Opinion for the Court filed by Circuit Judge WILLIAMS.
In thе early 1970s Independent Petrochemical Corporation (“IPC”), a wholly-owned subsidiary of plaintiff Charter Oil, was in the business of selling petrochemical products. As a courtesy to a customer, it arranged on several occasions for the disposal of waste oil by a St. Louis waste oil hauler, Bliss Oil, understanding that Bliss would take the oil to a waste disposal site. In fact, after Bliss Oil’s president tasted the oil to check its suitability for other uses and found the flavor fit, Bliss sprayed it as a dust suppressant at various locations throughout Missouri. The sprayings occurred over a period of at least two months, with each spraying lasting about 30-40 minutes. The waste oil turned out to contain dioxin, a chemical compound alleged to cause harm to humans, animals, and plants. 1 The disсharge of the dioxin-contaminated oil gave rise to claims against IPC by the federal government, the State of Missouri, and over 1,600 private plaintiffs, the latter seeking in aggregate $4 billion in compensatory damages and the same amount in punitive damages. IPC entered into settlements covering all of the claims and is now in bankruptcy. Its outstanding obligations include over $100 million owed to the federal government for clean-up of various sites in Missouri.
Charter and its affiliates (including IPC) sued several primary and excess insurers that had issued comprehensive general liability policies to them over the 1971-1988 period, seeking a declaratory judgment that these policies obliged the insurers to provide indemnification for all obligations arising out of Bliss’s spraying activities. Each of the policies at issue contains one of four forms of pollution exclusion; three of the forms, on which the parties have focused, create an exception to the exclusion — i.e., affirmatively cover — harm from pollution releases that are *1163 “sudden and accidental.” The first form (termed the “domestic insurers’ exclusion” by the district court) provides:
[This insurance does not apply to] [bjodily injury or property damage arising out of the discharge, dispersal, release or escape of smoke, vapors, soot, fumes, acids, alkal-is, toxic chemicals, liquids or gases, waste materials or other irritants, contaminants or pollutants into or upon land, the atmosphere or any watercourse or body of water, but this exclusiоn does not apply if such discharge, dispersal, release or escape is sudden and accidental.
Joint Appendix (“J.A.”) at 5067H (emphasis added). The second and third forms (the “London exclusion” and the “INA exclusion”) are identical in all relevant respects. The fourth form, contained in policies issued by defendant Travelers, replaces the “sudden and accidental” language with a requirement that the discharge of pollutants be neither “expected” nor “intended.”
In the decision under review here, the district court granted the insurers’ motion for summary judgment on claims governed by Missouri law.
Independent Petrochemical Corp. v. Aetna Casualty & Sur. Co.,
Although all parties agree that Missouri law controls, we have no ruling from the Missouri courts interpreting “sudden and accidental.” See
Independent Petrochemical Corp.,
I.
A. “Sudden and Accidental."
Charter argues, first, that the phrase “sudden and accidental” is facially ambiguous and thus, under standard principles of insurance law and specifically those of Missouri,
Peters v. Employers Mutual Casualty Co.,
1. Facial Ambiguity.
a. The Anti-redundancy Canon.
Charter says that “sudden” is ambiguous in that it may be interpreted to mean either “unexpected and unintended” (the interpretation favored by Charter) or “unexpected, unintended, and abrupt” (the interpretation favored by the insurers and adopted by the district court). In suppоrt of its position, Charter points to dictionary definitions of “sudden” that emphasize the element of unexpectedness and downplay or ignore that of abruptness. E.g.,
Webster’s Third New International Dictionary
2284 (1981) (listing, as the first definition of “sudden,” “happening without previous notice or with very brief notice: coming or occurring unexpectedly: not foreseen or prepared for”). The district court rejected Charter’s interpretation, relying heavily on the Eighth Circuit’s construction of Missouri law in
Aetna Casualty & Sur. Co. v. General Dynamics Corp.,
Under the “home circuit” rule of
Abex Corp. v. Maryland Casualty Co.,
The present appeal does not present such a case. First, the
General Dynamics
court’s determination that “accidental” includes an element of unexpectedness,
General Dynamics’s
use of the anti-redundancy canon is also consistent with Missouri caselaw. E.g.,
Brugioni v. Maryland Casualty Co.,
*1165
The application of anti-redundancy reasoning in
General Dynamics
is consistent with other eases interpreting “sudden and accidental.” As the Tenth Circuit said in concluding under Utah law that “sudden” had a meaning distinct from that of “accidental”: “Dictionaries may indicate each word has several overlapping meanings. We cannot use only the redundant definitions, however.”
Hartford Accident & Indemnity Co. v. United States Fidelity & Guaranty Co.,
Having determined that “sudden” must mean something other than “unexpected,” the
General Dynamics
court went on to hold that the term’s “plain meaning” is “abrupt.”
