Levels of endotoxin in 390 Swedish homes: determinants and the risk for respiratory symptoms in children

Microbial diversity in homes and the risk of allergic rhinitis and inhalant atopy in two European birth cohorts

BACKGROUND

Microbial exposures in early childhood direct the development of the immune system and their diversity may influence the risk of allergy development. We aimed to determine whether the indoor microbial diversity at early-life is associated with the development of allergic rhinitis and inhalant atopy.

METHODS

The study population included children within two birth cohorts: Finnish rural-suburban LUKAS (N = 312), and German urban LISA from Munich and Leipzig study centers (N = 248). The indoor microbiota diversity (Chao1 richness and Shannon entropy) was characterized from floor dust samples collected at the child age of 2-3 months by Illumina MiSeq sequencing of bacterial and fungal DNA amplicons. Allergic rhinitis and inhalant atopy were determined at the age of 10 years and analyzed using logistic regression models.

RESULTS

High bacterial richness (aOR 0.19, 95%CI 0.09-0.42 for middle and aOR 0.12, 95%CI 0.05-0.29 for highest vs. lowest tertile) and Shannon entropy were associated with lower risk of allergic rhinitis in LISA, and similar trend was seen in LUKAS. We observed some significant associations between bacterial and fungal diversity measured and the risk of inhalant atopy, but the associations were inconsistent between the two cohorts. High bacterial diversity tended to be associated with increased risk of inhalant atopy in rural areas, but lower risk in more urban areas. Fungal diversity tended to be associated with increased risk of inhalant atopy only in LISA.

CONCLUSIONS

Our study suggests that a higher bacterial diversity may reduce the risk of allergic rhinitis later in childhood. The environment-dependent heterogeneity in the associations with inhalant atopy - visible here as inconsistent results between two differing cohorts - suggests that specific constituents of the diversity may be relevant.

Indoor Microbial Exposures and Chronic Lung Disease: From Microbial Toxins to the Microbiome

Effects of environmental microbial exposures on human health have long been of interest. Microbes were historically assumed to be harmful, but data have suggested that microbial exposures can modulate the immune system. We focus on the effects of indoor environmental microbial exposure on chronic lung diseases. We found contradictory data in bacterial studies using endotoxin as a surrogate for bacterial exposure. Contradictory data also exist in studies of fungal exposure. Many factors may modulate the effect of environmental microbial exposures on lung health, including coexposures. Future studies need to clarify which method of assessing environmental microbial exposures is most relevant.

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/m(2) (4.3) for dust; 5.46 × 10(3) EU/m(2) (8.0) and 31.1 × 10(3) EU/g (2.6) for endotoxin; and 142 μg/m(2) (14.3) and 0.71 × 10(3) 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.

Determinants, reproducibility, and seasonal variation of bacterial cell wall components and viable counts in house dust

The objectives of this study were (i) to assess the determinants that affect concentrations of the bacterial cell wall components 3-hydroxy fatty acids (3-OH FAs) and muramic acid and of total viable bacteria and actinomycetes in house dust; and (ii) to examine the seasonal variation and reproducibility of these bacterial cell wall components in house dust. A number of lifestyle and environmental factors, mostly not consistent for different bacterial measures but commonly including the type of dwelling and farming (number of livestock), explained up to 37% of the variation of the bacterial concentrations in 212 homes in Eastern Finland. The reproducibility of 3-OH FAs and muramic acid measurements in house dust were studied in five urban homes and were found to be generally high (ICC 74-84%). Temporal variation observed in repeated sampling of the same home throughout a year was more pronounced for 3-OH FAs determinations (ICC 22%) than for muramic acid (ICC 55-66%). We conclude that determinants vary largely for different types of bacterial measurements in house dust; the measured parameters represent different aspects of the bacterial content indoors. More than one sample is needed to describe bacterial concentrations in house dust in the home environment due to large temporal variation.

Asthma and the hygiene hypothesis. Does cleanliness matter?

RATIONALE

The early hygiene hypothesis explained the development of allergies by a lack of infections; nowadays, the aspect of excessive cleanliness in affluent populations seems to have replaced this concept. Yet, no investigation has shown that home or personal cleanliness relate to allergic diseases.

OBJECTIVES

To relate personal and home cleanliness to risk of asthma and allergies.

METHODS

Comprehensive questionnaire information on home or personal cleanliness and allergic health conditions at school age was collected in 399 participants of the urban Perinatale Asthma Umwelt Langzeit Allergie Studie (PAULA) birth cohort. Bacterial markers were assessed in floor and mattress dust and were related to cleanliness and allergic diseases.

MEASUREMENTS AND MAIN RESULTS

Personal cleanliness was inversely related to bacterial compounds on floors and mattresses, whereas home cleanliness effectively reduced dust amount but not microbial markers. Exposure to muramic acid related to a lower prevalence of school-age asthma (adjusted odds ratio, 0.59 [95% confidence interval, 0.39; 0.90]). Mattress endotoxin in the first year of life was inversely associated with atopic sensitization (0.73 [0.56-0.96]) and asthma at school age (0.72 [0.55-0.95]). Despite the associations of dust parameters both with cleanliness and allergic health conditions, the development of allergies was not related to home and personal cleanliness.

CONCLUSIONS

Bacterial exposure in house dust determined childhood asthma and allergies. Personal cleanliness, such as washing hands, and home cleanliness were objectively reflected by dust parameters in homes. However, neither personal nor home cleanliness was associated with a risk for asthma and allergies. Other microbial components in house dust not affected by personal hygiene are likely to play a role.

