MDF or Medium-Density Fibreboard seats are cheap, but also flimsy and may pose serious health hazards. MDF seats usually have a thin outer layer that can weaken and tear off from daily use and harsh cleaning chemicals. This wear and tear can expose the inner MDF layers, which can act like a sponge that harbours germs and bacteria. Avoid using a loo with a broken MDF toilet seat, as this can raise your risk of serious illness.