Indoor climate and air quality

 In industrialized countries about 90% of the time is spent indoors. The ambient parameters affecting indoor thermal comfort are air temperature and humidity, air velocity, and radiant heat exchange within an enclosure. In assessing the thermal environment, one needs to consider all ambient parameters, the insulating properties of the occupants’ clothing, and the activity level of the occupants by means of heat balance models of the human body. Apart from thermal parameters, air quality (measured and perceived) is also of importance for well-being and health in indoor environments. Pollutant levels are influenced by both outdoor concentrations and by indoor emissions. Indoor levels can thus be lower (e.g. in the case of ozone and SO₂) or higher (e.g. for CO₂ and formaldehyde) than outdoor levels. Emissions from cooking play an important role, especially in developing countries. The humidity of the ambient air has a wide range of effects on the energy and water balance of the body as well as on elasticity, air quality perception, build-up of electrostatic charge and the formation or mould. However, its effect on the indoor climate is often overestimated. While air-handling systems are commonly used for achieving comfortable indoor climates, their use has also been linked to a variety of problems, some of which have received attention within the context of ”sick building syndrome”. Received: 27 October 1997 / Accepted 26 November 1997     

Indoor and outdoor winter activity of Culicoides biting midges,vectors of bluetongue virus,in Italy

Indoor and outdoor winter activity of Culicoides spp. (Diptera: Ceratopogonidae) in central Italy was investigated in order to evaluate whether indoor activity might account for the overwintering of bluetongue virus, as has been hypothesized by some authors. Weekly Culicoides collections were performed at three farms over three consecutive winter seasons. At each farm, two black‐light traps were operated simultaneously, indoors and outdoors. Culicoides were identified using both morphological and molecular means. The Culicoides obsoletus group accounted for 98.2% of sampled specimens. Within this group, C. obsoletus s.s. accounted for 56.8% and Culicoides scoticus for 43.2% of samples. Nulliparous, parous and engorged females were caught throughout the entire winter, both indoors and outdoors. At times, indoor catch sizes outnumbered outdoor collections. A significant inverse correlation was found between minimum temperature and the proportion of indoor Culicoides of the total midge catch, thus indicating that lower outdoor temperatures drive Culicoides midges indoors. High rates of engorged females were recorded indoors, possibly as the result of the propensity of C. obsoletus females to feed indoors. Higher proportions of parous females were found in indoor than in outdoor catches, indicating higher survival rates indoors and, consequently, higher vectorial capacities of midges sheltering indoors compared with those remaining outdoors.     

Air spore microfungi in dwellings of south of Spain

Summary Indoor and outdoor airborne microfungi were studied in fourteen homes of Córdoba (Spain) for two years. Samplings were done gravimetrically in three rooms in each home and, for comparison, also outdoors. An overall 128 taxa were identified, which were classified according to their occurrence into occasional, frequent and permanent. No statistically significant quantitative differences were found between the microfungi in each room. On the other hand, there were significant quantitative differences between indoor and outdoor microfungi. Spores occurred at their maximum concentrations in spring. Finally,Aspergillus andCladosporium were found to be the most abundant genera indoors and outdoors, respectively.     

Air pollution and the lung: epidemiological approach

Epidemiological evidence has concurred with clinical and experimental evidence to correlate current levels of ambient air pollution, both indoors and outdoors, with respiratory effects. In this respect, the use of specific epidemiological methods has been crucial. Common outdoor pollutants are particulate matter, nitrogen dioxide, carbon monoxide, volatile organic compounds and ozone. Short-term effects of outdoor air pollution include changes in lung function, respiratory symptoms and mortality due to respiratory causes. Increase in the use of health care resources has also been associated with short-term effects of air pollution. Long-term effects of cumulated exposure to urban air pollution include lung growth impairment, chronic obstructive pulmonary disease (COPD), lung cancer, and probably the development of asthma and allergies. Lung cancer and COPD have been related to a shorter life expectancy. Common indoor pollutants are environmental tobacco smoke, particulate matter, nitrogen dioxide, carbon monoxide, volatile organic compounds and biological allergens. Concentrations of these pollutants can be many times higher indoors than outdoors. Indoor air pollution may increase the risk of irritation phenomena, allergic sensitisation, acute and chronic respiratory disorders and lung function impairment. Recent conservative estimates have shown that 1.5-2 million deaths per year worldwide could be attributed to indoor air pollution. Further epidemiological research is necessary to better evaluate the respiratory health effects of air pollution and to implement protective programmes for public health.     

