722 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS safeguard to the public. It is therefore necessary to examine xvhether special circumstances exist for which an absolute standard of sterility is warranted and, in other cases, to what extent the requirement may reasonably be relaxed. Some authorities favour an acceptance target representing a particular level of microbial contamination such as 100 micro-organisms per gramme. Contamination levels are apt to vary widely in a comparatively short space of time and the particular species of micro-organisms present may be far more significant than the actual numbers. This approach without qualifica- tions therefore has little to commend it. Standards which apply the most stringent requirements when these are particularly appropriate and which are less rigid in other circumstances, will give adequate protection for the consumer without a prohibitive increase in manufacturin• costs. A set of Standards is being prepared by the joint Select Committee of the Toilet Preparations Federation Ltd. and the Society of Cosmetic Chem- ists of Great Britain. To avoid confusion, separate recommendations are omitted from this monograph, which therefore deals mainly with methods for achieving a satisfactory level of manufacturing hygiene and techniques for establishing preservation capacity and for monitoring the extent of microbial contamination. 1.3 Definitions For the purpose of this monograph, "toiletry" and "cosmetic" are taken to be synonymous. All temperatures are given in degrees Celsius. 2. GENERAL CONSIDERATIONS 2.1 Compliance with standards Standards need to be considered in relation to the efforts necessary to achieve them and the methods to be employed for verifying compliance. For example, the selection of raw materials and packaging components free from or having a low incidence of microbial contamination will matefid ally help to avoid a high level of contamination in the finished product the bacterial content of water used in manufacturing processes is of partic- ular importance in this connection. Similarly, processing conditions should be carefully scrutinized to limit adventitious contamination. Factory design and lay-out, personnel training and arrangements for cleaning

HYGIENIC MANUFACTURE AND PRESERVATION 723 equipment all contribute materially to the problem. It is impossible, however, to define in a single document exactly how every product should be manufactured and tested, if only because the contamination hazard is closely related to the scale of manufacture which differs greatly from one firm to another and from product to product. In the process of verifying compliance with standards or of monitoring the microbiological condition of production arrangements, attention will have to be paid to the question of representative sampling. When there is a moderately high level of contamination in the material being sampled, whether or not the product is distributed in separate small units (e.g. the finished packs) and the contamination evenly spread throughout, the sampling problem is unlikely to be highly critical since precise knowledge of the level of contamination is seldom essential. If the contamination is at a low level and unevenly distributed, representative sampling may be more important, especially when its purpose is to detect the presence or absence of pathogenic micro-organisms. Another aspect of sampling is the extent of replication necessary when carrying out the appropriate tests on a particular sample. Guidance on statistical sampling methods may be obtained from various publications such as: Lowe, C. W. Industrial statistics 1 259-273. (1968). (Business Books Ltd., London). Thatcher, F. S. and Clark, D. S. Micro-organisms in food. 52-58 and Appendix V. (1968). (Toronto Press Toronto). Cowell, N. D. and Morisetti, M.D. Microbiological techniques--some statistical aspects. J. Sci. Food Agric. 20 473. (1969). Sampling theory is perhaps of greatest importance when the purpose of testing is to examine material on a pass-or-fail basis. Microbiological quality is preferably studied continuously as a preventive measure and the intelligent application of experience may provide a better safeguard than reliance on a rigid scheme of sampling. For example, a single manufacturing unit may be involved in virtually continuous production of some high- volume toiletry lines such as shampoos and in the preparation of batches of decorative make-up items at quite protracted intervals e.g. once per month. The sampling problems are hardly comparable but an experienced microbiologist will be able to devise testing procedures appropriate to the circumstances and still within the capacity of the available laboratory services. For exceptional cosmetic preparations where sterility may be the un- qualified aim, a recognized routine of sterility testing should be applied. Suitable methods are given in the Therapeutic Substances (Manufacture and Interpretation) General Regulations 1963 The United States Pharma-