Stephen A. Higginson, Circuit Judge

Danny Dustin Russell, Russell Law Firm, L.L.C., Baton Rouge, LA, James D. McMichael, Attorney, Spencer & Taylor, P.L.C., Lexington, VA, for Plaintiff—Appellant.

James Conner Percy, Esq., Jones Walker, L.L.P., Baton Rouge, LA, Brett S. Venn, Jones Walker, L.L.P., New Orleans, LA, for Defendant—Appellee Denka Performance Elastomer, L.L.C.

Deborah DeRoche Kuchler, Joshua James Doguet, Sarah Elizabeth Iiams, Kuchler Polk Weiner, L.L.C., New Orleans, LA, Bradley Weidenhammer, Kirkland & Ellis, L.L.P., Chicago, IL, for Defendant—Appellee E I DuPont de Nemours & Company.

W. L. West, Attorney, Roedel, Parsons, Blache, Fontana, Piontek & Pisano, A.L.C., Baton Rouge, LA, for Defendant—Appellee State of Louisiana.

Patrick B. McIntire, Lawrence E. Marino, Oats & Marino, Lafayette, LA, for Defendant—Appellee State of Louisiana.

Before Haynes, Higginson, and Oldham, Circuit Judges.

Stephen A. Higginson, Circuit Judge:

In this environmental tort case, Juanea Butler alleges that neoprene production from the Pontchartrain Works Facility exposed residents of St. John the Baptist Parish, Louisiana, to unsafe levels of chloroprene, which she contends may result in a myriad of adverse health conditions including an elevated risk of cancer. Butler sued Denka Performance Elastomer and DuPont—the current and former owners of the facility—as well as the Louisiana Departments of Health ("DOH") and Environmental Quality ("DEQ") in state court seeking class certification, damages, and injunctive relief for various state tort claims.

Following removal, the district court denied Butler's motion to remand to state court; granted each of the defendants' motions to dismiss because Butler's claims were either time-barred or failed to state a plausible claim; denied in part Butler's motion for leave to amend as futile; and dismissed the amended petition for failure to state a claim. Butler appeals each ruling.

I.

DuPont owned and operated the Pontchartrain Works Facility ("PWF") from 1969 until 2015, when DuPont sold the plant to Denka. For decades, it is alleged, the plant has emitted unsafe levels of chloroprene into the air, exposing nearby residents in the vicinity to adverse health effects. Though DuPont sold the neoprene manufacturing facilities of the PWF to Denka, it retained ownership of the underlying land and buildings.

On June 5, 2018, Butler filed her initial class action petition in Louisiana state court. She complains only of the chloroprene released as a result of the facility's neoprene production, and both the PWF's owners and the state's alleged failure to regulate those emissions.

Butler acknowledges that she is not the first to complain about these chloroprene emissions. The district court, accepting as true as it must the allegations in Butler's complaint and undisputed by the parties on appeal, summarized the relevant background as follows:

In December 2015, the Environmental Protection Agency ("EPA") released a screening-level National Air Toxics Assessment ("NATA"), and classified chloroprene as a likely human carcinogen. EPA's NATA evaluation suggested an acceptable risk exposure threshold for chloroprene: 0.2 µg/m3; that is, chloroprene emissions should stay below .2 micrograms per cubic meter to comply with the limit of acceptable risk threshold (which is a risk of 100 in one million people).

The EPA held its first Parish community meeting to discuss the potential chloroprene emission issues on July 7, 2016. At that meeting, a DOH representative advised that children should not breathe chloroprene. In August of 2016, Denka began 24-hour air sampling every six days. Samples collected at five sampling sites are and continue to exceed the 0.2 µg/m3 threshold. According to Denka's own sampling numbers for chloroprene concentrations, the average chloroprene concentration across all sampling sites from August 2016 to March 2017 has ranged from 4.08 µg/m3 to 6.65 µg/m3.

The EPA has noted that, in addition to the high risk of cancer from exposure to chloroprene, symptoms include: headache, irritability, dizziness, insomnia, fatigue, respiratory irritation, cardiac palpitations, chest pains, nausea, gastrointestinal disorders, dermatitis, temporary hair loss, conjunctivitis, and corneal necrosis.

The EPA has further detailed that acute exposure may: damage the liver, kidneys, and lungs; affect the circulatory system and immune system; depress the central nervous system; irritate the skin and mucous membranes; and cause dermatitis and respiratory difficulties in humans.

On October 7, 2016, Denka submitted modeling results for chloroprene concentrations surrounding the PWF to the Louisiana Department of Environmental Quality ("DEQ") for the period of 2011 through 2015, showing concentrations well above the 0.2 µg/m3 threshold. At a meeting on December 8, 2016, DEQ Secretary Chuck Brown dismissed those expressing concern about the chloroprene concentrations as "fearmongerers" and said "forget about 0.2[µg/m3]."

The EPA's National Enforcement Investigation Center ("NEIC") conducted a Clean Air Act ("CAA") inspection of the Pontchartrain Works facility in June

2016. A copy of the redacted inspection report from the EPA's CAA inspection was publicized on April 3, 2017. The NEIC inspection report revealed various areas of non-compliance by both DuPont and Denka in their operation of the facility, including failure to adhere to monitoring, recordkeeping, and reporting requirements for the chloroprene vent condenser; failure to replace leaking valves; failure to include appropriate emissions factors in air permit application materials; and failure to institute appropriate emissions controls for the chloroprene Group I storage tank.

Butler II , 2019 WL 1160814, at *1–2.

