Causation — the link between an actor’s behavior and subsequent harm to another — is a vital component of a variety of legal doctrines. Requiring that a plaintiff show a causal connection between her injury and the defendant’s action satisfies the instinct that remedies for an injury should come from those who are responsible. Yet as any first-year torts student knows, pinpointing the actor(s) responsible for an injury can be factually and conceptually difficult, if not impossible. To further obfuscate clear analysis, “causation” can refer to many distinct concepts, due to different requirements in different doctrines. The result is that courts may often analyze causation in vastly differing ways, even in cases where the injury and instigating act are remarkably similar. The treatment of causation has been particularly inconsistent in environmental cases. This Note explores the disparate treatment of causation in environmental law and toxic torts. Courts can adapt the distinction between general and specific causation used in toxic tort law to clarify standing analysis and avoid prematurely deciding merits questions in environmental suits.
Environmental and toxic tort suits constitute broad, amorphous, and sometimes overlapping categories. To aid clarity, for the purposes of this Note, “toxic tort suits” refer to personal injury cases that allege a harm, generally a physical injury, due to exposure to a toxic substance.1 Toxic tort suits can cover a wide variety of toxic exposures, including those from toxic products, toxic materials in a workplace, and toxic discharges into the environment. “Environmental suits,” in contrast, refer to cases that allege an injury to plaintiffs’ interests due to a harm to the environment or a violation of an environmental statute. Environmental suits thus can be further divided into two subcategories: those asserting rights under common law, such as public nuisance, and those asserting rights created by statute.
There are many similarities between toxic tort and environmental cases; indeed, some toxic tort suits are considered environmental suits by scholars and practitioners alike.2 First, in the most archetypal version of both types of suits, the defendants have created, sold in the marketplace, or discharged into the environment an injurious substance, such as a commercial drug with previously unknown negative side effects, chemical waste leaking from a landfill,3 or a “noxious gas” that causes acid rain.4 Second, for both types of suits, the injuries or theories of causation alleged are often based on cutting-edge research, and resolving the claims often requires difficult factual or technical determinations, particularly in establishing a causal link between the offending substance and the claimed injury. Finally, even though such complex, fact-intensive determinations might seem better suited to factfinders, in both types of suits, causation is often determined by judges as a matter of law.
Despite these similarities, causation is treated quite differently in environmental suits compared to toxic tort suits, particularly in those suits where a judge finds that causation does not exist as a matter of law. In environmental suits, causation is typically analyzed as a component of Article III standing, a jurisdictional inquiry that precedes any other aspect of the case.5 In contrast, in toxic tort cases, causation is rarely addressed under the standing inquiry. Instead, dismissal of a toxic tort case for lack of causation is typically based on whether the plaintiffs have presented sufficient evidence on causation, after standing has been established (or presumed).6
This Note argues that causation in environmental law cases has been forced into jurisdictional standing analysis, even where the inquiry is more appropriate for later determination on the merits, which results in a significant and sometimes inappropriate barrier for environmental plaintiffs.7 To resolve this issue, courts can adapt toxic tort doctrine’s distinction between general and specific causation to distinguish causation questions best suited for standing analysis from causation questions better left to a factfinder. The analysis proceeds in four Parts. Part I describes how the causation inquiry functions under tort law in most states, and how toxic tort inquiries into causation differ from such inquiries in other areas of tort law. Part II discusses the difficulties with the causation prong of Article III standing in the context of environmental suits. Part III explains the similarities and differences of the causation inquiries in both types of cases, and the problems that arise out of conflating causation in standing with causation on the merits. The last Part explores solutions and proposes applying toxic tort law’s general/specific causation distinction to environmental causation inquiries. Such an approach could both mitigate the perceived inconsistencies in standing analysis in environmental suits and help ensure that fact-intensive inquiries into causation are addressed only after full discovery.
