The effect of temperature on airborne filamentous fungi in the indoor and outdoor space of a hospital

Mycological Methods for Routine Air Sampling and Interpretation of Results in Operating Theaters

Many infectious diseases are transmitted via the air and are, therefore, particularly difficult to combat. These infections include various invasive mycoses caused by molds. The usual route of infection is the inhalation of conidia. In hospitals, infection can also occur through the deposition of conidia in otherwise sterile anatomical sites during surgical and other invasive procedures. Therefore, knowledge of airborne mold concentrations can lead to measures to protect patients from fungal infections. The literature on this topic contains insufficient and sometimes ambiguous information. This is evidenced by the fact that there are no international recommendations or guidelines defining the methodology of air sampling and the interpretation of the results obtained. Surgical departments, intensive care units and medical mycology laboratories are, therefore, left to their own devices, leading to significant differences in the implementation of mycological surveillance in hospitals. The aim of this mini-review is to provide an overview of the current methods of air sampling and interpretation of results used in medical mycology laboratories.

Environmental surveillance of fungi and susceptibility to antifungal agents in tertiary care hospitals

IMPORTANCE

Saprophytic fungi can cause nosocomial infections in high-risk patients. These infections are related to high mortality and cost. In the current study, different species of filamentous fungi and yeast were isolated from the environment of the studied hospitals. Some species were resistant to antifungal drugs. We suggest that the future work concentrates on the relationship between the level/quantification of saprophytic contamination in the environment of hospitals and fungal infections in patients.

Prevalence of airborne fungi in Brazil and correlations with respiratory diseases and fungal infections

Airborne fungi are dispersed through the air. The aim of this study was to determine the prevalence of airborne fungi in Brazil and understand the relationship between fungal growth and respiratory diseases and infections. We conducted an integrative literature review of studies conducted in Brazil based on searches of the PubMed, MEDLINE-BIREME, SciELO, and LILACS databases for full-text articles published between 2000 and 2022. The searches returned 147 studies, of which only 25 met the inclusion criteria. The most prevalent genera of airborne fungi in Brazil are Aspergillus, Penicillium, Cladosporium, Curvularia, and Fusarium. The studies were conducted in the states of Maranhão, Ceará, Piauí, Sergipe, Mato Grosso, Pernambuco, Rio Grande do Sul, Santa Catarina, Rio de Janeiro, São Paulo, and Minas Gerais. The findings also show the relationship between fungi and meteorological factors and seasonality, the sensitivity of atopic individuals to fungi, and the main nosocomial mycoses reported in the literature. This work demonstrates the importance of maintaining good microbiological air quality to prevent potential airborne diseases.

Stochastic Processes Derive Gut Fungi Community Assembly of Plateau Pikas (Ochotona curzoniae) along Altitudinal Gradients across Warm and Cold Seasons

Although fungi occupy only a small proportion of the microbial community in the intestinal tract of mammals, they play important roles in host fat accumulation, nutrition metabolism, metabolic health, and immune development. Here, we investigated the dynamics and assembly of gut fungal communities in plateau pikas inhabiting six altitudinal gradients across warm and cold seasons. We found that the relative abundances of Podospora and Sporormiella significantly decreased with altitudinal gradients in the warm season, whereas the relative abundance of Sarocladium significantly increased. Alpha diversity significantly decreased with increasing altitudinal gradient in the warm and cold seasons. Distance-decay analysis showed that fungal community similarities were significantly and negatively correlated with elevation. The co-occurrence network complexity significantly decreased along the altitudinal gradients as the total number of nodes, number of edges, and degree of nodes significantly decreased. Both the null and neutral model analyses showed that stochastic or neutral processes dominated the gut fungal community assembly in both seasons and that ecological drift was the main ecological process explaining the variation in the gut fungal community across different plateau pikas. Homogeneous selection played a weak role in structuring gut fungal community assembly during the warm season. Collectively, these results expand our understanding of the distribution patterns of gut fungal communities and elucidate the mechanisms that maintain fungal diversity in the gut ecosystems of small mammals.

