180 JOURNAL OF COSMETIC SCIENCE cystine residues also may cause the hair to lose some of its natural ability to absorb UV light. Exposure to light induces the oxidative destruction of disulfide and phenolic side chains of the polypeptide chains. The light quanta induce the formation of free radicals that attack the disulfide bonds by chain reactions. Lengthy exposure to sunlight, especially in the summer or in southern regions where the exposure to sunlight is stronger and longer, can bring 20-40% weakening of the hair structure. Air- and water-borne pol- lution can also contribute to the oxidative damage of hair. In urban areas a great deal of polynuclear hydrocarbons and heavy metal oxide-containing pollutants are airborne and adsorb onto the hair surface. Many of these materials are light sensitizers capable of converting oxygen molecules into oxygen species. These attack and oxidize hair and degrade it (2). A particularly interesting aspect of the present study is the effect of cinnamic acid. Cinnamates are an important class of sunscreen, perhaps most notably as octylmethoxy- cinnamate. Since our studies are carried out in aqueous media where octylmethoxycin- namate would not be soluble, we used cinnamic acid as a functional model for cinnamate sunscreens. The absence of a DMPa-aH signal for hair irradiated in the presence of buffered 10 mM cinnamic acid (Figure 7) is an indication that the additive either prevents the formation of oxyradicals (0' 2- or OH') or competes effectively for them with the spin trap. Since, at the concentrations and wavelengths used here, cinnamic acid has no significant absorbance, the mode of action in quenching the oxyradical signal is not simply by blocking or absorbing light. An alternative mode of action for cinnamic acid is scavenging Ha,. Other aromatic hydrocarbons such as benzoic acid are used as Ha- scavengers due to their ability to compete for Ha. via aromatic hydroxylation. This observation may have significant implications for the use and development of sunscreens. Sunscreens used in skin care are not always desirable in hair care since they tend to be lipophilic and, as such, impart an undesirable oiliness to the hair. Furthermore, strat- egies in developing sunscreens for skin care may not yield materials optimal for hair care since different mechanisms may be operative and/or have different levels of importance in one versus the other. For example, the reaction of skin to UV-Vis radiation involves immunological responses not possible for hair. CONCLUSION Reduced oxygen radicals have been postulated during photoirradiation of hair, and the results of our studies provide direct evidence for the production of oxyradicals from human hair under UVA-visible irradiation. In addition, we have shown the value of combining direct ESR measurements and ESR spin trapping with a novel fluorescent probe for hydroxyl radical production. Terephthalate ion proves to be a convenient probe for the study of the production of hydroxyl radicals from irradiated samples of melanin and human hair, with potential utility in other areas. While we must emphasize the need for carefully prepared blank experiments, the relatively high excitation wavelength for HTA allows the presence of a variety of additives, including the radical scavengers used in this study and in our experiments with melanin (25). Our results indicate that bleached and red hair give a greater net yield of hydroxyl radical than brown hair under irradiation, reflecting the role of eumelanin in darker hair

OXYRADICALS FROM PHOTOIRRADIATED HAIR 181 as a more effective radical scavenger. Various other factors, including porosity, metal ions and melanin content, can influence the extent of oxygen radical production and photo- degradation of hair. Eumelanin and pheomelanin differ in composition, and regardless of type, the amount varies between individuals in the range of 1-4%. Small amounts of metals are endogenous to hair but are also impacted by exogenous factors such as water hardness. Porosity is mainly a function of environmental stress, such as combing, light, chemical treatment, etc. Our studies demonstrate convenient methods for assessing oxygen radical production in hair and, in combination with other methods, provide the potential to correlate hair damage with oxygen radical production under the influence of various factors. ACKNOWLEDGMENTS Financial support from Zotos Corporation is acknowledged. The authors thank Drs. P. and A. Rieger of Brown University for providing the ESR spectrometer and for their helpful suggestions. REFERENCES (1) (2). (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) j. Jachowicz, Hair damage and attempts at its repair, J. Soc. Cosmet. Chem., 28, 6 (1984). C. Robbins, Chemical and Physical Behavior of Human Hair, 3rd ed., (Springer-Verlag, New York, 1994), Ch. 1, 2, 5. C. Zviak, and P. R. Dawker, The Science of Hair Care (Marcel Dekker, New York, 1989), pp. 1-44. R. Beyak, G. S. Kass, and C. F. Meyer, Elasticity and tensile properties of human hair. II. Light radiation effects, J. Soc. Cosmet. Chem., 22, 667-678 (1977). C. Pande and J. Jachowiscz, Hair photodamage: Measurement and prevention,J. Soc. Cosmet. Chem., 44, 109 (1993). L. J. Wolfram, "The Reactivity of Human Hair: A Review," in Hair Research: Status and Future Aspects, C. E. Orfanos, W. Montangna, and G. Stuttgen, Eds. (Springer-Verlag, Berlin, 1981), pp. 479-500. E. Togyyesi, Weathering of hair, Cosmet. Toiletr., 98, 29-33 (1983). E. Scott and L.J. Wolfram, The weathering of pigmented hair, Proc 4th International Wool Textile Research ConjCrence, Berkeley, (1970). A. Deftandre, J. C. Garson, and F. Leroy, Photoaging and photoprotection of natural hair, 16th IFSCC Congress Poster Presentations, New York, (1990). C. Dubief, Experiments with hair photodegradation, Cosmet. Toiletr., 107, 95 (1992). M.L. Tare, S.B. Hornby, ¾. K. Kamath, and H. D. Weigmann, Effect of UV exposure on hair properties. Preprints, SCC Annual Scientific Seminar, Cleveland, 1995. J.P. Pavlichko, Sunscreens in hair care products, Drug Cosmet. Ind., 3540 (December 1985). M. M. Grosgrove, M. A. Collins, and R. A. Grant, in First European Biophysics Congress, E. Broda, A. Locker, and H. Springer-Lederer, Eds. (Wiener Medizinischen Academie, Vienna, 1971), pp. 87-93. G.J. Smith, New trends in photobiology: Photodegradation of keratin and other structural proteins, J. Photochem. Photobid. B. Biol., 27, 187-198 (1995). A. Shatkay, Differentiation between various species of free radicals appearing in irradiated keratin, Text. Res. J., 41,975-978 (1971). G. J. Smith, The effect of light at different wavelengths on electron spin resonances in wool, Text. Res. J., 46, 510-513 (1976). A. Shatkay and I. Michaeli, EPR study of wool irradiation with blue light, Photochem. Photobid., 15, 119-138 (1972). I. H. Leaver, Physicochemical study of the cotton cellulose-dimethylolpropyleneurea reaction, Text. Res. J., 38, 729-734 (1968). G. J. Smith, Effect of bound metal ions on photosensitivity of wool, N. Z.J. Sci., 17, 349-350 (1974).