Butler herself is a resident of LaPlace, Louisiana, in St. John the Baptist Parish. Since 1998, she has resided and worked within 5.5 miles of the PWF. Butler alleges that DuPont and Denka have emitted, and continue to emit, chloroprene at levels resulting in concentrations exceeding the upper limit of acceptable risk. Specifically, she alleged in paragraph 24 of her initial complaint:

Due to the Plaintiff's exposure to the chloroprene emissions, she has experienced symptoms attributable to exposure of said chemical. Since April 2012 until current date, the Plaintiff has continually sought medical attention for the following conditions: acute bronchitis ; coughing; throat irritation; redness and swelling; nasal blockage, congestion, and sneezing; sinusitis and nasal polyps; exacerbation of preexisting asthma ; shortness of breath; wheezing; rhinosinusitis; thyroid enlargement ; cardiac problems; nausea; vomiting; headaches; fatigue; epistaxis (nose bleeds); anxiety; depression; insomnia; and temporary hair loss.

Butler also seeks to represent a putative class on behalf of:

(1) Those persons who, at any time from January 1, 2011 through the present, have lived, worked, attended school, and/or actually resided within a geographical boundary of St. John the Baptist Parish ...; and

(2) who experienced one or more of the following physical symptoms: headaches; sinus problems; dizziness; insomnia; trouble breathing; respiratory irritation, or other respiratory problems; chest pains; acute cardiac palpitations; acute gastrointestinal disorder ; acute bronchitis ; acute onset of asthma ; exacerbation of pre- existing asthma ; fatigue; nausea; skin rash; temporary hair loss; chronic coughing; chronic nasal discharge; chronic cardiovascular disorder ; chronic throat irritation; chronic eye irritation; chronic thyroid disorder; anxiety; and depression, resulting from their exposure to chloroprene or other chemical substance released from the Pontchartrain Works Facility.

Butler asserts various state tort claims against each of the defendants, and seeks class certification, damages, declaratory relief, and injunctive relief including an abatement of chloroprene releases from the PWF.

The district court ultimately dismissed Butler's claims against DuPont and DOH as prescribed by Louisiana's one-year limitations period, reversed in part the magistrate judge's order granting leave to add strict liability claims against DuPont and dismissed those claims as futile, and dismissed the remaining continuing tort claims against Denka for failure to state a plausible claim. Judgment was entered in favor of the defendants on June 4, 2020, and this appeal timely followed.

II.

Butler first challenges the district court's denial of her motion to remand the case to state court, which we review de novo. Waste Mgmt., Inc. v. AIG Specialty Ins. Co. , 974 F.3d 528, 532 (5th Cir. 2020).

Denka and DuPont timely removed the case to federal court under the Class Action Fairness Act, 28 U.S.C. § 1332(d), and the district court concluded that minimal diversity existed between Butler, a Louisiana citizen, and DuPont, a Delaware citizen based on its state of incorporation and the location of its corporate headquarters. On appeal, Butler argues that the district court lacked subject matter jurisdiction and that the state agency defendants are immune from suit in federal court. She primarily asserts that at the time of removal, DOH and DEQ had not waived immunity, and alternatively that their post-removal waiver was not authorized by the state legislature.

While Butler's primary challenge is based on sovereign immunity, her premise that she could not file this suit in federal court in the first instance misunderstands CAFA. CAFA significantly expanded federal diversity jurisdiction over interstate class action claims. Contrary to Butler's assertions, CAFA expanded district courts' "original jurisdiction" to include "any civil action in which the matter in controversy exceeds the sum or value of $5,000,000, ... and is a class action in which[ ] any member of a class of plaintiffs is a citizen of a State different from any defendant." 28 U.S.C. § 1332(d)(2)(A).

As the district court concluded, CAFA's "minimal diversity" requirement is satisfied because Butler is a resident and citizen of Louisiana, and DuPont is a citizen of Delaware. See In re Katrina Canal Litig. Breaches , 524 F.3d 700, 705 (5th Cir. 2008) ; 28 U.S.C. § 1332(d)(2)(A). It is true that even under CAFA, "a state is not a citizen" for diversity purposes. In re Katrina Canal Litig. , 524 F.3d at 706. However, a state's presence does not affect CAFA's minimal—rather than complete—diversity requirement. See id.

Butler next contends that removal was improper because the state defendants had not waived their sovereign immunity at the time of removal. Not so. CAFA permits removal by "any defendant without the consent of all defendants." 28 U.S.C. § 1453(b) (emphasis added); cf. 28 U.S.C. § 1446(b)(2)(A) (requiring that "all defendants who have been properly joined and served must join in or consent to the removal of the action" under § 1441(a)). This rule allows defendants to remove a case to federal court without first obtaining consent—and therefore waiver of sovereign immunity—from any joined state defendants, which is what occurred here. While it is true that under CAFA, "a state may find itself in a case removed to federal court without having joined in the removal," this procedure does not itself infringe the state's sovereign immunity because the "state, having taken no affirmative act, has not waived immunity and can still assert it." Frazier v. Pioneer Ams. LLC , 455 F.3d 542, 547 (5th Cir. 2006) (citing Lapides v. Bd. of Regents of Univ. Sys. of Ga. , 535 U.S. 613, 616, 122 S.Ct. 1640, 152 L.Ed.2d 806 (2002) ). Consequently, "CAFA, like other statutes, provides jurisdiction over cases in which states may, if they choose, be defendants, thus respecting state dignity interests." Id. ; accord In re Katrina Canal Litig. , 524 F.3d at 706 (holding that CAFA's expanded jurisdiction "does not tax the [state's] immunity," even when the state was involuntarily removed to federal court).

Butler further argues that removal was barred by the Eleventh Amendment, which grants states (and qualifying state agencies) immunity from suits brought by citizens in federal court. Lapides , 535 U.S. at 616, 122 S.Ct. 1640 (citing Hans v. Louisiana , 134 U.S. 1, 10 S.Ct. 504, 33 L.Ed. 842 (1890) ). However, it is well established that states can waive this immunity. Id. at 618, 122 S.Ct. 1640 ("A State remains free to waive its Eleventh Amendment immunity from suit in a federal court."). A state's voluntary appearance in federal court, including through removal, constitutes such waiver. Id. at 619–20, 122 S.Ct. 1640. Such a waiver is precisely what occurred here: DEQ and DOH—both represented by the state's attorney general—expressly waived their Eleventh Amendment immunity in opposing Butler's motion to remand.

