A few case studies have suggested that acute inhalation exposure to heptachlor may result in nervous system effects, with oral studies showing gastrointestinal effects. Animal studies have reported effects on the liver and central nervous system from oral exposure. The limited available information on the chronic toxicity of heptachlor in humans suggests that inhalation and oral exposure may be associated with neurological effects including irritability, salivation, and dizziness, while oral exposure may result in effects on the blood. Limited information is available on the developmental or reproductive effects of heptachlor in humans. Animal studies have noted developmental effects , such as fetal resorptions, and reproductive effects , such as failure of animals to reproduce, following oral exposure to heptachlor.
Human studies are inconclusive regarding heptachlor and cancer.
Animal studies have reported liver tumors in mice exposed to heptachlor via ingestion . Exceedance of the RfD does not imply that an adverse health effect would necessarily occur. As the amount and frequency of exposures exceeding the RfD increase, the probability of adverse health effects also increases. Acute inhalation exposure to heptachlor in humans has been associated with nervous system effects in a few case studies, while gastrointestinal effects, such as nausea and vomiting, have been reported to occur following accidental ingestion of heptachlor. Heptachlor is considered to have high to extreme acute toxicity based on short-term tests such as the LD 50 test in rats.