Next‐generation DNA sequencing reveals that low fungal diversity in house dust is associated with childhood asthma development

Dampness and visible mold in homes are associated with asthma development, but causal mechanisms remain unclear. The goal of this research was to explore associations among measured dampness, fungal exposure, and childhood asthma development without the bias of culture‐based microbial analysis. In the low‐income, Latino CHAMACOS birth cohort, house dust was collected at age 12 months, and asthma status was determined at age 7 years. The current analysis included 13 asthma cases and 28 controls. Next‐generation DNA sequencing methods quantified fungal taxa and diversity. Lower fungal diversity (number of fungal operational taxonomic units) was significantly associated with increased risk of asthma development: unadjusted odds ratio (OR) 4.80 (95% confidence interval (CI) 1.04–22.1). Control for potential confounders strengthened this relationship. Decreased diversity within the genus Cryptococcus was significantly associated with increased asthma risk (OR 21.0, 95% CI 2.16–204). No fungal taxon (species, genus, class) was significantly positively associated with asthma development, and one was significantly negatively associated. Elevated moisture was associated with increased fungal diversity, and moisture/mold indicators were associated with four fungal taxa. Next‐generation DNA sequencing provided comprehensive estimates of fungal identity and diversity, demonstrating significant associations between low fungal diversity and childhood asthma development in this community.     

Assessing allergenic fungi in house dust by floor wipe sampling and quantitative PCR

Abstract In the present study, we modified an existing surface wipe sampling method for lead and other heavy metals to create a protocol to collect fungi in floor dust followed by real‐time quantitative PCR (qPCR)‐based detection. We desired minimal inconvenience for participants in residential indoor environmental quality and health studies. Accuracy, precision, and method detection limits (MDLs) were investigated. Overall, MDLs ranged from 0.6 to 25 cell/cm² on sampled floors. Overall measurement precisions expressed as the coefficient of variation because of sample processing and qPCR ranged 6–63%. Median and maximum fungal concentrations in house dust in study homes in Visalia, Tulare County, California, were 110 and 2500 cell/cm², respectively, with universal fungal primers (allergenic and nonallergenic species). The field study indicated samplings in multiple seasons were necessary to characterize representative whole‐year fungal concentrations in residential microenvironments. This was because significant temporal variations were observed within study homes. Combined field and laboratory results suggested this modified new wipe sampling method, in conjunction with growth‐independent qPCR, shows potential to improve human exposure and health studies for fungal pathogens and allergens in dust in homes of susceptible, vulnerable population subgroups.

Practical Implications

Fungi are ubiquitous in indoor and outdoor environments, and many fungi are known to cause allergic reactions and exacerbate asthma attacks. This study established—by modifying an existing—a wipe sampling method to collect fungi in floor dust followed by real‐time quantitative PCR (qPCR)‐based detection methodologies. Results from this combined laboratory and field assessment suggested the methodology’s potential to inform larger human exposure studies for fungal pathogens and allergens in house dust as well as epidemiologic studies of children with asthma and older adults with chronic respiratory diseases.

     

PVC flooring at home and development of asthma among young children in Sweden,a 10‐year follow‐up

The incidence of asthma and allergy has increased throughout the developed world over the past decades. During the same period of time, the use of industrial chemicals such as phthalates, commonly used as plasticizers in polyvinylchloride (PVC) flooring material, has increased. The aim of this study was to investigate whether PVC flooring in the home of children in the age of 1–5 years is associated with the development of asthma in 5‐ and 10‐year follow‐up investigations (n = 3228). Dampness in Buildings and Health Study (DBH Study) commenced in 2000 in Värmland, Sweden. The current analyses included subjects who answered all baseline and follow‐up questionnaires. Logistic regression analyses were applied to questionnaire results. Children who had PVC floorings in the bedroom at baseline were more likely to develop doctor‐diagnosed asthma during the following 10‐year period when compared with children living without. There were indications that PVC flooring in the parents' bedrooms was strongly associated with the new cases of doctor‐diagnosed asthma when compared with child′s bedroom. Our results suggest that PVC flooring exposure during pregnancy could be a critical period in the development of asthma in children at a later time; prenatal exposure and measurements of phthalate metabolites should be included in the future.     