Notwithstanding this express consent, Butler argues that Louisiana has categorically rejected any waiver of its sovereign immunity, and that neither the DEQ, DOH, nor the attorney general has authority to waive sovereign immunity or consent to federal court jurisdiction. Butler relies on Louisiana Revised Statutes section 13:5106(A), which states: "No suit against the state or a state agency or political subdivision shall be instituted in any court other than a Louisiana state court."

Butler's arguments are unavailing. To start, we have previously interpreted section 13:5106(A) narrowly as recognizing Louisiana's waiver of "its immunity in state, but not federal, court." Frazier , 455 F.3d at 547.

Moreover, the Supreme Court rejected a nearly identical argument by the State of Georgia in Lapides v. Board of Regents of the University System of Georgia . In that case, Georgia's attorney general consented to removal of a professor's lawsuit for state and federal claims against the Georgia state university system and university officials. Lapides , 535 U.S. at 616, 622, 122 S.Ct. 1640. Following removal, Georgia sought to invoke its sovereign immunity to dismiss the claims. Id. at 616–17, 122 S.Ct. 1640. The Supreme Court held that Georgia's voluntary invocation of federal jurisdiction by consenting to removal constituted waiver. Id. at 620–24, 122 S.Ct. 1640. In doing so, the Court rejected Georgia's argument that the attorney general did not have statutory authority to "waive the State's Eleventh Amendment immunity. . . even after it removed its case to federal court[.]" Id. at 621–22, 122 S.Ct. 1640. The Court emphasized that "[a] rule of federal law that finds waiver through a state attorney general's invocation of federal-court jurisdiction avoids inconsistency and unfairness," as opposed to a rule that "denies waiver despite the state attorney general's state-authorized litigating decision." Id. at 623, 122 S.Ct. 1640. Lapides likewise controls here.

Accordingly, we agree with the district court that removal was proper pursuant to CAFA, and the state agencies have consented to federal jurisdiction thereby waiving any sovereign immunity in this case.

III.

Satisfied of our jurisdiction, we turn to the merits. We review the district court's dismissal for failure to state a claim de novo, "applying the same standard applied by the district court." Masel v. Villarreal , 924 F.3d 734, 742–43 (5th Cir. 2019), as revised (June 6, 2019). A denial of a motion to amend the complaint is reviewed for abuse of discretion, but when the denial is based on the futility of amendment for failure to state a claim upon which relief could be granted, as here, we review that denial de novo under the same standards as a dismissal under Rule 12(b)(6). Villarreal v. Wells Fargo Bank, N.A. , 814 F.3d 763, 766 (5th Cir. 2016).

A.

Butler first challenges the dismissal of her claims against DuPont and DOH as time-barred. Butler alleges that DuPont, as the former neoprene manufacturer until 2015 and current owner of the PWF's land and buildings, is liable for various tort claims arising from the chloroprene emissions. She also claims that DOH failed to adequately warn Butler and the community about the dangers of chloroprene exposure and failed to fully investigate the health effects of chloroprene. We first consider whether Butler's allegations on their face are prescribed, and second, whether any tolling of prescription applies.

1.

Under Louisiana's civil code, Butler's alleged tort claims are "subject to a liberative prescription of one year," which "commences to run from the day injury or damage is sustained." La. Civ. Code art. 3492. "When damages are not immediate, the action in damages is formed and begins to prescribe only when the tortious act actually produces damage and not on the day the act was committed." Tenorio v. Exxon Mobil Corp. , 170 So. 3d 269, 274 (La. Ct. App. 2015). An injury or damage is sustained "when it has manifested itself with sufficient certainty to support accrual of a cause of action." Id. " ‘The burden of proof is normally on the party pleading prescription; however, if on the face of the petition it appears that prescription has run, ... the burden shifts to the plaintiff to prove a suspension or interruption of the prescriptive period’ based on the equitable doctrine of contra non valentem ." In re Taxotere (Docetaxel) Prods. Liab. Litig. , 995 F.3d 384, 388–89 (5th Cir. 2021) (quoting Younger v. Marshall Indus. Inc. , 618 So. 2d 866, 869 (La. 1993) ); accord Hogg v. Chevron USA, Inc ., 45 So. 3d 991, 998 (La. 2010).

Butler filed her initial complaint in state court on June 5, 2018. Therefore, for Butler's claims to be timely, the prescription period must have begun or been tolled until June 5, 2017. Butler alleged that she began seeking treatment for symptoms of chloroprene exposure in April 2012, which is the date her injury first accrued. Thus, unless tolled, the one-year prescription expired well before Butler filed suit six years later.

2.

We next consider whether Butler has met her burden in proving that prescription was tolled under the doctrine of contra non valentem . In re Taxotere , 995 F.3d at 388–89. At the pleadings stage, she has.

Contra non valentem is an equitable doctrine that tolls prescription where, inter alia , "the cause of action is neither known nor reasonably knowable by the plaintiff." Marin v. Exxon Mobil Corp. , 48 So. 3d 234, 245 (La. 2010). Under this doctrine, "the prescriptive period begins to run ‘on the date the injured party discovers or should have discovered the facts upon which his cause of action is based.’ " Chevron USA, Inc. v. Aker Mar., Inc. , 604 F.3d 888, 893 (5th Cir. 2010) (quoting Griffin v. Kinberger , 507 So. 2d 821, 823 (La. 1987) ). The exact time at which prescription begins to run "depends on the reasonableness of a plaintiff's action or inaction." Knaps v. B & B Chem. Co. , 828 F.2d 1138, 1140 (5th Cir. 1987) (per curiam) (quoting Jordan v. Emp. Transfer Corp. , 509 So. 2d 420, 423 (La. 1987) ).

