Mycotoxins as harmful indoor air contaminants

Fungal metabolites (mycotoxins) that pose a health hazard to humans and animals have long been known to be associated with mold-contaminated food and feed. In recent times, concerns have been raised about exposures to mycotoxin-producing fungi in indoor environments, e.g., damp homes and buildings. The principal mycotoxins that contaminate food and feed (alfatoxins, fumonisins, ochratoxin A, deoxynivalenol, zearalenone) are rarely if ever found in indoor environments, but their toxicological properties provide an insight into the difficulties of assessing the health effects of related mycotoxins produced by indoor molds. Although the Penicillium and Aspergillus genera of fungi are major contaminants of both food and feed products and damp buildings, the particular species and hence the array of mycotoxins are quite different in these environments. The mycotoxins of these indoor species and less common mycotoxins from Stachybotrys and Chaetomium fungi are discussed in terms of their health effects and the need for relevant biomarkers and long-term chronic exposure studies.     

Airborne fungi as biocontaminants at two Milan underground stations

The viable or culturable air spora of two Milan underground stations and of the squares above has been investigated during a one-year study. Aerobiological data were collected by semi-quantitative method. Outdoor results show the presence of four dominant genera, Cladosporium, Penicillium, Epicoccum and Alternaria, whose presence varied throughout the year. Cryptococcus neoformans was isolated in Duomo Square. Indoor sampling shows to what extent the mycoflora of an indoor environment can depend both on the fungal spora coming from outside and the capacity of the fungi to colonize the different sublayers found indoors.     

An indoor air model

Indoor aerobiological data sets are often difficult to handle because they are not easily related to climatic parameters similar to those found outdoors. However, in large buildings, where ventilation systems allow a systematic knowledge of air flows, the transfer of a power distribution model to airborne spore concentration can simplify the task of reaching a decision on contamination presence. The use of the absorption percentage of each component of the ventilation system (air intake, filters, cooling, humidification, air return) can identify abnormalities (i.e. concentrations not following the general expected model, which could mean contamination requiring action), permit direct cleaning, and allow the restoration of a normal state after a short period of time.     

Fungal pollution of indoor environments and its management

Indoor environments play important roles in human health. The health hazards posed by polluted indoor environments include allergy, infections and toxicity. Life style changes have resulted in a shift from open air environments to air tight, energy efficient, environments, in which people spend a substantial portion of their time. Most indoor air pollution comes from the hazardous non biological agents and biological agents. Fungi are ubiquitous in distribution and are a serious threat to public health in indoor environments. In this communication, we have reviewed the current status on biotic indoor air pollution, role of fungi as biological contaminants and their impact on human health.     

Microbial growth inside insulated external walls as an indoor air biocontamination source

The association between moisture-related microbial growth (mesophilic fungi and bacteria) within insulated exterior walls and microbial concentrations in the indoor air was studied. The studied apartment buildings with precast concrete external walls were situated in a subarctic zone. Actinomycetes in the insulation layer were found to have increased concentrations in the indoor air. The moisture content of the indoor air significantly affected all measurable airborne concentrations.     

Biodiversity of pollen in indoor air samples as revealed by DNA metabarcoding

We conducted DNA metabarcoding (based on the nuclear ITS2 region) to characterize indoor pollen samples (possibly accompanied by other plant fragments) and to discover whether there are seasonal changes in their taxonomic diversity. It was shown that DNA metabarcoding has potential to allow a good discovery of taxonomic diversity. The number of spermatophyte families and genera varied greatly among sampling sites (pooled results per building) and times, between 9–40 and 10–66, respectively. Comparable Shannon's diversity indices equaled 0.33–2.76 and 0.94–3.16. The total number of spermatophyte genera found during the study was 187, of which 43.9, 39.6, 7.5 and 9.1% represented wild, garden/crop and indoor house plants, and non‐domestic fruit or other plant material, respectively. Comparable proportions of individual sequences equaled 77.4, 18.8, 2.7 and 1.1%, respectively. When comparing plant diversities and taxonomic composition among buildings or between seasons, no obvious pattern was detected, except for the second summer, when pollen coming from outdoors was highly dominant and the proportions of likely allergens, birch, grass, alder and mugwort pollen, were very high. The average pairwise values of Sørensen_Chao indices that were used to compare similarities for taxon composition between samples among the samples from the two university buildings, two nurseries and farmhouse equaled 0.514, 0.109, 0.564, 0.865 and 0.867, respectively, while the mean similarity index for all samples was 0.524. Cleaning frequency may strongly contribute to the observed diversity. The discovery of considerable diversities, including pollen coming from outside, in both winter and summer shows that substantial amounts of pollen produced in summer enter buildings and stay there throughout the year.     

