Chlorpyrifos Parkinson's Lawsuits Reach Delaware as Durnell Reshapes What Plaintiffs Can Plead

Four men filed a product liability complaint in Delaware Superior Court on 15 September 2026 against Corteva Inc., Corteva Agriscience LLC, The Dow Chemical Company and Loveland Products Inc., alleging that decades of handling the organophosphate insecticide chlorpyrifos caused the Parkinson's disease each of them now has. It is the second publicly reported chlorpyrifos Parkinson's lawsuit of the year and the first with multiple plaintiffs, and it lands in a legal environment that changed fundamentally eleven weeks earlier, when the Supreme Court held in Monsanto Co. v. Durnell that federal pesticide law preempts the state-law warning claim on which the entire Roundup litigation was built.

That sequence is the story. The science supporting a chlorpyrifos Parkinson's lawsuit got materially stronger in December 2025. The most valuable legal theory for prosecuting one disappeared in June 2026. Anyone assessing this docket — as claimants' counsel, as defense counsel, or as a funder pricing a portfolio — has to hold both facts at once, and none of the pages currently ranking for this subject does.

What is the chlorpyrifos Parkinson's lawsuit about?

A chlorpyrifos Parkinson's lawsuit is a personal injury claim alleging that repeated occupational or residential exposure to chlorpyrifos, an organophosphate insecticide sold for decades under names including Dursban, Lorsban and Cobalt, damaged the plaintiff's dopaminergic neurons and caused Parkinson's disease, and that the companies that designed, registered, manufactured and distributed it knew or should have known of the neurological risk and did not act on it. The claims are brought against pesticide manufacturers and distributors, not employers, and they are being filed one at a time in state courts rather than in any consolidated federal proceeding.

The theory is not novel in its shape. It is the paraquat theory, the Roundup theory, the structure of every modern pesticide Mass Tort: a registered agricultural chemical, a latency period measured in decades, an epidemiological signal that firmed up long after the exposure ended, and a defendant group that continued selling while the literature accumulated. What is novel is the timing. Chlorpyrifos claims are the first pesticide filings to be drafted, from scratch, into a post-Durnell world.

The 15 September Delaware complaint, and what is in it

The four plaintiffs are Keith Lutz, Dean Larson, Paul Chesterson and Arthur Emery. Their pleaded exposure histories differ in ways that will matter a great deal later: Lutz from 1985 to 1991, Larson from 1980 all the way to 2019, Chesterson from 1985 to 1992, and Emery from 1983 to 1995. Three of the four describe exposure that ended in the early to mid-1990s. One describes exposure continuing to the end of the last decade.

The complaint alleges that the defendants knew or should have known that chlorpyrifos could cause neurological damage, that they did not adequately study what long-term exposure did to adults as opposed to children, and that they did not warn users of a Parkinson's risk. The named defendants are Corteva Inc. and Corteva Agriscience LLC — the agricultural business spun out of the DowDuPont merger — together with The Dow Chemical Company, which developed and long sold the chemical, and Loveland Products Inc., a distributor.

Set that against the first-filed case. Alexander Ramos, a former pest control worker from Selden, New York, sued in the Philadelphia County Court of Common Pleas on 16 June 2026; the defendants removed, and the case now sits in the Eastern District of Pennsylvania as Ramos v. Corteva, Inc., No. 2:26-cv-04988. The Ramos complaint alleges that the companies worked together to develop and sell the product and to keep the Parkinson's connection out of view. Aimee Wagstaff, who represents Ramos and who was central to the paraquat litigation, said at filing that she expected more cases to follow. Three months later, four more plaintiffs arrived.

	Ramos v. Corteva, Inc.	Lutz, Larson, Chesterson and Emery
Filed	16 June 2026	15 September 2026
Original forum	Philadelphia County Court of Common Pleas	Delaware Superior Court
Current forum	E.D. Pa., No. 2:26-cv-04988 (on removal)	Delaware Superior Court
Plaintiffs	1 (former pest control worker)	4
Corteva Inc. / Corteva Agriscience LLC	Yes	Yes
The Dow Chemical Company	Yes	Yes
FMC Corporation	Yes	Not named
Loveland Products Inc.	Not named	Yes
Exposure period pleaded	Occupational, pest control	1980-2019 across four plaintiffs

The difference in the defendant sets is not a drafting quirk. Chlorpyrifos was a widely licensed active ingredient sold in formulated products by a long list of registrants over four decades. Whether FMC or Loveland is in a given complaint reflects which branded product a particular plaintiff can place in his own hands. That is Product Identification, and it is the practical constraint that will shape this docket more than any doctrinal question.

