time indoors and may be particularly vulnerable. We evaluated the associations between exposure to airborne fungal levels and episodes of wheezing in a cohort of 103 infants at risk for asthma (due to maternal history of asthma), living primarily in low-income urban settings. Using a new protocol that facilitates identification of rare and slow-growing fungi, we measured the type and concentration of cultured fungi in home air samples taken early in the infant's first year of life. We also inspected the homes for visible mold, water damage and other housing and environmental conditions. All homes had measurable indoor airborne fungi and 73%, had some sign of mold, water damage, dampness or a musty odor. One or more episodes of wheeze during the first year of life were observed in 38% of infants. Multiple logistic regression showed high indoor levels of Penicillium were a significant risk factor for wheeze (OR 6.18; 95% CI: 1.34-28.46) in the first year of life after controlling for season of sampling, smoking, endotoxin levels, day care attendance and confounders. Acrodontium, a rarely reported fungal genus, was detected in 18% of study homes, and was associated with wheeze in unadjusted models (OR 2.75; 95% CI 0.99-7.61), but not after adjustment for confounders. Total fungal levels, visually observed mold, dampness, water damage or musty odors were not significantly associated with wheeze.

Airborne fungi in child day care centers in Edirne City, Turkey

The purpose of this study was to determine the concentration, in terms of monthly and seasonal distribution and in relation to meteorological factors, of indoor and outdoor microfungi at selected sites in several child day care centers in the city of Edirne, Turkey. Samples were collected at one month intervals over a period of 12 months between January-December 2004, by exposing petri plates containing Peptone Dextrose Agar with Rose-Bengal and Streptomycin medium to the air for 10-15 min. A total of 2,071 microfungal colonies were counted on 192 petri plates. Thirty microfungal genera (Acremonium, Alternaria, Arthrinium, Aspergillus, Bahusakala, Beauveria, Ceuthospora, Chaetomium, Cladosporium, Curvularia, Drechslera, Epicoccum, Eurotium, Fusarium, Mycotypha, Myrotechium, Paecilomyces, Penicillium, Pestalotiopsis, Phoma, Ramichloridium, Rhizopus, Scopulariopsis, Stachybotrys, Stemphylium, Torula, Trichoderma, Trichothecium, Ulocladium, Verticillium) and 75 microfungal species were isolated from the air indoor and outdoor of the day care centers. The dominant microfungal genera were Cladosporium, Penicillium and Alternaria (44.11%, 18.94%, 14.67% of the total respectively), while the genus with the most species richness was Penicillium (26 species). Alternaria, Cladosporium, Penicillium and non-sporulating microfungi were found every month. Cladosporium was the dominant genus in both indoor and outdoor air. Although the predominant genus was the same in both indoor and outdoor air, Cladosporium was followed by Penicillium, Alternaria and Aspergillus genera in indoor air and by Alternaria, Penicillium and Aspergillus genera in outdoor air. While a positive correlation was found between the concentration of monthly outdoor microfungi and monthly average temperature, a negative correlation was found between the concentration of monthly outdoor microfungi and monthly average wind velocity. Also, some relationships were found between the monthly concentrations of the most predominant microfungal genera (Cladosporium, Penicillium and Alternaria) and various meteorological factors.

Effect of indoor mold concentrations on daily symptom severity of children with asthma and/or rhinitis monosensitized to molds

Little is known about the contribution of indoor molds to the symptoms of asthma and/or rhinitis in children monosensitized to molds. We aimed to investigate the effect of indoor mold spore concentrations on daily symptoms of asthma and/or rhinitis in children monosensitized to molds. Nineteen children with asthma and/or rhinitis sensitized only to molds recorded their daily symptoms and peak expiratory flow (PEF) values to the diaries, from February 2005 to January 2006. In this study period, indoor mold concentrations were measured monthly from the living rooms/bedrooms. The median indoor mold concentration was 37.5 CFU/m(3). Most commonly recovered indoor molds were Cladosporium (26.4%), Penicillium (24.7%), and Aspergillus (7%). Significant correlation was not found between indoor mold concentrations and daily rhinitis score (r = -0.021, p = 0.932), daily asthma score (r = 0.155, p = 0.554), daily morning PEF (r = -0.056, p = 0.475), and evening PEF (r = -0.057, p = 0.471). The effect of indoor molds is not evident on the symptoms of our patients with asthma and/or rhinitis monosensitized to molds.