Fungal biodiversity in indoor environments in Havana, Cuba

A study was made of the indoor mycobiota in a range of public and private buildings (libraries, museums, laboratories and offices, warehouses, homes and a school) in the city of Havana (Cuba). Culturable airborne fungi were sampled using a slit-to-agar impactor (Chirana aeroscope). High levels of contamination were recorded, with more than 700 colony-forming units per cubic metre of air in 85% of the buildings sampled, and more than 1,000 in 55% of buildings. Of the 28 genera and 31 species identified, the most common were Aspergillus flavus, Aspergillus niger, Penicillium citrinum, Cladosporium cladosporioides and Cladosporium sphaerospermum. Genus and species diversity was analysed, and new findings were obtained regarding Cuba’s atmospheric ecosystem.     

Biological responses to indoor air contaminants

Summary The scientific study of indoor air quality has been a topic for research in the last two decades; in the late 70's it became an issue of general public perception. The public perceptions have been such tremendous stimuli because they involve aspects of health and welfare (comfort and economics). Various biomedical studies were performed to evaluate adverse biological effects associated with ambient and occupational pollutants. However, it became obvious that humans were exposed more, on a temporal basis, to their normal indoor environments than they were either in the workplace or outside. Concern with biological contaminants was always an issue, but rarely examined indoors until recently. Biological responses to the indoor environment will be discussed in this paper.     

Detection and enumeration of airborne biocontaminants

The sampling and analysis of airborne microorganisms has received attention in recent years owing to concerns with mold contamination in indoor environments and the threat of bioterrorism. Traditionally, the detection and enumeration of airborne microorganisms has been conducted using light microscopy and/or culture-based methods; however, these analyses are time-consuming, laborious, subjective and lack sensitivity and specificity. The use of molecular methods, such as quantitative polymerase chain reaction amplification, can enhance monitoring strategies by increasing sensitivity and specificity, while decreasing the time required for analysis.     

Fungal colonization of automobile air conditioning systems

Air samples and swab samples of the air conditioning vents were collected from 29 automobiles in the metropolitan region of Atlanta, GA, and cultured for fungi. Among the fungi observed, species of Acremonium, Aspergillus, Alternaria, Aureobasidium, Cladosporium, and Penicillium were in the highest densities. Transparent adhesive tape imprints, SEM observations, and enrichment culture of components of five systems demonstrated fungal hyphae on the metal surfaces and within the matrix of various insulation materials. The evaporator removed from one automobile because of a series of complaints of noxious odors was densely colonized by Penicillium viridicatum. The amplification of known allergenic and odor-producing fungi occurred within the automobile air conditioning systems. Received 27 May 1997/ Accepted in revised form 16 July 1997     

Fungal biodiversity in the air of Turin

The qualitative fungal composition of Turin 's atmospheric environment was surveyed, carrying out a twelve-month study and collecting with a single stage volumetric sieve sampler on Dermasel agar supplemented with 0.4 g l^–1 cycloheximide and 0.05 g l^–1 chloramphenicol. We isolated 165 species and 2 varieties of mesophilic fungi from 58 genera and 26 thermotolerant species from 12 genera. Penicillium, Aspergillus, Acremonium, Chrysosporium, Scopulariopsis, Malbranchea, Paecilomyces, Phialophora and Cladosporium were in sequence the genera most rich in mesophilic species; Aspergillus, Penicillium, Chrysosporium and Scopulariopsis the most rich in thermotolerant species. Many of the species isolated are rarely or never recorded in the atmospheric environment. Cycloheximide can thus be said to select among airborne fungi, giving a characteristic picture.Abbreviation CH Cycloheximide - cfu colony forming unit     

Microbiological indoor air quality in healthy buildings

There is a growing interest in indoor air quality for a better quality environment both at home and at work because many people spend at least 80% of their time indoors. The aim of our study was to evaluate the indoor concentration of airborne bacteria and fungi in a University auditorium, in an office of public buildings and in an apartment in the presence and in absence of building's occupants, building materials and furnishings. The concentrations of airborne bacteria and fungi were determined using a Surface Air System (SAS). In presence of people and furnishings the average air concentrations of bacteria (University auditorium: 925-1225 CFU m(-3); office: 493 CFU m(-3); apartment: 92-182 CFU m(-3)) were higher than in absence (respectively: 190-315 CFU m(-3); 126 CFU m(-3); 66-80 CFU m(-3)). The average air concentrations fungal were higher in presence of people and furnishings (University auditorium: 1256-1769 CFU m(-3); office: 858 CFU m(-3); apartment: 147-297 CFU m(-3)) than in absence (respectively: 301-431 CFU m(-3); 224 CFU m(-3); 102-132 CFU m(-3)). The obtained data can be considered as a step to identify acceptable levels for bioaerosols in common indoor environments.     

