Solvents are compounds that dissolve things. Water is a useful, life giving solvent. Most other solvents dissolve fats and are life threatening, because fats form the membrane wall around each of our cells, especially our nerve cells.
The solvent that does the most harm is benzene. It goes to the thymus, ruins our immune system, and causes AIDS. The next worst solvent is propyl alcohol. It goes to the liver and causes cancer in some distant organ. Other major culprits of disease are xylene, toluene, wood alcohol, methylene chloride, and trichloroethane (TCE). I'll discuss each one later, with the ailment it's associated with.