Chronic Health Effects
Hexachlorobenzene is listed as a "possible carcinogen" by the IARC (International Agency for Research on Cancer). On the U.S. National Toxicology Program's (NTP) Carcinogen List, it is ranked as "Reasonably Anticipated to Be a Carcinogen," and the U.S. EPA lists it as a "probable carcinogen."
It is listed as an endocrine disruptor by the EU (European Union Prioritization List for Endocrine Disrupting Compounds) and as a "probable" endocrine disruptor by the Illinois EPA.
Hexachlorobenzene also has reproductive/developmental effects: it is listed on the State of California's Proposition 65 List (a list of chemicals "known to the State to cause reproductive and developmental toxicity" that is maintained by the State of California under the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65)).
Chronic exposure to hexachlorobenzene has shown to cause liver damage in rats and one incident of overexposure in Turkey (in the 1950s) showed that infants who ingested a large amount may have lower survival rates (#ATSDR).
Health studies from accidental ingestion of HCB-treated seed grain in Turkey:
Hexachlorobenzene episode in Turkey
Evaluation of reproductive outcomes in women inadvertently exposed to hexachlorobenzene in southeastern Turkey in the 1950s
Epidemiology of hexachlorobenzene-induced porphyria in Turkey: clinical and laboratory follow-up after 25 years