Concentration Of Airborne Microbes Research Articles

Calibration for number size distribution of bacterial cells measured with traditional size-segregated aerosol samplers

Andersen samplers were invented to study the health effects of airborne particles according to the particle size and have been carefully validated and widely used. Recently, it turned to be necessary to quantify the cell concentration of airborne microbes with the progress in understanding the roles that bioaerosols play in the atmosphere. To collect enough particles on filters, collection time was frequently extended from minutes to hours and even days. However, prolonged impaction time may cause considerable microbes trapped in upper stage filters to drop to subsequent stage filters, leading to supposed uncertainties in the microbial size distribution. This study investigated the uncertainties in bacterial cell number size distribution measured with 8-stage Andersen samplers at a flow rate of 28.3 L min−1 (50% cutoff diameters: >11, 7.0, 4.7, 3.3, 2.1, 1.1, 0.65 and 0.43 μm). Results showed that the concentration of bacterial cells in the size range of >4.7 μm could be underestimated by 40–50% as the concentration in the size range smaller than 3.3 μm was overestimated when the sample collection time was more than 6 h. Sample collection time should be less than 20 min to suppress the uncertainty below 10%, and 42 min to be smaller than 20%. Based on identified exponential inverse relation between the dropping rate from each stage and sample collection time, a scheme is proposed to calibrate the counting results of Andersen sampler samples to obtain the number size distribution of airborne bacterial cells with examples.

Characteristics and Influencing Factors of the Microbial Concentration and Activity in Atmospheric Aerosols over the South China Sea

Oceans are important sources of microbes in atmospheric aerosols; however, information about the characteristics of airborne microbes and their influencing factors over oceans is lacking. Here we report the characteristics of the microbial abundance and activity in aerosols sampled near the sea surface over the South China Sea (SCS) from May to June 2016. The airborne microbial concentration range in the aerosols was 1.68×105 to 4.84×105 cells m−3 over the SCS, reflecting an average decrease of 40%–54% over the SCS compared with that in the samples from the coastal region of Qingdao. About 63%–76% of the airborne microbes occurred in coarse particles (> 2.1 µm), with a variable size distribution over the SCS. The microbial activity range in aerosols, measured by the fluorescein diacetate (FDA) hydrolysis method, was 2.09–11.97 ng m−3 h−1 sodium fluorescein (SF) over the SCS, which was 15%–79% lower than that over the coastal region. These values reflected a different spatial distribution over the SCS from that of the microbial concentration. Except for certain samples, all samples had 68% of the microbial activity occurring in coarse particles. Correlation analysis showed that the microbial abundance and activity were positively correlated with the aerosol, organic carbon (OC), and water-soluble organic carbon (WSOC) concentrations, indicating that the airborne microbes may be related to the reactions of certain water-soluble organic chemicals in the atmosphere. Moreover, the concentrations of airborne microbes were significantly negatively correlated with the horizontal offshore distance. The microbial concentration and activity were significantly correlated with wind speed.

Ambient concentration of airborne microbes and endotoxins in rural households of southern India

Investigation of microbial communities in the indoor environment is critically important as majority of human life is spent indoors. Airborne microbial flora and their pyrogenic substances can impact human health. They have so far been insufficiently characterized. Here, we quantify bioaerosol concentration and diversity in both indoor and outdoor air of rural households in South India and statistically determine the significant predictor variables influencing them. The median concentration of bacterial and fungal aerosols in indoor air (n = 36 households) was 1031 colony forming units (CFU) m−3 and 580 CFU m−3, respectively, and in outdoor air was 742 CFU m−3 and 680 CFU m−3, respectively. Bacterial species were comprised of the four major phyla Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes, and fungal species of Ascomycota, Basidiomycota, and Zygomycota, in both indoor and outdoor air. Multivariable linear regression revealed that outdoor bacterial concentration, the number of house inhabitants, indoor temperature, age of the homes and use of biomass (cow dung or firewood) as cooking fuel were significant predictor variables influencing concentrations of bacteria in the indoor air. The significant predictor variables influencing indoor endotoxin concentrations were indoor bacterial concentration, indoor meteorology (temperature and relative humidity), and use of biomass as cooking fuel. Outdoor fungal concentration was the significant predictor variable influencing fungal concentration in indoor air. Endotoxin concentrations in indoor air ranged from 1.23 to 20.7 EU m−3. Quantitative microbial risk assessment (QMRA) model revealed a probability of infection of resident women from B. anthracis to be 0.0009 to 0.010.

