Increased Levels of Markers of Microbial Exposure in Homes with Indoor Storage of Organic Household Waste

As part of environmental management policies in Europe, separate collection of organic household waste and nonorganic household waste has become increasingly common. As waste is often stored indoors, this policy might increase microbial exposure in the home environment. In this study we evaluated the association between indoor storage of organic waste and levels of microbial agents in house dust. The levels of bacterial endotoxins, mold β(1→3)-glucans, and fungal extracullar polysaccharides (EPS) of Aspergillus and Penicillium species were determined in house dust extracts as markers of microbial exposure. House dust samples were collected in 99 homes in The Netherlands selected on the basis of whether separated organic waste was present in the house. In homes in which separated organic waste was stored indoors for 1 week or more the levels of endotoxin, EPS, and glucan were 3.2-, 7.6-, and 4.6-fold higher, respectively (all P < 0.05), on both living room and kitchen floors than the levels in homes in which only nonorganic residual waste was stored indoors. Increased levels of endotoxin and EPS were observed, 2.6- and 2.1-fold (P < 0.1), respectively, when separated organic waste was stored indoors for 1 week or less, whereas storage of nonseparated waste indoors had no effect on microbial agent levels (P > 0.2). The presence of textile floor covering was another major determinant of microbial levels (P < 0.05). Our results indicate that increased microbial contaminant levels in homes are associated with indoor storage of separated organic waste. These increased levels might increase the risk of bioaerosol-related respiratory symptoms in susceptible people.     

Seasonal Variations of Indoor Microbial Exposures and Their Relation to Temperature,Relative Humidity,and Air Exchange Rate

Indoor microbial exposure has been related to adverse pulmonary health effects. Exposure assessment is not standardized, and various factors may affect the measured exposure. The aim of this study was to investigate the seasonal variation of selected microbial exposures and their associations with temperature, relative humidity, and air exchange rates in Danish homes. Airborne inhalable dust was sampled in five Danish homes throughout the four seasons of 1 year (indoors, n = 127; outdoors, n = 37). Measurements included culturable fungi and bacteria, endotoxin, N-acetyl-beta-d-glucosaminidase, total inflammatory potential, particles (0.75 to 15 μm), temperature, relative humidity, and air exchange rates. Significant seasonal variation was found for all indoor microbial exposures, excluding endotoxin. Indoor fungi peaked in summer (median, 235 CFU/m³) and were lowest in winter (median, 26 CFU/m³). Indoor bacteria peaked in spring (median, 2,165 CFU/m³) and were lowest in summer (median, 240 CFU/m³). Concentrations of fungi were predominately higher outdoors than indoors, whereas bacteria, endotoxin, and inhalable dust concentrations were highest indoors. Bacteria and endotoxin correlated with the mass of inhalable dust and number of particles. Temperature and air exchange rates were positively associated with fungi and N-acetyl-beta-d-glucosaminidase and negatively with bacteria and the total inflammatory potential. Although temperature, relative humidity, and air exchange rates were significantly associated with several indoor microbial exposures, they could not fully explain the observed seasonal variations when tested in a mixed statistical model. In conclusion, the season significantly affects indoor microbial exposures, which are influenced by temperature, relative humidity, and air exchange rates.     

Seasonal Changes in Endotoxin Exposure and Its Relationship to Exhaled Nitric Oxide and Exhaled Breath Condensate pH Levels in Atopic and Healthy Children

Endotoxin, a component of the cell walls of gram-negative bacteria, is a contaminant in organic dusts (house dust) and aerosols. In humans, small amounts of endotoxin may cause a local inflammatory response. Exhaled nitric oxide (eNO) levels, an inflammation indicator, are associated with the pH values of exhaled breath condensate (EBC). This study evaluated seasonal changes on indoor endotoxin concentrations in homes and the relationships between endotoxin exposure and eNO/EBC pH levels for healthy children and children with allergy-related respiratory diseases. In total, 34 children with allergy-related respiratory diseases and 24 healthy children were enrolled. Indoor air quality measurements and dust sample analysis for endotoxin were conducted once each season inside 58 surveyed homes. The eNO, EBC pH levels, and pulmonary function of the children were also determined. The highest endotoxin concentrations were on kitchen floors of homes of children with allergy-related respiratory diseases and healthy children, and on bedroom floors of homes of asthmatic children and healthy children. Seasonal changes existed in endotoxin concentrations in dust samples from homes of children with allergic rhinitis, with or without asthma, and in EBC pH values among healthy children and those with allergy-related respiratory diseases. Strong relationships existed between endotoxin exposure and EBC pH values in children with allergic rhinitis.     

