NOTE 13—COMMITMENTS AND CONTINGENCIES

Environmental Matters

Accruals for environmental matters are recorded when it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated, based on current law, existing technologies and other information. Pursuant to the terms of the Dow Separation, the pre-closing environmental conditions were retained by Dow, and the Company has been indemnified by Dow from and against all environmental liabilities incurred or relating to the predecessor periods. There are several properties which the Company now owns on which Dow has been conducting investigation, monitoring, or remediation to address historical contamination, including Dalton, Georgia. There are other

properties with historical contamination that are owned by Dow that the Company leases for its operations, including its facilities in Midland, Michigan, Schkopau, Germany, and Terneuzen, The Netherlands. Other than certain immaterial environmental liabilities assumed as part of the PMMA Acquisition and the Aristech Surfaces Acquisition, no material environmental claims have been asserted or threatened against the Company. The Company is not a potentially responsible party for any material amounts at any Superfund sites. As of June 30, 2026 and December 31, 2025, the Company had $2.0 million, respectively, of accrued obligations for environmental remediation or restoration costs.

Inherent uncertainties exist in the Company’s potential environmental liabilities primarily due to unknown conditions, whether future claims may fall outside the scope of the indemnity, changing governmental regulations and legal standards regarding liability, and evolving technologies for handling site remediation and restoration. In connection with the Company’s existing indemnification, the possibility is considered remote that environmental remediation costs will have a material adverse impact on the condensed consolidated financial statements over the next 12 months.

Asset Retirement Obligations

The Company has built certain manufacturing facilities on leased land and is required to remove these facilities at the end of the corresponding contract term. Legal obligations for these demolition and decommissioning activities exist in connection with the retirement of these assets triggered upon closure of the facilities. In instances when the Company plans to continue operations at these facilities indefinitely, and therefore, a reasonable estimate of fair value cannot be determined, an asset retirement obligation is not recognized.

In connection with the asset restructuring plans, as described within Note 4, the Company concluded the Boehlen, Germany site, the Stade, Germany site, the Schkopau, Germany site and the Porto Marghera, Italy site no longer had indeterminate lives. Accordingly, the Company recorded the fair value of an asset retirement obligation for each site and a corresponding asset retirement cost, which was capitalized as part of the carrying amount of the related long-lived assets and depreciated over the asset’s shortened useful life.

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Accretion expense is included within “Selling, general and administrative expenses” in the condensed consolidated statement of operations. The current portion of the asset retirement obligation is recorded within “Accrued expenses and other current liabilities” and the long-term portion is recorded within “Other noncurrent obligations” in the condensed consolidated balance sheets. As of June 30, 2026 and December 31, 2025, the current portion was $15.1 million and $17.1 million, respectively, and the long-term portion was $11.2 million and $20.7 million, respectively.

Purchase Commitments

In the normal course of business, the Company has certain raw material purchase contracts where it is required to purchase certain minimum volumes at current market prices. These commitments range from one to four years. In certain raw material purchase contracts, the Company has the right to purchase less than the required minimums and pay a liquidated damages fee, or, in case of a permanent plant shutdown, to terminate the contracts. In such cases, these obligations would be less than the annual commitment as disclosed in the Notes to Consolidated Financial Statements included in the Annual Report.

Litigation Matters

From time to time, the Company may be subject to various legal claims and proceedings incidental to the normal conduct of business, relating to such matters as employees, product liability, antitrust/competition, past waste disposal practices and release of chemicals into the environment. While it is impossible at this time to determine with certainty the ultimate outcome of these routine claims, the Company does not believe that the ultimate resolution of these claims

will have a material adverse effect on the Company’s results of operations, financial condition or cash flow. Legal costs, including those legal costs expected to be incurred in connection with a loss contingency, are expensed as incurred.

Environmental Proceedings related to the Bristol Spill

On March 25, 2023, the Company received a Notice of Federal Interest from the United States Coast Guard (“USCG”), identifying the Company as a “potentially responsible party” (“PRP”) related to the Bristol Spill. The Company also received a Notice of Federal Assumption and an Administrative Order, dated April 20, 2023 from the USCG, identifying the Company as a PRP related to the Bristol Spill. The USCG notices and order do not designate specific fines or penalties against the Company. In October 2023, the Pennsylvania Department of Environmental Protection (PADEP) notified the Company of its intent to impose penalties related to a Notice of Violation dated April 26, 2023 alleging water violations associated with the Spill. Discussions between the Company and PADEP are ongoing. In December 2023, the Company established an accrual for the estimated resolution of this matter, and such loss is not expected to be material to our business.

