FORM 52 – 109F2
CERTIFICATION OF INTERIM FILINGS
I, Douglas Newby, Chief Financial Officer of PolyMet Mining Corp., certify that:
1. Review: I have reviewed the interim financial statements and interim MD & A, (together, the “interim
filings”) of PolyMet Mining Corp. (the issuer) for the interim period ended July 31, 2010.
2. No Misrepresentations: Based on my knowledge, having exercised all reasonable diligence, the interim
filings do not contain any untrue statement of a material fact or omit to state a material fact required to be
stated or that is necessary to make a statement not misleading in light of the circumstances under which it
was made, with respect to the period covered by the interim filings.
3. Fair presentation: Based on my knowledge, having exercised all reasonable diligence, the interim financial
statements together with the other financial information included in the interim filings fairly present in all
material respects the financial condition, results of operations and cash flows of the issuer, as of the date of
and for the periods presented in the interim filings.
4. Responsibility: The issuer’s other certifying officer and I are responsible for establishing and maintaining
disclosure controls and procedures (DC&P) and internal controls over financial reporting (ICFR), as those
terms are defined in National Instrument 52-109 Certification of Disclosure in Issuers’ Annual and
Interim Filings , for the issuer.
5. Design: Subject to the limitations, if any, described in paragraphs 5.2 and 5.3, the issuer’s other certifying
officer and I have, as at the end of the period covered by the interim filings:
(a) designed DC&P, or caused it to be designed under our supervision, to provide reasonable assurance
(i) material information relating to the issuer, is made known to us by others, particularly during the
period in which the interim filings are being prepared, and