Indoor and outdoor pollen concentrations in private and public spaces during the <Emphasis Type="Italic">Betula</Emphasis> pollen season

Although the number of studies of pollen concentrations inside and outside buildings is increasing, little is known about the efficiency of penetration of pollen from outdoor to indoor air, and further. We studied indoor and outdoor pollen concentrations in the town of Lappeenranta and in the municipality of Rautjärvi in SE Finland from May 3–23, 2004, i.e. throughout the Betula pollen season, and assessed the risk of exposure to pollen grains. Pollen concentrations were measured inside and outside a block of flats, a detached house, and the regional central hospital, using rotorod-type samplers; in the town of Joutseno data were compared with Burkard counts. Outdoor concentrations of Betula pollen grains ranged between low and abundant (0–855 grains m^?3). The corresponding indoor concentrations near the main front doors varied from low to moderate (0–17 grains m^?3) in the central hospital and were low (<10 grains m^?3) in both residential buildings. Indoor concentrations further from the main front door were low (<10 grains m^?3) at all study sites. The concentrations of Betula pollen decreased substantially from outdoors to indoors, and further toward the centre of the building, probably indicating relatively poor penetrating properties of the pollen grains and/or the short-lived presence of pollen grains in indoor air. The concentrations of Betula pollen inside the buildings during the peak flowering period were mostly at a level barely inducing reactions even in the most sensitive persons.     

Estimating Mortality Derived from Indoor Exposure to Particles of Outdoor Origin

Following an extensive review of the literature, we further analyze the published data to examine the health effects of indoor exposure to particulate matter (PM) of outdoor origin. We obtained data on all-cause, cardiovascular, and respiratory mortality per 10 μg/m³ increase in outdoor PM₁₀ or PM_2.5; the infiltration factors for buildings; and estimated time spent outdoors by individuals in the United States, Europe, China, and globally. These data were combined log-linear exposure–response model to estimate the all-cause, cardiovascular, and respiratory mortality of exposure to indoor PM pollution of outdoor origin. Indoor PM pollution of outdoor origin is a cause of considerable mortality, accounting for 81% to 89% of the total increase in mortality associated with exposure to outdoor PM pollution for the studied regions. The findings suggest that enhancing the capacity of buildings to protect occupants against exposure to outdoor PM pollution has significant potential to improve public health outcomes.     

The incidence of fungal spores in the ambient air and inside homes: Evidence from London

Little research has been carried out in London concerning fungal spore prevalence yet this information may help to elucidate geographical patterns of asthma and hay fever. Although many types of spore reach peak concentrations outdoors in late-summer, the incidences in the indoor environment may be more important through the winter because of heating and poor ventilation. Daily average concentrations of fungal spores in the ambient atmosphere were monitored with a Burkard volumetric spore trap on an exposed roof in North London from autumn 1991 until the summer of 1992. Indoor spore measurements were taken in 19 homes in the vicinity through the winter months, both by direct air sampling using a portable Burkard sampler and by dust culture. Trends in the occurrence and concentrations of fungal spores indoors and outdoors were examined. Relationships between the abundance of selected allergenic fungi and features of the houses were analysed including age of dwelling, dampness, cleanliness and presence of pets.Aspergillus andPenicillium were the most frequently occurring spore types in the homes. Overall, high spore incidence was associated with dampness and dust accumulation. The outdoor spore samples revealed generally low concentrations through the winter until March when concentrations of many types includingCladosporium, Epicoccum andAlternaria increased in abundance in response to the warmer weather. Even during the late-spring and early-summer, concentrations of most fungal spores were notably below those reported for rural sites.     

