Sampling, extraction and measurement of bacteria, endotoxin, fungi and inflammatory potential of settling indoor dust

Work in nursing homes and occupational exposure to endotoxin and bacterial and fungal species

Indoor microbial exposure may cause negative health effects. Only little is known about the occupational microbial exposure in nursing homes and the factors that influence the exposure. The exposure in nursing homes may be increased due to close contact with elderly persons who may carry infectious or antimicrobial-resistant microorganisms and due to handling of laundry, such as used clothing and bed linen. We investigated the microbial exposure in 5 nursing homes in Denmark, by use of personal bioaerosol samples from different groups of staff members taken during a typical working day, stationary bioaerosol measurements taken during various work tasks, sedimented dust samples, environmental surface swabs, and swabs from staff members' hands. From the samples, we explored bacterial and fungal concentrations and species composition, endotoxin levels, and antimicrobial resistance in Aspergillus fumigatus isolates. Microbial concentrations from personal exposure samples differed among professions, and geometric means (GM) were 2,159 cfu/m3 (84 to 1.5 × 105) for bacteria incubated on nutrient agar, 1,745 cfu/m3 (82 to 2.0 × 104) for bacteria cultivated on a Staphylococcus selective agar, and 16 cfu/m3 air for potential pathogenic fungi incubated at 37 °C (below detection limit to 257). Bacterial exposures were elevated during bed making. On surfaces, the highest bacterial concentrations were found on bed railings. The majority of bacterial species found were related to the human skin microflora, such as different Staphylococcus and Corynebacterium species. Endotoxin levels ranged from 0.02 to 59.0 EU/m3, with a GM of 1.5 EU/m3. Of 40 tested A. fumigatus isolates, we found one multiresistant isolate, which was resistant towards both itraconazole and voriconazole, and one isolate resistant towards amphotericin B. In conclusion, we give an overview of the general microbial exposure in nursing homes and show that microbial exposures are higher for staff with more care and nursing tasks compared with administrative staff.

Exposure levels of animal allergens, endotoxin, and β-(1,3)-glucan on a university campus of veterinary medicine

OBJECTIVES

The study aimed to determine the allergen, endotoxin and β-(1,3)-glucan concentrations at various areas on a university campus of veterinary medicine.

METHODS

Dust samples were collected four times a year for three years using electrostatic dust collectors (EDC) at 25 different locations on a campus of veterinary medicine and in laboratories of inorganic chemistry as a control area representing animal-free environment. Major animal allergens from dog, cat, horse, cattle and mouse, domestic mite (DM) allergens, and β-(1,3)-glucan were measured using enzyme immunoassays and endotoxin using the limulus amoebocyte lysate (LAL) assay. Seasonal, annual and local influences on exposure levels were analyzed using Bayesian mixed models.

RESULTS

With the exception of mouse allergens, all other determinants were found in almost all locations on the campus and in the control area, but in up to 10.000-fold variable concentrations. By far the highest levels of feline, canine, equine and bovine allergens were detected in buildings where the respective species were examined. The highest levels of mouse and DM allergens, β-(1,3)-glucan and endotoxin occurred together and were associated with locations where large animals were present. In buildings without animals, allergen levels were considerably lower but still elevated at several locations compared to the control area, especially for dog and horse allergens, and β-(1,3)-glucan. Significant seasonal effects were observed for dog, cat, horse and DM allergens, and β-(1,3)-glucan. Variations between years were less apparent than between seasons (except for β-(1,3)-glucan).

CONCLUSIONS

The strongest influencing factor on the concentration of mammalian allergens was the presence of the corresponding animal at the collection site. Seasonal influence on allergen concentrations was observed, while the overall exposure remained constant over the years. At locations with horses, elevated levels of mite allergens, endotoxin, and β-(1,3)-glucan can be expected, probably due to passive transfer from stable environment.

Airborne bacterial species in indoor air and association with physical factors

The aim of this study is to obtain knowledge about which cultivable bacterial species are present in indoor air in homes, and whether the concentration and diversity of airborne bacteria are associated with different factors. Measurements have been performed for one whole year inside different rooms in five homes and once in 52 homes. Within homes, a room-to-room variation for concentrations of airborne bacteria was found, but an overlap in bacterial species was found across rooms. Eleven species were found very commonly and included: Acinetobacter lowffii, Bacillus megaterium, B. pumilus, Kocuria carniphila, K. palustris, K. rhizophila, Micrococcus flavus, M. luteus, Moraxella osloensis and Paracoccus yeei. The concentrations of Gram-negative bacteria in general and the species P. yeei were significantly associated with the season with the highest concentrations in spring. The concentrations of P. yeei, K. rhizophila and B. pumilus were associated positively with relative humidity (RH), and concentrations of K. rhizophila were associated negatively with temperature and air change rate (ACR). Micrococcus flavus concentrations were associated negatively with ACR. Overall, this study identified species which are commonly present in indoor air in homes, and that the concentrations of some species were associated with the factors: season, ACR and RH.

Composition of Culturable Microorganisms in Dusts Collected from Sport Facilities in Finland during the COVID-19 Pandemic

Sport facilities represent extreme indoor environments due to intense cleaning and disinfection. The aim of this study was to describe the composition of the cultivated microbiota in dust samples collected in sport facilities during the COVID-19 pandemic. A dust sample is defined as the airborne dust sedimented on 0.02 m² within 28 d. The results show that the microbial viable counts in samples of airborne dust (n = 9) collected from seven Finnish sport facilities during the pandemic contained a high proportion of pathogenic filamentous fungi and a low proportion of bacteria. The microbial viable counts were between 14 CFU and 189 CFU per dust sample. In seven samples from sport facilities, 20-85% of the microbial viable counts were fungi. Out of 123 fungal colonies, 47 colonies belonged to the potentially pathogenic sections of Aspergillus (Sections Fumigati, Nigri, and Flavi). Representatives of each section were identified as Aspergillus fumigatus, A. flavus, A. niger and A. tubingensis. Six colonies belonged to the genus Paecilomyces. In six samples of dust, a high proportion (50-100%) of the total fungal viable counts consisted of these potentially pathogenic fungi. A total of 70 isolates were considered less likely to be pathogenic, and were identified as Aspergillus section Nidulantes, Chaetomium cochliodes and Penicillium sp. In the rural (n = 2) and urban (n = 7) control dust samples, the microbial viable counts were >2000 CFU and between 44 CFU and 215 CFU, respectively, and consisted mainly of bacteria. The low proportion of bacteria and the high proportion of stress tolerant, potentially pathogenic fungi in the dust samples from sport facilities may reflect the influence of disinfection on microbial communities.

Microbial contamination and metabolite exposure assessment during waste and recyclable material collection

Waste workers are exposed to bioaerosols when handling, lifting and dumping garbage. Bioaerosol exposure has been linked to health problems such as asthma, airway irritant symptoms, infectious, gastrointestinal and skin diseases, and cancer. Our objective was to characterize the exposure of urban collectors and drivers to inhalable bioaerosols and to measured the cytotoxic effect of air samples in order to evaluate their health risk. Personal and ambient air sampling were conducted during the summer of 2019. Workers from 12 waste trucks collecting recyclables, organic waste or compost were evaluated. Bacteria and fungi were cultured, molecular biology methods were used to detect microbial indicators, cytotoxic assays were performed and endotoxins and mycotoxins were quantified. Domestic waste collectors were exposed to concentrations of bacteria and endotoxins above the recommended limits, and Aspergillus section Fumigati was detected at critical concentrations in their breathing zones. Cytotoxic effects were observed in many samples, demonstrating the potential health risk for these workers. This study establishes evidence that waste workers are exposed to microbial health risks during collection. It also demonstrates the relevance of cytotoxic assays in documenting the general toxic risk found in air samples. Our results also suggest that exposures differ depending on the type of waste, job title and discharge/unloading locations.

Microbial contamination in waste collection: Unveiling this Portuguese occupational exposure scenario

Previous studies anticipated that microorganisms and their metabolites in waste will increase as a consequence of a decreased collection frequency and due to differences in what kind of waste is bagged before collection leading to an increased exposure of workers handling the waste. This study aim was to investigate the microbial contamination present in the waste collection trucks (WCT) and in the support facilities (waste collection station - WCS). It was applied a multi-approach protocol using active (air sampling by impingement and impaction) and passive (surface swabs, electrostatic dust cloths and settled dust) sampling methods. The screening of azole-resistance, the investigation of mycotoxins and the assessment of the elicited biological responses in vitro were also carried out aiming recognizing the possible health effects of waste collection drivers. SARS-CoV-2 detection was also performed. In WCS only air samples had contamination in all the four sampling sites (canteen, operational removal core, operational removal center, and administrative service). Among all the analyzed matrices from the WCT a higher percentage of total bacterial counts and Gram-was detected in swabs (66.93%; 99.36%). In WCS the most common species were Penicillium sp. (43.98%) and Cladosporium sp. (24.68%), while on WCT Aspergillus sp. (4.18%) was also one of the most found. In the azole resistance screening Aspergillus genera was not observed in the azole-supplemented media. SARS-CoV-2 was not detected in any of the environmental samples collected, but Aspergillus section Fumigati was detected in 5 samples. Mycotoxins were not detected in EDC from WCS, while in WCT they were detected in filters (N = 1) and in settled dust samples (N = 16). In conclusion, our study reveals that a comprehensive sampling approach using active and passive sampling (e.g. settled dust sampling for a representative mycotoxin evaluation) and combined analytic methods (i.e., culture-based and molecular) is an important asset in microbial exposure assessments. Concerning the waste collection exposure scenario, the results of this study unveiled a complex exposure, particularly to fungi and their metabolites. Aspergillus section Fumigati highlight the significance of targeting this section in the waste management industry as an indicator of occupational health risk.

