A study of air particulate pollution in colombo using a nuclear-related analytical technique

Air particulate matter of two size fractions (coarse [2.5–10 Μm] and fine [less than 2.5 Μm]) were collected at an urban residential site (Colombo University ground) over a period of 12 mo during 1996 using a Gent PM10 stacked filter unit. Seventy-five sets of samples collected during this period were analyzed for 10 elements: Al, Si, K, S, Ca, Ti, Fe, Zn, Br, and Pb by energy-dispersive X-ray fluorescence, which is a multielement analysis. This is a highly sensitive technique enabling quantitative analysis of very low masses. The average concentrations of lead, sulfur, and bromine, which are generally associated with combustion products of automotive exhausts, dominate the fine fraction in this study. The minimum and maximum concentration of lead resulting in an annual average of 0.09 Μg/m³ was found to be 0.0042 and 0.441 Μg/m³ in particulate matter with less than 10 Μm equivalent aerodynamic diameter. The maximum concentration determined is well below the limits set by the World Health Organization (0.5–1.0 Μg/m³). The recommended value for Pb in Sri Lanka is 0.5 Μg/m³. Al, Si, Ca, Ti, and Fe exhibited enhanced concentrations in the coarse fraction, which probably originate from disturbed soil as a result of wind and traffic.     

Matrix effects in PIXE analysis of aerosols and ashes

A comparison of instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) results for sizefractionated atmospheric aerosols (“coarse” and “fine” fractions with an equivalent aerodynamic diameter of 2–10 Μm and < 2 Μm, respectively, or the PM10 fraction) showed that PIXE yielded significantly lower results for the PM10 and coarse fractions, especially for elements with a low Z resulting from a particle size effect. Somewhat lower PIXE results were also obtained for the fine fraction of atmospheric aerosols. A correction is also needed for irregularly shaped deposits of combustion aerosols collected by a cascade impactor in 11 size fractions ranging from 0.016 to 14.3 Μm, as well as for thick samples of fly and bottom ashes. An equivalent layer thickness (ELT) model is proposed to correct the matrix effects in PIXE. The approaches for the calculation of ELT using a comparison of PIXE and INAA results or by comparing PIXE results obtained using two different incident proton beam energies (1.31 and 2.35 MeV) are described. The correction for the ash pellets and irregular deposits are also discussed.     

Analysis and tracing of polycyclic aromatic hydrocarbons and mutagenicity of airborne particulates from the Taipei area

In a 3-year study, we determined the mutagenicity and polycyclic aromatic hydrocarbons (PAHs) of airborne particulates collected during December 1987-September 1988 (216 samples), October 1988-January 1989 (81 samples), and October 1989-April 1990 (52 samples) from 9 locations in the Taipei area. We found that dichloromethane extracts of all the samples were mutagenic to Salmonella typhimurium in the Ames test. Moreover, the mutagenicity was much higher in the presence of rat liver microsomal fraction (S9 mixture) than that observed in its absence, which indicates that airborne particulates contained both direct and indirect mutagens. The average mutagenicity of the samples collected in the 3-year period was 137, 127, and 118 histidine revertants/10 m3 air, respectively. On the other hand, we found that dichloromethane extracts of each airborne particulate sample contained 14 PAHs with wide variations in concentration and relative distribution. The levels of Pha, Flu, Pyr, and Ben were much higher than the PAHs with higher ring numbers such as BaP, BeP, Pr, IP, and DbA. The average PAH content was 8.0, 5.0, and 7.8 ng/m3 air for airborne particulates collected during December 1986-September 1987, October 1988-January 1989, and October 1989-April 1990, respectively. Among the 9 stations, Fu Hsing Elementary School and Chung Hsing University (Taipei campus), which are, respectively, located in the downtown area and a heavy traffic zone, had significantly higher levels of mutagenicity and PAHs than did the other stations. Moreover, comparative analysis of PAH levels of airborne particulates over the 3-year period revealed an interesting season-dependent change of PAH content in airborne particulates from the Taipei area. The concentrations of individual and total PAHs were consistently lower in the summer than those in the winter. A similar pattern of seasonal change was also observed in the mutagenicity of airborne particulate samples examined. It is worth mentioning that neither PAH level nor mutagenicity of airborne particulates showed significant yearly change over the 3-year period of study. As part of an effort to identify pollution sources, we examined the mutagenicity and PAH compounds of air particulates collected from the burning of garbage (14 samples) and motor-vehicle exhaust in the Hsin Hai Tunnel (17 samples), Taipei. The results showed that garbage burning gave rise to air particulates containing several hundred times higher levels of PAHs and about 20 times stronger mutagenicity, while the motor-vehicle exhaust contained about ten times higher PAH content and mutagenicity as compared with those of airborne particulates of the Taipei city.(ABSTRACT TRUNCATED AT 400 WORDS)     