Exposure to organophosphate and polybrominated diphenyl ether flame retardants via indoor dust and childhood asthma

Although the ubiquitous detection of polybrominated diphenyl ether (PBDE) and organophosphate flame retardants (PFRs) in indoor dust has raised health concerns, only very few epidemiological studies have assessed their impact on human health. Inhalation of dust is one of the exposure routes of FRs, especially in children and can be hazardous for the respiratory health. Moreover, PFRs are structurally similar to organophosphate pesticides, which have been associated with allergic asthma. Thus, we investigated whether the concentrations of PFRs and PBDEs in indoor dust are associated with the development of childhood asthma. We selected 110 children who developed asthma at 4 or at 8 years old and 110 matched controls from a large prospective birth cohort (BAMSE – Barn, Allergy, Milieu Stockholm Epidemiology). We analyzed the concentrations of 7 PFRs and 21 PBDEs in dust collected around 2 months after birth from the mother's mattress. The abundance rank in dust was as follows: TBOEP?TPHP>mmp‐TMPP>EHDPHP~TDCIPP>TCEP~TCIPP~BDE‐209?BDE‐99>BDE‐47>BDE‐153>BDE‐183>BDE‐100. There was no positive association between the FRs in mattress dust and the development of childhood asthma. In contrast, dust collected from mattresses of the mothers of children who would develop asthma contained significant lower levels of TPHP and mmp‐TMPP. This study provides data on a wide range of PFRs and PBDEs in dust samples and development of asthma in children.     

Indoor residential chemical emissions as risk factors for respiratory and allergic effects in children: a review

Most research into effects of residential exposures on respiratory health has focused on allergens, moisture/mold, endotoxin, or combustion products. A growing body of research from outside the US; however, has associated chemical emissions from common indoor materials with risk of asthma, allergies, and pulmonary infections. This review summarizes 21 studies in the epidemiologic literature on associations between indoor residential chemical emissions, or emission-related materials or activities, and respiratory health or allergy in infants or children. Associations, some strong, were reported between many risk factors and respiratory or allergic effects. Risk factors identified most frequently included formaldehyde or particleboard, phthalates or plastic materials, and recent painting. Findings for other risk factors, such as aromatic and aliphatic chemical compounds, were limited but suggestive. Elevated risks were also reported for renovation and cleaning activities, new furniture, and carpets or textile wallpaper. Reviewed studies were entirely observational, limited in size, and variable in quality, and specific risk factors identified may only be indicators for correlated, truly causal exposures. Nevertheless, overall evidence suggests a new class of residential risk factors for adverse respiratory effects, ubiquitous in modern residences, and distinct from those currently recognized. It is important to confirm and quantify any risks, to motivate and guide necessary preventive actions. PRACTICAL IMPLICATIONS: Composite wood materials that emit formaldehyde, flexible plastics that emit plasticizers, and new paint have all been associated with increased risks of respiratory and allergic health effects in children. Although causal links have not been documented, and other correlated indoor-related exposures may ultimately be implicated, these findings nevertheless point to a new class of little recognized indoor risk factors for allergic and respiratory disease, distinct from the current set of indoor risk factors. The available evidence thus raises initial questions about many common residential practices: for instance, using pressed wood furnishings in children's bedrooms, repainting infant nurseries, and encasing mattresses and pillows with vinyl for asthmatic children. The findings summarized here suggest a need for substantially increased research to replicate these findings, identify causal factors, and validate preventive strategies.     