A comparative study of asthma, pollen, cat and dog allergy among pupils and allergen levels in schools in Taiyuan city, China, and Uppsala, Sweden

We compared the school environment, asthma and allergy in 10 schools in Taiyuan, China, with eight schools in Uppsala, Sweden. In total 2193 pupils (mean age 13 years) participated. Chinese pupils had more respiratory symptoms, particularly daytime breathlessness after exercise (29.8% vs. 7.1%; P < 0.001), while cat allergy (1.2% vs. 6.6%; P < 0.001) and dog allergy (1.3% vs. 4.0%; P < 0.01) was less common. Cumulative incidence of asthma (1.8% vs. 9.5%; P < 0.001) and doctor's diagnosed asthma (1.2% vs. 9.0%; P < 0.001) were less common in China, indicating an under-diagnosis of asthma. Chinese classrooms were colder (mean 14.7 vs. 21.4 degrees C), more humid (mean 42% vs. 31% RH) and had higher CO2-levels (mean 2211 vs. 761 ppm). Levels of cat (Fel d1), dog (Can f1) allergens were low in settled dust from China (< 200 ng/g dust), but high in airborne dust on Petri-dishes (GM 16.8 ng/m2/day for Fel d1 and 17.7 for Can f1). The Swedish settled dust contained cat, dog and horse allergens in high levels (median 1300 ng/g, 1650 ng/g, 1250 U/g dust, respectively). In conclusion, there were large differences in the school environment, and in respiratory symptom and allergy. Allergen measurements in settled dust only may largely underestimate the classroom exposure. Practical Implications There is a need to improve the school environment, both in China and Sweden. The Swedish schools contained high levels of cat, dog and horse allergens and more amounts of open shelves and textiles that can accumulate dust and allergens. The air measurements indicated that Chinese schools may contain significant amounts of cat and dog allergen, and analysis of settled dust only may not reflect the true allergen exposure. Since the Chinese schools had no mechanical ventilation, they could not fulfill the ventilation standard in winter, and hence there is a need for improving the ventilation. The great discrepancy between respiratory symptoms and reports on asthma, and the high prevalence of attacks of breathlessness without wheeze, may have implication for future questionnaire studies on asthma in China.

Current asthma and respiratory symptoms among pupils in Shanghai, China: influence of building ventilation, nitrogen dioxide, ozone, and formaldehyde in classrooms

We investigated 10 naturally ventilated schools in Shanghai, in winter. Pupils (13-14 years) in 30 classes received a questionnaire, 1414 participated (99%). Classroom temperatures were 13-21 degrees C (mean 17 degrees C), relative air humidity was 36-82% (mean 56%). The air exchange rate was 2.9-29.4 ac/h (mean 9.1), because of window opening. Mean CO2 exceeded 1000 ppm in 45% of the classrooms. NO2 levels were 33-85 microg/m3 indoors, and 45-80 microg/m3 outdoors. Ozone were 1-9 microg/m3 indoors and 17-28 microg/m3 outdoors. In total, 8.9% had doctors' diagnosed asthma, 3.1% wheeze, 23.0% daytime breathlessness, 2.4% current asthma, and 2.3% asthma medication. Multiple logistic regression was applied. Observed indoor molds was associated with asthma attacks [odds ratio (OR) = 2.40: P < 0.05]. Indoor temperature was associated with daytime breathlessness (OR = 1.26 for 1 C; P < 0.001), and indoor CO2 with current asthma (OR = 1.18 for 100 ppm; P < 0.01) and asthma medication (OR = 1.15 for 100 ppm; P < 0.05). Indoor NO2 was associated with current asthma (OR = 1.51 for 10 microg/m3; P < 0.01) and asthma medication (OR = 1.45 for 10 microg/m3; P < 0.01). Outdoor NO2 was associated with current asthma (OR = 1.44 for 10 microg/m3; P < 0.05). Indoor and outdoor ozone was negatively associated with daytime breathlessness. In conclusion, asthma symptoms among pupils in Shanghai can be influenced by lack of ventilation and outdoor air pollution from traffic. Practical Implications Most urban schools in Asia are naturally ventilated buildings, often situated in areas with heavy ambient air pollution from industry or traffic. The classes are large, and window opening is the only way to remove indoor pollutants, but this results in increased exposure to outdoor air pollution. There is a clear need to improve the indoor environment in these schools. Building dampness and indoor mold growth should be avoided, and the concept of mechanical ventilation should be introduced. City planning aiming to situate new schools away from roads with heavy traffic should be considered.

