The objective of our study was to compare the in vitro and in vivo determination of the ultraviolet protection factor (UPF) of fabrics.
Five different viscose fabrics were investigated. Two of these fabrics had undergone a special treatment to confer UV protection.
During the in vitro testing, the UV transmission of the fabric samples was measured in the 280-390 nm wave length range with a Cary 3 Bio (VARIAN) spectrophotometer.
The UPF of the fabrics was then calculated from the data obtained.
The in vivo measurements were made on the backs of 10 subjects with healthy skin; these measurements served as a check of the UPF values measured in vitro. A sun simulator served as the radiation source.
The three fabrics which had received no special treatment yielded UPFs of 14 to 16, whereas UPFs between 33 and 35 were measured in the two specially treated fabrics. During the in vivo measurement series, it was noted that the fabrics with low UPFs did not produce the UPF values obtained during the preceding in vitro measurements. In the specially treated viscose fabrics, on the other hand, the UPF values measured in vivo were at least as high as, and sometimes higher than, the in vitro values.
This study has shown that - for fabrics with low UPF values at least - in vitro determination of UPF values is not sufficient.