HYGIENIC MANUFACTURE AND PRESERVATION 735 sterilization may well appear greatly to exaggerate the need for elaborate precautions in the manufacture of products which are not required to be truly sterile. The ultimate answer must depend on the results of micro- biological control testing if a consistently low level of contamination is already achieved, housekeeping is obviously adequate for the purpose but when high counts or potential pathogens are found, the production arrange- ments should be carefully re-examined. Important facets of this problem are whether the product tends to encourage microbial growth and whether the preservative is in danger of being overwhelmed. Quite small "pockets" of contamination, protected in one way or another from the usual cleaning or sterilizing procedures, can sometimes lead to a rapid and overwhelming increase of contamination in the bulk output constant vigilance is therefore necessary, if only to avoid such catastrophes which can be exceedingly difficult to overcome quickly. 3.9 Avoidance of contamination from human sources Personnel can play an active part in the introduction or in the preven- tion of contamination within manufacturing areas and they should be encouraged to have a continuing awareness of contamination problems. This should be done by instruction in the fundamentals of personal and factory hygiene. They should be encouraged to report minor ailments which may constitute a source of contaminating infection in the production process. Apparently healthy personnel may act as carriers for various microbial contaminants and bacteriological checks are advisable if difficulty is encountered in tracing sources of product contamination. Much can be accomplished by providing ample modern washing facilities before beginning work and after using the lavatories. Taps should not be manually operated the provision of a hand dip not exceeding 10 ppm of available chlorine may be useful. Disposable towels should be employed. Suitable clean protective clothing should be supplied including, where appropriate, caps, hair nets, gloves, and masks. It is essential to insist that such clothing should be worn and changed frequently. Personal effects should not be allowed in the washing area. Access to washing facilities should be freely available and cleanliness in changing rooms should conform to the same standard as in the working area. 4. MICROBIOLOGICAL QUALITY CONTROL Microbiological quality control serves four main purposes:

736 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 1. To check that plant hygiene is satisfactory. 2. To monitor the microbial contamination in raw materials. 3. To assess the microbial status of finished products. 4. To check that preservative capacity is adequate. To carry out such testing on every raw material supply and every batch of finished product, with daily or even hourly testing of the manufacturing plant and using all the possible test methods would be prohibitively ex- pensive and would cause unjustifiable production delays. It is therefore of great importance to establish a testing scheme appropriate to the actual circumstances in an individual production unit. The main aim will be to ensure gradually improving quality of output, along with early warning of adverse changes, rather than to "pass" or "fail" production batches in a purely routine fashion. Microbiological quality control should be initiated at the start of pro- duction with regular examination of plant in which the products are manufactured and proceeding to cover raw materials, including the water supply and packaging components. Frequent checks are desirable at all stages of a manufacturing process so that if contamination does occur, its point of onset is easily established and action can be taken to prevent a recurrence. Full records of all microbiological examinations will prove invaluable if complaints are received some time after manufacture and sale. The quality control programme for raw materials should include provision for quarantine on all items liable to be heavily infected until results are reported and evaluated, along with in-line testing on occasional product batches to determine microbiological changes in processing. Finished product testing should assess sterility or an acceptable microbial status for the particular product. Tests should be made for any pathogens previously encountered, unless the product has previously been shown to be self-sterilizing or unless production batches are found to be consistently sterile. The plant should be examined for the presence of specific pathogens and for micro-organisms, including fungi, likely to cause spoilage of the product or harm to the consumer. All valves, traps, pressure-relief valves and working surfaces should be swabbed periodically and the swabs cultured and counts performed. Pipe-lines should be taken apart where possible and washed through with sterile physiological saline or Ringer's solution viable counts should be performed on the washings, which should also be examined on selective media for the presence of potential pathogens. Manufacturing