Bed Dust Research Articles

Mold populations and dust mite allergen concentrations in house dust samples from across Puerto Rico

Lifetime childhood asthma prevalence (LCAP) percentages in Puerto Rico Health Regions (HR) are substantially higher in northeastern vs. southwestern HR. Higher average relative humidity in the northeast might promote mold and mite exposures and possibly asthma prevalence. To test this hypothesis, mold contamination, Environmental Relative Moldiness Index (ERMI) values were measured in floor dust (n = 26) and dust mite allergen concentrations in bed dust (n = 14). For this analysis, the eight HR were divided into those with LCAP > 30 % (n = 3) and < 30 % (n = 5). The average ERMI value was significantly greater (Wilcoxon Rank Sum, p < 0.001) in high than in low LCAP HR (14.5 vs. 9.3). The dust mite antigens Der p 1, Der f 1, and Blo t 5 were detected in 90 % of bed samples, but the concentrations were not significantly different in high vs. low LCAP HR. Mold exposures might partially explain the differences in LCAP HR in Puerto Rico.

Comment on “Distribution features of biological hazardous pollutants in residential environments in Korea [Lee et al., Environ Sci Pollut Res (2014) 21:1146–1152

In their article, Lee et al. (2014) report levels of the major group 1 allergens from the house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae, and bacterial endotoxin in bedding from pregnant women and 6-month-old newborns. There are a number of methodological and interpretive issues with their study. First, endotoxin was determined by the Limulus amebocyte lysate (LAL) method in aqueous extracts of bedding dust. Most, if not all, researchers extract dust samples or filters with pyrogen-free water with the addition of 0.05 % Tween-20 as Douwes et al. (1995) has shown that endotoxin extraction efficiency is about seven times higher in Tween-20containing water than in pyrogen-free water only. Thus, the endotoxin results reported by Lee et al. (2014) maybe seriously underestimated and this may be why the authors only found a detection ratio of endotoxin of 94.5 %, unlike the detection ratio of 100 % in other studies. Secondly, house dust allergen and endotoxin data is skewed, and most studies have log transformed this data before statistical analysis and report results as geometric mean levels with geometric standard deviations or 95 % confidence intervals. It therefore makes it difficult to compare the data of Lee et al. with other published studies. Also, due to likely skewed distribution of allergen and endotoxin data, statistical analysis should have been done by appropriate non-parametric tests. Lee et al. (2014) sampled dust from mattresses in homes with beds, but in homes without beds, dust was collected from blankets and bedclothes. The authors did not present data on the number of samples from the items other than mattresses. This makes interpretation of their data difficult or possibly misleading as it is well known that there are major differences in levels of allergens and endotoxin between mattresses and other bedding items (Hall et al. 2002; Mills et al. 2002; Wickens et al. 2004), with mattresses generally having much higher levels. Lee et al. (2014) found detection rates ofDer p 1 and Der f 1 of 52.7 and 86.5 %, respectively, and deduce thatD. farinae is the dominant house dust mite species in their locality. We have previously shown that D. farinae is also the dominant house dust mite species in Cheonan, Korea (Nam et al. 2008). Our detection rates differed from Lee et al. (2014); in that, we were able to detect Der f 1 in all (100 %) of mattresses, but Der p 1 in only 12 % of mattresses. These differences in detection rates between the two studies in Korea may be due to the nature of the sampled items. In our study (Nam et al. 2008), we only sampled mattresses, while Lee et al. (2014) studied a mix of mattresses and other bedding items.

Burning Man 2011: Mass Gathering Medical Care in a Hostile and Austere Environment

Burning Man is a weeklong outdoor arts festival held annually on a dry Pleistocene lakebed in the rugged and austere Black Rock Desert Wilderness Area in northern Nevada. The 2011 event presented numerous challenges in the provision of emergency medical services and medical care owing to attendance size, the hostile environment, and distance to definitive medical care. Our purpose was to describe the planning and implementation of medical care at a mass gathering event in a harsh and austere wilderness environment. This was a retrospective, observational review of the preparation, management, and implementation of medical care. Total attendance was 53 375, with a total of 2307 patients. Emergency medical services operations included 6 ambulances, 3 quick response vehicles, 2 first aid stations, and a physician staffed mobile hospital. The hospital had limited diagnostic capabilities and a limited formulary. Most conditions treated were minor, the most common being soft tissue injuries, dehydration, eye problems, and urinary tract infections. Most patients were treated and released. A total of 33 patients was transferred out. Several significant cases were seen, including a patient with a spontaneous subarachnoid hemorrhage who later died; there were several cases of trauma, a traumatic pneumothorax, and a thoracic aortic dissection. The latter patient sustained a cardiac arrest at the event, was resuscitated, flown to Reno, underwent emergency surgery, and survived to discharge. A unique phenomenon called “playa foot,” due to an alkali burn of the feet from constant exposure to the dry lake bed dust, was frequently encountered. Overall, Burning Man 2011 was successful. The goal of providing the highest level of care possible in an austere environment and allowing as many patients as possible to remain at the event was achieved. Our experience can help guide others planning for similar events under similar austere conditions in the future.

