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Background: Endotoxin is ubiquitous in the environment, but its clustering with indoor allergens is not well characterized. This study examined the clustering patterns of endotoxin with allergens in house dust and their association with asthma outcomes., Methods: We analyzed data from 6963 participants of the 2005-2006 National Health and Nutrition Examination Survey. House dust sampled from bedroom floor and bedding was evaluated for endotoxin and allergens from fungi, cockroach, dog, cat, mites, and rodents. Two-step cluster analysis and logistic regressions were performed to identify the clustering patterns and their associations with current asthma and wheeze in the past 12 months, adjusting for covariates., Results: Of the homes, 17.8% had low endotoxin and allergen levels in house dust (Cluster 1). High endotoxin level clustered with Alternaria and pet allergens in the homes of participants with a high socioeconomic status who own pets (Cluster 2) (48.9%). High endotoxin clustered with Aspergillus, dust mites, cockroach, and rodent allergens in the homes of participants with low socioeconomic status (Cluster 3) (33.3%). Compared to Cluster 1, Cluster 2 was associated with higher asthma prevalence (OR 1.42, 95% CI: 1.06-1.91) and wheeze (OR 1.32, 95% CI: 1.07-1.63). Cluster 3 was positively associated with wheeze only in participants sensitized to inhalant allergens (OR 1.42, 95% CI: 1.06-1.91) or exposed to tobacco smoke (OR 1.72, 95% CI: 1.15-2.60)., Conclusions: The clustering of endotoxin with allergens in dust from homes with pets or of people with low socioeconomic status is associated with asthma and wheeze.

Rationale: House endotoxin and ambient air pollution are risk factors for asthma; however, the effects of their coexposure on asthma are not well characterized. Objectives: To examine potential synergistic associations of coexposure to house dust endotoxin and ambient air pollutants with asthma outcomes. Methods: We analyzed data of 6,488 participants in the National Health and Nutrition Examination Survey 2005-2006. Dust from bedding and bedroom floor was analyzed for endotoxin content. The Community Multiscale Air Quality Modeling System (CMAQ) and Downscaler Model data were used to determine annual average particulate matter ≤2.5 μm in aerodynamic diameter (PM 2.5 ), ozone (O 3 ), and nitrogen dioxide (NO 2 ) exposures at participants' residential locations. The associations of the coexposures with asthma outcomes were assessed and tested for synergistic interaction. Measurements and Main Results: In adjusted analysis, PM 2.5 (CMAQ) (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.07-1.18), O 3 (Downscaler Model) (OR, 1.07; 95% CI, 1.02-1.13), and log 10 NO 2 (CMAQ) (OR, 3.15; 95% CI, 1.33-7.45) were positively associated with emergency room visits for asthma in the past 12 months. Coexposure to elevated concentrations of house dust endotoxin and PM 2.5 (CMAQ) was synergistically associated with the outcome, increasing the odds by fivefold (OR, 5.01; 95% CI, 2.54-9.87). A synergistic association was also found for coexposure to higher concentrations of endotoxin and NO 2 in children (OR, 3.45; 95% CI, 1.65-7.18). Conclusions: Coexposure to elevated concentrations of residential endotoxin and ambient PM 2.5 in all participants and NO 2 in children is synergistically associated with increased emergency room visits for asthma. Therefore, decreasing exposure to both endotoxin and air pollution may help reduce asthma morbidity.

Background: Pets are major contributors of endotoxin in homes, but whether they influence endotoxin association with respiratory outcomes is unclear., Objective: To examine whether exposure and sensitization to dog and cat modify the relationship between endotoxin exposure and asthma and wheeze., Methods: We analyzed data from 6051 participants in the 2005-2006 cycle of the National Health and Nutrition Examination Survey (NHANES). House dust from bedroom floor and bedding was evaluated for endotoxin and for dog (Canis familiaris 1) and cat (Feline domesticus 1) allergens. The NHANES also collected data on respiratory outcomes and measured IgE specific to allergens. Associations of log-endotoxin and pet exposure with respiratory outcomes were examined, adjusting for covariates including pet avoidance., Results: Dog and cat ownership among participants was 48.3% and 37.5%, respectively. Endotoxin geometric mean (SE) was 15.49 (0.50) EU/mg. Endotoxin and pet allergen levels were significantly higher in households with a dog or cat. Overall, endotoxin was positively associated with wheeze (odds ratio [OR], 1.30; 95% CI, 1.04-1.62), but not with asthma. However, in participants nonsensitized to dog, the odds of endotoxin association with wheeze were higher with exposure to dog allergen (OR, 1.80; 95% CI, 1.27-2.53; P interaction  = .048). In participants sensitized to cat and exposed to cat allergen, endotoxin became positively associated with asthma (OR, 1.92; 95% CI, 1.21-3.0; P interaction  = .040). With coexposure to dog and cat allergens, endotoxin association with asthma and wheeze was exacerbated (OR, 2.00; 95% CI, 1.04-3.83; P interaction  = .012 and OR, 1.88; 95% CI, 1.32-2.66; P interaction  = .016, respectively)., Conclusions: Exposure to dog and cat allergens enhances the association of endotoxin with asthma and wheeze., (Copyright © 2018 American Academy of Allergy, Asthma & Immunology. All rights reserved.)