Source identification of airborne bacteria in the mountainous area and the urban areas

Abstract Airborne microbes are an abundant component of the atmospheric aerosol, which has important influences on atmospheric conditions and public health. However, their possible sources have not been well-studied. To identify the sources of airborne bacteria, airborne PM2.5, PM10 samples and microorganism samples from surface-soil and leaves were collected at three different sampling sites involved in the mountainous area and urban areas in Xi'an, China in summer and autumn. The samples were then analyzed by fluorescence staining and high-throughput sequencing to explore the relationship in bacterial community structures between ambient air samples and possible sources. Results show that the concentrations of airborne microbes differed among sites and between seasons. The airborne bacterial community structures also varied with seasons and sites, with seasonal differences being greater than spatial ones. In both seasons, leaf-surface represented the main local source of airborne bacteria. At the mountainous area, bacteria from surface-soil and leaf-surface contributed the most to the airborne microbial community; at both mountainous and urban areas, this contribution was more pronounced in autumn. Furthermore, back trajectories arriving at the three sampling sites showed that the airborne bacteria may come from other regions by long-distance airflow. The results of this study provide a better understanding about the sources of ambient bacteria.

Influence of Dust Events on the Concentration and Size Distribution of Microorganisms in Bioaerosols

In order to study the influence of dust events on the airborne microbes in atmospheric bioaerosols, bioaerosol samples were continuously collected from March to April 2015 during two dust events using size-fractionated bioaerosol samplers in Lanzhou and Qingdao. The concentration of airborne microbes were measured using an epifluorescence microscope after staining with DAPI (4',6-diamidino-2-phenylindole). The results showed that the concentration of airborne microbes increased significantly during the period of dust (P<0.05). The average concentrations of airborne microbes on sunny days were 5.61×105 cells·m-3 and 2.08×105 cells·m-3 in Lanzhou and Qingdao, respectively, whereas the mean concentrations on dusty days were 14.8 times and 6.42 times those on sunny days, respectively. The concentration of airborne microbes presented a bimodal size distribution on sunny days in Lanzhou and Qingdao, with a peak at>7.0 μm and the lowest values ranging from 4.7 μm to 7.0 μm. However, the second peak appeared at 3.3-4.7 μm and 1.1-2.1 μm in Lanzhou and Qingdao, respectively. The size distribution of airborne microbes changed during the dust period. The size distribution of microbes still presented a bimodal distribution in Lanzhou; however, one peak shifted from>7.0 μm to 1.1-2.1 μm. The size distribution in Qingdao changed from a bimodal distribution to a skewed distribution with the predominant fraction in coarse mode. The background values of microbial load in PM10 before the dust were 2224 cells·μg-1 and 1550 cells·μg-1 in Lanzhou and Qingdao, respectively, and the highest value of such increased significantly to 26442 cells·μg-1 and 10250 cells·μg-1 during the dust events, respectively. This demonstrated that the high concentration of microbes in the dust events resulted not only from increased atmospheric particles but also from dust source and transportation path along with long-range transported dust particles.

A study of the energy consumption and airborne microbe concentration in the Sapporo underground walkway, in a cold region of Japan