Children’s residential exposure to selected allergens and microbial indicators: endotoxins and (1→3)-β-D-glucans

The study was aimed at assessment of exposure to endotoxins, (1→3)-β-D-glucans and mite, cockroach, cat, dog allergens present in settled dust in premises of children as agents which may be significantly correlated with the occurrence of allergic symptoms and diseases in children. The study covered 50 homes of one-or two-year-old children in Poland. Samples of settled dust were taken from the floor and the child's bed. The levels of (1→3)-β-D-glucans (floor), endotoxins (floor) and allergens of mite, cat, dog and cockroach (floor and bed) were analyzed. Average geometric concentrations (geometric standard deviation) of endotoxins, (1→3)-β-D-glucans, Der p1, Fel d1, Can f1 and Bla g1 in children homes were on the floor 42 166.0 EU/g (3.2), 20 478.4 ng/g (2.38), 93.9 ng/g (6.58), 119.8 ng/g (13.0), 288.9 ng/g (3.4), 0.72 U/g (4.4) and in their beds (only allergens) 597.8 ng/g (14.2), 54.1 ng/g (4.4), 158.6 ng/g (3.1) 0.6 U/g (2.9), respectively. When the floor was covered with the carpet, higher concentrations of endotoxins, (1→3)-β-D-glucans and allergens (each type) were found in the settled dust (p < 0.05). The trend was opposite in case of allergens (except dog) analyzed from bed dust and significantly higher concentrations were found in the rooms with smooth floor (p < 0.05). Among the analyzed factors only the type of floor significantly modified both the level of biological indicators and allergens. The results of this study could be the base for verifying a hypothesis that carpeting may have a protective role against high levels of cockroach, dog and cat allergens.

Synanthropic Mites of Kolkata, India: An Ecological Appraisal

Ecological observations were made on house dust mites of Kolkata as they form a major part of synanthropic mite community. Dust samples were collected with regard to the abundance of mite in relation to certain socio-ecological parameters like, habitat preference, location of house, construction pattern of house, types of mattresses used and the frequency of cleaning of mattresses. Among two different habitats examined, bed dust contained significantly higher mite population (p < 0.01) than the corresponding bedroom floor dust. The density of total mites and glycyphagids are significantly higher in rural houses in comparison to those of urban houses. In contrast, rural houses contained least number of pyroglyphids/g of dust. The density of total mites as well as pyroglyphid mites/g of dust are higher in mud house in comparison to concrete house. The density of total mites, pyroglyphids and glycyphagids are higher in cotton mattress in comparison to that of foam mattress. The frequency of cleaning has a significant effect on reducing mite densities i.e., the more the frequency of cleaning the lesser are the mite densities.

Clostridium leptum-induced regulatory T cells protect against asthma

Chinese allergic subjects have high levels of sensitization to house dust mite (HDM) and other indoor allergens. This study quantifies common indoor allergen levels in Chinese households.Dust samples were collected from nine cities. Major allergens Der p 1 and Der f 1 from Dermatophagoides pteronyssinus and D. farinae, and specific antigens of Blomia tropicalis, Tyrophagus putrescentiae, Acarus siro, and cockroach species Blattella germanica and Periplaneta americana were measured by ELISA.HDM allergens were found in dust samples from bedding in 95% of the Chinese households. The median levels varied from <0.006 to 9.2 µg/g of dust, depending on the city. The percentages of households having HDM allergen levels associated with the risk of developing allergy sensitization and asthma were 65% and 25%, respectively. Specific antigens of the storage mite and cockroach were only found in samples from the southern and tropical regions of China. Levels of mite allergens were generally higher in samples from bedding compared to samples from the living room, even for storage mites, whereas levels of cockroach antigens were higher in the living room samples.HDM allergens are present in bedding dust samples from most Chinese households. Cities in southern and central China have relatively high levels of HDM major allergens compared to cities in northern and western China. Antigens of storage mites and cockroaches are not as common as HDM allergens.