Consequently, prescription begins only "when a plaintiff obtains actual or constructive knowledge of facts indicating to a reasonable person that he or she is the victim of a tort." Campo v. Correa , 828 So. 2d 502, 510 (La. 2002). "Constructive knowledge is whatever notice is enough to excite attention and put the injured party on guard and call for inquiry. Such notice is tantamount to knowledge or notice of everything to which a reasonable inquiry may lead." Id. at 510–11. "That means prescription runs ‘from the time there is notice enough to call for inquiry about a claim, not from the time when the inquiry reveals facts or evidence sufficient to prove the claim.’ " In re Taxotere , 995 F.3d at 391 (quoting Terrel v. Perkins , 704 So. 2d 35, 39 (La. Ct. App. 1997) ). Under this standard, "a plaintiff will be deemed to know what he could have learned with reasonable diligence." Tenorio , 170 So. 3d at 274.

Butler first contends contra non valentem applies because she was not "aware in April 2012 that her symptoms were caused by chloroprene, much less that acts of [DuPont] and DOH were causing her symptoms." But actual knowledge is not required.

Butler next contends that she lacked even constructive knowledge that the chloroprene emissions from PWF caused her symptoms. "[T]he ultimate issue in determining whether [Butler] had constructive knowledge sufficient to commence a prescriptive period is the reasonableness of [Butler's] action or inaction in light of [her] education, intelligence, and the nature of the defendant's conduct." Wells v. Zadeck , 89 So. 3d 1145, 1151 (La. 2012) (quoting Marin , 48 So. 3d at 246 ). Consequently, "the reasonableness of the plaintiff's actions centers upon the knowledge she possessed." Id . at 1152. Louisiana courts consistently consider "the reasonableness of a plaintiff's action or inaction" based on the position she is in—including the information known or otherwise available to her at the time. See Jordan , 509 So. 2d at 423 ; see also Knaps , 828 F.2d at 1140 ; Lennie v. Exxon Mobil Corp. , 251 So. 3d 637, 646 (La. Ct. App. 2018).

Butler's specific allegations as to the onset of her symptoms attributable to chloroprene and her ensuing treatment are admittedly thin. However, at the pleadings stage, Butler need only allege "sufficient factual matter, accepted as true, to ‘state a claim to relief that is plausible on its face.’ " Ashcroft v. Iqbal , 556 U.S. 662, 678, 129 S.Ct. 1937, 173 L.Ed.2d 868 (2009) (quoting Bell Atl. Corp. v. Twombly , 550 U.S. 544, 570, 127 S.Ct. 1955, 167 L.Ed.2d 929 (2007) ). Here, consistent with the pleadings standard in which we must "accept all well-pleaded facts as true and view all facts in the light most favorable to the plaintiff," Thompson v. City of Waco , 764 F.3d 500, 502 (5th Cir. 2014), she has alleged enough.

While Butler's FAP alleged that she began experiencing symptoms in April 2012 that were ultimately linked to chloroprene exposure—i.e. "[d]ue to Plaintiff's exposure to the chloroprene emissions"—more facts are necessary to determine when she received notice of such linkage. Contrary to defendants' urging, we decline to read the complaint's phrasing of "due to" so narrowly to mean that Butler knew, in 2012, that chloroprene caused her symptoms. Indeed, at oral argument, Butler's counsel clarified that Butler's symptoms "were not linked to chloroprene until much, much later." DuPont rightfully concedes that its stronger argument is that Butler—at some point after she first started seeking medical treatment—was on constructive notice that chloroprene may have been responsible for her symptoms. But that fact-bound conclusion is not evident to us at the pleadings stage. While conclusive proof as to the cause of Butler's symptoms is not required to satisfy constructive notice that begins the prescriptive period, there must be "enough notice to call for an inquiry about a claim." Luckett v. Delta Airlines, Inc. , 171 F.3d 295, 300 (5th Cir. 1999) ("The commencement of prescription does not necessarily wait for the pronouncement of a victim's physician or of an expert. ... [T]he prescriptive period commences when there is enough notice to call for an inquiry about a claim, not when an inquiry reveals the facts or evidence that specifically outline the claim." (internal citations omitted)). On the record before us, we cannot say at what point Butler received such notice. Indeed, that may be dispositive upon further discovery of Butler's medical treatment history as to what she learned, and when she learned it. Compare, e.g. , Jenkins v. Bristol-Myers Squibb Co., 689 F. App'x 793, 796–97 (5th Cir. 2017), with Crochet v. Bristol-Myers Squibb Co. , 804 F. App'x 249, 252–55 (5th Cir. 2020).

Moreover, DuPont and DOH primarily rely on cases in which a plaintiff's diagnosis , more than one year prior to filing suit, constitutes constructive notice. But that distinction is critical, and supports our contrary holding here. Significantly, as alleged in her pleadings, Butler was not diagnosed or otherwise told that her symptoms were a result of excessive chloroprene emissions more than one year prior to filing suit. Cf. Tenorio , 170 So. 3d at 275 ("[Plaintiff's] diagnosis was constructive notice sufficient to put [him] on guard and to call him to inquire into the cause of his condition." (emphasis added)); Lennie , 251 So. 3d at 648 ("Mr. Lennie's diagnosis of lung cancer in January 2010 was constructive notice sufficient to put the [plaintiffs] on guard and to call for them to inquire further into the cause of his condition." (emphasis added)); Guerin v. Travelers Indem. Co. , 296 So. 3d 625, 631 (La. Ct. App. 2020) ("[Plaintiff's] diagnosis in 2015 was constructive notice sufficient to put him on guard and to call him to inquire into the cause of his condition." (emphasis added)).

At oral argument, DuPont attempted to distinguish these cases by asserting that "latent" "cellular level diseases like cancer" require a diagnosis before prescription runs, but that Butler's symptoms were "severe" "overt injuries" sufficient to constitute constructive notice without a diagnosis. We choose not to reach such an intensely fact-based distinction at the pleadings stage and on the sparse record before us. This further demonstrates why discovery—at least as to prescription—is warranted here.