Air quality status in Kinshasa as determined by instrumental neutron activation analysis,atomic absorption spectrometry,and ion-exchange chromatography

Three independent analytical techniques: instrumental neutron activation analysis, atomic absorption spectrometry, and ion-exchange chromatography were applied to airborne particulates collected on filters, and to atmospheric acid gases collected in carbonate buffer solutions. Twenty trace elements and seven acid gases and acid aerosols were determined. Results were compared with those observed elsewhere and showed that air pollution is low in Kinshasa and should not cause anxiety. The main known sources of pollutants are vehile exhaust and aeolian processes on stripped soils.     

Occurrence of airborne algae within the township of Bukit Jalil in Kuala Lumpur,Malaysia

There have been relatively few studies on airborne algae although they are known to have health implications. The aim of this study was to conduct a survey on the distribution of airborne algae within Bukit Jalil in Kuala Lumpur, Malaysia. The sampling sites included a quiet residential area, a busy area with high human movement, a highway with heavy traffic, small roads with low traffic, a golf course, two hilly areas, and the man-made lake, Tasik Komanwel. Soils were also collected from these sites when possible. Results based on cultured samples showed that cyanobacteria were the dominant airborne algae, with a total of eight species identified. The dominant species was Phormidium tenue while other airborne algae found included P. retzii, Nostoc commune, and N. linckia. The sites with high percentage occurrence of airborne algae were near the animal holding facility of the International Medical University and the Light Railway Transit station. Human movement could be an important factor affecting the occurrence of airborne algae. A very low occurrence of airborne algae was recorded at the sites around the lake area. Some of the airborne algae were also found in the soil samples, suggesting that the algae could originate from the soil.     

Ochratoxin A in airborne dust and fungal conidia

Farm workers are often exposed to high concentrations of airborne organic dust and fungal conidia, especially when working with plant materials. The purpose of this investigation was to study the possibility of exposure to the mycotoxin ochratoxin A (OTA) through inhalation of organic dust and conidia. Dust and aerosol samples were collected from three local cowsheds. Aerosol samples for determination of total conidia and dust concentrations were collected by stationary sampling on polycarbonate filters. Total dust was analysed by gravimetry, and conidia were counted using scanning electron microscopy. A method was developed for extraction and determination of OTA in small samples of settled dust. OTA was extracted with a mixture of methanol, chloroform, HCI, and water, purified on immunoaffinity column, and analysed by ion-pair HPLC with fluorescence detection. Recovery of OTA from spiked dust samples (0.9–1.0 μg/kg) was 74% (quantitation limit 0.150 μg/kg). OTA was found in 6 out of 14 settled dust samples (0.2–70 μg/kg). The total concentration of airborne conidia ranged from < 1.1 × 10⁴ to 3.9 × 15⁵ per m³, and the airborne dust concentration ranged from 0.08 to 0.21 mg/m³. Conidia collected from cultures of Penicillium verrucosum and Aspergillus ochraceus contained 0.4–0.7 and 0.02–0.06 pg OTA per conidium, respectively. Testing of conidial extracts from these fungi in a Bacillus subtilis bioassay indicated the presence of toxic compounds in addition to OTA. The results show that airborne dust and fungal conidia can be sources of OTA. Peak exposures to airborne OTA may be significant, e.g., in agricultural environments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Multielement compositions of marine phytoplankton samples from coastal areas of japan by instrumental neutron activation analysis

