This article is part of a special feature on cleanrooms that was published in the December issue of PTE Digital, available
The current expectations for cleanroom operations are those found in the FDA's 2004 Guideline on Sterile Drug Products Manufactured by Aseptic Processing and EMA's Annex 1: Sterile Medicinal Products. These documents are reasonably well harmonised with each other with respect to environmental monitoring expectations, media
fill requirements and other areas, but they differ with respect to classification of the core aseptic processing environments,
where the EMA employs Grades A and B, and the FDA adheres to the more general ISO classification scheme. USP is about to formalise
a new chapter <1116> Microbial Evaluation of Clean Rooms and Other Controlled Environments that differs markedly in approach by eliminating numerical limits and suggesting incidence rates. USP cites analytical variability
and limit of detection with respect to numerical quantification, especially in the cleanest environments as a major part of
the reason for changing their approach.
Before validating a new cleanroom facility, I think it best to first consider the functionality of the facility and then define
the desired capabilities that it is intended to satisfy. It is essential to understand:
- the types of products and the expected volumes
- the processes necessary for their manufacture
- the equipment to be utilised in those processes, with special attention to the extent of automation and operator involvement
- the materials and components necessary for the manufacturing processes.
With this defined, one can progress through the design exercise in an orderly manner.
Environmental monitoring over-emphasised
With respect to environmental monitoring, the expectations of both the FDA and the EMA do not consider the realities of aseptic
processing and as a consequence, they overemphasise environmental monitoring to the point where they may actually be causing
more problems than they are endeavouring to prevent. There are several aspects that the regulators seem to ignore:
- Aseptic processing is not 'sterile' processing; those terms don't mean the same thing. The environments have never been, nor
do they need to be 'sterile'. We don't require a 'sterile' environment to make a 'sterile' product.
- Methods to precisely measure the microbial level in the air or on a surface do not exist. This is particularly true in the
- You cannot sample your way to 'sterility' in a processing environment. Even the most aggressive sampling schemes fall way
short and increase risk more than any insight gained.
- Sampling is an intervention and subject to adventitious contamination.
- There have always been (and always will be) viable but nonculturable species, we cannot detect everything, but then again
we shouldn't have to.
Expectations for perfection in performance may seem reasonable considering the label claim, but is quite unrealistic and unprovable
from a scientific perspective. Unfortunately, these scientifically unrealistic expectations result in impractical acceptance
criteria and the arbitrary and capricious rejection of product. The cost of monitoring, investigations and identification
efforts is borne by the end user, and in many instances fails to bring any real benefit in reduction of product risk.
Can sterility ever be completely assured?
Sterility can never be guaranteed, and this represents a major technical disconnect between current regulatory policy and
scientific reality. The sterility test as we know it today dates to the 1930s when processes were markedly less capable. In
today's aseptic processing, its utility is highly questionable. The sampling limitations are well documented and, unfortunately,
unfixable. Until such time as we have a universally accepted nondestructive sterility test for products, there is simply no
means to assure sterility.
The media fill test is also, as many scientists and engineers have noted for years, merely a snapshot in time and not a method
by which an aseptic process can be truly validated. It is important to remind ourselves that we can neither test nor monitor
sterility (an attribute that can't be analytically measured) into our aseptically produced products.
My recent paper with Jim Akers entitled "The Myth Called Sterility" reviews this in some detail. It outlines what we called
'Sterility by Design', which is a group of interrelated design concepts that can at least assure 'safety' if not 'sterility'.1 If we were honest with ourselves, that is really all we have ever needed to have with respect to parenteral products.