Background: Although pets are found in more than 50% of US homes, the effect of pet allergen exposure on asthma morbidity in the US population is not well documented., Objective: To determine the effect of dog and cat allergen exposures on asthma morbidity in the US population., Methods: The National Health and Nutrition Examination Survey is a representative sample of civilian US population. Data on asthma, dog and cat allergen levels in bedroom dust, as well as specific IgE to dog and cat were analyzed for all participants 6 years or older., Results: Pets are common in the United States, with more that 50% of households having a dog or a cat or both. The prevalence of allergic sensitization in the National Health and Nutrition Examination Survey population was similar for dog and cat, with both being approximately 12%. Among those who were sensitized, exposure to elevated levels of pet allergens was associated with an increased prevalence of asthma and asthma attacks. Indeed, 44.2% of the asthma attacks were attributable to exposure to high levels of dog allergen in the bedroom among patients with asthma sensitive to dog and 30.3% were attributable to cat allergen exposure among the comparable cat-sensitive and exposed group. Projecting these results to the US population indicates more than 1 million increased asthma attacks each year for the dog-sensitive and exposed group and more than 500,000 increased asthma attacks for the cat-sensitive and exposed population of patients with asthma., Conclusions: Exposure to elevated levels of dog and cat allergens among those sensitized individuals with asthma is associated with excess asthma attacks. Reducing pet allergen exposures has the potential for a significant decrease in asthma morbidity., (Published by Elsevier Inc.)

Background: Allergic sensitization is an important risk factor for the development of atopic disease. The National Health and Nutrition Examination Survey (NHANES) 2005-2006 provides the most comprehensive information on IgE-mediated sensitization in the general US population., Objective: We investigated clustering, sociodemographic, and regional patterns of allergic sensitization and examined risk factors associated with IgE-mediated sensitization., Methods: Data for this cross-sectional analysis were obtained from NHANES 2005-2006. Participants aged 1 year or older (n = 9440) were tested for serum specific IgEs (sIgEs) to inhalant and food allergens; participants 6 years or older were tested for 19 sIgEs, and children aged 1 to 5 years were tested for 9 sIgEs. Serum samples were analyzed by using the ImmunoCAP System. Information on demographics and participants' characteristics was collected by means of questionnaire., Results: Of the study population aged 6 years and older, 44.6% had detectable sIgEs, whereas 36.2% of children aged 1 to 5 years were sensitized to 1 or more allergens. Allergen-specific IgEs clustered into 7 groups that might have largely reflected biological cross-reactivity. Although sensitization to individual allergens and allergen types showed regional variation, the overall prevalence of sensitization did not differ across census regions, except in early childhood. In multivariate modeling young age, male sex, non-Hispanic black race/ethnicity, geographic location (census region), and reported pet avoidance measures were most consistently associated with IgE-mediated sensitization., Conclusions: The overall prevalence of allergic sensitization does not vary across US census regions, except in early life, although allergen-specific sensitization differs based on sociodemographic and regional factors. Biological cross-reactivity might be an important but not the sole contributor to the clustering of allergen-specific IgEs., (Published by Mosby, Inc.)