Finally, our conclusion is further bolstered by defendants' consistent denial that chloroprene—either in April 2012 or in the years since—caused any of Butler's symptoms. In other words, absent a diagnosis or any facts that Butler received sufficient notice linking her symptoms to chloroprene, and drawing all reasonable inferences in Butler's favor at the pleadings stage, we cannot conclude that Butler had constructive notice more than one year prior to filing suit. Consistent with Louisiana's contra non valentem analysis as to what Butler reasonably knew or should have known at the time, we disagree that, on the record before us, Butler had constructive knowledge sufficient to trigger the running of prescription over a year before she filed suit in June 2018. See Wells , 89 So. 3d at 1151. Accordingly, we reverse the district court's holding that Butler's claims were prescribed.

B.

Second, Butler appeals the denial of her motion to amend her complaint to assert a claim against DuPont for the ongoing chloroprene emissions. Specifically, Butler claimed that DuPont and Denka were strictly liable for the PWF's ongoing chloroprene emissions from PWF's "defective" neoprene production units pursuant to Louisiana Civil Code Articles 2317 and 2317.1. Butler alleged that DuPont "owned and operated the entire PWF from 1969 to 2015," when it sold the PWF to Denka. After the sale, "except for the neoprene manufacturing units of the PWF ... DuPont retained ownership of the entirety of the PWF land and buildings, including the building where it currently manufactures Kevlar." Thus, Butler asserts, DuPont and Denka are both liable because "during separate periods of time, [they] have had ownership, care, custody, and control of the neoprene units of the PWF; and DuPont has maintained care, custody, and control of the PWF since 1969."

The first requirement for strict (custodial) liability is that "[t]he thing which caused injury must be in the care, custody and control of the defendant." Palermo v. Port of New Orleans , 951 So. 2d 425, 438 (La. App. 2007) (emphasis added); accord Fruge ex rel. Fruge v. Parker Drilling Co. , 337 F.3d 558, 565 (5th Cir. 2003). "Louisiana courts have generally held that (1) ownership of a thing establishes a rebuttable presumption of custody or ‘garde,’ and (2) in a case of non-ownership, a defendant may be found to have custody over property when he exercises direction and control of the thing and derives some benefit from it." Coulter v. Texaco, Inc. , 117 F.3d 909, 913 (5th Cir. 1997) ; accord Davis v. Riverside Court Condo. Ass'n Phase II, Inc. , 154 So. 3d 643, 648 (La. App. 2014) ("[I]n determining whether a thing is in one's custody or garde , courts should consider (1) whether the person bears such a relationship as to have the right of direction and control over the thing; and (2) what, if any, kind of benefit the person derives from the thing." (alteration in original) (quoting Dupree v. City of New Orleans , 765 So. 2d 1002, 1009 (La. 2000) )).

We agree with the district court that the "thing" Butler must show "custody" of to succeed on her custodial liability claim is the PWF's "neoprene production units," rather than the land itself. Under Articles 2317 and 2317.1, the defective "object" is distinct from the property on which the injury occurred, unless an inherent defect in the property caused the injury. Compare Doughty v. Insured Lloyds Ins. Co. , 576 So. 2d 461, 464 (La. 1991) (defective machinery located on the property was considered "the object," not the property itself), with Dupree , 765 So. 2d at 1005 (property was considered "the object" where cause of the injury was the property itself: a cave-in on a New Orleans city street). Butler does not argue that the PWF as a whole or the underlying land caused the "defect," but rather that "both DuPont and Denka have garde over the neoprene units and other sources of chloroprene emissions at DuPont's PWF."

The district court next concluded that Butler failed to allege garde over the neoprene production units after 2015 because "mere ownership" of the land and buildings is "insufficient to state a plausible strict or custodial liability claim against DuPont when [Butler's] own allegations state that, since 2015, Denka alone had custody over and operated the objects allegedly causing the harm, the allegedly faulty neoprene units operated during the manufacturing process." Butler III , 2019 WL 2417500, at *5.

Generally, "[d]etermining who has the custody or garde of the thing is a fact driven determination." Dupree , 765 So. 2d at 1009. Here, Butler principally argues that because DuPont retained ownership of the land and buildings, it likely retained some contractual control over Denka's neoprene production as well. For example, Butler's counsel asserted at oral argument that "it would seem a logical inference that DuPont still has some rights over what Denka is doing on DuPont's property." DuPont, in response, argues that Butler fails to allege any facts to support that, aside from ownership of the land, DuPont retains control or custody over PWF's neoprene production units.

We need not resolve whether Butler alleges enough, here, to support her contention that DuPont has garde over PWF's neoprene production units. For the reasons that follow, Butler's custodial liability claims against DuPont fail for the same reason as her claims against Denka: a failure to state a plausible duty and corresponding breach. See Socorro v. City of New Orleans , 579 So. 2d 931, 937 (La. 1991) (finding no liability even though the defendant had garde over the injury-causing defect).

C.

Next, Butler appeals the dismissal of her negligence and strict custodial liability claims against Denka arising from its past and current neoprene manufacturing at the PWF. Butler says that Denka "has failed to exercise reasonable care to prevent [the] emission of unreasonably dangerous chloroprene concentrations into the air," and that "Denka's neoprene manufacturing equipment is unreasonably dangerous, because of its excessive chloroprene emissions." Though not prescribed because of the continuing tort doctrine, the district court granted Denka's motion to dismiss for failure to state a plausible claim. We agree.

1.

As to the negligence claims, Butler asserts that Denka unreasonably emits dangerous chloroprene concentrations in violation of Louisiana Civil Code Articles 2315 and 2316. Those articles provide that "[e]very act whatever of man that causes damages to another obliges him by whose fault it happened to repair it," LA. CIV. CODE art. 2315(A), and that "[e]very person is responsible for the damage he occasions not merely by his act, but by his negligence, his imprudence, or his want of skill," La. Civ. Code art. 2316. Under Louisiana law's duty-risk analysis of negligence liability, Butler must prove five separate elements: "(1) the defendant had a duty to conform his conduct to a specific standard (the duty element); (2) the defendant's conduct failed to conform to the appropriate standard (the breach element); (3) the defendant's substandard conduct was a cause in fact of the plaintiff's injuries (the cause-in-fact element); (4) the defendant's substandard conduct was a legal cause of the plaintiff's injuries (the scope of liability or scope of protection element); and (5) the actual damages (the damages element)." Lemann v. Essen Lane Daiquiris , 923 So. 2d 627, 633 (La. 2006). Duty is the "threshold issue." Id.