Phosphorus flame retardants in indoor dust and their relation to asthma and allergies of inhabitants

Organophosphate esters are used as additives in flame retardants and plasticizers, and they are ubiquitous in the indoor environment. Phosphorus flame retardants (PFRs) are present in residential dust, but few epidemiological studies have assessed their impact on human health. We measured the levels of 11 PFRs in indoor floor dust and multi‐surface dust in 182 single‐family dwellings in Japan. We evaluated their correlations with asthma and allergies of the inhabitants. Tris(2‐butoxyethyl) phosphate was detected in all samples (median value: 580 μg/g in floor dust, 111 μg/g in multi‐surface dust). Tris(2‐chloro‐iso‐propyl) phosphate (TCIPP) was detected at 8.69 μg/g in floor dust and 25.8 μg/g in multi‐surface dust. After adjustment for potential confounders, significant associations were found between the prevalence of atopic dermatitis and the presence of TCIPP and tris(1,3‐dichloro‐2‐propyl) phosphate in floor dust [per log₁₀‐unit, odds ratio (OR): 2.43 and 1.84, respectively]. Tributyl phosphate was significantly associated with the prevalence of asthma (OR: 2.85 in floor dust, 5.34 in multi‐surface dust) and allergic rhinitis (OR: 2.55 in multi‐surface dust). PFR levels in Japan were high compared with values reported previously for Europe, Asia‐Pacific, and the USA. Higher levels of PFRs in house dust were related to the inhabitants' health status.     

Determining source strength of semivolatile organic compounds using measured concentrations in indoor dust

Consumer products and building materials emit a number of semivolatile organic compounds (SVOCs) in the indoor environment. Because indoor SVOCs accumulate in dust, we explore the use of dust to determine source strength and report here on analysis of dust samples collected in 30 US homes for six phthalates, four personal care product ingredients, and five flame retardants. We then use a fugacity‐based indoor mass balance model to estimate the whole‐house emission rates of SVOCs that would account for the measured dust concentrations. Di‐2‐ethylhexyl phthalate (DEHP) and di‐iso‐nonyl phthalate (DiNP) were the most abundant compounds in these dust samples. On the other hand, the estimated emission rate of diethyl phthalate is the largest among phthalates, although its dust concentration is over two orders of magnitude smaller than DEHP and DiNP. The magnitude of the estimated emission rate that corresponds to the measured dust concentration is found to be inversely correlated with the vapor pressure of the compound, indicating that dust concentrations alone cannot be used to determine which compounds have the greatest emission rates. The combined dust‐assay modeling approach shows promise for estimating indoor emission rates for SVOCs.     

Respiratory symptoms, asthma and allergen levels in schools--comparison between Korea and Sweden

We studied reports on respiratory symptoms, asthma and atopic sensitisation in relation to allergen contamination in Korean schools and compared with data from a previous Swedish study performed in eight primary schools. Korean pupils (n = 2365) in 12 primary schools first completed a questionnaire. Then airborne and settled dust were collected from 34 classrooms and analyzed for allergens by ELISA. In both countries, boys reported more symptoms. The prevalence of wheeze was similar, while daytime [odds ratio (OR) = 14.0, 95% confidence interval (CI) = 9.0-21.9] and nocturnal breathlessness (OR = 3.1, 95% CI = 1.5-6.4) were much higher among Korean students. In Korean schools, dog allergen (Can f 1) was the most common followed by mite allergen (Der f 1), while cat (Fel d 1), dog, and horse allergen (Equ cx) were abundant in Sweden. Moreover, CO(2) levels were high in most Korean schools (range 907-4113 ppm). There was an association between allergen levels in dust and air samples, and number of pet-keepers in the classrooms. In conclusion, allergen contamination in Korean schools may be an important public issue. PRACTICAL IMPLICATIONS: This study showed that furry pet allergen contamination was common in both Korean and Swedish schools. In addition, house dust-mite (Der f 1) allergen contamination was common in Korean schools, probably because of transport of allergen from other environments. Transfer should therefore be minimized. Korean schools had high CO(2) levels and the concept of mechanical ventilation should be introduced. Measurement of airborne allergen levels is quite new and seems to be a more convenient and correct way to monitor allergen exposure in classrooms.     