The present study sought to evaluate the energy consumption, indoor air quality and concentration of airborne bacteria and fungi in the Sapporo underground walkway, which is in a cold region of Japan. The energy consumption, temperature, relative humidity, and carbon dioxide concentrations of the underground walkway were investigated for 4 years from its opening in 2011 (until 2014). The temperature, relative humidity, and carbon dioxide concentrations were automatically detected using sensors and data from Sapporo city hall. To evaluate the microbial contamination in the ventilation system and indoors, the concentrations of airborne bacteria and fungi were measured on 2 days (a weekday and a weekend day) during opening hours in both summer and winter. The concentration of airborne microbes in the supply air, indoor air, and outside air was compared. Species of airborne bacteria were identified using 16S rDNA sequence analysis. The energy use intensities were decreased in 2013, when the walkway temperature was changed during both winter and summer. The carbon dioxide concentration in the walkway was maintained below 1000 ppm. The number of airborne bacteria and fungi in the supply air from the ceiling diffuser was lower than those in the outdoor and indoor air. These results indicate that both energy consumption and indoor air quality were maintained in the walkway throughout the 4-year period. This study could be helpful for developing the related standards for indoor air quality and for developing control strategies to properly operate air conditioning and ventilation systems in underground spaces.

Aerosolized Microbes from Organic Rich Materials: Case Study of Bat Guano from Caves in Romania

Cave air, bat guano, and swabs of bat fur from caves with bat guano in Romania were analyzed by using RIDAHCOUNT cultivation plates and standard selective media for Staphylococcus and Streptococcus. The samples of guano varied in concentration of cultivable chemoheterotrophic bacteria (max. 1.9310 10 CFU/g), coliforms (max. 2.2310 8 CFU/g), Escherichia coli (max. 1.0310 8 CFU/g), and yeasts and molds (max. 1.7310 7 CFU/g). The gravity-settling principle was applied to sample airborne microorganisms, and a new method was developed for evaluation of aerosolization potential. In cave air, the concentration of total bacteria was higher than yeast and molds. In addition to coliforms, enterobacteria, E. coli, and unidentified cultivable bacteria in the air samples, we also identified Chryseomonas luteola, Klebsiella pneumoniae, Micrococcus, Salmonella, Staphylococcus, and Streptococcus. In the experiment that provoked microbial aerosolization from guano, 3.35% of total cultivable fungi were aerosolized, up to 0.10% of bacteria, and 0.00% of E. coli. The concentration of Staphylococcus in the air exceeded counts of Streptococcus. The highest concentrations of airborne microorganisms were on the ground level. Using cultivation plates as a robust method we demonstrated that the relative proportion of microbial subgroups in the air remained constant in different seasons, with lower concentrations of airborne microbiota in the autumn. Caves as simplified natural systems demonstrated complex relationships between atmospheric parameters and microorganisms. Bats introduce into caves varying, but not negligible, concentrations of microbes on their fur. Caves with guano had relative high concentration of airborne microbes that may represent a biohazard for animals and humans.

Immune Indexes of Larks from Desert and Temperate Regions Show Weak Associations with Life History but Stronger Links to Environmental Variation in Microbial Abundance

Immune defense may vary as a result of trade-offs with other life-history traits or in parallel with variation in antigen levels in the environment. We studied lark species (Alaudidae) in the Arabian Desert and temperate Netherlands to test opposing predictions from these two hypotheses. Based on their slower pace of life, the trade-off hypothesis predicts relatively stronger immune defenses in desert larks compared with temperate larks. However, as predicted by the antigen exposure hypothesis, reduced microbial abundances in deserts should result in desert-living larks having relatively weaker immune defenses. We quantified host-independent and host-dependent microbial abundances of culturable microbes in ambient air and from the surfaces of birds. We measured components of immunity by quantifying concentrations of the acute-phase protein haptoglobin, natural antibody-mediated agglutination titers, complement-mediated lysis titers, and the microbicidal ability of whole blood. Desert-living larks were exposed to significantly lower concentrations of airborne microbes than temperate larks, and densities of some bird-associated microbes were also lower in desert species. Haptoglobin concentrations and lysis titers were also significantly lower in desert-living larks, but other immune indexes did not differ. Thus, contrary to the trade-off hypothesis, we found little evidence that a slow pace of life predicted increased immunological investment. In contrast, and in support of the antigen exposure hypothesis, associations between microbial exposure and some immune indexes were apparent. Measures of antigen exposure, including assessment of host-independent and host-dependent microbial assemblages, can provide novel insights into the mechanisms underlying immunological variation.