Monitoring of airborne fungi during the second wave of COVID-19 in selected wards of the referral university hospital in southeastern Iran

Microbiological monitoring of the air hospital is essential for prevention and control, due to the possible airborne route of infection transmission, especially in high-risk wards. This study aimed to monitor the airborne fungi during the second wave of the COVID-19 pandemic in selected wards of the biggest university educational hospital in Kerman, southeastern Iran. This study was conducted in 11 different wards, separated into the patient room and nursing station, of the Afzalipour hospital from May to August 2021. Fungal isolates were characterized to the species level by conventional and sequencing methods. Out of 93 obtained fungal colonies, 70 (75.3%) isolates were filamentous and 23 (24.7%) isolates were yeast. Aspergillus species were the predominant fungal isolates among the filamentous colonies (n=19; 27.1%), and Naganishia albida (formerly Cryptococcus albidus) was identified as the most common yeast isolate (n=13/23; 56.8%). The infectious ward was the most contaminated unit (n=19/93), while the least contaminated units were the neonatal intensive care unit (n=3/93), and oncology (n=3/93). The statistical findings displayed that the number of fungal isolates in patients' rooms is significantly higher than in nurses' stations (p-value=0.013). Our study demonstrated the presence of diverse fungal species in all wards of the hospital. Considering the presence of airborne fungi in hospitals and related public health problems is one of the critical issues for health systems management. In this regard, efficient monitoring of airborne fungi might play an influential role in hospital infection control and surveillance, particularly in high-risk hospitalization patients in critical wards.

Opportunistic Mycobiota of Dust in Cities of Different Climate Zones: Murmansk and Moscow

For the first time, mycological analysis of dust, including assessment of opportunistic fungal species, was carried out for the urban ecosystems of air, vegetation, and paved surfaces in different climate areas (the cities of Murmansk and Moscow). The combined effect of environmental factors (climate, functional zone, and substrate type) on qualitative and quantitative parameters of micromycete communities was assessed using MANOVA and cluster analysis. It was found that the abundance of culturable mycobiota in the air, on tree leaves, and on paved surfaces was lower in Murmansk than in Moscow. In both cities, approximately a half of fungal species were opportunistic pathogens. The relative abundance of opportunistic fungi of the BSL-2 group was higher in the air of the traffic zone in both cities and of the residential zone in Moscow. In the residential and traffic zones of Moscow, the most abundant species in the air in on the road dust were Aspergillus fumigatus and A. niger, while in Murmansk communities were dominated by members of the genera Cephalosporium, Scopulariopsis, and Trichoderma, which are less pathogenic for humans. The most significant factors affecting the abundance and species diversity of micromycetes, including opportunistic fungi, were the substrate type (air, leaves, or paved surfaces) and the climate, while the effect of the functional zone was not significant. The recreation zones of cities located in different climate regions are the most favorable for humans due to lower abundance of opportunistic fungi in the air and to lack of micromycetes of the BSL-2 and BSL-3 groups. However, the abundance of potentially pathogenic species on the surfaces of leaves and roads in this zone was higher than in the air. Therefore, it can be recommended that city residents minimize their contact with the leaves surface and road pavements, which is especially relevant for toddlers, so as to diminish the probability of encountering opportunistic mycobiota that potentially represents a health hazard.

Indoor Air Quality in Healthcare Units—A Systematic Literature Review Focusing Recent Research

The adequate assessment and management of indoor air quality in healthcare facilities is of utmost importance for patient safety and occupational health purposes. This study aims to identify the recent trends of research on the topic through a systematic literature review following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. A total of 171 articles published in the period 2015–2020 were selected and analyzed. Results show that there is a worldwide growing research interest in this subject, dispersed in a wide variety of scientific journals. A textometric analysis using the IRaMuTeQ software revealed four clusters of topics in the sampled articles: physicochemical pollutants, design and management of infrastructures, environmental control measures, and microbiological contamination. The studies focus mainly on hospital facilities, but there is also research interest in primary care centers and dental clinics. The majority of the analyzed articles (85%) report experimental data, with the most frequently measured parameters being related to environmental quality (temperature and relative humidity), microbiological load, CO2 and particulate matter. Non-compliance with the WHO guidelines for indoor air quality is frequently reported. This study provides an overview of the recent literature on this topic, identifying promising lines of research to improve indoor air quality in healthcare facilities.

