Childhood cat allergen exposure in three European countries: The AIRALLERG study

INTRODUCTION: Cat allergen is a major cause of morbidity among sensitised asthma patients, but little is known about distribution of cat allergen exposure and its determinants in homes. METHODS: We measured cat allergen and potential determinants of cat allergen levels in more than 1000 homes. House dust was collected from children's mattresses and living room floors in approximately 360 homes in The Netherlands, Sweden and Germany and analysed for Fel d 1 in one central laboratory. Exposure was expressed both in concentration (ng/g) and in loads (ng/m2). RESULTS: Levels on mattresses were similar in Sweden and Germany but higher on Dutch mattresses. Dutch floors had higher concentrations than Swedish floors, which had higher concentrations than German floors. The differences in load were less clear. Cat allergen on mattress and floor were moderately to highly correlated. The most important variable quantifying cat allergen variation was the presence of a cat. Floor cover type and last time that floor was vacuumed were important in all three countries. The ratio of cat allergen loads between mattresses from homes with and without cats was higher for Sweden and Germany than for The Netherlands. This is likely related to higher prevalence of cat ownership in The Netherlands which leads to more contamination of homes in which cats were never held. Dust samples from 27-35% of mattresses from homes without cats contained more than 1000 ng/g cat allergen. CONCLUSION: With the exception of cat ownership and floor cover, questionnaire data on housing characteristics did not accurately predict cat allergen in the home.     

Levels and predictors of endotoxin in mattress dust samples from East and West German homes

East-West differences in prevalence of asthma and allergies were suggested to be associated with lifestyle factors. To describe endotoxin levels in mattress dust samples from East and West German homes collected approximately 10 years after reunification. To identify factors that may account for an East-West difference. Dust was collected from mattresses of 2157 infants and 2108 mothers living in Leipzig (former East Germany) and Munich (West Germany). Endotoxin was measured using a chromogenic kinetic Limulus amoebocyte lysate test. Data on bedding, dwelling, and housing characteristics, and occupants' behavior were collected using a self-administered questionnaire. Endotoxin levels were significantly higher in Leipzig compared with Munich for the infants' mattresses but not for the mothers' mattresses. Apart from this, predictors for the mothers' and the infants' mattresses were very similar. Pet-ownership and contact with animals outside the home were most influential. Endotoxin levels in mattress dust were highest in summer and increased with the number of persons living in the household. The overall percentage of variability in endotoxin levels explained by these factors was low. Endotoxin levels were associated with lifestyle factors discussed within the framework of the hygiene hypothesis. None of these factors explains the difference in infant's mattress dust endotoxin between Leipzig and Munich or could be used as a surrogate for endotoxin. PRACTICAL IMPLICATIONS: Endotoxin levels in mattress dust are associated with a number of factors discussed in the framework of the hygiene hypothesis; among other things they are associated with pet-ownership, contact with pets and number of persons living in the home. However, none of these factors and not even a combination of factors explains the variability of endotoxin levels between homes.     

Are cats and dogs the major source of endotoxin in homes?

Previous studies have suggested that exposure to cats and dogs during early childhood reduces the risk of allergic disease, possibly by increasing home endotoxin exposure. This study asked the question of whether cats and dogs are the dominant influence on dust endotoxin concentrations in homes after considering other variables reportedly associated with endotoxin. The presence of cats or dogs in homes, household and home characteristics, and dust endotoxin concentrations from 5 locations were assessed in 966 urban and suburban homes. Whether considered together as pets or as cats and dogs separately, the presence of cats and dogs significantly contributed to living room and bedroom floor endotoxin concentrations, but not to bed endotoxin concentrations. However, the two variables consistently related to endotoxin in all home sites were the home occupant density (occupants/room) and cleanliness of the home. Our data suggest that reducing occupant density and improving home cleanliness would reduce home endotoxin concentrations more than removing pet cats or dogs from the home.     

