Cutaneous elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin

Background After exposure, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is excreted via the faeces, breast milk and epidermal lipids. Objectives To determine to what extent TCDD is eliminated via the skin and to evaluate whether cutaneous elimination can be accelerated by the application of petrolatum. Methods In two patients severely intoxicated with TCDD, material obtained from the skin surface and, in one patient, cerumen and the content of epithelial cysts, was analysed for TCDD. Results The TCDD concentration in the initial blood sample taken was 144 000 pg g−1 blood fat in patient 1, and 26 000 pg g−1 blood fat in patient 2. Six months later, when the skin tests were performed, the blood TCDD levels had decreased to 80 900 and 16 100 pg g−1 blood fat, respectively. In the two samples of pooled cyst contents from patient 1, TCDD levels of 34 400 and 18 600 pg g−1 fat were found. A cerumen sample contained TCDD at 20 500 pg g−1 fat. In the material collected from the skin surface we observed a linear increase of the amount of TCDD measured per test field with time, indicating a continuous elimination of TCDD via the skin. The daily amount of TCDD eliminated via the skin was 1·51 pg cm−2 in patient 1 and 0·57 pg cm−2 in patient 2. Application of petrolatum led to a twofold increase in the amount of TCDD measured in patient 1, but had no significant effect in patient 2. Conclusions In our patients, elimination of TCDD via the skin, most probably through desquamating scales, represented 1–2% of the overall daily TCDD elimination rate, with regard to the body surface and when calculated on the basis of the half-life of TCDD at the time of the skin test. If a more typical overall elimination half-life of 7 years is used as the basis for the calculation, the skin would account for 9%(patient 1) and 15%(patient 2) of the overall elimination. Although we observed an increase in TCDD in material derived from the skin surface of up to 100% after application of petrolatum in patient 1, such an approach appears not to be a feasible means to increase elimination. Owing to the small amount of TCDD measured in skin-surface material, as well as in the cyst contents and cerumen obtained from one patient, contamination of the environment and other persons appears highly unlikely.