The ecology of microscopic life in household dust

We spend the majority of our lives indoors; yet, we currently lack a comprehensive understanding of how the microbial communities found in homes vary across broad geographical regions and what factors are most important in shaping the types of microorganisms found inside homes. Here, we investigated the fungal and bacterial communities found in settled dust collected from inside and outside approximately 1200 homes located across the continental US, homes that represent a broad range of home designs and span many climatic zones. Indoor and outdoor dust samples harboured distinct microbial communities, but these differences were larger for bacteria than for fungi with most indoor fungi originating outside the home. Indoor fungal communities and the distribution of potential allergens varied predictably across climate and geographical regions; where you live determines what fungi live with you inside your home. By contrast, bacterial communities in indoor dust were more strongly influenced by the number and types of occupants living in the homes. In particular, the female : male ratio and whether a house had pets had a significant influence on the types of bacteria found inside our homes highlighting that who you live with determines what bacteria are found inside your home.     

<Superscript>210</Superscript>Pb concentration in household dust: a potential indicator of long-term indoor radon exposure

Radon decays to a long-lived isotope ²¹⁰Pb with a half-life of about 22 years. Measuring concentrations of ²¹⁰Pb in household dust could be an alternative method of determining indoor radon levels. This novel method for estimating long-term radon concentration was explored in over a hundred Canadian residential homes. The results demonstrate that ²¹⁰Pb concentrations in household dust relate reasonably well to radon concentrations in homes.     

A parametric distribution for the fraction of outdoor soil in indoor dust

For a chemical that does not have a source inside a house, the ratio of its dust concentration indoors to its soil concentration outdoors is equal to the fraction of house dust that is composed of soil. To estimate the fraction of soil in house dust, we compiled ratios of the concentrations of a chemical in dust and soil from the scientific literature. We find that a lognormal distribution fits the data extremely well. This distribution is suitable for use in public health risk assessments for single‐family homes in temperate climates.     

Quantification of ergosterol and 3-hydroxy fatty acids in settled house dust by gas chromatography-mass spectrometry: comparison with fungal culture and determination of endotoxin by a Limulus amebocyte lysate assay.

Ergosterol and 3-hydroxy fatty acids, chemical markers for fungal biomass and the endotoxin of gram-negative bacteria, respectively, may be useful in studies of health effects of organic dusts, including domestic house dust. This paper reports a method for the combined determination of ergosterol and 3-hydroxy fatty acids in a single dust sample and a comparison of these chemical biomarkers determined by gas chromatography-mass spectrometry with results from fungal culture and Limulus assay. Analyses of replicate house dust samples resulted in correlations of 0.91 (ergosterol in six replicates; P < 0.01) and 0.94 (3-hydroxy fatty acids in nine replicates; P < 0.001). The amounts of ergosterol (range, 2 to 16.5 ng/mg of dust) correlated with those of total culturable fungi (range, 6 to 1,400 CFU/mg of dust) in 17 samples, (r = 0.65; P < 0.005). The amounts of endotoxin (range, 11 to 243 endotoxin units/mg of dust) measured with a modified chromogenic Limulus assay correlated with those of lipopolysaccharide (LPS) determined from 3-hydroxy fatty acid analysis of 15 samples. The correlation coefficient depended on the chain lengths of 3-hydroxy acids used to compute the LPS content. The correlation was high (r = 0.88 +/- 0.01; P < 0.001) when fatty acid chains of 10 to 14 carbon atoms were included; the correlation was much lower when hydroxy acids of 16- or 18-carbon chains were included. In conclusion, the results of the described extraction and analysis procedure for ergosterol and 3-hydroxy fatty acids are reproducible, and the results can be correlated with fungal culture and endotoxin activity of organic dust samples.     