Fungal extracellular polysaccharides, beta (1-->3)-glucans and culturable fungi in repeated sampling of house dust

Fungal exposure inside homes has been associated with adverse respiratory symptoms in children and adults. While fungal assessment has traditionally relied upon questionnaires, fungal growth on culture plates and spore counts, new immunoassays for extracellular polysaccharides (EPS) and beta (1-->3)-glucans have enabled quantitation of fungal agents in house dust in a more timely and cost-effective manner, possibly providing a better measure of fungal exposure. We investigated associations among measurements of EPS, beta (1-->3)-glucans and culturable fungi obtained from 23 Dutch homes. From each home, dust samples were vacuumed from the living room floor twice during the Fall, Winter and Spring seasons for a total of six collections (every 6 weeks from October 1997 to May 1998). Samples were sieved and fine dust was analyzed for EPS from Aspergillus and Penicillium spp. combined, beta (1-->3)-glucans and culturable fungi. EPS was positively associated with glucan; an increase from the 25th to the 75th percentile of glucan concentration was associated with a 1.6-fold increase in EPS concentration (95% CI = 1.3 to 2.0; p < 0.01). The most significant variables associated with EPS and glucan concentrations were the surface type that was vacuumed and the concentration of total culturable fungi (in colony forming units (CFU)/g dust), with an increase in CFU/g from the 25th to the 75th percentile associated with a 1.3 (1.1-1.6)-fold increase in glucan and a 1.7 (1.3-2.2)-fold increase in EPS concentrations. In addition, the within-home variation of EPS levels were smaller than those between homes (25,646 U/g vs. 50,635 U/g), whereas the variation of glucan levels was similar within and between homes (1,300 vs. 1,205 micrograms/g). These positive associations suggest that house dust concentrations of beta (1-->3)-glucan, and particularly those of EPS, are good markers for the overall levels of fungal concentrations in floor dust which is a surrogate for estimating airborne fungal exposure.     

Geographical variation and the determinants of domestic endotoxin levels in mattress dust in Europe

Endotoxin exposures have manifold effects on human health. The geographical variation and determinants of domestic endotoxin levels in Europe have not yet been extensively described. To investigate the geographical variation and determinants of domestic endotoxin concentrations in mattress dust in Europe using data collected in the European Community Respiratory Health Survey follow-up (ECRHS II). Endotoxin levels were measured in mattress dust from 974 ECRHS II participants from 22 study centers using an immunoassay. Information on demographic, lifestyle, and housing characteristics of the participants was obtained in face-to-face interviews. The median endotoxin concentration in mattress dust ranged from 772 endotoxin units per gram (EU/g) dust in Reykjavik, Iceland, to 4806 EU/g in Turin, Italy. High average outdoor summer temperature of study center, cat or dog keeping, a high household crowding index, and visible damp patches in the bedroom were significantly associated with a higher endotoxin concentrations in mattress dust. There is a large variability in domestic endotoxin levels across Europe. Average outdoor summer temperature of study center, which explains only 10% of the variation in domestic endotoxin level by center, is the strongest meteorological determinant. The observed variation needs to be taken into account when evaluating the health effects of endotoxin exposures in international contexts. PRACTICAL IMPLICATIONS: The incoherent observations of the health effects of endotoxin may be partly owing to the geographical heterogeneity of endotoxin exposure. Therefore, the observed variation should be considered in further studies. Measurements of indoor endotoxin are recommended as an indicator for the level of exposures of individual domestic environments.     

