CURRENT PERSPECTIVES ON AEROSOL TOXICITY 273 today as perfumes. Most cosmetics contain approximately 0.5% perfume oil colognes about 4% and perfumes up to 20%. Each of these perfume sub- stances may contain up to 50 different chemical ingredients, so the task of identifying the cause of an allergic response is, at best, a difficult one (6). Photosensitization is a type of allergic response and has been reported for a number of essential oils, such as neroli, pettigrain, cedarwood, lavender, and bergamot (6, 14). In addition, dermatitis has been reported following the use of oil of bergamot. Chlorophyll, traces of copper, and psoralens, all found in oil of bergamot, are suspected of being the cause of the allergies. Aging of the oil reduces its sensitizing propensity (6). Even once the allergy-causing ingredient has been found, the problem of cross-sensitivity may arise. Persons allergic to oil of citronella, for example, are also often allergic to lemon oil (15). A partial solution to the problem of allergy to perfume oils may have been found with the marketing, by a number of companies, of a group of chemical- ly-reproducible perfume substances which have been patch tested to prove a low incidence of allergic responses (16). Hypoallergenie cosmetics may be another soIution. These are a group of cosmetic products, marketed by a few companies, which are specifically for the use of individuals hypersensitive to many cosmetics. The raw materials for these products are selected on the ba- sis of a reported low incidence of allergic responses (6). The pyrethrins, found in many insecticide aerosols, may also cause a variety of allergic manifestations in susceptible individuals erythema, rash, loss of feeling in exposed parts of the skin, and diminished vision have all been re- ported (10). Another type of toxicity, though less important, that may result from the active or inert ingredients in many cosmetic aerosols, is primary irritation of the skin (17). This is not an allergic response but rather is a result of the caustic nature of certain ingredients in the formulation. Calcium thioglycolate is a primary irritant found in many aerosol foam depilitories (6). Antiperspir- ants often contain salts of zinc, zirconium, or aluminum which can cause primary irritation (6). Ocular irritation from dandruff shampoos has been reported (18, 19), probably as a result of certain zinc salts. EFFECT OF AEROSOLS ON ANATOMY AND PHYSIOLOGY OF THE SKIN AND RESPIRATORY SYSTEM The underlying cause of many of the toxic reactions resulting from the use of cosmetic and household aerosols seems to be the result of an alteration in the basic anatomy and/or physiology of the skin and respiratory systems. The type of alteration produced depends, to a degree, on the product in question and the area of the body it comes in contact with. Alterations in skin pH are thought to be the basis for the primary irritation produced by the depilitories in foam aerosols. Preparations containing calcium fifioglycolate, for example,

274 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS usually have a pH of about 12, while the normal pH of the skin is between 4 and 6 (6). The metallic salts of zinc, aluminum, and zirconium used in aero- sol antiperspirants may cause superficial skin infections because they produce narrowing of the ducts of sweat glands which may give rise to apocrine sweat gland occlusion and a true hydradentitis (6, 18). The refrigerant action of propellants in personal or household aerosols can produce cooling or freezing of the sensitive corneal (5) or vaginal (7) tissues if they are used improperly. Many facets of skin metabolism, includ- ing cellular respiration, can be altered by some cosmetic aerosols (20). The propellants have been reported to sensitize the myocardium to arrhythmias caused by anoxia and catecholamines (21), although there is no definitive evidence that this type of cardiac toxicity can result from normal use of any aerosol product (22, 23). The interruption of the normal bacterial flora of several body orifices was formerly a potential problem with vaginal deodorant sprays containing antibacterial agents (24). It is known that once the normal flora of the vagina or rectum is altered (as with tetracycline therapy), an abnormal overgrowth of yeasts and fungi (usual symbionts in these areas) may cause pruritis (25) and/or other bacterial infections. Since most vaginal sprays no longer contain antibacterial chemicals, this problem has essentially ceased to exist. Keratitis, due to a foreign body reaction of the skin, has been reported in response to the presence of materials from several household aerosols that have, in effect, been driven into the skin by the force of the spray (5). An increased formation of pulmonary edema fluid and lipid pneu- monia has been reported following a foreign body response to the inhalation of oil droplets from an aerosol containing a vegetable oil (11). Edema fluid is an ideal medium for the groxvth of pathogens, resulting in aspiration pneumo- nia. A slight reduction in specific airway conductance, posing no clinical danger, has been reported following the inhalation of several bronchodilator aerosols. The bronchoconstriction reported, which was less than that caused by smoking a cigarette, was attributed to the aerosol propellant and/or the surfactant chemicals (sorbitol trioleate and soya lecithin) contained in the two bronchodilator aerosols evaluated (26). PROPELLANT TOXICITY AND ABUSE The controversy regarding the toxicity of aerosol products, in general, and the propellant chemicals they contain, in particular, began several years ago with the publication in the lay press of several deaths due to "sniffing," especially by teen-agers, of the vapors from a wide variety of aerosol products (27). The practice involved the deliberate, deep inhalation of the concen- trated vapors, usually from a balloon or paper bag (28). These reports of aerosol abuse brought the toxic potential of the various propellants to the attention of the aerosol industry. The toxicity of the pro- pollants can be divided into three major categories: toxicity due to the refrig-