U.S. Senate Passes Land Exchange between PolyMet, U.S. Forest Service

The U.S. Senate today passed bipartisan legislation for a land exchange
between the Forest Service and Poly Met Mining, Inc., a wholly-owned
subsidiary of PolyMet Mining Corp. (together “PolyMet” or the “company”)
TSX: POM; NYSE AMERICAN: PLM. Passage of the legislation marks another
major milestone in PolyMet’s development of Minnesota’s first
copper-nickel-precious metals mine, located near Hoyt Lakes.

The land exchange measure was included as an amendment to the National
Defense Authorization Act, which passed on a 85-10 vote in the Senate.
Last November the House of Representatives passed the land exchange bill
on an overwhelming, bipartisan 309-99 vote.

The Senate amendment was sponsored by Sen. Tina Smith and co-sponsored
by fellow Minnesota Sen. Amy Klobuchar. It is nearly identical to the
bill authored by Rep. Rick Nolan (D-Minn.), The Superior National Forest
Land Exchange Act of 2017, which he introduced in the House last summer
and shepherded to passage. His bipartisan bill was co-sponsored by
fellow Minnesota Democrat Reps. Collin Peterson and Tim Walz, and
Republicans Tom Emmer and Jason Lewis, among others.

In January 2017, the Superior National Forest issued a Record of
Decision authorizing the administrative land exchange, determining it
was in the best public interest.

“We are very grateful to House and Senate members and leadership who
have worked tirelessly to bring this land exchange to closure,” said Jon
Cherry, president and CEO. “We also acknowledge with gratitude the
strong hand of support shown to this legislation by business and labor
groups, community leaders, and local supporters.”

The transfer of approximately 6,650 acres of federal lands to PolyMet
consolidates surface land and mineral ownership in and around the
NorthMet ore body, near an area historically used for mining and
associated infrastructure. Likewise, PolyMet’s transfer of title of four
tracts of private land to the Forest Service totaling 6,690 acres
further consolidates its land holdings in northeast Minnesota.

With title transfer, PolyMet will have total surface ownership rights of
approximately 19,000 contiguous acres (30 square miles) of land
including the land at the mine and processing sites, the transportation
corridor connecting those sites, and buffer.

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
long-term lease, and owns 100 percent of the Erie Plant, a large
processing facility located approximately six 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. The NorthMet Final Environmental Impact Statement was
published in November 2015, preparing the way for decisions on permit
applications. 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.

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,
2017, 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.

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