I. Toxic Torts and Causation
Toxic torts, despite their general limitation to personal injuries, span a wide variety of cases and types of exposure. Some of the more common examples include exposure to asbestos,8 pesticides,9 dioxins,10 and various pharmaceuticals, such as the miscarriage-prevention drug diethylstilbestrol (DES).11 Because of the nature of the substances generally involved, the harms due to exposure typically are not discovered until long after the exposure occurred.12 In addition, over that period of time, the injured party may have been exposed to a variety of potentially harmful substances, likely as the result of actions by a variety of different actors.13 As a result, identifying any responsible party, much less identifying all responsible parties, can be quite difficult. For toxic torts, these difficulties complicate plaintiffs’ ability to prove causation in personal injury claims.14 The standard of causation in toxic tort law is also quite contentious. Some argue that it is currently too difficult to show causation, preventing worthy victims from being compensated for their injuries.15 Indeed, causation is arguably the most difficult element to prove in toxic tort cases.16 Others, however, argue that the causation bar is too low or that relaxing the standard further would encourage frivolous lawsuits or otherwise negatively affect the court system.17 As an adaptation to those difficulties, courts in many states address causation not only by performing classical factual and proximate cause analysis, but also by separating factual causation into the categories of general and specific cause.18
Causation in tort law entails two elements: factual causation and proximate causation. For many torts, establishing factual causa-tion depends on showing that the defendant’s conduct is a but-for cause of the plaintiff’s injury.19 An alternative is “substantial factor” causation — that is, the conduct would have been sufficient to be a but-for cause, but there existed another act that also would have been a but-for cause if it had occurred separately.20 In most states, substantial factor causation is sufficient to establish factual causation.21
Historically, factual causation was established by showing but-for causation, but this approach ran into practical difficulties. For example, in a situation where two simultaneous actions could each individually suffice to create the harm, neither action is a but-for cause of the injury.22 In other situations, there may be multiple actors, but it is not clear which actor is responsible for the injury.23 If all the actors have behaved similarly, it may seem unfair that the injured party cannot obtain a remedy from any of the actors simply because each of them could point at the others to prevent any showing of causation. Such situations are not uncommon in toxic tort cases. For example, multiple but-for causes may exist in pesticide cases, where a farmworker is exposed to multiple pesticides that each could have caused the farmworker’s injuries.24 Additionally, there may be multiple indistinguishable actors in pharmaceuticals cases, where a patient has taken a drug that is produced by multiple manufacturers and it is unclear which one manufactured the doses actually purchased and used.25
As discussed above, determining factual causation can be a challenge in toxic torts.26 To aid their determinations, courts have identified two categories of factual causation: general and specific causation.27 “[G]eneral causation addresses whether products of the same nature as [the] defendant’s product are capable of causing the type of injuries alleged . . . [, while] specific causation addresses whether [the] defendant’s product more likely than not caused injuries in this particular case.”28 Most, but not all, jurisdictions require showing both aspects — but even where jurisdictions do not require both, evidence in favor of either form of causation can be probative as to establishing factual causation.29
Currently, a toxic tort plaintiff faces difficulties in establishing both general and specific factual causation. For general causation, it may be difficult to establish that a particular substance can cause a particular malady. This uncertainty may be due to ongoing debate among researchers, or simply the time it takes for such studies to be completed. One unfortunate side effect is that the earliest claimants for a particular type of toxic exposure may well find it difficult to establish general causation simply because the medical science has not yet caught up to claimants’ personal experiences.30
For specific causation, as in the multiple-emitter environmental cases described above, it may be impossible in toxic tort cases to determine which specific entity is responsible for the exposure that led to the plaintiffs’ harms.31 The difficulty in traceability may be due to the fungibility of the toxin, the length of time between exposure and medical consequences, or other issues. For example, a variety of pharmaceutical companies produced the drug DES as a generic product. DES turned out to cause cancer and other medical complications in the daughters of women who took the drug, so the medical consequences necessarily did not become apparent until decades later.32 In addition, some jurisdictions require showing that exposure to other substances is likely not responsible for the alleged injury,33 which can be difficult when a plaintiff has been exposed to multiple toxic substances. For example, asbestos is known to increase the risks of, among other things, lung cancer. However, those who have contracted lung cancer subsequent to being exposed to other airborne toxins, such as those found in cigarette smoke, may have trouble establishing that asbestos is a significant contributor, much less that smoking is likely not responsible.34 Even where the responsible toxic substance can be pinpointed, it is often medically unclear how much effect a particular exposure has had on an injury. For example, the medical evidence may still be unsettled, or it may be technically or ethically impossible to quantitate the health effects of a toxin in humans. Courts often rely on expert opinions to aid their determinations of factual questions relating to causation, but that creates additional epistemic problems in determining which experts and what testimony to allow.35
The circumstances of toxic tort cases often create difficult questions of causation, particularly factual causation, which courts often address in their merits inquiry at trial. In contrast, in environmental law cases, similarly complex questions of causation are determined before trial, as discussed below.