Comparative microbial sampling from eutrophic caves in Slovenia and Slovakia using RIDA ®COUNT test kits

RIDA®COUNT test plates were used as an easy-to-handle and rapid indicator of microbial counts in karst ecosystems of several caves in Slovakia and Slovenia. All of the caves had a high organic input from water streams, tourists, roosting bat colonies or terrestrial surroundings. We sampled swabs, water and air samples to test robustness and universality of the RIDA®COUNT test kit (R-Biopharm AG, Germany, http://www.r-biopharm.com/) for quantification of total bacteria, coliforms, yeast and mold. Using data from swabs (colony-forming units CFU per cm 2 ) we proposed a scale for description of biocontamination level or superficial microbial load of cave niches. Based on this scale, surfaces of Ardovska Cave, Drienovska Cave and Stara Brzotinska Cave (Slovakia) were moderately colonized by microbes, with total microbial counts (sum of total bacterial count and total yeast and molds count) in the range of 1,001-10,000 CFU/100 cm 2 , while some surfaces from the show cave Postojna Cave (Slovenia) can be considered highly colonized by microbes (total microbial counts ≥ 10,001 CFU/100 cm 2 ). Ardovska Cave also had a high concentration of airborne microbes, which can be explained by restricted air circulation and regular bat activity. The ratio of coliform to total counts of bacteria in the 9 km of underground Pivka River flow in Postojna Cave dropped approximately 4-fold from the entrance, indicating the high anthropogenic pollution in the most exposed site in the show cave. The RIDA®COUNT test kit was proven to be applicable for regular monitoring of eutrophication and human influence in eutrophic karst caves.

THE PROGNOSIS OF BRONCHIAL ASTHMA FROM ADOLESCENCE TO ADULTHOOD

ISEE-174 Introduction: A rising trend in asthma prevalence and morbidity has been evident throughout the world, and reports on the prognosis of asthma have presented varied outcomes from western countries. Yet, risk factors attributable to the nature and prognosis of bronchial asthma, especially from adolescence to adulthood, have not been under thorough investigation for this part of the world where environmental and genetic influence is of great importance. Methods: From a region-wide questionnaire survey, 704 middle-school students at Chiayi County were identified in 1995 as having had reported wheeze with difficult breathing in the past 12 months. Seven years later in 2002, 369 of them, 211 males and 158 females with mean age of 20 years, were successfully retrieved for questionnaire interviews and physical examinations. Results: There was no statistical significance in gender (p=0.61), mean age (p=0.28), and percentage of physician-diagnosed asthmatic cases (p=0.5) between this sub-group of the follow-up study, and the original population of 704. Among them, 119 subjects (32%) were considered to have asthma persistence into adulthood, and 250 subjects (68%) had not experienced any asthmatic symptoms for at least one year. A majority (60%) of those with inactive asthma were symptom-free for more than 5 years. In addition, 50 active asthmatics and 60 inactive asthmatics were randomly sampled from these 369 subjects, to attend hospital visits for detailed questionnaire interviews, physical examinations, pulmonary function tests, and Immunoglobulin E checks. The presence of mould growth in the residential interiors (OR=5.0, p=0.04), familial history of asthma (OR=2.9, p=0.003), and concomitant allergic rhinitis (OR=3.4, p=0.02) were significantly associated with persistence of asthma into adulthood. Discussion: Our results suggest that environmental and genetic factors both play a vital role on the prognosis of middle-school aged asthmatics. The contribution of indoor mould growth to the persistence of adolescent asthma into adulthood is particularly meaningful for an environment, such as Taiwan, where high humidity and concentrations of airborne microbes have been observed. A future endeavour may focus on the promotion of environmental hygiene along with proper clinical management, for the treatment and control of asthmatics in similar surroundings.