Air- and Dustborne Mycoflora in Houses Free of Water Damage and Fungal Growth

Typically, studies on indoor fungal growth in buildings focus on structures with known or suspected water damage, moisture, and/or indoor fungal growth problems. Reference information on types of culturable fungi and total fungal levels are generally not available for buildings without these problems. This study assessed 50 detached single-family homes in metropolitan Atlanta, Ga., to establish a baseline of “normal and typical” types and concentrations of airborne and dustborne fungi in urban homes which were predetermined not to have noteworthy moisture problems or indoor fungal growth. Each home was visually examined, and samples of indoor and outdoor air and of indoor settled dust were taken in winter and summer. The results showed that rankings by prevalence and abundance of the types of airborne and dustborne fungi did not differ from winter to summer, nor did these rankings differ when air samples taken indoors were compared with those taken outdoors. Water indicator fungi were essentially absent from both air and dust samples. The air and dust data sets were also examined specifically for the proportions of colonies from ecological groupings such as leaf surface fungi and soil fungi. In the analysis of dust for culturable fungal colonies, leaf surface fungi constituted a considerable portion (>20%) of the total colonies in at least 85% of the samples. Thus, replicate dust samples with less than 20% of colonies from leaf surface fungi are unlikely to be from buildings free of moisture or mold growth problems.     

Indoor and outdoor airborne fungal propagule concentrations in Mexico City

Thirty homes of asthmatic adults located in Mexico City were examined to determine the predominant culturable fungi and the changes in their airborne concentrations. Fungi were cultured and identified microscopically from air samples collected in naturally ventilated homes, during both wet (July–August) and cool dry (November–December) seasons, and from settled dust from the same homes. Airborne dust from indoor yielded 99–4950 cfu m⁻³, and settled dust 10²–10⁶ cfu g⁻¹ on DG18 agar. The indoor geometric mean concentration of airborne fungi during the cool dry season was 460 cfu m⁻³ while in the wet season it was 141 cfu m⁻³. Similarly, numbers of airborne fungal propagules out of doors decreased 60% between the dry and wet season. In general, the total fungal concentrations in indoor air were less than 10³ cfu m⁻³ and a large proportion of them was collected in Stage-2 of the Andersen sampler. Moreover, the ratio between indoor and outdoor concentrations was <3:1. Five of the 30 sampled homes yielded >500 cfu m⁻³ of one genus, with up to 1493Cladosporium cfu m⁻³ or 2549Penicillium cfu m⁻³. Also, these two genera were predominant in both airborne and settled dust, and their concentrations were greater indoors than out, indicating a possible indoor source of fungal propagules. The predominant species wereCladosporium herbarum, Penicillium aurantiogriseum andP. chrysogenum. These results suggest that exposure to large concentrations of fungi occurs indoors and is associated with both seasons of the year and with particular home characteristics.     

Air- and dustborne mycoflora in houses free of water damage and fungal growth

Typically, studies on indoor fungal growth in buildings focus on structures with known or suspected water damage, moisture, and/or indoor fungal growth problems. Reference information on types of culturable fungi and total fungal levels are generally not available for buildings without these problems. This study assessed 50 detached single-family homes in metropolitan Atlanta, Ga., to establish a baseline of "normal and typical" types and concentrations of airborne and dustborne fungi in urban homes which were predetermined not to have noteworthy moisture problems or indoor fungal growth. Each home was visually examined, and samples of indoor and outdoor air and of indoor settled dust were taken in winter and summer. The results showed that rankings by prevalence and abundance of the types of airborne and dustborne fungi did not differ from winter to summer, nor did these rankings differ when air samples taken indoors were compared with those taken outdoors. Water indicator fungi were essentially absent from both air and dust samples. The air and dust data sets were also examined specifically for the proportions of colonies from ecological groupings such as leaf surface fungi and soil fungi. In the analysis of dust for culturable fungal colonies, leaf surface fungi constituted a considerable portion (>20%) of the total colonies in at least 85% of the samples. Thus, replicate dust samples with less than 20% of colonies from leaf surface fungi are unlikely to be from buildings free of moisture or mold growth problems.     