II. Environmental Law and Standing
Modern environmental law cases may arise from common law or from statutory authorizations.36 The earliest environmental suits were based in common law, particularly public nuisance law.37 More recently, common law environmental cases have mostly but not entirely been supplanted by cases arising from environmental statutes and regulations.38 The major statutes governing environmental law were enacted or significantly amended between 1970 and 1980, with subsequent amendments passed in the decades since.39 The broad language of the environmental statutory “canon” created a range of new rights and causes of action based on theories of environmental harm, which appears to have triggered judicial concern over whether Congress overstepped Article III’s limitations on standing.40
Courts have derived standing doctrine from Article III’s requirement of a case or controversy.41 Despite this relatively clear basis for the standing requirement, standing doctrine is a controversial topic and has been criticized as “incoherent” or worse.42 Some have argued that Article III standing is merely an excuse for courts to avoid reaching the merits on cases they are unwilling or unable to decide, or that courts will sometimes turn a blind eye to standing when they wish to reach the merits.43 This section describes the elements of Article III standing, with particular emphasis on the standards for showing causation in environmental suits.
Article III standing comprises three components: injury in fact, causation, and redressability.44 The injury must be both “concrete and particularized”45 and “actual or imminent.”46 An injury may be concrete even if the harm is not physical or economic, such as an injury to one’s interest in viewing endangered animals.47
Redressability requires that the court find it likely (and not “merely ‘speculative’”) that the injury would be redressed by a favorable decision.48 Redressability often ties in with causation, as a finding of lack of causation typically results in a finding of no redressability as well.49 And in “procedural rights” cases — where the claimed injury is an agency’s failure to fulfill a statutorily mandated procedure (such as a rulemaking or an administrative hearing) — the redressability requirement may be fulfilled if the court’s decision for the plaintiff would cause the desired procedure to be performed, even if the outcome of the procedure may go against the plaintiff’s goals.50 This has resulted in one of many gray areas in standing doctrine: whether procedural rights are substantially different from other types of rights for the purposes of standing.51
For the causation prong, courts generally find causation when the injury is “fairly traceable” to the defendant’s conduct.52 However, the standard for what is considered fairly traceable is unclear. In some cases, a but-for causal connection has been considered sufficient for standing purposes.53 In others, the Court has applied a causal nexus test.54 In addition, the unclear role of state sovereignty in standing may extend to the causation prong.55
The causation inquiry in Article III standing has been criticized as “uncertain in application and unpredictable in result.”56 However, causation generally has been easier to establish when the alleged injury is perceived to be a direct result of the defendant’s action,57 while cases that claim a harm based on a defendant’s failure to engage with a third party are more likely to fail on the causation prong.58 Additionally, Congress may be able to define new chains of causation that suffice to establish standing,59 including by creating procedural rights.60
In some environmental cases, as in some toxic tort cases, demonstrating but-for causation can be nearly impossible, even when the plaintiff has undoubtedly been injured. In global warming and other similar cases, multiple entities may emit a pollutant with no feasible means to determine whether any individual entity’s emissions created the complained-of injury. This may be true even when a court has accepted that the result of the accumulated emissions has created the injury. In such cases, the Court has considered whether the defendants’ conduct has made a “meaningful contribution” to the pollution.61 However, the extent of what suffices to show a meaningful contribution remains unclear.62
There has been substantial disagreement in the courts and among commentators about the degree of inquiry required in the standing phase of an environmental claim. In particular, it is difficult to determine when adjudication of a factual dispute over causation should occur, in the standing phase or afterwards on the merits, with some scholars arguing that current standing doctrine injects the “merits issues into a supposedly jurisdictional determination.”63 One example of this dispute occured in Comer v. Murphy Oil USA,64 in which a class of Mississippi residents and landowners sued under various common law doctrines, including public nuisance, claiming injuries from greenhouse gas (GHG) emissions that exacerbated the effects of Hurricane Katrina.65 The Fifth Circuit held that the challenge to jurisdiction involved questions that ought to be resolved at the merits stage,66 but the decision was vacated upon en banc review.67 Generally, however, courts have incorporated factual inquiries at the standing stage for determining causation.68 In fact, in one case relating to the Clean Water Act, the Third Circuit vacated a judgment because the plaintiffs did not contradict a defendant’s expert who testified during the merits phase that the permit violations had no observable impact.69
