The limitation provided by Sections 15-3-640 through 15-3-660 may not be asserted as a defense by any person in actual possession or control, as owner, tenant, or otherwise, of the improvement at the time the defective or unsafe condition constitutes the proximate cause of the injury or death for which it is proposed to bring an action, in the event such person in actual possession or control knows, or reasonably should have known, of the defective or unsafe condition. The limitations provided by Sections 15-3-640 through 15-3-660 are not available as a defense to any person guilty of fraud, gross negligence, or recklessness in providing components in furnishing materials, in developing real property, in performing or furnishing the design, plans, specifications, surveying, planning, supervision, testing or observation of construction, construction of, or land surveying, in connection with such an improvement, or to any person who conceals any such cause of action. The limitation provided by Section 15-3-640 may not be asserted as a defense to any action for personal injury, including a personal injury resulting in death, or property damage which is (i) by its nature not discoverable in the exercise of reasonable diligence at the time of its occurrence and (ii) the result of ingestion of or exposure to some toxic or harmful or injury producing substance, element, or particle, including radiation, over a period of time as opposed to resulting from a sudden and fortuitous trauma.