Occupational hygiene in a Finnish drum composting plant

Bioaerosols (microbes, dust and endotoxins) and volatile organic compounds (VOCs) were determined in the working air of a drum composting plant treating source-separated catering waste. Different composting activities at the Oulu drum composting plant take place in their own units separated by modular design and constructions. Important implication of this is that the control room is a relatively clean working environment and the risk of exposure to harmful factors is low. However, the number of viable airborne microbes was high both in the biowaste receiving hall and in the drum composting hall. The concentration (geometric average) of total microbes was 21.8 million pcs/m 3 in the biowaste receiving hall, 13.9 million pcs/m 3 in the drum composting hall, and just 1.4 million pcs/m 3 in the control room. Endotoxin concentrations were high in the biowaste receiving hall and in the drum composting hall. The average (arithmetic) endotoxin concentration was over the threshold value of 200 EU/m 3 in both measurement locations. In all working areas, the average (arithmetic) dust concentrations were in a low range of 0.6–0.7 mg/m 3, being below the Finnish threshold value of 5 mg/m 3. In the receiving hall and drum composting hall, the concentrations of airborne microbes and endotoxins may rise to levels hazardous to health during prolonged exposure. It is advisable to use a respirator mask (class P3) in these areas. Detected volatile organic compounds were typical compounds of composting plants: carboxylic acids and their esters, alcohols, ketones, aldehydes, and terpenes. Concentrations of VOCs were much lower than the Finnish threshold limit values (Finnish TLVs), many of the quantified compounds exceeded their threshold odour concentrations (TOCs). Primary health effects due VOCs were not presumable at these concentrations but unpleasant odours may cause secondary symptoms such as nausea and hypersensitivity reactions. This situation is typical of composting plants where the workers are exposed to dozens of VOCs simultaneously. The odour units (OU/m 3) were measured using olfactometer. The numbers were 23,000 OU/m 3 at the output end of the composting drum and 6300 OU/m 3 in the exhaust pipe. Inside the composting hall, the number of odour units was 500 and 560 OU/m 3.

Exposure to microbes, endotoxins and total dust in cigarette and cigar manufacturing: an evaluation of health hazards

The concentrations of airborne microbes, endotoxins and total dust were measured in one cigar and two cigarette factories in order to evaluate the risk of respiratory symptoms. The role of humidifiers as a source of microbes was investigated. Air samples for the analyses were collected near workers' breathing zones during different phases of production. Gram-negative bacteria, mesophilic fungi, thermotolerant fungi and thermophilic actinomycetes, but not Aspergillus glaucus fungi, were found in higher concentrations in the cigar factory than in the cigarette factories. High microbe concentrations (10 4 –10 5 cfu m −3 ) occurred throughout the production line in the cigar factory. The highest dust and endotoxin concentrations were found in the wick-making department in the cigar factory (3.3 mg dust per m 3 and 38 ng endotoxin per m 3 ) and during the weighing or handling of raw tobacco in the cigarette factories (4.5 mg dust per m 3 and 106 ng endotoxin per m 3 ). The spray humidifiers in the cigar factory were a more important source of microbes than was raw tobacco. In the cigarette factories, steam humidifiers were used; the humidified air was free of microbes. The microbe concentrations in the tobacco factories were lower than in environments known to have caused allergic alveolitis.

Exposure to Microbes, Endotoxins and Total Dust in Cigarette and Cigar Manufacturing: an Evaluation of Health Hazards

The concentrations of airborne microbes, endotoxins and total dust were measured in one cigar and two cigarette factories in order to evaluate the risk of respiratory symptoms. The role of humidifiers as a source of microbes was investigated. Air samples for the analyses were collected near workers' breathing zones during different phases of production. Gram-negative bacteria, mesophilic fungi, thermotolerant fungi and thermophilic actinomycetes, but not Aspergillus glaucus fungi, were found in higher concentrations in the cigar factory than in the cigarette factories. High microbe concentrations (10(4)-10(5)cfu m(-3)) occurred throughout the production line in the cigar factory. The highest dust and endotoxin concentrations were found in the wick-making department in the cigar factory (3.3mg dust per m(3) and 38ng endotoxin per m(3)) and during the weighing or handling of raw tobacco in the cigarette factories (4.5 mg dust per m(3) and 106ng endotoxin per m(3)). The spray humidifiers in the cigar factory were a more important source of microbes than was raw tobacco. In the cigarette factories, steam humidifiers were used; the humidified air was free of microbes. The microbe concentrations in the tobacco factories were lower than in environments known to have caused allergic alveolitis.

