[Investigation of toxicity through human cases and animal experiments--study of bromopropanes]

In 1995, workers in a Korean electronic factory exhibited oligospermia or amenorrhea. We investigated the toxicity of 2-bromopropane used as an alternative to chlorofluorocarbons in the factory in animal experiments, and clarified that exposure to 2-bromopropane depletes spermatogenic cells in male rats and oocytes in female rats. Subsequently, we investigated the neurotoxicity of 2-bromopropane on the basis of the reported neuropathy in the Korean workers exposed to 2-bromopropane. For comparison, we employed 1-bromopropane, which is now used as a new alternative to chlorofluorocarbons. The results showed that 1-bromopropane is more neurotoxic than 2-bromopropane, causing harm to reproductive organs by inhibiting spermiation in the testis and impairing follicular development in the ovary. Shortly after the initial investigation of 1-bromopropane in animals, human cases were reported in the United States. Neurologic abnormalities in Chinese workers exposed to 1-bromopropane were also reported, such as the elongation of distal latency and lowered sense of vibration in the lower limbs. Thus, these serial studies revealed that 1-bromopropane is neurotoxic, but its dose-response relationship in humans remains unknown. In the investigation of 2-bromopropane toxicity, initial animal studies were designed on the basis of human studies, while in research on 1-bromopropane, animal studies preceded human studies and contributed to the prediction of toxicity in humans. However, the use of animal model is limited in its ability to predict the toxicity of chemicals introduced depending on species differences. Further studies should focus more on the differences and commonality between animals and humans in response to toxic agents.