Assurance report of the Statutory Auditor on a selection of social, environmental and other sustainable development information for the year ended 31 December 2017

Pursuant to your request and in our capacity of Statutory Auditor of Solvay SA / NV (“the Company”), we hereby present you our assurance report on a selection of social, environmental and other sustainable development information disclosed in the Solvay Group Annual Integrated Report for the year ended 31 December 2017 (the “2017 Annual Integrated Report”), identified by the symbol and .

Responsibility of the Company

This selection of information (the “Information”) extracted from the 2017 Annual Integrated Report has been prepared under the responsibility of Solvay Group management, in accordance with internal measurement and reporting principles used by Solvay Group (the "Reporting Framework"). The Reporting Framework consists of specific definitions and assumptions that are summarized in section “Extra-financial statements” of the 2017 Annual Integrated Report.

Responsibility of the Statutory Auditor

It is our responsibility, based on the procedures performed by us, to express:

• “Limited assurance” for the Information identified by the symbol as included in the 2017 Annual Integrated Report
• “Reasonable assurance” for the Information identified by the symbol as included in the 2017 Annual Integrated Report

The complete list of Information in scope of our assurance engagement together with the type of assurance has been included in appendix A of this report.

We conducted our procedures in accordance with the international standard as defined in ISAE (International Standard on Assurance Engagements) 3000 (Revised)¹ISAE 3000 (Revised) - Assurance engagements other than audits or reviews of historical information. With respect to independence rules, these are defined by the respective legal and regulatory texts as well as by the professional Code of Ethics, issued by the International Federation of Accountants (“IFAC”).

Nature and scope of procedures

We have carried out the following procedures

• General procedures:
  • We assessed the appropriateness of the Reporting Framework with respect to its relevance, completeness, neutrality, clarity and reliability, by taking into consideration, when relevant, the sector reporting practices.
  • We have verified the set-up within Solvay Group of the process to obtain, consolidate and check the selected Information with regard to its completeness and consistency. We have familiarized ourselves with the internal control and risk management procedures relating to the compilation of the information. We have conducted interviews with individuals responsible for social, environmental and other sustainable development reporting.
  • At the sites that we have selected based on their activity, their contribution to consolidated indicators, their location and a risk analysis, we have:
    • Conducted interviews to verify the proper application of procedures and obtained information to perform our verifications;
    • Conducted substantive tests, using sampling techniques, to verify the calculations performed and reconcile data with supporting evidence.
  • All the audited sites and perimeters are listed in appendix B of this document.
• “Limited assurance” for the Information identified by the symbol as included in the 2017 Annual Integrated Report
  • For the entity in charge of consolidation (“the Company”), as well as for the controlled entities, we have designed analytical procedures and verified, using sampling techniques, the calculations as well as the consolidation of this information in order to obtain limited assurance that the selected information does not contain any material errors that would question its preparation, in all material respects, in accordance with the Reporting Framework. A higher level of assurance would have required more extensive procedures.
• “Reasonable assurance” for the Information identified by the symbol as included in the 2017 Annual Integrated Report
  • We conducted work of the same nature as the work described in section above (limited assurance) but in further detail, in particular performing an increased number of tests. When relevant, we have tested a representative sample of entities based on their activities, their contribution to the consolidated data, their location and a risk analysis. In these cases, the selected sample represents between 46 % and 52% of the published data, which is significantly more than what would be requested for a limited assurance review.

Conclusion

• For the indicators in scope of “limited assurance” (identified by the symbol )

On the basis of the procedures performed by us, nothing came to our attention that causes us to believe that the Information identified by the symbol as included in the 2017 Annual Integrated Report, is not prepared, in all material respects, in accordance with the Reporting Framework.

• For the indicators in scope of “reasonable assurance” (identified by the symbol )

In our opinion, based on the procedures performed, the Information identified by the symbol as included in the 2017 Annual Integrated Report, has been prepared in all material respects in accordance with the Reporting Framework.

Observation

Without qualifying our conclusion above, we draw your attention to the following point: worked hours is used as the denominator of the indicators MTAR (Medical Treatment Accident Rate), LTAR (Lost Time accident Rate) and Process Safety Incident Rate. We observed that different methodologies are applied by the sites for calculating worked hours (employees and contractors).

Zaventem, 29 March 2018
The statutory auditor

DELOITTE Bedrijfsrevisoren / Réviseurs d’Entreprises
BV o.v.v.e. CVBA / SC s.f.d. SCRL
Represented by Michel Denayer

Appendix A - Overview of indicators reviewed

Indicators in bold are selected for reasonable insurance.

Appendix B - Overview of perimeter reviewed