Passive Bioaerosol Samplers: A Complementary Tool for Bioaerosol Research. A Review

Bioaerosols consist of airborne particles of biological origin. They play an important role in our environment and may cause negative health effects. The presence of biological aerosol is typically determined using active samplers. While passive bioaerosol samplers are used much less frequently in bioaerosol investigations, they offer certain advantages, such as simple design, low cost, and long sampling duration. This review discusses different types of passive bioaerosol samplers, including their collection mechanisms, advantages and disadvantages, applicability in different sampling environments, and available sample elution and analysis methods. Most passive samplers are based on gravitational settling and electrostatic capture mechanism or their combination. We discuss the agar settle plate, dustfall collector, Personal Aeroallergen Sampler (PAAS), and settling filters among the gravity-based samplers. The described electrostatics-based samplers include electrostatic dust cloths (EDC) and Rutgers Electrostatic Passive Sampler (REPS). In addition, the review also discusses passive opportunity samplers using preexisting airflow, such as filters in HVAC systems. Overall, passive bioaerosol sampling technologies are inexpensive, easy to operate, and can continuously sample for days and even weeks which is not easily accomplished by active sampling devices. Although passive sampling devices are usually treated as qualitative tools, they still provide information about bioaerosol presence and diversity, especially over longer time scales. Overall, this review suggests that the use of passive bioaerosol samplers alongside active collection devices can aid researchers in developing a more comprehensive understanding of biological presence and dynamics, especially over extended time scales and multiple locations.

Electrostatic Dust Cloth: A Useful Passive Sampling Method When Assessing Exposure to Fungi Demonstrated in Studies Developed in Portugal (2018–2021)

Electrostatic dust cloths (EDC) have been widely used for microbiologic contamination assessment in different indoor and occupational environments. This paper reviews sixteen studies performed in Portugal between 2018 and 2021 for evaluating the exposure to microbiological agents and focusing on fungi using EDC as a passive sampling method. The findings suggest that EDC can be applied as a screening method for particulate matter-exposure assessment and as a complementary method to characterize microbial exposures in occupational environments. Overall, EDC should be included, side by side with other sampling methods, in sampling campaigns focused on exposure assessments due to the advantages such as the straightforward extraction protocol favoring the employment of different assays, which allows us to assess exposure to a wide range of microbial agents, and presents higher accuracy regarding the fungal diversity.

Accumulation of microorganisms on work clothes of workers collecting different types of waste - A feasibility study

Electrostatic dust cloths have previously been used to study microorganisms in settled dust by placing the cloths horizontally on surfaces (called Electrostatic Dust Collectors, EDC). In this study, we investigate whether the same cloths, henceforth called 'E-Cloths', can be used to study accumulation of microorganisms and endotoxin on workers' clothes. This was studied as current methods have limitations. It was examined for waste collection workers, as their work environment is associated with elevated exposure to microorganisms and endotoxin. Each worker received a kit with a T-shirt with an attached E-Cloth on the front, a instruction letter, and a questionnaire. Workers wore the T-shirts during the next two workdays. Unaffected by waste type collected, it was possible to measure the accumulation of bacteria, fungi, and endotoxin from the work environment on the E-Cloths. Geometric mean concentration of 9 × 10⁶ CFU bacteria/m², 1 × 10⁷ CFU fungi/m², and 4 × 10⁴ endotoxin units/m² were found. In total, 100 different bacterial and 25 fungal species were found. The genus Bacillus (with 18 species) and Brevibacterium aurantiacum were among the dominating bacteria. For fungi, Penicillium brevicompactum, P. commune, Penicillium italicum, and Aspergillus niger were most often found. Importantly, mainly environmental bacteria and fungi had accumulated on the E-Cloths and only few skin-related bacterial species were present, showing that accumulation had happened from the work exposure and not workers' skin. In conclusion, the T-shirts with an E-Cloth can be used as a self-administered method for measurement of accumulation of microorganisms and endotoxin from the work environment on waste collection workers' clothes.

Effectiveness of portable HEPA air cleaners on reducing indoor endotoxin, PM10, and coarse particulate matter in an agricultural cohort of children with asthma: A randomized intervention trial

We conducted a randomized trial of portable HEPA air cleaners in the homes of children age 6-12 years with asthma in the Yakima Valley, Washington. All families received asthma education while intervention families also received two HEPA cleaners (child's bedroom, living room). We collected 14-day integrated samples of endotoxin in settled dust and PM₁₀ and PM_10-2.5 in the air of the children's bedrooms at baseline and one-year follow-up, and used linear regression to compare follow-up levels, adjusting for baseline. Seventy-one families (36 HEPA, 35 control) completed the study. Baseline geometric mean (GSD) endotoxin loadings were 1565 (6.3) EU/m² and 2110 (4.9) EU/m² , respectively, in HEPA vs. control homes while PM₁₀ and PM_10-2.5 were 22.5 (1.9) μg/m³ and 9.5 (2.9) μg/m³ , respectively, in HEPA homes, and 19.8 (1.8) μg/m³ and 7.7 (2.0) μg/m³ , respectively, in control homes. At follow-up, HEPA families had 46% lower (95% CI, 31%-57%) PM₁₀ on average than control families, consistent with prior studies. In the best-fit heterogeneous slopes model, HEPA families had 49% (95% CI, 6%-110%) and 89% lower (95% CI, 28%-177%) PM_10-2.5 at follow-up, respectively, at 50th and 75th percentile baseline concentrations. Endotoxin loadings did not differ significantly at follow-up (4% lower, HEPA homes; 95% CI, -87% to 50%).

Correlation between levels of airborne endotoxin and heavy metals in subway environments in South Korea

This study aimed to evaluate the exposure levels and variation in airborne endotoxin and heavy metals such as aluminum, chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), zinc, and lead (Pb) in the three different South Korean subway environments (driver room, station office, and underground tunnel) and identify subway characteristics influencing endotoxin and heavy metals levels. Air samples were collected and analyzed using the kinetic Limulus Amebocyte Lysate assay and inductively coupled plasma mass spectrometers. The geometric mean was determined for endotoxin levels (0.693 EU/m³). It was also found that Fe (5.070 µg/m³) had the highest levels in subway environments while Pb (0.008 µg/m³) had the lowest levels. Endotoxin levels were higher in the underground tunnel and lower in the station office; the total heavy metal levels showed the same pattern with endotoxin levels. Endotoxins and total heavy metal levels were higher in the morning than at night. Positive correlations were found between endotoxin and Cr, Fe, Mn, and Ni levels. Given the correlation between airborne endotoxins and heavy metals, further studies with larger sample sizes are needed to identify the correlation between levels of airborne endotoxin and heavy metals.

Aspergillus collected in specific indoor settings: their molecular identification and susceptibility pattern

Exposure to Aspergillus conidia is an increased risk factor for the development of respiratory symptoms. The emergence of azole resistance in Aspergillus fumigatus is a major concern for the scientific community. The aim of this study was to perform the molecular identification of Aspergillus species collected from different occupational and non-occupational indoor settings and to study the azole susceptibility profile of the collected Fumigati isolates. The selected Aspergillus isolates were identified as belonging to the sections Fumigati, Nigri Versicolores, Terrei, Clavati and Nidulantes. All the Aspergillus fumigatus were screened for azole resistance using an agar media supplemented with itraconazole, voriconazole and posaconazole. None of the tested isolates showed resistance to those azoles. Knowledge of Aspergillus epidemiology in specific indoor environments allows a better risk characterization regarding Aspergillus burden. This study allowed the analysis of the molecular epidemiology and the determination of the susceptibility pattern of Aspergillus section Fumigati found in the studied indoor settings.