The causation prong of the Article III standing inquiry is heavily fact dependent. In its discussion of causation in Connecticut v. American Electric Power Co.70 (AEP), the Second Circuit concluded that the five defendants’ emissions sufficiently contributed to the plaintiffs’ injuries, noting that they were the largest utility emitters of carbon dioxide in the United States.71 As a result, the court found that the causation element was fulfilled.72 In contrast, in the most recent major case on causation, Washington Environmental Council v. Bellon73 (WEC), the Ninth Circuit held that environmental group plaintiffs did not have standing to sue to compel state regulation of GHG emissions from oil refineries.74 The court found that the causal chain between the state’s lack of controls and the claimed injuries “consists of a series of links strung together by conclusory, generalized statements of ‘contribution,’ without any plausible scientific or other evidentiary basis that the refineries’ emissions are the source of their injuries.”75 The court noted that causation in GHG cases was particularly difficult, due to the global effect of GHG emissions and the localized nature of harms.76 Because the plaintiffs had not alleged that the oil refineries had emitted a significant proportion of national or global GHG emissions, the court found that there was insufficient evidence that the emissions were contributing significantly to climate change.77 The plaintiffs did argue that the emissions constituted a significant percentage of state emissions, but the court noted that this was a far smaller amount than that emitted by the parties at issue in AEP.78 If the reasoning in WEC is followed by other courts, it could preclude nearly all state court suits, which typically involve only a small percentage of national emissions.79 The causation analysis in both AEP and WEC considered the sufficiency of facts to show causation — namely whether the amount of GHG emissions was “enough” to count as causing the plaintiffs’ harms.
Factual inquiries into causation at the standing stage are not limited to climate change cases. While recent Supreme Court inquiries into standing have been predominantly about GHGs, lower courts consistently make factual inquiries in other areas of environmental law.80
III. Criticizing the Differences in Causation Inquiries
Much scholarship has criticized how standing doctrine is applied, both generally as well as specifically in the context of environmental law. In toxic tort scholarship, there has been vigorous discussion of the standards for causation and the difficulty (or ease) of establishing both factual and legal causation.81 And others have examined the historical basis of modern environmental law in tort law, as well as how tort law might still apply in modern environmental law, much of which is now governed by statute.82 Still, despite similarities in the causation inquiries in these two types of cases, surprisingly little has been written on the disjunction between causation inquiries for the purposes of jurisdiction and for merit determinations in tort law.
Despite being considered at different stages in the two different types of cases, causation in both environmental and toxic tort cases often requires complex factual determinations. Such factual determinations can occur before the merits stage — in jurisdictional hearings resembling trials — and are treated as factual determinations on appellate review,83 even though the findings are used to determine standing, a question of law. There are also many similarities between the technical methods available to support causation findings in both toxic torts and environmental suits. In toxic tort cases, findings of causation typically rely on epidemiological evidence, which relies heavily on statistical analyses and mathematical or computer modeling to make probabilistic determinations of risk and contribution.84 Because of the complexity of human health and the great difficulty in showing direct medical causation (rather than correlation), it is typically impossible to demonstrate that an individual’s health condition is directly and solely caused by any particular toxin.85 In environmental cases, there are a variety of fields that might be called on to support a causal nexus, depending on the type of claim.86 Many of these fields, including meteorology, hydrology, and ecology, also rely heavily on statistical and modeling methods, and these fields also tend to be able to only predict risks based on observed correlations.87
Despite these similarities, causation is considered more often and in more detail at the standing phase in environmental suits, but it is reserved primarily for merits determinations in tort suits. There are rationales for this divergence based on doctrinal, structural, or policy arguments, but they ultimately cannot justify the disparity. The first argument is that, while there might appear to be a divergence in practice, there is no actual doctrinal difference in the standards for causation in standing for environmental and toxic tort cases; any difference in outcome is due simply to the nature of environmental law cases. Environmental suits often are rooted in statutes or administrative regulations, which may provide broader bases for claims than are available at common law. Such environmental suits are thus more likely to fail at the first, lower causation requirement during standing, while toxic tort cases typically are clear enough to overcome standing issues without need for discussion. However, even if environmental cases are inherently more likely to fail on standing, there are several signs that this cannot be the sole reason for the difference. Environmental cases that do not arise under statute often fail at the standing stage as well — environmental tort cases, particularly public nuisance cases, also tend to require strong factual support for standing.88 Of course, public nuisance is not quite as traditional a tort as other torts, and may raise significant standing problems simply based on the more generalized claims of harm it encompasses. However, the same can be said of some toxic tort suits, particularly those claiming injuries attributed to exposure to a toxic discharge. Yet toxic tort claims rarely face the same standing barriers as environmental claims.89