A systematic review and meta-analysis of indoor bioaerosols in hospitals: The influence of heating, ventilation, and air conditioning

OBJECTIVES

To evaluate (1) the relationship between heating, ventilation, and air conditioning (HVAC) systems and bioaerosol concentrations in hospital rooms, and (2) the effectiveness of laminar air flow (LAF) and high efficiency particulate air (HEPA) according to the indoor bioaerosol concentrations.

METHODS

Databases of Embase, PubMed, Cochrane Library, MEDLINE, and Web of Science were searched from 1st January 2000 to 31st December 2020. Two reviewers independently extracted data and assessed the quality of the studies. The samples obtained from different areas of hospitals were grouped and described statistically. Furthermore, the meta-analysis of LAF and HEPA were performed using random-effects models. The methodological quality of the studies included in the meta-analysis was assessed using the checklist recommended by the Agency for Healthcare Research and Quality.

RESULTS

The mean CFU/m3 of the conventional HVAC rooms and enhanced HVAC rooms was lower than that of rooms without HVAC systems. Furthermore, the use of the HEPA filter reduced bacteria by 113.13 (95% CI: -197.89, -28.38) CFU/m3 and fungi by 6.53 (95% CI: -10.50, -2.55) CFU/m3. Meanwhile, the indoor bacterial concentration of LAF systems decreased by 40.05 (95% CI: -55.52, -24.58) CFU/m3 compared to that of conventional HVAC systems.

CONCLUSIONS

The HVAC systems in hospitals can effectively remove bioaerosols. Further, the use of HEPA filters is an effective option for areas that are under-ventilated and require additional protection. However, other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi.

LIMITATION OF STUDY

Although our study analysed the overall trend of indoor bioaerosols, the conclusions cannot be extrapolated to rare, hard-to-culture, and highly pathogenic species, as well as species complexes. These species require specific culture conditions or different sampling requirements. Investigating the effects of HVAC systems on these species via conventional culture counting methods is challenging and further analysis that includes combining molecular identification methods is necessary.

STRENGTH OF THE STUDY

Our study was the first meta-analysis to evaluate the effect of HVAC systems on indoor bioaerosols through microbial incubation count. Our study demonstrated that HVAC systems could effectively reduce overall bioaerosol concentrations to maintain better indoor air quality. Moreover, our study provided further evidence that other components of the LAF system other than the HEPA filter are not conducive to removing airborne bacteria and fungi.

PRACTICAL IMPLICATION

Our research showed that HEPA filters are more effective at removing bioaerosols in HVAC systems than the current LAF system. Therefore, instead of opting for the more costly LAF system, a filter with a higher filtration rate would be a better choice for indoor environments that require higher air quality; this is valuable for operating room construction and maintenance budget allocation.

Risk assessment and disease burden of legionella presence in cooling towers of Iran's central hospitals

Regular monitoring and measurement of Legionella in tower water and preventive measures against contamination are particularly important in hospitals. This study aimed at risk assessment and disease burden because of legionella presence in cooling towers of Iran's central hospitals. Then its correlation with temperature, pH, turbidity, residual chlorine, and EC was investigated by the Pearson test. The health risk and burden of diseases caused by Legionella exposure were determined using QMRA and DALY models. Statistical analysis and modeling were performed in MATLAB₂₀₁₈. Of the total samples, 30-43% was infected with Legionella. The mean concentrations in hospital A and B were 5-102.5 ± 10 and 5-89.7 ± 0.7 CFU/L, respectively. Among environmental factors, turbidity and pH were the most effective factors in increasing and decreasing Legionella concentration, respectively. According to the QMRA model, the risks of Legionella infections and annual mortality in both hospitals were 0.2-0.3, 0-0.19, 2-2.9 × 10^-5, and 0-0.7 × 10^-5, respectively, which was higher than the acceptable risk range for Legionella (10-4-10-7). However, the trend of its change was negatively correlated with time (R_B = - 0.77). According to the results, the concentration of Legionella and the exposure risk in both hospitals were higher than the permissible range, which is necessary to decrease to 0.1 current concentrations.

