Reduction of ultraviolet transmission through cotton T-shirt fabrics with low ultraviolet protection by various laundering methods and dyeing: Clinical implications

Background: The public has long been instructed to wear protective clothing against ultraviolet (UV) damage. Objective: Our purpose was to determine the UV protection factor (UPF) of t wo cotton fabrics used in the manufacture of summer T-shirts and to explore methods that could improve the UPF of these fabrics. Methods: Each of the two types of white cotton fabrics (cotton T-shirt and mercerized cotton print cloth) used in this study was divided into 4 treatm ent groups: (1) water-only (machine washed with water), (2) detergent-only (washed with detergent), (3) detergent-UV absorber (washed with detergent a nd a UV absorber), and (4) dyes (dyed fabrics). Ultraviolet transmission th rough the fabrics was measured with a spectrophotometer before and after la undry and dyeing treatments. Based on UV transmission through these fabrics , the UPF values were calculated. Results: Before any treatments, the mean UPFs were 4.94 for the T-shirt fab ric and 3.13 for the print cloth. There was greater UVA (320-400 nm) than U VB (280-320 nm) transmission through these fabrics. After 5 washings with w ater alone and with detergent alone, UPF increased by 51% and 17%, respecti vely, for the cotton T-shirt fabric. Washing the T-shirt fabrics with deter gent plus the UV-absorbing agent increased the UPF by 407% after 5 treatmen ts. Dyeing the fabric blue or yellow increased the UPF by 544% and 212%, re spectively. Similar changes in UPFs were observed for the print cloth fabri c. Conclusion: The two cotton fabrics used in this study offered limited prote ction against UV radiation as determined by spectrophotometric analysis. La undering with detergent and water improves UPF slightly by causing fabric s hrinkage. Dyeing fabrics or adding a W-absorbing agent during laundering su bstantially reduces UV transmission and increases UPF. More UVA is transmit ted through the fabrics than UVB.