As to strict custodial liability, Butler argues that Denka is the owner or custodian of a defective thing—the neoprene manufacturing equipment—in violation of Louisiana Civil Code Articles 2317 and 2317.1. Those articles provide that "[w]e are responsible, not only for the damage occasioned by our own act, but for that which is caused by ... the things which we have in our custody," LA. CIV. CODE art. 2317, and that "[t]he owner or custodian of a thing is answerable for damage occasioned by its ruin, vice, or defect, only upon a showing that he knew or, in the exercise of reasonable care, should have known of the ruin, vice, or defect which caused the damage, that the damage could have been prevented by the exercise of reasonable care, and that he failed to exercise such reasonable care," La. Civ. Code art. 2317.1 ; accord Renwick v. PNK Lake Charles, L.L.C. , 901 F.3d 605, 616 (5th Cir. 2018) (citing Bufkin v. Felipe's La., LLC , 171 So. 3d 851, 855 (La. 2014) ).

"Strict liability" is a misnomer, however, because Article 2317.1's knowledge requirement "effectively eliminated strict liability ... turning it into a negligence claim." Renwick , 901 F.3d at 617 n.12 (quoting Burmaster v. Plaquemines Parish Gov't , 982 So.2d 795, 799 n.1 (La. 2008) ). Accordingly, a claim for "strict" liability requires that a duty of care was breached, just as a negligence claim does. Bd. of Comm'rs v. Tenn. Gas Pipeline Co. , 850 F.3d 714, 729 n.52 (5th Cir. 2017) (citing Oster v. Dep't of Transp. & Dev. , 582 So. 2d 1285, 1288 (La. 1991) ). "There is essentially no difference between the two types of claims under Louisiana law ...." Id . at 729.

2.

Here, Butler fails to adequately allege a duty owed by Denka, and consequently whether Denka breached such a duty. Thus, both the negligence and strict liability claims fail to state a plausible claim.

Butler repeatedly references the EPA's NATA recommended "acceptable risk" chloroprene emissions threshold of 0.2 µg/m3 (micrograms per cubic meter). The district court dismissed Butler's invocation of that threshold as a legal duty because it is "less than a federal regulation" and even the EPA "disclaims" it as an "absolute risk measure" of toxicity. Butler IV , 2020 WL 2747276, at *10–11. The district court concluded that Butler "fails to allege that [Denka] had a duty to conform its conduct to a specific legally-enforceable standard (or any corresponding duty to warn the plaintiff concerning its business operations) and that it breached that duty." Id. at *9. Thus, the court concluded that Butler's "allegations concerning [Denka's] duty and breach are conclusory and speculative" because her "theory that [Denka] owed a duty not to exceed a certain level of emissions and breached that duty is not plausible." Id. at *12.

On appeal, Butler now disclaims any reliance on the EPA's stated risk threshold. Although Butler sought to enjoin Denka from emitting chloroprene "in excess of 0.2 micrograms (mcg) per cubic meter into the air," she now contends that the district court "misconstrued" her petitions. Instead, Butler asserts that Denka violated Louisiana's general duty "to use reasonable care to avoid injury to another." Rando v. Anco Insulations, Inc. 16 So. 3d 1065, 1086 (La. 2009). She says Denka's chloroprene emissions—untethered from any particular emissions threshold—are nonetheless unreasonably excessive.

While we remain skeptical of Butler's contention that the district court misconstrued her claims, Butler's retreat to generalized grievances is unavailing. While Louisiana law does impose a "universal duty" on defendants in a negligence action to use "reasonable care," Rando , 16 So. 3d at 1086, plaintiffs are still required to assert a "specific standard" of care. See Lemann , 923 So. 2d at 633. The inquiry into a defendant's particular duty "is whether the plaintiff has any law (statutory, jurisprudential, or arising from general principles of fault) to support the claim that the defendant owed him a duty." Id. ; accord Boykin v. La. Transit Co. , 707 So. 2d 1225, 1230 (La. 1998) (emphasizing that in a "proper duty-risk analysis" the court should first identify "the duty imposed upon the defendant by statute or rule of law"). "Whether a legal duty exists, and the extent of that duty, depends on the facts and circumstances of the case, and the relationship of the parties." Joseph v. Dickerson , 754 So. 2d 912, 916 (La. 2000).

Here, Butler relies not on the EPA, OSHA, or other agencies' recommended emissions thresholds but on generalized pronouncements that Denka has violated its duty to take "reasonable care." Yet, Butler points to no "statutory," "jurisprudential," or any other source of law—and we have likewise found none—in which such generalized references to "excessive emissions," "acceptable risk threshold," and "unreasonably dangerous emissions," constitutes a sufficient legal duty to support a negligence or custodial liability claim. See Bd. of Comm'rs v. Tenn. Gas Pipeline Co. , 850 F.3d 714, 727–28 (5th Cir. 2017) (dismissing negligence and strict liability claims asserting that defendant companies' dredging caused erosion and costly flood protection measures because plaintiffs failed to allege an applicable legal duty under the federal and state statutory and regulatory schemes governing the state's waterways). Consequently, we agree with the district court that Butler fails to allege a duty, or a breach of such duty, based on Denka's alleged "excessive" chloroprene emissions. Absent a showing of duty or breach, we need not address the district court's alternative holding as to causation or injury. See Lemann , 923 So. 2d at 633 ("A negative answer to any of the inquiries of the duty-risk analysis results in a determination of no liability."). Butler's custodial liability claims fail for the same reason. See Tenn. Gas Pipeline Co. , 850 F.3d at 729.