The choice of forum is also deliberate. Corteva and Dow are Delaware entities, which makes Delaware Superior Court a court of general jurisdiction over them and complicates the usual removal-and-remand skirmish. Philadelphia and Delaware are both courts with deep institutional experience in pharmaceutical and chemical mass torts. Plaintiffs' counsel are keeping these cases in state court where they can, and the removal in Ramos shows the defense is equally clear about wanting them out.

Does chlorpyrifos cause Parkinson's disease?

The strongest evidence that chlorpyrifos causes Parkinson's disease is a study published in Molecular Neurodegeneration on 11 December 2025 by a UCLA-led team, which reported an odds ratio of 2.68, with a 95 per cent confidence interval of 1.58 to 4.55, for long-term residential exposure to chlorpyrifos. That is a risk roughly two and a half times higher than for unexposed comparators, and the confidence interval excludes 1.0 by a wide margin. For participants with the longest duration of occupational proximity to chlorpyrifos applications, the estimate was approximately 2.74.

The design matters for how this will survive a Daubert Challenge. The epidemiology draws on UCLA's Parkinson's Environment and Genes cohort, comparing 829 people with Parkinson's disease against 824 controls in California farming communities. Exposure was not self-reported from memory alone; the researchers geocoded residential and workplace addresses and matched them against California's pesticide use reporting system, which is among the most granular application datasets in the country. That is an unusually defensible exposure assessment for a retrospective study, and it is the feature defense experts will have the hardest time dismantling.

The paper did not stop at association. The same team reported experimental work in mice and zebrafish showing loss of dopamine-producing neurons, neuroinflammation, disruption of autophagy — the process by which cells clear damaged proteins — and protein aggregation of the kind seen in Parkinson's patients. That combination, human epidemiology plus a mechanistic account of how the exposure could produce the disease, is precisely what a General Causation opinion needs to be admissible. It is also what the Roundup plaintiffs never quite had and the paraquat plaintiffs assembled slowly.

One finding in the study deserves more attention from practitioners than it has received. The association was strongest for exposures occurring 10 to 20 years before diagnosis. Epidemiologically, that fits a neurodegenerative disease with a long prodromal phase. Legally, it is a Statute of Limitations argument waiting to happen, and it cuts both ways. It supports a Discovery Rule position — a plaintiff exposed in 1988 and diagnosed in 2015 could not have connected the two before the literature existed — and it simultaneously gives the defense a clean line of attack on any plaintiff whose diagnosis long predates the date he claims to have discovered the connection.

Chlorpyrifos works by inhibiting acetylcholinesterase, the enzyme that clears acetylcholine from the synapse. That mechanism is the basis of its acute toxicity and has been understood since it came to market. The dopaminergic injury described in the 2025 work is a different pathway, and establishing it as a known or knowable risk during the relevant sales period is the evidentiary burden that will decide these cases. Specific Causation will then be litigated plaintiff by plaintiff on exposure intensity, duration and differential diagnosis.

Which companies are being sued over chlorpyrifos?

The defendants named so far are Corteva Inc., Corteva Agriscience LLC, The Dow Chemical Company, FMC Corporation and Loveland Products Inc. Dow developed chlorpyrifos and sold it for decades as Dursban for residential and structural use and Lorsban for agriculture; Corteva is the agricultural successor entity; FMC and Loveland appear as registrants or distributors of formulated products in particular complaints.

Corporate succession will be contested. The Dow-DuPont combination and the subsequent separation into Dow, DuPont and Corteva produced a set of allocation agreements that defendants will use to argue about which entity bears liability for pre-separation conduct. Plaintiffs will plead successor liability and name the full chain. None of this is new — the Roundup litigation spent years on Monsanto and Bayer's corporate structure — but it adds months to the front end of every case and it matters for solvency analysis if this docket ever grows to a size that requires one.

Does Monsanto v. Durnell kill chlorpyrifos failure-to-warn claims?

Monsanto Co. v. Durnell does not end chlorpyrifos litigation, but it removes the warning claim from it. Decided 7-2 on 25 June 2026, with Justice Kavanaugh writing for the majority and Justice Jackson dissenting joined by Justice Gorsuch, Durnell holds that the Federal Insecticide, Fungicide, and Rodenticide Act expressly preempts a state-law Failure to Warn claim where the claim would require the registrant to carry a label different from, or additional to, what EPA approved. The case came from a Missouri farmer who used Roundup for about twenty years and argued the label should have carried a cancer warning; the Court held that state tort law could not impose that requirement while EPA's approved labeling said otherwise.

