Tuesday 19 July 2022

Human skin, movement and particles within the cleanroom


Cleanroom microbiologists have a concern with particle release and the main source of particle release is from personnel and a proportion of these particles will be microbial carrying. With cleanroom gowns the fabric must be tightly and reliably woven, typically retaining particles of 6 to 12 μm and greater and the highest efficiencies of 90% or higher     , although this varies by gown and whether it is single use or reusable. Assessments are made using bioaerosol chambers. In selecting gowns of the optimal pore size, there needs to be a trade-off between operator comfort and the particle retaining capabilities. There are also variables to take account of, for young people despise more microorganisms than older people and biological males disperse significantly more bacteria than biological females .


When we disperse skin particles, the median size of these have a minimum projected diameter of 20 μm, although 7–10% are less than 10 μm (these expand in the hydrated state) and a few are less than 5 μm. Where corneocytes are dispersed, these are far larger in size and would always be retained by the cleanroom gown.


It is for these reasons that we need to wear protective cleanroom gowns, with pores that can capture a high proportion of these pieces of skin detritus. Fabric and garment design is intended to act as a filter to minimise contaminants from the operator, such as skin flakes, hair and sneezing aerosols, from entering the cleanroom.


It is also based on these sizes that microbiologists are concerned with particles of an approximate diameter of 5 μm or larger as these may be indicative of skin fragments.


We also know that rates of skin shedding are increased through excessive movement, which is why movements within cleanrooms need to be slow and steady and why, in aseptic processing rooms, we ask personnel to stand still foremost of the time. Minimum movement is essential to contamination control.


Finally, we also know that many skin conditions, such as those leading to dry skin, increase the rate of shedding which is why skin conditions need to be reported ahead of each shift and judgement made about whether or not an individual can go into the cleanroom. There is an additional concern that dry skin alters the homeostasis of the microbiome, leading to a greater abundance and therefore shedding of organisms that are atypical, such as anaerobic and organisms that thrive in anoxic environments, including Cutibacterium acnes.

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)

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