Additives are commonly formulated into polymers to stabilize them against thermo-oxidative and photo-oxidative degradation. However, the additives themselves undergo degradation in the polymers, especially when the polymers are placed in hostile environments. This study focuses on the degradation of additives in chemical and photo-oxidizing environments; i.e., spas and xenon are, respectively. HPLC-UV/vis, FT-IR, and GC-MS techniques were utilized to follow the degradation chemistry of the additives. The chemistry was determined for additive degradation by spa chemicals, but the degradation chemistry of benzotriazoles remains elusive due to the insolubility of the resinous degradation products.