FUNDAMENTALS OF MICROBIOLOGY IN RELATION TO CLEANSING Formaldehyde is also cheap and effective but very unpleasant for the staff, and somewhat corrosive. It causes eye, nose and throat reactions at 2-3 ppm. Up to 5 ppm can be tolerated for a few minutes, but at 10 ppm it becomes almost unbearable (13). Fogs of QAC solutions appear to be both effective, cheap and without objection. Little or nothing is known of the effect of repeated inhalation of minute concentrations of QAC (e.g. 1 ppm) but in general they can be regarded as non-toxic. There has been some scare in medical circles about the use of benzene compounds in hygienic measures on account of possible carcinogenic effects, but there appears to be no real evidence for this. For example, the toxicity of benzoic acid is low. It there is any apprehension over the benzyl QAC a twin chain (C s or C •0) compound may be equally or even more effective. Walls, roofs and air in factories These problems are inter-related because whatever organisms may occur on one will be found on the others. Clearly the factory air cannot be free from contamination which occurs on walls and roofs, or is present in air outside the factory. Moulds, yeasts and algae grow readily on any surface if the RH is over 70ø//0 and the merest trace of nutrients is present. The first precaution is therefore to maintain adequate ventilation and at all cost to prevent con- densation at any time. Such condensate can be teeming with gram- negative bacteria including coliforms and Pseudomonas. The simplest and best treatment for soiled walls and other surfaces is to wet them and 1 h later to apply a penetrative, non-foaming, alkaline detergent by a spray or other suitable means. This will clean the surfaces and exercise a substantial killing effect, but in order to obtain an effective kill a suitable bactericide- fungicide must be incorporated in the detergent. If the wall, etc., has been allowed to get into bad condition, repeated treatments will be necessary. Needless to say, all walls, etc. in a cosmetics factory should have a smooth, impervious and washable surface. Methodology in hygiene Practical recommendations for cleaning, sterilizing and hygiene in public health and various industries are given in (14-19). One of the most serious problems in the teaching of the principles of

66 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS hygiene and their application is that there is no glamour, no excitement and no romance in such a subject. Heart transplants, human organ banks, the fertilization of the human ovum outside the uterus and similar topics hit the headlines, but at the most these advances save an occasional life or prolong a few lives for a few months. On the other hand hygiene has saved millions of lives and pre- vented many millions of cases of disease. The dramatic rise in the ex- pectation of life during the past 100 years is mainly due to the application of hygienic principles. No branch of medicine or science has contributed more to human health and happiness. LABORATORY CONTROL Laboratory control of cleaning and sterilizing The choice of a particular method is less important than regular testing. The ultimate criterion must always be the keeping quality and safety of the product, and it is usually easy to link the hygiene aspects in the factory with the quality of the products. The 'first product through' test, swabbings, rinsings or any other sound •hethod is adequate for both staff training and protecting the quality of the product (16). An important feature in hygiene control is that tests should be surprise tests the staff should never know when a particular piece of equipment is going to be checked. A rigid and known time-table for plant control defeats its own object. Laboratory tests are useless unless they are acted upon. I have known of a case where the head of the laboratory put his reports on the manager's desk daily, but it was not until the poor quality of the product was re- yealed later that the manager studied the reports. The testing of disinfectants, antiseptics and preservatives The high degree of competitiveness in this field results in many far- reaching claims being made by manufacturers and salesmen. Unfortunately it is not possible to assess the validity of these claims without a careful examination by an expert with adequate bacteriological facilities, a process which is time-consuming and expensive. There is no single, reliable test which can be applied to any of these preparations. Results vary con- siderably according to the technique used, and the cynic might with some reason assert that one can get almost any result one likes by selection of the