Domestic airborne black carbon and exhaled nitric oxide in children in NYC

Differential exposure to combustion by-products and allergens may partially explain the marked disparity in asthma prevalence (3-18%) among New York City neighborhoods. Subclinical changes in airway inflammation can be measured by fractional exhaled nitric oxide (FeNO). FeNO could be used to test independent effects of these environmental exposures on airway inflammation. Seven- and eight-year-old children from neighborhoods with lower (range 3-9%, n=119) and higher (range 11-18%, n=121) asthma prevalence participated in an asthma case-control study. During home visits, FeNO was measured, and samples of bed dust (allergens) and air (black carbon; BC) were collected. Neighborhood built-environment characteristics were assessed for the 500 m surrounding participants' homes. Airborne BC concentrations in homes correlated with neighborhood asthma prevalence (P<0.001) and neighborhood densities of truck routes (P<0.001) and buildings burning residual oil (P<0.001). FeNO concentrations were higher among asthmatics with than in those without frequent wheeze (≥4 times/year) (P=0.002). FeNO concentrations correlated with domestic BC among children without seroatopy (P=0.012) and with dust mite allergen among children with seroatopy (P=0.020). The association between airborne BC in homes and both neighborhood asthma prevalence and FeNO suggest that further public health interventions on truck emissions standards and residual oil use are warranted.

Among Middle-income Children In NYC, Neighborhood Reports Of Mouse Sightings Were Associated With Sensitization To Mouse

Previously, we observed that in middle-income NYC homes, mouse allergen in bed dust correlated with neighborhood asthma prevalence (NAP), but not with mouse sensitization among 7-8 year-old children. We then hypothesized that mouse sensitization would be associated with reported mouse sightings in a child's home and neighborhood.

Cat Ownership and Fel d 1 in Bed Dust were Associated with Increased Sensitization to Cat, but Not Asthma Symptoms Among Middle-income Children in New York City

RATIONALE: Pediatric asthma prevalence varies dramatically (3-19%) among neighborhoods in New York City (NYC). Previously we demonstrated that, in low-income NYC communities, where cat ownership is less common than in suburban communities, cat ownership increased risk for developing sensitization but, surprisingly, not for asthma symptoms. We hypothesized that there would be similar associations in middle-income NYC communities.

Do Other Components of Bedding Dust Affect Sensitisation to House Dust Mites?

Bedding dust is a mixture of many components, of which the house dust mite (HDM) allergen, Der p 1, is the most allergenic. There has been little work to investigate the effect of other bedding dust components on HDM sensitisation. The objective of the study was to determine the effect of endotoxin in bedding dust on the allergic response in HDM-sensitised individuals. Twenty-nine house dust mite-sensitised adults were skin prick and allergen patch tested against a sterile solution of their own bedding dust and against a solution containing the same concentration of Der p 1 as the bedding solution for comparison. There was no significant difference in wheal size between the diluted house dust mite solution and the bedding dust in spite of their high levels of endotoxin. Symptomatic subjects had larger, but not statistically significant, responses to commercial house dust mite solution than asymptomatic subjects. Allergen patch test responses were negative in 22/29 of subjects using either bedding dust solutions or comparable diluted house dust mite solutions. An individual's own bedding dust does not appear to contain factors that enhance skin prick test or atopy patch test responses to house dust mites.

Results of a field study on the influence of HygienicWood mattress toppers on the number of mites in bed dust and the state of health of people with house dust mite allergies.