Characterization of aerobic bacterial and fungal microbiota on surfaces of historic Scottish monuments

Twenty samples were taken from the inner or outer surfaces of stone monuments of six historic Scottish buildings and ruins. Biofilms developing on mineral substrates were analysed by in situ scanning electron microscopy and cultivation. Various methods were used to characterize the isolates including automated ribotyping, RAPD and sequencing of the 16S rRNA gene for bacteria, and stereomicroscopy and sequencing of the Internal Transcribed Spacers (ITS) for fungi. Most samples contained microbes between 10(5) and 10(7)cfug(-1) substrate. Actinobacteria belonging to the genus Streptomyces (17 samples/5 monuments) or Arthrobacter (12/3) and Pseudomonas (9/3) were frequently detected. Most streptomycetes were in terms of their 16S rRNA gene sequence most closely related to S. microflavus (10/3) or to the undescribed species S. "vulgaris" (8/3). Indoor and outdoor biofilms exhibited significant differences in their microbiota, as shown by both microscopy and isolation studies. Pigmented coccoid Arthrobacter species were typical for the outdoor samples, whereas Pseudomonas species were common in the indoor samples. Based on the low phylogenetic relationship to a known species (type strain), potential novel pigmented bacterial species belonging to the genera Arthrobacter, Brevundimonas, Cryseobacterium, Deinococcus and Dyadobacter were detected from the outdoor samples and to Pseudomonas from the indoor samples. Hyaline fungal species of Acremonium (10/4) mainly occurred in indoor samples, whereas pigmented species of Cladosporium (8/3), Penicillium (6/3) and Phialophora (6/2) were found outdoors. Using in situ microscopy diatom algae were also detected.     

(1 → 3)-β-<Emphasis Type="SmallCaps">d</Emphasis>-glucan in different background environments and seasons

This study was undertaken to investigate how the length of the extraction period influences the (1 → 3)-β-d-glucan (β-glucan) yield and also to examine the background concentration of β-glucan as airborne β-glucan in outdoor environments in different seasons and as concentrations in airborne and floor dust in offices. To ensure compatibility between results obtained in different laboratories, it is important to use optimal and standardised methods to extract and quantify β-glucan. In this study, an extraction period of 60 min gave the highest β-glucan yield. The median concentration of β-glucan in 44 floor dust samples was 597 μg g⁻¹ dust. The median concentration of airborne β-glucan in offices was 5.1 ng m⁻³ in the summer and 2.3 ng m⁻³ in the winter, and the outdoor median concentration in towns was 6.8 ng m⁻³. The outdoor airborne concentration of β-glucan was significantly lower in January, November and December than during the rest of year. In July, the median airborne concentration of β-glucan was 14 times higher than in January. Furthermore, the airborne concentration of β-glucan was significantly higher in July than in March, April, May, September and October. In the summertime, we found that the indoor airborne concentration of β-glucan was lower than outdoor concentrations. This is in accordance with measurements of concentrations of airborne pollen and culturable fungal spores showing higher outdoor than indoor concentrations during the summer months.     

Indoor and outdoor levels,sources, and health risk assessment of mercury in dusts from a coal-industry city of China

To understand the mercury (Hg) pollution characteristics and health risks in indoor and outdoor dust of Huainan residential areas, 122 dust samples were collected indoors and outdoors. Average Hg contents in indoor and outdoor dusts of Huainan city were 0.321 ± 0.724 (n = 61) and 0.072 ± 0.163 (n = 61) mg/kg respectively. The average Hg content in indoor dust was characterized by PJ (Panji district) > XJJ (Xiejiaji district) > DT (Datong district) > TJA (Tianjiaan district), and in the order of PJ > DT > XJJ >TJA in outdoor dust. According to enrichment factor and geo-accumulation index, the enrichment degree and pollution intensity for Hg are ranked as “very high enrichment” and “heavily polluted” in indoor dust, and “significant enrichment” and “moderately polluted” in outdoor dust Hg concentrations in indoor dust were highly significantly associated with the coal combustion and frequency of open windows, and Hg concentrations in outdoor dust were significantly associated with the coal combustion and traffic density. The inhalation of Hg vapor is the main route of Hg exposure to adult and children. The hazard risks of Hg for different exposure ways in indoor and outdoor dust were more risk for children than for adults, but have no obvious health risk for them.     