D.

Finally, Butler appeals the dismissal of her declaratory relief claims against DEQ. Butler alleged that DEQ failed to warn the community of the risks of chloroprene exposure, provide notice concerning the high levels of chloroprene emissions, and abide by its statutory duties to conduct routine sampling and testing of hazardous waste from the PWF. On appeal, she asserts that "DEQ is violating Plaintiff's Louisiana constitutional rights by subjecting her to harmful concentrations of chloroprene," and seeks a judgment declaring the same.

The district court dismissed Butler's claims against DEQ because she failed to comply with the agency's administrative process, including the agency's authority to issue declaratory rulings prior to seeking a declaratory judgment in court, pursuant to Louisiana Revised Statutes section 30:2050.10(C).

On appeal, Butler barely acknowledges the district court's detailed explication of the applicable law, regulations, and administrative procedures—instead referring to them as "irrelevant." Rather, Butler cursorily insists that she is entitled to declaratory relief under the Louisiana Constitution and Louisiana Code of Civil Procedure Article 1871. Butler does not brief how these provisions interact with, let alone supersede, the state's significant regulatory framework, and we need not address such inadequately briefed arguments here. Cinel v. Connick , 15 F.3d 1338, 1345 (5th Cir. 1994) ("A party who inadequately briefs an issue is considered to have abandoned the claim.").

IV.

For the foregoing reasons, the judgment of the district court is REVERSED in part and AFFIRMED in part, and REMANDED for further proceedings consistent with this opinion.

Haynes, Circuit Judge, concurring in part, dissenting in part:

I respectfully dissent from Sections III.B and III.C of the majority opinion and the corresponding portion of the judgment. As the majority opinion demonstrates, we lack understanding of Louisiana law on the scope of a defendant's legal duty regarding the emission of chemicals. To determine whether certification is appropriate, we weigh three factors: (1) "the closeness of the question[s]"; (2) federal–state comity; and (3) "practical limitations," such as the possibility of delay or difficulty of framing the issue. Swindol v. Aurora Flight Scis. Corp. , 805 F.3d 516, 522 (5th Cir. 2015) (quotation omitted). The Rules of the Louisiana Supreme Court allow us to certify dispositive questions of Louisiana law on our own accord if there is a lack of "clear controlling precedent" from the Louisiana Supreme Court. McKesson v. Doe , ––– U.S. ––––, 141 S. Ct. 48, 50, 208 L.Ed.2d 158 (2020) (per curiam) (quotation omitted). I discuss these points below.

As demonstrated by the majority opinion, we lack controlling precedent concerning this novel and important question of state law, making is a "close question." Indeed, it concedes, "[t]here is a dearth of Louisiana case law on a defendant's legal duty regarding the emission of chemicals." Op. at 445 n.26. The precedent we do have is of limited utility.

In Rando v. Anco Insulations Inc. , 16 So.3d 1065 (La. 2009), the Louisiana Supreme Court held that a defendant-employer had a duty to protect a plaintiff-employee from exposure to asbestos—despite there being no law or regulation at the time of the exposure regarding the harm of asbestos—because the defendant "knew or should have known of the dangers of asbestos exposure at the time of [the plaintiff's] employment." Id. at 1087. While Rando is helpful to our analysis (and, frankly, is more supportive of Butler's view than Denka's), the Louisiana Supreme Court has never addressed whether, and to what extent, this duty applies outside of the employment law context. A further review of the existing law indicates that there are no "clear controlling precedents" from the Louisiana Supreme Court that discuss the full scope of this duty. As such, it is appropriate for us to certify the question sua sponte.

The question of whether an emitter has a duty to limit emissions to a level it should have known would not harm human health is an important one that can substantially affect residents of the particular state, so under our federal-state comity, I conclude that we should defer to the Louisiana Supreme Court on this topic. Moreover, certification of a question to a state supreme court is particularly appropriate where, as here, the dispute presents novel issues of state law, calling for the exercise of judgment by the state courts. See Lehman Bros. v. Schein , 416 U.S. 386, 391, 94 S.Ct. 1741, 40 L.Ed.2d 215 (1974). As the majority opinion notes, Butler's negligence claim does not rely on any statutory or jurisprudential law to establish duty. Rather, Butler relies on the general principle that individuals have a duty to take "reasonable care." Where, as here, the plaintiff states a generalized duty, the court must determine "whether the rule is intended to protect him from the particular harm alleged." In re FEMA Trailer Formaldehyde Prods. Liab. Litig. , 838 F. Supp. 2d 497, 505 (E.D. La. 2012) (citing Meany v. Meany , 639 So.2d 229, 233 (La. 1994) ). In doing so, courts "may consider various moral, social, and economic factors." Meany , 639 So.2d at 233. As such, in deciding legal duty questions, courts are required to "make a policy decision in light of the unique facts and circumstances presented." Lemann v. Essen Lane Daiquiris, Inc. , 923 So. 2d 627, 633 (La. 2006). The determination of a legal duty question presents a paradigmatic situation of a case calling for the exercise of judgment by state courts. See Lehman Brothers , 416 U.S. at 391, 94 S.Ct. 1741. Indeed, the Supreme Court recently remanded to the Fifth Circuit to certify a novel question on duty under Louisiana negligence law to the Louisiana Supreme Court. See McKesson , 141 S. Ct. at 51 (2020). At bottom, certification in this case would allow Louisiana courts to properly exercise their judgment on novel issues of state law.

Additionally, the question of whether Denka owed Butler a legal duty is directly dispositive of Butler's claims (assuming arguendo that Butler has sufficiently pleaded breach, causation, and damages). Therefore, whether or not Denka has a legal duty—regarding the emission of excessive chemicals that it allegedly should have known could have carcinogenic effects—will determine the outcome of this case, with respect to Denka.

As far as practicality, there is no indication that the Louisiana Supreme Court would unduly delay the case—it handles cases promptly.