Fungal biocatalysts in the biofiltration of VOC-polluted air

Gas-phase biofilters used for the treatment of waste gases were originally packed with compost or other natural filter beds containing indigenous microorganisms. Over the past decade much effort has been made to develop new carrier materials, more performant biocatalysts and new types of bioreactors. Elimination capacities reached nowadays are 5 to 10 times higher than those originally reported with conventional compost biofilters. With the recently developed inert filter beds, inoculation is a prerequisite for successful start-up and operation. Either non-defined mixed cultures or pure bacterial cultures have originally been used. The search for efficient fungal biocatalysts started only a few years ago, mainly for the biofiltration of waste gases containing hydrophobic compounds, such as styrene, alpha-pinene, benzene, or alkylbenzenes. In this review, recently isolated new fungal strains able to degrade alkylbenzenes and other related volatile organic pollutants are described, as well as their major characteristics and their use as biocatalysts in gas-phase biofilters for air pollution control. In biofiltration, the most extensively studied organism belongs to the genus Exophiala, although strains of Scedosporium, Paecilomyces, Cladosporium, Cladophialophora, and white-rot fungi are all potential candidates for use in biofilters. Encouraging results were obtained in most of the cases in which some of those organisms were present in gas-phase biofilters. They allow reaching high elimination capacities and are resistant to low pH values and to reduce moisture content.     

Fungal spores are an important component of library air

The airborne fungal spore types were studied in different libraries in Delhi, using an Andersen sampler and a Burkard personal sampler, for culturable and non-culturable fungi respectively. The concentration inside the libraries, before and after the agitation of books, were compared with outside air. The major contributors to the library air areCladosporium, aspergilli/penicillia, smuts andAlternaria, varying from 50 to 14%. Some fungi (Cladosporium, Alternaria, smut,Penicillium chrysogenum andnigricans) showed seasonal occurrence, corresponding to their occurrence in the extramural environment. Aspergilli/penicillia,Drechslera, Curvularia andAspergillus flavus had a significantly higher concentration (P<0.01) inside the library, and recorded a significant increase in concentration after agitation of books. Air-conditioned libraries have low fungal spore concentrations, as compared to naturally ventilated libraries.     

Chemical characterization of indoor air quality in Parisian homes

Summary Air quality inside 9 homes in the Paris region was evaluated by measuring several atmospheric pollutants. In these homes interior emissions of ammonia and volatile organic compounds were obvious. Regarding other pollutants such as sulphur dioxide, nitrogen dioxide, particles, polycyclic aromatic hydrocarbons, sulphate and metals, the influence of external surrounding air remains predominant.     

Hydrogen sulfide concentrations in indoor air of thermal springs

This study aimed to assess hydrogen sulfide (H₂S) concentrations in the pool indoor air of hot springs and its link to some physicochemical properties of the springs in Ardabil province. Twenty-two hot springs from different regions were selected and monitored for H₂S concentrations using a portable gas meter. Respective mean concentrations of H₂S in hot springs indoor air were 9.11 ± 11. Ghotour Souei hot springs had the highest concentration of H₂S with a mean concentration of 29.4 ± 7.7 and 25.2 ± 8.16 ppm at the source and general pool areas, respectively. Oxidation-reduction potential and pH of the water were the most important factor influencing H₂S concentrations in the hot springs. H₂S concentrations in indoor air of Ardabil hot springs were noticeably higher than OEL-TWA and OEL-STEL, and therefore may pose important risks for human health on both short-and long-term exposures.     

Fungal CO2 sensing: a breath of fresh air

Carbon dioxide levels are used by two fungal pathogens as a key signal to choose between the expression of environmental or virulence traits. Studies now reveal that the atypical fungal adenylyl cyclases are implicated in this decision.     

Public health: Quality of indoor residential air and health

About 90% of our time is spent indoors where we are exposed to chemical and biological contaminants and possibly to carcinogens. These agents may influence the risk of developing nonspecific respiratory and neurologic symptoms, allergies, asthma and lung cancer. We review the sources, health effects and control strategies for several of these agents. There are conflicting data about indoor allergens. Early exposure may increase or may decrease the risk of future sensitization. Reports of indoor moulds or dampness or both are consistently associated with increased respiratory symptoms but causality has not been established. After cigarette smoking, exposure to environmental tobacco smoke and radon are the most common causes of lung cancer. Homeowners can improve the air quality in their homes, often with relatively simple measures, which should provide health benefits.In North America, adults spend about 87% of their time in buildings, 6% in vehicles and 7% outdoors.¹ Leech and colleagues² have reported that Canadians spend similar amounts of time indoors. Typically, more time is spent indoors in very hot or cold climates. As a result, personal exposure to airborne substances is more closely related to indoor rather than outdoor pollution.^3,4 We review the sources, health effects and control strategies for several of the most important sources of residential biological and chemical contaminants.Although outdoor and indoor environments tend to be viewed as distinct entities, some outdoor pollutants enter the home. However, less air pollution enters tightly sealed homes, such as those found in colder and hotter climates where windows and doors are more regularly closed to retain conditioned air.⁵ In addition, economically disadvantaged families may be more likely than others to live close to roadways and industry, have lower-quality housing and have less access to air conditioning, which may result in poor indoor air quality.⁶ On days with high concentrations of particulate matter, cities with a high prevalence of air conditioner use report fewer hospital admissions for cardiovascular disease, chronic obstructive pulmonary disease and pneumonia compared with cities with lower air conditioner use.⁵Indoor air pollutants include carcinogens and biological and chemical contaminants. The latter category can be divided into combustion products and gases released from indoor materials (off-gassing emissions). Several guidelines for exposure limits for indoor air contaminents have been developed by the Canadian government (Open in a separate window