Alterations in health examination items and skin symptoms from exposure to ultra-low humidity

OBJECTIVES

Several lines of evidence have shown that insufficient humidity could result in health problems but no studies have been performed in ultra-low humidity (ULH) environments. The aims of this study are to investigate the health examination items alterations and skin symptoms of workers exposed to ULH environment based on a longitudinal study design.

METHODS

Twelve male ULH (RH = 1.5%) workers and 12 age-sex-matched reference workers were selected. The examination items in blood and urine as well as the skin problems were compared between ULH workers and controls, and between ULH workers in 2000 and 2003. Biochemistry analysis of blood and urine were implemented from annual health examinations. Information on skin symptoms and diseases were obtained from a structured questionnaire in 2000 and 2003.

RESULTS

The alterations in mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and total cholesterol in blood analysis and only sediment-WBC in urine analysis were found significantly different in 2000. These changes were almost fully recovered in 2003 although a consistently significant elevation in the urine specific gravity was found during the 3-year follow-up period. Skin disorders, however, showed an earlier elevated itching symptom in lower limb and pretibial that developed to physician-diagnosed contact dermatitis.

CONCLUSIONS

Long-term ULH exposure could cause progressive pathological changes in the skin and urine concentration elevation. Because low humidity condition occurs frequently in air-conditioned buildings, the findings of this study suggest the population long-term exposed to low humidity should be cautious about health manifestations living in a low humidity environment. While the indoor environment is equipped with an air-conditioner, continuous monitoring on the humidity is recommended.

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

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.

Dustborne and airborne fungal propagules represent a different spectrum of fungi with differing relations to home characteristics

BACKGROUND

Exposure to fungi is often assessed by culturing floor dust or air samples. Our objective was to evaluate the relationships between dustborne and airborne fungi and to identify factors that modify these relationships.

METHODS

From November 1994 to September 1996 sequential duplicate 45-l air samples were collected in bedrooms of 496 homes in the Boston area, using a Burkard culture plate sampler. After air sampling, bedroom floors were sampled with a vacuum cleaner that was modified to collect dust in a cellulose extraction thimble. Dust was sieved, and the fine dust was dilution-plated onto DG-18 media.

RESULTS

Concentrations of total culturable fungi per gram of bedroom-floor dust were correlated weakly, but significantly, with those of indoor air (r = 0.13, P < 0.05). Concentrations of some individual taxa in the dust and indoor air were also weakly associated. Adjusting for the concentrations of fungi in outdoor air, dustborne fungal concentrations were positively associated with those in indoor air for the taxa Cladosporium and Penicillium, but not for total fungi. The indoor air fungal levels were often predicted by different covariates to those predicting fungal levels in dust. The type of housing (house or apartment) and the presence of carpeting were often predictive factors for dust fungi. In contrast, outdoor fungal levels were often predictive of the indoor air fungal levels.

CONCLUSIONS

Because our data do not indicate a strong overall relationship between culturable fungi in dust and indoor air, the results from these two methods (dust and air sampling) likely represent different types of potential fungal exposures to residents. It may be essential to collect both air and dust samples, as well as information on housing characteristics, as indicators for fungal exposure.

An update on pollen and fungal spore aerobiology

Changes in climate are altering pollen distribution. Predictive modeling can be used to forecast long- and short-term changes in pollen concentrations. Increasing evidence confirms the presence of pollen allergens on small, respirable particles in the air, explaining the occurrence of pollen-season increases in asthma. Like pollens, aboveground indoor fungal aerosols primarily reflect outdoor concentrations. Basement spore concentrations might be higher and reflective of local sources. Fungal presence in the indoor or outdoor air can be monitored on an area basis or with personal monitors. The samples can be analyzed by means of microscopy, culture, DNA probes, HPLC, or immunodetection. Total fungal biomass can be estimated on the basis of measurements of ergosterol or glucan in environmental samples. Unfortunately, there are no generally accepted standards for interpretation of fungal levels in indoor or outdoor air. At present, the best approach to indoor fungal control is moisture control in the indoor environment. This will essentially prevent fungal growth, except from extraordinary events.