Dispersal in microbes: fungi in indoor air are dominated by outdoor air and show dispersal limitation at short distances

The indoor microbiome is a complex system that is thought to depend on dispersal from the outdoor biome and the occupants'' microbiome combined with selective pressures imposed by the occupants'' behaviors and the building itself. We set out to determine the pattern of fungal diversity and composition in indoor air on a local scale and to identify processes behind that pattern. We surveyed airborne fungal assemblages within 1-month time periods at two seasons, with high replication, indoors and outdoors, within and across standardized residences at a university housing facility. Fungal assemblages indoors were diverse and strongly determined by dispersal from outdoors, and no fungal taxa were found as indicators of indoor air. There was a seasonal effect on the fungi found in both indoor and outdoor air, and quantitatively more fungal biomass was detected outdoors than indoors. A strong signal of isolation by distance existed in both outdoor and indoor airborne fungal assemblages, despite the small geographic scale in which this study was undertaken (<500 m). Moreover, room and occupant behavior had no detectable effect on the fungi found in indoor air. These results show that at the local level, outdoor air fungi dominate the patterning of indoor air. More broadly, they provide additional support for the growing evidence that dispersal limitation, even on small geographic scales, is a key process in structuring the often-observed distance–decay biogeographic pattern in microbial communities.     

Indoor intake fraction considering surface sorption of air organic compounds for life cycle assessment

Purpose

Life cycle assessment (LCA) has largely focused on characterizing the impact of outdoor emissions. However, the intake fraction (iF) of indoor air emissions could be more important. The present paper aims to determine the long-term intake fractions of indoor emissions, including multiple indoor removal pathways such as sorption on indoor surfaces, and to compare it to the outdoor intake fraction.

Method

The developed model accounts for the different removal pathways in buildings, including air exchange, degradation in the gas phase, degradation on surfaces, and finally partitioning between air, walls, and furniture assuming a kinetically limited material transfer between gas phase and a near-surface film. The indoor intake fraction is presented as a function of the adsorption and degradation rate on surfaces.

Results and discussion

The intake fraction of volatile substances is only affected by the ventilation rate, with a constant intake fraction of 1?×?10^?2. For ozone-sensitive substances, indoor gas phase reactions can significantly reduce the intake fraction. Semi-volatile substances are affected by the adsorption and degradation on room surfaces. For highly adsorbing substances, the decrease in intake fraction is limited to a minimum value of 2.5?×?10^?4 by the mass transfer rate between air and room surfaces for a typical office or residence room in developed countries with temperate climate. Indoor intake fraction is compared to outdoor intake fraction calculated using the Impact 2002 multimedia model. Typical calculated indoor intake fraction values are in a significantly higher range (2.5?×?10^?4 to 1?×?10^?2) than inhalation outdoor values (1?×?10^?9 to 1?×?10^?6).

