SUNSCREEN COMBINATIONS AND SPF 143 Table II Table of SPF Values and Cost/SPF Ratios of Test Lotions Percent Additive Average Standard Cost/SPF sunscreen sunscreen SPF* deviation Cost ratio 7.5% PAD. O + 2% OXY 18 2.56 4.53 4.04 3% OXY 19 2.43 4.91 3.85 4% OXY 23 4.48 5.57 4.07 5% OXY 23 4.44 6.23 3.69 6% OXY 28 5.39 6.89 4.10 2% O.S. 16 3.14 3.46 4.55 3% O.S. 15 2.39 3.73 4.07 4% O.S. 18 3.59 4.00 4.40 5% O.S. 21 3.65 4.27 4.86 4% HMS 16 2.66 3.64 4.30 6% HMS 15 2.39 3.99 3.81 8% HMS 18 3.43 4.34 4.17 10% HMS 20 3.15 4.70 4.16 12% HMS 22 3.19 5.05 4.42 7.5% CINN + 2% OXY 21 2.27 5.62 3.77 3% OXY 20 3.07 6.28 3.26 4% OXY 22 3.88 6.94 3.20 5% OXY 19 5.09 7.60 2.47 6% OXY 23 4.89 8.26 2.79 2% O.S. 15 2.93 4.83 3.16 3% O.S. 17 3.31 5.10 3.35 4% O.S. 18 2.71 5.37 3.34 5% O.S. 18 3.47 5.64 3.20 4% HMS 16 1.82 5.01 3.28 6% HMS 16 2.68 5.36 2.90 8% HMS 19 2.45 5.71 3.38 10% HMS 17 1.88 6.07 2.78 12 % HMS 20 4.04 6.42 3.14 Abbreviations: OXY, oxybenzone O.S., octyl salicylate HMS, homosalate PAD. O, padimate O CINN, octyl methoxycinnamate. * The SPF testing procedure is performed by using a 25% plus or minus exposure range. Therefore the accuracy of each result has a 25% error factor. The listed SPF values are an average of these results. DISCUSSION SPF VALUES The combinations using oxybenzone yielded the highest SPF numbers. However, within the mid-SPF ranges (15 to 21), all the test materials performed well. Padimate O yielded the highest SPFs for each of the maximum concentrations. With lower con- centrations of the additives, the octyl methoxycinnamate combinations yielded the highest SPFs. COST EFFICIENCY Dividing the chemical cost of the lotion by its SPF value determines a cost ratio for each

29 O.M.C. vs PADIMATE 0 SPF vs PERCENT SCREEN 28 27 26 25 24 23 22 21 20 19 18 17 16 15 26 2 ,3 4 5 6 7 8 9 10 PERCENT SUNSCREEN PAD.O-oxy + PAD.O-O.S. o PAD.O-HMS A OMC-OXY v OMC-HMS Figure 1A. SPF values of both groups of test lotions. CINNAMATE W/ OXY,O.S.,HMS SPF vs PERCENT SCREEN I i 11 12 x OMC-O.S. 25 24 25 22 21 2O 19 18 17 16 15 2 ,3 4 5 6 7 8 9 10 11 12 % SCREEN [] OXY + O.S. o HMS Figure lB: SPF values of octyl methoxycinnamate combinations.