Determinants of endotoxin levels in carpets in New Zealand homes

Endotoxin in house dust has been shown to be associated with asthma severity. Little is known about the influence of housing characteristics on endotoxin distribution. Using standardized methods, dust was sampled from a 1m(2) site and the whole accessible carpet area in selected Wellington, New Zealand homes (n = 77). Endotoxin was measured using a Limulus Amoebocyte Lysate assay. Relative humidity and temperature were recorded using sensors placed in carpet bases. Questionnaires were used to collect information on housing characteristics. All analyses were performed for endotoxin units (EU)/mg and EU/m2 for each site. Geometric mean endotoxin levels were 22.7 EU/mg [geometric standard deviation (GSD) = 2.4] or 30,544 EU/m2 (GSD = 3.2) from the 1m(2) site, and 28.4 EU/mg (GSD = 3.4) or 5653 EU/m2 (GSD = 6.4) from the whole room. After controlling for confounding, endotoxin was positively associated with dogs inside [geometric mean ratio (GMR): 0.9-2.0], total household occupants (GMR: 1.7-2.0, for 1 m2 sample only), vacuum cleaners <1-year old (GMR: 2.3-2.7), reusing vacuum dust collection bags (GMR: 1.4-3.1), steamcleaning or shampooing the carpet (GMR: 1.4-2.2) and high relative humidity (GMR: 1.4-1.6). Lower endotoxin was associated with floor insulation (GMR: 0.4-0.8), and north-facing living rooms (GMR: 0.4-0.8). This study has identified home characteristics that could be modified to reduce endotoxin exposure.     

Dust sampling methods for endotoxin - an essential, but underestimated issue

Exposure to farming environment in early life has been associated with lower risk for allergic diseases possibly caused by increased exposure to endotoxin. The aims of this study were to compare the reproducibility of different sampling methods for endotoxin, and to determine whether environmental characteristics have different effect on endotoxin levels of different sample types. The reproducibility of sampling methods (bed dust, floor dust, vacuum cleaner dust bag dust, settled dust and air samples) was studied with repeated sampling (five visits during 1 year) in five farming and five urban homes. To examine determinants of endotoxin for different types of dust sample, sampling was conducted once in 12 farming and 17 urban homes. Endotoxin was analyzed using Limulus Amebocyte Lysate assay. Bed dust samples had the best reproducibility (intraclass correlation, ICC=66%), but the difference between farming and non-farming homes was not clear with this sample type. The reproducibility of floor (ICC=52%) and settled dust (ICC=51%) was moderate. With these sample types the difference between farming and non-farming homes was clear. Settled dust had some seasonal variation. Based on this study, the best compromise for sampling for endotoxin appears to be floor dust sample followed by bed and settled dust samples. Practical Implications Endotoxins have been widely measured, even though the validity of different sample types to reflect the endotoxin exposure level of an indoor environment is poorly known. This study shows that bed dust samples have the best reproducibility, but they do not reflect the differences in exposure due to environmental factors such as farming. Floor dust samples with moderate reproducibility may be the best choice for sampling of endotoxin in large field studies.     

Distribution variations of multi allergens at asthmatic children's homes

Increasing asthma prevalence is evident in many countries and childhood asthma has also become one of the most common chronic diseases in children. Exposure to indoor allergens has been be attributed to a significant increase in asthma occurrence. Meanwhile, allergen distribution varies widely among different countries. This brief investigation reports the distribution of common indoor allergens, such as mite (Dermatophagoides pteronyssinus, Der p 1 and Der p 2), cat (Felis domesticus, Fel d 1), and German cockroach allergens (Blattella germanica, Bla g 1) at different sites of asthmatic children in Taiwan. Approximately 40 asthmatic children's homes participated in this study and the cohort was followed prospectively for approximately 6 months, starting in December until the following May. Dust samples were collected from each child's mattress, and bedroom and living room floors. All samples were analyzed with monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA). Statistical difference of Der p 1 concen trations is observed among those on the mattress, bedroom and living room floor, except for in May. Seasonal variation in Der p 1 levels on the mattress and bedroom floor is also significant (P < 0.025 and 0.001, respectively). Distributional variation seems to be significant for most allergens among sites within homes in most seasons. Therefore, if only one sample is to be taken, the month of May would be a more ideal choice of study period, and detailed sampling across sites appears to be necessary should the true environmental exposure of allergens be desired.     