Phytoplankton samples were collected during spring bloom of diatoms from three coastal areas of Japan using a NORPAC P-25 net (25-Μm opening) with a NGG52 prenet (335-Μm opening), and 25 major and trace elements have been analyzed by INAA. Concentration ranges of analyzed phytoplankton samples are much wider than the concentration ranges compiled by Bowen (1979) except for As, and data of marine phytoplankton samples for Br, Sb, Hf, Sc, La, Ce, Sm, and Eu were not included in the compilation. The 25 analyzed elements have been categorized into three groups: elements showing positive correlation with Br, positive correlation with Al, and no positive correlation with Br or Al. The marine phytoplankton samples have been plotted on a Masuzawa-Koyama-Terazaki (MKT) plot and it proved that the MKT plot is applicable to marine phytoplankton samples.     

Transport of microorganisms to Israel during Saharan dust events

Dust storms are serious meteorological events that affect the East Mediterranean region, primarily during the spring season. The physical and chemical nature of dust storms, their origin, and the meteorological conditions leading to the generation of storms have been fully documented, but knowledge on their biological content is almost nonexistent. Four dust events that occurred in the period 2004–2005 were sampled in Haifa, Israel, an urban area on the East Mediterranean coast, for biological characterization. Samples were taken before or after (depending on the meteorological conditions) as well as during the dust events. Dust particles were collected as two size fractions using a dichotomous sampler, and their elemental content was determined using X-ray fluorescence analyses. Airborne bacteria and fungi were collected with the Six Stage Andersen Viable Impactor. Fungi were identified by optical microscopy. Compared to adjacent clear days, there was an increase in the concentration of both atmospheric particles and elements of geological and marine origin during the dust events. The concentration of airborne microorganisms during the dust events was also higher, and the fungal population content was affected. On a winter clear day the abundant airborne fungi were Paecilomyces variotii, Penicillium glabrum, and Alternaria alternata. On a spring clear day, the persisting airborne fungi were Alternaria alternata, Geotrichum candidum, Penicillium chrysogenum, and P. glabrum. However, during two dust events the fungal population was dominated by Alternaria alternata, Aspergillus fumigatus, A. niger, A. thomii, Cladosporium cladosporioides, Penicillium chrysogenum, and P. griseoroseum. This study suggests that Saharan and other desert dust events in the East Mediterranean have a significant effect on the airborne microbial populations, which might impact on health, agriculture, and ecology.     

Comparative study of sister-chromatid exchanges and chromosomal aberrations induced by airborne particulates from an urban and a highly industrialized location in human lymphocyte cultures

Cytogenetic effects induced by extracts of airborne particulates in human lymphocyte cultures were studied with regard to local and seasonal variations. Samples of airborne particulates were collected from an urban and a highly industrialized area in March and October, respectively. All extracts of particulates induced a significant increase of sister-chromatid exchanges (SCE) in a dose-dependent manner. Referring to the induction of sister-chromatid exchanges, local and seasonal differences were observed. Samples from the industrialized area revealed the highest activities. In addition, SCE rates found for March samples were always higher than those for October for both locations. Furthermore, a remarkable, significant induction of chromosomal aberrations occurred with all samples from both locations and sampling periods. Aspects of health risk evaluation for exposed human populations are discussed with respect to the observed cytogenetic effects of airborne particulates in human lymphocyte cultures.     

Low environmental selenium availability as an additional determinant for goiter in East Java, Indonesia?

Iodine deficiency, which is most visibly indicated by goiter, is highly prevalent in Indonesia. Since 1994, Indonesia has a decree that all salt used for human, livestock, and industry must be iodized. However, despite the increased distribution of iodized salt, pockets with significantly higher prevalence of goiter still remain. This situation may be consequence of selenium (Se) deficiency. This study aimed to assess the Se level in the environment of goiter prevalent areas. Five hundred eleven school children participated in this study. Goiter was measured using both ultrasound and palpation. Ninety-nine eggs were collected from free-living chicken in 11 villages, and the Se contents of egg yolk and egg white were determined by neutron activation analysis. In the villages studied, Se concentration in egg yolk ranged from 0.15 to 1.52 Μg/g and in egg white from 0.18 to 2.97 Μg/g. The prevalence of goiter measured by palpation ranged from 18.4% to 70% and by ultrasound from 0% to 100%. Because of the inconsistency of goiter rate measured by palpation and ultrasonography, the question remains whether low availability of Se in the environment might be an additional contributing factor for goiter.     

