Lyondell Chemical Company Non-employee Directors Benefit Plans Trust Agreement

Exhibit 10.16

INSTRUMENT AMENDING

LYONDELL CHEMICAL COMPANY

NON-EMPLOYEE DIRECTORS BENEFIT PLANS

TRUST AGREEMENT Lyondell Chemical Company hereby amends, effective February 23, 2006, the Lyondell Chemical Company Non-Employee Directors Benefit Plans Trust Agreement, as follows:

Section 3, Change in Control, Section 3.2., " Definition of Change in Control" is revised in its entirety to read as follows:

Section 3.2. Definition of " Change in Control" . For purposes of this Trust Agreement, a " Change in Control" shall be deemed to occur on the date that one or more of the following occurs:

(i) Individuals who constitute the entire Board on the date of this amendment (" Incumbent Directors" ) then cease to constitute at least a Board majority for any reason; provided , however , that any individual after the date of this amendment also shall be considered an Incumbent Director if the individual' s election or nomination for election by the Company' s shareholders was approved by a vote of at least a majority of the then Incumbent Directors, but an individual shall not be considered an Incumbent Director if the individual' s initial assumption of office occurs as a result of either an actual or threatened election contest, as those terms are used in Rule 14a-11 under the Securities Exchange Act of 1934, as amended, or as a result of other actual or threatened solicitation of proxies or consents by or on behalf of any Person (as defined below) other than the Board;

(ii) The consummation of any merger, consolidation, amalgamation, reorganization, share exchange or recapitalization of the Company (or, if the Company' s capital stock is affected, any Company subsidiary), or any sale, lease, exchange or other transfer (in one transaction of a series of transactions contemplated or arranged by any party as a single plan) of all or substantially all of the Company' s assets (each of the foregoing being an " Acquisition Transaction" ) where:

(1) the Company' s shareholders immediately before that Acquisition Transaction do not beneficially own, directly or indirectly, immediately after that Acquisition Transaction shares or other ownership interests representing in the aggregate fifty percent (50%) or more of (a) the then outstanding common stock or other equity interests of the corporation or other entity surviving or resulting from the merger, consolidation, amalgamation, reorganization, share exchange or recapitalization or

acquiring such assets of the Company, a ...