It is not possible at this time for the Company to estimate its ultimate liability pursuant to these matters or other potential administrative or criminal actions related to the Bristol Spill, whether a material loss to our business is probable or remote, or estimate a potential range of loss, if any.

Synthos Matter

On November 21, 2022, the Company received formal notice from the German Arbitration Institute that Synthos had initiated an arbitration dispute on October 14, 2022 against Trinseo and its following subsidiaries: Trinseo Deutschland GmbH, Trinseo Belgium BV, Trinseo Europe GmbH, and Trinseo Export GmbH, related to Synthos’ purchase of Trinseo’s Rubber Business in 2021.

Synthos and Trinseo are parties to an asset purchase agreement (“APA”) dated May 21, 2021, whereby Trinseo transferred its Rubber Business to Synthos, pending regulatory approval and other administrative pre-closing conditions, for an enterprise value of approximately $491.0 million. This transaction formally closed on December 1, 2021. Synthos claims that Trinseo did not properly disclose certain information including the natural gas pricing mechanism for the steam which is supplied by a third party to the Rubber Business. Synthos is seeking monetary damages related to the spike of utility prices in Germany that commenced in the fall of 2021. On December 7, 2023, Synthos filed an adjusted motion with the German Arbitration Institute clarifying its claims for monetary damages. On April 26, 2024, Trinseo filed a statement of defense and counterclaim in response to Synthos’ adjusted motion. On September 27, 2024, Synthos filed a Statement of Reply to reduce its monetary damages claim and filed a statement of defense to Trinseo’s counterclaim. On February 10, 2025, Trinseo filed a statement of rejoinder in defense of Synthos’ claims and a reply to Synthos’ statement of defense of Trinseo’s counterclaim. On March 21, 2025, Synthos filed a further statement of defense against Trinseo’s counterclaim. During the week of May 19, 2025, an arbitration hearing was held before an arbitration tribunal convened by the German Arbitration Institute, following which the tribunal set a schedule for submission of post-hearing briefings ending during the fourth quarter 2025. The parties submitted respective final substantive briefs to the arbitration tribunal over July, August and September 2025. Additional briefs related to potential reimbursement of legal fees and other costs incurred were submitted in fourth quarter 2025. On May 7, 2026, the German Arbitration Institute notified the parties of the arbitration tribunal’s final decision which ruled in favor of Trinseo by dismissing all of Synthos’ claims. Although this decision also dismissed Trinseo’s counterclaim, Trinseo was awarded its costs for the arbitration. Additionally, in July 2026, Trinseo and Synthos entered into a separate asset purchase agreement, for equipment unrelated to the arbitration, that includes a waiver by Synthos of its right to seek court review of the arbitration tribunal’s final decision.

Chapter 11 Litigation

On May 29, 2026, an ad-hoc minority lender group filed an adversary complaint pursuant to Rule 7001 of the Federal Rules of Bankruptcy Procedure with regard to the Chapter 11 Cases against certain lenders and certain of the Debtors, alleging that the Company’s 2023 refinancing transactions violated the terms of the Credit Agreement and therefore subsequent transactions should be invalidated, including seeking disallowance of certain intercompany loans, as well as recharacterization or subordination of those same intercompany loans, and subordination of the OpCo Super-Priority Revolver. The Company filed a Motion for Judgment on the Pleadings on June 9, 2026, with the parties subsequently filing response and reply briefs on June 23 and June 30. Additionally, the complaint was amended on June

23, 2026, and the Company filed an answer to the amended complaint, on July 7, 2026. The Bankruptcy Court heard argument on the Motion for Judgment on the Pleadings on July 22, 2026. On July 30, 2026, the Bankruptcy Court issued an oral ruling denying the Company’s Motion for Judgment on the Pleadings with respect to three claims, dismissing a fourth claim with leave to amend, and denying the Company’s request to stay the minority lender group’s objection to certain intercompany claims. The matter is currently scheduled for trial on August 12-14, 2026.

In addition, the ad-hoc minority lender group has filed certain additional motions that could affect the resolution of these Chapter 11 Cases, including (a) a motion to designate the votes of certain intercompany loans, (b) a motion seeking leave of the Bankruptcy Court for derivative standing to assert certain claims, including fraudulent conveyance and breach of fiduciary duty claims, on behalf of the Company and certain of its subsidiaries, and (c) a motion seeking to terminate the Company’s exclusive authority to promulgate a plan of reorganization. Responses to the first two motions are due on August 7, 2026, and each motion is expected to be heard during the scheduled August 12-14 trial. A response to the latter motion is currently due on August 11, 2026.