Further, even apart from the redundancy problem, reading “sudden” to mean only unexpected presents serious difficulties. In advocating that reading, for instance, the Supreme Court of Georgia reasoned: “[0]n reflection one realizes that, even in its popular usage, ‘sudden’ does not usually describe the duration of an event, but rather its unexpectedness: a sudden storm, a sudden turn in the road, sudden dеath.”
Claussen v. Aetna Casualty & Sur. Co.,
b. Purpose of Policy Term.
Putting canons aside, Missouri courts in interpreting insurance contracts look to the underlying commercial or legal purpose sought to be achieved by a policy term. See
Weathers v. Royal Indemnity Co.,
Of course, suddenness is only an imperfect mechanism for identifying harm that the insured neither expected nor intended. Here, the suddenness of Bliss’s discharge presumably has little if any bearing on whether the resulting harm was expected or intended by Charter. By definition, however, a proxy only approximates the underlying item of interest. The absence of a perfect fit therefore provides no basis for refusing to apply the proxy or for distorting its meaning. 2
*1167 c. Historical Interpretation.
Charter argues that
Abex
deference to
General Dynamics
is unjustified in light of the courts’ historic interpretation of “sudden and accidental” language in boiler and machinery policies, and indeed two courts have been persuaded that the language acquired an established meaning in the boiler and machinery context. See
New Castle County v. Hartford Accident & Indemnity Co.,
It seems to us that the risk tо the insurer would be the same, whether a break was instantaneous or began with a crack which developed over a period of time until the final cleavage occurred, as long as its progress was undetectible [sic]. On the other hand, the insured should not be permitted to proceed recklessly and hold the insurer hable for damage if it had been forewarned of a possible break and could have taken steps to forestall it or avoid an interruption of business resulting therefrom.
Anderson & Middleton Lumber Co. v. Lumbermen’s Mutual Casualty Co.,
2. Latent Ambiguity.
Charter argues that even if “sudden and accidental” is not facially ambiguous, the insurers’ prior claims behavior and representations made to state insurance regulators reveal a latent ambiguity in the phrase. Latent ambiguity can arise where language, clear on its face, fails to resolve an uncertainty when juxtaposed with circumstances in the world that the language is supposed to govern. See
AM Int’l, Inc. v. Graphic Management, Inc.,
Charter first points to evidence of the payment by certain (unspecified) defendants of the initial claims against Charter and its affiliates arising out of Bliss’s spraying. The insurers paid, in aggregate, $2.8 million, a tiny fraction of Charter’s ultimate liability. J.A. 999. Charter argues that thе payment of the initial claims places a practical construction on the parties’ agreement, one that the defendants are not now free to ignore. The defendants respond that the decision by an individual claims representative to pay a single claim or a small number of claims should not, without more, bind the insurer to an interpretation under which the insured is covered for all similar claims. (A fortiori, one insurer’s claims behavior should not bind other insurers.) We agree with the defendants. A contrary holding would require that an insurer, before paying modest claims such as the initial claims by Charter here, conduct an investigation in far greater depth than the amount at stake would justify, simply to avoid the risk of massive exposure down the road. Charter correctly notes that the decision to uphold coverage in
Haas
was based in part on the prior claims behavior of the insurer.
The second sort of extrinsic evidence proffered by Charter concerns representations made to insurance regulators (and contemporaneous internal memoranda) regarding the scope of the pollution exclusion. Again we assume that such evidence might in some circumstances establish a latent ambiguity in the pollution exclusion, but we find that none of the evidence proffered rises to the level of suggesting material inconsistency between the representations or internal memoranda and the policy language as interpreted in General Dynamics.