Determinants,reproducibility, and seasonal variation of ergosterol levels in house dust

This study aimed to clarify the determinants that affect the concentrations of ergosterol and viable fungi in house dust and to examine the seasonal variation and reproducibility of ergosterol concentrations indoors. In studying the determinants, dust samples from living room floors and vacuum cleaner dust bags were collected from 107 farming and 105 non‐farming homes. Ergosterol levels were determined with gas chromatography‐mass spectrometry, and the dust bag dust was cultivated for enumeration of fungal genera. Lifestyle and environmental factors, for example using of the fireplace, and visible mold observations in homes, explained 20–26% of the variation of fungal concentrations. For the reproducibility study, samples were collected from five urban homes in four different seasons. The reproducibility of ergosterol determinations within a sample was excellent (ICC = 89.8) for floor dust and moderate (ICC = 63.8) for dust bag dust, but poor when sampling the same home throughout a year (ICC = 31.3 and 12.6, respectively) due to large temporal variation in ergosterol concentrations. In conclusion, environmental characteristics only partially predicted the variation of fungal concentrations. Based on these studies, we recommend repeated sampling of dust over time if one seeks to adequately describe overall fungal levels and exposure in a home.     

Endotoxin,extracellular polysaccharides,and β(1‐3)‐glucan concentrations in dust and their determinants in four European birth cohorts: results from the HITEA project

Early‐life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early‐life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early‐life levels of endotoxin, extracellular polysaccharides (EPS), and β(1‐3)‐glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1‐3)‐glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1‐3)‐glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early‐life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries.     

Differential effects of air conditioning type on residential endotoxin levels in a semi‐arid climate

Residential endotoxin exposure is associated with protective and pathogenic health outcomes. Evaporative coolers, an energy‐efficient type of air conditioner used in dry climates, are a potential source of indoor endotoxins; however, this association is largely unstudied. We collected settled dust biannually from four locations in homes with evaporative coolers (n=18) and central air conditioners (n=22) in Utah County, Utah (USA), during winter (Jan‐Apr) and summer (Aug‐Sept), 2014. Dust samples (n=281) were analyzed by the Limulus amebocyte lysate test. Housing factors were measured by survey, and indoor temperature and relative humidity measures were collected during both seasons. Endotoxin concentrations (EU/mg) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons. Endotoxin surface loads (EU/m²) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons and in upholstered furniture during winter. For the nine significant season‐by‐location comparisons, EU/mg and EU/m² were approximately three to six times greater in homes using evaporative coolers. A plausible explanation for these findings is that evaporative coolers serve as a reservoir and distribution system for Gram‐negative bacteria or their cell wall components in homes.     

Determinants of house dust,endotoxin, and β‐(1→3)‐D‐glucan in homes of Danish children

Little is known about the geographic variation and determinants of bacterial endotoxin and β ‐(1,3)‐d ‐glucan in Danish house dust. In a population of 317 children, we: (i) described loads and concentrations of floor dust, endotoxin, and β‐(1→3)‐d ‐glucan and (ii) their correlations and (iii) assessed their determinants; (iv) Finally, we compared our findings with previous European studies. Bedroom floor dust was analyzed for endotoxin content by the kinetic limulus amoebocyte lysate assay and for β‐(1→3)‐d ‐glucan by the inhibition enzyme immunoassay. The parents answered questions regarding potential determinants. We found: geometric means (geometric standard deviations) 186 mg/m² (4.3) for dust; 5.46 × 10³EU/m² (8.0) and 31.1 × 10³EU/g (2.6) for endotoxin; and 142 μg/m² (14.3) and 0.71 × 10³ μg/g (7.3) for β‐(1→3)‐d ‐glucan. High correlations (r > 0.75) were found between floor dust and endotoxin and β‐(1→3)‐d ‐glucan loads, while endotoxin and β‐(1→3)‐d ‐glucan concentrations were moderately correlated (r = 0.36–0.41) with the dust load. Having a carpet was positively associated with dust load and with endotoxin and β‐(1→3)‐d ‐glucan concentrations. Pet keeping, dwelling type, and dwelling location were determinants of endotoxin concentrations. No other determinants were associated with β‐(1→3)‐d ‐glucan concentrations. Compared with other European studies, we found lower β‐(1→3)‐d ‐glucan loads and concentrations but higher endotoxin loads and concentrations suggesting a geographically determined different composition of Danish floor dust compared with other European regions.     

