They have been joined by the city of Chicago, which has agreed to the same emissions limits and, like the others, will be able to trade credits earned by exceeding those limits when trading starts in about 90 days.
CCX is the first effort by U.S. companies to voluntarily commit to reducing the pollutants they emit and aims to establish a market for trading such emissions.
The National Association of Securities Dealers, a Washington, D.C.-based self-regulatory body for the securities industry, has been selected to oversee compliance with the targets. Any failures will be handled by peer review.
In mid-January, legislation was introduced by U.S. Senators John McCain (R-Ariz.) and Joseph Lieberman (D-Conn.) calling for a U.S. system to cap emissions and a market for trading them.