In this category Charter points first to the insurers’ representation that the newly introduced pollution exclusion merely “clarified” existing coverage. The insurers stated in various fora that because damages from pollution tended to be expected or intended and thus excluded from coverage by virtue of the threshold requirement for coverage under standard occurrence policies, the effect of the pollution exclusion was merely to “clariffy] th[e] situation so as to avoid any question of intent.” J.A. 5067F; see also J.A. 5024-5025 (testimony of David E. Kuizеnga) (interpreting insurers’ explanation of the pollution exclusion); J.A. 5069A-5069B (testimony of James C. Schmitt) (stating that a coverage-reducing exclusion would have encountered substantial regulatory resistance in Missouri in 1970). According to Charter, this evidence demonstrates that the “sudden and accidental” language in the pollution exclusion, even if clear on its face, was not interpreted or understood to impose conditions beyond the traditional “unexpected and unintended” requirement. But the addition of “clarifying” language necessarily implies some element of change; presumably some cases, whose classification was in doubt before the change, can afterwards be classified with certainty. Moreover, in the context of insurance policies, where ambiguous language is construed against the insurer, a clarification that yields any wins for the insurer (out of the set of formerly ambiguous cases) represents a slight curtailment of the former theoretically available coverage. And here the emphasis is properly on theoretical availability. The record evidence, undisputed by Charter, shows that pollution claims *1169 were far less common and far less broad in scope in the era in which the pollution exclusion was drafted than they are today. E.g., Supplemental Appendix at 414 (affidavit of Frank Ovaitt). 3 Furthermore, as we noted above, the classic image of pollution in that era was the steady emission of pollutants into the air or a stream, not the kind of ground contamination that CERCLA and рarallel developments made crucial. See, e.g., J.A. 2128, 2174, 2176 (script of speech delivered November 11, 1965 by the Secretary of the Hartford Insurance Co., entitled “Implications of Coverage for Gradual Injury or Damage” (1965)) (using, as an illustration of gradual harm, “the discharge of corrosive material into the atmosphere or water courses”). Against this backdrop, the insurers’ statement that damages from pollution tended to be expected or intended and thus exempt from coverage under standard occurrence policies seems entirely plausible. While the expansion of liability for environmental harm in subsequent decades may have greatly increased the scope of “pollution damages” and reduced the likelihood of such damages being expected or intended, these later developments cannot convert the insurers’ 1970 statements into misrepresentations.
Charter likewise fails to show how an internal statement by Aetna’s in-house counsel, expressing reluctance to concede any reduction in coverage as a result of the pollution exclusion, supports the conclusion that the insurers’ representations to regulators were deceptive. The counsel stated that Aetna did not want to concede any reduction in coverage as a result of the exclusion “because this is tantamount to admitting that all such cases are now covered, whereas some of them may not be covered.” J.A. 5060. Though the meaning is obscure, it appears quite consistent with the insurers’ position that the language change was one of clarification. Charter also points to a statement by the Aetna counsel that “[t]here may be a hue and cry because there will be no reduction in premium, despite the fact that coverage would appear to be cut back_” Id. This statement appears in a list of “industry public relations” issues related to the filing of the pollution exclusion, and it is immediately followed by the statement that Aetna did not want to concede any reduction in coverage. Charter has not explained how an industry public relations concern about coverage “appearing]” — most plausibly to insurance regulators or policyholders — to be cut back is inconsistent with thе representation of the exclusion as a “clarification” of existing coverage. Further, no premium reduction would have been likely for a linguistic change “for an exclusion where there was little or no loss experience” because of the limited scope of pollution liability at the time the exclusion was developed. Ovaitt Affidavit, Supplemental Appendix at 414.
Charter points finally to statements appearing in what it calls “insurance industry” publications, such as an item in the May 1971 issue of F.C. & S. Bulletins. See J.A. 2136, 2425-26. Without some reason to believe that any of the defendants is responsible for these statements — and Charter provides none — they appear to be only the view of some third party. Even if they provided an unequivocal reading of the рollution exception — and they don’t — Charter does not explain why we should regard them as material.
Closely related to Charter’s latent ambiguity contention is its argument that the insurers’ statements to regulators require the court to strike down the exclusion (as interpreted in
General
Dynamics) on grounds of public policy. The district court rejected Charter’s argument, relying again on
General Dynamics,
which the district court described as “implicitly rejecting]” an analogous argument explicitly made by the insured in that case.
Independent Petrochemical Corp.,
Charter has not pointed to any articulated policy of the Missouri legislature or the Missouri courts calling for judicial invalidation of contracts on the type of grounds urged by Charter, i.e., alleged misconduct of insurers before state regulators, as opposed to a substantive conflict between state public policy and a contract’s terms. It is conceivable, of course, that Missouri courts would accept such a theory. We find it unnecessary to decide whether they would as a general matter, however, because Charter has failed to establish any convincing inconsistency between the representations and the language of the pollution exclusion as interpreted in General Dynamics.
B. “Suddenness” of Bliss’s Discharge.
Because the pollution exclusion as interpreted in
General Dynamics
denies coverage unless the discharge of pollutants is abrupt, we must determine whether Bliss’s discharge of dioxin-contaminated oil satisfied this requirement. Clearly, if the discharge is defined as the aggregate of Bliss’s oil-spraying activities, then it was not abrupt; Charter concedes that the spraying took place over a period of at least two months. It argues that each spraying session, taking about 30-40 minutes, should be viewed as a distinct discharge, and that, so viewed, the discharges were abrupt. The logical consequence of this argument, however, is that spraying in, say, 30-minute increments over a two-month period with five-minute breaks between each increment would satisfy the suddenness requirement, whereas constant spraying over the same two-month period would not. We cannot conceive of any sensible basis for such a distinction. As Charter itself acknowledges, see Reply Brief at 17-18, the rationale for excluding coverage when the polluting activity is undertaken repeatedly in the course of ordinary business operations is that the resulting harm is less likely than otherwise to be unexpected and unintended. Cf.
