Characteristic of chloracne are comedones and epidermal cysts around the eyes, retroauricular area, and on the scrotum. Chloracne is caused by chlorinated (or brominated) aromatic hydrocarbons including polychlorinated dibenzodioxins (dioxins or PCDDs), biphenyls (PCBs), and dibenzofurans (PCDFs). A study of workers with chloracne in a large chemical factory manufacturing hexachlorobenzene in China found the blood levels were between 650 and 1200 parts per trillion (ppt). [
PMID 10583118] Acneiform lesions may appear as early as 1 to 3 weeks after dioxin exposure. Most cases of chloracne resolve within 1 to 3 years. [ATSDR Case Studies: PCB Toxicity] All patients with chloracne living in the most contaminated area of Seveso, Italy had TCDD levels of 828 to 56,000 ppt, and the chloracne had resolved in all but one patient within 7 years of the accident; [IARC: TCDD] Chloracne was not found in veterans of Operation Ranch Hand, the Air Force unit responsible for the aerial spraying of TCDD-contaminated herbicides in Vietnam from 1962 to 1971 [PubMed 9814716], nor in herbicide applicators such as the group studied in New Zealand [
PMID 15613606]. Median serum levels for the high group in Operation Ranch Hand were 195.7 ppt. Mean serum levels for the applicators highly exposed to 2,4,5-T in New Zealand were 53.3 ppt. "Although toxic effects, notably chloracne, have been observed in manufacturing plant workers, these effects have not been observed in formulators or applicators regularly exposed to 2,4,5-T or other chlorophenoxy compounds." [EPA Pesticides, p. 95]