In summary, it is surprising to say that, because we do not know what the law is on this, we are going to let emitters spew pollution harming individuals without recourse. This case therefore has wide-ranging implications on future plaintiffs' ability to pursue similar claims under Louisiana law. The majority opinion's declination to certify this question could prevent future plaintiffs from filing suit against alleged environmental contaminators, merely because they lack detailed information on the emitter's specific actions prior to discovery.

For the foregoing reasons, I conclude that we should certify this issue to the Louisiana Supreme Court: whether an emitter has a duty (the failure of which gives rise to a cause of action by an individual who was harmed) to fail to emit pollutants above a level that causes harm to human health. See In re Katrina Canal Breaches Litig. , 613 F.3d 504, 509 (5th Cir. 2010) ("[C]ertification may be advisable where important state interests are at stake and the state courts have not provided clear guidance on how to proceed." (quotation omitted)); see also Jesco Const. Corp. v. NationsBank Corp. , 278 F.3d 444, 448 (5th Cir. 2001) (same). I therefore dissent from Sections III.C and III.B and the corresponding portion of the judgment; I otherwise concur.

Andrew S. Oldham, Circuit Judge, dissenting in part:

I respectfully dissent from section III.A of the majority's opinion. Butler has not met her burden to prove tolling of the prescription period. I would affirm the district court's holding that Butler's claims against DuPont and DOH were time-barred.

The majority concludes Butler's injury accrued—and prescription began to run—in April 2012 when she began seeking medical treatment. With that much, I agree. But the majority then concludes that Butler is entitled to tolling of the prescription period because, at the pleadings stage, there is not enough evidence to put her on constructive notice that chloroprene was responsible for her symptoms. There are five problems with that.

First, Butler's own pleadings contained facts sufficient to establish constructive notice. Under Louisiana law, constructive notice includes "notice of everything to which a reasonable inquiry may lead." Campo v. Correa , 828 So. 2d 502, 511 (La. 2002). And here, Butler alleged numerous public facts that any reasonable inquiry would uncover:

• In 2010, EPA concluded chloroprene is likely carcinogenic.

• In December 2015, EPA classified chloroprene as a likely human carcinogen.

• In July 2016, EPA held a public meeting in Butler's community to discuss potential chloroprene emission issues.

• In December 2016, at a school board meeting, the community discussed—and community members expressed concern about—local chloroprene concentrations.

• In January 2017, Denka made an agreement with DEQ to reduce its chloroprene emissions by 85%.

• And in April 2017, EPA released a redacted copy of an inspection report, which revealed numerous areas of non-compliance at the facility.

Butler did not file suit until June 5, 2018. So it was her burden to prove that tolling lasted until June 5, 2017. But every one of the above facts points to an earlier date. Butler's own petition reveals what a reasonable inquiry would have uncovered and when it would have uncovered it.

Second, the efforts that led Butler to learn these facts by June 2018 could have led her to discover them sooner. That matters because the limitations period is more likely to bar relief when the petition's allegations are "based on the same facts" that the plaintiff "could have discovered had [she] investigated" earlier. Marin v. Exxon Mobil Corp. , 48 So. 3d 234, 250 (La. 2010) ; accord Wells v. Zadeck , 89 So. 3d 1145, 1152 (La. 2012) (noting inaction is reasonable when a plaintiff is "prevented from filing [a] claim" because the cause of action is not "reasonably knowable by the plaintiff"). But there's nothing to suggest the facts that formed the basis of Butler's petition in 2018 were not reasonably knowable well before then. She doesn't point to anything that would have made these facts undiscoverable until June 2017. So the very same efforts she eventually made could have been made earlier.

Third, the majority concludes that Butler is entitled to discovery to determine "what she learned, and when she learned it." Ante , at 440. But this confuses actual and constructive notice. Any information uncovered in discovery only could show Butler's actual knowledge. But that's beside the point. "It is not necessary to have actual knowledge as long as there is constructive knowledge." Tenorio v. Exxon Mobil Corp. , 170 So. 3d 269, 274 (La. Ct. App. 2015). Butler is "deemed to know" every fact she "could have learned with reasonable diligence." Ibid. Whether and when she did in fact know is irrelevant.

Fourth, the absence of a formal diagnosis can't rescue Butler's claims. Prescription runs "from the time there is enough notice to call for inquiry about a claim, not from the time when the inquiry reveals facts or evidence sufficient to prove the claim." In re Taxotere (Docetaxel) Prods. Liab. Litig. , 995 F.3d 384, 391 (5th Cir. 2021). A medical diagnosis is not a prerequisite—it's just one form of notice. And here, notice came in a different form: As the district court concluded, "[s]eeking medical attention for approximately 20 symptoms consistently for years would put a reasonable person on guard to inquire into why she is suffering persistently with so many symptoms." Butler v. Denka Performance Elastomer LLC , 2019 WL 1160814, at *4 (Mar. 13, 2019). And to the extent Butler argues her symptoms were unexplained without a diagnosis, her own allegations again fill the gap: She alleged she experienced a fear of cancer from her symptoms and medical treatment. The mental link she formed between her symptoms and the possibility of cancer was enough to "put [her] on guard and to call h[er] to inquire into the cause of h[er] condition." Tenorio , 170 So. 3d at 275.

Finally, the majority makes much of the fact that this case is only at the pleadings stage. And it rightly notes we must "accept all well-pleaded facts as true and view all facts in the light most favorable to the plaintiff." Thompson v. City of Waco , 764 F.3d 500, 502 (5th Cir. 2014). But that makes no difference either, because it's the very facts Butler pleaded that make her ineligible for tolling. If we accept all her facts as true, it only establishes that she had constructive notice long before she sued.

For these reasons, Butler cannot meet her burden to prove prescription was tolled. She's pleaded facts that establish constructive notice well before she filed suit. And further discovery won't do anything to erase the facts she alleged. I would affirm the district court's judgment.