Loading Rates of Dust and Bioburden in Dwellings in an Inland City of Southern Europe

Sampling campaigns indoors have shown that occupants exposed to contaminated air generally exhibit diverse health outcomes. This study intends to assess the deposition rates of total settleable dust and bioburden in the indoor air of dwellings onto quartz fiber filters and electrostatic dust collectors (EDCs), respectively. EDC extracts were inoculated onto malt extract agar (MEA) and dichloran glycerol (DG18) agar-based media used for fungal contamination characterization, while tryptic soy agar (TSA) was applied for total bacteria assessment, and violet red bile agar (VRBA) for Gram-negative bacteria. Azole-resistance screening and molecular detection by qPCR was also performed. Dust loading rates ranged from 0.111 to 3.52, averaging 0.675 μg cm−2 day−1. Bacterial counts ranged from undetectable to 16.3 colony-forming units (CFU) m−2 day−1 and to 2.95 CFU m−2 day−1 in TSA and VRBA, respectively. Fungal contamination ranged from 1.97 to 35.4 CFU m−2 day−1 in MEA, and from undetectable to 48.8 CFU m−2 day−1 in DG18. Penicillium sp. presented the highest prevalence in MEA media (36.2%) and Cladosporium sp. in DG18 (39.2%). It was possible to observe: (a) settleable dust loadings and fungal contamination higher in dwellings with pets; (b) fungal species considered indicators of harmful fungal contamination; (c) Aspergillus section Candidi identified in supplemented media with voriconazole and posaconazole; (d) specific housing typologies and (e) specific housing characteristics influencing the microbial contamination.

Bioburden in sleeping environments from Portuguese dwellings

A wider characterization of indoor air quality during sleep is still lacking in the literature. This study intends to assess bioburden before and after sleeping periods in Portuguese dwellings through active methods (air sampling) coupled with passive methods, such as electrostatic dust cloths (EDC); and investigate associations between before and after sleeping and bioburden. In addition, and driven by the lack of information regarding fungi azole-resistance in Portuguese dwellings, a screening with supplemented media was also performed. The most prevalent genera of airborne bacteria identified in the indoor air of the bedrooms were Micrococcus (41%), Staphylococcus (15%) and Neisseria (9%). The major indoor bacterial species isolated in all ten studied bedrooms were Micrococcus luteus (30%), Staphylococcus aureus (13%) and Micrococcus varians (11%). Our results highlight that our bodies are the source of the majority of the bacteria found in the indoor air of our homes. Regarding air fungal contamination, Chrysosporium spp. presented the highest prevalence both in after the sleeping period (40.8%) and before the sleeping period (28.8%) followed by Penicillium spp. (23.47% morning; 23.6% night) and Chrysonilia spp. (12.4% morning; 20.3% night). Several Aspergillus sections were identified in air and EDC samples. However, none of the fungal species/strains (Aspergillus sections Fumigati, Flavi, Nidulantes and Circumdati) were amplified by qPCR in the analyzed EDC. The correlations observed suggest reduced susceptibility to antifungal drugs of some fungal species found in sleeping environments. Toxigenic fungal species and indicators of harmful fungal contamination were observed in sleeping environments.

Culture Media and Sampling Collection Method for Aspergillus spp. Assessment: Tackling the Gap between Recommendations and the Scientific Evidence

Culturing is still the most widely used method for determining fungal growth. Thus, is important to identify the most suitable culture media to assess Aspergillus spp. The aim of this study was to analyze data obtained from previous studies, aiming at identifying the most suitable culture media (malt extract agar (MEA) or dichloran-glycerol agar (DG18) to assess Aspergillus spp. isolation and growth. This study was conducted by using environmental samples (n = 1153). Most of the active sampling methods (air samples) were impacted directly onto both culture media. As for passive sampling methods, fungi were extracted from environmental matrices inoculated onto both media. Overall, total Aspergillus counts were higher in MEA (n = 617, 53.5%) than in DG18 (n = 536, 46.5%). Regarding Aspergillus sections, significant associations were detected with the media (χ2 (7) = 241.118, p < 0.001), the sampling approach (p < 0.001, 95% CI = (0.3 × 10−4), and the indoor environment (p < 0.001, 95% CI = (0.3 × 10−4)). As such, sampling approach and the culture media should be accurately selected when dealing with Aspergillus spp. exposure assessment.

Settleable Dust and Bioburden in Portuguese Dwellings

Monitoring campaigns in several buildings have shown that occupants exposed to contaminated indoor air generally exhibit diverse health symptoms. This study intends to assess settleable dust loading rates and bioburden in Portuguese dwellings by passive sampling onto quartz fiber filters and electrostatic dust cloths (EDCs), respectively. Settled dust collected by EDCs was analyzed by culture-based methods (including azole-resistance screening) and qPCR, targeting four different toxigenic Aspergillus sections (Flavi, Fumigati, Circumdati, and Nidulantes). Dust loading rates and bioburden showed higher variability in the summer season. In both seasons, Penicillium sp. was the one with the highest prevalence (59.1% winter; 58.1% summer), followed by Aspergillus sp. in winter (13.0%). Fungal contamination increased in the winter period, while bacterial counts decreased. Aspergillus sections Circumdati and Nidulantes, detected in voriconazole supplemented media, and Aspergillus sections Fumigati and Nidulantes, detected by molecular tools, were found in the winter samples. This study reinforces the importance of applying: (a) Passive sampling methods in campaigns in dwellings; (b) two different culture media (MEA and DG18) to assess fungi; (c) in parallel, molecular tools targeting the most suitable indicators of fungal contamination; and (d) azole resistance screening to unveil azole resistance detection in fungal species.

Lung function of primary cooks using LPG or biomass and the effect of particulate matter on airway epithelial barrier integrity

BACKGROUND

Cooks exposed to biomass fuel experience increased risk of respiratory disease and mortality. We sought to characterize lung function and environmental exposures of primary cooking women using two fuel-types in southeastern India, as well as to investigate the effect of particulate matter (PM) from kitchens on human airway epithelial (HAE) cells in vitro.

METHODS

We assessed pre- and post-bronchodilator lung function on 25 primary female cooks using wood biomass or liquified petroleum gas (LPG), and quantified exposures from 34 kitchens (PM_2.5, PM < 40 μm, black carbon, endotoxin, and PM metal and bacterial content). We then challenged HAE cells with PM, assessing its cytotoxicity to small-airway cells (A549) and its effect on: transepithelial conductance and macromolecule permeability (NuLi cells), and antimicrobial activity (using airway surface liquid, ASL, from primary HAE cells).

RESULTS

Lung function was impaired in cooks using both fuel-types. 60% of participants in both fuel-types had respiratory restriction (post bronchodilator FEV₁/FVC>90). The remaining 40% in the LPG group had normal spirometry (post FEV₁/FVC = 80-90), while only 10% of participants in the biomass group had normal spirometry, and the remaining biomass cooks (30%) had respiratory obstruction (post FEV₁/FVC<80). Significant differences were found in environmental parameters, with biomass kitchens containing greater PM_2.5, black carbon, zirconium, arsenic, iron, vanadium, and endotoxin concentrations. LPG kitchens tended to have more bacteria (p = 0.14), and LPG kitchen PM had greater sulphur concentrations (p = 0.02). In vitro, PM induced cytotoxicity in HAE A549 cells in a dose-dependent manner, however the effect was minimal and there were no differences between fuel-types. PM from homes of participants with a restrictive physiology increased electrical conductance of NuLi HAE cells (p = 0.06) and decreased macromolar permeability (p ≤ 0.05), while PM from homes of those with respiratory obstruction tended to increase electrical conductance (p = 0.20) and permeability (p = 0.07). PM from homes of participants with normal spirometry did not affect conductance or permeability. PM from all homes tended to inhibit antimicrobial activity of primary HAE cell airway surface liquid (p = 0.06).

CONCLUSIONS

Biomass cooks had airway obstruction, and significantly greater concentrations of kitchen environmental contaminants than LPG kitchens. PM from homes of participants with respiratory restriction and obstruction altered airway cell barrier function, elucidating mechanisms potentially responsible for respiratory phenotypes observed in biomass cooks.

Assessment of Children’s Potential Exposure to Bioburden in Indoor Environments

The exposure to particles and bioaerosols has been associated with the increase in health effects in children. The objective of this study was to assess the indoor exposure to bioburden in the indoor microenvironments more frequented by children. Air particulate matter (PM) and settled dust were sampled in 33 dwellings and four schools with a medium volume sampler and with a passive method using electrostatic dust collectors (EDC), respectively. Settled dust collected by EDC was analyzed by culture-based methods (including azole resistance profile) and using qPCR. Results showed that the PM2.5 and PM10 concentrations in classrooms (31.15 μg/m3 and 57.83 μg/m3, respectively) were higher than in homes (15.26 μg/m3 and 18.95 μg/m3, respectively) and highly exceeded the limit values established by the Portuguese legislation for indoor air quality. The fungal species most commonly found in bedrooms was Penicillium sp. (91.79%), whereas, in living rooms, it was Rhizopus sp. (37.95%). Aspergillus sections with toxigenic potential were found in bedrooms and living rooms and were able to grow on VOR. Although not correlated with PM, EDC provided information regarding the bioburden. Future studies, applying EDC coupled with PM assessment, should be implemented to allow for a long-term integrated sample of organic dust.

