In Montrose Chemical Corp. v. Admiral Ins. Co. (1995) 10 Cal. 4th 645, a landmark case involving the disposal of hazardous waste causing damage both before and during the periods covered by the insurer's policies, the California Supreme Court adopted the " 'continuous injury' trigger of coverage . . . for third party liability insurance cases involving continuous or progressively deteriorating losses." (Montrose, supra, 10 Cal. 4th at p. 655.) "In the third party liability insurance context, 'trigger of coverage' has been used by insureds and insurers alike to denote the circumstances that activate the insurer's defense and indemnity obligations under the policy." (Ibid., fn. 2, ) In Montrose Chemical Corp. v. Admiral Ins. Co., the plaintiffs sought damages for toxic waste contamination released by the defendant. The lawsuit alleged that bodily injury and property damage "occurred on a continuous basis, commencing in 1956 and extending to the present." (Id. at p. 657.) The California Supreme Court examined insurance coverage under comprehensive general liability policies "triggered" by damage or injury occurring during the policy periods. The court held that "property damage that is continuous or progressively deteriorating throughout successive comprehensive general liability policy periods is potentially covered by all policies in effect during those periods." (Id. at p. 673; see also id. at p. 689.) The California Supreme Court held that "bodily injury and property damage that is continuous or progressively deteriorating throughout several policy periods is potentially covered by all policies in effect during those periods." (Id. at p. 655; see also id. at pp. 654-655, 675, 685-689.) In other words, it adopted the "'continuous injury' trigger of coverage." (Id. at p. 655.) In sum, seven insurers had issued a series of liability policies, collectively covering the period from 1960 to 1986. Admiral Insurance Company (Admiral) had issued polices covering only the last four years of this period. (Montrose, supra, 10 Cal.4th at p. 656.) The issue before the court was whether Admiral had a duty to defend actions alleging either continuous or progressively deteriorating bodily injury or property damage, resulting from toxic chemicals manufactured by the insured, that began before, but continued during, Admiral's policy periods. Admiral argued that a "manifestation" trigger of coverage applied; in other words, the only relevant "occurrence," within the meaning of its policies, was when appreciable bodily injury or property damage first appeared. (Montrose, supra, 10 Cal.4th at pp. 662-663, 669, 677 & fn. 17.) The Supreme Court disagreed. It noted that Admiral's policies defined "property damage" as " 'physical injury to or destruction of tangible property which occurs during the policy period' "; similarly, they defined "bodily injury" as " 'bodily injury, sickness or disease sustained by any person which occurs during the policy period ... .' " (Id. at p. 668.) They then defined "occurrence" as " 'an accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage ... .'" (Id. at p. 669.) The court concluded: "This policy language unambiguously distinguishes between the causative event--an accident or 'continuous and repeated exposure to conditions'--and the resulting 'bodily injury or property damage.' It is the latter injury or damage that must 'occur' during the policy period, and 'which results' from the accident or 'continuous and repeated exposure to conditions.'" (Ibid.) In Montrose Chemical Corp. v. Admiral Ins. Co. (1995) the policy used the standard language found in CGL policies at the time. It provided the insurer would "'pay on behalf of the insured all sums which the insured shall become legally obligated to pay as damages because of . . . bodily injury, or . . . property damage to which this insurance applies, caused by an occurrence.'" (Id. at p. 656.) "Property damage" was defined as "'(1) physical injury to or destruction of tangible property which occurs during the policy period, including the loss of use thereof at any time resulting there from . . . .'" (Id. at p. 668.) The policy defined "occurrence" as "'an accident, including continuous or repeated exposure to conditions, which results in bodily injury or property damage neither expected nor intended from the standpoint of the insured.'" (Id. at p. 656.) In short, the policy provided coverage so long as some bodily injury or property damage took place within the policy period, regardless of when the injury or damage began. (See id. at p. 675 "The timing of the accident, event, or conditions causing the bodily injury or property damage, e.g., an insured's negligent act, is largely immaterial to establishing coverage; it can occur before or during the policy period. Neither is the date of discovery of the damage or injury controlling. . . . It is only the effect--the occurrence of bodily injury or property damage during the policy period, resulting from a sudden accidental event or the 'continuous or repeated exposure to conditions'--that triggers potential liability coverage".)