Anthropogenic chemicals and their impacts on microbes living in buildings

Humans spend the vast majority of their time indoors where complex interactions occur among indoor anthropogenic chemicals, indoor microbiomes and human occupants. This paper summarizes previous work addressing interactions between anthropogenic chemicals associated with indoor household products and building materials, and microorganisms found within the built environment. Water availability seems to determine the extent to which microbes are impacted by anthropogenic chemicals, since desiccation remains one of the primary stressors regulating microbial viability indoors. Several lines of evidence suggest that both fungi and bacteria are capable of transforming biodegradable ingredients originating from various products used indoors when water is present. Previous research also establishes positive and significant correlations between anthropogenic chemicals that are antimicrobial and antibiotic resistance gene abundance. As researchers move towards understanding complex indoor environments as well as the role of anthropogenic chemicals in shaping microbiomes, in situ activities associated with the viable indoor microbial population merit more attention.     

Lactic acid fermentation of food waste for swine feed

This study was conducted to determine the effects of lactic acid bacteria (LAB, Lactobacillus salivarius) inoculation on the microbial, physical and chemical properties of food waste mixture (FWM) stored at ambient temperature (25 degrees C) for 10 and 30 days. A complete pig diet including restaurant food waste, bakery by-product, barley and wheat bran, and broiler poultry litter was amended with LAB at the levels of 0.1%, 0.2%, 0.5% and 1.0% and fermented anaerobically. These treatments were compared with intact FWM before storage and non-anaerobically stored FWM. Non-anaerobic storage of FWM showed microbial putrefaction with the loss (P < 0.05) of water and water soluble carbohydrate (WSC) and increases (P < 0.005) in protein and fiber. Anaerobic fermentation of FWM with or without LAB seemed effective in both 10- and 30-day-storage. The addition of LAB inoculants to FWM showed a linear trend (P < 0.05) toward an increase in the number of total and lactic acid bacteria and toward the nutritional improvement with WSC increased and fiber decreased. Long-term (30 days) storage resulted in consistent reduction (P < 0.05) in numbers of total and lactic acid bacteria and pH and showed little change in chemical components, compared with short-term (10 days) storage. On the basis of these results, LAB inoculation improved fermentative characteristics of FWM. Among anaerobic treatments, further WSC increase and NDF reduction did not occur (P > 0.05) when LAB-added levels were over 0.2%. Based on these observations the optimum level of LAB addition to FWM was 0.2%.     

Evaluation of a Low-Cost Electrostatic Dust Fall Collector for Indoor Air Endotoxin Exposure Assessment

Exposure to endotoxin in home environments has become a key issue in asthma and allergy research. Most studies have analyzed floor or mattress dust endotoxin, but its validity as a proxy for airborne exposure is unknown, while active airborne dust sampling is not feasible in large-scale population studies because of logistic and financial limitations. We therefore developed and evaluated a simple passive airborne dust collection method for airborne endotoxin exposure assessment. We explored an electrostatic dust fall collector (EDC), consisting of a 42- by 29.6-cm-sized folder with four electrostatic cloths exposed to the air. The EDC was tested during two 14-day periods in seven nonfarm and nine farm homes and in farm stables. In parallel, active airborne dust sampling was performed with Harvard impactors and floor dust collected by vacuuming, using nylon sampling socks. The endotoxin levels could be measured in all EDC cloth extracts. The levels (in EU/m²) between EDCs used simultaneously or in different sampling periods in the same home correlated strongly (r > 0.8). EDC endotoxin also correlated moderately to strongly (r = 0.6 to 0.8) with the endotoxin measured by active airborne dust sampling and living room floor dust sampling and—in farm homes—with the endotoxin captured by the EDC in stables. In contrast, endotoxin levels measured by floor dust sampling showed only a poor correlation with the levels measured by active airborne dust sampling. We therefore conclude that measuring endotoxin levels with the EDC is a valid measure of average airborne endotoxin exposure, while reproducibility over time is at least equivalent to that of reservoir dust analyses.     