Windrow composting of source separated kitchen biowastes in Finland

All households in the City of Jyväskylä have been required to source-separate their wastes since June 1996. The accumulation of kitchen biowaste was about 60 kg per resident in 1997, with an efficiency of more than 75%. The residents of almost 50% of the detached houses in the city opted for small-scale composting. Ensuing kitchen biowaste was surprisingly pure: the estimated content of non-compostable material was less than 0.1 % by weight. The biowastes were composted at the Mustankorkea waste station in open windrows. Adequate aeration of the windrows was guaranteed when the initial height of the windrow was less than 1.5 m and the blending ratio for biowaste and bulking agent was one tonne of biowaste to one cubic metre of wood chips. The temperature rose to 85°C in these windrows. Carbon concentration increased slightly during 64 weeks composting, whilst the hydrogen concentration decreased. The pH and the ash content also increased during composting. As measured by pathogenic microbes (Salmonella), the biowaste composts were hygienic. In summer, the concentration of airborne microbes was high during turning of the windrows, both in the composting field and in the cabin of the wheel loader. The concentration of endotoxin in the cabin exceeded all recommended limits.

Occupational hygiene in biowaste composting

Source-separated biowastes from the Helsinki Metropolitan Area have been composted in open air windrows at Ammas suo, the Helsinki regional landfill in Espoo (Finland). The most significant problem encountered in the early stages of the process has been the formation of rancid odor causing human discomfort. The offensive odor was mainly due to car boxylic acids. A total of 110 organic compounds were detected in volatile emissions from windrow composts with an integrated sensory and instrumental method. Occasionally the temperatures in the windrows exceeded 80°C. Bacterial measurements also revealed substantial populations of bacte ria at 75°C. The concentrations of airborne microbes and endotoxins were highest during the crushing of fresh biowaste and the turning of compost, and were relatively high in sum mer and when windrows were dry. The most common fungi in the air were Aspergillus and Penicillium. Dust concentrations were consistently low. The concentrations of microbes were never so high as to constitute an acute health hazard from the occasional exposure. Continuous exposure to such concen trations nevertheless increases the risk of illness. The time, neccessary for the compost to become hygienic improved from four months to four weeks during the project. Drum composting was also tested and was found to be an alternative approach to treating organic wastes. Emissions from the drum composting were low compared to open air composting.

Exposure to airborne microbes during the repair of moldy buildings.

Concentrations of airborne microbes, studied during the repair of seven moldy buildings, showed that concentrations of airborne fungi increased during the repair work. This was especially true during the demolition of moldy building materials, even though the total dust levels remained low. Concentrations of viable fungi sampled with a six-stage cascade impactor were 10(3) - > 1.9 x 10(5) cfu/m3, and the total concentrations of fungal propagules, as determined by the Camnea method (i.e., air filtration method with epifluorescence microscopic counting of acridine-stained organisms) showed 10(5)-10(6) counts/m3 during the demolition. Penicillium was the main genus throughout. Concentrations of viable total bacteria also increased, but this change proved less noticeable than that of the fungi. However, rather high concentrations of viable actinomycetes up to 10(4) cfu/m3 were detected during the demolition. Results show that construction workers are exposed to high concentrations of microbes, perhaps causing health problems. Thus, personal protection of both the respiratory system and eyes is strongly recommended for workers as they repair moldy buildings. In addition, the repair room should be isolated from other areas to protect occupants or any other people present.

THE MICROBIOLOGIC EFFECT OF GAS FILTRATION

Air and expansile gases commonly are injected into the eye in both vitreoretinal surgery and anterior segment surgery. Although the halogenated gases are filtered routinely before injection, air often is not prepared in this manner. This study was designed to investigate the effect of filtration on the microbiology of gas mixtures. Two separate studies were conducted, one examining medical grade perfluoropropane gas (C3F8), and the other evaluating air collected from an ophthalmic operating room or emergency room. Aliquots of air or gas were collected through a 0.22-micron filter before and after filtration. The filter discs were cultured for bacterial and fungal organisms. Of 514 samples collected, none grew either bacterial or fungal organisms. There was no difference with regard to recovered microbes between filtered and unfiltered air or C3F8, nor was there a difference between operating room air and emergency room air. Positive controls using aerosolized microorganisms yielded heavy growth. Based on results obtained in this study and available information on the concentration of airborne microbes, the microbiologic effect of gas filtration is of little significance for volumes routinely injected in ophthalmic surgery.

