Relationship between the presence of newborn and the house dust endotoxin

Background

Exposure to house dust endotoxin induces of airways' inflammation. Endotoxin are produced by the Gram-negative bacteria, which are released into the stools and could contaminate domestic environment.

Objective

The newborn could contaminate his mattress by endotoxin.

Methods

The dusts of mattress and carpets of 97 newborn' dwellings were sampled at birth and after six months of life. Samplings were made in the bedroom from the baby and in the second place where the baby spent the longer time. The endotoxin concentration was measured by a quantitative Limulus assay and the bacterial contamination was evaluated using 3 selective agar media.

Results

Endotoxin concentration at birth was positively associated with the presence of both sibling and the number of inhabitants (p < 0.01). At 6 months of life, the endotoxin concentration raised significantly not only in the mattresses (from a median of 17.6 (ranges: 0.4-346.7) to 79.6 (3.8-518.8) EU/mg) (p < 0.0001), but also in the dust from the second place where the baby is sleeping (from 20.4 (0.8-226.3) to 101.8 (6.5-634.3) EU/mg) (p < 0.001). Importantly, there was no change in endotoxin concentration from the carpets dust, and the environmental dwelling characteristics remained unchanged. The total bacterial contamination was also positively associated with endotoxin concentration in newborn mattress at birth (p < 0.01) and showed a significant increase at 6 months of life of the newborn (p < 0.01).

Conclusion

The newborn is a significant source of house dust's endotoxin.     

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.     

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.     

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.     

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.     

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.     

A longitudinal study of sick building syndrome among pupils in relation to microbial components in dust in schools in China

There are few longitudinal studies on sick building syndrome (SBS), which include ocular, nasal, throat, and dermal symptoms, headache, and fatigue. We studied the associations between selected microbial components, fungal DNA, furry pet allergens, and incidence and remission of SBS symptoms in schools in Taiyuan, China. The study was based on a two-year prospective analysis in pupils (N = 1143) in a random sample of schools in China. Settled dust in the classrooms was collected by vacuum cleaning and analyzed for lipopolysaccharide (LPS), muramic acid (MuA), and ergosterol (Erg). Airborne dust was collected in Petri dishes and analyzed for cat and dog allergens and fungal DNA. The relationship between the concentration of allergens and microbial compounds and new onset of SBS was analyzed by multi-level logistic regression. The prevalence of mucosal and general symptoms was 33% and 28%, respectively, at baseline, and increased during follow-up. At baseline, 27% reported at least one symptom that improved when away from school (school-related symptoms). New onset of mucosal symptoms was negatively associated with concentration of MuA, total LPS, and shorter lengths of 3-hydroxy fatty acids from LPS, C14, C16, and C18. Onset of general symptoms was negatively associated with C18 LPS. Onset of school-related symptoms was negatively associated with C16 LPS, but positively associated with total fungal DNA. In general, bacterial compounds (LPS and MuA) seem to protect against the development of mucosal and general symptoms, but fungal exposure measured as fungal DNA could increase the incidence of school-related symptoms.     

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.     

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

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

Heating of indoor dust causes reduction in its ability to stimulate release of IL-8 and TNFalpha in vitro compared to non-heated dust

Dust is a major contaminant of the indoor air environment and may affect human health. Indoor dust accumulates on surfaces including heaters and light fixtures, and will be heated when these devices are used. Heat treatment of the dust may change its biologic properties and in this study we simulated the heat treatment with a dust-heating model (50-250 degrees C). The residual and the non-heated dust from seven samples were tested in cultures of fresh peripheral blood mononuclear cells and in A549 cell culture using the release of TNFalpha and IL-8, respectively, as effect indicators. The endotoxin-content and the particle size distribution of the residual and the non-heated dust suspensions were determined for some of the samples. We found that the residual dust had less ability to induce the release of TNFalpha and IL-8. The cytokine decline pattern was similar for all the dust tested and could partly be explained by the reduction in endotoxin content or possibly by inhibitory decomposition products. No correlation was found between the measured particle size distribution and the decreased cytokine levels. The results in this study suggest that the residual dust promotes reduced cytokine response and thereby a possibly lower inflammation reaction in the airways if suspended and inhaled compared with the non-heated dust. PRACTICAL IMPLICATIONS: Accumulation of indoor dust on electric heaters and light fixtures may produce a bad odor when switched on in the cold season and some people claim respiratory distress during such events. To investigate to what extent the residuals of heated indoor dust represent a health hazard, we measured the effect in cell cultures before and after heat treatment of the dust. The in vitro results imply that the residual dust will cause a lower proinflammatory response in the airways if suspended and inhaled compared with non-heated dust. This is partly explained by heat destruction of inflammatory components in the dust.     

Feasibility of zero carbon homes in England by 2016: A house builder's perspective

The UK government set itself a 60% reduction of carbon dioxide emissions target on 2000 levels by 2050. This commitment will require carbon reductions to be made by all industries including the housing sector which presently accounts for 27% of carbon dioxide emissions. The house building industry is the subject of numerous government policies and legislation, but none are as demanding as the Code of Sustainable Homes, which set a ‘world-beating’ target for all new homes to be zero carbon by 2016. This paper sets out to investigate the feasibility of building zero carbon homes in England by 2016 from a house builder's perspective. A comprehensive opinion of the feasibility of zero carbon homes is gathered through a questionnaire survey and in-depth semi-structured interviews with the major UK housing developers. The research found that there are currently numerous legislative, cultural, financial and technical barriers facing house builders to deliver zero carbon homes in England by 2016. The house builders surveyed concurred that these challenges are not insurmountable provided that a swift, all-embracing and above all realistic strategy is adopted and implemented across the supply chain.     