The second argument is structural. Article III’s case-or-controversy requirement is said to enforce the separation of powers and ensure that there is “proper adversarial presentation” to support effective adjudication.90 Standing requirements provide a safeguard against congressional and judicial overreach, both by limiting Congress’s power to establish new causes of action and by limiting the courts’ authority to adjudicate issues.91 However, too high a standing barrier also cuts against the structural limits of the Constitution. A court that dismisses claims under too narrow a view of standing unduly limits congressional discretion in defining new injuries and causes of action.92 In addition, an overly high bar for standing may prematurely trigger or block detailed technical review that is better left to the merits stage of a trial.93
Finally, judicial policy may be playing a role in decisions to deny standing to environmental suits. Courts may be using standing for a gatekeeping function, out of concern that allowing environmental suits to proceed based on broader views of standing would overwhelm the courts or allow frivolous lawsuits intended to harass or delay others.94 But these are prudential considerations. If a court is concerned about these issues, it should analyze them directly rather than treating them as constitutional issues, which cannot be overruled by Congress.
In addition, the highly detailed factual analysis that accompanies some standing inquiries may be inappropriate at such an early stage of trial. There are several problems that arise from overreliance on factual determinations in issues of standing. For example, judges are not equipped to handle highly technical factual issues unaided.95 Also, in areas of ongoing research, like the effects of various pollutants on human health and welfare, later scientific and technical developments could change the causation analysis. Because such new data or models are rarely universally adopted soon after discovery, but rather only slowly reach scientific consensus, judges and juries would benefit from a full factfinding process, with Daubert hearings and other supporting procedures to ensure that the facts presented to the court reflect scientific methods and expertise as accurately as the judicial process allows.
If both tort merits-stage and environmental standing causation inquiries are being resolved by judges as questions of law, and resolving both types of inquiries depends on the same judges considering similar technical information, why does it matter that the inquiries happen at different stages of the proceedings? First, requiring the same degree of scrutiny at the standing and merits phases is inconsistent with doctrine. Second, there are a variety of practical considerations that support leaving heavily fact-dependent questions to the merits phase.
Standing is intended to be a threshold inquiry. By considering both general and specific causation for deciding standing for environmental suits but not in similar toxic tort suits, courts have established an inconsistently high barrier for plaintiffs in environmental suits, limiting access to judicial process. Ironically, the federal statutes creating the possibility of environmental citizen suits, which are now heavily scrutinized under Article III standing analysis, were passed in response to the consensus that the common law was insufficiently protective and the tests for liability too strict for plaintiffs.96 In fact, passage of the environmental statutes inspired those drafting the Second Restatement of Torts to relax some tort requirements.97 The greater burden to show standing for citizen suits under statutes compared to common law thus likely contradicts the intent of the Congresses that passed those statutes. Further, conducting the entire causation inquiry within the standing analysis places an inappropriately high burden on judges to resolve factual questions at an early stage of trial, instead of leaving those determinations to the designated factfinder after a full hearing.
If determining jurisdiction often requires considering the merits of the case, why should it matter that current standing doctrine sometimes results in court analyses that overinclude factual determinations in standing? Beyond the value of judicial restraint in not unnecessarily restricting Congress’s determinations of when to provide remedies not available at common law, there are several nondoctrinal reasons why fact-based determinations should be left to the merits phases as much as possible. While it would be inefficient to leave jurisdictional questions to a jury or other factfinders because doing so would interfere with the gatekeeping function of limited standing, it is also inefficient to require inexpert judges to weigh dueling statements of expert witnesses when the asserted technical information is not necessary to determine whether the parties have standing. There are also broader considerations of fairness, or at least perceived fairness. Given the typically more truncated nature of jurisdictional proceedings, both in terms of the hearing process and the degree of discussion in resulting decisions, jurisdictional proceedings tend to provide a less complete airing of factual disputes. And given the political concerns over many environmental suits, including the perception that standing determinations in environmental suits are often politically motivated,98 reserving as much of the factual dispute as possible to the merits phase would incent more detailed examination of the issues at stake, and perhaps allow more environmental suits to proceed to the merits.