Objectives: So far, there has been no practical or toxicologically non-hazardous way to decimate mites – without interrupting use of beds – in their main reservoir on bed mattresses to such an extent that the allergic condtion of people suffering from house dust mite allergies is reduced or even remedied. As so-called HygienicWood was effective against mites under simulated conditions, the influence of a mattress topper filled with HygienicWood chips on the content of mite antigen Der p1 was to be investigated and the influence on the state of health of the persons concerned analysed at the same time.Procedure: 32 test persons suffering from dust mite allergy were randomly selected. During the course of 5 months, the influence of a HygienicWood mattress topper on the content of the mite antigen Der p1 as well as the number of bacteria, dermatophytes and yeasts in the bed dust were determined and compared with the values obtained during the 5 weeks prior to the application of HygienicWood mattress toppers. The samples were taken from between the HygienicWood mattress topper and the sheet below. At the same time, changes in well-being, state of health, typical allergy symptoms and frequency of taking antihistamines and glucocorticoids were recorded as self-assessments in the form of questionnaires.Findings: The most striking finding was the significant decrease (p=0.000) of the house dust mite antigen Der p1 during usage of the HygienicWood mattress toppers. The effect started immediately after applying the toppers and continued with little fluctuation until the end of the observation period without lessening. At the end of the study, 43% of the test persons stated a slight improvement in their well-being. 13% of the test persons felt no change, and 6% of the test persons stated a slight deterioration. The situation was similar with regard to allergy symptoms: 43% reported a significant reduction, 38% a slight reduction, and 19% did not notice any change. The improvement in symptomatology could not be ascribed to an increased intake of antihistamines or glucocorticoids.The dermatophytes, too, showed a slight, albeit statistically not significant decrease after application of HygienicWood mattress toppers. In contrast, the pollution of bed dust with yeasts rose significantly (p=0.002), whereas there was only a tendency towards an increase in the number of bacteria, which, if one considers the slight increase, is without hygienic relevance. Conclusion: HygienicWood mattress toppers are able to reduce the house dust mite allergen load. This leads to a distinct reduction in the allergy symptomatology, and the well-being of the persons concerned increased significantly.

Further confirmation of the relevance of cockroach and dust mite sensitization to inner‐city asthma morbidity

Further confirmation of the relevance of cockroach and dust mite sensitization to inner‐city asthma morbidity

People with Moderate/Severe Atopic Dermatitis have Higher Human TLR4-Specific Ligand Levels in Bedding Dust, Not Discerned by Conventional Endotoxin Assay

RATIONALE: To determine if patients with moderate/severe atopic dermatitis (AD), known to have high burdens of Staphylococcus aureus, also have high exposure levels of human TLR4 ligands (hTLR4-L), we quantified hTLR4-L in dust samples from moderate/severe versus no AD patients, using novel and conventional methods.

Severe Atopic Dermatitis Is Associated With a High Burden of Environmental Staphylococcus aureus

Leung AD, Schiltz AM, Hall CF, Liu AH. Clin Exp Allergy. 2008;38(5):789–793 PURPOSE OF THE STUDY. It has been established that Staphylococcus aureus worsens atopic dermatitis (AD) by a variety of mechanisms. The purpose of this study was to quantify S aureus burden in the homes of participants with AD of varying severity. STUDY POPULATION. There were 62 volunteers aged 1 to 40 years. Participants were categorized as having mild (n = 18), moderate (n = 14), severe (n = 15), or no (n = 15) AD. METHODS. Participants completed questionnaires about their asthma, allergies, and home environment. Patients with AD completed a Lung-Browder diagram, documenting the area and intensity of erythema, excoriation, papulation, and lichenification. From these diagrams, AD severity was calculated by using the Eczema Area and Severity Index (EASI). Subjects collected dust samples from their bed, the floor next to their bed, and the home vacuum bag and sent them to the laboratory for analysis. S aureus DNA was extracted, and quantitative reverse-transcription polymerase chain reaction for the femB gene (an S aureus–specific genomic marker) was performed. Data were log-transformed and then analyzed with analysis of variance, student's t test, and Spearman's r. RESULTS. Bed dust yielded the highest S aureus concentrations. Participants with severe AD had significantly more S aureus DNA (14.67 pg/mg dust) in bed dust than those with moderate (0.41 pg/mg dust; P &amp;lt; .0001), mild (1.42 pg/mg; P = .0051), and no (0.09 pg/mg; P &amp;lt; .0001) AD. The concentration of S aureus DNA in bed dust strongly correlated with EASI scores. Similar patterns were observed for dust from bedroom floors for both DNA concentrations and EASI scores. The quantity of S aureus DNA from the vacuum samples was significantly higher in participants with severe AD versus moderate, mild, and no AD. However, there was no correlation between EASI scores and concentrations of S aureus DNA from vacuum dust samples. CONCLUSIONS. S aureus is ubiquitous and was detected in dust samples from almost all homes regardless of disease state. However, house dust from participants with severe AD contained the most S aureus DNA. The correlation between S aureus DNA levels and AD severity is driven by proximity to the patient, as shown by the fact that the bed and bedroom floors from the patients with AD yielded the highest levels of S aureus DNA. In the home and especially the bedroom, higher levels of S aureus may contribute to disease severity and persistence in patients with AD. REVIEWER COMMENTS. This is the first study to examine the environmental burden of S aureus in the homes of patients with AD. This study concludes that patients with severe AD have higher environmental burdens of S aureus. The source of the S aureus may be shed bacteria from the skin of the patient with AD, and if live organisms persist in house dust, then they may be the source of recolonization of patients’ skin. However, to prove whether the relationship between high environmental load of S aureus and severe AD is cause or effect, additional studies need to be performed, including quantification of bacterial load on the patient's skin as correlated with home environmental burden and quantification of live bacteria in house dust.