Rhinosinusitis and mold as risk factors for asthma symptoms in occupants of a water-damaged building

Abstract Mold exposure in damp buildings is associated with both nasal symptoms and asthma development, but the progression of building-related (BR) rhinosinusitis symptoms to asthma is unstudied. We examined the risk of developing BR-asthma symptoms in relation to prior BR-rhinosinusitis symptoms and microbial exposure among occupants of a damp building. We conducted four cross-sectional health and environmental surveys among occupants of a 20-story water-damaged office building. We defined BR-rhinosinusitis symptom (N?=?131) and comparison (N?=?361) groups from participants' first questionnaire responses. We compared the odds for the development of BR-asthma symptoms between these two groups over the subsequent surveys, using logistic regression models adjusted for demographics, smoking, building tenure, and first-survey exposures to fungi, endotoxin, and ergosterol. The BR-rhinosinusitis symptom group had higher odds for developing BR-asthma symptoms [odds ratio (OR)?=?2.2; 95% confidence interval (CI)?=?1.3-3.6] in any subsequent survey compared to those without BR-rhinosinusitis symptoms. The BR-rhinosinusitis symptom group with higher fungal exposure within the building had an OR of 7.4 (95% CI?=?2.8-19.9) for developing BR-asthma symptoms, compared to the lower fungal exposure group without BR-rhinosinusitis symptoms. Our findings suggest that rhinosinusitis associated with occupancy of water-damaged buildings may be a sentinel for increased risk for asthma onset in such buildings. PRACTICAL IMPLICATIONS: Exposure to mold is associated with the development of asthma in damp building occupants, and rhinitis is known to be a risk factor for asthma. However, there is little information about the degree of risk for the progression of rhinosinusitis to asthma owing to mold exposures in damp buildings. Our study of damp building occupants demonstrates that building-related (BR) rhinosinusitis symptoms were a risk factor for the development of BR asthma symptoms and that exposure to mold (fungi) or other dampness-related agents augments risk for the development of BR asthma symptoms among those with BR rhinosinusitis symptoms. Our findings suggest that occurrence of BR upper respiratory illness in water-damaged buildings may presage future endemic asthma.     

Formaldehyde and acetaldehyde exposure and risk characterization in California early childhood education environments

Little information is available about air quality in early childhood education (ECE) facilities. We collected single‐day air samples in 2010–2011 from 40 ECE facilities serving children ≤6 years old in California and applied new methods to evaluate cancer risk in young children. Formaldehyde and acetaldehyde were detected in 100% of samples. The median (max) indoor formaldehyde and acetaldehyde levels (μg/m³) were 17.8 (48.8) and 7.5 (23.3), respectively, and were comparable to other California schools and homes. Formaldehyde and acetaldehyde concentrations were inversely associated with air exchange rates (Pearson r = ?0.54 and ?0.63, respectively; P < 0.001). The buildings and furnishings were generally >5 years old, suggesting other indoor sources. Formaldehyde levels exceeded California 8‐h and chronic Reference Exposure Levels (both 9 μg/m³) for non‐cancer effects in 87.5% of facilities. Acetaldehyde levels exceeded the U.S. EPA Reference Concentration in 30% of facilities. If reflective of long‐term averages, estimated exposures would exceed age‐adjusted ‘safe harbor levels’ based on California's Proposition 65 guidelines (10^?5 lifetime cancer risk). Additional research is needed to identify sources of formaldehyde and acetaldehyde and strategies to reduce indoor air levels. The impact of recent California and proposed U.S. EPA regulations to reduce formaldehyde levels in future construction should be assessed.     

Home dampness,childhood asthma,hay fever,and airway symptoms in Shanghai,China: associations,dose‐response relationships,and lifestyle's influences