Fungal populations in the bedroom dust of children in Havana, Cuba, and its relationship with environmental conditions

The study of the fungal community composition in house dust is useful to assess the accumulative exposure to fungi in indoor environments. The objective of this research was to characterize the fungal diversity of house dust and its association with the environmental conditions of bedrooms. For this, the dust was collected from 41 bedrooms of children between the ages of 8 and 9 with a family history of asthma, residents of Havana, Cuba. The fungal content of each sample was determined by two methods: plate culture with malt extract agar and by direct microscopy. An ecological analysis was carried out from the fungal diversity detected. To describe the factors associated with the fungi detected, bivariate logistic regression was used. Through direct microscopy, between 10 and 2311 fragments of hyphae and spores corresponding mainly to Cladosporium, Coprinus, Curvularia, Aspergillus/Penicillium, Xylariaceae, and Periconia were identified. Through the culture, 0-208 CFU were quantified, where Aspergillus, Cladosporium, and Penicillium predominated. The culturability evidenced the differences between the quantification determined by both methods. A positive relationship was found between the type of cleaning of the furniture, the presence of trees in front of the bedroom, indoor relative humidity, indoor temperature, the presence of air conditioning, and natural ventilation with specific spore types and genera. The use of two different identification methods allowed to detect a greater fungal diversity in the residences evaluated. Monitoring the exposure to these fungal allergens in childhood can help to prevent sensitization in the allergic child, the development of asthma, and other respiratory diseases.

Simultaneous monitoring of SARS-CoV-2, bacteria, and fungi in indoor air of hospital: a study on Hajar Hospital in Shahrekord, Iran

The novel SARS-CoV-2 outbreak was declared as pandemic by the World Health Organization (WHO) on March 11, 2020. Understanding the airborne route of SARS-CoV-2 transmission is essential for infection prevention and control. In this study, a total of 107 indoor air samples (45 SARS-CoV-2, 62 bacteria, and fungi) were collected from different wards of the Hajar Hospital in Shahrekord, Iran. Simultaneously, bacterial and fungal samples were also collected from the ambient air of hospital yard. Overall, 6 positive air samples were detected in the infectious 1 and infectious 2 wards, intensive care unit (ICU), computed tomography (CT) scan, respiratory patients' clinic, and personal protective equipment (PPE) room. Also, airborne bacteria and fungi were simultaneously detected in the various wards of the hospital with concentrations ranging from 14 to 106 CFU m-3 and 18 to 141 CFU m-3, respectively. The highest mean concentrations of bacteria and fungi were observed in respiratory patients' clinics and ICU wards, respectively. Significant correlation (p < 0.05) was found between airborne bacterial concentration and the presence of SARS-CoV-2, while no significant correlation was found between fungi concentration and the virus presence. This study provided an additional evidence about the presence of SARS-CoV-2 in the indoor air of a hospital that admitted COVID-19 patients. Moreover, it was revealed that the monitoring of microbial quality of indoor air in such hospitals is very important, especially during the COVID-19 pandemic, for controlling the nosocomial infections.