Chlorpyrifos is a FIFRA-registered pesticide with EPA-approved labeling. The logic transfers directly. A chlorpyrifos complaint pleading that the defendants should have added a Parkinson's warning to the Dursban or Lorsban label is pleading the claim the Supreme Court has just held preempted.

What Durnell did not do is equally important, and it is the part the consumer-facing coverage of this litigation has skipped entirely. The Court addressed a labeling-based warning claim. It did not hold that FIFRA preempts the field, and it did not address Design Defect, manufacturing defect, negligent testing, fraudulent concealment or warranty theories. Those remain available, subject to the individual facts and the law of the forum state — with the caveat that a defendant will argue any of them is a warning claim wearing a different hat, and some courts will agree.

Claim type	Status after Durnell	What it now turns on
Failure to warn premised on the EPA-approved label	Expressly preempted	Nothing survives if the claim requires different labeling
Design defect	Not addressed; available	Whether the state's test can be satisfied without asking for a label change; feasible alternative design
Negligent testing and failure to investigate	Not addressed; available	Duty to study long-term adult neurotoxicity independent of what the label said
Fraudulent concealment and misrepresentation	Not addressed; available	Off-label statements to regulators, customers and the scientific literature
Breach of warranty	Not addressed; available	Representations outside the approved labeling
Negligence per se on the label	Effectively foreclosed	Collapses into the preempted warning theory

The practical consequence is a drafting problem, not an extinction event. A chlorpyrifos Parkinson's lawsuit filed today has to be built so that its load-bearing counts do not depend on the label. That means pleading what the companies knew from their own toxicology, what they told EPA and what they did not, what they said in marketing and technical literature that never appeared on a registered label, and whether a less neurotoxic formulation was feasible. The evidentiary centre of gravity moves from the warning to the internal file.

Roundup is the live demonstration. In MDL No. 2741 before Judge Vince Chhabria in the Northern District of California, where roughly 3,925 actions were pending as of September 2026, Monsanto has moved to dismiss remaining cases on Durnell grounds, and the court has pushed back on both sides for briefing that did not engage precisely enough with what the decision actually reaches. A Missouri judge, meanwhile, declined to extend Durnell to design defect and negligence counts. That post-Durnell line-drawing exercise will be run again in every chlorpyrifos case, and the chlorpyrifos plaintiffs have the advantage of drafting after the decision rather than defending pleadings written before it.

Is chlorpyrifos still legal in the United States?

Yes. Chlorpyrifos tolerances are currently in effect for food uses, and this is the single most widely misunderstood fact about the litigation — several of the pages ranking for this subject leave readers believing the chemical was banned outright.

The chronology runs as follows.

Date	Action
2000	Dow agrees with EPA to phase out residential and indoor uses; retail sales end by the close of 2001
August 2021	EPA issues a final rule revoking all chlorpyrifos food tolerances, stopping use on food and animal feed
November 2023	The Eighth Circuit vacates the revocation rule
Following vacatur	All tolerances are reinstated and are currently in effect
November/December 2024	EPA proposes a rule that would revoke most food tolerances while retaining eleven uses in specified states
2026	EPA expected to issue an amended proposed interim decision for comment, followed by an interim decision

The eleven uses EPA proposed to retain are alfalfa, apple, asparagus, tart cherry, citrus, cotton, peach, soybean, strawberry, sugar beets and spring and winter wheat, limited to states assessed in the 2020 proposed interim decision. EPA's own estimate is that keeping only those uses would cut average annual pounds applied in the United States by around 70 per cent against historical usage.

For the litigation, current registration status is not a footnote. A defendant arguing preemption is in a materially stronger position when the product remains registered with EPA-approved labeling that says what it says. The reinstatement of tolerances after the Eighth Circuit's vacatur is therefore a defense asset, and plaintiffs will press the point that regulatory tolerance of a chemical is not a finding that it is safe — a distinction courts have accepted for decades but which juries hear differently.

There is a separate practical point about the residential claims. If indoor and residential uses ended at the close of 2001, then residential exposure claims are exposure claims from the last century, and every one of them arrives with a limitations question attached before the merits are reached.

Who can file a chlorpyrifos Parkinson's disease lawsuit?

