Complex sentence: The primary need is for additional safety measures to prevent fuel escaping from the tanks in which it is stored, and to deal adequately with fuel when it does escape, preventing it from forming a flammable vapour and pollutants from poisoning the environment.
Split into simpler sentences: The primary need is for safety measures to be in place to prevent fuel from exiting the tanks in which it is stored. Added safety measures are needed for when fuel does escape, mainly to prevent it forming a flammable vapour and stop pollutants from poisoning the environment.