Conclusions

This paper opens new possibilities to assess the health impact of indoor and outdoor air emissions in a consistent way, including surface sorption??a major removal pathway for semi-volatile compounds. By combining the newly calculated intake fractions with effect factors and with indoor and outdoor emissions per functional unit, it becomes possible to consistently account for indoor exposure in methods such as LCA     

3D simulations for evaluation of location factors in an urban environment: application of a novel methodology to calculate external exposure doses for evacuees from Pripyat

This article presents a methodology for assessing the radiation doses in an urban environment due to external irradiation from radionuclides deposited on the ground and other surfaces as well as from a passing radioactive cloud. The approach was developed and applied to assess individual doses of residents of the town of Pripyat who were evacuated shortly after the Chernobyl accident. Typically, the so-called location factor is defined as the ratio of the dose rate at a point of exposure and the dose rate at an undisturbed lawn far from any buildings. The present study used a new definition of the location factor as a regular four-dimensional grid of ratios of air kerma rates indoors and outdoors distributed in space and time. The location factors were calculated for two scenarios: outdoor and indoor values for typical apartments and buildings in Pripyat. Indoor location factors varied within two orders of magnitude depending on the floor of residence and place of staying inside the apartment. Values of the indoor location factor differed during the daytime and night by a factor of 30–40 depending on the behaviour of an individual within the apartment. Both, outdoor and indoor location factors decreased with decreasing distances between buildings. It was shown that during the first 4 days after the accident, air kerma rates in Pripyat were governed by the radionuclides deposited on the ground surface, and not by radionuclides in the cloud. Specifically, the contribution of the radioactive cloud to air kerma rate was maximal (i.e., 2.3%) on the morning of 28 April 1986. The methodology and results of this study are currently being used to reconstruct the radiation gonadal dose for the subjects of the American–Ukrainian study of parental irradiation in Chernobyl cleanup workers and evacuees for investigating germline mutations in their offspring.

     

Airborne bacteria and fungal spores in the indoor environment. A case study in Singapore

The concentration of airborne fungal spores and bacteria as related to room temperature, humidity and occupancy levels within a library building in Singapore was determined. Measurement of indoor air quality with respect to microorganisms is of particular importance in tropical environments due to the extensive use of air‐conditioning systems and the potential implications for human health. This study has revealed a number of interesting relationships between the concentrations of fungal spores and bacteria in relation to both environmental and human factors. The levels of fungal spores measured in the indoor environment were approximately fifty times lower than those measured outside, probably because of the lowered humidity caused by air‐conditioning in the indoor environment. The variation in fungal spore concentration in the outdoor environment is likely to be due to the diurnal periodicity of spore release and the response to environmental factors such as light temperature and humidity. The indoor concentration of fungal spores in air was not clearly correlated to concentrations measured in air outside of the library building and remained relatively constant, unaffected by the difference in the numbers of occupants in the library. In contrast, the indoor concentrations of bacteria in air were approximately ten times higher than those measured outdoors, indicating a signficant internal source of bacteria. The elevated levels of indoor bacteria were primarily attributed to the number of library occupants. Increased human shedding of skin cells, ejection of microorganisms and particulates from the respiratory tract, and the transport of bacteria on suspended dust particles from floor surfaces probably accounts for the strong positive correlation between occupancy levels and the concentration of bacteria in internal air.     

Growth and fermentation responses of Selenomonas ruminantium to limiting and non-limiting concentrations of ammonium chloride

 The objective of this study was to assess fermentation product, growth rate and growth yield responses of Selenomonas ruminantium HD₄ to limiting and non-limiting ammonia concentrations. The ammonia half-inhibition constant for S. ruminantium in batch culture was 296 mM. Cells were grown in continuous culture with a defined ascorbate-reduced basal medium containing either 0.5, 5, 25, 50, 100 or 200 mM NH₄Cl and dilution rates were 0.07, 0.14, 0.24 or 0.40 h^-1. Ammonia was the growth-limiting nutrient when 0.5 mM NH₄Cl was provided and the half-saturation constant was 72 μM. Specific rates of glucose utilization and fermentation acid carbon formation were highest for 0.5 mM NH₄Cl. Lactate production (moles per mole of glucose disappearing) increased at the fastest dilution rate (0.40 h^-1) for 5.0 mM NH₄Cl while acetate and propionate decreased when compared to slower dilutions (0.07 and 0.14 h^-1). Lactate production remained low while acetate and propionate remained high for all dilution rates when NH₄Cl concentrations were 25 mM or greater. Yield (Y _Glc and Y _ATP) were nearly doubled when NH₄Cl was increased from 0.5 mM (25.1 g cells/mol glucose used and 13.9 g cells/mol ATP produced respectively) to the higher concentrations. Y _Glc was highest at 25 mM and 50 mM NH₄Cl (48.2 cells/mol and 43.1 cells/mol respectively) as was Y _ATP (23.2 cells/mol and 20.8 cells/mol respectively). Y _NH3 was highest at the lowest NH₄Cl concentration. The maximal fermentation product formation rate occurred at a growth-limiting ammonia concentration, while maximal glucose and ATP bacterial yields occurred at non-growth-limiting ammonia concentrations. Given the growth response of this ruminal bacterium, it is possible that maximization of ruminal bacterial yield may necessitate sacrificing the substrate degradation rate and vice versa. Received: 5 December 1995/Received revision: 2 April 1996/Accepted: 22 April 1996     