Exposure to environmental bacteria may have differing effects on tumour necrosis factor‐α and interleukin‐6‐producing capacity in infancy

Our previous study showed an association between increased concentration of endotoxin in house dust and elevated IFN-gamma responses in neonates. The impact of other microbial agents on immune responses in infancy is poorly known. To examine whether stimulated cytokine responses of mothers and their children are associated with concentrations of other microbial markers in addition to endotoxin in house dust samples. Mitogen-stimulated production of IFN-gamma, IL-4, IL-6 and TNF-alpha was measured in cord blood and in peripheral blood of mothers (n=29) and their children (n=29) 3 months after birth. Gas chromatography mass spectrometric analysis was applied to measure the concentrations of ergosterol (marker of fungal biomass), muramic acid (indicating the presence of Gram-positive bacteria) and 3-hydroxy fatty acids (C(10:0)-C(14:0), indicating the presence of Gram-negative bacteria) in house dust. Endotoxin was determined with Limulus assay. Significant mother-to-child correlations were observed in stimulated production of TNF-alpha and IL-6 3 months after birth. 3-hydroxy fatty acid (C(10:0)-C(14:0)) levels in bed dust were inversely associated with the production of TNF-alpha and IL-6 in blood samples of mothers and their 3-month-old children. High concentrations of muramic acid in floor dust were related to increased production of TNF-alpha and IL-6 at the age of 3 months. In contrast to endotoxin, none of the other microbial markers were significantly associated with enhanced IFN-gamma-producing capacity from birth to 3 months. Exposure to Gram-negative bacteria and their components may be associated with down-regulated immune responses in early infancy, indicated as an impaired production of pro-inflammatory cytokines following mitogen stimulation. Gram-positive bacteria and their constituents seem to have opposite effects. Of the measured markers, exposure to bioactive endotoxin appears to have the strongest impact on T-helper type 1 responses.

Measurement of ambient aerosols in northern Mexico City by single particle mass spectrometry

Abstract. Continuous ambient measurements with aerosol time-of-flight mass spectrometry (ATOFMS) were made in an industrial/residential section in the northern part of Mexico City as part of the Mexico City Metropolitan Area-2006 campaign (MCMA-2006). Results are presented for the period of 15–27 March 2006. The submicron size mode contained both fresh and aged biomass burning, aged organic carbon (OC) mixed with nitrate and sulfate, elemental carbon (EC), nitrogen-organic carbon, industrial metal, and inorganic NaK inorganic particles. Overall, biomass burning and aged OC particle types comprised 40% and 31%, respectively, of the submicron mode. In contrast, the supermicron mode was dominated by inorganic NaK particle types (42%) which represented a mixture of dry lake bed dust and industrial NaK emissions mixed with soot. Additionally, aluminosilicate dust, transition metals, OC, and biomass burning contributed to the supermicron particles. Early morning periods (2–6 a.m.) showed high fractions of inorganic particles from industrial sources in the northeast, composed of internal mixtures of Pb, Zn, EC and Cl, representing up to 73% of the particles in the 0.2–3μm size range. A unique nitrogen-containing organic carbon (NOC) particle type, peaking in the early morning hours, was hypothesized to be amines from local industrial emissions based on the time series profile and back trajectory analysis. A strong dependence on wind speed and direction was observed in the single particle types that were present during different times of the day. The early morning (3:30–10 a.m.) showed the greatest contributions from industrial emissions. During mid to late mornings (7–11 a.m.), weak northerly winds were observed along with the most highly aged particles. Stronger winds from the south picked up in the late morning (after 11 a.m.), resulting in a decrease in the concentrations of the major aged particle types and an increase in the number fraction of fresh biomass particles. The highest wind speeds were correlated with the highest number fraction of fresh biomass particles (up to 76% of the submicron number fraction) when winds were coming directly from fires that were located south and southeast of the city based on MODIS fire count data. This study provides a unique clock of hourly changes in single particle mixing state and sources as a function of meteorology in Mexico City. These new findings indicate that biomass burning and industrial emissions can make significant contributions to primary particle loadings in Mexico City that are strongly coupled with local meteorology.