Numerous studies of associations between dampness and respiratory diseases have been conducted, but their implications remain inconclusive. In this study of 13,335 parent‐reported questionnaires (response rate: 85.3%), we analyzed associations between home dampness and asthma and related symptoms in 4‐ to 6‐year‐old children in a cross‐sectional study of Shanghai. Indicators of home dampness were strongly and significantly associated with dry cough, wheeze, and rhinitis symptoms. In the current residence, children with visible mold spots (VMS) exposure had 32% higher risk of asthma (adjusted OR, 95% CI: 1.32, 1.07–1.64); damp clothing and/or bedding (frequently) was strongly associated with dry cough (1.78, 1.37–2.30); condensation on windows was strongly associated with hay fever (1.60, 1.27–2.01). In the early‐life residence, VMS or damp stains (frequently) were strongly associated with dry cough (2.20, 1.55–3.11) and rhinitis ever (1.57, 1.11–2.21). Associations between dampness and diseases among children with or without family history of atopy were similar. The total number of dampness indicators had strong dose‐response relationships with investigated health outcomes. Actions, including opening windows of the child's room at night and cleaning the child's room frequently, could potentially mitigate 25% of home VMS, thereby preventing more than 1.5% of attributable risk of the studied symptoms.     

Long-term reliability in reporting of childhood pets by adults interviewed twice, 9 years apart. Results from the European Community Respiratory Health Survey I and II

Investigation of long-term effects of childhood pet exposure is usually based on retrospective information provided by adults, while there is little knowledge about the reliability in adult reporting of childhood events. We analyzed 8287 adults interviewed about childhood pets twice, on average nine years apart, in the European Community Respiratory Health Survey. Agreement between the surveys in reporting of childhood cats, dogs and birds were investigated with kappa statistics, and potential effects of disease status on agreement were analyzed with kappa statistics and multiple logistic regressions. Cats, dogs and birds in childhood were reported by 44, 41 and 38%, respectively. Cohen's kappa for agreement in adult reporting of childhood pets was 0.714 (95% CI=0.698-0.729) for cat, 0.709 (0.691-0.722) for dog, and 0.606 (0.591-0.626) for bird. Thus, agreement was significantly higher for reporting of cat and dog than for bird. Adult wheeze, asthma or atopy did not influence agreement. Neither did adult cat sensitization influence agreement in adult reporting of childhood cat. Childhood factors such as moving house <5 years, or growing up as a single child, in a large family or in a rural area, were associated with poorer agreement, while adult factors were unrelated to agreement. PRACTICAL IMPLICATIONS: Long-term reliability in adult reporting of childhood pets was substantial, and not influenced by disease status. Thus, collection of information about childhood pets from adults appears to be reliable for the purpose of studying adult allergic disease. Future studies should consider that the reliability was higher for a more important childhood event and influenced by childhood rather than adult characteristics. Imperfect reliability contributed to underestimation of the effects of pets on adult allergy; i.e. with a kappa of 0.71, a true odds ratio (OR) of 0.80 would be attenuated to 0.86. Future studies should account for non-differential misclassification error.     

Residential culturable fungi, (1‐3, 1‐6)‐β‐d‐glucan,and ergosterol concentrations in dust are not associated with asthma,rhinitis, or eczema diagnoses in children

Qualitative reporting of home indoor moisture problems predicts respiratory diseases. However, causal agents underlying such qualitative markers remain unknown. In the homes of 198 multiple allergic case children and 202 controls in Sweden, we cultivated culturable fungi by directly plating dust, and quantified (1‐3, 1‐6)‐β‐d ‐glucan and ergosterol in dust samples from the child's bedroom. We examined the relationship between these fungal agents and degree of parent or inspector‐reported home indoor dampness, and microbiological laboratory's mold index. We also compared the concentrations of these agents between multiple allergic cases and healthy controls, as well as IgE‐sensitization among cases. The concentrations of culturable fungal agents were comparable between houses with parent and inspector‐reported mold issues and those without. There were no differences in concentrations of the individual or the total summed culturable fungi, (1‐3, 1‐6)‐β‐d ‐glucan, and ergosterol between the controls and the multiple allergic case children, or individual diagnosis of asthma, rhinitis, or eczema. Culturable fungi, (1‐3, 1‐6)‐β‐d ‐glucan, and ergosterol in dust were not associated with qualitative markers of indoor dampness or mold or indoor humidity. Furthermore, these agents in dust samples were not associated with any health outcomes in the children.     