Lumbermens Mutual Casualty Co. v. Belleville Indus. Inc.,
As noted above, suddenness is only a proxy for hаrm that is unexpected and unintended, and here Charter presumably neither expected nor intended the harm that resulted from Bliss’s spraying. Again, however, the inevitable imperfections in a proxy’s fit are no basis for refusing to apply it. Thus we conclude that Bliss’s discharge of dioxin-contaminated oil was not “sudden.”
C. Coverage under the Travelers Policies.
As we mentioned at the start, the policies issued by defendant Travelers did not contain the “sudden and accidental” language but instead preserved coverage for discharges that were neither “expected” nor “intended.” As to those policies the duration of Bliss’s spraying activity does not bar coverage. Rather, Charter should recover if the discharge of the dioxin-contaminated oil was neither expected nor intended. The district cоurt treated this requirement as identical to the “accidental” requirement in the other policies,
Independent Petrochemical Corp.,
The district court ruled that Bliss’s discharge was not accidental,
II.
There remain a few procedural matters to be cleaned up. After the parties had filed their briefs with this court, but prior to oral argument, the insurers filed a motion to strike certain exhibits submitted with Charter’s reply brief. Charter fired back with a cross-motion to strike certain affidavits submitted by the insurers to the district court after briefing on the insurers’ summary judgment motion was complete. We deferred consideration of these motions pending oral argument.
The insurers moved to strike the following material submitted by Charter: (1) deposition excerpts from unrelated litigation in other courts; (2) excerpts from insurance law treatises; (3) articles containing factual material concerning the drafting history of the pollution exclusion; and (4) a summary categorization, prepared by Charter, of affidavits submitted by the insurers to the district court.
The deposition excerpts submitted by Charter were not put before the district court on the motion for summary judgment and therefore cannot properly be invoked here. See
Frito-Lay, Inc. v. Willoughby,
As to Charter’s objections to affidavits submitted by the insurers, only the affidavit of Frank Ovaitt (Supplemental Appendix at 414) has played any role in our affirmance of the district court’s decision. We see no basis for any objection to the Ovaitt affidavit. See note 3 supra. Because we do not rely on any of the other affidavits, we need not address Charter’s objections to them.
Charter also objects to discovery rulings entered by the district court in 1993 and by a magistrate judge in 1986 and 1987. We review district court rulings on discovery matters solely for abuse of discretion,
Carey Canada, Inc. v. Columbia Casualty Co.,
The district court’s grant of summary judgment for the defendants is
Affirmed.
Notes
. The issue whether dioxin causes cancer in humans is highly controversial. See, e.g., Richard Stone, "Panel Slams EPA’s Dioxin Analysis," 268 Science 1124 (May 26, 1995) (reporting critique by the EPA's Science Advisory Board).
. Abraham, supra, at 153-55, also suggests that a requirement of sudden onset — as distinguished from a requirement of limited duration — might help to control moral hazard. His argument seems to be that a sudden onset, or "boom,” alerts all to the occurrence of the discharge and thus allows the insurer to enforce a duty to mitigate on the part of the insured. In contrast, when a discharge begins gradually it will be difficult to enforce any duty to mitigate, and that duty will be subject to moral hazard. A requirement of sudden onset might help to control this moral hazard problem. Id. We are somewhat skeptical of this analysis. First, enforcement of a *1167 duty to mitigаte would seem to require complex knowledge about a wide range of factors other than simply the onset of the discharge, such as the costs and benefits of each possible corrective measure. Second, even in terms of identifying the onset, we suspect that in many cases the insured’s failure to take action in response to a discharge that begins with a whimper rather than a bang would be due to its ignorance of the event rather than to its shirking the duty to mitigate. If the set of cases in which insureds would fail to mitigate gradually-beginning discharges of which they are aware is small, then coverage of harms resulting from such discharges would not create any significant moral hazard problem.
. In Addendum E to its Reply Brief, Charter characterizes the Ovaitt affidavit аs "not made under oath.” We are unable to explain this characterization, since the affidavit includes a notarization saying that it was sworn to before the notary. Charter also notes that Ovaitt did not join the Missouri Insurance Division until 1971, after the pollution exclusion had been filed. Reply Brief at 6 n. 5. However, this fact has no bearing on Ovaitt's ability to testify to the general tenor of pollution liability in the early 1970s.
. Rule 72(a) now provides further that "a party may not thereafter assign as error a defect in the magistrate judge's order to which objection was not timely made.” We have held that under this
*1172
language we lack jurisdiction over challenges to magistrate judges' orders to which objection was not timely made below.
CNPq-Conselho Nacional de Desenvolvimento Cientifico e Technologico v. Inter-Trade, Inc.,