Comparison of two dust collection methods for reservoir indoor allergens and endotoxin on carpets and mattresses

Variable methods of dust collection may lead to uncertainty in the measurement of biomarkers. The purpose of this study was to examine the effect of two different dust collection devices on dust weight, Der p 1, Fel d 1, and endotoxin levels. We compared: (1) a nylon mesh sock inserted between the furniture attachment and the vacuum hose (the reference method) and (2) the ALK device. Duplicate dust samples were collected for 2 min from 2 m(2) of 37 living room floors and from each longitudinal half of 37 mattresses. Measurement of Der p 1 and Fel d 1 were by double monoclonal antibody enzyme-linked immunosorbent assay (ELISA) and endotoxin by a Limulus Amobocyte Lysate assay. Geometric mean ratios (95% confidence intervals) were calculated to show the differences between sampling devices for each measurement. Compared with the ALK device, the reference method collected significantly more dust from floors (sevenfold) and mattresses (threefold) and more total Der p 1, Fel d 1, and endotoxin in both sites. Floor, but not mattress, Der p 1 concentrations were also significantly higher (threefold) using our reference method. We recommend that, in order to minimize sampling device bias, allergen and endotoxin are expressed as a concentration, and that the bed is considered the major source of allergen exposure. Practical Implications Dust sampling equipment can influence the dust yield. In order to have confidence in comparisons of allergen and endotoxin reservoir levels between centers, standardization in the use of sampling equipment is important.     

Social factors, allergen, endotoxin, and dust mass in mattress

Indoor environment has been associated with allergic disease. Further, it has been observed that the prevalences of allergic sensitization are different in different social groups. We therefore investigated the association between socioeconomic status (SES) and indoor bio-contaminants. House dust samples were collected from parents' and infants' mattress from 2166 families in Munich (62.2%) and Leipzig (37.8%), Germany. Major mite allergen Der p 1 and Der f 1, cat allergen Fel d 1, and endotoxin were extracted and quantified. Parental educational level and family equivalent income were used independently as socioeconomic indicators. Indoor endotoxin, mite allergen Der p 1, and the amount of sampled dust were not associated with the social factors. Mite allergen Der f 1 was slightly associated by family SES but without a consistent pattern. In families who are not cat owners, however, a negative association between the amount of cat allergen and family SES were observed. The observed negative association between cat allergen loads and concentrations in mattress and family SES in non-cat owners' homes indicated that community is an important source of cat allergen exposure. PRACTICAL IMPLICATIONS: The study indicated that community is a major source of cat allergen exposure especially in communities of low SES.     

Spatial variability of particulates in homes: implications for infant exposure

Personal monitoring of particulate matter (PM) exposure in infants is difficult. Indirect, microenvironment modelling methods are more practical. Infants spend most of their time indoors at home and the aim of this study was to investigate spatial variations in PM concentrations within homes. Three size fractions of PM - particles with an aerodynamic diameter of less than 10 microm (PM(10)), less than 2.5 microm (PM(2.5)) and total suspended particulates (TSP) - were monitored in the homes of 77 infants (0-2 years) using a multi-stage virtual impactor. In all homes PM was monitored simultaneously in the main living room at heights of 1.4 m and 0.2 m from the floor. In 26 of these homes monitoring was also conducted simultaneously in the infant's bedroom. Further, PM(10) was measured simultaneously in the living room, bedroom and child's cot in 14 homes using a real-time photometer. All homes in the study were non-smoking households. On average, there were no significant differences between concentrations of any of the different PM size fractions measured at the two heights (living room) and between living room and bedroom concentrations. However, there were only moderate correlations in concentrations between the different microenvironments and in some homes there was considerable variation between sampling sites. From the real-time measurements there seemed to be good agreement between concentrations measured in different rooms and in the cot and short-term peak concentrations at one sampling site were often mirrored at other sites. These results suggest that, although large variations in PM concentrations between rooms within homes can occur, a single monitoring station can provide a reasonable estimate of indoor concentrations.     

