Tanenbaum L, Parrish J A, Pathak M A, Anderson R R, Fitzpatrick T B
Arch Dermatol. 1975 Apr;111(4):467-70.
The photoxicity of coal tars was determined by comparing the ultraviolet light (UVL) energy required to produce erythema at tar treated sites (minimal phototoxic dose [MPD]) with the energy required to produce the same degree of erythema at untreated control sites (minimal erythema dose [MED]). The ratio of MED/MPD is the photoxic index (PI). Tars that were phototoxic had a PI of greater than 1. Using a UVA (320 to 400 nm) and a tuvb (290 to 320 nm) light source, 15 subjects and six tars were tested. All tars were phototoxic to UVA but not to UVB (P smaller than 0.0001). Although tar and UVL is a widely accepted treatment for psoriasis (Goeckerman therapy), the light sources employed at normal exposure times provide insufficient UVA energy to produce a phototoxic reaction to the tars are used. The therapeutic response seen in psoriatic patients treated with tar and UVL should therefore not be attributed to tar phototoxicity.
通过比较在焦油处理部位产生红斑所需的紫外线（UVL）能量（最小光毒性剂量[MPD]）与在未处理对照部位产生相同程度红斑所需的能量（最小红斑剂量[MED]），来确定煤焦油的光毒性。MED/MPD的比值即为光毒性指数（PI）。具有光毒性的焦油其PI大于1。使用紫外线A（320至400纳米）和紫外线B（290至320纳米）光源，对15名受试者和6种焦油进行了测试。所有焦油对紫外线A具有光毒性，但对紫外线B无光毒性（P小于0.0001）。尽管焦油和UVL是治疗银屑病的一种广泛接受的方法（Goeckerman疗法），但在正常暴露时间所使用的光源提供的紫外线A能量不足，无法对所使用的焦油产生光毒性反应。因此，接受焦油和UVL治疗的银屑病患者所观察到的治疗反应不应归因于焦油的光毒性。
