Purpose The objective of this study was to assess exposure to anaerobic bacteria released into air from sewage and sludge at workplaces from a wastewater treatment plant (WWTP). Methods Samples of both sewage and sludge were collected at six sampling points and bioaerosol samples were additionally collected (with the use of a 6-stage Andersen impactor) at ten workplaces covering different stages of the technological process. Qualitative identification of all isolated strains was performed using the biochemical API 20A test. Additionally, the determination of Clostridium pathogens was carried out using 16S rRNA gene sequence analysis. Results The average concentration of anaerobic bacteria in the sewage samples was 5.49 × 10⁴ CFU/mL (GSD = 85.4) and in sludge—1.42 × 10⁶ CFU/g (GSD = 5.1). In turn, the average airborne bacterial concentration was at the level of 50 CFU/m³ (GSD = 5.83) and the highest bacterial contamination (4.06 × 10³ CFU/m³) was found in winter at the bar screens. In total, 16 bacterial species were determined, from which the predominant strains belonged to Actinomyces, Bifidobacterium, Clostridium, Propionibacterium and Peptostreptococcus genera. The analysis revealed that mechanical treatment processes were responsible for a substantial emission of anaerobic bacteria into the air. In both the sewage and air samples, Clostridium perfringens pathogen was identified. Conclusions Anaerobic bacteria were widely present both in the sewage and in the air at workplaces from the WWTP, especially when the technological process was performed in closed spaces. Anaerobic bacteria formed small aggregates with both wastewater droplets and dust particles of sewage sludge origin and as such may be responsible for adverse health outcomes in exposed workers.

Exposure to flour dust can be found in the food industry and animal feed production. It may result in various adverse health outcomes from conjunctivitis to baker's asthma. In this paper, flour dust exposure in the above-mentioned occupational environments is characterized and its health effects are discussed. A peer-reviewed literature search was carried out and all available published materials were included if they provided information on the above-mentioned elements. The hitherto conducted studies show that different components of flour dust like enzymes, proteins and baker's additives can cause both non-allergic and allergic reactions among exposed workers. Moreover, the problem of exposure to cereal allergens present in flour dust can also be a concern for bakers’ family members. Appreciating the importance of all these issues, the exposure assessment methods, hygienic standards and preventive measures are also addressed in this paper.

This study aimed to qualitatively and quantitatively assess the prevalence of the most common respiratory and gastrointestinal viruses in the air, surface swab, and influent/effluent samples collected in wastewater treatment plants (WWTPs). Application of qPCR/RT-qPCR (quantitative polymerase chain reaction/reverse-transcription quantitative polymerase chain reaction) assays combined with PMA (propidium monoazide) dye pretreatment allowed detecting the potentially infectious and disintegrated viral particles in collected samples. In the air at workplaces in WWTPs, the most frequent isolation with the highest concentrations (reaching up to 10³ gc/m³ of potentially infectious intact viral particles) were observed in case of adenoviruses (AdVs) and rotaviruses (RoVs), followed by noroviruses (NoVs). Viruses were significantly more often detected in the air samples collected with Coriolis μ impinger, than with MAS-100NT impactor. The temperature negatively (Spearman correlation: –1 < R < 0; p < 0.05), while RH (relative humidity) positively (0 < R < 1; p < 0.05) affected airborne concentrations of potentially infectious viral particles. In turn, the predominant viruses on studied surfaces were RoVs and noroviruses GII (NoV GII) with concentrations of potentially infectious virions up to 10⁴ gc/100 cm². In the cases of SARS-CoV-2 and presumptive SARS-CoV-2 or other coronaviruses, their concentrations reached up to 10³ gc/100 cm². The contamination level of steel surfaces in WWTPs was similar to this on plastic ones. This study revealed that the qualitative and quantitative characteristics of respiratory and gastrointestinal viruses at workplaces in WWTPs is important for proper exposure assessment and needs to be included in risk management in occupational environment with high abundance of microbial pollutants derived from wastewater.

An automobile air-conditioning (AC) system can be a source of microbiological contamination in a driver’s car. The aim of this study was to assess the level of microbial contamination before and after servicing of the automobile AC system, based on qualitative and quantitative analyses of bacteria and fungi isolated from the air, and to check the efficiency of different AC system cleaning methods in the removal of microbial contaminants. The study was carried out in 35 randomly selected cars, equipped with AC systems. In each car tested, viable bioaerosol samples were taken using a single-stage MAS impactor before and after servicing the AC systems. Four methods were used to disinfect the air-conditioning installations in the vehicles examined: ozonisation, application of chemical disinfectant using ultrasounds, manual application of chemical disinfectant foam and simultaneous ozonisation and application of chemical disinfectant foam. The bacterial and fungal concentrations in air samples before AC servicing in cars were between 7.5 × 10¹ cfu/m³ and 2.0 × 10³ cfu/m³ and 4.0 × 10¹ cfu/m³ and 5.0 × 10² cfu/m³, respectively. Regardless of the disinfection method, after the AC service, a decrease in microbial concentrations was observed. The highest disinfection efficiency was observed for two methods: ozonisation combined with manual application of the chemical disinfectant into the air-conditioning system and spraying of the chemical disinfectant using ultrasounds. On the basis of the results obtained, it can be concluded that air-conditioning systems in cars should be regularly disinfected to eliminate microbiological contaminants, which may be the cause of adverse health effects on humans.

Objective: The aim of this study was to assess microbial contamination of the air and surfaces at workplaces in commercial (CD) and traditional (TD) dairies. Material and methods: Bioaerosol (impactor) and surface (swab) samples were collected in CD and in TD. Bacterial and fungal...