The effects of waste sorting in environmental microbiome, THP-1 cell viability and inflammatory responses

Workers in the waste sorting industry are exposed to diverse bioaerosols. Characterization of these bioaerosols is necessary to more accurately assess the health risks of exposure. The use of high-throughput DNA sequencing for improved analysis of microbial composition of bioaerosols, in combination with their in vitro study in relevant cell cultures, represents an important opportunity to find answers on the biological effects of bioaerosols. This study aimed to characterize by high-throughput sequencing the biodiversity present in complex aerosol mixtures retained in forklift air conditioning filters of a waste-sorting industry and its effects on cytotoxicity and secretion of proinflammatory cytokines in vitro using human macrophages derived from monocytic THP-1 cells. Seventeen filters from the filtration system from forklifts operating in one waste sorting facility and one control filter (similar filter without prior use) were analyzed using high-throughput sequencing and toxicological tests in vitro. A trend of positive correlation was seen between the number of bacterial and fungal OTUs (r = 0.47, p = 0.06). Seven filters (39%) exhibited low or moderate cytotoxicity (p < 0.05). The highest cytotoxic responses had a reduction in cell viability between 17 and 22%. Filter samples evoked proinflammatory responses, especially the production of TNFα. No significant correlation was found between fungal richness and inflammatory responses in vitro. The data obtained stress the need of thorough exposure assessment in waste-sorting industry and to take immunomodulatory properties into consideration for bioaerosols hazard characterization. The broad spectrum of microbial contamination detected in this study demonstrates that adequate monitoring of bioaerosol exposure is necessary to evaluate and minimize risks. The combined techniques can support the implementation of effective environmental monitoring programs of public and occupational health importance.

Home Assessment of Indoor Microbiome (HAIM) in Relation to Lower Respiratory Tract Infections among Under-Five Children in Ibadan, Nigeria: The Study Protocol

The association between household air pollution and lower respiratory tract infections (LRTI) among children under five years of age has been well documented; however, the extent to which the microbiome within the indoor environment contributes to this association is uncertain. The home assessment of indoor microbiome (HAIM) study seeks to assess the abundance of indoor microbiota (IM) in the homes of under-five children (U-5Cs) with and without LRTI. HAIM is a hospital- and community-based study involving 200 cases and 200 controls recruited from three children’s hospitals in Ibadan, Nigeria. Cases will be hospital-based patients with LRTI confirmed by a pediatrician, while controls will be community-based participants, matched to cases on the basis of sex, geographical location, and age (±3 months) without LRTI. The abundance of IM in houses of cases and controls will be investigated using active and passive air sampling techniques and analyzed by qualitative detection of bacterial 16SrRNA gene (V3–V4), fungal ITS1 region, and viral RNA sequencing. HAIM is expected to elucidate the relationship between exposure to IM and incidence of LRTI among U-5Cs and ultimately provide evidence base for strategic interventions to curtail the burgeoning burden of LRTI on the subcontinent.

Indoor Microbiome: Quantification of Exposure and Association with Geographical Location, Meteorological Factors, and Land Use in France

The indoor microbial community is a mixture of microorganisms resulting from outdoor ecosystems that seed the built environment. However, the biogeography of the indoor microbial community is still inadequately studied. Dust from more than 3000 dwellings across France was analyzed by qPCR using 17 targets: 10 molds, 3 bacteria groups, and 4 mites. Thus, the first spatial description of the main indoor microbial allergens on the French territory, in relation with biogeographical factors influencing the distribution of microorganisms, was realized in this study. Ten microorganisms out of 17 exhibited increasing abundance profiles across the country: Five microorganisms (Dermatophagoïdes pteronyssinus, Dermatophagoïdes spp., Streptomyces spp., Cladosporium sphaerospermum, Epicoccum nigrum) from northeast to southwest, two (Cryptococcus spp., Alternaria alternata) from northwest to southeast, Mycobacteria from east to west, Aspergillus fumigatus from south to north, and Penicillium chrysogenum from south to northeast. These geographical patterns were partly linked to climate and land cover. Multivariate analysis showed that composition of communities seemed to depend on landscapes, with species related to closed and rather cold and humid landscapes (forests, located in the northeast) and others to more open, hot, and dry landscapes (herbaceous and coastal regions, located in the west). This study highlights the importance of geographical location and outdoor factors that shape communities. In order to study the effect of microorganisms on human health (allergic diseases in particular), it is important to identify biogeographic factors that structure microbial communities on large spatial scales and to quantify the exposure with quantitative tools, such as the multi-qPCR approach.

Exposure assessment in one central hospital: A multi-approach protocol to achieve an accurate risk characterization

The bioburden in a Hospital building originates not only from patients, visitors and staff, but is also disseminated by several indoor hospital characteristics and outdoor environmental sources. This study intends to assess the exposure to bioburden in one central Hospital with a multi-approach protocol using active and passive sampling methods. The microbial contamination was also characterized through molecular tools for toxigenic species, antifungal resistance and mycotoxins and endotoxins profile. Two cytotoxicity assays (MTT and resazurin) were conducted with two cell lines (Calu-3 and THP-1), and in vitro pro-inflammatory potential was assessed in THP-1 cell line. Out of the 15 sampling locations 33.3% did not comply with Portuguese legislation regarding bacterial contamination, whereas concerning fungal contamination 60% presented I/O > 1. Toxigenic fungal species were observed in 27% of the sampled rooms (4 out of 15) and qPCR analysis successfully amplified DNA from the Aspergillus sections Flavi and Fumigati, although mycotoxins were not detected. Growth of distinct fungal species was observed on Sabouraud dextrose agar with triazole drugs, such as Aspergillus section Versicolores on 1 mg/L VORI. The highest concentrations of endotoxins were found in settled dust samples and ranged from 5.72 to 23.0 EU.mg^-1. While a considerable cytotoxic effect (cell viability < 30%) was observed in one HVAC filter sample with Calu-3 cell line, it was not observed with THP-1 cell line. In air samples a medium cytotoxic effect (61-68% cell viability) was observed in 3 out of 15 samples. The cytokine responses produced a more potent average cell response (46.8 ± 12.3 ρg/mL IL-1β; 90.8 ± 58.5 ρg/mL TNF-α) on passive samples than air samples (25.5 ± 5.2 ρg/mL IL-1β and of 19.4 ± 5.2 ρg/mL TNF-α). A multi-approach regarding parameters to assess, sampling and analysis methods should be followed to characterize the biorburden in the Hospital indoor environment. This study supports the importance of considering exposure to complex mixtures in indoor environments.

Household dampness and microbial exposure related to allergy and respiratory health in Danish adults

Background: Indoor dampness has consistently been associated with respiratory symptoms and exacerbations. The causal mechanisms may involve increased microbial exposures. However, the evidence regarding the influence of indoor microbial exposures under damp- and non-damp conditions on the risk of asthma and allergy has been inconclusive. Objective: The aim of this study was to investigate the association between dampness and microbial exposure with allergy and respiratory health in Danish adults using a cross-sectional design. Methods: From 1,866 participants of the Health2006 cohort, we selected three non-overlapping groups: 196 at random, 107 with confirmed atopy, and 99 without atopy. Bedroom dust was sampled using electrostatic dust fall collectors and analysed for endotoxin, β-(1,3)-D-glucan, 19 microbial species or groups, and total fungal load. Household moisture-related problems and asthma were self-reported by questionnaire. Atopy was determined by skin-prick-testing and lung function was measured by spirometry. Results: Household moisture damage was positively associated with asthma outcomes, although this was statistically significant only in atopics for self-reported asthma (odds ratio (OR) 3.52; 95%CI 1.01-12.7). Mould odor was positively associated with wheezing (OR 6.05; 95%CI 1.19-30.7) in atopics. Inconsistent associations were found for individual microbial exposures and health outcomes. Inverse associations were observed between microbial diversity and rhinitis in the random sample and both doctor-diagnosed and self-reported asthma in non-atopics. Conclusions: In conclusion, our findings suggest that household moisture damage may increase the risk of asthma and wheeze with mould odor in atopics. In addition, asthma and allergy may be affected by the indoor microbial composition in urban domestic environments. Further studies are needed to identify and understand the causal agents and underlying mechanisms behind the potential effects of environmental microbial exposure on human health.

