"The pollution estimate in question was too high - by 340 percent, according to the California Air Resources Board, the state agency charged with researching and adopting air quality standards. The estimate was a key part in the creation of a regulation adopted by the Air Resources Board in 2007, a rule that forces businesses to cut diesel emissions by replacing or making costly upgrades to heavy-duty, diesel-fueled off-road vehicles used in construction and other industries. "

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2010/10/08/MNOF1FDMRV.DTL#ixzz11o1B3ywU

"The revision was ordered after the board scientist who oversaw that study was outed as having faked his scientific credentials.
Roberts and other board members were not told by Nichols that the scientist, Hien Tran, lied about earning a doctorate from UC Davis before they voted in favor of regulations based in part on his science. That vote took place in December 2008.
Nichols, who acknowledges she knew about the falsification prior to the vote, has apologized for not sharing that information with her fellow board members."

And she is still head of CARB. She should be dismissed immediately. People have spent thousands of dollars and some have gone out of business already because of her negligent practices. Also, there excuse for the overestimate was caused by the recession is baseless because their factors were used before the recession started.

If you are voting in Calif. you might want to think seriously about Prop. 23.
Makes me wonder about the EPA too.