IV. Incorporating Toxic Tort Causation into Environmental Standing
Shifting some of the factual analysis for establishing causation out of standing analysis would help reduce the bias against finding standing in environmental suits. However, the difficulty is in determining which aspects of the causation factfinding can be moved from the standing inquiry of environmental suits to the merits phase, without further muddling standing doctrine.
Toxic tort doctrine may serve as a valuable guide to reforming environmental standing analysis. Courts considering difficult questions of causation may be able to distinguish questions of general and specific causation, requiring proof of only the former at the standing stage. This Note is not the first to argue that aspects of toxic tort law can be used to clarify issues in environmental law; but prior work has focused on other aspects of such cases.99 The general/specific distinction is readily made by nontechnical decisionmakers and may lead to more coherent doctrine and fairer access to merits review for environmental plaintiffs.
To parallel the terms’ use in toxic tort cases, then, this Note defines general causation in environmental cases as showing that the actions of the defendant are capable of causing the plaintiff’s alleged injuries, and specific causation as showing whether the defendant’s conduct was a substantial contributor to the injuries in the particular case. With general and specific causation defined in this manner, environmental claimants would be able to show the causation prong of standing if they presented sufficient evidence that the defendant’s pollution is of a kind capable of creating their alleged injury. For a fisher, it would be sufficient to show that an upstream discharge contains toxins capable of killing fish, reserving for the merits whether the amount of discharge was sufficient to harm the fish in question. For a coastal landowner, it would be sufficient to show that a facility is emitting pollutants capable of contributing to climate change, reserving for the merits whether damage to the landowner’s property is due to climate change and whether the amount of the facility’s emissions is a significant contribution. And so on. Requiring general causation alone at the standing stage would maintain the basic tripartite structure of standing analysis, and a general causation requirement would be sufficient to exclude a wide variety of problematic cases, including those where there is insufficient scientific evidence that the action is injurious in the way claimed by the plaintiff.
Addressing only general causation in the causation prong of standing returns that prong to its initial gatekeeping role of ensuring that the courts hear only cases that arise out of a case or controversy. A finding of general causation — that the action could create the type of harm suffered by the plaintiff — suggests that there is at least a possibility that the action did cause the harm, and thus, whether the action specifically caused the harm is a controversy suitable for adjudication. As with other areas of law, an affirmative finding on general causation alone would not always suffice to reach the merits: the suit must also establish the other prongs of standing.100 Further, if a court recognizes that a claimant has presented no facts supporting specific causation and cannot establish that the alleged injury resulted from the defendant’s actions, the court may still dismiss the case on summary judgment,101 which parallels how this issue is resolved in toxic tort cases.102 This approach is a more logical way to resolve clear factual outcomes without denying jurisdiction altogether and allows courts to leave more difficult (and thus harder to establish) questions of fact to the factfinding stage.
This solution would not be entirely inconsistent with existing case law. Some decisions already implicitly recognize a distinction between general and specific causation, though they address both forms of causation under standing analysis. In WEC, the court appeared to accept the State’s argument, supported by expert declaration, that “it is not possible to quantify a causal link” between the GHG emissions of any individual refinery and global climate change.103 And even if there were a link between the emissions and environmental harm, the court argued, that would not suffice to show a causal link with the plaintiffs’ injuries.104 While the former argument may be dicta,105 it suggests that the Ninth Circuit was concerned not only with whether the plaintiffs had established a specific causal link to the claimed injuries, but also with a general causal link between the emissions and climate change. Moreover, the Third Circuit in Powell Duffryn seemed to find general causation sufficient when it explained that, under the Clean Water Act, causation can be established by showing that the defendant discharged more than the permitted amount of pollutant “into a waterway in which the plaintiffs have an interest . . . [and] this pollutant causes or contributes to the kinds of injuries alleged by the plaintiffs.”106
The Supreme Court, too, has sometimes appeared to distinguish between general and specific causation without explicitly identifying that distinction. For example, in Friends of the Earth, Inc. v. Laidlaw Environmental Services (TOC), Inc.,107 the Court’s injury analysis overlapped with the causation inquiry when it found that the plaintiffs had sufficiently alleged cognizable injuries to satisfy that prong of standing for its claim for injunctive relief.108 The Court observed that “[t]he relevant showing for purposes of Article III standing . . . is not injury to the environment but injury to the plaintiff.”109 To ultimately prevail on claims based on the latter type of injury, the plaintiffs would need to show that the defendants’ discharges into the river caused the plaintiffs’ specific behavior, not merely the more general showing that some discharges could cause some people to stop using the river. The Court noted that Friends of the Earth had provided reasonable support, beyond that of “general averments,” sufficient to support their claims at the jurisdictional stage.110 The Court, however, did not define a more specific standard for the evidentiary requirements to establish standing.