Airborne fungi in Universiti Sains Malaysia: knowledge, density and diversity

Airborne fungi are among common contaminants in indoor and outdoor environments, leading to poor indoor air quality (IAQ), and to some extent, implicate health risks to humans worldwide. In Malaysia, fungal contamination in institutional buildings is rarely documented although these places are frequently visited by many. This study was conducted to assess the density and diversity of airborne fungi in Universiti Sains Malaysia (USM) main campus, Penang. A total of 11 sampling sites were assessed. Fungi were collected by using Andersen Single Stage Impact Air Sampler N-6 and MEA plates. Two separate trials, namely Trial 1 and Trial 2, were conducted in 2008 and 2019, respectively. The recovered fungi were identified up to the genus level-based morphological features. A survey involving 400 respondents among USM staff and students in relation to fungal contamination in indoor air environment was also conducted to evaluate the knowledge on indoor fungi among USM community. The densities of indoor air fungi in Trial 1 were higher; ranging from 81 to 1743 CFU/m³, exceeding the recommended level set by the Malaysia Industry Code of Practice (MCPIAQ) in some sampling sites, compared to that of in Trial 2 where the densities ranged from 229 to 699 CFU/m³. A total of 154 isolates and 230 isolates of airborne fungi were recovered in Trial 1 and Trial 2, respectively. In total, 11 fungal genera were identified in both trials, and three genera were predominant: Aspergillus, Penicillium, and Cladosporium. The survey also revealed that knowledge of IAQ among staff and students was limited and that they were unaware of fungal contamination and IAQ. A continuous and wide-spread awareness should be implemented at USM main campus for safer and healthier indoor air environments, particularly university students where productivity and efficiency are of the utmost importance.

Combining culturing and 16S rDNA sequencing to reveal seasonal and room variations of household airborne bacteria and correlative environmental factors in nanjing, southeast china

Exposure to bioaerosols poses important health effects on occupants. To elucidate seasonal and room variations of household airborne bacteria, this study investigated 30 residential homes during summer and winter throughout Nanjing, Southeast China, with a humid subtropical climate. Culturing and 16S rDNA sequencing methods were combined in this study. Results showed that the community structure and composition in the same season but different homes show similarity, however, they in the same home but in different seasons show a huge difference, with Sphingomonas (25.3%), Clostridium (14.8%), and Pseudomonas (7.6%) being the dominant bacteria in summer, and Pseudomonas (57.1%) was dominant bacteria in winter. Culturable concentrations of bacteria were also significantly higher in summer (854 ± 425 CFU/m³ ) than in winter (231 ± 175 CFU/m³ ), but difference by home or room was relatively minor. More than 80% of culturable bacteria (<4.7 μm) could penetrate into lower respiratory tract. The seasonal variations of bacterial community and concentrations were closely associated with seasonal variations of temperature, humidity, and PM_2.5 . Higher concentrations and larger sizes were observed in the bathroom and kitchen, typically with higher humidity than other rooms.

Air change rate effects on the airborne diseases spreading in Underground Metro wagons

The effect of the rate of change of fresh air inside passengers' wagons for Underground Metro on the spreading of airborne diseases like COVID-19 is investigated numerically. The study investigates two extreme scenarios for the location of the source of infection within the wagon with four different air change rates for each. The first scenario considers the source of infection at the closest point to the ventilation system while the other places the infection source at the farthest point from the wagon ventilation system. The effect of the wagon windows' status (i.e. closed or open) is also studied. It is found that under all conditions, open windows are always favored to decrease the infection spreading potential. A higher air change rate also decreases the infection spreading up to a certain value, beyond which the effect is not noticeable. The location of the infection source was found to greatly affect the infection spreading as well. The paper gives recommendations on the minimum air change rate to keep the infection spreading potentials to a minimum considering different times the passengers stay in the wagon.

Fungi in the indoor air of critical hospital areas: a review

Invasive fungal infection is an important cause of mortality and morbidity in neonates, especially in low-birthweight neonates. The contribution of fungi in the indoor air to the incidence of mucocutaneous colonization and to the risk of invasive fungal infection in this population is uncertain. This review aimed to identify and to summarize the best available evidence on the fungal contamination in the indoor air of critical hospital areas with an emphasis on pediatric/neonatal ICUs. Publications from 2005 to 2019 were searched in the databases Scientific Electronic Library Online (SciELO), US National Library of Medicine National Institutes of Health Search (PubMed), and Latin American Caribbean Health Sciences (LILACS). Descriptors in Health Sciences (DeCS) were used. Research papers published in Portuguese, English, and Spanish were included. Twenty-nine papers on all continents except Australia were selected. The results showed that the air mycobiota contained several fungal species, notably Aspergillus, Penicillium, Cladosporium, Fusarium, and yeast (Candida) species. The selected papers point out the risks that fungi pose to neonates, who have immature immune system, and describe simultaneous external factors (air humidity, seasonality, air and people flow, use of particulate filters, and health professionals' hand hygiene) that contribute to indoor air contamination with fungi. Improving communication among health professionals is a great concern because this can prevent major health complications in neonates, especially in low-birthweight neonates. The results reinforced the need to monitor environmental fungi more frequently and efficiently in hospitals, especially in neonatal ICUs.