Airborne Microbes and Endotoxins in the Work Environment of Two Sanitary Landfills in Finland

The Andersen sampler was used to study the occurrence of bacteria and fungi in the working air of two large, intensively used landfills in Finland. Endotoxins were also determined. The concentrations of airborne microbes were high in summer in warm windy weather. Mesophilic bacteria exceeded 105 colony-forming units (cfu)/m3 and mesophilic fungi 104 cfu/m3. In 67% of the samples, the concentrations of gram-negative bacteria exceeded 103/m3, which has been suggested to be the threshold limit value (TLV). The endotoxin levels were all below 0.1 μg/m3. A large part of the colony-forming particles were within the respirable size range, about 40% of the bacteria and about 80% of the fungi. The commonly isolated airborne bacteria were Pseudomonas, Enterobacter, and Bacillus spp. The landfill workers should try to work upwind. There are also grounds for using a mask and irrigating the refuse terrace with leachate in dry weather. It is suggested that the traffic on the refuse terrace be decreased by arranging for the private cars to be emptied in the reception area.

Airborne micro-organisms and prevalence of byssinotic symptoms in cotton mills.

The concentration of airborne microbes, their endotoxins and the prevalence of byssinotic symptoms among workers were measured in the cardrooms of seven cotton spinning, a wool spinning and two cotton waste mills and in a dusty workroom of a group of five willowing mills, a tea-packing plant and a pipe tobacco factory. The concentration of microbes cultured on endoagar plates were found to correlate with byssinosis prevalence (r greater than 0.95, P less than 0.001). The concentration of nutrient agar microbes correlated with prevalence less well (r greater than 0.77, P less than 0.01) and that of fungi and endotoxins not at all.

Rising fertilizer tonnage

Bioaerosols (microbes, dust and endotoxins) and volatile organic compounds (VOCs) were determined in the working air of a drum composting plant treating source-separated catering waste. Different composting activities at the Oulu drum composting plant take place in their own units separated by modular design and constructions. Important implication of this is that the control room is a relatively clean working environment and the risk of exposure to harmful factors is low. However, the number of viable airborne microbes was high both in the biowaste receiving hall and in the drum composting hall. The concentration (geometric average) of total microbes was 21.8 million pcs/m3 in the biowaste receiving hall, 13.9 million pcs/m3 in the drum composting hall, and just 1.4 million pcs/m3 in the control room. Endotoxin concentrations were high in the biowaste receiving hall and in the drum composting hall. The average (arithmetic) endotoxin concentration was over the threshold value of 200 EU/m3 in both measurement locations. In all working areas, the average (arithmetic) dust concentrations were in a low range of 0.6–0.7 mg/m3, being below the Finnish threshold value of 5 mg/m3. In the receiving hall and drum composting hall, the concentrations of airborne microbes and endotoxins may rise to levels hazardous to health during prolonged exposure. It is advisable to use a respirator mask (class P3) in these areas.Detected volatile organic compounds were typical compounds of composting plants: carboxylic acids and their esters, alcohols, ketones, aldehydes, and terpenes. Concentrations of VOCs were much lower than the Finnish threshold limit values (Finnish TLVs), many of the quantified compounds exceeded their threshold odour concentrations (TOCs). Primary health effects due VOCs were not presumable at these concentrations but unpleasant odours may cause secondary symptoms such as nausea and hypersensitivity reactions. This situation is typical of composting plants where the workers are exposed to dozens of VOCs simultaneously. The odour units (OU/m3) were measured using olfactometer. The numbers were 23,000 OU/m3 at the output end of the composting drum and 6300 OU/m3 in the exhaust pipe. Inside the composting hall, the number of odour units was 500 and 560 OU/m3.