The realistic claimant profile is someone with a Parkinson's disease diagnosis who personally mixed, loaded, applied or cleaned up chlorpyrifos products over a sustained period: farmers and farm workers, licensed pesticide applicators, pest control operators, grounds and golf course maintenance staff, greenhouse and nursery workers, and grain handlers. The UCLA data extend the picture to people who simply lived near treated fields for years, but a residential claim is a harder case to build because the exposure is diffuse and the Product Identification problem is acute.

The gating questions are the same three every time, and they are worth stating plainly because the intake pages ranking for this subject do not.

First, can the plaintiff identify the product? Not "a pesticide" and not "an organophosphate", but a named chlorpyrifos formulation traceable to a defendant. Purchase records, employer chemical inventories, applicator licence records, state pesticide use reports and coworker testimony are what carry this. A plaintiff who applied unlabeled product from a bulk tank for fifteen years has a causation story and no defendant.

Second, does the exposure have enough duration and intensity to support Specific Causation? The epidemiology is about long-term exposure. A season of incidental contact will not carry an expert opinion.

Third, is the claim timely? With diagnoses arriving decades after exposure, the Statute of Limitations and, in some jurisdictions, a statute of repose are the first things a defendant will raise. The Discovery Rule is the plaintiff's answer, and how it is applied varies by state. The 10-to-20-year latency finding in the UCLA work is useful here, because it goes to when a reasonable person could have connected exposure to disease at all.

A fourth question is quietly becoming important: how many other Parkinson's-linked exposures does the plaintiff have? Paraquat claims, well water contamination, other organophosphates and trichloroethylene exposure all compete for the same causal slot. A plaintiff already registered in the paraquat litigation is not disqualified from a chlorpyrifos claim, but the two claims will be used against each other, and counsel need to decide early which exposure the case is actually about.

Is there a chlorpyrifos MDL yet?

No. The Judicial Panel on Multidistrict Litigation has not opened a docket for chlorpyrifos, and the Panel's pending-MDL report dated 1 September 2026 lists none. Every chlorpyrifos Parkinson's lawsuit currently on file is proceeding individually, in state court or on removal.

An MDL petition under 28 U.S.C. § 1407 requires civil actions pending in more than one district that share common questions of fact, and it requires the Panel to be persuaded that centralisation will serve convenience and efficiency. On present numbers that case cannot be made. Ramos is in the Eastern District of Pennsylvania; the new Delaware filing is in state court and would only count if removed. A petition filed now would draw the response the Panel gives to thin dockets: that informal coordination between a handful of judges is adequate.

The comparison worth keeping in view is paraquat. In re Paraquat Products Liability Litigation, MDL No. 3004, before Chief Judge Nancy J. Rosenstengel in the Southern District of Illinois, held roughly 6,665 actions as of August 2026. That litigation approved a qualified settlement fund in March 2026, saw its first bellwether case settle in January 2026 on the eve of trial, and by June 2026 was dealing with a meaningful share of plaintiffs declining the offered terms. Paraquat is where chlorpyrifos wants to be and also a demonstration of how long it takes and how untidy the endgame is.

If the filing rate that produced one case in June and four in September continues, a petition becomes plausible during 2027. Practitioners should watch three leading indicators: the appearance of chlorpyrifos cases in three or more federal districts, the first defense motion invoking Durnell against a chlorpyrifos complaint, and whether any court entertains a Lone Pine Order early. That last one is the tell. A Lone Pine Order requiring product identification and exposure proof before general discovery would compress this docket faster than any ruling on preemption.

How much is a chlorpyrifos Parkinson's case worth?

There is no defensible answer, and anyone publishing a number is estimating. There has been no chlorpyrifos verdict, no Bellwether Trial, no Settlement Matrix, no Global Settlement and no MDL from which a matrix could emerge. Figures circulating in ranges of several hundred thousand dollars per claim are extrapolations from other pesticide litigation, not observations of this one.

What can be said with confidence is which variables will drive value once a market exists. Age at diagnosis, because a plaintiff diagnosed at 52 has a very different damages profile from one diagnosed at 78. Documented exposure duration and intensity, because that is what separates a trial case from an inventory case. Product identification quality. Wage loss and future care costs, which in advanced Parkinson's disease are substantial and well evidenced. And whether the internal corporate record supports a Punitive Damages claim, which in pesticide litigation has historically been the difference between a modest compensatory award and a headline number.

The honest framing for a client is that this litigation is at the stage paraquat occupied in 2019 and Roundup occupied in 2016: viable, scientifically supported, and years from a number.