Status of airborne spores and pollen in a coir factory in Kerala,India

The prevalence of airborne fungal spores and pollen grains in the indoor and outdoor environments of a coir factory in Thiruvananthapuram district of Kerala state, India was studied using the Burkard Personal Sampler and the Andersen 2-stage Sampler for 2 years (September 1997 to August 1999). The concentration of pollen grains was remarkably lower than that of fungal spores (ratio of 1:28). There was no large difference in the concentrations and types of fungal spores between the indoor and outdoor environments, with 26 spore types found to be present indoors and 27 types outdoors; of these, 22 were common to both the environments. Aspergillus/Penicillium, Cladosporium, ‘other basidiospores’ and ascospores were the dominant spore types. The total spore concentration was highest in February and lowest in September, and it was significantly higher in 1998–1999 than in 1997–1998. Twenty viable colony-forming types were isolated from inside the coir factory. The most dominant viable fungi isolated were Penicillium citrinum, Aspergillus flavus and Aspergillus niger. The total pollen concentration was higher in the outdoor environment of the coir factory than indoors, with 15 and 17 pollen types, respectively. Grass and Cocos nucifera pollen types were dominant. The dominant spore and pollen types trapped in the two environments of the coir factory are reportedly allergenic and, consequently, workers are at risk of catching respiratory/allergic diseases.     

Relationship between indoor and outdoor airborne fungal spores, pollen, and (1→3)-β-D-glucan in homes without visible mold growth

In this exploratory study, indoor and outdoor airborne fungal spores, pollen, and (1→3)-β-D-glucan levels were determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected in five Cincinnati area homes that had no visible mold growth. The total count of fungal spores and pollen in the collected samples was conducted under the microscope and Limulus Amebocyte Lysate (LAL) chromogenic assay method was utilized for the determination of the (1→3)-β-D-glucan concentration. For the combined number concentration of fungal spores and pollen, the indoor and outdoor geometric mean values were 573 and 6,435 m⁻³, respectively, with a geometric mean of the Indoor/Outdoor (I/O) ratio of .09. The geometric means of indoor and outdoor (1→3)-β-D-glucan concentrations were .92 and 6.44 ng m⁻³, respectively, with a geometric mean of the I/O ratio equal to .14. The I/O ratio of (1→3)-β-D-glucan concentration was found to be marginally greater than that calculated based on the combined number concentration of fungal spores and pollen. This suggests that (1→3)-β-D-glucan data are affected not only by intact spores and pollen grains but also by the airborne fragments of fungi, pollen, and plant material, which are ignored by traditional enumeration methodologies. Since the (1→3)-β-D-glucan level may elucidate the total exposure to fungal spores, pollen, and fungal fragments, its I/O ratio may be used as a risk marker for mold and pollen exposure in indoor environments.     