Occupational Exposures to Organic Dust in Irish Bakeries and a Pizzeria Restaurant

For decades, occupational exposure to flour dust has been linked to a range of respiratory diseases, including occupational asthma, thought to result from exposure to fungi present in the flour. Antifungal resistance is of increasing prevalence in clinical settings, and the role of occupational and environmental exposures, particularly for specific fungal species, is of concern. Occupational exposure to flour dust can occur in a range of occupational settings, however, few studies have focused on restaurant workers. The objective of this study was to measure occupational exposure to flour and microbial contamination, including azole resistance screening, in two small commercial bakeries and in a pizzeria. Personal full shift inhalable dust measurements were collected from workers, and were analyzed for inhalable dust and fungi, bacteria, azole resistance, and mycotoxins. Samples of settled dust were collected, and electrostatic dust cloths (EDC) were deployed and analyzed for microbial contamination, including azole resistance screening, and mycotoxins. Geometric mean exposures of 6.5 mg m-³ were calculated for inhalable dust, however, exposures of up to 18.30 mg m-³ were measured-70% of personal exposure measurements exceeded the occupational exposure limit for flour dust of 1.0 mg m-³. The air and EDC fungal counts were similar to those reported in previous studies for similar occupational environments. The fungi were dominated by Penicillium genera, however Aspergillus genera, including Fumigati and Flavi sections, were observed using culture-based methods, and the Fumigati section was also observed by molecular tools. Both Aspergillus sections were identified on the azole resistance screening. Mycotoxins were also detected in the settled dust samples, dominated by deoxynivalenol (DON). The role of environmental exposure in both the development of antimicrobial resistance and the total mycotoxin body burden is a growing concern; therefore, the presence of azole-resistant fungi and mycotoxin contamination, although low in magnitude, is of concern and warrants further investigation.

Measurement of dust-borne MRSA in pig farms using different approaches

AIMS

To obtain knowledge about (i) how to sample airborne methicillin-resistant Staphylococcus aureus (MRSA) and dust in the pig farm environment including effects of sampler on (a) measured exposure, (b) MRSA survival and (c) spatial and temporal variation in exposure, and (ii) the association between exposure to MRSA, dust and optical density OD.

METHODS AND RESULTS

Airborne dust was sampled on five pig farms using five active and one passive samplers. Staphylococcus aureus and MRSA (as a subset of S. aureus) were quantified using selective agar media and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The Andersen sampler, electrostatic dust collectors (EDC), and Gesamtstaubprobenahme (GSP) and Institute of Occupational Medicine samplers with polycarbonate or Teflon filters were applicable for sampling airborne MRSA. The half-life of MRSA was not reduced by active sampling. A significant correlation was found between dust and S. aureus exposure within, but not between, farm section and farms. A significant spatial and temporal variation in dust and MRSA exposure was found within a stable. The dust sampling rate and the concentration of MRSA in the sampled dust decreased after 5 days of sampling.

CONCLUSION

Sampling using the GSP can be performed for 1 h without affecting the following half-life of MRSA. Sampling for MRSA using the EDC should not exceed 3 days due to overloading and the die-off of MRSA. The measurement of OD may be used as a proxy measure for dust exposure. To obtain knowledge about potential exposure, samples should be taken repeatedly and in different areas within a stable section.

SIGNIFICANCE AND IMPACT OF THE STUDY

Sampling method, sampling time and number of samples taken, but not force of airflow on the filter, influence the measured potential exposure to MRSA and dust.

A comparison of methods used to unveil the genetic and metabolic pool in the built environment

BACKGROUND

A majority of indoor residential microbes originate from humans, pets, and outdoor air and are not adapted to the built environment (BE). Consequently, a large portion of the microbes identified by DNA-based methods are either dead or metabolically inactive. Although many exceptions have been noted, the ribosomal RNA fraction of the sample is more likely to represent either viable or metabolically active cells. We examined methodological variations in sample processing using a defined, mock BE microbial community to better understand the scope of technique-based vs. biological-based differences in both ribosomal transcript (rRNA) and gene (DNA) sequence community analysis. Based on in vitro tests, a protocol was adopted for the analysis of the genetic and metabolic pool (DNA vs. rRNA) of air and surface microbiomes within a residential setting.

RESULTS

We observed differences in DNA/RNA co-extraction efficiency for individual microbes, but overall, a greater recovery of rRNA using FastPrep (> 50%). Samples stored with various preservation methods at - 80°C experienced a rapid decline in nucleic acid recovery starting within the first week, although post-extraction rRNA had no significant degradation when treated with RNAStable. We recommend that co-extraction samples be processed as quickly as possible after collection. The in vivo analysis revealed significant differences in the two components (genetic and metabolic pool) in terms of taxonomy, community structure, and microbial association networks. Rare taxa present in the genetic pool showed higher metabolic potential (RNA:DNA ratio), whereas commonly detected taxa of outdoor origins based on DNA sequencing, especially taxa of the Sphingomonadales order, were present in lower relative abundances in the viable community.

CONCLUSIONS

Although methodological variations in sample preparations are high, large differences between the DNA and RNA fractions of the total microbial community demonstrate that direct examination of rRNA isolated from a residential BE microbiome has the potential to identify the more likely viable or active portion of the microbial community. In an environment that has primarily dead and metabolically inactive cells, we suggest that the rRNA fraction of BE samples is capable of providing a more ecologically relevant insight into the factors that drive indoor microbial community dynamics.

Concentrations of Staphylococcus species in indoor air as associated with other bacteria, season, relative humidity, air change rate, and S. aureus-positive occupants

The aim of this study was to obtain knowledge about concentrations of Staphylococcus aureus, MRSA (methicillin-resistant S. aureus), and other Staphylococcus species in indoor air in Greater Copenhagen and about factors affecting the concentrations. The effects of season, temperature, relative humidity, air change rate (ACR), other bacterial genera, area per occupant, and presence of S. aureus-positive occupants were studied. In samples from 67 living rooms, S. hominis, S. warneri, S. epidermidis, and S. capitis were found in 13-25%; S. saprophyticus, S. cohnii, and S. pasteuri in 5-10%; and S. lugdunensis, S. haemolyticus, S. caprae, S. equorum, S. kloosii, S. pettenkoferi, S. simulans, and S. xylosus in less than 3%. Staphylococcus aureus were found in two of 67 living rooms: spa type t034 (an MRSA) was recovered from a farmhouse, while spa type t509 was found in an urban home. Two species, S. equorum and S. kloosii, were found only in the farmhouse. Staphylococcus was significantly associated with season with lowest concentration and richness in winter. Genera composition was associated with ACR with smaller fractions of Staphylococcus at higher ACR, while richness was significantly and negatively associated with area per occupant. Concentration of Staphylococcus correlated positively with the total concentration of bacteria, but negatively with the total concentration of other bacteria. The concentration of Staphylococcus was not significantly associated with concentrations of the other abundant genera Bacillus, Kocuria, and Micrococcus. In offices with S. aureus-positive occupants, airborne S. aureus was not found. In conclusion, Staphylococcus species constitute a considerable proportion of the airborne bacteria in the studied homes and offices. However, both S. aureus and MRSA had very low prevalence during all seasons. Thus, transmission of S. aureus and MRSA through the air in living rooms in Copenhagen is expected to be limited. The negative associations between ACR and the fraction Staphylococcus constituted out of total bacteria, and between area per occupant and Staphylococcus richness indicate that it might be possible to affect the presence of airborne Staphylococcus in homes.

Assessment of occupational exposure to azole resistant fungi in 10 Portuguese bakeries

Occupational exposure to bioaerosols resulting from handling of flour dust and raw materials in bakeries is associated with health problems. The emergence of azole-resistant fungal species in the environment is thought to be related with the use of azole fungicides in cereal crops and prevention of postharvest spoilage. As raw materials used in bakeries are commonly exposed to azoles, we investigated the mycobiota and azole-resistant fungi prevalence in this occupational environment. Ten Portuguese bakeries were assessed through electrostatic dust cloth (EDC, n = 27), settled dust (n = 7), and raw material (n = 26) samples. Samples were inoculated in malt extract agar (2%) (MEA) with chloramphenicol (0.05 g/L) and in dichloran glycerol (DG18), and onto Saboraud screening media supplemented with 4 mg/L itraconazole, 1 mg/L voriconazole, or 0.5 mg/L posaconazole, and incubated for 3-5 days at 27 °C. Except for one out of the ten analyzed bakeries, Cladosporium sp., Penicillium sp., and Aspergillus sp. were the most prevalent fungi identified. Aspergillus sp. and Mucorales order were identified in raw materials with both media, whereas Penicillium sp. was identified in DG18 only. Azole-resistant species were identified in the environment (EDC) and, to a lower extent, in raw materials, including Aspergillus sp. and Mucorales. The presence of azole-resistant fungal species in bakeries represents an occupational risk for workers. This study proposes complementary sampling methods for the evaluation of occupational exposure to mycobiota, and highlights the importance of studying the prevalence of azole-resistant strains in specific occupational environments.

