The two main expressions used in relation to the operation of pharmaceutical clean rooms are not synonymous: environmental control and environmental monitoring.
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Environmental control describes the systems functionally ensuring that clean rooms operate within predetermined limits. There are many such systems, integrated and overlapping, described in Chapter 3.
Environmental monitoring describes the techniques used to measure the effectiveness of the environmental control systems, and defines the procedures necessary in the event of limits being exceeded.
Environmental control, particularly in sterile manufacture, is achieved by means of many factors: well-designed and efficiently operated facilities and air-handling systems, by the use of integral HEPA filters, well-designed and well-made garments, by reliable disinfection regimes, and by rigid adherence to aseptic disciplines.
Information on the operation of all such factors is obtained from a variety of physical monitors. These include pressure differentials, air flows, supervision and other systems that can, if required, be linked to feedback control. Pressure differentials may be lost for short periods with minimal impact on sterility assurance, and occasional lapses in aseptic disciplines can never be totally excluded. Environmental control is best achieved by physical means, by feedback, and by automated alarms — means that respond in "real time" and can lead to immediate correction of lapses.
Microbiological environmental monitoring, however, looks indirectly at the environmental control systems. It is intended to measure the end product of such systems, i.e., the microbiological quality of the clean room.
Microbiological environmental monitoring has no immediacy. Results are not obtainable until days after the data collection, and later than the events that the data describe were occurring. Rarely are adverse microbiological results reproducible on re-examination. So often they are a case of too little, too late.
From experience, microbiological environmental monitoring is a necessary and valuable means of disclosing lapses in control, which may not be signalled by any other means. This most typically happens with regard to personnel. The periodic presence of a quality assurance (QA) microbiologist taking environmental samples is undoubtedly a reminder to production personnel of the importance of asepsis, particularly if the environmental microbiologist is also involved in aseptic training and periodic retraining of the operators. The microbiologist's own practices and techniques must be beyond reproach.
Conversely, all time-served production operators remember occasions when they may have "screwed up" only a few minutes before a microbiological monitoring, and escaped with satisfactory results. They will also know of many occasions when they could, "hand on heart" with absolute certainty, testify that they had done nothing wrong, but the microbiological results indicate the contrary. In other words, the results of microbiological monitoring are erratic.
Environmental monitoring is one of the frequently criticised areas in regulatory inspections. An FDA inspector once said to the author: "Finding problems with environmental monitoring techniques, programs, results and responses is like shooting fish in a barrel!"
Good environmental microbiologists understand sound laboratory controls and have detailed facility and process knowledge. Good microbiological monitoring programs are unique to particular facilities; they must focus both on known vulnerabilities (validation may disclose these) and on discovering unknown vulnerabilities. Good environmental microbiologists analyse their data regularly, looking for changes to established patterns and for trends.
The purpose of microbiological environmental monitoring is to discover the unexpected, unpredicted vulnerability of facility or process to microbiological contamination. Its limitations are speed of response (too slow) and consistency (erratic nonreproducible results).
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