What it means for plaintiffs' firms, defense counsel and funders

For plaintiffs' firms. The drafting has to change. A complaint modelled on a pre-Durnell pesticide template will lose its warning counts on a motion to dismiss, and if the warning counts were doing the work, the case goes with them. Build on design defect, negligent testing and concealment; plead conduct and representations that sit outside the EPA-approved label; and anticipate the argument that each surviving count is a repackaged warning claim. On intake, product identification should be a screening question, not a discovery problem — the cost of carrying unidentifiable cases through a Plaintiff Fact Sheet process is the single largest avoidable expense in an emerging tort. Firms building inventory should also be thinking now about a Census Registry mechanism and about how Common Benefit Fund assessments would be structured if an MDL is created later, because those terms are much harder to negotiate after leadership is appointed.

For defense counsel. Durnell is a substantial win and a narrow one. The preemption motion should be filed early and framed tightly on the labeling theory, because overreaching into design defect invites the kind of judicial impatience now visible in the Roundup MDL. The stronger long-run defenses here are not doctrinal: they are product identification, exposure quantification, alternative causation and limitations. The 2001 end of residential sales is a hard date that defines the outer boundary of a large category of claims. And the Daubert Challenge to general causation will be harder than it was in earlier pesticide torts, because the UCLA work pairs geocoded exposure data with an animal-model mechanism rather than relying on recall-based questionnaires.

For funders and portfolio buyers. This is early-stage risk with an unusually clear catalogue of contingencies: no MDL, no bellwether, no matrix, an unresolved preemption boundary, and a claimant population whose exposure largely ended between fifteen and thirty-five years ago. Third-Party Litigation Funding priced off paraquat or Roundup comparables will misprice it, because both of those dockets had resolved the preemption question one way or the other before capital arrived at scale. The variable to underwrite is not the science, which is comparatively strong; it is the proportion of acquired claims that will survive a product identification test.

For claimants. The practical consequence of everything above is that documentation is more valuable than speed. Employment records, applicator licences, purchase receipts, product labels kept in a shed, and the names of coworkers who can place a specific branded product in a specific place over a specific period are what convert a diagnosis into a claim.

Frequently asked questions

What is chlorpyrifos and what was it sold as?

Chlorpyrifos is an organophosphate insecticide that works by inhibiting acetylcholinesterase, an enzyme essential to nerve signalling. Dow brought it to market and sold it for residential and structural pest control as Dursban and for agricultural use as Lorsban; it has also been sold as Cobalt and in numerous other formulated products by multiple registrants.

Was chlorpyrifos banned in the United States?

Not entirely, and not currently for food uses. Residential and indoor uses were phased out under a 2000 agreement with EPA, with retail sales ending by the close of 2001. EPA revoked all food tolerances in August 2021, the Eighth Circuit vacated that rule in November 2023, and the tolerances were reinstated and remain in effect. EPA has proposed retaining eleven food uses and is expected to move that process forward during 2026.

Does the Supreme Court's Durnell decision end chlorpyrifos claims?

No. Monsanto Co. v. Durnell, decided 25 June 2026, holds that FIFRA preempts state-law failure-to-warn claims that would require labeling different from what EPA approved. It did not address design defect, negligent testing, fraud or warranty claims, and those theories remain available depending on the facts and the forum state's law.

Is there a chlorpyrifos class action or MDL?

Neither. These are individual personal injury claims, not a class action — personal injury claims of this kind are rarely certifiable because causation and damages differ for every claimant. No Judicial Panel on Multidistrict Litigation docket had been opened for chlorpyrifos as of the Panel's 1 September 2026 pending-MDL report.

How long do I have to file a chlorpyrifos Parkinson's lawsuit?

It depends on the state whose law applies and when the claim is treated as having accrued. Because Parkinson's disease is diagnosed decades after the relevant exposure, the discovery rule is usually central, and some states also impose a statute of repose that can bar a claim regardless of discovery. The limitations question should be assessed before anything else, because it is the first defense that will be raised.

Who are the defendants in the chlorpyrifos lawsuits filed so far?

Corteva Inc., Corteva Agriscience LLC and The Dow Chemical Company appear in both cases reported to date. FMC Corporation was named in Ramos v. Corteva, Inc.; Loveland Products Inc. was named in the 15 September 2026 Delaware Superior Court complaint. Which distributors appear in a given complaint depends on which branded product that plaintiff can identify.