No apparent transmission of livestock-associated methicillin-resistant Staphylococcus aureus CC398 in a survey of staff at a regional Danish hospital

Background

In recent years, livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) multi locus sequence type CC398 has spread widely in the livestock production in Europe. The rates of LA-MRSA in hospitals have been found to be largely determined by contact to and density of livestock in the area.

Methods

This is a cross sectional study of the prevalence of LA-MRSA among hospital staff in a Danish hospital situated in a livestock production region. We analysed nasal swabs, air and dust samples for the presence of MRSA using PCR and mass spectrometry.

Results

Of 1745 employees, 545 (31%) contributed nasal swabs. MRSA was not detected in any participant, nor was it detected in air or dust at the hospital or in houses of employees living on farms. Four percent of the participants had contact to pigs either directly or through household members. LA-MRSA was detected in two of 26 samples from animal sheds, both of them from pig farms. The participation rate was relatively low, but participants were representative for the source population with regards to animal contact and job titles.

Conclusions

The study suggests a low point prevalence of LA-MRSA carriage in Danish hospital staff even in regions where livestock production is dense. Should more studies confirm our findings we see no need for additional hospital precautions towards LA-MRSA in Denmark at the moment. We think that our data might reduce potential stigmatization of hospital workers with contact to LA-MRSA positive farms at their work places and in their communities.

Electronic supplementary material

The online version of this article (10.1186/s13756-017-0284-y) contains supplementary material, which is available to authorized users.

The unexpected role of bioaerosols in the Oxidative Potential of PM

Bioaerosols represent up to 15–25% of PM by mass, but there is currently no assessment of their impact on Oxidative Potential (OP), or capacity of particulate matter (PM) to produce damaging oxidative reactions in the human lungs. Here, the OP of selected bioaerosols (bacteria cells vs fungal spores) was assessed through the cell-free DTT assay. Results show that bioaerosols induce Reactive Oxygen Species (ROS) production, varying along the microorganism type, species, and concentration. Fungal spores show up to 10 times more ROS generation than bacterial cells. At the highest concentrations, fungal spores present as much oxidative reactivity as the most redox-active airborne chemicals (Copper, Naphtoquinone). Moreover, bioaerosols substantially influence OP of ambient PM and that of its chemical constituents: in presence of A. fumigatus spores, the OP of Cu/NQ is increased by a factor of 2 to 5, whereas, 10⁴ and 10⁵  S. epidermidis bacterial cells.mL⁻¹ halves the OP of Cu/NQ. Finally, viable and gamma-rays-killed model bioaerosols present similar oxidative reactivity, suggesting a metabolism-independent cellular mechanism. These results reveal the importance of bioaerosols for PM reactivity. PM toxicity can be modified due to bioaerosols contribution or by their ability to modulate the OP of toxic chemicals present in PM.

Assessment of airborne bacteria and noroviruses in air emission from a new highly-advanced hospital wastewater treatment plant

Exposure to bioaerosols can pose a health risk to workers at wastewater treatment plants (WWTPs) and to habitants of their surroundings. The main objective of this study was to examine the presence of harmful microorganisms in the air emission from a new type of hospital WWTP employing advanced wastewater treatment technologies. Air particle measurements and sampling of inhalable bacteria, endotoxin and noroviruses (NoVs) were performed indoor at the WWTP and outside at the WWTP ventilation air exhaust, downwind of the air exhaust, and upwind of the WWTP. No significant differences were seen in particle and endotoxin concentrations between locations. Bacterial concentrations were comparable or significantly lower in the exhaust air than inside the WWTP and in the upwind reference. Bacterial isolates were identified using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry. In total, 35 different bacterial genera and 64 bacterial species were identified in the air samples. Significantly higher genus and species richness was found with an Andersen Cascade Impactor compared with filter-based sampling. No pathogenic bacteria were found in the exhaust air. Streptomyces was the only bacterium found in the air both inside the WWTP and at the air emission, but not in the upwind reference. NoV genomes were detected in the air inside the WWTP and at the air exhaust, albeit in low concentrations. As only traces of NoV genomes could be detected in the exhaust air they are unlikely to pose a health risk to surroundings. Hence, we assess the risk of airborne exposure to pathogenic bacteria and NoVs from the WWTP air emission to surroundings to be negligible. However, as a slightly higher NoV concentration was detected inside the WWTP, we cannot exclude the possibility that exposure to airborne NoVs can pose a health risk to susceptible to workers inside the WWTP, although the risk may be low.

Potentially harmful secondary metabolites produced by indoor Chaetomium species on artificially and naturally contaminated building materials

The presence of the fungal genus Chaetomium and its secondary metabolites in indoor environments is suspected to have a negative impact on human health and well-being. About 200 metabolites have been currently described from Chaetomium spp., but only the bioactive compound group, chaetoglobosins, have been screened for and thus detected in buildings. In this study, we used a liquid chromatography high-resolution mass spectrometry approach to screen both artificially and naturally infected building materials for all the Chaetomium metabolites described in the literature. Pure agar cultures were also investigated to establish differences between metabolite production in vitro and on building materials as well as in comparison with non-indoor reference strains. On building materials, six different chaetoglobosins were detected in total concentrations of up to 950 mg/m² from Chaetomium globosum along with three different chaetoviridins/chaetomugilins in concentrations up to 200 mg/m² . Indoor Chaetomium spp. preferred wood-based materials over gypsum, both in terms of growth rate and metabolite production. Cochliodones were detected for the first time on all building materials infected by both C. globosum and Chaetomium elatum and are thus candidates as Chaetomium biomarkers. No sterigmatocystin was produced by Chaetomium spp. from indoor environment.

A critical review of approaches and limitations of inhalation bioavailability and bioaccessibility of metal(loid)s from ambient particulate matter or dust

Inhalation of metal(loid)s in ambient particulate matter (APM) represents a significant exposure pathway to humans. Although exposure assessment associated with this pathway is currently based on total metal(loid) content, a bioavailability (i.e. absorption in the systemic circulation) and/or bioaccessibility (i.e. solubility in simulated lung fluid) based approach may more accurately quantify exposure. Metal(loid) bioavailability-bioaccessibility assessment from APM is inherently complex and lacks consensus. This paper reviews the discrepancies that impede the adoption of a universal protocol for the assessment of inhalation bioaccessibility. Exposure assessment approaches for in-vivo bioavailability, in-vitro cell culture and in-vitro bioaccessibility (composition of simulated lungs fluid, physico-chemical and methodological considerations) are critiqued in the context of inhalation exposure refinement. An important limitation of bioavailability and bioaccessibility studies is the use of considerably higher than environmental metal(loid) concentration, which diminishing their relevance to human exposure scenarios. Similarly, individual metal(loid) studies have been criticised due to complexities of APM metal(loid) mixtures which may impart synergistic or antagonistic effects compared to single metal(loid) exposure. Although a number of different simulated lung fluid (SLF) compositions have been used in metal(loid) bioaccessibility studies, information regarding the comparative leaching efficiency among these different SLF and comparisons to in-vivo bioavailability data is lacking. In addition, the particle size utilised is often not representative of what is deposited in the lungs while assay parameters (extraction time, solid to liquid ratio, temperature and agitation) are often not biologically relevant. Research needs are identified in order to develop robust in-vitro bioaccessibility protocols for the assessment or prediction of metal(loid) bioavailability in APM for the refinement of inhalation exposure.

Electrostatic dust collectors compared to inhalable samplers for measuring endotoxin concentrations in farm homes

Paired electrostatic dust collectors (EDCs) and daily, inhalable button samplers (BS) were used concurrently to sample endotoxin in 10 farm homes during 7-day periods in summer and winter. Winter sampling included an optical particle counter (OPC) to measure PM2.5 and PM2.5-10 . Electrostatic dust collectors and BS filters were analyzed for endotoxin using the kinetic chromogenic Limulus amebocyte lysate assay. Optical particle counter particulate matter (PM) data were divided into two PM categories. In summer, geometric mean (geometric standard deviation) endotoxin concentrations were 0.82 EU/m(3) (2.7) measured with the BS and 737 EU/m(2) (1.9) measured with the EDC. Winter values were 0.52 EU/m(3) (3.1) for BS and 538 EU/m(2) (3.0) for EDCs. Seven-day endotoxin values of EDCs were highly correlated with the 7-day BS sampling averages (r = 0.70; P < 0.001). Analysis of variance indicated a 2.4-fold increase in EDC endotoxin concentrations for each unit increase of the ratio of PM2.5 to PM2.5-10 . There was also a significant correlation between BS and EDCs endotoxin concentrations for winter (r = 0.67; P < 0.05) and summer (r = 0.75; P < 0.05). Thus, EDCs sample comparable endotoxin concentrations to BS, making EDCs a feasible, easy to use alternative to BS for endotoxin sampling.

