Effectiveness of engineering interventions in decreasing worker exposure to metalworking fluid aerosols

The influence of ventilation modes on oil mist particles diffusion in a machining workshop

Mechanical processing and operations are widely involved in modern industry. Large amount of oil mist is tended to be produced and will diffuse in the processing workshop when metalworking fluids are applied on the high temperature workpiece. The ventilation modes and air distributions can influence the air pollutants dilution in machining workshops. Therefore, this paper presents both experimental investigation and simulation study on the oil mist particles diffusion under different ventilation modes. The results identified PM2.5 as the primary component among different oil mist particles generated during a typical machining process. The distribution of oil mist particles in a full-scale machining workshop laboratory was investigated under two ventilation modes: high-sidewall nozzle air supply and low-sidewall air supply. Results revealed obvious influences of both air supply modes on the distribution of oil mist particles. Under the high-sidewall-nozzle air supply mode, the airflow and the oil mist distribution in the workshop was relatively uniform; while the low-sidewall-vent air supply mode led to an uneven distribution of oil mist particles, and the maximum oil mist concentration appeared at the height of 3 m. Under both modes, the attempts to increase the airflow rate are not always successful. Compared with low-sidewall-vent air supply mode, the high-sidewall-nozzle air supply mode presents better performance in achieving lower overall particle concentration level. Overall, the results of this study give useful reference to improve the air quality of industrial plant by properly designing the ventilation mode of machining workshop.

Seasonal dynamics in bacterial communities of closed-cage broiler houses

The bacteria contained in air aerosols from poultry houses are closely connected to animal health and production. This study aimed to investigate the seasonal factors on microbial aerosol concentration, particle size and bacterial spectrum composition inside a closed-cage broiler house. Then, 16S rDNA sequencing technology was applied to analyze the characteristics of bacterial abundance and diversity. The results indicated that the concentration of bacterial aerosol in the broiler house varied significantly in different seasons, with a concentration range of 5.87–15.77 × 10³ CFU/m³, and the highest and lowest concentrations in the summer and winter, respectively. Microbiological analysis showed that the proportion of Gram-negative bacteria in autumn was significantly higher than that in summer (P < 0.05). In addition, the floral structure of potential pathogenic bacterial genera also differed by season. Escherichia-Shigella, Streptococcus, Acinetobacter, Pseudomonas were identified in the bacterial aerosols. Importantly, the relative abundance of Firmicutes in spring and autumn was much higher. In contrast, the relative abundance of Proteobacteria in spring and autumn was lower than that in summer and winter. Altogether, results revealed the effects of seasonal factors on the diversity and abundance of bacteria and the distribution characteristics of major opportunistic pathogens in the air of closed-cage broiler houses. These results will provide important information for exploring the potential risk of aerosols from poultry houses all four seasons.