Assessment of endotoxin levels in the home and current asthma and wheeze in school-age children

The relationship between household endotoxin and asthma in children is not clear. To further investigate the relationship between sources of endotoxin and childhood asthma, we conducted a case-control study of children with and without asthma and examined their more frequent household exposures in the home. Children ages 6-13 years with current asthma (n = 70) or wheeze only (n = 19) were sex and age matched (+/-1 year) to 107 controls. Play area and mattress dust were collected for endotoxin analysis. Atopic status was determined by skin prick testing for allergies. A family size of >4 per household was associated with higher endotoxin levels (EU/mg) in the bed dust (P < 0.05). Passive smoking (P < 0.05) and the presence of a cat were associated with higher levels of endotoxin in mattress dust. Endotoxin levels in either the play dust or the bed dust did not differ between cases and controls. Within atopic cases, those with higher endotoxin loads (EU/m2) in bed or play areas were more likely to miss school for chest illness (P < 0.05). In this study, household endotoxin is not a risk factor for current asthma overall but may be associated with increased severity in children with atopic asthma. PRACTICAL IMPLICATIONS: This study did not find that household sources of endotoxin were associated with asthma. However, within atopic asthmatics, asthma severity (as measured by a history of being kept home from school because of a chest illness in the past year) was associated with higher levels of endotoxin in dust from the child's bed. There is a need to further investigate the nature of the relationship between household endotoxin and asthma severity in children which could lead to better management of childhood asthma.     

Breastfeeding modifies the effects of environment tobacco smoke exposure on respiratory diseases and symptoms in Chinese children: the Seven Northeast Cities Study

To evaluate the potential effect of interaction between breastfeeding and environmental tobacco smoke (ETS) exposure on respiratory health, we studied 31 049 children (aged 2–14 years) from 25 districts of seven cities in northeast China. Parents of the children completed standardized questionnaires that characterized the children's histories of respiratory symptoms and illness, feeding methods, ETS exposure, and other associated risk factors. Breastfeeding was defined as having been mainly breastfed for 3 months or more. The results showed that the association of ETS exposure with childhood respiratory conditions/diseases was modified by breastfeeding, and the association for nonbreastfed children was stronger than that for breastfed children. In particular, for nonbreastfed children, the odds ratios (ORs) for the effect of current ETS exposure asthma was 1.71 (95% CI: 1.43–2.05); however, the OR for breastfed children was 1.33 (95% CI: 1.20–1.48), indicating that the interactions between breastfeeding and current ETS exposure on asthma were statistically significant (P = 0.019). When stratified by school (kindergarten vs. elementary school), breastfeeding was more protective for asthma‐related symptoms among children from kindergarten. In conclusion, this study shows that breastfeeding is associated with smaller associations between ETS exposure and respiratory conditions in children, suggesting that breastfeeding reduces susceptibility to the respiratory effects of ETS.     

Indoor air quality,ventilation and health symptoms in schools: an analysis of existing information

We reviewed the literature on Indoor Air Quality (IAQ), ventilation, and building-related health problems in schools and identified commonly reported building-related health symptoms involving schools until 1999. We collected existing data on ventilation rates, carbon dioxide (CO2) concentrations and symptom-relevant indoor air contaminants, and evaluated information on causal relationships between pollutant exposures and health symptoms. Reported ventilation and CO2 data strongly indicate that ventilation is inadequate in many classrooms, possibly leading to health symptoms. Adequate ventilation should be a major focus of design or remediation efforts. Total volatile organic compounds, formaldehyde (HCHO) and microbiological contaminants are reported. Low HCHO concentrations were unlikely to cause acute irritant symptoms (<0.05 ppm), but possibly increased risks for allergen sensitivities, chronic irritation, and cancer. Reported microbiological contaminants included allergens in deposited dust, fungi, and bacteria. Levels of specific allergens were sufficient to cause symptoms in allergic occupants. Measurements of airborne bacteria and airborne and surface fungal spores were reported in schoolrooms. Asthma and 'sick building syndrome' symptoms are commonly reported. The few studies investigating causal relationships between health symptoms and exposures to specific pollutants suggest that such symptoms in schools are related to exposures to volatile organic compounds (VOCs), molds and microbial VOCs, and allergens.     