Waste Workers’ Exposure to Airborne Fungal and Bacterial Species in the Truck Cab and During Waste Collection

A large number of people work with garbage collection, and exposure to microorganisms is considered an occupational health problem. However, knowledge on microbial exposure at species level is limited. The aim of the study was to achieve knowledge on waste collectors’ exposure to airborne inhalable fungal and bacterial species during waste collection with focus on the transport of airborne microorganisms into the truck cab. Airborne microorganisms were collected with samplers mounted in the truck cab, on the workers’ clothes, and outdoors. Fungal and bacterial species were quantified and identified. The study showed that the workers were exposed to between 112 and 4.8×10⁴ bacteria m⁻³ air and 326 and 4.6×10⁴ fungi m⁻³ air. The personal exposures to bacteria and fungi were significantly higher than the concentrations measured in the truck cabs and in the outdoor references. On average, the fungal and bacterial concentrations in truck cabs were 111 and 7.7 times higher than outdoor reference measurements. In total, 23 fungal and 38 bacterial species were found and identified. Most fungal species belonged to the genus Penicillium and in total 11 Penicillium species were found. Identical fungal species were often found both in a personal sample and in the same person’s truck cab, but concentrations were on average 27 times higher in personal samples. Concentrations of fungal and bacterial species found only in the personal samples were lower than concentrations of species also found in truck cabs. Skin-related bacteria constituted a large fraction of bacterial isolates found in personal and truck cab samples. In total, six Staphylococcus species were found. In outdoor samples, no skin-related bacteria were found. On average, concentrations of bacterial species found both in the truck cab and personal samples were 77 times higher in personal samples than in truck cab samples. In conclusion, high concentrations of fungi were found in truck cabs, but the highest concentrations were found in personal samples; fungal and bacterial species found in high concentrations in personal samples were also found in truck cabs, but in lower concentrations indicating that both fungi and bacteria are transported by the workers into the truck cab, and are subsequently aerosolized in the truck cab.

Generation and Characterization of Indoor Fungal Aerosols for Inhalation Studies

In the indoor environment, people are exposed to several fungal species. Evident dampness is associated with increased respiratory symptoms. To examine the immune responses associated with fungal exposure, mice are often exposed to a single species grown on an agar medium. The aim of this study was to develop an inhalation exposure system to be able to examine responses in mice exposed to mixed fungal species aerosolized from fungus-infested building materials. Indoor airborne fungi were sampled and cultivated on gypsum boards. Aerosols were characterized and compared with aerosols in homes. Aerosols containing 10⁷ CFU of fungi/m³ air were generated repeatedly from fungus-infested gypsum boards in a mouse exposure chamber. Aerosols contained Aspergillus nidulans, Aspergillus niger, Aspergillus ustus, Aspergillus versicolor, Chaetomium globosum, Cladosporiumherbarum, Penicillium brevicompactum, Penicillium camemberti, Penicillium chrysogenum, Penicillium commune, Penicillium glabrum, Penicillium olsonii, Penicillium rugulosum, Stachybotrys chartarum, and Wallemia sebi. They were all among the most abundant airborne species identified in 28 homes. Nine species from gypsum boards and 11 species in the homes are associated with water damage. Most fungi were present as single spores, but chains and clusters of different species and fragments were also present. The variation in exposure level during the 60 min of aerosol generation was similar to the variation measured in homes. Through aerosolization of fungi from the indoor environment, cultured on gypsum boards, it was possible to generate realistic aerosols in terms of species composition, concentration, and particle sizes. The inhalation-exposure system can be used to study responses to indoor fungi associated with water damage and the importance of fungal species composition.

Seasonal variation in airborne endotoxin levels in indoor environments with different micro-environmental factors in Seoul, South Korea

This study evaluated the variation over a year in airborne endotoxin levels in the indoor environment of five university laboratories in Seoul, South Korea, and examined the micro-environmental factors that influenced endotoxin levels. These included temperature, relative humidity, CO2, CO, illumination, and wind velocity. A total of 174 air samples were collected and analyzed using the kinetic limulus amebocyte lysate assay. Endotoxin levels ranged from <0.001 to 8.90EU/m(3), with an overall geometric mean of 0.240EU/m(3). Endotoxin levels showed significantly negative correlation with temperature (r=-0.529, p<0.001), CO2 (r=-0.213, p<0.001) and illumination (r=-0.538, p<0.001). Endotoxin levels tended to be higher in winter. Endotoxin levels in laboratories with rabbits were significantly higher than those of laboratories with mice. Multivariate regression analysis showed that the environmental factors affecting endotoxin levels were temperature (coefficient=-0.388, p<0.001) and illumination (coefficient=-0.370, p<0.001). Strategies aimed at reducing airborne endotoxin levels in the indoor environments may be most effective if they focus on illumination.

Performance of electrostatic dust collectors (EDCs) for endotoxin assessment in homes: Effect of mailing, placement, heating, and electrostatic charge

Electrostatic Dust Collectors (EDCs) are in use for passive sampling of bioaerosols, but particular aspects of their performance have not yet been evaluated. This study investigated the effect of mailing EDCs on endotoxin loading and the effect of EDC deployment in front of, and away from, heated ventilation on endotoxin sampling. Endotoxin sampling efficiency of heated and unheated EDC cloths was also evaluated. Cross-country express mailing of dust-spiked EDCs yielded no significant changes in endotoxin concentrations compared to dust-only samples for both high-spiked EDCs (p = 0.30) and low-spiked EDCs (p = 0.36). EDCs were also deployed in 20 identical apartments with one EDC placed in front of the univent heater in each apartment and contemporaneous EDC placed on the built-in bookshelf in each apartment. The endotoxin concentrations were significantly different (p = 0.049) indicating that the placement of EDC does impact endotoxin sampling. Heated and unheated EDCs were deployed for 7 days in pairs in farm homes. There was a significant difference between endotoxin concentrations (p = 0.027) indicating that heating EDCs may diminish their electrostatic capabilities and impact endotoxin sampling. The last study investigated the electrostatic charge of 12 heated and 12 unheated EDC cloths. There was a significant difference in charge (p = 0.009) which suggests that heating EDC cloths may make them less effective for sampling. In conclusion, EDCs can be mailed to and from deployment sites, EDC placement in relationship to ventilation is crucial, and heating EDCs reduces their electrostatic charge which may diminish their endotoxin sampling capabilities.

Passive dust collectors for assessing airborne microbial material

BACKGROUND

Settled airborne dust is used as a surrogate for airborne exposure in studies that explore indoor microbes. In order to determine whether detecting differences in dust environments would depend on the sampler type, we compared different passive, settled dust sampling approaches with respect to displaying qualitative and quantitative aspects of the bacterial and fungal indoor microbiota.

RESULTS

Settled dust sampling approaches-utilizing plastic petri dishes, TefTex material, and electrostatic dustfall collectors (EDCs)-were evaluated in indoor spaces in the USA and Finland and in an experimental chamber study. The microbial content was analyzed with quantitative PCR (qPCR) to quantify total bacterial and fungal biomass and through high-throughput sequencing to examine bacterial community composition. Bacterial composition and diversity were similar within a sampling environment regardless of the sampler type. The sampling environment was the single largest predictor of microbial community composition within a study, while sampler type was found to have much less predictive power. Quantitative analyses in indoor spaces indicated highest yields using a petri dish approach, followed by sampling with EDCs and TefTex. The highest correlations between duplicate samples were observed for EDC and petri dish approaches, indicating greater experimental repeatability for these sampler types. For the EDC samples, it became apparent that, due to the fibrous nature of the material, a rigorous extraction protocol is crucial to obtain optimal yields and stable, repeatable results.

CONCLUSIONS

Correlations between sampler types were strong both in compositional and quantitative terms, and thus, the particular choice of passive settled dust sampler is not likely to strongly alter the overall conclusion of a study that aims to characterize dust across different environments. Microbial cell abundances determined from settled dust varied with the use of different sampling approaches, and thus, consistency in the method is necessary to allow for absolute comparisons within and among studies. Considering practical aspects, petri dishes were found to be an inexpensive, simple, and feasible approach that showed the highest quantitative determinations under typical building conditions, though the choice of sampler will ultimately depend on study logistics and characteristics such as low- or high-exposure settings.

Estimation of the in vitro eye irritating and inflammatory potential of lipopolysaccharide (LPS) and dust by using reconstituted human corneal epithelium tissue cultures

CONTEXT

Eye irritation is a common complaint in indoor environment, but the causes have still not been identified among the multiple exposures in house environments. To identify the potential environmental factors responsible for eye irritation and study the possible mechanisms, an in vitro model for eye irritation is suggested.

