4. Nothing in paragraph 1 shall require an enforcing authority to keep in a register maintained by it–
(a)monitoring information relating to a particular installation or a mobile plant four years after that information was entered in the register; or
(b)information relating to a particular installation or mobile plant which has been superseded by later information relating to that installation or mobile plant four years after that later information was entered in the register,
but this paragraph shall not apply to any aggregated monitoring data relating to overall emissions of any substance or class of substance from installations or mobile plant generally or from any class of installations or mobile plant.