Background: Allergic sensitization is a risk factor for asthma and allergic diseases. The relationship between ambient air pollution and allergic sensitization is unclear., Objective: To investigate the relationship between ambient air pollution and allergic sensitization in a nationally representative sample of the US population., Methods: We linked annual average concentrations of nitrogen dioxide (NO2), particulate matter ≤10 μm (PM10), particulate matter ≤2.5 μm (PM2.5), and summer concentrations of ozone (O3), to allergen-specific immunoglobulin E (IgE) data for participants in the 2005-2006 National Health and Nutrition Examination Survey (NHANES). In addition to the monitor-based air pollution estimates, we used the Community Multiscale Air Quality (CMAQ) model to increase the representation of rural participants in our sample. Logistic regression with population-based sampling weights was used to calculate adjusted prevalence odds ratios per 10 ppb increase in O3 and NO2, per 10 μg/m(3) increase in PM10, and per 5 μg/m(3) increase in PM2.5 adjusting for race, gender, age, socioeconomic status, smoking, and urban/rural status., Results: Using CMAQ data, increased levels of NO2 were associated with positive IgE to any (OR 1.15, 95% CI 1.04, 1.27), inhalant (OR 1.17, 95% CI 1.02, 1.33), and indoor (OR 1.16, 95% CI 1.03, 1.31) allergens. Higher PM2.5 levels were associated with positivity to indoor allergen-specific IgE (OR 1.24, 95% CI 1.13, 1.36). Effect estimates were similar using monitored data., Conclusions: Increased ambient NO2 was consistently associated with increased prevalence of allergic sensitization., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: Environmental exposures to phthalates, particularly high-molecular-weight (HMW) phthalates, are suspected to contribute to allergy., Objective: We assessed whether phthalate metabolites are associated with allergic symptoms and sensitization in a large nationally representative sample., Methods: We used data on urinary phthalate metabolites and allergic symptoms (hay fever, rhinitis, allergy, wheeze, asthma) and sensitization from participants ≥ 6 years of age in the National Health and Nutrition Examination Survey (NHANES) 2005-2006. Allergen sensitization was defined as a positive response to at least one of 19 specific IgE antigens (≥ 0.35 kU/L). Odds ratios (ORs) per one log10 unit change in phthalate concentration were estimated using logistic regression adjusting for age, race, body mass index, gender, creatinine, and cotinine. Separate analyses were conducted for children (6-17 years of age) and adults., Results: The HMW phthalate metabolite monobenzyl phthalate (MBzP) was the only metabolite positively associated with current allergic symptoms in adults (wheeze, asthma, hay fever, and rhinitis). Mono-(3-carboxypropyl) phthalate and the sum of diethylhexyl phthalate metabolites (both representing HMW phthalate exposures) were positively associated with allergic sensitization in adults. Conversely, in children, HMW phthalate metabolites were inversely associated with asthma and hay fever. Of the low-molecular-weight phthalate metabolites, monoethyl phthalate was inversely associated with allergic sensitization in adults (OR = 0.79; 95% CI: 0.70, 0.90)., Conclusion: In this cross-sectional analysis of a nationally representative sample, HMW phthalate metabolites, particularly MBzP, were positively associated with allergic symptoms and sensitization in adults, but there was no strong evidence for associations between phthalates and allergy in children 6-17 years of age.

Background: The National Health and Nutrition Examination Survey (NHANES) 2005-2006 was the first population-based study to investigate levels of serum total and allergen-specific IgE in the general US population., Objective: We estimated the prevalence of allergy-related outcomes and examined relationships between serum IgE levels and these outcomes in a representative sample of the US population., Methods: Data for this cross-sectional analysis were obtained from NHANES 2005-2006. Study subjects aged 6 years and older (n = 8086) had blood taken for measurement of total IgE and 19 specific IgE levels against common aeroallergens, including Alternaria alternata, Aspergillus fumigatus, Bermuda grass, birch, oak, ragweed, Russian thistle, rye grass, cat dander, cockroach, dog dander, dust mite (Dermatophagoides farinae and Dermatophagoides pteronyssinus), mouse and rat urine proteins, and selected foods (egg white, cow's milk, peanut, and shrimp). Serum samples were analyzed for total and allergen-specific IgE by using the Pharmacia CAP System. Information on allergy-related outcomes and demographics was collected by questionnaire., Results: In NHANES 2005-2006, 6.6% reported current hay fever, and 23.5% had current allergies. Allergy-related outcomes increased with increasing total IgE levels (adjusted odds ratios for a 10-fold increase in total IgE level of 1.86 [95% CI, 1.44-2.41] for hay fever and 1.64 [95% CI, 1.41-1.91] for allergies). Increased levels of plant-, pet-, and mold-specific IgE contributed independently to allergy-related symptoms. The greatest increase in odds was observed for hay fever and plant-specific IgE (adjusted odds ratio, 4.75; 95% CI, 3.83-5.88)., Conclusion: In the US population self-reported allergy symptoms are most consistently associated with increased levels of plant-, pet-, and mold-specific IgE., (Published by Mosby, Inc.)

Background: Most studies investigating the role of residential mouse allergen exposures in asthma have focused on inner-city populations., Objective: We examined whether elevated mouse allergen levels were associated with occupants' asthma status in a nationally representative sample of U.S. households., Methods: Data for this study were collected as part of the National Survey of Lead and Allergens in Housing. This cross-sectional study surveyed 831 housing units inhabited by 2,456 individuals in 75 different locations throughout the United States. The survey obtained information on demographics, household characteristics, and occupants' health status by questionnaire and environmental observations. We used a polyclonal immunoassay to assess concentrations of mouse urinary protein (MUP) in vacuumed dust collected from various indoor sites., Results: Of the surveyed homes, 82% had detectable levels of MUP, and in 35% of the homes, MUP concentrations exceeded 1.6 microg/g, a level that has been associated with increased mouse allergen sensitization rates. Current asthma, defined as having doctor-diagnosed asthma and asthma symptoms in the preceding 12 months, was positively associated with increased MUP levels. The observed association was modified by atopic status; in allergic individuals, elevated MUP levels (>1.6 microg/g) increased the odds of having asthma symptoms [adjusted OR=1.93; 95% confidence interval (CI), 1.14-3.27], but we found no association in those who did not report allergies (adjusted OR=0.69; 95% CI, 0.33-1.44)., Conclusions: In allergic asthma, residential mouse allergen exposure is an important risk factor for asthma morbidity.

