Ocena narażenia na drobnoustroje w strefie oddziaływania składowiska odpadów komunalnych
AbstractSimilar to other municipal structures, landfills are important sources of hazardous emissions in the form of dusts, odorants and a number of different chemical and biological contaminants. In addition, several problems result from extremely high variability of harmful agent emissions, associated with diversity of disposed materials and meteorological conditions. Hence, it is difficult to obtain a conclusive picture of human exposure. All of this requires to detect accurately microbial emissions from these municipal structures and to assess their impact on environmental hygiene and human health. With respect to this problem, the dissertation presents some proposals of methods for assessing the exposure to airborne microorganisms within the immediate range of the landfill impact. The research presented in this dissertation aimed to: • obtain data on particle size distribution of airborne microorganisms both within the examined waste landfill and its surroundings; thus to determine the potential for depth penetration of the respiratory system by various fractions of bacterial and fungal aerosol particles (i.e. to evaluate which level of the respiratory system they can reach), • estimate the range of bioaerosol propagation as a result of air movement around the landfill followed by determination of seasonal dynamics of this process, • verify the suitability of the MTT cytotoxicity assay as an analytical tool complementary to classical methods of mycological research, • indicate accurately the source of microorganisms emitted from the landfill and to track transmission paths in its surroundings. Particular attention was paid to selection of bacterial and fungal environmental colonization markers both for the waste landfill and for its workers. The bioaerosol measurements were conducted according to the seasonal cycle (i.e. spring, summer, autumn and winter) at the sampling sites located within the municipal landfill in Tarnów. The bioaerosol samples were collected from each sampling site using a 6-stage Andersen’s impactor. Cytotoxicity was determined using mold strains of Aspergillus and Penicillium, which were isolated from air samples collected at the designated sites and from the disposed municipal waste. To find some markers for bacterial and fungal colonization of landfill environment and its workers from among the total microbial reservoir, the most frequently isolated strains were considered. These strains belonged to the most prevalent species to the environment studied (i.e. Staphylococcus aureus, S. lentus and S. xylosus for bacteria, and Aspergillus fumigatus, A. flavus and A. niger, for fungi). Two molecular methods based on PCR amplification of genomic DNA fragments were used in this stage of research, i.e. random amplification of polymorphic DNA (RAPD) and profiling of thermally denaturized DNA restriction fragments, PCR melting profile (PCR-MP). The molecular study covered the strains of aforementioned bacterial and fungal species. They were isolated from the following samples: air collected at the designated sampling sites, surface water, leachate, soil surrounded the functioning sector, the landfill functioning sector, surface of houseflies (Musca domestica) caught in the landfill area, bird feathers randomly collected within and around the active sector of the landfill, as well as from the landfill workers. The analysis of results allowed one to draw several conclusions. The results of studies conducted at the municipal landfill clearly show that the landfill is the major source of bacterial and fungal bioaerosol emission into the environment. The emission leads to an increase in both contamination within the direct impact zone and human health hazard. Seasonal variability is a significant factor affecting the bioaerosol concentrations within the municipal landfill. This means that predictions of the health effects resulting from the exposure to bioaerosols in the landfill should be based on the results of measurements conducted at different seasons. Monitoring of basic microclimatic parameters, i.e. temperature and relative humidity of air and wind velocity, is a prerequisite for properly conducted field research on the impact of municipal landfills. These parameter values are necessary for proper interpretation of microbiological analyses. Routinely performed operations on the waste landfill have a significant impact on bioaerosol concentrations. The highest exposure to bacterial and fungal aerosol is within the active sector of the landfill. Qualitative analysis of microorganisms isolated from the air within the landfill, and surroundings revealed the domination of Gram-positive cocci: Staphylococcus, Micrococcus and Kocuria, spore-forming rods of Bacillus and fungal genera of Alternaria, Aspergillus and Cladosporium. Among them, the presence of bacteria and fungi belonging to the second group of hazard was found. This fact indicates that the workers can be exposed to a direct contact with harmful biological agents. The exposure concerns mostly the functioning sector of the landfill during works related to unloading, distribution and compacting of wastes. Determination of particle size distribution of bioaerosol allows to obtain a detailed pattern of air contamination within the landfill. It enables to predict the range of human health exposure caused by microorganism transmission in the form of bioaerosols. For bacterial aerosol, the largest load of the particles in the human respiratory system may reach: throat, nasal and oral cavity, trachea, primary and terminal bronchi, and seasonally in winter, alveoli. However, fungi may reach oral and nasal cavity, pharynx, primary, secondary and terminal bronchi, and alveoli. This may result in health problems such as asthmatic or allergic reactions. The studies confirmed the practical and scientific usefulness of the cytotoxicity test for the mycotoxic hazard assessment in the environment of the municipal landfill. The applied MTT test proved to be a fast and effective method in the detection of mold strains that may synthesize mycotoxins. A. fumigates that often colonizes municipal waste poses the greatest mycotoxic threat at the examined waste landfill. The results from the study revealed that the isolated strains were more cytotoxic than other species of molds. The analysis of differentiation among Staphylococcus strains showed that the municipal landfill is a habitat that significantly stimulates the bacterial diversity. For particular Staphylococcus species, high genetic diversity is characteristic for strains isolated from different sites of the landfill, in comparison with the central sector and waste. Genotyping analysis confirmed that wastes are not the source of S. aureus for the landfill workers because the landfill is a habitat for the genetically specific saprophytic strain. The environmental strains are significantly different from those isolated from humans. The results of molecular analyses indicate that both genotypic methods differentiated strain genotypes of three Aspergillus species, belonging to the indigenous microflora of the area where the landfill is located, from the genotypes of strains specific to or originating from the waste. The wastes collected at the landfill contain fungal strains distinctly different genetically from the native strains. The genotypic analyses clearly indicate that insects and birds act as vectors transferring strains of Staphylococcus and Aspergillus species, inhabiting the waste, to the environment. The results of molecular analyses indicate that the methods used during this study, based on the analysis of genetic material, may be applied to examine the range of invironmental and human colonization with microorganisms in the impact zone of municipal waste landfill. It was established that these methods allow not only to select a bacterial or fungal marker of colonization of the landfill surroundings but also enable to determine the source of microorganisms. Furthermore, they permit to track the transmission routes in the landfill surroundings, as well as to forecast the range of human health exposure.
|Other language title versions||Exposure assessment to microorganisms in the impact zone of a municipal waste landfill|
|Publisher name (outside publisher list)||Wydawnictwo Uniwersytetu Rolniczego w Krakowie|
|Publishing place (Publisher address)||Kraków|
|Book series /Journal (in case of Journal special issue)||Zeszyty Naukowe Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Rozprawy, ISSN 1899-3486, (0 pkt)|
|Publication size in sheets||8|
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