Characterization of lipopolysaccharides present in settled house dust

The 3-hydroxy fatty acids (3-OHFAs) in lipopolysaccharides (LPS) play an important role in determining endotoxin activity, and childhood exposure to endotoxin has recently been associated with reduced risk of atopic diseases. To characterize the 3-OHFAs in house dust (HD), we used gas chromatography-mass spectrometry to assay 190 HD samples. Dust from beds, bedroom floors, family rooms, and kitchen floors was collected as part of a birth cohort study of childhood asthma (study 1) and a longitudinal study of home allergen and endotoxin (study 2). We also measured endotoxin activity with a Limulus assay and computed specific activity (endotoxin activity per nanomole of LPS). Longer-chain (C(16:0) and C(18:0)) 3-OHFAs were predominant in HD compared with short-chain (C(10:0), C(12:0), and C(14:0)) acids. Endotoxin activity was positively correlated with short-chain 3-OHFAs in both studies. In study 2, 3-OH C(16:0) was negatively correlated and 3-OH C(18:0) was not correlated with endotoxin activity, consistent with previous findings that the Limulus assay responds preferentially to LPS containing short-chain 3-OHFAs. Kitchen dust contained the highest concentrations of 3-OH C(10:0), the highest endotoxin activities, and the highest specific activities (P < 0.03). Bed dust contained the largest amounts of long-chain 3-OHFAs, the highest concentrations of LPS, and the lowest specific activities. Apartments had significantly different types of LPS (P = 0.03) compared with single-family homes in study 2. These data suggest that the Limulus assay may underestimate exposure to certain types of LPS. Because nontoxic LPS may have immune modulating effects, analysis of 3-OHFAs may be useful in epidemiologic studies.     

Mycotoxins in house dust problems and analytical Approaches

People in developed countries spend up to 90% of their time indoors. This led to an increased awareness for problems regarding indoor environment in the recent years. It is known that mycotoxins formed by moulds can be harmful to human health.The body burden of mycotoxins is caused primarily by the uptake of cereals and related products but sometimes also by animal products. However the health effects caused by indoor moulds are currently under investigation. Therefore the aim of an investigation program is to study mould-dependent health effects in a burdened population of the city of Leipzig, Germany. To estimate exposure situation house dust samples are collected from loaded apartments. To realise the measurements of selected mycotoxins in house dust the development of a suitable analytical method was necessary. Capillary electrophoresis in combination with a special clean up of the samples was found to be an useful tool for these investigations.     

Molecular and immunological characterization of arginine kinase from the Indianmeal moth, Plodia interpunctella, a novel cross-reactive invertebrate pan-allergen.

IgE recognition of indoor allergens represents a major cause of allergic asthma in atopic individuals. We found that 52 of 102 patients suffering from allergic symptoms indoors contained IgE Abs against allergens from the Indianmeal moth (Plodia interpunctella), a ubiquitous food pest. Using serum IgE from a moth-sensitized patient we screened an expression cDNA library constructed from P. interpunctella larvae. cDNAs coding for arginine kinase (EC 2.7.3.3), a 40-kDa enzyme commonly occurring in invertebrates that is involved in the storage of such high-energy phosphate bonds as phosphoarginine, were isolated. Recombinant moth arginine kinase, designated Plo i 1, was expressed in Escherichia coli as a histidine-tagged protein with enzymatic activity, and purified to homogeneity by nickel chelate affinity chromatography. Purified recombinant arginine kinase induced specific basophil histamine release and immediate as well as late-phase skin reactions. It reacted with serum IgE from 13 of the 52 (25%) moth-allergic patients and inhibited the binding of allergic patients' IgE to an immunologically related 40-kDa allergen present in house dust mite, cockroach, king prawn, lobster, and mussel. Our results indicate that arginine kinases represent a new class of cross-reactive invertebrate pan-allergens. Recombinant arginine kinase may be used to identify a group of polysensitized indoor allergic patients and for immunotherapy of these individuals.     

Assessment of airborne endotoxin in sandstorm dust and indoor environments using a novel passive sampling device in Al Zulfi city,Saudi Arabia – Establishing threshold exposure levels