阿克苏市5种常见绿化树种滞尘规律

绿化树种在截留沙尘、降低大气颗粒污染物浓度、改善城市生态环境等方面发挥着不可替代的作用。该文选取新疆南部典型绿洲城市——阿克苏市不同功能区的绿化树种, 用多重比较法对比分析了二球悬铃木(Platanus × acerifolia)、新疆杨(Populus alba var. pyramidalis)、圆冠榆(Ulmus densa)、天山梣(Fraxinus sogdiana)和垂柳(Salix babylonica) 5个树种叶片平均滞尘量随时间变化及不同高度叶片的滞尘能力, 探讨了阿克苏市主要绿化树种的滞尘规律, 得出以下结论: 不同绿化树种单位叶面积滞尘量差异显著, 差距在1.15-2.17倍之间, 绿化树种滞尘量随着时间延长而增加; 同一树种在城市不同功能区的滞尘能力不同: 工业区>交通枢纽区>居民区>清洁区; 不同高度的叶片, 其滞尘量在工业区和交通枢纽区差异显著: 高度1 m的叶片滞尘量>高度2 m的叶片滞尘量>高度4 m的叶片滞尘量。     

Preliminary assessment of protein associated with airborne particles in Mexico City

The protein associated with airborne particles was measured during 1991 as an indicator of airborne biological material in different outdoor urban environments. Fifty air samples were collected simultaneously at three sampling sites, located in the north, south and downtown Mexico City, using a PM10 high-volume sampler (particles<10 μm). The air filters were weighed and protein extracted using a phosphate buffer. Protein concentrations were determined by Lowry assay. The extracts were also analysed by SDS electrophoresis and IEF using a Phastsystem. High concentrations of airborne particles were recorded at the sampling sites with a geometric mean of 70.2 μg/m³ in the south (residential area), 95.5 μg/m³ in the center (urban-commercial area), and with the highest value of 108.9 μg/m³ in the north (urban-industrial area). No statistically significant difference (P>0.05) was observed among the protein concentrations from the sampling sites and the concentrations ranged from non-detectable to 2.54 μg/m³. However, the protein concentrations presented significant difference (P<0.05) with respect to rainy and dry seasons. The Spearman correlation coefficient between protein concentration and airborne particles concentration was statistically significant (r=0.50). The molecular weights (MW) and isoelectric points (pI) for the proteins present in some of the extracts were determined. The values ranged from approximately 8000 to 106 000 Da and the pI values from nearly 4.0 to 5.85. This is important because the major allergens from inhalants are mostly acidic proteins with molecular weights in the range of 20 000–40 000 Da.     

Determination of 1-hydroxypyrene in children urine using column-switching liquid chromatography and fluorescence detection

This study developed an acid hydrolysis method instead of using enzyme extraction, equipped with column-switching system for the pretreatment of samples, in the determination of 1-hydroxypyrene in the urine from children and pyrene in airborne particulates. We collected both types of samples from areas near a petrochemical industry and rural areas as reference. Samples were first treated with acid hydrolysis and followed by solvent extraction prior to being injected into the separation system for the determination with high performance liquid chromatography and fluorescence. A column-switching system was on-line with a C18 separation column to remove matrix interference and obtain a stable baseline of the chromatogram. The eluent used to separate the 1-hydroxypyrene was 60% (v/v) aqueous acetonitrile solution. A fluorescence detector was used to monitor 1-hydroxypyrene at lambdaex = 348 nm and lambdaem = 388 nm, and pyrene at lambdaex = 331 nm and lambdaem = 390 nm. Both calibration graphs were linear with very good correlation coefficients (r > 0.999) and the detection limits were ca. 2pg (5ng/l). Results showed that there was a significant association between 1-hydroxypyrene levels in urine specimens and pyrene levels in airborne particulate samples (r = 0.68, P < 0.05). The average levels of pyrene in the particulates (0.18 versus 0.09ng/m3) and of 1-hydroxypyrene in urine specimens (155.9 versus 110.2ng/g creatinine) were higher for the petrochemical area than for the rural area. This method is stable and sensitive for measuring polycyclic aromatic hydrocarbons in environmental samples.     