Effect of land use on cultivable bioaerosols in the indoor air of hospital in southeast Iran and its determination of the affected radius around of hospital

This study aimed to evaluate the effect of land use on hospital bioaerosols and determine the effective radius. The concentration of fungi and bacteria in indoor and outdoor air was determined by the 0800NIOSH. Then land uses were determined by Google earth within a range of 0.5-5 km around three hospitals. Data were analyzed by using Spearman correlation, and a t test was used to determine differences between groups. Data were recorded in Excel and entered into Matlab₂₀₁₈ for analysis. The results of the study showed that the concentration of fungi and bacteria was higher in the indoor and outdoor hospital B (bacteria = 343-43, fungi = 106-291 CFU/m³) (P = 0.04). Maximum land use was also found in hospitals A and B related to urban and bare, while in hospital C, they were urban and bare. Mathematical modeling has shown that the trend of land-use variation over different radii consisted of the Gaussian model (in hospital B) and Fourier series (in hospitals A and C). Besides, there was a positive correlation between the bare and fungal and bacterial concentrations. Finally, the most effective bare radius of application on the indoor and outdoor fungi was 4 and 5 km, respectively (R² = 0.99). The effective radius for reducing fungi and bacteria by creating green space was 0.5 and 3 km from the hospital center (R²_fungi = - 0.99, R²_bacteria = - 0.8). Based on these results, land use is an effective factor in airborne fungi and bacteria in hospitals. Therefore, their control and management of land use during 5 km is necessary to reduce pollution.

Temporal variation of airborne fungi in university library rooms and its relation to environmental parameters and potential confounders

Indoor airborne fungi have been associated with adverse human health effects. Therefore, it is important to understand the causes of underlying variation in airborne fungi in indoor environments. This study consequently aimed to investigate the association between indoor fungi with temporal variation, environmental parameters, and potential confounders over 10 months in four library rooms using Andersen samplers. Indoor fungal concentrations peaked in October and were lowest in March in both stack rooms, whereas the highest concentrations in both reading rooms were observed in September with lowest concentrations in July. Nonparametric analyses revealed higher fungal concentrations in the rooms that were significantly associated with relative humidity ≥ 60%, PM_2.5 ≥ 35 μg/m³, number of people ≥ 16, open windows, working air conditioners, and room area < 400 m². Multiple linear regression modeling for the library building considering only continuous variables revealed that relative humidity, PM_2.5, and the number of people were significant predictors of fungal concentrations. Additionally, the model with continuous and categorical variables suggested that relative humidity, PM_2.5, the number of people, ceiling fan condition, window state, and air conditioner operating status were significant predictor variables of concentrations. Outdoor fungal concentrations were a significant predictor for the two models of indoor fungal concentrations for each room. Ceiling fan or air conditioner operation was associated with altered fungal particle concentrations. These results provide a deeper understanding of indoor air fungal quality.

Impact of negative pressure system on microbiological air quality in a Central Sterile Supply Department

OBJECTIVE

Guidelines recommend that the cleaning area in a Central Sterile Supply Department (CSSD) maintain a negative pressure of the environmental air, but how much this system can impact the contamination of the air by bioaerosols in the area is not known. The objective of this study was to assess the impact of negative pressure on CSSD by evaluating the microbiological air quality of this sector.

METHODS

Microbiological air samples were collected in two CSSD in the same hospital: one with and one without a negative air pressure system. Outdoor air samples were collected as a comparative control. Andersen six-stage air sampler was used to obtain the microbiological air samples.

