Lyondell Chemical Co. (Houston) has obtained European Commission antitrust clearance for the company's acquisition of Millennium Chemicals Inc. for $1 billion in stock, according to news reports in Europe. Lyondell says completion of the acquisition is anticipated in the third quarter. The merger will combine two large U.S. chemical companies that hold major positions in various commodity and specialty chemicals, including titanium dioxide, propylene oxide, acetyls, vinyl acetate monomer, cadmium pigments and other materials.