MATERIALS AND METHODS

In this study, reconstituted human corneal epithelium (HCE) tissue cultures were used to study the eye irritating and inflammatory potential of lipopolysaccharide (LPS) and dust. HCE tissue cultures were exposed to a range of concentrations of LPS for 6 h and dust for 24 h, respectively. After exposure, viability and secretion of interleukins (IL) IL-1β, IL-8, and tumor necrosis factor (TNFα) were examined. Histology was used to indicate the morphological changes after dust exposure.

RESULTS

Both LPS and dust affected HCE viability. There was an increased level of IL-8 after LPS exposure, while the concentrations of IL-1β and TNFα remained unaffected. Dust exposure resulted in an elevation of both IL-1β and IL-8, but not TNFα. Histology study showed increased vacuolization and reduced thickness after 24 h exposure to 5 mg/mL dust.

DISCUSSION AND CONCLUSION

LPS and dust showed in vitro eye irritating and inflammatory potential, and cytokines/chemokines like IL-1β and IL-8 may be involved in the mechanisms of eye irritation. The HCE tissue culture may be used as an in vitro model to study environmental exposure induced eye irritation and inflammation.

Indoor and outdoor exposure to ultrafine, fine and microbiologically derived particulate matter related to cardiovascular and respiratory effects in a panel of elderly urban citizens

To explore associations of exposure to ambient and indoor air particulate and bio-aerosol pollutants with cardiovascular and respiratory disease markers, we utilized seven repeated measurements from 48 elderly subjects participating in a 4-week home air filtration study. Microvascular function (MVF), lung function, blood leukocyte counts, monocyte adhesion molecule expression, C-reactive protein, Clara cell protein (CC16) and surfactant protein-D (SPD) were examined in relation to exposure preceding each measurement. Exposure assessment included 48-h urban background monitoring of PM10, PM2.5 and particle number concentration (PNC), weekly measurements of PM2.5 in living- and bedroom, 24-h measurements of indoor PNC three times, and bio-aerosol components in settled dust on a 2-week basis. Statistically significant inverse associations included: MVF with outdoor PNC; granulocyte counts with PM2.5; CD31 expression with dust fungi; SPD with dust endotoxin. Significant positive associations included: MVF with dust bacteria; monocyte expression of CD11 with PM2.5 in the bedroom and dust bacteria and endotoxin, CD31 expression with dust serine protease; serum CC16 with dust NAGase. Multiple comparisons demand cautious interpretation of results, which suggest that outdoor PNC have adverse effects on MVF, and outdoor and indoor PM2.5 and bio-aerosols are associated with markers of inflammation and lung cell integrity.

Microbiological characterization of 3193 French dwellings of Elfe cohort children

Although exposure to indoor microorganisms in early life has already been associated with respiratory illness or allergy protection, only a few studies have performed standardized samplings and specific microbial analysis. Moreover, most do not target the different groups of microorganisms involved in respiratory diseases (fungi, bacteria, dust mites). In our study, ten specific qPCR targets (6 fungal species, 1 family and 2 genera of bacteria, 1 house dust mite) were used to analyze the microorganism composition of electrostatic dust fall collector (EDC) from 3193 dwellings of the Elfe French cohort study. Multivariate analyses allowed us to show that the microbial composition of dwellings, assessed with simultaneous analysis of 10 microorganisms, can be characterized by four entities: three bacteria, house dust mite Dermatophagoïdes pteronyssinus, fungi Alternaria alternata, and five other molds. Some dwellings' intrinsic characteristics (occupational ratio, type of dwelling and presence of pets) clearly influence microorganism distribution, and six different profiles of dwellings, characterized by their composition in microorganisms, have been described across France. The use of these clusters seems promising in the evaluation of allergic risk. Allergic respiratory diseases will develop in the near future in some children of the Elfe cohort and will indicate to what extent our approach can be predictive of respiratory disease.

Effect of deployment time on endotoxin and allergen exposure assessment using electrostatic dust collectors

The electrostatic dust collector (EDC) is a passive dust sampling device for exposure assessment of airborne endotoxin and possibly allergens. EDCs consist of a non-conducting plastic folder holding two or four electrostatic cloths of defined area. The sampling time needed to achieve detectable and reproducible loading for bioaerosols has not been systematically evaluated. Thus, in 15 Iowa farm homes EDCs were deployed for 7-, 14-, and 28-day sampling periods to determine if endotoxin and allergens could be quantified and if loading rates were uniform over time, i.e. if loads doubled from 7 to 14 days or 14 to 28 days and quadrupled from 7 to 28 days. Loadings between left and right paired EDC cloths were not significantly different and were highly correlated for endotoxin, total protein, and cat (Fel d1), dog (Can f1), and mouse (Mus m1) allergens (P < 0.001). EDCs performed especially well for endotoxin sampling with close agreement between paired samples (Pearson r = 0.96, P < 0.001). Endotoxin loading of the EDCs doubled from 7- to 14-day deployments as hypothesized although the loading rate decreased from 14 to 28 days of sampling with only a 1.38-fold increase. Allergen exposure assessment using EDCs was overall less satisfactory. Although there was reasonable agreement between paired samples, only exposures to cat, dog, and mouse allergens were reliable and these only at the longer deployment times.

Cardiovascular and lung function in relation to outdoor and indoor exposure to fine and ultrafine particulate matter in middle-aged subjects

This cross-sectional study investigated the relationship between exposure to airborne indoor and outdoor particulate matter (PM) and cardiovascular and respiratory health in a population-based sample of 58 residences in Copenhagen, Denmark. Over a 2-day period indoor particle number concentrations (PNC, 10-300 nm) and PM2.5 (aerodynamic diameter<2.5 μm) were monitored for each of the residences in the living room, and outdoor PNC (10-280 nm), PM2.5 and PM10 (aerodynamic diameter<10 μm) were monitored at an urban background station in Copenhagen. In the morning, after the 2-day monitoring period, we measured microvascular function (MVF) and lung function and collected blood samples for biomarkers related to inflammation, in 78 middle-aged residents. Bacteria, endotoxin and fungi were analyzed in material from electrostatic dust fall collectors placed in the residences for 4 weeks. Data were analyzed using linear regression with the generalized estimating equation approach. Statistically significant associations were found between indoor PNC, dominated by indoor use of candles, and lower lung function, the prediabetic marker HbA1c and systemic inflammatory markers observed as changes in leukocyte differential count and expression of adhesion markers on monocytes, whereas C-reactive protein was significantly associated with indoor PM2.5. The presence of indoor endotoxin was associated with lower lung function and expression of adhesion markers on monocytes. An inverse association between outdoor PNC and MVF was also statistically significant. The study suggests that PNC in the outdoor environment may be associated with decreased MVF, while PNC, mainly driven by candle burning, and bioaerosols in the indoor environment may have a negative effect on lung function and markers of systemic inflammation and diabetes.

Monitoring of occupational and environmental aeroallergens-- EAACI Position Paper. Concerted action of the EAACI IG Occupational Allergy and Aerobiology & Air Pollution

Exposure to high molecular weight sensitizers of biological origin is an important risk factor for the development of asthma and rhinitis. Most of the causal allergens have been defined based on their reactivity with IgE antibodies, and in many cases, the molecular structure and function of the allergens have been established. Significant information on allergen levels that cause sensitization and allergic symptoms for several major environmental and occupational allergens has been reported. Monitoring of high molecular weight allergens and allergen carrier particles is an important part of the management of allergic respiratory diseases and requires standardized allergen assessment methods for occupational and environmental (indoor and outdoor) allergen exposure. The aim of this EAACI task force was to review the essential points for monitoring environmental and occupational allergen exposure including sampling strategies and methods, processing of dust samples, allergen analysis, and quantification. The paper includes a summary of different methods for sampling and allergen quantification, as well as their pros and cons for various exposure settings. Recommendations are being made for different exposure scenarios.

Endotoxin levels in settled airborne dust in European schools: the HITEA school study

Indoor exposure to microbial agents is known to influence respiratory health. Besides home exposure, exposure in schools can affect respiratory health. In this study, we measured endotoxin in settled dust in primary schools in three European countries from three different geographical regions with different climates. Our aim was to characterize endotoxin levels in primary schools and evaluate associations with potential determinants. Endotoxin levels were repeatedly assessed in 23 schools in Spain (n = 7), the Netherlands (n = 10), and Finland (n = 6) using electrostatic dustfall collectors. In total, 645 measurements were taken in 237 classrooms. Endotoxin levels differed significantly between countries; Dutch schools had the highest levels, while Finnish schools showed the lowest levels. In each country, differences in endotoxin levels were observed between schools and over the sampling periods. Estimates improved after adjustment for sampling period. Factors affecting endotoxin levels in a school differed per country. In general, endotoxin levels were higher in lower grades and in classrooms with higher occupancy. School endotoxin levels may contribute significantly to total endotoxin exposure in children and teachers. As the correlation between the repeated measurements is reasonable, single endotoxin measurements form a reasonable basis for estimating annual endotoxin levels in schools.