Dampness in buildings and health. Nordic interdisciplinary review of the scientific evidence on associations between exposure to "dampness" in buildings and health effects (NORDDAMP)

Several epidemiological investigations concerning indoor environments have indicated that "dampness" in buildings is associated to health effects such as respiratory symptoms, asthma and allergy. The aim of the present interdisciplinary review is to evaluate this association as shown in the epidemiological literature. A literature search identified 590 peer-reviewed articles of which 61 have been the foundation for this review. The review shows that "dampness" in buildings appears to increase the risk for health effects in the airways, such as cough, wheeze and asthma. Relative risks are in the range of OR 1.4-2.2. There also seems to be an association between "dampness" and other symptoms such as tiredness, headache and airways infections. It is concluded that the evidence for a causal association between "dampness" and health effects is strong. However, the mechanisms are unknown. Several definitions of dampness have been used in the studies, but all seems to be associated with health problems. Sensitisation to mites may be one but obviously not the only mechanism. Even if the mechanisms are unknown, there is sufficient evidence to take preventive measures against dampness in buildings.     

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.     

Indoor molds, bacteria, microbial volatile organic compounds and plasticizers in schools--associations with asthma and respiratory symptoms in pupils

We investigated asthma and atopy in relation to microbial and plasticizer exposure. Pupils in eight primary schools in Uppsala (Sweden) answered a questionnaire, 1014 (68%) participated. Totally, 7.7% reported doctor-diagnosed asthma, 5.9% current asthma, and 12.2% allergy to pollen/pets. Wheeze was reported by 7.8%, 4.5% reported daytime breathlessness, and 2.0% nocturnal breathlessness. Measurements were performed in 23 classrooms (May-June), 74% had <1000 ppm CO(2) indoors. None had visible mold growth or dampness. Mean total microbial volatile organic compound (MVOC) concentration was 423 ng/m(3) indoors and 123 ng/m(3) outdoors. Indoor concentration of TMPD-MIB (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, Texanol) and TMPD-DIB (2,2,4-trimethyl-1,3-pentanediol diisobutyrate, TXIB), two common plasticizers, were 0.89 and 1.64 microg/m(3), respectively. MVOC and plasticizer concentration were correlated (r = 0.5; P < 0.01). Mold concentration was 360 cfu/m(3) indoors and 980 cfu/m(3) outdoors. At higher indoor concentrations of total MVOC, nocturnal breathlessness (P < 0.01) and doctor-diagnosed asthma (P < 0.05) were more common. Moreover, there were positive associations between nocturnal breathlessness and 3-methylfuran (P < 0.01), 3-methyl-1-butanol (P < 0.05), dimethyldisulfide (P < 0.01), 2-heptanone (P < 0.01), 1-octen-3-ol (P < 0.05), 3-octanone (P < 0.05), TMPD-MIB (P < 0.05), and TMPD-DIB (P < 0.01). TMPD-DIB was positively associated with wheeze (P < 0.05), daytime breathlessness (P < 0.05), doctor-diagnosed asthma (P < 0.05), and current asthma (P < 0.05). In conclusion, exposure to MVOC and plasticizers at school may be a risk factor for asthmatic symptoms in children. PRACTICAL IMPLICATIONS: Despite generally good ventilation and lack of visible signs of mold growth, we found an association between respiratory symptoms and indoor MVOC concentration. In addition, we found associations between asthmatic symptoms and two common plasticizers. The highest levels of MVOC, TMPD-MIB, and TMPD-DIB were found in two new buildings, suggesting that material emissions should be better controlled. As MVOC and plasticizers concentrations were positively correlated, while indoor viable molds and bacteria were negatively correlated, it is unclear if indoor MVOC is an indicator of microbial exposure. Further studies focusing on health effects of chemical emissions from indoor plastic materials, including PVC-floor coatings, are needed.