A hybrid approach to house construction - a case study in Botswana

This paper examines the strategy of employing a hybrid combination of indigenous and modern housing construction technologies. Using a Botswana village as a case study, this paper examines four traditional house types in relation to the household income, skills, materials and aspects which could be improved by adapting industrialized methods. Using experimental houses, the case study provides the costs, benefits, potential problems and implementation considerations. The paper discusses the weaknesses and virtues of traditional construction technologies, how appropriate aspects from modern technologies can be incorporated or adapted into traditional methods and the implications for developing appropriate, affordable housing technologies. Dans cette communication, l'auteur s'interesse a la combinaison hybride de techniques indigenes et modernes de construction de maisons. Il prend comme etude de cas un village du Botswana et examine quatre types de maisons classiques en termes de revenus du foyer, de competences, de materiaux et d'aspects que l'on pourrait ameliorer en faisant appel a des methodes de construction industrialisees. L'auteur, se basant sur des maisons experimentales, indique les couts et les avantages, met en garde coutre les problemes possibles et prend en compte les considerations de mise en oeuvre. Il oppose les points faibles des technologies de la construction classique aux avantages, explique comment des aspects appropries des technologies d'aujourd'hui peuvent etre integres ou adaptes aux methodes classiques et examine les consequences que pourrait avoir la mise au point de technologies de construction de logements appropriees et economiques.     

法国社会住宅政策的演变及其启示

法国社会住宅系统创立于19世纪中叶工业革命以后,二战后逐步发展完善,形成了以政府贷款、补贴等优惠政策为刺激,通过公私舍作的方式建设管理社会住宅的系统。社会住宅系统起到了解决贫困人1：2居住问题,缓解社会矛盾,调控房地产市场等多种作用。但社会住宅空间分布集中,建设规模偏大等原因,造成了1980年代以来法国严重的居住隔离问题。2000年以后,法国确立了通过社会住宅的重新分布实现社会混和的战略目标。文章通过对法国社会住宅政策演变历程的回顾,总结出它的成功与失败之处．并结合国内的实际情况、提出中国应加大政府的财政投入、扩大融资方式,建立以租赁为主的保障性住房系统,并以此调控厉地产市场;同时注意通过综合规划,防止居住隔离现象进一步加剧,维持社会的和谐稳定。     

Characterization of endotoxin and 3-hydroxy fatty acid levels in air and settled dust from commercial aircraft cabins

Endotoxin was measured in air and dust samples collected during four commercial aircraft flights. Samples were analyzed for endotoxin biological activity using the Limulus assay. 3-hydroxy fatty acids (3-OH FA) of carbon chain lengths C10:0-C18:0 were determined in dust by gas chromatography-ion trap tandem mass spectrometry. The geometric mean (geometric standard deviation) endotoxin air level was 1.5 EU/m3 (1.9, n = 28); however, significant differences were found by flight within aircraft type. Mean endotoxin levels were significantly higher in carpet dust than in seat dust (140 +/- 81 vs. 51 +/- 25 EU/mg dust, n = 32 each, P < 0.001). Airborne endotoxin levels were not significantly related to either carpet or seat dust endotoxin levels. Mean 3-OH FA levels were significantly higher in carpet dust than in seat dust for C10:2, C12:0, and C14:0 (P < 0.001 for each), while the mean level of C16:0 was significantly higher in seat dust than in carpet dust (P < 0.01). Carpet dust endotoxin was significantly, but moderately, correlated with 3-OH-C12:0 and 3-OH-C14:0 (Pearson r = 0.52 and 0.48, respectively), while correlation of seat dust endotoxin with individual 3-OH FAs depended on the test statistic used. Mean endotoxin potency was significantly higher for carpet dust than for seat dust (6.3 +/- 3.0 vs. 3.0 +/- 1.4 EU/pmol LPS, P < 0.0001). Mean endotoxin levels in the air and dust of commercial aircraft cabins were generally higher than mean levels reported in homes and office buildings. These results suggest that exposure route and dust source are important considerations when relating endotoxin exposure to specific health outcomes.     

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.     

Exposure to microbial components and allergens in population studies: a comparison of two house dust collection methods applied by participants and fieldworkers

Dust collection by study participants instead of fieldworkers would be a practical and cost-effective alternative in large-scale population studies estimating exposure to indoor allergens and microbial agents. We aimed to compare dust weights and biological agent levels in house dust samples taken by study participants with nylon socks, with those in samples taken by fieldworkers using the sampling nozzle of the Allergology Laboratory Copenhagen (ALK). In homes of 216 children, parents and fieldworkers collected house dust within the same year. Dust samples were analyzed for levels of allergens, endotoxin, (1-->3)-beta-D-glucans and fungal extracellular polysaccharides (EPS). Socks appeared to yield less dust from mattresses at relatively low dust amounts and more dust at high dust amounts than ALK samples. Correlations between the methods ranged from 0.47-0.64 for microbial agents and 0.64-0.87 for mite and pet allergens. Cat allergen levels were two-fold lower and endotoxin levels three-fold higher in socks than in ALK samples. Levels of allergens and microbial agents in sock samples taken by study participants are moderately to highly correlated to levels in ALK samples taken by fieldworkers. Absolute levels may differ, probably because of differences in the method rather than in the person who performed the sampling. Practical Implications Dust collection by participants is a reliable and practical option for allergen and microbial agent exposure assessment. Absolute levels of biological agents are not (always) comparable between studies using different dust collection methods, even when expressed per gram dust, because of potential differences in particle-size constitution of the collected dust.