**6. Conclusion**

Chemicals have toxic effects on the human body. Neurotoxicity demonstrates acute and chronic manifestations. A toxic chemical can produce an acute toxic response, besides prolonged exposure of a toxin may result in slowly developing chronic disease. In many cases, the putative neurotoxic damage present many years after initial exposure to the toxin. Therefore, the clinical signs elicited and symptoms expressed should be interpreted carefully. The neurotoxicity level and the circumstances of the exposure determine clinical presentation. The clinical signs and symptoms due to neurotoxicity may be expressed in central and peripheral nervous systems. Moreover, toxic agents disrupt cellular processes and result in epigenetic changes. While several heavy metals cause DNA damage which leads to carcinogenesis, the peripheral nervous system is also vulnerable to toxin-induced damage. A peripheral neuropathy may have its origin in the neurone, axon, myelin sheath or either Schwann cells. Patients may present with length-dependent sensorimotor peripheral neuropathy as well as mononeuropathy or radicular pathology. Organophosphates and acrylamide have been associated with severe damage to the motor nerve terminal. Many chemicals have the ability to cause axon damage including acrylamide, arsenic, carbon disulfide, n-hexane, lead, organic mercury, perhexilene, and thallium. Hexachlorophene and perhexilene have been involved in myelin disruption. Also, methyl mercury is well-known neurotoxin cause neuronopathy. Here, we discuss the peripheral nervous system manifestations of heavy metals, solvents, chemotherapeutics, monomers, gases and pesticides in detail.