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. 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.

Nonlinear relationship of mite allergen exposure to mite sensitization and asthma in a birth cohort

There is uncertainty about the nature of the relationship between mite allergen exposure during infancy and the expression of allergic diseases in childhood. We sought to explore the relationships between repeated measurements of mite allergen exposure during the first 5 years of life and clinical allergic disease outcomes at age 5 years. In a birth cohort of 516 at-risk children, 13 bed dust samples were collected between birth and 5 years of age and analyzed for mite allergen. At age 5 years, the presence of mite atopy was assessed based on skin prick test results, and clinical assessments for asthma, eczema, and wheeze were conducted. The association of allergen exposure with each clinical outcome was examined by means of logistic regression, with adjustments for potential confounders. The lowest and highest mite exposure quintiles, expressed as mean allergen concentration averaged over 0 to 5 years, were associated with a lower prevalence of mite atopy and of asthma compared with intermediate levels of exposure. These relationships, when determined by using average allergen concentration over 0 to 18 months, were weaker. This study demonstrates a nonlinear relationship between mite allergen exposure and clinical outcomes in this generally high mite allergen environment.

The bell tolls for the relationship between house dust mite exposure and asthma in childhood

Prior evidence has suggested a direct relationship between the level of house dust mite (HDM) allergen exposure, sensitisation and asthma. A recent cross-sectional study indicated a bell-shaped relationship between HDM exposure and sensitisation [1]. We examined the effects of cumulative HDM allergen exposure during the first 5 years of life on outcomes at age 5 years in Sydney, a high HDM environment.In the Childhood Asthma Prevention Study, bed dust samples collected at 3, 6, 9 and 12 months and then 6-monthly (total 6615 samples) until age 5 years were analysed for HDM allergen by ELISA. At five years, 516 children were assessed for wheeze and asthma by questionnaires and spirometry, and 488 for sensitisation by skin test. Time-weighted average HDM allergen concentration was estimated for each individual. The range was divided into quintiles with cut-points being 3,5; 7,8; 13,5 and 23,4 ug Der p 1/g. The association between HDM levels and outcomes was analysed with chi-square test, adjusting for confounders.The figure shows the prevalence of outcomes by quintile of time-weighted average of HDM allergen.In this birth cohort, there is a bell-shaped dose response between HDM levels and sensitisation and asthma. This may reflect tolerance to HDM allergen or be attributable to protection from associated exposures, and prompts further research on the mechanisms.

Alternaria measures in inner-city, low-income housing by immunoassay and culture-based analysis

Sensitivity to Alternaria allergens has been associated with severe asthma and life-threatening exacerbations, and a high prevalence of Alternaria sensitivity has been reported among inner-city populations. Traditionally, epidemiologic studies have measured indoor Alternaria concentrations by cultural analyses; however, the number of viable spores may not be a good proxy for allergen levels. Furthermore, other genera share epitopes with Alternaria that may contribute to the allergenic effect. To compare measures of Alternaria antigen by enzyme-linked immunosorbent assay with measures of Alternaria and cross-reactive genera (Ulocladium, Curvularia, Epicoccum, and Stemphylium) by cultural analysis. Antigen assays and cultural analyses were performed on vacuum-collected bed dust samples collected between June 18, 2002, and February 9, 2004, from 3 inner-city, low-income public housing developments. Alternaria antigen was found in all bed dust samples regardless of season. However, culturable Alternaria, Ulocladium, Curvularia, Epicoccum, and Stemphylium were only found in 50%, 35%, 6%, 11%, and 0% of bed samples, respectively. No correlations were found between Alternaria antigen and culturable concentrations of Alternaria or of its cross-reactive genera except for marginal correlation with Ulocladium culturable concentrations. The results confirm that exposure to Alternaria antigens and allergens can occur even in the absence of culturable Alternaria or its cross-reactive genera, so further refinement and use of assays are essential for characterizing the distribution and determinants of indoor fungal allergen levels forsensitive populations.