If you're not getting a sunburn/welders tan then the clothing is blocking UVB and C although obviously once faded it's more likely to reflect light. UVA is the one that used to be safe (sunbeds) then became the primary cause of premature of skin aging and is currently (i think) thought to be responsible for the rarer but more deadly skin cancers. UVA is the one that fades furniture/upholstry through windows but as it's the main cause of a 'healthy' tan i would have thought if you are getting a high dose you'd see it