There are several reasons why courts may remain reluctant to leave some aspects of causation for later proceedings in the case. While there are some valid prudential and doctrinal objections to the general/specific distinction described here, these objections ultimately are not persuasive.
One reason may simply be history, both in terms of overt limits in the form of precedent and in the limits of path dependence.111 Courts have long entertained detailed inquiries into causation under Article III standing, starting with early public nuisance law claims, and this practice does not appear to have been widely challenged in courts, even as academics have debated the merits of existing standards for standing. The continued overuse of causation inquiries in environmental cases may be attributable, at least in part, to the reluctance of litigators to raise arguments that might challenge this doctrine.112
Courts may also be concerned that relaxing the factual inquiry will weaken standing’s role as a structural limit on judicial overreach and jeopardize both the separation of powers and the adversary requirements that aid effective adjudication. However, it seems more likely that recognizing when a factual question is better left to the merits would better enforce both the separation of powers and the adverseness requirement. As noted above, too high a standing barrier also cuts against the separation of powers by allowing courts to limit Congress’s power to create new causes of action. And adversarial presentation of difficult questions of fact would be more complete if the parties are given the opportunity to be heard at the merits stage.
Another concern is whether analyzing causation in this way would open the floodgates to massive numbers of environmental suits that are currently resolved on standing grounds. This is particularly relevant to climate change suits, given the extremely large number of facilities that emit GHGs, especially if such claims can continue to be brought under common law.113 However, just because plaintiffs can show general causation does not mean that they have standing, or that they would prevail at trial. For example, plaintiffs suing a relatively small emitter would still have trouble showing that any harm to their property would be redressed by a favorable court decision.114 The difference is that those nonconstitutional considerations would be more clearly stated as such, allowing Congress to step in if it disagrees.
And even if environmental suits were to flood courts because standing restrictions (including prudential limitations) were relaxed, the caseload may not be entirely unmanageable. Toxic tort cases are widely acknowledged to have produced such a flood, which courts have established procedures to handle. It is not clear why the many toxic tort plaintiffs should have greater access to the courts than environmental plaintiffs, at least where both are requesting similar damages-based remedies.
It may also be true that many of the cases that survive the standing inquiry by establishing only general causation will fail on the merits when they come up short on specific causation. As noted by others, it is extremely difficult to show specific causation — that an individual emitter’s emissions created a particular harm.115 Given this difficulty, then, what value is there to extending the trial and burdening courts by moving to merits phases that are (likely) doomed to fail? The first reason is the ideal that those with valid claims are entitled to their day in court. Further, truly hopeless cases may still be dismissed on summary judgment, upon a party’s showing that its adversary cannot overcome the burden of proof before any reasonable factfinder. But the relatively high standard required for summary judgment reduces judicial discretion and thus the risk that conscious or unconscious biases will influence a case’s dismissal. This, in turn, allows dismissal where the facts clearly dictate a specific result while still granting a full hearing to more borderline cases. This structure parallels how other areas of law resolve cases, including toxic tort law, and may help resolve some of the underlying confusion in environmental standing doctrine.
Conclusion
The conflation between causation in standing law and causation as an element of tort law has created a justiciability barrier in environmental law, under which judges find themselves considering the full extent of causation as a part of the standing inquiry. Such an exhaustive examination of causation under an ostensibly jurisdictional consideration places an undue burden both on judges, who must consider factual and technical findings without the benefit of full briefing and argument, and on plaintiffs, who must establish full causation in their initial filings. Given the similarities between toxic tort cases and environmental suits, reserving questions of specific causation for later determination would likely help relieve the burden on both courts and claimants without serious injury to courts’ dockets and would result in more consistent and equitable hearings for those pursuing environmental claims.