Indoor and outdoor airborne fungal propagule concentrations in Mexico City

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

Characterization of selenium status of inhabitants in the region Ústi nad orlici,czech republic by inaa of blood serum and hair and fluorimetric analysis of urine

Selenium is an essential trace element and its isufficient status may cause serious health complications for both individuals and the whole populations. To investigate the selenium status of the subpop-ulation in northeastern Bohemia represented by the region ústí nad Orlicí, 253 serum, 469 urine, and 31 hair samples from 470 randomly selected volunteers between 6 and 65 yr of age have been analyzed for selenium concentration. Serum and hair Se were detected by instrumental neutron activation analysis (means: 55 ±11 Μg Se/L sera, 0.268 ±0.040 Μg Se/g hair). Urine Se was measured by fluorimetry (12 ±5 Μg Se/L urine) with coanalyses of Lyphocheck urine, SRM Urine 2670, and Seronorm urine for quality control of the method. Results proved significant age-dependent differences, but gender differences were not significant. The frequency plot of serum Se proved maximal frequencies in adults between 55 and 70 Μg Se/L and in children in the range 45–55 Μg Se/L. The same plots of urine Se for both age groups showed maximal frequency in the limits 8–15 Μg Se/L. All indices used (Se in serum, urine, and hair) confirmed mild to severe selenium deficiency in the population of the region.     

Mutagenicity in Salmonella typhimurium mutants of serum extracts from airborne particulates

Airborne particulates collected from urban and non-urban air were extracted with calf serum or benzene, and their mutagenic potencies were evaluated in the Salmonella reversion assay. The serum extracts were mutagenic to strains TA98 and TA100 and contained both direct- and indirect-acting mutagens. Mutagenic activities for TA98 recovered from the particulates by serum or benzene extraction were much less in the serum extracts than in the benzene extracts. There was no significant difference in mutagenic potencies of the extracts between the urban and non-urban particulates, irrespective of the presence of S9 mix. The calculated mutagenic activities per m3 of air, however, were greater for urban air than for non-urban air, because of higher concentration of particulates in urban air than in non-urban air. Serum effectively reduced both direct and indirect mutagenic activities of the benzene extracts except for an insufficient reduction in direct mutagenicity at a high dose of benzene extracts. These findings suggest that serum could contribute greatly to decrease the mutagenicity of airborne particulates by mechanisms such as less efficient solubilization of mutagenic components and inactivation by protein binding. Biological availability of mutagens, therefore, should be considered for evaluation of actual mutagenic hazard by airborne particulates.     

Viability and potential for immigration of airborne bacteria from Africa that reach high mountain lakes in Europe

We have analysed the diversity of the bacteria, which grow after addition of concentrated airborne particles and desert dust in different microcosms combinations with water samples from oligotrophic alpine lakes. We used, on the one hand, airborne bacteria transported by an African dust plume and collected in a high mountain area in the central Pyrenees (Spain). On the other hand, we collected desert dust in Mauritania ( c . 3000 km distance, and a few days estimated airborne journey), a known source region for dust storms in West Africa, which originates many of the dust plumes landing on Europe. In all the dust-amended treatments we consistently observed bacterial growth of common phyla usually found in freshwater ecosystems, i.e. Alpha -, Beta - and Gammaproteobacteria , Actinobacteria , and a few Bacteroidetes , but with different composition based on lake water pretreatment and dust type. Overall, we tentatively split the bacterial community in (i) typical freshwater non-airborne bacteria, (ii) cosmopolitan long-distance airborne bacteria, (iii) non-freshwater low-distance airborne bacteria, (iv) non-freshwater long-distance airborne soil bacteria and (v) freshwater non-soil airborne bacteria. We identified viable long-distance airborne bacteria as immigrants in alpine lakes (e.g. Sphingomonas -like) but also viable putative airborne pathogens with the potential to grow in remote alpine areas ( Acinetobacter -like and Arthrobacter -like). Generation of atmospheric aerosols and remote dust deposition is a global process, largely enhanced by perturbations linked to the global change, and high mountain lakes are very convenient worldwide model systems for monitoring global-scale bacterial dispersion and pathogens entries in remote pristine environments.     