Exposure to indoor pollutants and Wheeze and asthma development during early childhood

Background: This review aimed to summarize existing epidemiological evidence of the association between quantitative estimates of indoor air pollution with early childhood respiratory disease. Methods: We carried out a systematic literature search of peer-reviewed epidemiological studies undertaken in “westernized” countries that have assessed exposure to indoor pollutants and asthma and wheeze from infancy up to the age of 5. Results: The search, between January 2004 and February 2014 yielded 1840 studies for consideration. Following application of eligibility criteria to titles and abstracts 22 independent studies were deemed relevant for further review. Two additional studies were next identified through examination of the references’ lists of these studies. Of these 24 selected studies, 16 adopted a prospective cohort design and 8 were case-control studies. Fourteen studies assessed exposure to bio-aerosols, 8 studies assessed exposure to specific air chemicals and two studies assessed exposure to bio-aerosols and air chemicals. Furthermore, 11 studies examined the association of exposure with asthma and 16 with wheeze. Findings indicate that existing studies have reported contradictory effects of indoor pollutants levels and occurrence of asthma/wheeze. Conclusion: Additional research to establish causality and evaluate interventions to prevent disease onset is needed.

Asthma, allergy and eczema among adults in multifamily houses in Stockholm (3-HE study)--associations with building characteristics, home environment and energy use for heating

Risk factors for asthma, allergy and eczema were studied in a stratified random sample of adults in Stockholm. In 2005, 472 multifamily buildings (10,506 dwellings) were invited (one subject/dwelling) and 7,554 participated (73%). Associations were analyzed by multiple logistic regression, adjusting for gender, age, smoking, country of birth, income and years in the dwelling. In total, 11% had doctor's diagnosed asthma, 22% doctor's diagnosed allergy, 23% pollen allergy and 23% eczema. Doctor's diagnosed asthma was more common in dwellings with humid air (OR = 1.74) and mould odour (OR = 1.79). Doctor's diagnosed allergy was more common in buildings with supply exhaust air ventilation as compared to exhaust air only (OR = 1.45) and was associated with redecoration (OR = 1.48) and mould odour (OR = 2.35). Pollen allergy was less common in buildings using more energy for heating (OR = 0.75) and was associated with humid air (OR = 1.76) and mould odour (OR = 2.36). Eczema was more common in larger buildings (OR 1.07) and less common in buildings using more energy for heating (OR = 0.85) and was associated with water damage (OR = 1.47), humid air (OR = 1.73) and mould odour (OR = 2.01). Doctor's diagnosed allergy was less common in buildings with management accessibility both in the neighbourhood and in larger administrative divisions, as compared to management in the neighbourhood only (OR = 0.49; 95% CI 0.29-0.82). Pollen allergy was less common if the building maintenance was outsourced (OR = 0.67; 95% CI 0.51-0.88). Eczema was more common when management accessibility was only at the division level (OR = 1.49; 95% CI 1.06-2.11). In conclusions, asthma, allergy or eczema were more common in buildings using less energy for heating, in larger buildings and in dwellings with redecorations, mould odour, dampness and humid air. There is a need to reduce indoor chemical emissions and to control dampness. Energy saving may have consequences for allergy and eczema. More epidemiological studies are needed on building management organization.

Endotoxins in indoor air and settled dust in primary schools in a subtropical climate

Endotoxins can significantly affect the air quality in school environments. However, there is currently no reliable method for the measurement of endotoxins, and there is a lack of reference values for endotoxin concentrations to aid in the interpretation of measurement results in school settings. We benchmarked the "baseline" range of endotoxin concentration in indoor air, together with endotoxin load in floor dust, and evaluated the correlation between endotoxin levels in indoor air and settled dust, as well as the effects of temperature and humidity on these levels in subtropical school settings. Bayesian hierarchical modeling indicated that the concentration in indoor air and the load in floor dust were generally (<95th percentile) <13 EU/m(3) and <24,570 EU/m(2), respectively. Exceeding these levels would indicate abnormal sources of endotoxins in the school environment and the need for further investigation. Metaregression indicated no relationship between endotoxin concentration and load, which points to the necessity for measuring endotoxin levels in both the air and settled dust. Temperature increases were associated with lower concentrations in indoor air and higher loads in floor dust. Higher levels of humidity may be associated with lower airborne endotoxin concentrations.

Vocal cord dysfunction related to water-damaged buildings

BACKGROUND

Vocal cord dysfunction (VCD) is the intermittent paradoxical adduction of the vocal cords during respiration, resulting in variable upper airway obstruction. Exposure to damp indoor environments is associated with adverse respiratory health outcomes, including asthma, but its role in the development of VCD is not well described.

OBJECTIVE

We describe the spectrum of respiratory illness in occupants of 2 water-damaged office buildings.

METHODS

The National Institute for Occupational Safety and Health conducted a health hazard evaluation that included interviews with managers, a maintenance officer, a remediation specialist who had evaluated the 2 buildings, employees, and consulting physicians. In addition, medical records and reports of building evaluations were reviewed. Diagnostic evaluations for VCD had been conducted at the Asthma and Allergy Center of the Medical College of Wisconsin.

RESULTS

Two cases of VCD were temporally related to occupancy of water-damaged buildings. The patients experienced cough, chest tightness, dyspnea, wheezing, and hoarseness when in the buildings. Spirometry was normal. Methacholine challenge did not show bronchial hyperreactivity but did elicit symptoms of VCD and inspiratory flow-volume loop truncation. Direct laryngoscopy revealed vocal cord adduction during inspiration. Coworkers developed upper and lower respiratory symptoms; their diagnoses included sinusitis and asthma, consistent with recognized effects of exposure to indoor dampness. Building evaluations provided evidence of water damage and mold growth.

CONCLUSION

VCD can occur with exposure to water-damaged buildings and should be considered in exposed patients with asthma-like symptoms.