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Fine-Dispersion Aerosols in the Environment of Human Life
Published in Katarzyna Majchrzycka, Nanoaerosols, Air Filtering and Respiratory Protection, 2020
Humans are one of the main sources of bioaerosols found indoors. The production of bioaerosol occurs by sneezing, coughing and physical activity. Humans are the main source of bacteria due to natural skin flora. Bathrooms are also a source of bioaerosols, due to high humidity, which is favorable for the development of mold fungi. Microbiological contamination can also come from construction and finishing materials such as wallpapers, insulation, fibrous materials and plasterboards. Fungi can develop in almost all materials that are sufficiently moist. Cellulose-based materials are particularly fungal-friendly (Sivasubramani et al. 2004). The presence of bioaerosols in indoor air is significantly influenced by heating, ventilation and air conditioning. Although mechanical ventilation systems are equipped with particle filters that remove up to 80% of aerosols from the air supplied from the outside, they are themselves a favorable area for the development of microorganisms. Air humidifiers, uncleaned ventilation ducts and particle filters that have not been replaced constitute an ideal place for the multiplication and spreading of fungi and bacteria (Bonetta et al. 2010).
The role of hygrodynamic resistance compared to biofilm formation in helping pathogenic bacteria dominate air-conditioning units recovered from odour problems
Published in Environmental Technology, 2023
Wing Lam Chan, Liwen Luo, Haoxiang Wu
Methylobacterium and Sphingomonas were two genera dominant in all ACUs, including the ones with and without odour problems before. Acinetobacter, a common skin flora, was found to be more abundant in ACUs with odour complaints previously (71% in 1c and 36% in 1d) than that without unpleasant odour (31% in 2b and 6% in 2a and 2c). Other than these three genera, Spirosoma also accounted for a significant portion in all ACUs, and Bradyrhizobium, another genus that had a significant abundance in some ACUs such as 1a, 2d & 2e, was shown to be more abundant in normal ACUs (13% and 9% in 2d and 2e, respectively) compared with the previously odorous ones (all lower than 5%). Similar to Bradyrhizobium, the relative abundance of Rhodococcus was higher in ACUs without odour complaints as well, accounting for approximately 11% in 2a and 4% in 2d but less than 1% in previously odourous ACUs; e.g. 1d and 1e. Other common skin bacteria, such as Staphylococcus, Propionibacterium, Corynebacterium and Micrococcus, were not detected in all ACUs sampled in this study.
The wash-in effect and its significance for mass casualty decontamination
Published in Journal of Toxicology and Environmental Health, Part B, 2022
Thomas James, Lydia Izon-Cooper, Samuel Collins, Haydn Cole, Tim Marczylo
The pH of skin is between 4 and 6, slightly acidic, and it is generally accepted that the acid mantle within the hydrolipid film coating the epidermis is the cause. Endogenous factors such as age and sebum as well as exogenous factors such as cleansing agents may also markedly affect the skin pH. Skin’s purpose is to neutralize alkaline compounds such as harsh surfactants, to allow optimal conditions for skin flora to thrive and to allow the SC to repair itself when damaged. The slightly acidic nature of the skin creates a gradient with the body’s generally neutral internal environment, and this gradient can be easily disrupted by adjusting the pH of the surface of the skin. It is thought that surfactants might alter the pH of the skin surface significantly, initiating a change in barrier function of the SC, and possibly leading to enhanced diffusion of certain chemicals. While this would not be a factor of the wash-in effect alone, it may contribute to a co-enhancement depending on the type of surfactant used.
Study of adherence kinetics of Escherichia coli on cotton knitted fabrics
Published in Indian Chemical Engineer, 2019
S. Bajpai, Vidushi Bajpai, Apurba Dey, Subrata Ghosh, M.K. Jha
In the literature, it was found that little information is available about the adherence of microbes on textile materials, the mechanism, kinetics and equilibrium of the process. This study therefore aimed towards the quantification of adhered cells, studying the kinetics and mechanisms of adherence. This work also aimed towards optimising the important parameters such as contact time, pH and temperature for adherence process on most commonly used textile fabric, i.e. cotton. Cotton was selected for the study as it is the most favoured fabric for manufacturing undergarments, infant wears and wound dressing. Escherichia coli was selected as it is one of most common microbes present in the environment, found in human skin flora, a common pathogen for wound and urinary tract infections [21]. The effect of three different pre-treatments (i.e. autoclaved alone; scoured + autoclaved; scoured + bleached + autoclaved) on cotton fabrics was also studied for the adherence. Kinetic data was analysed using the Lagergren equation, and the isotherm modelling of adherence process was done using the Langmuir and Freundlich models. To understand the mechanism of bacterial adherence, SEM and FTIR analysis was also done.