The impact of sandstorm dust events affects local air quality and public health. These issues are becoming of greater concern in Saudi Arabia. There is a significant lack of research on airborne endotoxin exposure and analysis in the Middle East countries and no coherent body of research exists focusing on sandstorm dust in worldwide. In this study, we used a novel design of an aluminum foil plate (AFP) electrostatic dust cloth (EDC) for the passive air sampling of sandstorm dust. A total of 38 sandstorm dust samples were collected during sandstorm episodes occurring between January and April 2020 in both indoor (7 days, n = 20) and outdoor environments (24 h, n = 18). After exposure, and following an extraction procedure, bacterial endotoxin levels were measured using the Limulus Amoebocyte Lysate (LAL) gel clot method. The study highlights that the airborne endotoxin level observed was between 10 and 200 EU/m² in both indoor and outdoor environments, during a sandstorm event. Agricultural activities and farmhouses observed higher airborne endotoxin levels. In general, increased endotoxin levels were related to the severity of the sandstorms. Given that the observed values were high as per existing guidelines for respiratory health, we recommend the setting an occupational airborne exposure limit for bacterial endotoxin. This is the first report and further studies across various sandstorm-hit regions will need to be undertaken, together with various sampling methods, in order to assess for seasonal and geographic trends.     

Microbial contamination in kitchens and bathrooms of rural Cambodian village households

Aims: To quantify microbial contamination on kitchen and bathroom surfaces (fomites) in rural Cambodian homes and to compare these concentrations to similar data from the United States and Japan. Methods and Results: This study monitored the numbers of faecal coliforms (i.e. thermotolerant coliforms), total coliforms, Escherichia coli and heterotrophic plate count bacteria on household surfaces in a rural village of Cambodia. Faecal coliform levels in Cambodia were highest on moist locations such as the plastic ladle used for sink water, the toilet seat surface and the cutting board surface with 100‐fold higher levels of faecal coliform bacteria than E. coli and 100‐fold higher levels of faecal coliforms than the US and Japanese studies. Conclusions: A single public health intervention barrier, such as an improved latrine, is only partially effective for household sanitation. For complete sanitation, multiple environmental barriers may be necessary. These barriers occur in a house constructed with easily washable surfaces, a chlorinated water distribution system, house climate control and cleaning product availability. Significance and Impact of the Study: Results of this study can be used to emphasize the importance of increasing household environmental sanitation barriers.     

Exoskeletons and economics: indoor arthropod diversity increases in affluent neighbourhoods

In urban ecosystems, socioeconomics contribute to patterns of biodiversity. The ‘luxury effect’, in which wealthier neighbourhoods are more biologically diverse, has been observed for plants, birds, bats and lizards. Here, we used data from a survey of indoor arthropod diversity (defined throughout as family-level richness) from 50 urban houses and found that house size, surrounding vegetation, as well as mean neighbourhood income best predict the number of kinds of arthropods found indoors. Our finding, that homes in wealthier neighbourhoods host higher indoor arthropod diversity (consisting of primarily non-pest species), shows that the luxury effect can extend to the indoor environment. The effect of mean neighbourhood income on indoor arthropod diversity was particularly strong for individual houses that lacked high surrounding vegetation ground cover, suggesting that neighbourhood dynamics can compensate for local choices of homeowners. Our work suggests that the management of neighbourhoods and cities can have effects on biodiversity that can extend from trees and birds all the way to the arthropod life in bedrooms and basements.     

Architectural design influences the diversity and structure of the built environment microbiome

Buildings are complex ecosystems that house trillions of microorganisms interacting with each other, with humans and with their environment. Understanding the ecological and evolutionary processes that determine the diversity and composition of the built environment microbiome—the community of microorganisms that live indoors—is important for understanding the relationship between building design, biodiversity and human health. In this study, we used high-throughput sequencing of the bacterial 16S rRNA gene to quantify relationships between building attributes and airborne bacterial communities at a health-care facility. We quantified airborne bacterial community structure and environmental conditions in patient rooms exposed to mechanical or window ventilation and in outdoor air. The phylogenetic diversity of airborne bacterial communities was lower indoors than outdoors, and mechanically ventilated rooms contained less diverse microbial communities than did window-ventilated rooms. Bacterial communities in indoor environments contained many taxa that are absent or rare outdoors, including taxa closely related to potential human pathogens. Building attributes, specifically the source of ventilation air, airflow rates, relative humidity and temperature, were correlated with the diversity and composition of indoor bacterial communities. The relative abundance of bacteria closely related to human pathogens was higher indoors than outdoors, and higher in rooms with lower airflow rates and lower relative humidity. The observed relationship between building design and airborne bacterial diversity suggests that we can manage indoor environments, altering through building design and operation the community of microbial species that potentially colonize the human microbiome during our time indoors.