Personal susceptibility to pitch.

160-166. During the years 1957 to 1963, 59 cases of hyperplastic squamous lesions were referred to us from a local patent fuel works where ovoids were made by fusing coal dust and pitch together by steam heat. We carried out a survey of all the personnel exposed to the pitch hazard and at the same time examined a control group of men of the same age group. The pitch workers examined totalled 144 and they were re-examined after a period of two years. The control group consisted of 263 persons selected from dermatological out-patients. The clinical findings were classified into six main groups: (1) benign proliferative lesions; (2) pre-malignant and malignant epidermoid lesions; (3) pitch acanthoma (pitch warts); (4) photo-sensitivity; (5) acneiform lesions; and (6) scrotal changes. 1. Benign proliferative lesions: There was little difference between the incidence of these lesions in the pitch workers and in the control group. 2. Pre-malignant and malignant epidermoid lesions: (a) Squamous keratoses were slightly more common in the pitch workers (12%) than in the controls (10%). (b) Chronic tar dermatosis was found in 5% of pitch workers who had an exposure to pitch ranging from 30 to 50 years. No controls showed these changes. (c) Squamous-cell carcinoma incidence was 2·8% in pitch workers compared with 0·4% in the controls. 3. Pitch acanthoma: At the initial examination the incidence of pitch acanthoma in the pitch workers was 3·5% compared with 2·7% in the controls. However, on the two-year follow-up there was an increase in incidence in the pitch workers of 15·7%. Only 10·4% of all pitch workers developed pitch acanthoma. The incidence was related not only to the duration of exposure but also to the degree of pitch contamination of the skin. The highest incidence was recorded in those with the greatest skin contamination, 24% compared with 3·2% in those with low exposure. Spontaneous regression was noticed in 26% of cases. 4. Photo-sensitivity: 57 (4%) pitch workers recorded photo-sensitivity (`smarts'). There was no relationship between the incidence of `smart' and pitch warts or acne. 5. Acneiform lesions: All acneiform lesions were much more common in the pitch workers (93%) than in the controls (31%). 6. Scrotal changes: 13·5% of all the pitch workers showed one or more of our recorded lesions. There was a 3·5% incidence of kerato-acanthoma and there was one squamous carcinoma. In this series there is an increased susceptibility to some proliferative lesions, either premalignant or malignant, in pitch workers when compared with the controls. Only 10·7% of the working population were affected with pitch acanthoma and of these 50% had multiple warts. Even though there is an increasing incidence with increased exposure, this is not absolute and our findings suggest that there is also a personal susceptibility to pitch.