Potential pathogenic bacteria in metalworking fluids and aerosols from a machining facility

Abstract

The metalworking and machining industry utilizes recirculating metalworking fluids for integral aspects of the fabrication process. Despite the use of biocides, these fluids sustain substantial biological growth. Subsequently, the high-shear forces incurred during metalworking processing aerosolize bacterial cells and may cause dermatologic and respiratory effects in exposed workers. We quantified and identified the bacterial load for metalworking fluid and aerosol samples of a machining facility in the US Midwest during two seasons. To investigate the presence of potentially pathogenic bacteria in fluid and air, we performed 16S rRNA gene surveys. The concentration of total bacterial cells (including culturable and nonculturable cells) was relatively constant throughout the study, averaging 5.1 × 10⁸ cells mL⁻¹ in the fluids and 4.8 × 10⁵ cells m⁻³ in the aerosols. We observed bacteria of potential epidemiologic significance from several different bacterial phyla in both fluids and aerosols. Most notably, Alcaligenes faecalis was identified through both direct sequencing and culturing in every sample collected. Elucidating the bacterial community with gene surveys showed that metalworking fluids were the source of the aerosolized bacteria in this facility.

Biological and chemical hazards in water-mix metalworking fluids and mists

“…Nevertheless, whilst the presence of Pseudomonads is not considered a risk factor with regards to respiratory illness as viable bacterial cells (Perkins and Angenent, 2010).…”

“…Some of which may be pathogenic to humans (Perkins and Angenent, 2010 (Perkins and Angenent, 2010;Schwarz et al, 2015).…”

“…These include; chemicals such boron (MHDS95/3), or biological contaminants such as bacteria, fungi (Perkins and Angenent, 2010) and endotoxins (Thorne et al, 2006). However, it is now understood sampling biological components requires much more consideration when correlating results to MWF sump samples.…”

“…Nevertheless, air sampling using impingement methods has been shown to reduce the impact on the viability of organisms within the literature (Terzieva et al, 1996). The research carried out by Perkins and Angenent (2010) employed the use of the SKC liquid impinger and successfully identified bacteria present within MWF samples and air samples. The bacteria that they detected in both MWF and air samples consisted of Wautersiella falsenii and Pseudochrobactrum asaccharolyticum.…”

“…Microorganisms such as bacteria, opportunistic mycobacteria and fungi have all been detected within MWF Lodders and Kampfer, 2012). In addition, some of these microorganisms are thought to express antigens causative in the pathogenesis of OHP and OA (Perkins and Angenent, 2010). A large number of studies investigating the cause of respiratory allergy in machinists have relied on traditional culture based methods for quantifying bacteria present in MWF (Khan and Yadav, 2004;Saha et al, 2011).…”