Benzene is a solvent chemical, older cleaning solvents for firearms and certain car parts consisted of a nitrobenzene component, and this has since caused health problems. According to a website I stumbled across, people who develop these health problems can get free health care and maybe even money for pain and suffering. Conditions associated with this include lung and neurological disorders, lymphoma, both Hodgkin's and non-Hodgkin's, acute myelogenous leukemia, and skin cancer. It' similar to legalities regarding asbestos, the person has to prove their disease was related to exposure, which is a difficult and complex thing to determine. Fortunately, modern cleaning agents for firearms are unlikely to cause any of these problems as long as they are not misused.