RESULTS

The concentration of bioaerosols in the CSSD without negative pressure was 273.15 and 206.71 CFU/m3 , while in the CSSD with negative pressure the concentration of bioaerosols was 116.96 CFU/m3 and 131.10 CFU/m3 . The number of isolated colonies in the negative pressure CSSD was significantly lower (P = .01541).

CONCLUSION

The findings showed that the negative pressure system in the CSSD cleaning area contributed to the quantitative reduction in bioaerosols. However, the concentration of bioaerosols was lower than that established in the guideline for indoor air quality of many countries. Therefore, it cannot be concluded that CSSDs which do not have a negative pressure system in their cleaning area offer occupational risk.

The impact of agricultural and green waste treatments on compost quality of dewatered sludge

Composting is one of the environmentally desirable methods for the management of sewage sludge. In this process, the organic matters were decomposed by microorganisms. However, different treatments can improve their qualities. This study aimed to investigate the effect of two agricultural waste wheat straw (WS) and green waste eucalyptus tree leaves (ETL) treatments on the quality of the compost produced from dewatered sewage sludge. So that, the variation trend of heavy metals, temperature, moisture, PH, and C/N ratio was considered during the composting process. The results showed that the variation of some parameters in WS and ETL such as temperature (24.68 ± 0.26 and 23.41 ± 1.35), moisture (4.5 ± 2.64 and 7.66 ± 2.51), pH (5.66 ± 0.35 and 5.97 ± 0.41), and C/N ratio (250 ± 4.08 and 60 ± 3.21) was suitable in both windrows, respectively. Likewise, trend of mineralization was suitable in both masses, because TVS (43 to 78 mg/g DW for WS and 45 to 69 mg/g DW for ETL) and TDS (21 to 55 mg/g DW for WS and 2.6 to 38 mg/g DW for ETL) decreased and increased, respectively, in the composting process. While fecal coliform (2.72 MPN/g DW) and EC (2.4mmho/cm) at WS was more than Iran's agricultural standard. As a consequence, although the quality of both masses was suitable and similar, there are some limitations for using treated compost by WS in agricultural lands due to higher levels of EC, fecal coliforms, and manganese. Therefore, quality of dewatered sludge treated compared with ETL is higher than WS. Furthermore, improvement process and application of some pretreatments are necessary for decreasing the heavy metals.

On the interpretation of bioaerosol exposure measurements and impacts on health

Bioaerosols are recognized as one of the main transmission routes for infectious diseases and are responsible for other various types of health effects through inhalation and potential ingestion. Associating exposure with bioaerosol and health problems is challenging, and adequate exposure monitoring is a top priority for aerosol scientists. The multiple factors affecting bioaerosol content, the variability in the focus of each bioaerosol exposure study, and the variations in experimental design and the standardization of methods make bioaerosol exposure studies very difficult. Therefore, the health impacts of bioaerosol exposure are still poorly understood. This paper presents a brief description of a state-of-the-art development in bioaerosol exposure studies supported by studies on several related subjects. The main objective of this paper is to propose new considerations for bioaerosol exposure guidelines and the development of tools and study designs to better interpret bioaerosol data. The principal observations and findings are the discrepancy of the applicable methods in bioaerosol studies that makes result comparison impossible. Furthermore, the silo mentality helps in creating a bigger gap in the knowledge accumulated about bioaerosol exposure. Innovative and original ideas are presented for aerosol scientists and health scientists to consider and discuss. Although many examples cited herein are from occupational exposure, the discussion has relevance to any human environment. This work gives concrete suggestions for how to design a full bioaerosol study that includes all of the key elements necessary to help understand the real impacts of bioaerosol exposure in the short term. The creation of the proposed bioaerosol public database could give crucial information to control the public health. Implications: How can we move toward a bioaerosol exposure guidelines? The creation of the bioaerosol public database will help accumulate information for long-term association studies and help determine specific exposure biomarkers to bioaerosols. The implementation of such work will lead to a deeper understanding and more efficient utilization of bioaerosol studies to prevent public health hazards.