Commentary on 'UVB-SPF': the SPF labels of sunscreen products convey more than just UVB protection

The FDA recently published a proposed amendment of the Final Monograph for OTC Sunscreen Products. Among the proposals, FDA revised solar simulator performance specifications and additional labeling for sunscreen products. The maximum allowable labeled sun protection factor (SPF) was increased to SPF 50 while simultaneously requiring it to be called 'UVB-SPF'. UVB accounts for 80-91% of the erythemic effectiveness of the UV solar simulator specified in the amendment. Analysis of the specified solar simulator spectrum used to determine SPF indicates that if 100% of the UVB is blocked, it is mathematically impossible to achieve an SPF in excess of approximately 11 without also blocking at least some UVA. Consequently significant UVA protection must be provided for sunscreen products to achieve SPFs of 15 and higher. At the maximum allowed SPF 50, where only 2% or less of the effective UV risk remains, the minimum reduction of UVA erythemal effectiveness must by definition be 78-90%. While mandating UVA protection criteria is doubtless important, especially as it relates to sunscreen photostability, there is no utility in, or basis for, the proposed 'UVB-SPF' descriptor as existing high SPF labeling indicates both UVB and UVA protection.