Predictors of high endotoxin concentrations in the settled dust of German homes

Endotoxin concentrations in settled house dust were measured within the collaborative study named INGA (Indoor Exposure and Genetics in Asthma) together with other asthma-related indoor factors in 405 randomly selected homes in two German cities. Endotoxin was assayed using the quantitative kinetic chromogenic Limulus Amebocyte Lysate (LAL) method. The mean concentration of 2,274 ng endotoxin/g dust in living rooms is about two orders of magnitude below mean occupational exposure (e.g. agriculture). Endotoxin concentrations are higher in old buildings (means ratio = (MR) 1.52, 95% C.I.: 1.14; 2.04), and in the lower storey of the dwelling (MR = 1.30, 95% C.I.: 1.04; 1.62). Furthermore, higher endotoxin concentrations are associated with longer occupancy in the apartment (MR = 1.63, 95% C.I.: 1.21; 2.18), high utilisation of the apartment during the sampling period (MR = 2.52, 95% C.I.: 1.42; 4.47), infrequent vacuum cleaning of the carpets (MR = 1.67; 95% C.I.: 1.10; 2.54), an indifferent attitude to ventilation (MR = 1.37; 95% C.I.: 1.03; 1.82), keeping cats (MR = 1.91; 95% C.I.: 1.43; 2.55) and dogs (1.57; 95% C.I.: 1.08; 2.30), as well as the occurrence of mice (MR = 1.39; 95% C.I.: 1.00; 1.93). The season and indoor climate (operative temperature and relative humidity) did not effect endotoxin concentration. These results indicate that high endotoxin concentration in settled dust is an indicator of poor hygienic conditions in homes.     

Allergens and endotoxin in settled dust from day-care centers and schools in Oslo, Norway

Allergy to indoor allergens can cause frequent and severe health problems in children. Because little is known about the content of allergens in the indoor environments in Norway, we wanted to assess the levels of cat, dog and mite allergens in schools and day-care centers in Oslo. Allergen levels in dust samples from 155 classrooms and 81 day-care units were measured using commercially available enzyme-linked immunosorbent assay (ELISA) kits. Additionally, we measured the levels of endotoxin in 31 day-care units, using the limulus amebocyte lysate test. Most of the dust samples contained detectable amounts of cat and dog allergens. In mattress and floor dust (day-care centers), and curtain and floor dust (schools) the median Fel d 1 levels were 0.17, 0.002, 0.02 and 0.079 microg/m2, while the median Can f 1 levels were 1.7, 0.03, 0.1 and 0.69 microg/m2, respectively. Levels of cat and dog allergens in school floor dust were associated with the number of pupils with animals at home. In contrast, <1% of the samples had measurable levels of the mite allergen Der p 1. Moreover, the levels of endotoxin tended to be higher in dust from floors (1.4 ng/m2) compared with that from mattresses (0.9 ng/m2). PRACTICAL IMPLICATIONS: To reduce allergen exposure, allergic individuals should be placed in the classes/rooms with the fewest pet owners. Moreover, mattresses in day-care centers are major reservoirs of cat and dog allergens and should be cleaned frequently.     

Exposure matrices of endotoxin, (1 → 3)-β-d-glucan, fungi, and dust mite allergens in flood-affected homes of New Orleans

This study examined: (i) biocontaminant levels in flooded homes of New Orleans two years after the flooding; (ii) seasonal changes in biocontaminant levels, and (iii) correlations between biocontaminant levels obtained by different environmental monitoring methods. Endotoxin, (1 → 3)-β-d-glucan, fungal spores, and dust mite allergens were measured in 35 homes during summer and winter. A combination of dust sampling, aerosolization-based microbial source assessment, and long-term inhalable bioaerosol sampling aided in understanding exposure matrices. On average, endotoxin found in the aerosolized fraction accounted for < 2% of that measured in the floor dust, suggesting that vacuuming could overestimate inhalation exposures. In contrast, the (1 → 3)-β-d-glucan levels in the floor dust and aerosolized fractions were mostly comparable, and 25% of the homes showed aerosolizable levels even higher than the dust-borne levels. The seasonal patterns for endotoxin in dust and the aerosolizable fraction were different from those found for (1 → 3)-β-d-glucan, reflecting the temperature and humidity effects on bacterial and fungal contamination. While the concentration of airborne endotoxin followed the same seasonal trend as endotoxin aerosolized from surfaces, no significant seasonal difference was identified for the concentrations of airborne (1 → 3)-β-d-glucan and fungal spores. This was attributed to the difference in the particle size; smaller endotoxin-containing particles can remain airborne for longer time than larger fungal spores or (1 → 3)-β-d-glucan-containing particles. It is also possible that fungal aerosolization in home environments did not reach its full potential. Detectable dust mite allergens were found only in dust samples, and more commonly in occupied homes. Levels of endotoxin, (1 → 3)-β-d-glucan, and fungi in air had decreased during the two-year period following the flooding as compared to immediate measurements; however, the dust-borne endotoxin and (1 → 3)-β-d-glucan levels remained elevated. No conclusive correlations were found between the three environmental monitoring methods. The findings support the use of multiple methods when assessing exposure to microbial contaminants.     