Background: The National Survey of Lead and Allergens in Housing was the first population-based study to measure indoor allergen levels in US homes., Objective: We characterized the overall burden to multiple allergens and examined whether increased allergen levels were associated with occupants' asthma status., Methods: This cross-sectional study surveyed a nationally representative sample of 831 housing units in 75 different locations throughout the United States. Information was collected by means of questionnaire and environmental assessment. Allergen concentrations in dust samples were assessed by using immunoassays. The following cutoff points were used to define increased allergen levels: 10 microg/g for Der p 1, Der f 1, and Can f 1; 8 microg/g for Fel d 1; 8 U/g for Bla g 1; 1.6 microg/g for mouse urinary protein; and 7 microg/g for Alternaria alternata antigens. Allergen burden was considered high when 4 or more allergens exceeded increased levels in any of the sampling locations., Results: Exposure to multiple allergens was common in US homes. Of the surveyed homes, 51.5% had at least 6 detectable allergens and 45.8% had at least 3 allergens exceeding increased levels. Race, income, housing type, absence of children, and presence of smokers, pets, cockroaches, rodents, and mold/moisture-related problems were independent predictors of high allergen burden. Among atopic subjects, high allergen burden increased the odds of having asthma symptoms (odds ratio, 1.81; 95% CI, 1.04-3.15)., Conclusion: Increased allergen levels in the home are associated with asthma symptoms in allergic individuals.

Background: Settled dust has been used in studies to assess exposures to allergens and other biologically active components, but it has not been considered in the aggregate in relation to respiratory health outcomes in the general population., Objective: We addressed whether total house dust weight, an index of total dust exposure, was associated with respiratory health outcomes in the National Survey of Lead and Allergens in Housing (1998-1999) (NSLAH)., Methods: NSLAH was a cross-sectional survey designed to represent permanently occupied housing units in the United States. In each household, a questionnaire was administered and settled dust was vacuumed from five locations. Linear regression models were used to identify predictors of dust weight; logistic regression models were used to examine the relationship between dust weight and asthma and wheeze., Results: Dust weight samples were available for 829 households, and survey information was available for 2,456 participants (children and adults). Lower income, older homes, household pets, having a smoker in the house, and less frequent cleaning predicted higher dust weight levels in U.S. households. Higher levels of dust weight were associated with greater odds of current asthma and wheeze. The strongest associations were seen for wheeze [adjusted odds ratio (OR) = 1.99; 95% confidence interval (CI), 1.21-3.28 for bedroom bed dust; OR = 2.81; 95% CI, 1.52-5.21 for upholstery dust). These associations persisted when adjusting for allergen and endotoxin exposures., Conclusions: Dust weight, an index of total dust exposure in the home, may contribute to respiratory outcomes independently of the exposure to specific components.

Background: Alternaria alternata is one of the most common fungi associated with allergic disease. However, Alternaria exposure in indoor environments is not well characterized., Objective: The primary goals of this study were to examine the prevalence of Alternaria exposure and identify independent predictors of Alternaria antigen concentrations in US homes., Methods: Data for this cross-sectional study were obtained from the National Survey of Lead and Allergens in Housing. A nationally representative sample of 831 housing units in 75 different locations throughout the United States completed the survey. Information on housing and household characteristics was obtained by questionnaire and environmental assessments. Concentrations of A alternata antigens in dust collected from various indoor sites were assessed with a polyclonal anti-Alternaria antibody assay., Results: Alternaria antigens were detected in most (95% to 99%) of the dust samples. The geometric mean concentration, reflecting the average Alternaria concentration in homes, was 4.88 microg/g (SEM, 0.13 microg/g). In the multivariable linear regression analysis, the age of the housing unit, geographic region, urbanization, poverty, family race, observed mold and moisture problems, use of de-humidifier, and presence of cats and dogs were independent predictors of Alternaria antigen concentrations. Less frequent cleaning and smoking indoors also contributed to higher Alternaria antigen levels in homes., Conclusion: Exposure to A alternata antigens in US homes is common. Antigen levels in homes are influenced not only by regional factors but also by residential characteristics. Preventing mold and moisture problems, avoiding smoking indoors, and regular household cleaning may help reduce exposure to Alternaria antigens indoors.