Considerations in the grouping of plant and fungal taxa for an epidemiologic study

Although exposure to airborne pollen grains and fungal spores has been implicated as a causative factor for acute exacerbation of asthma, the few epidemiologic studies that have attempted to evaluate the relationship between these bioaerosols and asthma have used only total counts (ignoring the relative importance of different taxa) or a few predominant pollen or spore types (ignoring less abundant but potentially relevant groups). This paper reports the development of hypothesis‐driven exposure metrics (based on known aeroallergen associations with allergic asthma and other hypersensitivity diseases, pollen allergen cross‐reactivity, and the presence of local sources in the city of Fresno, California, USA) for a 3.5 year epidemiologic study of childhood asthma. Outdoor regional and neighborhood concentrations of pollen and spores were measured using Hirst‐type, 7‐day samplers. Indoor and outdoor residential concentrations were measured at 84 selected homes with similar 24‐hour slit impactors. All pollen and spore concentrations were recorded in 2‐hour intervals to assist in understanding diurnal fluctuations in aeroallergen concentrations, identify exposures during the time periods that children are outdoors, and study interaction between aeroallergens and other air contaminants, which were the primary focus of the study. The 124 pollen taxa that were observed were reduced to 15 categories and the 66 fungal and algal taxa were reduced to five categories that will be used in microenvironmental models to generate individual daily exposure estimates for each of the 315 children. These new exposure metrics will allow examination of health effects for taxa traditionally associated with allergy and those with locally elevated concentrations in combination with exposures to other indoor and outdoor air contaminants.     

Indoor and outdoor atmospheric fungal spores in the São Paulo metropolitan area (Brazil): species and numeric concentrations

The aim of this study was to estimate the indoor and outdoor concentrations of fungal spores in the Metropolitan Area of Sao Paulo (MASP), collected at different sites in winter/spring and summer seasons. The techniques adopted included cultivation (samples collected with impactors) and microscopic enumeration (samples collected with impingers). The overall results showed total concentrations of fungal spores as high as 36,000 per cubic meter, with a large proportion of non culturable spores (around 91% of the total). Penicillium sp. and Aspergillus sp. were the dominant species both indoors and outdoors, in all seasons tested, occurring in more than 30% of homes at very high concentrations of culturable airborne fungi [colony forming units(CFU) m⁻³]. There was no significant difference between indoor and outdoor concentrations. The total fungal spore concentration found in winter was 19% higher than that in summer. Heat and humidity were the main factors affecting fungal growth; however, a non-linear response to these factors was found. Thus, temperatures below 16°C and above 25°C caused a reduction in the concentration (CFU m⁻³) of airborne fungi, which fits with MASP climatalogy. The same pattern was observed for humidity, although not as clearly as with temperature given the usual high relative humidity (above 70%) in the study area. These results are relevant for public health interventions that aim to reduce respiratory morbidity among susceptible populations.     

Degradation of anthracene by laccase of Trametes versicolor in the presence of different mediator compounds

 Laccase of Trametes versicolor was generally able to oxidize anthracene in vitro. After 72 h incubation about 35% of the anthracene was transformed stoichiometrically to 9,10-anthraquinone. Transformation of anthracene increased rapidly in the presence of different mediators that readily generate stable radicals: 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and 1-hydroxybenzotriazole. For the reaction, the presence of both the laccase and the mediator was necessary. In the presence of 0.005 mM 1-hydroxybenzotriazole this conversion had removed 47% of the anthracene after 72 h; 75% of the substrate was oxidized during this period when ABTS (1 mM) was used as mediator. In contrast to reactions without or with only low concentrations of a mediator, there was a discrepancy between the disappearance of anthracene and the formation of 9,10-anthraquinone in mediator-forced reactions. Coupling-products of mediators with anthracene degradation products were found. Anthracene disappeared nearly completely after incubation for 72 h with laccase in a 0.1 mM solution of 1-hydroxybenzotriazole and was transformed to 9,10-anthraquinone in about 80% yield; 90% of the substrate was transformed in the presence of ABTS (2.0 mM) resulting again in 80% quinone. Phenothiazine was not effective in this system. Received: 9 April 1996/Received last revision: 7 June 1996/Accepted: 10 June 1996