Fungal and endotoxin measurements in dust associated with respiratory symptoms in a water-damaged office building

We investigated the associations of fungal and endotoxin levels in office dust with respiratory health in 888 (67% participation) occupants of a water-damaged building. We analyzed floor and chair dusts from 338 workstations for culturable fungi and endotoxin. Based on averages, we ranked each floor of the building as low, medium, or high for occupants' exposure to each of these agents. Multivariate logistic regression models for building-related symptoms included this ranking of fungi and endotoxin, age, gender, race, smoking status, and duration of occupancy. Using floor dust measures, we found significantly increased odds for lower respiratory symptoms [wheeze, chest tightness, attacks of shortness of breath, and attacks of cough: odds ratios (OR) = 1.7 (95% confidence interval (CI): 1.02-2.77) to 2.4 (95% CI: 1.29-4.59)], throat irritation [OR = 1.7, (95% CI: 1.06-2.82)], and rash/itchy skin [OR = 3.0, (95% CI: 1.47-6.19)] in the highest fungal exposure group compared to the lowest, with generally linear exposure-response relationships. Nonlinear relationships were observed for many of these symptoms and endotoxin in floor dust. Interaction models showed that endotoxin modified effects of fungi on respiratory symptoms. Our findings of exposure interactions and exposure-response relationships of fungal and endotoxin with increased risk of building-related symptoms contribute to an understanding of the role of microbial agents in building-related asthma and respiratory and systemic symptoms. PRACTICAL IMPLICATIONS: Our demonstration of exposure-response relationships between measurements of fungi and/or endotoxin in floor dusts and building-related symptoms implies that microbial agents in floor dust may be a good surrogate measure for dampness-related bioaerosol exposure, considering that measurements of microbial agents in air often fail to demonstrate the associations between exposure and health. In addition, our finding that endotoxin exposure may change the effect of fungal exposure (and vice versa) on respiratory heath suggests that exposure to both fungi and endotoxin should be assessed in epidemiological investigations examining the effect of fungal or endotoxin exposure on respiratory health in indoor environments.     

House dust‐mite allergen exposure is associated with serum specific IgE but not with respiratory outcomes

Exposure to house dust has been associated with asthma in adults, and this is commonly interpreted as a direct immunologic response to dust‐mite allergens in those who are IgE sensitized to house dust‐mite. Mattress house dust‐mite concentrations were measured in a population‐based sample of 2890 adults aged between 27 and 56 years living in 22 centers in 10 countries. Generalized linear mixed models were employed to explore the association of respiratory symptoms with house dust‐mite concentrations, adjusting for individual and household confounders. There was no overall association of respiratory outcomes with measured house dust‐mite concentrations, even in those who reported they had symptoms on exposure to dust and those who had physician‐diagnosed asthma. However, there was a positive association of high serum specific IgE levels to HDM (>3.5 kU_A/l) with mattress house dust‐mite concentrations and a negative association of sensitization to cat with increasing house dust‐mite concentrations. In conclusion, there was no evidence that respiratory symptoms in adults were associated with exposure to house dust‐mite allergen in the mattress, but an association of house mite with strong sensitization was observed.