Detection of 3,6-dinitrobenzo[a]pyrene in airborne particulates

3,6-Dinitrobenzo[a]pyrene, a new mutagen, was detected in airborne particulates collected in Santiago (Chile). The quantity of the compound in the airborne particulates was very small, accounting for 0.01 micrograms/g of total particulates (0.002 ng/m3 of air) at the lowest concentration. It was found that 3,6-dinitrobenzo[a]pyrene is readily decomposed by UV irradiation at 312 nm. The decomposed product was identified as 3-nitrobenzo[a]pyrene-6-quinone by means of mass spectrometry and proton nuclear magnetic resonance analysis. The mutagenicity of 3,6-dinitrobenzo[a]pyrene was 137,000 revertants/nmole for Salmonella typhimurium strain TA98, less than that for strain TA98/1,8-DNP6, an acetyltransferase-deficient mutant, and more than that for strain YG1024, an acetyltransferase-rich mutant.     

Risk assessments of heavy metals in house dust from a typical industrial area in Central China

Heavy-metal pollution in house dust is of great potential hazard to human health, as people spend more than half of their time at home. To investigate heavy-metal pollution in a heavily air-polluted area of the Xi'an western industrial area, house dust was collected from relatively large residential quarters and <63 μm fraction of dust was measured for heavy metals. The results show that concentrations of Cr, Mn, Co, and V in the house dust are close to that in the local natural soil, whereas that of Ni, Cu, Zn, and Pb are often significantly elevated—mainly caused by intensively industrial activities in this area. Total ecological risks of these eight metals are moderate to considerable in most (69%) dust samples, while they are considerable to high in the others, occurring at the southwest of the study area. Health risk assessments reveal that exposure of these eight metals in the house dust has no risks to adults but has significant non-cancer risks to children, predominantly caused by dust ingestion. The results of this study are helpful for environmental management in industrial areas.     

Study of bioaerosols and site influence in the La Plata area (Argentina) using conventional and DNA (fingerprint) based methods

The present study approaches the characterization of seasonal samples of bioaerosols taken during 2005–2006 in rural, urban, industrial, coastal and residential sites within La Plata area, Buenos Aires, Argentina. Culturable airborne fungal and bacterial communities were collected on DG18 agar and R2 Agar plates respectively, using a single-stage SKC sampling device. Fungal genera were identified based on their micro- and macro-morphological characteristics. Bacterial populations were analyzed by denaturing gradient gel electrophoresis (DGGE) of PCR 16SrDNA bacterial amplification. Geometric mean concentration of bacteria and fungi ranged from 10 to 10³ CFU m⁻³ and were comparable with those from other reports. No differences were observed among sites for fungi and Cladosporium sp. was predominant, with 85.7% of total concentration counts; secondary genera that contributed were Alternaria (6.7%), Penicillium (1.8%), Aspergillus (1.3%), Epicoccum (1.0%) and the group of yeasts (1.9%). The dominance of Cladosporium in all sites suggests that the most abundant fungal aerosol was neither significantly affected nor primarily generated by any anthropogenic area source more than the natural ambience present in the La Plata area. With regard to bacteria, the results showed on several occasions differences in concentration among sites during sampling events, but these differences were not observed when the community structure was analyzed by means of DGGE. Bacterial DGGE banding profiles from all sites revealed the existence of a relatively diversified, culture-based airborne community. Construction of similarity dendrograms exposed a distribution of site samples in which replicates intra-site equalled those encountered among sites, rendering substantial inference of site distinction unfeasible.