August 5, 2019

Minnesota Court of Appeals upholds nonferrous mining rules for PolyMet NorthMet Project

St. Paul, Minn. August 5, 2019 – Poly Met Mining, Inc., a wholly-owned subsidiary of PolyMet Mining Corp. (together “PolyMet” or the “company”) TSX: POM; NYSE American: PLM, announces that the Minnesota State Court of Appeals today affirmed the validity of the state’s nonferrous mining rules, rejecting a challenge from environmental groups who sought to overturn the rules after the state issued PolyMet’s Permit to Mine.

In its unanimous decision, the three-judge panel recounted the history of the Department of Natural Resources’ nonferrous mining rules, emphasizing the decade of “study and rulemaking proceedings” that led to their adoption. The court agreed with the DNR that “flexible reclamation rules are necessary to accommodate the variety of conditions at proposed mine sites” and endorsed the DNR’s authority to establish reclamation standards and “deny a
permit . . . if reclamation standards cannot be met.”

This case was filed in 2018 against the DNR by the Minnesota Center for Environmental Advocacy and Friends of the Boundary Waters Wilderness. PolyMet intervened as a corespondent to defend the rules.

“We are pleased that the Court of Appeals ruled in our favor,” said Jon Cherry, president and CEO. “Minnesota’s standards for nonferrous mining are among the strictest anywhere in the world, and we demonstrated through the extensive environmental review and permitting process that we can meet or exceed these standards.”

PolyMet is the first company to be fully permitted to mine copper, nickel and precious metals from the world-class Duluth Complex under the state’s nonferrous rules.

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About PolyMet
PolyMet Mining Corp. (www.polymetmining.com) is a publicly traded mine development
company that owns 100 percent of Poly Met Mining, Inc., a Minnesota corporation that
controls 100 percent of the NorthMet copper-nickel-precious metals ore body through a longterm
lease, and owns 100 percent of the former LTV Steel Mining Company processing facility,
located approximately seven rail miles from the ore body in the established mining district of
the Mesabi Iron Range in northeastern Minnesota. Poly Met Mining, Inc. has completed its Definitive Feasibility Study and received all permits necessary to construct and operate the NorthMet Project. NorthMet is expected to require approximately two million hours of construction labor, create approximately 360 long-term jobs directly, and generate a level of activity that will have a significant multiplier effect in the local economy.

For further information, please contact:

Media
Bruce Richardson, Corporate Communications
Tel: +1 (651) 389-4111
brichardson@polymetmining.com

Investor Relations
Tony Gikas, Investor Relations
Tel: +1 (651) 389-4110
investorrelations@polymetmining.com

PolyMet Disclosures
This news release contains certain forward-looking statements concerning anticipated developments in PolyMet’s
operations in the future. Forward-looking statements are frequently, but not always, identified by words such as
“expects,” “anticipates,” “believes,” “intends,” “estimates,” “potential,” “possible,” “projects,” “plans,” and similar
expressions, or statements that events, conditions or results “will,” “may,” “could,” or “should” occur or be achieved
or their negatives or other comparable words. These forward-looking statements may include statements  regarding the ability to receive environmental and operating permits, job creation, and the effect on the local economy, or other statements that are not a statement of fact. Forward-looking statements address future events and conditions and therefore involve inherent known and unknown risks and uncertainties. Actual results may differ materially from those in the forward-looking statements due to risks facing PolyMet or due to actual facts differing from the assumptions underlying its predictions.

PolyMet’s forward-looking statements are based on the beliefs, expectations and opinions of management on the
date the statements are made, and PolyMet does not assume any obligation to update forward-looking statements if circumstances or management’s beliefs, expectations and opinions should change.

Specific reference is made to risk factors and other considerations underlying forward-looking statements discussed in PolyMet’s most recent Annual Report on Form 40-F for the fiscal year ended December 31, 2018, and in our other filings with Canadian securities authorities and the U.S. Securities and Exchange Commission.

The Annual Report on Form 40-F also contains the company’s mineral resource and other data as required under National Instrument 43-101.

The TSX has not reviewed and does not accept responsibility for the adequacy or accuracy of this release.