Q.Give one industrial/laboratory use and one health hazard of dichloromethane (methylene chloride).

Several halogenated compounds combine genuine industrial or historical-medical usefulness with real, well-documented environmental or health hazards. Dichloromethane is a common solvent but a CNS depressant with carcinogenicity concerns on heavy exposure; chloroform, a historic surgical anaesthetic, slowly oxidises in air/light to toxic phosgene (prevented by storing it dark, full and sealed, with about 1% ethanol added); carbon tetrachloride, once a solvent and fire-extinguishing fluid, is hepatotoxic/nephrotoxic and is itself an ozone-depleting substance; iodoform, a traditional wound antiseptic, owes its action to the free iodine it liberates rather than to the molecule itself. Freons (CFCs) are inert and safe at ground level but survive intact into the stratosphere, where UV photolysis releases a chlorine radical that destroys ozone through a self-regenerating, catalytic two-step cycle ($\text{Cl}^{\bullet}+\text{O}_3 \to \text{ClO}^{\bullet}+\text{O}_2$; $\text{ClO}^{\ …